# Centrifugal vs axial compressors in WW2 jets



## wuzak (Dec 22, 2013)

On another thread davparlr remarkd:



davparlr said:


> And I think putting all their eggs into the axial flow design was a mistake. I believe that if they had pressed the much simpler centrifugal flow design that they could have had a single 4-5000 lb thrust engine, straight wing fighter fielded in late ’43, in time to affect the air war over Germany. Possibly, such engine installed into a P1101 type fighter could have been in production by early ’45, pre-dating the F-86/Mig 15 by 2 years.




SR6 followed that up with the following:



Shortround6 said:


> The Axial flow design was NOT easier to get into service quickly, the British had a least one if not more axial programs and the US and 2 or 3 programs, even allocating them to engineering firms with extensive steam turbine experience resulted in spotty results. In part because the US imposed some rather restrictive secrecy rules which prevented companies from talking to each other (although a few of them could talk to a "parent/partner" company in England) which meant a lot of the same problems had to solved a number of times independently.
> The Axial compressor ( the rest of the "stuff" ie, combustion chambers and power turbines are pretty much interchangeable between the two types) was very hard to sort out. The early axial flow compressors (everybody's) were heavy, complex, and had lower compression ratios and efficiency than the centrifugal compressor. By the late 40s and very early 50s this had flipped and new axial compressors were showing much better performance than the centrifugals but that is several years too late.





Firstly, the Germans first flying jet engines used centrifugal compressors. And they used radial inflow turbines. These were the Heinkel-Hirth HeS 3. This was replaced by the HeS 6, which worked but was deemed to be too heavy and was cancelled. The next development was the HeS 8 (109-001), which was delayed by problems and didn't produce the expected thrust. It was cancelled in favour of axial flow projects that Heinkel had also been working on.

So, there was some effort in Germany towards making a centrifugal flow jet engine. These did not have the performance of the contemporary BMW and Jumo engines. Not sure that they were any more reliable, either.

Partly on the RLM's instructions, Heinkel's class II jet engine featured a "diagonal" compressor - a cross between an axial and centrifugal compressor, which did not work as well as either.

I have serious doubts as to whether Germany could have produced a 4000-5000lb static thrust jet using a centrifugal compressor, certainly before the Me 262 became operational.

Back to the British.
The RAE and AA Griffiths had been running test axial flow compressors since the mid 1930s. This was work towards their first complete engine, a turbo-prop, which was to be made by Metropolitan Vickers. When Whittle demonstrated his jet, the decision at MV was to drop the turbo-prop in favour of a new jet. The was the F.2.

The F.2 did have reliability problems - these appear to be mainly in the combustion chamber, which caused hot spots in the turbine and turbine failure. The solution was to use several smaller combustion chambers like those used in the centrifugal types. This change was made in 1943, resulting in even more thrust.

The F.2 gave more thrust than the contemporary Welland or (early mk) Derwent, was somewhat heavier but also more fuel efficient.

One wonders if the reliability issues that the F.2 was experiencing would have been overlooked if Britain had been in a similar position to Germany in 1943/44?

Another British axial flow egine was the Armstrong-Siddeley ASX. This didn't run until sometime in 1945, and was abandoned in favour of the Metrovicks F.9 Sapphire.

In the US the only axial jet project I am aware of is the Lockheed L-1000 project.


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## Shortround6 (Dec 22, 2013)

Two American programs were the Westinghouse program and the General Electric program. Northrop also was working on an axial design. 

During the war years the Army and Navy had contracted for the development of seven turbo-props, five turbo jets, three pulse jets. There were also several ramjet design studies. 

The Westinghouse 19A is claimed to be the 2nd Axial jet engine to run outside of Germany on March 19th 1943. This lead to the 19XB (J30) under flight test Sept 28th 1944 ( Under/In a Martin Marauder), the 9.5 or J32 first run in June 1944 and the larger J34 first run in April 1945 and in early models could reach 3000lbs thrust.

GE had been contracted to build a turbo-prop, design work started July 25th 1941 on the TG-100 with a 14 stage axial compressor. First test run Dec 23rd 1943. Much of what was learned was used on the TG-180 (J-35) which was first run on April 21 1944 although it doesn't make it to flight test until May of 1946.


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## fastmongrel (Dec 22, 2013)

wuzak said:


> And they used radial inflow turbines.
> 
> a "diagonal" compressor - a cross between an axial and centrifugal compressor, which did not work as well as either.
> 
> .



Never heard of these 2 types of jet engine have you got anymore details wuzak


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## wuzak (Dec 22, 2013)

fastmongrel said:


> Never heard of these 2 types of jet engine have you got anymore details wuzak



The radial in-flow turbine is the type of turbine used on modern turbochargers. The GE turbos used axial turbines, as did most of the jets of WW2.

Basically the radial in-flow turbine works like the centrifugal compressor, but the opposite way.

A schematic of the Heinkel-Hirth system






A picture of the HeS 3 trubine and exhaust







The diagonal flow compressor has the air flow moving diagonally along its length. A centrifugal compressor turns the air 90° to its axis, while the axial compressor has air that flows parallel to the axis (for each stage). The diagonal compressor is somewhere in between.


Item 2 in this diagram is the diagonal compressor.
http://img441.imageshack.us/img441/2386/109011a0.jpg

In these two pictures it is the set of blades ahead of the 3 stage axial compressor.
http://upload.wikimedia.org/wikipedia/commons/8/8d/Heinkel-Hirth_HE_S_011_USAF.jpg
http://img185.imageshack.us/img185/5249/heinkelhirthhes001view7.jpg

The diagonal compressor was used on the HeS 011.


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## delcyros (Dec 22, 2013)

Shortround6 said:


> The Westinghouse 19A is claimed to be the 2nd Axial jet engine to run outside of Germany on March 19th 1943. This lead to the 19XB (J30) under flight test Sept 28th 1944 ( Under/In a Martin Marauder), the 9.5 or J32 first run in June 1944 and the larger J34 first run in April 1945 and in early models could reach 3000lbs thrust.



Would You mind to shed more light on this SR?
I have read conflicting data to that in that the J30 -which run earlier- was certified in the first series production version J-30 WE-20 for 150 hour benchtests not earlier than sept. 1945 (on a static thrust rating of 1,550lbs and rev limited to 17,000rpm) and that in april 1945, the J34 was projected, but the first engine wasn´t completed before 1946 and was first trialed on an airplane in 1947.

There were a couple of challanges to be overcome with axial jet engines:

[+] compressor stall caused by rotors
[+] compressor stall caused by air duct and boundary layer seperation 
[+] burn out of turbine blades (requiring an accelerator valve of the fuel gouvernor)
[+] exhoust nozzle needle controll for optimum performance in a given range of altitudes / engine speed
[+] technical reliability
[+] ability to relight in flight (Seems trivial but THIS WAS A BIG CONCERN. -the primary reason to give early jet A/C so large wing areas and good low speed handling -that if engine was lost during take off/landing it doesn´t critically effect the survivability of the pilot)

the first jet engine which adressed most of these points -to my knowledge- was the BMW-003A1. The BMW- jet engine project took longer than Junkers -004 but it was a more matured design. Lighter and smaller, better thrust-weight ratio, 150 hours certified lifetime for the hot turbine section (the compressor section had a significantly larger lifetime), an accelerator valve to prevent the burn out of the turbine blade due to rapid throttle changes (AFAIK, this was the first jet engine, whiches throttles could be less gingerly advanced and returned without fear of damaging the engine), good altitude performance with very few documented compressor stalls (could be relighted in flight) and overrew capability for increased thrust. There was one aspect which was not included, an automatic exhoust jet needle controll such as employed by Junkers, requiring the operator to controll this aspect.


Radial compressor jet engines like those mentioned previously were probably better suited for the low thrust ratings concerned in ww2 but required more machining, milling and higher grade steel ressources.

The requirement to produce only jet engines with spare free charakteristics would preclude the idea that the Luftwaffe could have fielded a working 4000 to 5000lbs jet engine in time for ww2, be it radial or axial design. As I mentioned previously, this requirement set back the whole jet engine project by approx. 1.5 years. Many of the issues encountered historically really just need to be adressed in order to be able to move beyond this low thrust rating to higher performance engines.

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## wuzak (Dec 22, 2013)

delcyros said:


> There were a couple of challanges to be overcome with axial jet engines:
> 
> [+] compressor stall caused by rotors
> [+] compressor stall caused by air duct and boundary layer seperation



These seem, to me, to be the only points that apply to axial jets only, though I'm not sure that the second one is unique to axial jets either.


Whereas the following seem to be general gas turbine concerns.



> [+] burn out of turbine blades (requiring an accelerator valve of the fuel gouvernor)
> [+] exhoust nozzle needle controll for optimum performance in a given range of altitudes / engine speed
> [+] technical reliability
> [+] ability to relight in flight (Seems trivial but THIS WAS A BIG CONCERN. -the primary reason to give early jet A/C so large wing areas and good low speed handling -that if engine was lost during take off/landing it doesn´t critically effect the survivability of the pilot)



Axial flow compressors were being tested in the UK, Germany and, probably, the US before the war. They could, and did, run compressors without the combustors and turbines to test them. So while they weren't building gas turbines they were ironing out the compressor problems and improving them.


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## wiking85 (Dec 22, 2013)

How much and what kinds of raw materials would the Germans have needed to make their without restrictions on materials? I've read that the V-2 rocket nozzles consumed major heat resistant metals that would have been used with the jet engines like nickel, so had the V-2 project not been followed through on, then the jet program wouldn't have had to restrict itself and would have been further along. Is there any truth to that?


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## Shortround6 (Dec 22, 2013)

delcyros said:


> Would You mind to shed more light on this SR?
> I have read conflicting data to that in that the J30 -which run earlier- was certified in the first series production version J-30 WE-20 for 150 hour benchtests not earlier than sept. 1945 (on a static thrust rating of 1,550lbs and rev limited to 17,000rpm) and that in april 1945, the J34 was projected, but the first engine wasn´t completed before 1946 and was first trialed on an airplane in 1947.




I am not sure how much more light you want. First ground "test" or first run is not type test or certification test. 

The Westinghouse 19A used a different compressor than the 19B ( 6 stages instead of 10 and there were more than likely other changes as well, both combustion chambers and turbine section design did not stay static during the development period.) Apparently only 6 of 19A engines were built. A 19A was test flown under neath a Corsair for the first time Jan 21 1944. The 6 stage compressor offered NO advantage over a centrifugal compressor however (pressure ratio and thus fuel consumption being no better than centrifugal engines under development at the same time. The 19A had been intended as a "booster" engine. 
A contract for 500 19XB engines had been placed in Jan of 1944 (essentially off the drawing board) and while the J-30 WE-20may or may not have been certified for 150 hours in Sept of 1945 the XFD-1 Phantom Prototype first flew with two J30s in Jan of 1945. There were a number of problems with the engine even several years later that kept the Phantom from reaching the hoped for performance. Contract was cut to 190 engines right after V-J day. Many American programs were cut, slashed, dropped and then re-instated and cut again during late 1945 and 1946/47. Research, development and deployment was nowhere near the wartime pace until the cold war really got going in 1948. 
Most sources say the Vought XF6U-1 first flew Oct 2 1946 with a J34 engine. Granted that is only a few months from 1947. The J-34 may have taken a while to fully develop but wound up being a fairly reliable and long lived, or long used engine ( many jets gave a LOT trouble in their first few years) being manufactured until 1962 and in use in flying aircraft until the 1980s. Unfortunately Westinghouse's follow up engines were not as good or introduced nothing new, being little more than scaled up J-34s which was NOT good enough to compete with P&W and GE's newer, more sophisticated engines.


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## nuuumannn (Dec 22, 2013)

> though I'm not sure that the second one is unique to axial jets either.



Compressor surge was/is an issue that affects all gas turbines. Modern centrifugal compressors in use in turboprop and turboshaft engines have bleed valves specifically to handle compressor surge at low power settings; these are nominally controlled by electronic engine control units - depending on the sophistication of the engine system. The early incarnation of the Rolls-Royce Avon was prone to excessive compressor surge and had big blow-off valves fitted to the compressor casing, but it was found that mating the more efficient compressor unit of the (by then) Armstrong Siddeley Sapphire to the Avon hot section produced a better and more reliable engine.

Getting back to the original thread subject; I suspect the German firms were under considerable pressure to get working aircraft and engines in service and reliable as quickly as possible, which would have meant that priority would have had to have been placed on certain technology and advances, although the resources were not necessarily there to take advantage of these advanced concepts. Add to that Allied bombing and you have an industry unable to meet the expectations of the equipment being developed, or the demands of the high command.

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## delcyros (Dec 23, 2013)

Shortround6, thanks for Your memo. I am interested in these periods jet engines and just keep notes on the topic, so Your input is greatly appreciated.
What the american jet engine project demonstrates, in my mind, is that the pace of progress was really rapid in this timeframe.
When we think about it the J30 took considerable time to mature but was more efficient than either BMW-003 or JUMO-004 when finished. The J-34 was an awesome compact engine but by the time all problems were ironed out, it was already on the edge of becomeing obsolete in comparison to more powerful engines aviable.



> Getting back to the original thread subject; I suspect the German firms were under considerable pressure to get working aircraft and engines in service and reliable as quickly as possible, which would have meant that priority would have had to have been placed on certain technology and advances, although the resources were not necessarily there to take advantage of these advanced concepts. Add to that Allied bombing and you have an industry unable to meet the expectations of the equipment being developed, or the demands of the high command.



That´s a correct assessment. But to be fair, the option of the RLM to prefer the JUMO-004 was dictated primarely by it´s low risk charakteristics. It was a working jet engine capable to be manufacturerd in the thousends (as poor as it goes but nevertheless). The best class I engine would have been the HeS-030 (RLM called it 109-006) with smaller frontal diameter than either BMW- or JUMO engine, a very good spec. fuel consumption and excellent thrust to power ratio. But then again, in 1941, JUMO and BMW already had engines with the same net thrust power flying, while the HeS-030 was still very much a developmental engine, which still had lots of spare elements buildt into it and many problems yet in fornt of it. Instead of supporting a third engine of this class, Schelp ordered Müller (axial compressor project) and v. Ohain (radial compressor project) to merge for the HeS011 project and it´s diagonal compressor layout. A failure to decide between radial and axial compressor in my mind. I guess that the HeS030 should have been developed further, with a 2 stage turbine and another two compressor stages, as proposed by Müller, who hoped that this design could develop around 1200kp on just under 500kg weight.
That would certainly entail less developmental risk than the complex diagonal layout of the HeS011.
But then again, jet engines were still very much in their infancy and nobody knew for sure which direction was the best in this timeframe.

I guess we all agree that 4000 to 5000lbs jet engines, placed in series production within ww2 are beyond any realistic possibility.
The LW likely developmental path has been well documented in sources:
890Kp JUMO-004B3/4 engines in late 1944 and early 1945 (historical)
930kp JUMO-004D4 engines in early 1945 to mid 1945 (historical)
1000kp (1200kp with reheat) JUMO-004E1 engines in mid 1945 to the end of 1945. (benchtested, scheduled for mass production in mid 1945)

similarely for BMW:
800Kp BMW-003A engines in late 1944 (historical)
800Kp (920 Kp with overrew) BMW-003A2/E1 egines in early 1945 (historical)
1000 Kp (1150Kp with overrew) BMW-003D engines in mid 1945 (benchtested, scheduled for production)
-the BMW-003 was added with an afterburner only in the SU and has been excluded here-

HeS011 (benchtested, flighttested), JUMO-012 (as well as the downscaled -012 derivate called JUMO-004H) (assembled) and BMW-018 (part assembly or assembled, sources vary) were still developmental and should be treated with caution. They are listed according to their developmental stage.


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## nuuumannn (Dec 23, 2013)

> But to be fair, the option of the RLM to prefer the JUMO-004 was dictated primarely by it´s low risk charakteristics.



That's essentially what I mean, but yes indeed I agree with your post and thanks for the like!

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## davparlr (Dec 24, 2013)

delcyros said:


> I guess we all agree that 4000 to 5000lbs jet engines, placed in series production within ww2 are beyond any realistic possibility.



This is true for the axial flow engine but definitely not for the centrifugal flow engine. While low level development activity had been going on with the British jet for quite a while, serious government involvement did not occur until many years after the Germans started their government funded jet engine development, yet the British, and Americans had 4-5000 lb thrust engines running in 1944 and, since 83 production P-80s were delivered by the end of July, ‘45, there certainly was production J-33s in ww2. I think the Germans, with their multi-year head start with government money could easily beaten this by a year or more if they had stuck with the centrifugal flow engines. 

The axial engines are much more complex to develop due to their multiple compressor stages. The Jumo had eight stages of compressors, each stage consisted of a compressor and a stator for a total of sixteen sub-stages. Each sub-stage has to be specifically designed to operate with different airflow characteristics including different velocities, pressures, temperatures, and incidence angles and must be finely tuned to operate efficiently over the entire operational RPM range and variable initial airflow values. In addition, each blade of compressor and stator must be manufactured to tight tolerances to prevent leakage; this is a lot of components. The centrifugal compressor on the other hand has, effectively, only one stage consisting of one moving part, a much easier design and manufacturing problem. In addition, the axial engine has a much longer shaft that can induce vibration problems and could require multiple bearings. The centrifugal engine is much shorter and less problems in these areas, and it tends to be more robust.


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## wuzak (Dec 24, 2013)

davparlr said:


> This is true for the axial flow engine but definitely not for the centrifugal flow engine.



I disagree.

The Metrovicks F.2/4 "Beryl" had tested at about 4000lb static thrust sometime in 1944. But like the centrifugal flow engines it was a prototype, and not a production engine.




davparlr said:


> I think the Germans, with their multi-year head start with government money could easily beaten this by a year or more if they had stuck with the centrifugal flow engines.



Von Ohain's team at Heinkel did stick with the centrifugal engine - for a while. But they weren't getting the improvements that Whittle and Halford were. In some respects they were going backwards. The HeS 6 was overweight and did not have the required performance improvement over the HeS 3. The HeS 8 was the first turbojet officially supported by the RLM (as the 109-001), but its performance never met targets, and it was only ably to muster about 1500lb static thrust. The HeS 8 was abandoned in 1943 - it had well and truly been overtaken by the BMW 003 and Jumo 004, and even by the HeS 30 (109-006), which was itself abandoned so that Heinkel could work on the class II turbojet - the HeS 011.

By the end of the war there were a few class II projects in hand (the HeS 011, Daimler Benz 109-007), as well as class III and class 4 (BMW 018, target of over 7000lb static thrust).




davparlr said:


> The axial engines are much more complex to develop due to their multiple compressor stages. The Jumo had eight stages of compressors, each stage consisted of a compressor and a stator for a total of sixteen sub-stages. Each sub-stage has to be specifically designed to operate with different airflow characteristics including different velocities, pressures, temperatures, and incidence angles and must be finely tuned to operate efficiently over the entire operational RPM range and variable initial airflow values. In addition, each blade of compressor and stator must be manufactured to tight tolerances to prevent leakage; this is a lot of components. The centrifugal compressor on the other hand has, effectively, only one stage consisting of one moving part, a much easier design and manufacturing problem. In addition, the axial engine has a much longer shaft that can induce vibration problems and could require multiple bearings. The centrifugal engine is much shorter and less problems in these areas, and it tends to be more robust.



At the end of the day the main problems exhibited by German turbojets was in the combustion chambers and turbines. And this was due largely to materials not being able to withstand the temperatures, with air cooled turbine blades being developed as a result.

AA Griffiths wrote a paper on an axial flow gas turbine engine in 1926. He showed mathematically how the compressor should be designed, as opposed to previous attempts. He included a case study of an engine with a multi-stage compressor, a single stage turbine to drive the compressor and a single stage "free" turbine to drive a propellor. A model engine based on his thesis was built and tested by 1928.

While the British found it easier to develop the centrifugal flow compressor, it doesn't follow that the Germans did. Von Ohain's original engine used a centrifugal flow compressor and radial in-flow turbine because it was simple, cheap and easy to make for a proof-of concept. Not that he thoughtthat the centrifugal compressor was the way of the future.


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## delcyros (Dec 24, 2013)

davparlr said:


> yet the British, and Americans had 4-5000 lb thrust engines running in 1944 and, since 83 production P-80s were delivered by the end of July, ‘45, there certainly was production J-33s in ww2. I think the Germans, with their multi-year head start with government money could easily beaten this by a year or more if they had stuck with the centrifugal flow engines.



Correct me if I am wrong but I don´t think that the americans had any 4000 to 5000lbs jet engines running in 1944. Even in 1945 their best engine was the I40/J33 which made 3,850lbs until Allison uprated it in late 1945 to 4,000lbs on the bench. All P80A1 had only 3,850lbs rating and the uprated engine was not delivered before 1946. The british had the R.B.41 Nene which offered the required thrust rating but first benchtests were late in 1944 (oct, IIRC) and the engine was far from production ready in 1944 and still looked around for a suitable platform (Vampire and P80 got them as experimental fits in mid/late 1945, with the P80 beeing badly damaged due to a Nene engine failure) and finally missed ww2 by a good margin.
The germans may have had a headstart but they needed to invent new cooling techniques due to the spare free requirements. Without them, just go along with the JUMO-004A, which was benchtested to 1000kp thrust rating in 1941 or the JUMO-004C, which eventually was a classical -004A with afterburner added (1200kp). They couldn´t do that, hence they reverted to the derated JUMO004B (1944), the slightly improved JUMO004D (1945) and the afterburner aequivalent JUMO-004E (1945).

I fully agree that the axial compressor layout was more complicated than the radial layout but nothing fundamentally new. It inherited a lot experiences from axial compressor layouts in steam turbine propulsion (both navy steam turbines and electric power generation plants).

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## davebender (Dec 24, 2013)

> How much and what kinds of raw materials would the Germans have needed to make their without restrictions on materials?


Germany had plenty of nickel until mid 1944 when Finland changed sides. Chromium was in short supply for the entire war.

*1943 Chromium requirements per engine.*
27.41kg DB605
21 lbs Jumo 004A jet engine.

It's readily apparent that raw material shortages had little to do with decision not to mass produce Jumo 004A engine during 1943.


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## wiking85 (Dec 24, 2013)

davebender said:


> Germany had plenty of nickel until mid 1944 when Finland changed sides. Chromium was in short supply for the entire war.
> 
> *1943 Chromium requirements per engine.*
> 27.41kg DB605
> ...



The V-2 took a lot of nickel for its nozzle, so the 'extra' went to that in 1944. Also I think they expected that the jet engines, being a new technology, would see more attrition than the more proven piston engines. I agree that it was a matter of priorities rather than anything else. If they had used all the DB603 raw materials that would have been saved by not producing the ME210/410, then there would have been a significant amount of nickel and other metals for Jumo.

BTW what raw materials were needed? IIRC Molybenium, Coblat, Chromium, and Nickel, but what about Tungsten and Copper?

Edit:
https://en.wikipedia.org/wiki/Junkers_Jumo_004


> The initial 004A engines built to power the Me 262 prototypes had been built without restrictions on materials, and they used scarce raw materials such as *nickel, cobalt, and molybdenum* in quantities which were unacceptable in production.


I think the last two were the real issue.


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## davebender (Dec 24, 2013)

I'm no metallurgist but I know alloy metals can substituted to some extent when making high temperature steel. For example we have this quote:
http://www.ww2aircraft.net/forum/engines/jumo-004-a-12983-3.html


> "In 1936, when development work on the Jumo 004 started, a high-temperature Krupp steel known as P-193 was available. This material, which contained Ni, Cr, and Ti, could be given good high-temperature strength by means of solution treating and precipitation hardening. Krupp developed an improved version of P-193 known as Tinidur. It was of the same type as Nimonic 80, which was used in British Gas turbines from 1942 but contained over 50 percent iron (which was replaced by Ni in Nimonic 80) and this caused a rapid drop in creep strength at 1080F (compared to 1260F for Nimonic 80). While Krupp knew that Tinidur could be improved by increasing the Ni content from 30 to 60 percent, there was a recognition that Ni would not be available. The Ni content was therefore left at 30 percent. Similarly, work on cobalt-based alloys was also shelved due to a shortage of cobalt." (Journal of Engineering for Gas Turbines and Power, October 1997, Vol. 119)


Albert Speer provides considerable detail concerning Nickel imports from Finland so we can dismiss talk of a nickel shortage. Nickel ore was piling up at Petsmo faster then Germany cared to transport it to the Ruhr.

So why wasn't Jumo 004A engine placed into mass production with turbine blades made from Nimonic 80 alloy which relies largely on Nickel? There must be reason(s) besides shortage of alloy metals.


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## davparlr (Dec 24, 2013)

wuzak said:


> I disagree.
> 
> The Metrovicks F.2/4 "Beryl" had tested at about 4000lb static thrust sometime in 1944. But like the centrifugal flow engines it was a prototype, and not a production engine.


Yes, I kinda overlooked the Metrovick engine. According to Kay, the Beryl certainly ran at 3500 lb/thrust in 1943 and could possibly have been in production by 1945 (my limited opinion).



> Von Ohain's team at Heinkel did stick with the centrifugal engine - for a while. But they weren't getting the improvements that Whittle and Halford were. In some respects they were going backwards. The HeS 6 was overweight and did not have the required performance improvement over the HeS 3. The HeS 8 was the first turbojet officially supported by the RLM (as the 109-001), but its performance never met targets, and it was only ably to muster about 1500lb static thrust. The HeS 8 was abandoned in 1943 - it had well and truly been overtaken by the BMW 003 and Jumo 004, and even by the HeS 30 (109-006), which was itself abandoned so that Heinkel could work on the class II turbojet - the HeS 011.



There is no doubt that Heinkel’s early engine work was hampered by secrecy and poor engineering. His engine was much more complicated than those of Whittle and Halford but it is difficult to believe that Germany did not have the capability to engineer compressor designs equivalent to the Brits.



> By the end of the war there were a few class II projects in hand (the HeS 011, Daimler Benz 109-007), as well as class III and class 4 (BMW 018, target of over 7000lb static thrust).


It is inescapable to come to the conclusion that the Germans had some serious problems with their engine design work when the British, and the Americans even earlier than the Brits, were able to run 4000-5000 lb thrust engines in 1944. The Americans, using British technology was running the J-33 in early ’44 and was in production in early ’45. The Germans never came close to being able to do this. It is my opinion that the centrifugal engine was easier to engineer and manufacture (a whole lot less parts) and was also easier to increase thrust levels. Doubling thrust was simply increasing the size and could be done with relatively inexperienced engineers. GE began work on a 3-4000 lb thrust engine in June, 1943 and the engine was run at 4000 lbs thrust in February, 1944, doubling the thrust of the previous engine. This engine went on to become one of the most robust engines ever built and was in production until 1959 and was in military use much longer (The USAF was still using them when I was in the AF in 1970, and some are still flying today).



> At the end of the day the main problems exhibited by German turbojets was in the combustion chambers and turbines. And this was due largely to materials not being able to withstand the temperatures, with air cooled turbine blades being developed as a result.


This is true, but at the beginning of the day there was a lot of complex engineering and manufacturing that needed to be done before they even got to the end of the day.



> While the British found it easier to develop the centrifugal flow compressor, it doesn't follow that the Germans did. Von Ohain's original engine used a centrifugal flow compressor and radial in-flow turbine because it was simple, cheap and easy to make for a proof-of concept. Not that he thoughtthat the centrifugal compressor was the way of the future.



Yes, and I think that was a mistake.



delcyros said:


> Correct me if I am wrong but I don´t think that the americans had any 4000 to 5000lbs jet engines running in 1944. Even in 1945 their best engine was the I40/J33 which made 3,850lbs until Allison uprated it in late 1945 to 4,000lbs on the bench. All P80A1 had only 3,850lbs rating and the uprated engine was not delivered before 1946.


According to Antony Kay’s book “Turbojet History and Development 1930-1960, Vol. 2”, the GE I-40 (J33) was run at 4000 lb thrust in February, 1944. Ray Wagner in his “American Combat Planes” along with E.T. Wooldridge,Jr.’s “The P-80 Shooting Star” stated the YP-80’s engine was also 4000 lb thrust, but, although they are reliable books, I not as sure. Of course 3,850 lbs is certainly in the 4000 lb range.



> The british had the R.B.41 Nene which offered the required thrust rating but first benchtests were late in 1944 (oct, IIRC) and the engine was far from production ready in 1944 and still looked around for a suitable platform (Vampire and P80 got them as experimental fits in mid/late 1945, with the P80 beeing badly damaged due to a Nene engine failure) and finally missed ww2 by a good margin.



I cannot argue this point. The J33 took one year to go from test bench to production. Of course this also applies to German engines which were not even at the test bench stage.

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## davparlr (Dec 24, 2013)

Merry Christmas. "Peace on earth and good will to all"


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## fastmongrel (Dec 24, 2013)

An excuse to post one of my favourite pictures the Meteor F1 with Metrovick F2 engines


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## wuzak (Dec 24, 2013)

fastmongrel said:


> An excuse to post one of my favourite pictures the Meteor F1 with Metrovick F2 engines
> 
> View attachment 250621



And, from what I understand, performed better than the Whittle engined prototypes.

The F.2 wasn't put into production because of reliability issues. I wonder if they were any greater than those being experienced by the Germans.


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## Shortround6 (Dec 24, 2013)

There is little difference between a centrifugal compressor used on a piston engine and one used in a jet engine except size. In fact at least one company (and perhaps a collage research group) was able to make working turbojets for drone missile use in the late 40s by sticking a combustion chamber (one of the tricky bits) _between_ the compressor and turbine of a standard GE "B" series turbo charger. By hanging the single chamber combustion chamber outside the diameter of the compressor and turbine I believe they were able to keep the same spacing between the two units (keep same shaft and housings). 
Granted you need a working turbo charger to pull this trick 

Centrifugal compressors were good for about 3:1 pressure ratio at the beginning of the war and went to 4:1 or just a bit beyond at the end (for a single stage). It seems that axial compressors needed 6-8 stages (or more) to get a 3:1 pressure ratio in the early part of the war _in practice_ despite what theory said. As the war went on and more research/development was done things got better (but slowly). Pressure ratios of 5:1 or better from axial flow engines only really came into use several years post war. By the early 50s however Pressure ratios of over 10:1 were being run (even if not in service) and by the 60s pressure ratios of 15:1 were being exceeded by a a few engines. 

Some companies with marine/industrial steam turbine experience were able to build successful _aircraft _gas turbine engines, some were not. It seems that steam turbine experience, while useful, was no guarantee of a successful aircraft turbine engine. 

The highest pressure ratio I have found for a single stage centrifugal compressor jet engine is 4.6:1 and that is in the early 50s. A late model P&W J-48 (modified licensed RR Tay) that offered 7,250lbs thrust dry at sea level and 8500lbs wet for 2200lbs _without _ after burner for 2200lbs dry weight. This was probably the last gasp of the centrifugal compressor in a _big_ engine although it continues in use in small engines to this day. 

It took the rest of the world until the early/mid 50s to get the axial engine to show a clear superiority over the centrifugal engine. 

Lets not get too hung up on test results and service engine powers either. Many engines were tested to much higher powers than they were used in service several years earlier. RR ran a Merlin at 1800hp in 1938 and ran it for over 10 hours at 1600 hp if I remember right. A P&W engineer ran an R-2800 at 3500hp for a least a few seconds using a truly astounding amount of water/alcohol and it was a "B" series engine to boot which were never rated by P&W at over 2000hp dry or rated by the Army at much over 2500hp wet. The higher powered engines were "C" series engines. BTW the engine survived 
AN engine hitting 4000lbs thrust on test means exactly that, 4000lbs on test, on the ground, for a time of possible a few seconds or possible several hours, it does NOT mean it was installed and flown in an aircraft at that rating at that time.

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## nuuumannn (Dec 24, 2013)

The thing about early British centrifugal flow engines is that Rolls-Royce in particular had been working with centrifugal compressors for years in superchargers, longer than its German counterparts, so there was a lot of accumulated experience, knowledge and data to fall back on when that firm began to build them. It was only natural that Rolls begin engineering these compressors because of what it already knew. Its first production axial flow compressor was riddled with problems, particularly with compressor surge.



> (Vampire and P80 got them as experimental fits in mid/late 1945, with the P80 beeing badly damaged due to a Nene engine failure)



The P-80 prototype was powered by a Halford H.1, not a Nene.


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## Shortround6 (Dec 24, 2013)

ALL German WW II combat piston engines use centrifugal compressors (superchargers) and the Germans had been making such superchargers since the early 30s. Most superchargers of the late 20s and early 30s were violable on commercial engines and were NOT military secrets. Granted with 70-80 octane fuel the need or actual use of a high pressure ratio compressor is rather limited so some rather bad designs could see a fair amount of use with no one being the wiser. 

By the way the P-80 prototype badly damaged the Halford H.1 engine not the other way around. The intake duct was made of too thin a gauge sheet metal and not rigid enough. On a ground run of the engine the intake duct duct collapsed and part of it was sucked into the engine. Blaming the engine for the damage doesn't seem quite fair.


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## delcyros (Dec 25, 2013)

I like Anthony Kay´s books, and am aware that he refers to the I40 engine run at 4,000lbs on the benchtest. However, the production version manufactured in 1944 and through 1945 were derated to 3,850lbs static thrust.
The germans appearently never proceed with a jet engine project of 4,000lbs to 5,000lbs range.
The HeS006, JUMO-004 and BMW-003 all were 1750 to 2450lbs range, the He-S011 and Db-007 was 2450 to 3000lbs range and the JUMO012 and BMW-018 was in the 6,000lbs to 8,000lbs thrust range.


snippet from
Lockheed P-80A Shooting Star



> The first 345 aircraft of this contract (serials 44-84992 to 44-85336) were designated P-80A-1-LO. Some of them were powered by the 3850 lb.s.t. General Electric J33-GE-11 turbojet, the production version of the I-40 which had powered the XP-80A and the YP-80A. Others were powered by the Allison J33-A-9, a version of the same engine built by the Allison Division of the General Motors Corporation.
> 
> The next 218 aircraft in the contract (44-85337 to 44-85941 and 45-8301 to 45-8262) were built as the P-80A-5-LO production block and differed by being equipped with the more powerful 4000 lb.s.t. Allison J33-A-17. The -5 also introduced a boundary layer control splitter plate inside the air intake. The landing light was relocated from the nose to the nosewheel landing gear strut. Later, the initial production P-80A-1-LOs were retrofitted with the uprated Allison engine during routine engine overhauls.



It might be noticed that the integration of the engine entailed thrust losses due to the long exhoust pipe and the intake ducts. Installed thrust was slightly lower than 3,850lbs rated for the first 345 P80A aircraft and has been calculated by NACA to the aequivalent of about 3,500lbs.

While the P80 prototype was indeed driven by an H1b, and the P80A prototypes were driven by I40/J33, one YP-80A was modified for an experimental fit with Nene engine as I mentioned:



> serial no. 44-83027 was modified by Rolls-Royce to flight test the B-41, the prototype of the Nene turbojet. On November 14, 1945, it was destroyed in a crash landing after an engine failure.



So it was certainly possible to fit the Nene -at least theoretically- in an P80A airframe.

The HeS011A engine was initially buildt without reference to spare resources (the radial compressor milled out from a single block of aluminium took about 3,000 manhours to produce, roughly five times the total production time of a single series made JUMO-004B). It was quite complicated and offered only 1,115kp (=~2460lbs) at 9920rpm (HeS011 AV01, 1st prototype engine). That´s comparable to the performance offered by the experimental BMW-003D (which was lighter smaller)...
It was, of course hoped that thrust increase by an increase in rpm could be attained for 1,300kp in the - version and 1,500kp in the -C version but this is entirely speculation in absence of any engines made to these specifications.


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## davparlr (Dec 25, 2013)

Yeah, there was something nagging at me on that 4000 lbs thrust for the YP-80. I just couldn't chase it down.


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## nuuumannn (Dec 25, 2013)

> On a ground run of the engine the intake duct duct collapsed and part of it was sucked into the engine. Blaming the engine for the damage doesn't seem quite fair.



Exactly. As for RR superchargers, despite the German engines having them in WW2 the knowledge Rolls accumulated _did _prove useful in the design of the compressors, but you knew that already, SR. The first RR engine with a supercharger was the Condor V of 1925 that had a exhaust driven turbo supercharger, although it did not go into production.



> So it was certainly possible to fit the Nene -at least theoretically- in an P80A airframe.



I can't say I was aware of this. The problem with the Nene was that at this time it still needed work by the end of the war in Europe. Hawker did propose a Fury with a B.41 (Nene) jet engine with intakes in the wings and a split exhaust pipe in 1944 as the P.1035; this, via the P.1040 eventually evolved into the Sea Hawk.


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## wuzak (Dec 26, 2013)

I have just read that there was another centrifugal jet project from Germany. It was from BMW.

BMW made turbochargers with centrifugal compressors and an air cooled axial flow turbine.

The BMW project took advantage of this knowledge, using an air-cooled turbine and a two stage centrifgal compressor. The axial flow turbine was rated for 900°C. This project, the P.3303, began in 1938 but was cancelled not long after the declaration of war (ie late 1939). It was decided to concentrate on the axial flow project, the P.3302 which would later become the 109-003.

The P.3302 project had its origins at Bramo before BMW took them over. It was originally designed for a combustion temperature of 600°C, but was soon changed to 900°C in co-operation with BMW, using their air-cooled turbine. Not long after, BMW took over Bramo. 

Bramo had a second axial flow project, the P.3304. This differed in having counter rotating compressor stages. The theory there was there was no need for stator blades, and that the compressor would be more efficient (Griffith also experimented with counter rotating compressor stages when at the RAE, IIRC). The P.3304 would be officially known as the 109-002.

Bramo had ranked the types of compressors in order of desireability as 1. counter-rotating axial, 2. single rotating axial and 3. centrifugal. Bramo chose the single rotating axial compressor to start with, since it promised fewer development difficulties than the counter-rotating type. The latter began later (~1939), being cancelled early in 1942.


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## delcyros (Dec 27, 2013)

BRAMO was very advanced before beeing bought out by BMW. There are believable reports suggesting that they had an experimental jet engine flying before ww2 in 1939 on a testbed.


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## stona (Dec 27, 2013)

delcyros said:


> BRAMO was very advanced before beeing bought out by BMW. There are believable reports suggesting that they had an experimental jet engine flying before ww2 in 1939 on a testbed.



Reports from where?

I don't know much about jets but I'm familiar with the various machinations of the RLM in relation to some of these programs 

Bruno Bruckmann and Hermann Oestrich at Bramo were visited by Hans Mauch of the RLM in 1938 (he also went to BMW, Daimler Benz and Junkers) to discuss gas turbines and jet propulsion. The Bramo men made it clear that they did not think that they could produce an efficient gas turbine and that they would continue trying to increase aircraft performance using a piston engine to drive a multi blade ducted fan. An experimental system was flown on an Fw 44 in October 1938. The Fw 44 was a two seat, biplane trainer for those unfamiliar with the type.
A rather more ambitious power unit consisting of a Bramo Twin Fanfir driving a large variable pitch ducted fan was also tested at DVL Gottingen in 1938.
Neither is an experimental jet flying before the war.

It was as a result of these projects giving disappointing results that the Bramo team started research and development of a turbojet. They collaborated fully with BMW from October 1938 until the acquisition of Bramo by BMW shortly thereafter, July 1939 I think, but haven't checked.

The BMW team at Munchen-Albach had already started a two stage centrifugal turbo jet and the Bramo team at Berlin-Spandau an 'axial counter rotating unit' [quote because I'm not sure exactly what that is!]by the time of the merger. This Bramo developed engine was placed under RLM contract 109-002.

The BMW 109-003 was an axial turbojet which used Loehner's turbine from the centrifugal engine which was dropped. This was the engine which finally ran (at Spandau) in August 1940, was eventually coaxed into giving 440 Kg of thrust and was cleared for flight in November 1941. Two of these engines flew in Me 262 V1 on 25th March 1942. They both flamed out. The developed 003A-0 didn't fly until 17th October 1943 under a Ju 88.

Cheers

Steve


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## delcyros (Dec 27, 2013)

They experimented with not yet authochthonious (self sustained) jet propulsion aggregats, which lead to P3302 series types.
Ok, experimentation with jet engines was not so fundamentally new and it was still a long way to a working examples but nevertheless these approaches were very early.


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## wuzak (Dec 27, 2013)

stona said:


> the Bramo team at Berlin-Spandau an 'axial counter rotating unit' [quote because I'm not sure exactly what that is!]by the time of the merger. This Bramo developed engine was placed under RLM contract 109-002.



In a conventional axial compressor each compressor stage is followed by a fixed stator.







In the axial counter-rotating unit the stators are replaced by another set of rotors which rotate in the opposite direction. There are, theoretically, benefits, but there is a big downside - complexity.

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## fastmongrel (Dec 28, 2013)

Theoretically as Steam is a Gas everything from Parsons onward is a gas turbine. I naively thought that people who worked in Steam Turbine development would have been the best people to work on Gas Turbines but that doesnt seem to have been the case are the two disiplines not compatible.


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## davparlr (Dec 28, 2013)

fastmongrel said:


> Theoretically as Steam is a Gas everything from Parsons onward is a gas turbine. I naively thought that people who worked in Steam Turbine development would have been the best people to work on Gas Turbines but that doesnt seem to have been the case are the two disiplines not compatible.



Not knowing anything about steam turbines, I would guess the aerodynamics of a steam turbine vs a jet turbine would be similar, however, vane cooling would be more of an issue with a jet turbine, and, I suspect gas velocity maybe a factor. I think there may be some similarity between a steam turbine and a compressor but not as much.


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## delcyros (Dec 28, 2013)

Steam turbines didn´t used airfoil shapes for the rotors. So they were more simplier to be constructed but nevertheless there is some relationship between both technologies and some shared layouts. Needless to say that the Steam turbine wasn´t self-sustainable but relied on a feed steam manifold pressure provided by seperated boilers, which canceled the need to buildt a hot turbine.


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## b0ned0me (Dec 28, 2013)

delcyros said:


> Steam turbines didn´t used airfoil shapes for the rotors.


I did originally post that this was what Griffith pointed out, but on further looking around, I think I'm wrong. His paper seems to be specifically on gas turbines, and focused on compressors.
Which points to the other major challenge for steam people/companies - they had no experience with compressors. I think the temperature and the compressor design are the two trickiest bits, which explains why areoengine firms with prodigious experience of high *temperatures *and compressor dynamics basically ate their lunch.


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## Aozora (Dec 28, 2013)

delcyros said:


> Steam turbines didn´t used airfoil shapes for the rotors. So they were more simplier to be constructed but nevertheless there is some relationship between both technologies and some shared layouts. Needless to say that the Steam turbine wasn´t self-sustainable but relied on a feed steam manifold pressure provided by seperated boilers, which canceled the need to buildt a hot turbine.



Photos of Parsons ship's turbines; the blades still needed to be given a modified airfoil shape to direct the steam through successive sets of rotors, otherwise the turbines wouldn't work at all well:










Steam Turbines


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## Shortround6 (Dec 28, 2013)

The steam turbine guys have an advantage in that they know how to make disks with many replaceable blades. They Know how to and have the machinery to make the airfoil shaped blades. 

A minor problem is that the materials they are used to working with don't work at the temperatures a gas turbine needs. 

A bigger problem is that the compressor works the exact opposite of a Steam turbine, the steam turbine _starts_ with a high pressure gas/fluid and allows it to expand in carefully controlled stages to get the most work out of it before the pressure drops too low to be useful. 
The axial compressor of a jet engine (or gas turbine) starts with a low pressure gas/fluid and compresses it in carefully controlled stages to get the highest possible pressure while using the least amount of power. 

Many steam turbine firms were also used to thinking in terms of HP per ton instead of HP per pound (or KG). Of course Steam turbine firms were also used to thinking of overhaul life in thousands of hours not tens of hours (or a few hundred)


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## wuzak (Dec 28, 2013)

Aozora said:


> Photos of Parsons ship's turbines; the blades still needed to be given a modified airfoil shape to direct the steam through successive sets of rotors, otherwise the turbines wouldn't work at all well:
> 
> 
> 
> ...



For turbines there are two kinds of blades - reaction and impulse. I think that the reaction blades are aerodynamically shaped. Less so in the case of the impulse blade.

From the looks of the first picture, the five rotors to the right at impulse blades and the rest are reaction.






That image shows how importantthe stators and nozzles are as well. These aren't shown in the rotor set pictures.


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## delcyros (Jan 8, 2014)

I think the latter picture quite elobately shows this. However, even then, the early gas turbines were not reaction turbines but impulse types. Müllers HeS030 was the first axial Reaction type gas turbine to my knowledge. This yielded significant improvements in efficiency of the engine.

Regarding the late ww2 german jet engine developments, I´d like to give some further thought on BMW projects.
BMW developed the P3302/3 into the BMW-003. By late 1940 they started another, initially preliminary project which would eventually end up in the large BMW-018 engine, of which at least two prototypes have been buildt, though evidence suggest that only the compressor has been trialed before the facilities were captured and the BMW-018V2 was destroyed (the -V1 was destroyed in oct. 1944 by an air raid).
However, Schelp went into the class II buissness with the HeS011 triggering the project in 1942. The RLM was not convinced that the diagonal compressor is necessarely the most efficient form of a class II jet engine and urged Schelp to order BMW to exploits it´s experiences in the more developed BMW-003C/D projects to scale the axial engine up into a suitable class II engine as a backup.
This was the late 1943 or early 1944 starting point of the BMW-P3306 projected jet engine. At wars end, the design of the BMW-P3306 V1 had been completed, though no parts have been assembled. The outlines of the projected engine read like:

diameter: 850mm
length: 3200mm
compression ratio: 4.0:1 (calculated)
thrust: 1700kp at 7500 rpm (calculated)
sfc: 1.15 (claculated)
7 stages axial compressor (reaction type)
1 stage axial turbine
annual compressor with 20 burners

Altough not run in ww2, one engine was made to this specification and trialed in march 1948. The head of the BMW jet engine project was hired by the french to set up a jet engine design bureau in sept. 1945. Just 3 weeks later, he presented to complete design of an engine "scaled up from the known BMW-003 and able to produce 1700kp". As You can imagine, he didn´t created this engine in three weeks in 1945, but what he was able to do is to recollect the complete set of ww2 BMW-P3306 drawings. He never referred to P3306 but I have a couple of drawings and it´s nothing else, it´s the realisation of the BMW ww2 jet engine.
The design was submitted and after the german design team signed a second contract in 1946, S.N.E.C.M.A. started preperation for part assembly of two jet engines, redesignated ATAR-101. The -V1 prototype was still a perfect BMW-P3306 with Riedel starter unit, hollow air cooled turbine blades from rather mild steel and adjustable exhoust area controlled by a jet needle. In the second prototype -V2 the mild steel was replaced by high Nickel and chromium content steels, resulting in simplier construction and increased rpm and allowed exhoust temperature.
Delays in S.N.E.C.M.A production (particularely in producing hollow turbine blades) made compressor parts aviable in late 1946 and in march 1948 the -V1 prototype was benchtested for the first time. It worked according to specification and developed 1700 kp thrust at 7500rpm as intended.
Just two months later, the-V2 became avaiable and produced 2,200kp thrust at 8,050 rpm. The following development of the ATAR-101A and -B (they removed the Riedel starter engine in the hub and changed the tail to exhoust eye-type lid shutters) is entirely post ww2.





In my mind, a much more reasonable engeneering approach than the HeS011. Note how much the inavaiability of proper heat resistent materials affected the performance of this engine.

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## wuzak (Jan 9, 2014)

delcyros said:


> The RLM was not convinced that the diagonal compressor is necessarely the most efficient form of a class II jet engine and urged Schelp to order BMW to exploits it´s experiences in the more developed BMW-003C/D projects to scale the axial engine up into a suitable class II engine as a backup.



As far as I am aware no manufacturer was instructed to use the diagonal compressor other than Heinkel. Heinkel was so instructed because they were trying to move away from centrifugal compressors.


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## delcyros (Jan 9, 2014)

Am not so sure. The diagonal compressor layout was Schelp´s pet idea. Heinkel not only had a radial jet engine project (HeS08, class I) but also a very innovative and successful axial jet engine project (HeS030 -class I) and Schelp ordered both axial and radial teams to merge for a joint class II project (to become the HeS011 with diagonal compressor).
In defense of Schelp, he hoped to get the best of both worlds but as it turned out, both teams were working hard to avoid the worst of both in the HeS011.
There were two backups to the class II HeS011, the aforementioned BMWP3306, which was a scaled up BMW-003 and the JUMO-004H, which was a scaled down JUMO-012, which unlike the BMW-003 wasn´t yet a fully stabilised design, handing all developmental advantage to BMW´s class II backup project.


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## Juha (Jan 10, 2014)

davebender said:


> I'm no metallurgist but I know alloy metals can substituted to some extent when making high temperature steel. For example we have this quote:
> http://www.ww2aircraft.net/forum/engines/jumo-004-a-12983-3.html
> 
> Albert Speer provides considerable detail concerning Nickel imports from Finland so we can dismiss talk of a nickel shortage. Nickel ore was piling up at Petsmo faster then Germany cared to transport it to the Ruhr.
> ...



Sorry for the late answer, I noticed your message only now.
Maybe the fact that the Kolosjoki/Nikel Nickel mine situated only c. 70km from frontline generated some uncertainty to Germans on the continuity of the Nickel supply from Finland. 

Juha


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## swampyankee (Jan 10, 2014)

wuzak said:


> The radial in-flow turbine is the type of turbine used on modern turbochargers. The GE turbos used axial turbines, as did most of the jets of WW2.
> 
> Basically the radial in-flow turbine works like the centrifugal compressor, but the opposite way.
> 
> ...



I believe that the normal English language term for "diagonal" compressor is mixed-flow compressor.


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## johnbr (Feb 7, 2015)

D's any one here have cutaway or more info on the JUMO-004H engine.


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## tomo pauk (Feb 7, 2015)

Some data found in the von Ghersdorff et al:
-air flow: 33 kg/s
-11 stage compressor (axial)
-pressure ratio: 5.5
-8 combustion chambers
-2 stage turbine (axial)
-3950 mm long, diameter 860 mm, dry weight 1100 kg
-static thrust 17.6 kN at 6600 rpm, spec. consumption 117 kg/kNh

No production, at least how I read it there.


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## kool kitty89 (Feb 12, 2015)

tomo pauk said:


> Some data found in the von Ghersdorff et al:
> -air flow: 33 kg/s
> -11 stage compressor (axial)
> -pressure ratio: 5.5
> ...



Wiki's also listing the 004G as what appears to be a signle spool 11 stage 8 combustion chamber development of the 004, but I'm not seeing other references to this, so it may not be accurate. I know the 004H was a scaled down derivative of the 012 design, but the G either seems to be a related derivative or a simpler single-spool follow-on to the existing 004.


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## kool kitty89 (Feb 13, 2015)

I've been meaning to comment on a bunch of points in this discussion for months now, but kept getting distracted, sooo, here goes.





delcyros said:


> [+] ability to relight in flight (Seems trivial but THIS WAS A BIG CONCERN. -the primary reason to give early jet A/C so large wing areas and good low speed handling -that if engine was lost during take off/landing it doesn´t critically effect the survivability of the pilot)
> 
> the first jet engine which adressed most of these points -to my knowledge- was the BMW-003A1. The BMW- jet engine project took longer than Junkers -004 but it was a more matured design. Lighter and smaller, better thrust-weight ratio, 150 hours certified lifetime for the hot turbine section (the compressor section had a significantly larger lifetime), an accelerator valve to prevent the burn out of the turbine blade due to rapid throttle changes (AFAIK, this was the first jet engine, whiches throttles could be less gingerly advanced and returned without fear of damaging the engine), good altitude performance with very few documented compressor stalls (could be relighted in flight) and overrew capability for increased thrust. There was one aspect which was not included, an automatic exhoust jet needle controll such as employed by Junkers, requiring the operator to controll this aspect.


I've gotten a lot of mixed information on these issues and actually had the impression the 004 series (or at least the most common service models) were capable of being re-started from inside the cockpit, though maybe more variables complicated this. (oddly, some flight sims seem to model the reverse of what you show: 004s able to be re-started vs 003s being totally dead on flame-out - the Il-2 series seems to do this fairly consistently)

On a side note, with the 003 having so many advantages, it's a bit odd there were no serious considerations for producting an Me-262 variant with those engines. (probably a fair argument that slating those engines for thatpurpose would have made more sense than reserving them for the likes of the He-162 ... including possibly making the Me 262 easier to fly -more fool-proof engines and throttle control, lower overall weight, lower stall speed, higher roll rate, longer endurance/range and higher top speed and climb rate -at very least if including emergency overrev thrust)




> Radial compressor jet engines like those mentioned previously were probably better suited for the low thrust ratings concerned in ww2 but required more machining, milling and higher grade steel ressources.


This is true for some of the more elaborate machined impellers, but Heinkel appears to have been using a sheet metal composite construction for both their compressors and turbines (and a large portion of the diffusor and combustion chamber sections too). The compressor of the HeS 3, 6, and 8 being made from a steel hub with aluminum blades/vanes mated to it. (the radial turbine was similar but all steel, I believe Krupp stainless steel similar to the Tinadur alloy Junkers adopted)

There's a lot of nice info on this here:
ASME DC | Proceedings | GT1999 | Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery | Pioneering Turbojet Developments of Dr. Hans von Ohain â€” From the HeS 1 to the HeS 011
(which I'm glad they've finally made free to public access -years ago a big chunk was viewable though google's cache, but hasn't for quite some time ... sans paying the $25 fee they were asking)




> The requirement to produce only jet engines with spare free charakteristics would preclude the idea that the Luftwaffe could have fielded a working 4000 to 5000lbs jet engine in time for ww2, be it radial or axial design. As I mentioned previously, this requirement set back the whole jet engine project by approx. 1.5 years. Many of the issues encountered historically really just need to be adressed in order to be able to move beyond this low thrust rating to higher performance engines.


I'll mostly agree here, with the exception that ~5000 lb engines of relatively primitive construction might have been possible in the time frame, but too bulky to be all that useful. The 3000~4000 range is more seeable. A german equivalent of something as conservative as the Halford H.1/Goblin would have been interesting ... or scaled up a bit larger. (the later Ghost was still pretty simple ... also much heavier than comparable Whittle-based designs at Rolls Royce and GE -that and a Ghost size engine probably would have been more in the 3200~3600 lb thrust range given the thrust the Goblin itself was putting out at the time)

A Jumo 004 derived turbine and combustion section mated with a single-stage centrifugal compressor might have been in that vein.

On the other hand, Ohain actually managed to get the diameter of his engines down considerably with the HeS-8, and applying that compressor+axial diffusor arrangement on a larger scale might have worked quite well too. (the merits of the annular combustion chamber design in use is another matter though and -along with the uncooled turbine- one of the bigger problems with the engine) Perhaps adopting Muller's combustor and turbine designs or portions of them would have helped with this.

Regardless of this, the HeS-011 was a waste (costly and impractical design) ... and cancelling the 006 (HeS 30) was an even bigger mistake. And while Heinkel really stretched their design teams thin with all those jet and ducted fan designs, it still might have made sense to have 2 working designs in progress, perhaps with as much commonality in the hot section as possible. 


However, on the note of the HeS-6. They had a working, flight-quality 1300 lb thrust engine in late 1939 yet they abandoned that in favor of Muler's axial design and sightly later began the HeS-8 design as a back-up. It seems that it would have been much more prudent to stick with what was already working and continue developing the HeS-6 to something practical for mass pruduction and service (even if ideally to be retired in favor of more advanced replacements fairly soon). It's a bulky design that would not have worked on the Me 262 or existing He 280, but given the He 280 was still on the drawing board at the time, adapting it to allow mid-wing mounting (or high wing with large under-slung nacelles) of the HeS-6 would have made plenty of sense.

At worst it would have made a usable, if short life and fuel hungry (existing HeS 3 and HeS 6 used 1.6 lb/lbf/hr -though some sources claim improvements on the HeS 6, the above pdf document states otherwise and appears to be a better authority on these engines than most others) engine at a time when nothing else was production ready ... or possibly proved unsuitable for service use but at very least allowed the He-280 to fly earlier. (important for flight testing AND especially for Udet's conditions for the Heinkel-Hirth merger hinging on the He-280's flight under jet power)

It was making thrust in 1939 that the HeS 8 didn't manage until around the time of its cancellation in 1942 for only modestly more weight, less complexity, and a good bit larger diameter. (appears to have been around 38 inches wide to the approximately 30 inches of the HeS 8 and 36 inches of the HeS 3 -from the drawings I've seen, the HeS 6 used a similar diameter impeller to the HeS 3, but much broader chord of the blades; this would allow for a more modest increase in diameter and also explain the higher mass flow but identical 2.8:1 compression ratio to the HeS 3 -larger diameter centrifugal compressors usually increase compression as well as mass flow)

At best, it might have matured into a practical longer term design and possibly even proved the radial turbine design had more merit than seen historically. (to the extent that it might have been worth retaining in scaled-up designs, but honestly, the bulk, weight, and use of metal resources makes it unattractive even if it could be practically air-cooled and more durrable than axial counterparts -BMW managed impressive turbine life trials by comparison)

--- One possible exception for this is if a plain, cheap, mild steel radial turbine was feasible, but this would still probably only be useful for short-life engines. (either single use or very regular turbine replacement)

As it was, with strategic metals not being stockpiled at all, producing less resource efficient engines earlier in the war wouldn't have compromised later productivity at all (but detracted from other machines needing those resources OR requiring additional procurement -Finnish Nickel in particular was bottlenecked by transport and not availability prior to very late war when that supply was blocked entirely)



And one other side note, and one that I don't recall often coming up on these sorts of discussions, but: Heinkel might have gained more support from the RLM if he'd put some resources into jet bomber/attack aircraft development early on. (maybe even to the extent of extracting resources from the conventional piston engine bombers then in development -especially the impractical and costly He-177)

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## GregP (Feb 13, 2015)

About all this "diagonal" stuff ... anything that throws the air outward is a centrtufugal compressor. All the "diagonal" does is make it move forward or backward a small bit before the pressure is used. Acceleration OUTWARD is centrifugal. Acceleration INLINE is Axial.


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## GrauGeist (Feb 13, 2015)

Greg, are you actually aware of the unusual configuration of the 109-011?


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## GregP (Feb 13, 2015)

Yes I am. The diagonal compressor is centrifugal as it accelerates the air outward by definition. The slope is there to clear obsatcles, not accelerate the air. Air comes in, diverts outward, and moves inline as a means of diverting it to the intended inlet and bpassing the obstacles. Length is NOT added for no reason. If the inlet were straight back, it would axial. Using radial acceleration makes it centrufugal by nature.

It takes in air in the center and moves it mostly outward and backward a small bit. Might be a bit of a hybrid, but not much. Centrifugal to me and, much more importantly ... to the designer.

I see it as using both centrifugal and axial, much like a Rolls Royce Clyde, but with the centrifugal part as mid-pressure compressor instead of low or high-pressure. It is an intermediate stage that is centrifugal in nature, in front of an axial turbine. Almost all turbines are axial thatb I can think of in aircraft.

I don't consider steam turbines axial since the steam is NOT directed inline; it is directed into the turbine cups instead of straight through the engine, usually at 30° or more angle of entry. That is an engineering judgement on my part ... but I am an engineer after all. To me they work much like paddle-wheeler propulsion on an old riverboat .. inject the high-pressure steam into a cup designed to catch the steam .... not to be an airfoil.


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## wuzak (Feb 13, 2015)

http://www.mep1112.de/img/hes11.jpg

It moves as far back as it does outwards. It was neither a centrifugal or an axial compressor. It was a combination of both. And as good as neither.

The diagonal stage, as shown in the drawing, is between the sing stage low pressure axial compressor and the three stage high pressure axial compressor. It was aweird arrangement that didn't work very well.

Steam turbines are axial, as the flow form stage to stage is axial, though there is a tangential component.

Turbine blades can be impulse or reaction, or a combination of both. 






The ones Greg described are impulse. Steam turbines use a mixture of the types, as do turbines in gas turbines.

As in most gas turbines, the stages for a steam turbine are arranged along the axis of the machine, with the blades getting longer as the steam pressure is reduced.

http://thumbs.dreamstime.com/z/power-generator-steam-turbine-repair-power-plant-process-35001395.jpg

This one shows the steam nozzles (4)

http://2.bp.blogspot.com/-t9StxmIsRXY/UBF8Kd1qIQI/AAAAAAAAAGw/m3wtDDtqyCI/s1600/Picture2.png

This is the spool of a gas turbine generator - the multi stage axial compressor at the front and the multi stage turbine at the rear.

http://www.alstom.com/Global/Group/Resources/Images/Gallery/GT13E2 GasTurbineRotor.jpg

Notice that the turbine section looks much like teh steam urbine - small at the front (where combustion gases enter) and large at the rear.


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## GregP (Feb 13, 2015)

OK, if you say so. Diagrams aren't necessarily the same is real geometry.

Centrifugal to me.


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## wuzak (Feb 13, 2015)

Here is a real one

http://upload.wikimedia.org/wikipedia/commons/8/8d/Heinkel-Hirth_HE_S_011_USAF.jpg


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## GregP (Feb 13, 2015)

Saw it. I'd have to see the helix angle to decide for sure, but it looks like it accelerates the air outward and THEN backward ... making the prime mover centrifugal.

Pics don't always tell the real story and I could easily be wrong here.

Maybe not, though.

Perhaps there IS a real transvestite/hermaphrodite jet engine after all. If so, what do we CALL it?

Centraxial?

Axiafugal?

Seems like a total strange setup since it doesn't exist today as an engine configuration.

On the other hand, both centrifugal and axial engines are VERY popular. I think the centrifugals win out. P&W Canada PT-6 probably has the population over axial in civilian use. Military probably uses more axial.

When I think of centrifugals, I think of the Welland, Derwent, Trent, Clyde, Dart, T31, and PT-6. That encompases MANY aircaft that are not only still flying but also are still in production and still being designed today.

How about the Lancair Evolution? Talk about performance ... it could compete with some early WWII warplanes if armed.


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## tomo pauk (Feb 13, 2015)

Glad to read your very informed posts again, kool kitty.


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## wuzak (Feb 13, 2015)

GregP said:


> Saw it. I'd have to see the helix angle to decide for sure, but it looks like it accelerates the air outward and THEN backward ... making the prime mover centrifugal.



That's whay I showed the diagram, as there weren't many built and not many (one?) survived.

I don't think you can say that the compressor stage accelerates out and then back - it does both at the same time.




GregP said:


> Perhaps there IS a real transvestite/hermaphrodite jet engine after all. If so, what do we CALL it?
> 
> Centraxial?
> 
> Axiafugal?



I believe the stage in question was referred to as a diagonal compressor.




GregP said:


> Seems like a total strange setup since it doesn't exist today as an engine configuration.



Because it didn't work.

Though other engines used a combination of axial and centrifugal compressor stages.




GregP said:


> On the other hand, both centrifugal and axial engines are VERY popular. I think the centrifugals win out. P&W Canada PT-6 probably has the population over axial in civilian use. Military probably uses more axial.



Generally speaking, gas turbines with centrifugal compressors are the smaller power ones. When you get into teh big thrust/hp turbines they will invariably have an axial flow compressor.




GregP said:


> When I think of centrifugals, I think of the Welland, Derwent, Trent, Clyde, Dart, T31, and PT-6. That encompases MANY aircaft that are not only still flying but also are still in production and still being designed today.



The PT-6 and Clyde used both axial and centrifugal compressors in their design.

http://carleton.ca/aerospace/wp-content/uploads/3665745_orig.gif

Only 9 Cydes were built, and only one T31, though it was developed from the J33.

Not many of the newer designs would have centrifugal compressors only, mostly combining that with an axial compressor.




GregP said:


> How about the Lancair Evolution? Talk about performance ... it could compete with some early WWII warplanes if armed.



Huh?


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## nuuumannn (Feb 13, 2015)

> Not many of the newer designs would have centrifugal compressors only, mostly combining that with an axial compressor.



Pretty much on the PT-6. Also, check out the number of types that use it: https://en.wikipedia.org/wiki/Pratt_&_Whitney_Canada_PT6

Many civilian turboprops/turboshaft engines in use today have centrifugal compressors, but axial turbine stages, such as the PW-100 series engines: 

https://en.wikipedia.org/wiki/Pratt_&_Whitney_Canada_PW100


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## kool kitty89 (Feb 14, 2015)

A huge number of turboprop and turboshaft engines use one or more axial stages followed by a single centrifugal one. (Ohan's use of an axial stage BEHIND the centrifugal one in the HeS 8 -and mixed-flow one of the HeS 011 was a bit odd by comparison)

I'm not sure the 'digonal' compressor 'didn't work' but it was complex and costly to manufacture. They're called 'mixed flow' compressors in US engineering terminology and there's a handful of engines that used them. I'm not positive on all the details, but they certainly were not popular or commom. (I'm not sure any saw mass production) Centrifugal designs and axial+centrifugal multi-stage designs continue to be common to this day though.

The XJ49
http://www.enginehistory.org/Packard/jpgs/XJ49 cutaway.jpg
Is one example but I think that design was actually derived from the 109-011 itself, though the mixed-flow impeller seems even more elaborate there. (and there's an added turbofan stage added in that image)


Additionally, Ohain's axial /diffusor/ concept used in the HeS 8 did later become common on some centrifugal based turbine engines and did notably reduce the overall diameter of the engine. 
Off the top of my head, the Saturn MD-120 File:Saturn MD-120 cutaway.jpg - Wikimedia Commons
and Fairchild J44 both did this. (not positive on the latter, but it appears to do such and certainly has an exceptionally small diameter for a centrifugal engine in its thrust class)
Interestignly the SMD-120 uses a diffusor arrangement that looks very similar to the HeS 8's AND uses an additional intake impeller well ahead of the centrifugal stage. (though this appears to be an actual axial compression stage rather than the low-pressure impeller Ohain used)

In fact, I think it's the development of the narrow diameter centrifugal compresspr + axial diffusor arragement that made mixed-flow compressors pretty much worthless. (heavier, MUCH more expensive, and not imparting much added compression or flow on the axial portion of the impller -more like a bulky, expensive, heavy, rotating diffusor)


And on another note, composite construction centrifugal impellers are another way for reducing complex, costly machined single-peice impellers while still allowing more complex and efficient airfoil shapes for the blades/vanes.
The Fairchild J44 is a good example:
http://www.minijets.org/typo3temp/pics/efd82c6f36.jpg
http://www.minijets.org/typo3temp/_processed_/csm_Fairshild_J44_-_03_dfb358239d.jpg
http://www.leteckemotory.cz/motory/j44/validate_j44_1.jpg




Edit:

Also interesting to note that even aside from the axial diffusor, the diameter/bulk of Ohain's engines could have been reduced somewhat if he'd foldered the combustion chamber BEHIND the turbine similar to what Whittle ended up doing.
This seems to be the common feature for commercially developed radial turbine jets, aside from the straight-through configuration.

http://www.gasturbine.pwp.blueyonder.co.uk/ct3201.htm
http://patentimages.storage.googleapis.com/US7055306B2/US07055306-20060606-D00000.png
(the latter example is actually a turbofan configured not too far from the existing axial impeller used by ohain, but with a splitter for bypass air -still smaller than the ducted fan employed on the HeS 8 derivative and not relying on a 2nd turbine stage)

The HeS 3 and 6's 'folding' didn't actually move the combustion chamber to the front of the engine either, rather it allowed a large diffusor section and a portion of the combustion chamber to be moved forward, still requiring a larger diameter for the annular flame tube that ran OUTSIDE the diameter of the compressor/turbine and still nacessitated some added length for the turbine shaft for combustion to take place. (folding the entire combustion chamber to the rear allows for a similarly compact arrangement to mounting it in-between -at least in the case of a typical radial diffusor case- while allowing an even shorter shaft and thus reduced weight/bulk -the reasons Whittle used that configuration even though a straight-through flow configuration was actually simpler with the axial turbine he employed -with a radial turbine the advantages are bigger)


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## kool kitty89 (Apr 22, 2015)

Continued from:
http://www.ww2aircraft.net/forum/aviation/horton-ho-229-vs-vampire-43105-7.html#post1199930







Koopernic said:


> The drop tanks came in as useful in the temporary night fighter versions which sacrificed much of the rear fuel tank to allow a second crew member to be carried. The drop tanks compensated. The original small He 280, with engines in the 1200lb thurst class was judged to small and short ranged. The It was force to use the larger jumo 004 which couldn't fit in the airframe and so the airframe had to be enlarged.


I'm not familiar with this, aside from perhaps having the wings reinforced to mount the heavy Jumo 004As for testing. The story I know of is that Heinkel had been ordered to stop development of the 001 and 006 (HeS 8 and 30) due to BMW and Jumo's class I engines being 'good enough' and ordering Heinkel to focus on a new Class II design.

At that point, Heinkel targeted the 003 and when that was delayed, 004. I have not seen mention of enlarging or increasing fuel capacity of the 280 when mated to the 004, just that it hampered overall handling characteristics and was a less satisfactory installation than on the Me 262. (which had both a larger fuel capacity and larger weapons bay)

With lighter 12-1300 lb thrust engines, the He 280's fuel capacity may have been at least adequate for an interceptor, granted, and the weapons bay should have allowed 2, perhaps 3 MK 108s to be fitted, but I still say adopting the earlier and less troublesome HeS 6 would have accelerated the design considerably. (possibly to the point of being practical for at least pre-production/service testing by 1943, possibly even 1942 -the prototype should have been flying under its own power around a year earlier and without the leaking fuel problems) The heavier use of Krupp stainless steel than the later 004B might have been a problem, but supplies of nickel and and (to lesser extent) chromium were much less problematic early-war, so the emphasis on non-strategic materials was less necessary. (and Heinkel used common tinadur for their high temperature parts, not the exotic alloys the 004A employed -hub/blade-root air cooling slots may have been reasonably effective in improving radial turbine life as well, while hollow blades may have been impractical)


On the HeS 011: Milch's pet 'diagonal' mixed-flow impeller design was targeted rather than a direct follow-on to either the 001 or 006 designs in terms of compressor, combustion chamber, or turbine. In spite of its problems, the 001's compressor section was at least impressive in terms of thrust to frontal area compared to any other war-time centrifugal design, though the axial diffuser used was probably one of the reasons development was slowed in the first place. IMO, an enlarged compressor based on the 001 using the combustion chamber and turbine advances of the 006 seems like it would have been a much safer bet for a class 2 engine in the size range of perhaps the American J-35. (~40 in diameter, close to 2000 lbs and 3000+ lbf thrust with higher compression ratio and better fuel consumption than the 001)

The 006 simply shouldn't have been canceled at all. (ohain's use of sheet metal composite compressor impellers rather than machined single-piece units would still have been an advantage over the 006's reaction blades and more competitive with the 004's construction methods -similarly easier to build than the far more complex British impellers -especially the 2-sided whittle designs)



> The Heinkel Hirth HeS 006 was based on the Jumo 002 designed by Adolf Müller of the Airframe division of Junkers. The engine division *JU*nkers *MO*toren or *jumo* had nothing to do with developing jet engines, it was the RLM that decided that airframe manufacturers shouldn't develop jet engines so Adolf Müller moved to Heinkel and the Austrian Turbo charger espert Franz Anselm started to develop the Jumo 004.


I was of the impression the 002 was a Bramo design with contra-rotating axial compressor, while the Junkers Airframe team's engine never received numbering at all.

Additionally, I was under the impression that the Junkers-Jumo merger fused the perfious Junker's team into the Jumo 004 project in a consulting role at which point roughly half of the Junkers team left the project entirely and migrated to Heinkel (who had not jet Acquired Hirth). I was proposing that there might have been some collaboration between the two teams, and even have the Junkers team migrate to Jumo facilities, but not limiting work to the single Jumo 004 design. (so more like the continued parallel development going on after the BMW-Bramo merger with the contra-rotating axial 002 and Centrifugal BMW engine continuing for some time before efforts shifted entirely towards the 003)
Given the pace the 006 developed at Heinkel-Hirth once the Junkers team finally completed migrating, it seem likely that they could have been a solid year ahead had they continued work at Junkers/Jumo in parallel with the 004. (ie reaching 860 kg bench thrust in late 1941 rather than late 1942)



> Heinkel, an airframe manufacturer, faced been sidelined as well so he brought the company Hirth Motoren at 50% above market value so that he could claim to be an engine manufacturer and continue to develop the jet engine that had in fact been invented by his companies patronage of von Ohain.


Yes, an acquisition facilitated by negotiations with Udet, provided the He 280 fly under Jet power in Spring 1941 (which it managed). 

Heinkel's insistance on developing air-cooled piston engine ducted fan designs at Hirth may have hampered things somewhat, and abandoning the HeS 6 in favor of HeD 8 follow-on cost the potential of a He 280 with different wing/engine mounting configuration from flying in 1940 and possibly accelerating acquisition of Hirth and their engine and compressor/turbine experience by almost a year. 



> Adolf Müller's Jumo 002 that became the Heinkel Hirth HeS 006 was far more capable than the Jumo 004. It used a 50% reaction compressor that was 10%-15% more efficient and required only 5 stages to achieve the same compression ratio as the jumo 004.


Indeed, it was a very attractive design that, had it continued development at Junkers, possibly would have overtaken the Jumo 004 once it was beset with vibration problems. (luck of the draw regarding harmonics of the 006 when adapted to mass producable materials may or may not have favored it, but given it was the 004B that was delayed mostly by vibration and 003 mostly by combustion problems, the more advanced 006 may have been able to reach production first -but Ohain's 1939 HeS 6 developed into a mass-production quality design likely would have been the earliest possible by far)



> As a result it had 50% of the weight for the same thrust. In fact it wasn't beaten in terms of frontal area vs thrust and weight versus thrust by any engine till 1947 and weighed only 390kg versus the 740kg of the jumo.


I'm not sure that claim is quite accurate given the late war Metrovick developments, but it may be referring to engines that actually saw mass production in which case the J34 may being referenced. (the J-30 had an incredibly small diameter, but fuel consumption and thrust/weight were worse than the 006, in theory -on a side note, the J30 would have fit very well in the original He 280 with small size and weight if modest thrust, and perhaps even attractive on the Me 262 if weight was kept down)

It would have been possible to derate the HeS 006 to only 70% and so reduce turbine temperature drastically and still have enough power for the He 280(small). The temperature reduction would have greatly increased turbine life. Sure the fighter had only the range of an Me 109 or He 162 and 3 x 20mm canon but it might have been available earlier despite the more expensive compressor.



> Thus type of compressor was developed further by ABB Cie for the BMW 003C and increased thrust from 800 to 900kg with no changes in turbine conditions. The BMW003D even was expected to reach 1100kg thurst but required a new 2 stage turbine.


Yes, and the 003C was also the only really promising Class II engine. (though a 004 adapted to that compressor type may have been quite compelling ... and quite possibly may have been what happened had the Junkets team not been forced into a consulting role on the existing, more conservative 004 design -ie had the 006 overtaken 004 developments, a follow-on class II design using the experience from both teams may have been forthcoming with better compression ratio than the 006 itself -more stages- and thus likely even better fuel efficiency and thrust likely in the 3000 lbf range to the 003D's 2500~2600)


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## kool kitty89 (Apr 27, 2015)

Continued from: http://www.ww2aircraft.net/forum/av...e-missiles-43188-post1200913.html#post1200913




GrauGeist said:


> The He280 was intended to have the HeS8 as it's powerplants...and the ones tested and demonstrated with the HeS8 performed to all expectations. It was the HeS30 that was supposed to replace the HeS8


This is one of the most informative articles on Ohain's and Heinkel's Jet engine developments that I've found online. ASME DC | Proceedings | GT1999 | Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery | Pioneering Turbojet Developments of Dr. Hans von Ohain â€” From the HeS 1 to the HeS 011 

Ohain's biography (Elegance in Flight) is very informative as well, but in pure technical terms and as a historical digest of events (plus some specific details not present in the biography) it's extremely useful.

When the initial follow-on projects for a jet fighter and jet engines to power it were started in late 1939, it was initially hoped that Adolf Muller's design (claimed to be in an advanced stage of development) would be ready to fly quite soon. This quickly proved to not be the case with major delays in Wagner/Muller's team moving and unpacking from Junkers as well as Muller's exaggerated claims being exposed for what they were. So, before the end of 1939, Ohain started work on a back-up design, the HeS 8, adopting a combustion chamber embedded between the compressor and turbine as well as an axial diffuser and axial flow turbine stators and give vanes in order to keep the diameter within the minimum constraints of the He 280 (or He 180 as it was initially named). Then there's Heinkel and Udet's agreement on acquiring Hirth on the condition the He 280 flew under jet power by spring of 1941.

My point being that at that time, late 1939, the HeS 3/6 and He 178 project having just wound down and the He 180/280 still on the drawing board, the very easily could have taken the conservative approach and compromised to modify the He 280's design to practically mount the existing HeS 6 engines rather than banking on some new unproven developments (be it Wagner's team's axial designs or Ohain's HeS 8 with several fairly radical or at least untried features). The HeS 6 was managing performance in 1939 that the HeS 8 wouldn't until 1942 (and even the HeS 3 was managing performance on par with what the troubled HeS 8 managed in 1941). The He 280 could have flown in 1940 and with at least 18% more thrust (and engines without cowlings due to fuel leaks) and potential an engine that could have matured much closer to being production ready by that point or at least have a greater number of spares. (and move work over to Hirth around a year sooner). 

A scaled up HeS 6 derivative (something closer to the Goblin's thrust ... a Class II RLM engine if you will) would have been worth pursuing as well. That and potentially axial turbines based on Hirth's and Wagners teams work. (and possibly combustion chamber developments progressing with Wagner's team as well -particularly the HeS 30's flame cans)



> The RLM was actually impressed with the He280 and intended to acquire at least 300 units BUT the RLM also got involved with the engine development and insisted on development of the HeS011 instead. It was this meddling that spelled the doom of the He280 as the HeS011 was having serious development problems and cost a great deal of time when the HeS8 was nearly "bug" free and the HeS30 development was coming along behind the HeS8.


Late 1942 when the HeS 8 and HeS 30 were canceled, I'm talking about missed opportunities due to decisions made within Heinkel 3 years earlier. The HeS 8 was never nearly bug free and never produced the anticipated thrust (didn't even exceed the HeS 6's 1939 thrust levels until after the axial compressor stage was added in 1942). Problems with the diffusor, combustion chamber, and turbine (including several problems that were never as severe on the HeS 3 or 6) had not been solved by the time of cancellation and progress had been very sluggish. Given the rate of progress the HeS 30 was making once the team fully settled in (possibly more so after Muller left), it may have been production ready before the HeS 8 ever had its problems worked out.

Aerodynamic problems within the HeS 8 also meant most if not all versions produced were only managing a 2.7:1 compression ratio to the 2.8:1 of its predecessors. (and just over 3:1 for the HeS 30, 004, and 003)

Dumping the HeS 8 made sense, the HeS 30 did not, and pushing the HeS 11 made very little sense and was forced by Milch against the judgement of Heinkel and his engineering teams. IMO, the practical, sensible thing to do (as things stood in mid 1942) would be to continue development of the HeS 30, provide communication/collaboration and exchange of information between the Hirth engineers, Wagner's team, and Ohain's team (which was already the case to some degree), and start work on a class two engine either based directly on the HeS 30's design elements or a larger, single stage centrifugal design that focused on further refining the axial diffusor layout and combined it with the HeS 30's flame can and axial turbine layout. (the combusion chamber and turbine in the HeS 8 were major problems, and the compact diffuser and combustion routing also meant cramped turbine inlet routing -as it was a radial turbine as wide as the compressor impeller, an axial turbine would avoid this problem entirely and allow much greater benefit from the axial diffuser layout, and the axial diffuser would mate extremely well with the flame can arrangement of the HeS 30)

The radial turbine might have been more interesting if applied to Hirth's turbochargers. Those turbines excel in smaller applications and have far better wearing properties as well. (all modern automotive turbochargers use radial turbines)


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## GrauGeist (Apr 27, 2015)

The point I'm making, is that the HeS8 was further along than any other systems and that the He280 was designed for the lighter, smaller engines so it did perform well as designed.

Now, had the He280 continued into production with the HeS8 with the intention to replace those engines with the HeS30 once it was production-worthy, then alot of valuable time would not have been lost.

Now bear in mind that this becomes a "what-if" because, like has been mentioned before, the RLM derailed the HeS30 for the HeS011 and thus the He280 became an opportunity lost.


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## kool kitty89 (Apr 28, 2015)

GrauGeist said:


> The point I'm making, is that the HeS8 was further along than any other systems and that the He280 was designed for the lighter, smaller engines so it did perform well as designed.
> 
> Now, had the He280 continued into production with the HeS8 with the intention to replace those engines with the HeS30 once it was production-worthy, then alot of valuable time would not have been lost.
> 
> Now bear in mind that this becomes a "what-if" because, like has been mentioned before, the RLM derailed the HeS30 for the HeS011 and thus the He280 became an opportunity lost.


No attempts were made to transition the HeS 8 to mass production quality or even make a small production run of it. They were all prototypes and focusing more on attempting to reach the target thrust than manage mass produceability.

They may have proceeded to reach mass production more easily than the 004B did, they likely would have had relatively low TBO times similar to the production 004B and may have required a larger amount of stainless steel. They would have had poorer specific fuel consumption than the 004B (though the lower weight and drag would have saved a lot on fuel efficiency on a complete aircraft performance basis -ie range likely would be significantly worse using the 004s).

From what I understand, Heinkel was using much less exotic alloys in the prototype engine construction than Jumo did on the 004A, much closer to the 004B but with greater portions of stainless and lesser use of mild steel. (percentage of overall weight would certainly have been more stainless steel, though I'm not certain overall material use would be higher) So it's more likely there'd have been a smoother transition from proto to production (at least as long as the mid-war stainless steel supplies held out -much better than the situation in 1944). Plus, vibration problems had consistently slowed development of the 004 prototypes and later B series, this had not been the case on Ohain's engines. (also not one of the major problems with Wagner/Muller's developments -though I believe it was for BMW's 003 development along with their combustion problems)

So yes, had the HeS 8 been pressed into mass production ASAP based on its prototypes of 1942 ... have the design frozen and rushed into service as the 004B bad been two years later, they might have gotten an adequately service ready He 280 into production during 1942. (there were a few other problems with the airframe itself -the twin-fin tail was determined to be less than optimal I believe, but not ones serious enough to totally bar it from being service ready, or at least used for pre-production evaluation A-0 models for operational testing) The ejection seat was not one of the problem areas of the aircraft, and had been used successfully more than once in testing, so that certainly would have been a positive point for pilot survivability.

Shifting to HeS 011 development was just a horrible decision all around.


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## Juha (Apr 28, 2015)

A bit OT but when Jumo 004B-4 entered series production? Most of my sources say in Dec 1944 but Price in one of his newer articles (in International Air Power Review Vol 23)says that during Sept 44 production of the Jumo 004B-4 reached significant levels.


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