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wuzak
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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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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.
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.
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.
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.
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.
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)[+] 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.
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)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.
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)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.
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.
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.
Not many of the newer designs would have centrifugal compressors only, mostly combining that with an axial compressor.
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.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 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.The Heinkel Hirth HeS 006 was based on the Jumo 002 designed by Adolf Müller of the Airframe division of Junkers. The engine division JUnkers MOtoren 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.
Yes, an acquisition facilitated by negotiations with Udet, provided the He 280 fly under Jet power in Spring 1941 (which it managed).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.
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)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.
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)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.
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)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.