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- #41
wuzak
Captain
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.
Centrifugal vs axial compressors in WW2 jets
- Thread starter wuzak
- Start date
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.
delcyros
Tech Sergeant
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.
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.
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
Chief Master Sergeant
- 4,306
- Jun 25, 2013
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.
I believe that the normal English language term for "diagonal" compressor is mixed-flow compressor.
johnbr
2nd Lieutenant
D's any one here have cutaway or more info on the JUMO-004H engine.
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.
-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.
kool kitty89
Senior Master Sergeant
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.
kool kitty89
Senior Master Sergeant
I've been meaning to comment on a bunch of points in this discussion for months now, but kept getting distracted, sooo, here goes.
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)
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)
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)
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)
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)
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
Major
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.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Greg, are you actually aware of the unusual configuration of the 109-011?
GregP
Major
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.
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.
- Thread starter
- #52
wuzak
Captain
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.
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.
GregP
Major
OK, if you say so. Diagrams aren't necessarily the same is real geometry.
Centrifugal to me.
Centrifugal to me.
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- Thread starter
- #54
wuzak
Captain
GregP
Major
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.
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.
- Thread starter
- #57
wuzak
Captain
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.
I believe the stage in question was referred to as a diagonal compressor.
Because it didn't work.
Though other engines used a combination of axial and centrifugal compressor stages.
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.
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.
Huh?
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
kool kitty89
Senior Master Sergeant
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)
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)
Last edited:
kool kitty89
Senior Master Sergeant
Continued from:
http://www.ww2aircraft.net/forum/aviation/horton-ho-229-vs-vampire-43105-7.html#post1199930
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)
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'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.
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.
http://www.ww2aircraft.net/forum/aviation/horton-ho-229-vs-vampire-43105-7.html#post1199930
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)
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)
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.
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)
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.
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)
