Heinkel Jet engines

[johnbr]

Parts of the HeS-011 you can see here
Public.Resource.Org

 

[johnbr]

Heinkel-Hirth 011-A-0 jet engine front cross section of the bullet assembly
Heinkel-Hirth 011-A-0 jet engine left side bullet section.

 

[johnbr]

.Heinkel-Hirth 011-A-0 jet engine cross section showing the front of the auxillary accessory housing and axial compressor
.Heinkel-Hirth 011-A-0 jet engine cross section showing the rear of the auxillary accessory housing and axial compressor.

 

[johnbr]

Heinkel-Hirth 011-A-0 jet engine front cross section of the axial compressor
Front view of Heinkel-Hirth 011-A-0 jet engine second stage diagonal compressor, March 6, 1947.
.Left rear view of Heinkel-Hirth 011-A-0 jet engine second stage diagonal compressor, March 6, 1947

 

[johnbr]

.Rear view of the Heinkel-Hirth 011-A-0 jet engine second stage diagonal compressor, March 6, 1947.
.Left side of the Heinkel-Hirth 011-A-0 jet engine second stage diagonal compressor, March 6, 1947
Heinkel-Hirth 011-A-0 jet engine cross section showing the reduction drive assembly and front for Reidel starter...
Heinkel-Hirth 011-A-0 jet engine cross section showing the reduction drive assembly and rear for Reidel starter.

 

[johnbr]

Heinkel-Hirth 011-A-0 jet engine rear turbine cross section.
.Heinkel-Hirth 011-A-0 jet engine front cross section of the axial compressor

 

[johnbr]

.Heinkel-Hirth 011-A-0 jet engine left side of the combustion and turbine section.
Heinkel-Hirth 011-A-0 jet engine left side of the compressor housing
Heinkel-Hirth 011-A-0 jet engine rear cross section of hte bullet assembly..

 

[johnbr]

.Heinkel-Hirth 011-A-0 jet engine cross section of a dismantled rear bullet assembly, February 24, 1947
Heinkel-Hirth 011-A-0 jet engine center section of a dismantled bullet assembly showing the right side hydraulic piston cylinder, oil scavenge pump and rear turbine bearing support
Heinkel-Hirth 011-A-0 jet engine dismantled and showing the right side of the bullet assembly suppor

 

[johnbr]

Heinkel-Hirth 011-A-0 jet engine dismantled and showing the right side of the bullet assembly support to small this one
.Heinkel-Hirth 011-A-0 jet engine right side of a dismantles bullet assembly showing housing and hydraulis piston rod assembly,
Left side of a Heinkel-Hirth 011-A-0 jet engine showing a dismantled multi-stage compressor,

 

[johnbr]

Heinkel-Hirth 011-A-0 jet engine last three stages, multi stage compressor

 

[johnbr]

Heinkel-Hirth 011-A-0 jet engine dismantled to show the left side of the multi stage compressor thrust bearing support, March 6, 1947
Front view of the Heinkel-Hirth 011-A-0 jet engine showing the second stage disgonal compressor and multi-stage compressor housing, March 6, 1947.

 

[johnbr]

Heinkel-Hirth 011-A-0 jet engine Reidel starter

 

[johnbr]

 

[johnbr]

 

[MiTasol]

The best review of any wartime turbine engine technical features I have seen.
I am giving your post 1 bacon as a reflection on the whole set of posts

 

[johnbr]

Thank you.

 

[kool kitty89]

Video walk-around of the HeS 3B replica cut-away at the Smithsonian Air and Space Museum. (I'm not sure it was there back in 2007 when I visited, but I don't remember it)

It wasn't until seeing this video a few years back that I properly understood the diffuser and combustion chamber arrangements of the HeS 3. It uses an annular combustion chamber of pretty simple and open design, with a splitter at the exit of the radial diffusor section, directing some air downstream into the chamber and most of it forward into the folded, reverse-flow or mixed-flow diffuser section, where it's split up further by a series of sheet metal diffusion/guide vanes, with a small portion tapped off and fed to the burners (combustors). The burners are a series of square flame tubes or square flame jets with vaporized fuel injection nozzles, with vaporizer fuel lines forming a grate-like structure at the exit mouth of the flame tubes. (I assume the square shape was chosen for simplicity of manufacture, as these engines were all made using Heinkel's airframe manufacturing facilities, with an emphasis on cut and formed sheet metal construction over machined parts: also a design feature that made for interesting mass-production and war-time resource conservation potential, but in any event, all those engines were hand-crafted by Heinkel craftsmen) The flame jets would presumably extend well into the very wide/open combustion chamber and would then combine with the air split-off from the compressor earlier on, mixing on its way to the radial inflow turbine guide vanes and the turbine itself. (the use of the radial inflow turbines is one of the more unusual and interesting elements of the engines and probably one of the reasons they worked as well as they did using solid Krupp stainless steel alloy blades: radial inflow turbines are subjected to far lesser stress than axial ones and would tolerate a good deal more abuse as well as less optimized designs or overall conditions)

Those vaporizer type burners were a solution to poor performance with attempted atomized fuel injection systems, inspired by the vaporizer for the flame jet of a gasoline or kerosene blowlamp. Due to the need for warm-up time to reach proper vaporizing conditions, these engines also had to be started with a gasceous fuel, typically hydrogen (at least in early testing), though I suspect propane, methane, dimethyl ether, carbon monoxide (or the carbon monoxide, hydrogen, nitrogen blend of coal-gas or town gas used as domestic heating gas in many regions at the time) would all have worked well enough. Once operating temperature was reached, the engine could be switched over to kerosene or gasoline fuel. Hypothetically, they should have been able to use a volatile, smokeless liquid fuel for start-up, like methanol, diethyl ether, a blend of the two, or ether-alcohol blends (ether-alcohol being a common/popular solvent form of diethyl ether, reducing volatility and largely preventing the formation of explosive peroxides during longer storage periods), but I've seen no reference to such starting fluids being used, or for such being used as primary fuels earlier on when combustion issues were even more serious. (pure Hydrogen gas was used instead to ease design of early prototypes and proofs of concept in the HeS 1 and HeS 2, a choice that likely also would have greatly sped up Frank Whittle's early developments, as would a number of other 'friendlier' fuel choices with higher flame speeds, more volatility, and lower flame temperatures: Whittle was even worse off, as he started with Diesel fuel and later decided on Kerosene)



Origins of German jet power

https://jqmgrdyk.home.xs4all.nl/jetpower/HeS-6-400.jpg

This might be the only image I've seen depicting the HeS 6, or at least the only one I recall off hand.


There seems to be relatively little information on the HeS 6 developed from the HeS3 but apparently not able to be flight tested in the He 178 due to size/weight issues. (the diameter appears to have been similar to the 930 mm of the HeS 3B, but it was quite a bit longer, with broader/taller compressor impeller, larger reverse-flow diffuser section, longer combustion chamber, and broader/longer turbine, plus weighed 420 kg to the 3B's 360) There's mixed information on whether fuel consumption was a major improvement or largely unchanged, but it appears to be approximately 1.6 lb/lbf (or kg/kgf) in any case, similar to the HeS 8 (or at least some early developments of that type), while the HeS 3 may have been as poor as 2.16 lb/lbf.

Thrust of the HeS 6 appears to have been 550 to 590 kgf, with the former being quoted more often, but the latter (or 1,300 lbf explicitly) being cited in some scientific journals or extracts on Jet Engine development.

One in particular: "Pioneering Turbojet Developments of Dr. Hans von Ohain — From the HeS 1 to the HeS 011" comes to mind. Pioneering Turbojet Developments of Dr. Hans von Ohain — From the HeS 1 to the HeS 011 | Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery | GT1999 | Proceedings | ASME DC

There's also a good summary of Ernst Udet's involvement and his support for Heinkel, including the agreement to allow Heinkel to absorb Hirth if the He 280 met its 1941 test flight deadline.



The combustion chamber layout (and possibly the axial diffuser design itself) of the HeS 8 also seemed to prove major problems to combustion stability, general performance, and development time/energy required to make a flight-worthy design and it's always puzzled me a bit as to why the HeS 6 wasn't reconsidered or at least returning to the more known and (apparently) workable diffuser/combustion chamber layout already proven. Being only about 6 inches larger in diameter, it may have even fit acceptably well in underwing mounts on the He 280, unmodified, though the ground clearance obviously would be reduced. Still, compared to the massively greater weight of the Jumo 004A engines (plus 1.5 inch larger diameter) eventually trialed as well, the difference in size seems fairly minor, especially if it had been considered from the start in the He 280's design phase. (for that matter, redesigned wings for mid-mounted engines in the style of the Gloster Meteor also would have worked, and given the many months the He 280 prototype was ready before the first flight-worthy HeS 8 engines, it seems like building a whole new, alternate wing would be quite realistic, too)

Besides all that, the HeS 8 was always intended as an interim substitute for the exceptionally appealing HeS 30, and from that perspective, it seems like falling back on the HeS 6 fit the job much better, especially once difficulties in the HeS 8 began to develop.

On the other hand, the HeS 8 likely did provide valuable experience in developing and refining the axial diffuser arrangement, which could have been quite valuable in a scaled-up second-generation design, but that didn't materialize either for whatever reason. (scaling up the HeS 8 1.26:1 should result in an engine approximately twice as powerful, twice the weight, but with a much better frontal area to thrust ratio and diameter of about 38.4 inches or 976 mm) Though combining the combustion chamber and turbine design of the HeS 30 with the simpler centrifugal compressor of the HeS 8 seems like it would've been a winning combination, including avoiding potential issues of the larger radial turbine consuming too many rare materials and possibly being more difficult to adapt to air cooling. (though the radial design does seem better suited to cooling slots/jets cut into the hub at the base of the blade roots rather than needing the more complicated drawing or folded+welded hollow blades to be effective ... and investigating air cooling methods for the HeS 6 may have been yet another better choice than dealing with the HeS 8's struggles)





That above document also mentions, contrary to some other claims (including wikipedia's) that the centrifugal compressor was built-up from a steel hub and sheet metal aluminum blades, which should have been an appealing route for mass production in war-time, avoiding the high speed steel consumed in precision machining. (designing an impeller suitable for casting would be the other route, and notable one used for the post-war American J44's arguably mixed-flow compressor) The axial inducer fan stage was made of forged aluminum blades, though I'm not sure of the distinction of forging and stamping in this case, but it was not simply formed/curved sheet metal of uniform thickness and was not machined. (also possibly noteworthy was the J44's use of inducer type blading on its compressor being a separate piece with individual blades that mated to the blades of the magnesium alloy casting, allowing simple, straight blades on the cast portion; Ohain's impellers were not completely straight though, but had a slight curve to them on the upper edges receiving intake air) The Whittle and De Havilland (as well as most war-time American and British supercharger impeller designs) had more pronounced curved, angled intake blade tips and overall shaping, plus tended to be made of large, monolithic aluminum forgings, quite complex ones in the case of double-sided impellers as Whittle used. (also notable in the Napier Saber supercharger)

The HeS 011's mixed-flow impeller appears to have been made of machined aluminum, but mass production likely would've switched to something else, possibly a casting or a two-piece casting with additional stamped-blade section. (I'm not sure the sheet metal blading of the earlier Ohain designs would adapt well to the more complex aerodynamic shape of the impeller) The HeS 011's diagonal flow compressor is also not the same type of mixed-flow compressor as the J44 uses (the latter is likely closer to the mixed-flow compressors used on a couple experimental V-1710 supercharger designs) with the J44 using either an axial or diagonal diffuser with fairly heavily curved/shaped centrifugal impeller blades with inducer blades angled sharply enough to arguably count as an axial-centrifugal hybrid stage. (so it goes from axial to centrifugal flow, vs the centrifugal to axial flow in the Heinkel engines: also something present in the HeS 8 with axial stages added after the centrifugal one rather than having one or more axial compressor stages feeding a centrifugal compressor as the final stage as is pretty much the only arrangement used in commercial turbojet and turboshaft designs ... and slightly odd or ironic given the axial inducer stage Ohain had already included: simply developing that into a full axial compressor stage with stator blades flowing into the centrifugal stage would've seemsed straightforward enough, then potentially stacking more axial stages onto the intake of the engine to increase mass flow and compression without increasing the diameter significantly ... for that matter, taking the HeS 30's 5-stage compressor or omitting one or two stages of it, and adding a single centrifugal stage behind that should have made a quite good class-2 engine and been a lot simpler than the HeS 011, though required the precision machined reaction type compressor blading of the HeS 30 ... though I suppose switching to the simpler impulse blading and retaining all 5 stages, plus the centrifugal one also would've worked)

Fairchild J-44s: Minijets (for some reason it's half in french and half english) Some dramatic cost-saving measures there, like using off the shelf burners and stainless steel tubing for the combustion chamber casing.

Packard XJ41 - Wikipedia (one of the few other mixed-flow turbojets of that period, and like the J44, designed for expendable drone or missile use, and the two might even be related, but I haven't seen any reference to such) Also slightly odd the J41 was marginalized, as the thrust was competitive with the J33 and J35 of the period, fuel consumption similar or better, and weight much lower, while diameter was between the two at 48 inches (not listed on wiki). It seems closer in size, weight, and performance to the Derwent V, though possibly simpler and cheaper (especially if it was much like the slightly later J44) but somewhat larger in diameter. (the Derwent V was capable of 4,000 lbf maximum thrust, but was down-rated for operational use in Meteors, though I believe it was used at max RPM for the speed record Meteor flights)





Also, the HeS 6 becomes all the more appealing for use in testing of other jet aircraft developments, not just Heinkel's, and was producing more power in 1939 than the BMW P.3302 (003) was producing a couple years later (and possibly still at the time of being fitted to the Me 262 V1, where those engines failed) and almost as powerful as the 004 up to its mid 1941 endurance tests, though the 004A developed fairly rapidly later that year. The diameter and certainly weight seem to have been small enough to be substitute engines for the Me 262, and potentially low enough in weight to not lead to the wing sweep modification the heavier-than-expected BMW engines caused. (wing loading and stall speed should also have been reduced a good deal on the Me 262, though thrust to weight ratio would be poorer than the 004A, particularly if overreved to 10,000 RPM, but the take-off run might still be reduced due to the lower wing loading, and landing speed would be greatly reduced, plus dead-stick glide landings would have more margin for error, and of course, roll rate would be greatly improved with all that mass on the wings removed) As a possible operational/production design, even with approximate 10-hour turbine life, 1.6 lb/lbf specific fuel consumption and the moderately greater diameter, it seems reasonably appealing with the better thrust to weight ratio and relative ease of producing flight worthy examples. (plus, with the lower weight and nominal thrust, actual fuel consumption or fuel economy in terms of range might have improved over the much heavier Jumo 004 in an aircraft of the Me 262's size)


Also odd is the lack of interest in bomber or recon aircraft with Heinkel. 4 or 6 HeS 6 engines should have worked well for high-speed light or medium bombers and been very appealing for getting RLM attention (or enticing Hitler himself). The Arado 234 also likely would've fared well with 4 HeS 6 engines, being much less underpowered than the 004 installation for similar weight and much lower weight than the 4 003s later tried.

HeS 6 engines also would've made sense on conventionally powered bombers and transport aircraft as booster engines. (small and light enough to make sense in that role, and the relatively short turbine life would be extended if only used for take-off assist and potentially for emergency thrust) And running on diesel, or aviation kerosene compatible with diesel engines, they could also serve alongside Junkers diesel engines and potentially offset the poor ability to use maximum power for combat/emergency conditions with those engines while having a common fuel system using the cheaper, more available diesel or kerosene (or a blend of such). Jet-boosted, turbocharged 2-stroke diesel powered aircraft would be quite interesting. (and apparently turbo-diesels were easier to engineer on the high-temperature turbine materials end due to the lower exhaust temperatures than gasoline counterparts, though the turbine blades of Jumo 207 engines do appear to be hollow for air cooling as well)

File:Jumo 207 im Technikmuseum Hugo Junkers Dessau 2010-08-06 01.jpg - Wikipedia

 

[kool kitty89]

Hmm, also I'm now suspecting the 36.6 (0.93 meter) diameter of the HeS 3b is incorrect, both by comparing the dimensions of the HeS 8 (assuming the compressor and turbine are of similar diameter in both) and more definitively, to the drawing of the HeS 3b that cites a 640 mm diameter 'laufrad' (which appears to refer to the turbine wheel). And taking some measurements of that drawing, it appears the overall diameter should be approximately 1090 mm and not 930.

It's quite possible that 1093 mm is the true figure, and that's where the 93 comes from, as an error.

The "Pioneering Turbojet Developments of Dr. Hans von Ohain — From the HeS 1 to the HeS 011" article doesn't expressly mention diameters either, but frontal areas instead with .68 m^2 and 7.31 square feet given for the HeS 3b (and the diameter can be derived from that by assuming the engine is a perfect circle and using pi*r^2 giving 36.61 inches for the diameter if the more precise 7.31 figure is used). So I suspect the areas were calculated erroneously for the HeS 3 at least, possibly by inputting .930 meters (or perhaps .9301) instead of 1.093 meters at some point and deriving the rest of the errors from there.

I'm also going to assume the HeS 8 frontal area figure of 5.05 square feet is accurate as it matches other citations of approximately 30.5 inches diameter and matches drawings of the HeS 3 or HeS 6 shown to scale with the HeS 8. Though the 5.05 sq ft figure works out to more precisely 30.43 inches, which would round down to 30.4 and not 30.5, so I'm not sure about that. (the less precise .47 square meter figure works out to about 773.58 mm or 30.46 inches, and rounding applied in any number of stages of that would make it even closer to 30.5 inches, particularly if you treat it as .470 square meters with 3 significant figures, then round to 774 mm and end up with 30.47 inches)

The 1.093 meter (43.0 inch) figure is also very close to the same diameter as Whittle's W.1 and W.2 engines, or Derwent or GE developments of the W.1 and W.2 all in the 41.5 to 44 inch range, with the W.1 prototypes cited as 43 inches), but the W.1 used only a 19 inch impeller to the 640 mm (25.2 inch) diameter impeller of the HeS 3b, though the Whittle engine used a double-sided impeller with surface area similar to that of a single-sided 26.9 inch diameter impeller (though the comparison is more complex than that as there's blade length/chord among other issues to consider, plus Whittle's configurations required sufficiently wide space between and around the compressor outlets and combustion chambers to allow intake to the rear side of the compressor). The Halford H.1 Goblin engine by comparison had an overall diameter of approximately 50 inches and impeller of approximately 32 inches diameter. The tip-speed of the HeS 3 at 13,000 RPM would also be fairly similar to the desired maximum operating RPM that Whittle had targeted for the W.1 of 17,750 RPM. (13,000 of the HeS 3b impeller would approximate 17,240 RPM for a 19 inch impeller and the HeS 6's 13,300 would be 17,640, and HeS 8's 13,500 is 17,900 RPM ) However, the W.1 struggled to reach the desired RPM while Ohain's designs apparently ran at full speed by 1939)

The HeS 8, whatever its difficulties were with combustion and its axial defuser, did manage an impressively small diameter relative to its compressor and should have been quite appealing to scale up further, though likely with a switch to an axial turbine and possibly flame cans rather than an annular combustion chamber. Also, had it been made just slightly larger, similar to the 32 inches of the Jumo 004, it probably would've managed to approach the 700 kgf design thrust originally intended. (though the combustion chamber really needed to be longer by the looks of it, and while it would've increased weight and stresses on the rotor shaft, it should have kept the cold section cooler on top of better combustion and homogeneous mixing of the gases past the flame tubes fewer hot spots to develop in the turbine section, plus a greater overall length would generally mean shorter intake and exhaust channels, and fewer losses there, even in nacelles: one of the downsides of both Ohain's earlier and Whittle's reverse-flow/folded arrangement as well)

However, given the trouble and delay in actually getting the HeS 8 working at all, but given the fact the HeS 30's smaller dimensions had already been included for the design specifications of the He 280 (and considerably design work done and construction had already begun), with 43 inch diameter engines, it seems like the best option would have been building an alternate, substitute wing that allowed mid-mounting of the engines, or at least partial submersion in the wing, probably requiring a curved spar, but perhaps not as dramatic as Gloster's fully mid-wing mounting, perhaps one that allowed some 10 inches of the engine's upper half to be submerged in the wing, leaving most of it still below. (closer to the late 1940s Sukhoi Su-11 with its Lyulka TR-1 engine installation)

Additionally, scaling up the existing HeS 6 to something closer to the Halford Goblin engines, suitable for a single-engine aircraft, would be much more reasonable for a large-diameter engine. (the twin-boom arrangement also seems to be appealing in general for short exhaust and ease of engine access or replacement) Though with the radial turbine consuming more stainless steel, a transition to an axial turbine seems likely prior to mass production, either with flame cans or an annular combustion chamber. (again, the turbine and combustion chamber developments of the HeS 30 should have been applied to centrifugal engine developments as well) Meanwhile, the HeS 6 itself might have been a good interim engine to refine as-is for production, at least in the short-term. (and probably more valuable on high speed recon aircraft or bombers than fighters in the early-war period, or as booster engines on those same types, and again also potentially working well alongside Junkers two-stroke diesel engines)

Hmm, for that matter, installing booster engines on the He 177 prototypes and using two, conventional, but less powerful main engines (like BMW 801 or DB 603) along with a number of booster jets for take-off assist and combat speed boost might have allowed for a more practical design than the coupled engine arrangement and heavier, taller landing gear to complement the larger propellers. (though I suppose a push-pull arrangement of smaller engines also would have avoided some of those same problems and allowed use of the more plentiful Jumo 211, but that would seriously alter the center of gravity with engine weight added to the trailing edges of the wings)

OTOH, jet engines would be more problematic for night operations with the exhaust plume rather visible, at least when throttled up. (if only used for take-off and escape/evasion that would be less problematic, and the cruise and bombing operations could be done with the turbine engines at idle, though they likely couldn't be shut down and re-started in flight, or at least not re-started if allowed to cool below operating temperature of the vaporizing burners; re-lighting a flame-out might be possible if action is taken quickly enough, but cold starts would be another matter)



Additionally, it seems Ohain chose the radial inflow turbine for the additional reason of easily matching it to a centrifugal compressor with fluid dynamic and other physics and engineering calculations of properly matching impeller and turbine being much simpler than if one or both was of an axial design.




Edit: apparently Laufrad actually refers to compressor impeller Laufrad (Strömungsmaschine) – Wikipedia based on that at least. And given the compressor is slightly larger in diameter in that drawing, the overall diameter appears closer to 1059 to 1060 mm meters and not 1093, which would be 41.7 inches. (and that wouldn't fit with my typo hypothesis, though I suppose it's possible the HeS 6 was slightly larger at 1093 mm or the error came from somewhere else entirely) The HeS 6 being a slightly greater diameter as well as longer and heavier would certainly have made it even more of a poor fit in the He 178, which was noted for being unable to mount it properly. (information is confusing, but it sounds like the V2 prototype with retractable landing gear was to mount the HeS 6, but never flew, either related to those problems, or due to other issues with malfunctioning landing gear)

The long, curved intake manifold of the He 178 also seems ill suited to such engines, even more so as mass flow increases. (shorter, fuselage mounted side intakes close to the engine's location seem like they'd have worked out much better, probably below and behind the wing) The lack of nose intake also would've made a shift to tricycle landing gear more practical, and the tail arrangement could have been switched to a single-boom, allowing a much shorter jet exhaust pipe to be used. (had there been a V3 prototype built for more extensive testing of jet engines, I imagine that might have been the arrangement, that or a nose intake that split around the sides of the fuselage more like the Gloster G.40 or perhaps the Me P.1101)

 

[Gnomey]

Good stuff!

 

[wuzak]

Kay, German Jet Engine and Gas Turbine Development 1930 - 1945 gives the diameter of the HeS 3b as 930mm with a frontal area of 0.68m².

No diameter is given for the HeS 6, but states this was a development of the 3b. The frontal area of the HeS 6 is given as 0.66m².

The HeS 3b thrust is given as 992lb @ 800km/h (497mph).
The HeS 6 thrust is given as 1,312lb @ 800km/h (497mph).

The weight went up from 360kg in the HeS 3b to 420kg in the HeS6.

The W.1 had a larger diameter because of the arrangement of the combustion chambers, which were larger than that on the HeS 3b and HeS 6.

The HeS 8 was the first jet engine to receive a type number - 109-001, or He 001.

It achieved 1,323lb static thrust, which was less than the 1,544lb thrust @ 800km/h (497mph) which was planned. This must put doubt on the thrust numbers above.

The HeS 8 775mm in diameter and weight 380kg. The pressure ratio was 2.7:1, compared to the Power Jets W.1's 3.8:1, though the W.1 gave less thrust (1,032lb) at lower weight (320kg).

Note that von Ohain only built a centrifugal flow turbojet as an experimental proof of concept (to show that a turbojet could produce thrust). His intention was to move to axial flow designs, but that was blocked, to a degree, buy the RLM. The RLM, in fact, insisted on the diagonal compressor in later Heinkel turbojets. HAd they went with a centrifugal compressor behind teh axial compressor, they may have been more successful.