Germany goes for centrifugal flow turbojet engines?

z42 · Monday at 6:15 AM

Since we've lately had quite a few threads about all the mistakes (or however you wish to characterize it..) the Germans made and what they could (should?) have done better, here's another one: Should they have gone for centrifugal flow turbojet engines instead of axial flow?

Yes, axial flow eventually won out, with much smaller diameter being a big win. (Though to this day many turboprop engines have a number of axial stages followed by a final centrifugal one). But, the centrifugal ones are simpler. So by going for centrifugal designs they could have had something in service sooner?

And while we're at it, target a bit more thrust than the historical Jumo 0004 / BMW 003, enabling single engine fighters from the get-go. Maybe something that looks a bit like the Ta 183, with a nose intake? Performance doesn't have to be as good as the Me 262, even a top speed of 800 km/h should be enough to outclass any prop fighter. More important to have something reasonably reliable in service sooner. And which doesn't flameout when you give the throttle lever a stern look.

tomo pauk · Monday at 7:19 AM

z42 said:
Yes, axial flow eventually won out, with much smaller diameter being a big win. (Though to this day many turboprop engines have a number of axial stages followed by a final centrifugal one). But, the centrifugal ones are simpler. So by going for centrifugal designs they could have had something in service sooner?

Seems also that centrifugal engines were lighter. Being simpler should mean that it is easier to make them en masse (prerequisite being that the air-cooled turbine blades are also in the place).

z42 said:
Should they have gone for centrifugal flow turbojet engines instead of axial flow?

Going with centrifugal flow would've probably meant that they have a less of a rocky start wrt. both development and mass production.

MIflyer · Monday at 8:15 AM

I suspect that centrifugal engine turbine wheels were less sensitive to the type of alloy used, having more material to add strength. On the other hand they likely would have used more material than the individual blades.

bf109xxl · Monday at 8:58 AM

z42 said:
Since we've lately had quite a few threads about all the mistakes (or however you wish to characterize it..) the Germans made and what they could (should?) have done better, here's another one: Should they have gone for centrifugal flow turbojet engines instead of axial flow?

It's not a mistake. It's rather a bad luck. The Germans had a chance to jump over the period of fascination with centrifugal compressors straight into the future - powerful jet engines with axial compressors (RR Avon class). But they could not find a solution to the aerodynamic problems, although they were close - the Jumo 012 could become a breakthrough. In early 1947, German engineers completely redesigned the Jumo 012 (012B) and achieved a very good result. All they had to do was to replace the manager - Scheibe with Brandner - and involve H.-J.Schröder as a leading mathematician. It took about a year and a half, which could have been saved with a rational choice of personnel. And I'm not sure they would have succeeded with centrifugal compressors - they would have needed more time to gain experience.

GrauGeist · Monday at 10:11 AM

Germany had the opportunity to field a true Jet-powered fighter well before the Me262 in the form of the He280, which was powered by centrifugal flow jet engines.
The HeS8 produced enough power to enable the He280 to perform well, though the fighter was intended to have a pair of HeS30 engines.

However, the RLM, once again, screwed itself by interfering with development and ordered Heinkel to develop the HeS011 instead.

Adding to the RLM's idiocy, the HeS30 development, which held a great deal of promise, was set back by infighting and eventual cancellation due to Schelp's favoring the Axials of BMW and Junkers.

*had* the RLM backed the HeS engine development (HeS3/HeS8/HeS30) early on AND not interfered, it is more than likely the HeS30 would have been ready for production sooner than late 1942 and the He280 would have been in the skies two years before the Me262.

z42 · Monday at 1:44 PM

MIflyer said:
I suspect that centrifugal engine turbine wheels were less sensitive to the type of alloy used, having more material to add strength. On the other hand they likely would have used more material than the individual blades.

AFAIU centrifugal flow jet engines all have axial flow turbines, only the compressor is centrifugal. (Now I'm sure someone will prove me wrong by digging up a diagram of some jet engine with a centrifugal turbine )

bf109xxl · Monday at 2:03 PM

z42 said:
AFAIU centrifugal flow jet engines all have axial flow turbines, only the compressor is centrifugal. (Now I'm sure someone will prove me wrong by digging up a diagram of some jet engine with a centrifugal turbine )

SaparotRob · Monday at 2:05 PM

Ask and ye shall receive.

bf109xxl · Monday at 2:08 PM

bf109xxl · Monday at 2:28 PM

z42 said:
Since we've lately had quite a few threads about all the mistakes (or however you wish to characterize it..) the Germans made and what they could (should?) have done better, here's another one: Should they have gone for centrifugal flow turbojet engines instead of axial flow?

Ohain unsuccessfully tried to bring the engine with centrifugal compressor to an acceptable state, but by early 1942 the thrust remained at 550 kg. HeS 10 was designed, but its thrust would not exceed 900 kg, which was also insufficient. Heinkel himself counted on the engine with axial compressor (HeS 30), but this development also failed.
I am very impressed by the number of different projects of the Germans, which at that time was clearly unacceptable.

MIflyer · Monday at 3:54 PM

I do recall an article that said that the Germans concentration on axial flow jet engines was a mistake because it was too early for that type design. I thought that was a bit odd, since axial flow was a better approach in the long run. But after dealing with centrifugal cooling turbines used in aircraft air cycle systems I came to appreciate that while it was not a sure thing with turbines turning at 75,000 RPM, you had a bit more latitude in the turbine wheel design when the centrifugal approach was used. And aside from that, almost every major power had at least some experience with building exhaust driven turbosuperchargers of that design.

GrauGeist · Monday at 4:06 PM

bf109xxl said:
Heinkel himself counted on the engine with axial compressor (HeS 30), but this development also failed.

The HeS30 did not fail, it's thrust-to-weight ratio of 2.20, was unmatched until 1947 and was operating reliably in late summer 1942.

The RLM cancelled the project in favor of the BMW003 and Jumo004.

The HeS011 engine that the RLM did want, was too complex and was not fully developed by war's end.

The HeS30 was a huge missed opportunity. It's weight was half that of the Jumo004 with twice the output and did not require exotic metals.

Germany goes for centrifugal flow turbojet engines?

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