Germany goes for centrifugal flow turbojet engines?

[MIflyer]

Well, both the USA and Germany had the same kind of government interference. Heinkel wanted to build a jet fighter complete with engines but the Nazi govt told them they were NOT an engine company, so they could not. Lockheed wanted to build a jet fighter complete with engines and the US Govt told them they already had a full plate, so no. Heinkel ended up buying the Hirth company, just so they could say they were an engine company. And of course Whittle struggled under the control of an automobile company and things did not really pick up there until RR traded their Meteor engine factory for Powerjets.

This stifled innovation, all over the place. Today SpaceX builds not only their boosters but the engines; at one time that would have been unacceptable to the US Govt.

 

[tomo pauk]

And of course Whittle struggled under the control of an automobile company and things did not really pick up there until RR traded their Meteor engine factory for Powerjets.

Quoting from the book about the Pegasus jet engine, A.A. Griffith poo-pooed Whittles ideas in the 1930s. Guess hat that was not helping either :\

 

[GrauGeist]

HeS30 does indeed look very impressive on paper. But hard to say they wouldn't have ran into similar issues that subsequently seriously delayed the 003 and 004?

Further, lack of exotic materials might imply a seriously limited lifespan for the hot parts? Unless they had invented something like film cooling?

In any case, considering how promising it was, canceling it was arguably a big mistake.

The HeS30 addressed and improved on the HeS8's issues and was performing reliably by Fall of 1942.
It's development had been delayed several times due to typical infighting, which seemed to be a typical condition within the German aircraft industry, existing at both the design level and with the RLM itself.

The HeS30's design incorporated less exotic materials than the Axials as well as being simpler in construction.

It was also capable of longer operation between refit as well as being capable of rapid RPM changes without a violent reaction, which plagued the 003 and 004 engines.

And again, it operated on Kerosene, which was yet another plus in it's favor.

 

[bf109xxl]

Well, both the USA and Germany had the same kind of government interference. Heinkel wanted to build a jet fighter complete with engines but the Nazi govt told them they were NOT an engine company, so they could not.

What about Junkers?

 

[bf109xxl]

And now a quiz! The winner is the one who finds the centrifugal compressor in the HeS 30.

A special prize to the person who can point out what exactly HeS 8 and HeS 30 have in common - apart from the company abbreviation and the general principle of getting thrust.

 

[MIflyer]

What about Junkers?

Junkers was also an engine company as well as an airframe company. Which was mainly owned by high ranking Nazis.

 

[bf109xxl]

Junkers was also an engine company as well as an airframe company. Which was mainly owned by high ranking Nazis.

Nazis founded Junkers Flugzeug– und Motorenwerke AG in 1936 by fusing Junkers-Motorenbau GmbH and Junkers-Flugzeugwerk AG. I.e. government interference was quite different.

 

[Shortround6]

Hugo was forced out and placed under house arrest.
Competitive bidding under the NAZI's is suspect

 

[Art Medcalf]

Centrifugal compressors and turbines are quite different technologies. By the beginning of WWII, compressor development was quite advanced, turbine not so much. I worked for some years with radial inflow turbines, during the late 80s and early 90s. Even then, we had some serious development problems and our application was probably less demanding that an aircraft turbine engine. Having worked for both USA and German technology companies, my opinion is the corporate and engineering cultures are quite different. The ability to bring new technology to a usable state seemed definitely slower when I worked with and for the Germans. Over-engineering takes more time and does not always produce a better solution.
ArtieBob

 

[nuuumannn]

As an aside, it is also worth noting that both axial and centrifugal compressors are in use in equal numbers to this day and both have found their groove. To say that the centrifugal compressor has been superseded or made redundant or any other equivalent is not facing reality. Axial flow compressors enabled greater power output from thrust producing gas turbines, while centrifugal compressors enabled better efficiencies in smaller applications where torque production and compact installation are the most important elements. Every Pratt & Whitney Canada produced turboprop engine in use today has a centrifugal compressor; one of the most widely used gas turbines in the world is the PT-6, a great wee engine. The PW-100 series engines that power modern turboprop airliners have centrifugal compressors and there are thousands of those in service around the world.

 

[nuuumannn]

In any case, this axial compressor engine is proof that the use of a centrifugal compressor did not offer an unquestionable advantage at that time.

It does when your aircraft are grounded because your engines have a time between overhaul of less than a quarter of that of your opposition. A grounded jet fighter with unserviceable engines is as useless as no jet fighter at all.

 

[MIflyer]

Well, the Germans also failed to incorporate turbosuperchargers in their aircraft, even after the 8th Air Force bombing raids made their shortcomings in high altitude fighters obvious. The reason was not that they lacked the technical skill to develop and mass produce turbos, but because they did not have access to adequate quantities of nickel ore to do so. Turkey's nickel was bought by the Allies and the only other source of nickel was from a mine in far northern Finland that proved to be too difficult to access. 50 years later the Russians were proposing the use of Typhoon nuclear subs to haul nickel from Arctic area mines by going under the ice.

 

[nuuumannn]

Well, the Germans also failed to incorporate turbosuperchargers in their aircraft, even after the 8th Air Force bombing raids made their shortcomings in high altitude fighters obvious. The reason was not that they lacked the technical skill to develop and mass produce turbos, but because they did not have access to adequate quantities of nickel ore to do so. Turkey's nickel was bought by the Allies and the only other source of nickel was from a mine in far northern Finland that proved to be too difficult to access. 50 years later the Russians were proposing the use of Typhoon nuclear subs to haul nickel from Arctic area mines by going under the ice.

Not for a lack of trying. There were several attempts to incorporate turbosuperchargers into existing designs, such as the Fw 190, but as you know, the aircraft really needs to have the device designed into it from the drawing board. Turbosuperchargers were not the only necessity to achieve the performance required, though, the British were achieving the same altitudes with two speed two-stage superchargers, and the Germans never really got those to the same degree of efficiency as the Brits and Americans either. They did incorporate NOS and water meth injection into their engines, which did give them the altitude performance they wanted, not to mention the advent of jet and rocket interceptors, which could easily reach the bomber formations. By then however, their own industry hampered by constant bombing raids and ever increasing Allied air superiority over Europe rendered those ineffective.

 

[z42]

As an aside, it is also worth noting that both axial and centrifugal compressors are in use in equal numbers to this day and both have found their groove. To say that the centrifugal compressor has been superseded or made redundant or any other equivalent is not facing reality. Axial flow compressors enabled greater power output from thrust producing gas turbines, while centrifugal compressors enabled better efficiencies in smaller applications where torque production and compact installation are the most important elements. Every Pratt & Whitney Canada produced turboprop engine in use today has a centrifugal compressor; one of the most widely used gas turbines in the world is the PT-6, a great wee engine. The PW-100 series engines that power modern turboprop airliners have centrifugal compressors and there are thousands of those in service around the world.

Seems many (most?) contemporary turboprop engines tend to have a number of axial stages, followed by a final centrifugal compressor stage.

 

[z42]

Turkey's nickel was bought by the Allies and the only other source of nickel was from a mine in far northern Finland that proved to be too difficult to access.

The nickel mine in Petsamo is right beside a harbor, though a problem is that the entire thing sits right behind the front line, so within comfortable strike range of the Soviet Air Force. I'm not sure actually why Germany was unable to get more nickel from there. Certainly they ought to have the motivation to get convoys through.

Not for a lack of trying. There were several attempts to incorporate turbosuperchargers into existing designs, such as the Fw 190, but as you know, the aircraft really needs to have the device designed into it from the drawing board. Turbosuperchargers were not the only necessity to achieve the performance required, though, the British were achieving the same altitudes with two speed two-stage superchargers, and the Germans never really got those to the same degree of efficiency as the Brits and Americans either. They did incorporate NOS and water meth injection into their engines, which did give them the altitude performance they wanted, not to mention the advent of jet and rocket interceptors, which could easily reach the bomber formations. By then however, their own industry hampered by constant bombing raids and ever increasing Allied air superiority over Europe rendered those ineffective.

Given how huge WWII era turbochargers were (hello P-47!), yeah it would have required an aircraft designed around it, retrofitting to an existing one was never going to work well (some of the German efforts had the exhaust pipes going on the outside of the aircraft from the engine to the turbine in the back!).

But two-stage superchargers were entirely doable, and not managing to get them into widespread use was a huge miss.

 

[bf109xxl]

The ability to bring new technology to a usable state seemed definitely slower when I worked with and for the Germans. Over-engineering takes more time and does not always produce a better solution.

Germans are very prone to excessive perfectionism. This is also a personal experience. But in general, I have the highest regard for the German engineering school.

 

[bf109xxl]

It does when your aircraft are grounded because your engines have a time between overhaul of less than a quarter of that of your opposition. A grounded jet fighter with unserviceable engines is as useless as no jet fighter at all.

At that time, the reliability of axial and centrifugal compressor engines was about the same. The Germans had at least two very promising engines, one of which was brought to quite acceptable perfection after the war, although it could be brought to the same condition during the war.

 

[Shortround6]

Given how huge WWII era turbochargers were (hello P-47!),

Well, we have to consider the design constraints. The P-47 turbo system was designed...
To flow enough air to support 2000hp (or a bit more).
Supply sea level pressure air to the engine at 25,000ft
AND supply the air at an intake temperature of 100 degrees F to the inlet of the carb.

Ask for less air total, ask for a some what less level of supercharging, ask for a slightly higher inlet temperature and you have 3 ways to make the system smaller.
And that doesn't even include asking for a more efficient compressor, which was not that hard to do. GE often just used the 'free' power from the exhaust to get away with a not that good compressor and then mask it with a large intercooler to get the temperature back down.

Don't forget, Republic and P & W did NOT design the turbochargers. The Turbos were supplied by GE, a third company under contract from the US Army.

It is sort of wonder that the US turbos worked as well as they did as there was certainly a lot of room for blaming the other guy. Army actually designed and ordered the turbo controllers (pressure regulators) from a 4th source.

 

[MIflyer]

Given how huge WWII era turbochargers were (hello P-47!), yeah it would have required an aircraft designed around it, retrofitting to an existing one was never going to work well

And it was worst than useless to put a turbo in and not install a intercooler/aftercooler as well. Given that Sir Hooker was the only one to think of using a liquid cooled intercooler there is little doubt that they would have 'effed that up too, just like everyone BUT Hooker. NAA even managed to 'eff that up with the production F-82 despite the rather obvious example of the Merlin Mustang. Odd that no one wondered how the No.1 fighter plane in the world managed to achieve that with the Smallest Displacement Front Line Fighter Engine of the Entire War.

The A6M4 Zero was supposed to have a turbo, as well as the later Wildcats, but ..... ten pounds of feces won't fit in a five pound sack.

The P-47 was derived from a TWO SEAT aircraft. Hence the ability of every P-35 to carry a passenger in relative comfort (and in fact Seversky took his wife with him on demo tours). Hence the ability of the P-43 to accommodate a turbo while the XP-37 went to ridiculous ends.

And of course, if you do install a turbo, not only the rotating machine itself but also the exhaust pipes feeding it need to be made out of the same kind of high temperature material. Germans tried using aluminum spray coating on ordinary steel .....uh, no.

 

[nuuumannn]

At that time, the reliability of axial and centrifugal compressor engines was about the same.

No it wasn't, the British engines were more reliable and were demonstrating greater time between overhaul than the German engines, this is well known. Any report on the Me 262 will tell you that its engines were excessively unreliable.