Online lecture on WW2 engine development

Snowygrouch said:

The trouble with evaporative cooling, is that if you pressurise the whole system it stops it from evaporating in the first place, its extremely difficult to allow it to boil-off at some point after the engine, and still maintain a high pressure inside the engine. There are a few things you can do with flow restrictions and so on to get the benefit without letting the metal temperature in the engine get too high, but its on a knife-edge the whole time, and if the engine power demand suddenly increases, you can get significant boiling happening inside the cylinder head etc, then you`re done for. There is a lot of interest in evaporative cooling today in automotive engines because of the very high cooling possible by allowing boiling (i.e phase change) you can get away with a much lower flow rate of coolant which means smaller pumps etc, but it requires a lot of very clever controls to make it work, which has so far not seen it being adopted in production. Even when it is set up perfectly the metal temps in the head in some typical studies are 10 degrees higher. Which might not sound much, but if you have a high performance engine, it might be enough to cause problems - and thats if it works perfectly. I`ve never used such a system, so I only know what I`ve read on it.

Some modern studies in evaporative cooling for engines are:

http://sro.sussex.ac.uk/id/eprint/63582/1/A REVIEW OF EVAPORATIVE COOLING SYSTEM CONCEPTS.pdf
https://people.bath.ac.uk/enscjb/D22903.pdf

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Thank you

D Deleted member 68059

It appears the problem with the He 100 is that while the pressure is high where it absorbs heat from the engine, the pressure drops off as it's allowed to boil. I'm not sure what pressure was produced at the highest point.

Zipper730 said:

D Deleted member 68059

It appears the problem with the He 100 is that while the pressure is high where it absorbs heat from the engine, the pressure drops off as it's allowed to boil. I'm not sure what pressure was produced at the highest point.

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I dont have engineering reports on it so I dont know what the figures are. I wouldnt say thats a problem specifically with the He 100, what you`re describing is how evaporative cooling works.

Snowygrouch said:

I dont have engineering reports on it so I dont know what the figures are. I wouldnt say thats a problem specifically with the He 100, what you`re describing is how evaporative cooling works.

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I was merely curious if they would be better equipped to produce a good radiator based on their design for pressure.

D Deleted member 68059 : have you ever encountered documents covering the 'classic' cooling for the He 100 during your research for the book, if such thing existed in the 1st place?

tomo pauk said:

D Deleted member 68059 : have you ever encountered documents covering the 'classic' cooling for the He 100 during your research for the book, if such thing existed in the 1st place?

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Very little sadly:

Thank you.

Snowygrouch said:

Very little sadly:

View attachment 603247

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The retractable radiator on the M.S.406 was completely unsatisfactory, and there's a suggestion that the problem was boundary layer issues. Of course, the M.S.406 had that "dip" recess, which seems to have been a big problem.

The He100 didn't have problems that way?

I just watched the webinar, and ordered the book, . It has the potential to be the most informative in my ww2 aviation book collection.
I knew of course about the raw material s shortages of the germans. But i always thought that it was the fuel that limited their boost pressures. But , it seems, according to your presentation that the deciding limiting factor was the lack of strong alloys for the engine components!
Regardless of the very poor management, it seems that with low quality fuel, lack of raw materials germany had no chance to produce a reasonably competitive piston engine fighter after late 1941

dedalos said:

I just watched the webinar, and ordered the book, . It has the potential to be the most informative in my ww2 aviation book collection.
I knew of course about the raw material s shortages of the germans. But i always thought that it was the fuel that limited their boost pressures. But , it seems, according to your presentation that the deciding limiting factor was the lack of strong alloys for the engine components!
Regardless of the very poor management, it seems that with low quality fuel, lack of raw materials germany had no chance to produce a reasonably competitive piston engine fighter after late 1941

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I think your statement about 1941 is probably a reasonably fair assessment. They did manage to get around a lot of the problems in very late model engines
like the Jumo213 which had really superb cooling and oil systems (which compensated), but thats pretty much clutching at straws. It also meant that you have hundreds of "man-years" of development work going into stopping something breaking, whilst Allied engineers were busy making it more reliable or more powerful and so on. So its a double-loss really, burning the candle at both ends. It was an amazing achivement and a tribute to the German designers at the coal-face that they managed to make anything even vaguely workable at all in those conditions. That - as far as I`m concerned - was their real achievement. In many ways a totally different conflict to the one the Allied designers were fighting, so direct comparisons are often almost worthless, unelss the context is understood.

German WWII material shortages had not only a huge effect on their own engineering but some continue to impact us even today.

The engine for the A-4/V-2 was a huge technical achievement but was limited by material shortages. The Germans were short of oil so the fueled the V-2 with alcohol, which they could manufacture from waste and LOX, which they could manufacture using electricity. Their severe shortage of high temperature nickel alloys not only ensured that their jet aircraft would be only a circus sideshow but that the V-2 engine would have to avoid the use of that material as well. So the V-2 turbopump was driven not by burning some of the alcohol fuel and LOX to drive a turbine but by using H2O2 to run the turbine, which is a relatively cold gas reaction, enabling the rocket engine to be built out of lower grade alloys.

When the US and USSR used captured V-2's as a model to develop later rockets both initially used the V-2 approach. Both Sputnik 1 and Explorer 1 as well as the ill fated Vanguard 1 were launched using engines that employed H2O2 to drive the turbine. The US quickly moved on to rocket engines that burn the actual fuel and oxidizer to drive the turbopump but the Soviets did not. The first Soviet ICBM, the SS-6 Sapwood, used H2O2 in the engines and they stayed with that design feature as it was developed into the Vostok, Molniya, and Soyuz vehicles that are still built and launched today. They even had one manned mission blow up on the pad due to leaking H202.

Funny thing. Maybe 15 years ago I was just leaving the office when they told me to come back, the president of the company wanted to talk to me. He asked, "What were the propellants used in the V-2?" I told him alcohol and LOX. He replied, "No way! No one would use LOX in a tactical missile!" I asked him who were the world leaders in cryogenics at the time. He replied, "The Germans." I said, "There you go!" And I thought to myself, "What's the last time someone got called back into the office because the boss wants to know what are the propellants used in the V-2? Maybe 1946?"

You build what you can with what you have, both in terms of knowledge and materials. It's not always the best idea or the latest design. And for some people, once they have something working they leave it alone. The Soviets built the SS-6 engines based on the V-2 technology and the Russians still are. The Sovets built copies of WWII US aircraft radios for decades after the war. The Indians built copies of the 1921 Enfield SMLE rifle for almost 50 years, even though it was decades after their miltary had adopted a modern autoloading rifle.

D Deleted member 68059

Jumo's engineers had planned to use pressurized cooling as of 1938 right? If so, was this solely intended for newer engines (i.e. the Jumo 213) or modifications to older engines (i.e the Jumo 211)?

I'm curious because that seems like a big plus.

MIflyer said:

The Sovets built copies of WWII US aircraft radios for decades after the war. The Indians built copies of the 1921 Enfield SMLE rifle for almost 50 years, even though it was decades after their miltary had adopted a modern autoloading rifle.

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About 25 years ago I worked on five MiG-15 aircraft imported from Poland and my first reaction when I saw the ADF was that's a Bendix MN-26. All the externals looked absolutely identical. Once the lids came off the boxes though it was a whole different ballgame. Instead of the UK/US style vacuum tubes/valves they had totally different Soviet parts - much shorter and about 4 or 5 times the diameter. Naturally the circuit boards were much different too to allow for such tubes to fit. I never saw a circuit diagram for inside the box but I doubt it had much in common with the Bendix unit. The local radio museum were given some and got one working just by swapping all the boxes on their MN-26 display (and using the Bendix racks) so obviously they were backwards compatible as a set and maybe also as individual components.

Several years ago on ebay someone was selling a VHF radio out of a Mig-15. It was rather obviously a copy of an SCR-522.

yes - definitely derived from the SCR-522 but again the internals were very different - less tubes and much larger like with the MN-26.

Zipper730 said:

D Deleted member 68059

Jumo's engineers had planned to use pressurized cooling as of 1938 right? If so, was this solely intended for newer engines (i.e. the Jumo 213) or modifications to older engines (i.e the Jumo 211)?

I'm curious because that seems like a big plus.

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Pressurised cooling systems are a "bit" of a grey area, as, at one time they were basically open to atmosphere, and so, "technically speaking" anything which increases that is "pressurised cooling." However, the DB601E was the first Daimler-Benz engine which at least started down the route of increasing the pressures in a meaningful way (although to a far lower degree than Merlins after the XII), the same is true for Jumo, in their case, the 211 F/J had a totally redesigned cooling system which they referred to as "high pressure (Presswasserkülung)". This was in turn improved for the 213, so its a gradual process rather than a distinct yes/no.

If you dont have it (and it sounds like you either dont, or have not had time to read it all yet) - if you are interested to this degree I really do recommend you buy my book...
it will explain a LOT of things. The image at the bottom is the upper half of page 258 in my book, for example.