Which country designed the best engines for WWII?

[FLYBOYJ]

Metropolitan-Vickers F.2 never successfully passed a PFTR nor did it ever enter production... its an example of what we call a "failed attempt" to build a axial flow turbojet engine...Germany was clearly ahead in jet propulsion technology by the end of the war.
Below is a comprehensive study conducted by a British author. Pls feast your eyes on it .
http://www.artefactsconsortium.org/....Transport-Lyth,JetEnginesGrPics75ppiWEBF.pdf

Be advised that you're replying to a post from 2008 and to a member who was banned a long time ago.

 

[duplex]

Be advised that you're replying to a post from 2008 and to a member who was banned a long time ago.

I was replying to red admiral's post..I believe he is not banned..The thread is old but still alive

 

[Shortround6]

I was replying to red admiral's post..I believe he is not banned..The thread is old but still alive

Thank you for the link. Although a a bit long it is nowhere near long enough to cover the subject thoroughly and the author seems a bit biased or is pushing a certain view point.
The US did start from behind and the gift of the British jets was an incredible benefit. However no mention is made of the Westinghouse J-30 engine or the GE J-35 Axial engines. Both of which owed little to the British engine/s.
One should also note that the Americans were flying quite a number of different pressurized piston powered air liners in the late 40s eve if the pressure differential wasn't as great as it would be on the jets. In fact the US had lead the way on Pressurized transports.
First being the Boeing 307.

Unfortunately for the British aircraft and jet engines had reached such a state of complication that a few smart people with brains were no longer enough to deliver a working product in a reasonable amount of time. You needed large numbers of not so smart people (but no where near dumb) working under them to sort out the thousands if not tens of thousands of little problems. The Americans had such a work force, the British did not, in large part just due to the size of the populations of both countries.

 

[FLYBOYJ]

I was replying to red admiral's post..I believe he is not banned..The thread is old but still alive

And that it is, just didn't want your efforts to go unanswered, but do appreciate you reviving this thread.

 

[Dan Fahey]

The key powers US, Germany, Japan and England all made great engines.
Speaking for liquid cooled Germany, Allison and Merlin in that order.
US or Germans Liquid cooled engines were just more rugged.
Merlin was called the Watchmakers Engine..it performed well because of a great Supercharger system that Allison never quite caught up.
Germany had the variable Supercharger which was a huge asset.

Radials ..everyone had a good radial.

 

[Shortround6]

The key powers US, Germany, Japan and England all made great engines.
Speaking for liquid cooled Germany, Allison and Merlin in that order.
US or Germans Liquid cooled engines were just more rugged.
Merlin was called the Watchmakers Engine..it performed well because of a great Supercharger system that Allison never quite caught up.
Germany had the variable Supercharger which was a huge asset.

Radials ..everyone had a good radial.

Would you care to post the time/s to overhaul for the German Liquid cooled engines?
Or other evidence of how rugged they were?

The variable supercharger (actually variable drive) was not quite the huge asset it is made out to be. It was variable between a high and low limit that wasn't that much different than some two speed superchargers (although it did eliminate the "notch") and if the compressor is crap it doesn't matter what kind of drive mechanism you use. The 109 for most of it's career had good altitude performance because they stuck a big engine in a small plane. Not because the engine was a technological marvel.

 

[Juha2]

Metropolitan-Vickers F.2 never successfully passed a PFTR nor did it ever enter production... its an example of what we call a "failed attempt" to build a axial flow turbojet engine...

In fact M-V F.2 was developed into 3,500 lb F.2/4 Beryl, first ran Jan 1945 and passed a 100-hour type test that year. Built in small numbers, IIRC around 30, and in the end produced 4,000 lb thrust. Powered Saunders-Roe S.R./A.1 flying boat fighter prototypes.

Juha

 

[mad_max]

Mike Nixon of Vintage V-12s has told me the DB 601/605 has very good internals. The biggest problem was feeding them NO2 and over-boosting them to get powers that weren't conductive to long engine life. You can only push powers so high until something breaks and they needed more power without the time to strengthen the engine sufficiently.

 

[Venturi]

The overhauls / TBOs of the db60x series were on the order of 100-150hrs. Whereas the overhauls of late series Allisions were 700hrs in combat zones, in training, a thousand hours or more. Merlins were somewhere in between, about 400hrs.

The Db601/5 is a large displacement engine which when ran at high power levels was very stressed. It weighs about the same as a Allison or Merlin, and is 33L or 35L displacement, as compared to the Allison or Merlin which is 27L displacement.

A lot of the difficulty's with high power levels have to do with the fuel octane rating the engine is designed for. As the surface area of the piston tops increase, and the Db601 and especially the 605 has bigger pistons than the Allison or Merlin, the difficulty with an even fuel air mix becomes greater. Resulting in detonation more easily as lean/hot spots develop across the piston top. DB mitigated this somewhat with direct fuel injection, increasing fuel/air homogenicity, but still had issues in their pushing of the cylinder compression to the max possible with 87oct fuel - resulting in pistons with holes in them, burnt valves, and compression losses of all kinds.

Really, a lot of attention has been paid to the variable supercharger on the db601/5, but the real design genius was in the direct fuel injection and RPM/boost matching system. And that cognitive error goes back even to the wartime years. The variable supercharger was simply effective, cheap, and light. Nothing too special about it. As SR says, the 109 was a very small airplane with a very big engine, and that's where it got its performance.

 

[Venturi]

The maximum emergency time at power with these systems engaged was actually quite a bit LONGER than when at 1.42ata, which remained through the war the maximum boost level permitted without MW50 or other system like GM-2.

Again, this is because the limiting factor was not structural, but rather chemical - read: detonation - as the engine was simply designed for 87oct fuel (excepting very minor variants) and the design pushed the limitations of what that fuel could provide in the way of maximum permissible supercharger boost. As it approached the absolute maximum permissible boost, the safety margin between normal combustion and detonation became razor thin. This was far less of an issue for late (or even mid) war allied aircraft which had the advantage of higher octane fuel (and the more clumsily operated but more adjustable fuel mixture and prop control systems which were not tailored for a specific fuel octane).

Mike Nixon of Vintage V-12s has told me the DB 601/605 has very good internals. The biggest problem was feeding them NO2 and over-boosting them to get powers that weren't conductive to long engine life. You can only push powers so high until something breaks and they needed more power without the time to strengthen the engine sufficiently.

 

[Smokey Stover]

For me this is an easy one and i can even whittle it down to just two main types....
1) The British/US Rolls Royce PV12/Packard 1650 "Merlin" inlines.
2) The Pratt & Whitney R2800 radial.

Honourable mentions include Daimler Benz DB series. The Bristol Hercules & Centaurus radials. The Junkers Jumo 200 series inline. BMW radial & Napier Sabre inlines. Curtis inline & Wright Cyclone radial. Maybe some Nakajima's but they were woefully underpowered.....
I'd mention Russia but they were all just copies of copies of copies and not even very good at that.

 

[Smokey Stover]

When the Sabre was ordered the Air Ministry (not gifted with our hindsight) thought that there was more at stake than the technical promise of the engine itself. THE fundamental tenet of the Air Ministry's selection policy was that quality could only be maintained by competition between different firms. The contraction of the aero engine industry in the 1930s was, as shown above, a source of considerable official anxiety.
We do have an inkling on the effect of the Ministry's renewed interest in the Sabre on Rolls Royce. On 20th November 1939, following the decision to build the factory for Sabre production at Liverpool, Hives wrote the following memorandum.

"We allowed Napier's to come into the aero-engine business after the war and build up a most lucrative business which should have been ours. If Napier's had really been awake we might have been suffering from that error today. Having now established ourselves as one of the two top aero-engine producers in the country, we have got to hang on to that position, even if it costs us money."

He was clearly suspicious of the opportunity afforded to a competitor by this second war.
In 1939 the Vulture was still seen as the engine most likely to counter the perceived threat from Napier, Hives said as much to the AMDP in March of that year, but he definitely had reservations about it. It was at this time that a much simpler engine, based on the 'R' Type, what we would know as the Griffon, started serious development. It seems that Hives colluded with Supermarine (who were supposed to lose the Spitfire and start manufacturing the Beaufighter in 1941) to make it clear to the Air Ministry that the Griffon, not the Vulture, could extend the life of existing types. It was in both companies interest to extend the life of the Spitfire, in the case of Supermarine they argued that it would prevent a time consuming and costly changeover of production from one type to another, and in the case of Rolls Royce the challenge of an alternative Sabre engined fighter might be dispelled. By October 1939 the two companies had come up with a system for installing the Griffon in the Spitfire. The companies argued that this would produce a fighter equal in performance to the Typhoon , but lighter and with a lower powered engine. The smaller engine and lighter airframe would also be more economical in terms of man hours and material.
At the end of 1939, under persuasion by Rolls Royce and Supermarine, who had their own vested interests, Freeman would write to the Secretary of State that

"in wartime when it is difficult to introduce new types of aircraft without a great falling off of production, it is essential that we improve the performance of the types which are already being produced."

The order for the Sabre engine led directly to the development of the Griffon, perhaps even more importantly to radical development of the Merlin, and to the Spitfire remaining the RAF's premier fighter for several more years. None of this was intended, but seemingly innocuous causes can have drastic effects.
I would argue that it was neither the Vulture, nor the Griffon that proved Rolls Royce's answer to the Sabre, it was the Merlin, but largely because of Napier's woes with the Sabre.
It is also clear that whilst a certain degree of cooperation between companies was inevitable in the national interest, commercial considerations were never ignored.

Cheers

Steve

I think your quote about Sabre engines is a little harsh. Yes early Napier's were very unpredictable and suffered a litany of problems especially with fire during engine start, and a few other minor gremlins that were concerning the RAF. But at that time Britain had to work with what it had, and later Sabre variants (Especially Tempest V's powered by the Sabre ll) Had almost all problems eradicated, and many Luftwaffe pilots stated the Tempest was one of, if not the best fighter the allies possessed towards the end of the war. Further development of the British H-24-cylinder, liquid-cooled, sleeve valve, piston aero engine, designed by Major Frank Halford and built by D. Napier & Son, would surely have given the Merlin or Griffon serious consideration and respect. As for Britain having just a few types of modern powerful aero engines i think is irrelevant. From inline to radials, Britain could hold its own with any other country during ww2. Plus a lot of people forgey the Napier Sabre H-24 Mkl was first tested way back in 1939.

 

[Deleted member 68059]

[QUOTE="As the surface area of the piston tops increase, and the Db601 and especially the 605 has bigger pistons than the Allison or Merlin, the difficulty with an even fuel air mix becomes greater. Resulting in detonation more easily as lean/hot spots develop across the piston top. DB mitigated this somewhat with direct fuel injection, increasing fuel/air homogenicity, but still had issues in their pushing of the cylinder compression to the max possible with 87oct fuel - resulting in pistons with holes in them, burnt valves, and compression losses of all kinds.[/QUOTE]

References please.

 

[Venturi]

Look at the Luftwaffe technical notes about maximum permissible boost on the Db605 and the 1.3ata limit (instead of 1.42) until piston tops could be reinforced, for starters. As pistons were being burned through. They did eventually solve this but I would note that the solution was simply to add more mass to the top of the pistons...

 

[Deleted member 68059]

Look at the Luftwaffe technical notes about maximum permissible boost on the Db605 and the 1.3ata limit (instead of 1.42) until piston tops could be reinforced, for starters. As pistons were being burned through. They did eventually solve this but I would note that the solution was simply to add more mass to the top of the pistons...

The thicker pistons just meant it took a few more hours for the detonation to eat through the piston crowns.

 

[Venturi]

Exactly,
But also more mass also means the piston sinks heat better, theoretically
Tradeoff being increase in reciprocating mass and the stress is equal to the square of the engine speed times the mass being reciprocated...

 

[Deleted member 68059]

Exactly what ?

Hardly a solution then is it ? - and also totally unrelated to the piston crown area being the case, which was your proposition - for which you`ve provided no evidence.

 

[Venturi]

As the piston creates a vacuum it generates vortices of distubed air at the top of it in the low pressure zone, increases in diameter of the piston results in bigger low pressure area, means increases in inhomogenicity, well known general fact in engine building. Direct injection increases fuel air homogenization as less volume to traverse before combustion area (you don't get lean cylinders etc) which is another beneficial effect and helps prevent detonation.

Ok go talk to an engine builder if you're more interested in specifics on general principles. Sorry not every piece of knowledge is able to be historically sourced, except maybe extrapolated from texts in engine design

 

[pbehn]

The thicker pistons just meant it took a few more hours for the detonation to eat through the piston crowns.

I burned through many pistons on two strokes, I know it is different technology but when the process starts it takes seconds or minutes not hours.

 

[Venturi]

Yes agreed. I was responding in the affirmative that it was the process responsible.