Superchargers?

[tomo pauk]

What I'm after is this: is there a one-stop on-line reference around? Specifically, I'm interested about supercharger systems used in piston engines, from late 1930s to late 1940s. Preferably, with as small flag-waving as possible

 

[Shortround6]

I am not even sure there is a one stop print reference

You can certainly find books with chapters on supercharger theory and formulas but actual details of individual superchargers seems to be pretty spread out.

The Merlin was pretty prolific as far as superchargers go, with a variety of gear ratios and different sized impellers (at least 4) and at least 3 different inlets on the single stage superchargers alone. Maybe somewhere there are documents with supercharger maps or charts for all the variations.

Same with a number of other companies. The superchargers were modified over time with not only different sized impellers but different numbers of 'blades', the geometry of the inlets changed, the number and shape of the inlet vanes changed and the diffuser changed even for superchargers that kept the same nominal impeller diameter. These changes could affect air flow and efficiency even at the same gear ratios. These records may or may not exist in company records anymore.

 

[tomo pauk]

Guess you're on the money there. I'm a bit more interested in applications, than in theory, but will look at anything decent that I can learn from.

 

[Balljoint]

For what it's worth;

Supercharger Development in the U.S. During the Inter-War Period

 

[tomo pauk]

A worthly reading. Guess I'll try to make a set of articles about supercharger systems of ww2

 

[Shortround6]

This site may have a fair amount of the information you need. Unfortunately it may be scattered through a number of threads.

 

[rinkol]

You can find a number of NACA reports on superchargers and various other aeronautical topics in the NACA archive on the NASA web site (I tried posting a link, but this was forbidden for some reason). In some cases, these are translations of foreign documents.

 

[OldSkeptic]

What I'm after is this: is there a one-stop on-line reference around? Specifically, I'm interested about supercharger systems used in piston engines, from late 1930s to late 1940s. Preferably, with as small flag-waving as possible

Read Stanley Hookers biography "Not much of an Engineer", put quite few equations in there.

 

[tomo pauk]

Thanks for feedback, people.

 

[Shortround6]

The "Flight Magazine" archives : Aviation History - Browse the History of Flight from 1909

Have a number of articles on superchargers although you have to dig for them. You may also have to allow for a bit of bias or war time censorship.

 

[Balljoint]

Apparently NACA was tasked with improving the supercharger performance but found the engine itself was lacking. Just an opinion, but it would seem that the engine may have been unlike their previous experience with radials and turbocharging.

http://history.nasa.gov/SP-4306/ch2.htm

 

[tomo pauk]

I take it you mean this, from the NACA's page:

The Allison engine, however, never met the expectations of the Army Air Forces. The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design. Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight.

Am I the only one that finds this except misleading?

 

[gjs238]

I take it you mean this, from the NACA's page:



Am I the only one that finds this except misleading?

There were several misleading statements in that document.

 

[Balljoint]

Two things struck me as pregnant. I had thought that the Allison supercharger problem was the result of Allison's lack of corporate funds and lack of military concern. But Arnold was apparently on top of the matter and requested the NACA effort. However, the NACA guy Pinkel was a turbo man with good results on the B-17 but at sea as to how to package and drive a supercharged inline engine. It may be reading a bit too much into a few lines, but not at least replicating and adapting the extant Merlin supercharger tech meant the escort P-51 was delayed. It should have been doable.

 

[m37b1]

I take it you mean this, from the NACA's page:



Am I the only one that finds this except misleading?

I'd call it a bit misleading, or at least in need of expanding on. The basic mechanics of the reciprocating assembly of the Allison, were very much the equal of the Merlin. I'd say the combustion chamber was actually superior on the Allison. I'll never take any of the excellence away from the Merlin, but that statement really needs to be backed up with detail.

 

[Shortround6]

Something to remember is that Army power plant division thought that the IV-1430 hyper engine was the "answer" to the liquid cooled engine question for quite some time. Continental simply built bits and pieces to Army specifications. Some of the Army "experts" had a lot of prestige and pride invested in the hyper concept. How much of this transferred over to the NACA I don't know.

 

[tomo pauk]

Fine points there.
We might see that failure of the IV-1430 was never mentioned in the article, yet Arnold's condemning comments about US engines' manufacturers can be read easily:

Arnold blamed the engine companies for the country's dismal aircraft engine situation, but he expected the NACA to correct it. On October 14, 1942 he issued an official directive that the NACA must "do everything practicable to improve the performance of existing engines". The engine companies had failed to provide the nation with "small, light, high performance, highly supercharged engines" suitable for fighter airplanes. Their exclusive focus on large, heavy, air-cooled radial engines reflected their drive for profits at the cost of preparedness. "Our engines were nearly all built as all-purpose engines, with an eye on the world market, and not specifically for fighter aircraft".2 The United States could not enjoy the luxury of fundamental research until the problems of reciprocating engines then in production-the Wright 2600 and 3350, the Pratt Whitney 1830 and 4360, and the Allison V-1710 had been resolved.

In late 1942, both UK and Germany were trying to develop the engines that were neither small, nor light (Sabre, Griffon, Centaurus, DB-603, Jumo 213/222, BMW-802). The USAC/USAF never put much faith before 1942 in two-stage engines either - why all of the sudden accusing the manufacturers for not designing the stuff the main costumer isn't asking for? If there was no USN and P&W cooperation, the P&W 2-stage ('highly supercharged') engines would've likely never existed. Even Wright produced 2-stage variant of the R-2600, though just as prototype (prototypes?).
Contrary to that, USAC/USAF favored turbo, and that does not mean small, and by extension, does not mean light. Insistence for turbo meant that engine-stage compressors were of modest size, too.

As the country's aircraft engine needs intensified during World War II, fundamental engine research took a back seat to trouble-shooting to solve the problems of engines in production. The wartime mission of the new engine laboratory was simple. It had to assist the engine companies to make their engines more powerful and reliable. General Arnold wanted engines that were comparable to the best European models. He ordered Pratt Whitney and Wright Aeronautical to develop fuel injection systems within 12 months to make their engines comparable to the German BMW-801, at that point the world's best aircraft engine.

That is dated as of "3 November 1941".
The R-2800 was at that time (and any other time) a far better engine than BMW-801. In late 1941, the lack of fuel injection was not a thing holding back the R-2600, but a better layout of exhaust, that was solved mid-war. The 801 was somewhat smaller, but R-2600 was far more reliable, despite some Curtiss muddling.

Here is the reply (dated 11 December 1942) from P&W to the Arnold's accusations of 14 October 1942, a footnote from same web site:

Debate over the engine situation in the Power Plants Committee resulted in a stinging response to Arnold's charges by Arthur Nutt of Wright Aeronautical and Leonard S. Hobbs of Pratt Whitney. Hobbs went so far as to insist that a long rebuttal be inserted in the revised minutes of the meeting. The Army Air Forces, he argued, had demanded speed "to the exclusion of other qualities, and as far as he knew, they had obtained it" He felt that there was a basic fallacy in Arnold's assessment of the nation's engine needs. Small engines would never be superior to large ones, and he believed that reliance on "small engines to eventually get the initiative and step above the Germans was simply the continuation of a basic error which could not be corrected by any kind or amount of concentrated laboratory work

 

[Shortround6]

Kind of a case where the right hand didn't know what the left hand was doing. You are not going to build "small" (1200-1400 cu in engines) that are "highly supercharged" without fuel well in advance of the plain 100 octane stuff the US was using in 1940 and into 1941. It is also a bit amusing in that both the Lycoming 1230 and Continental 1430, which had the most Army input (read meddling ) weighed about the same as the Allison and, at least in length, were significantly longer.

 

[OldSkeptic]

Kind of a case where the right hand didn't know what the left hand was doing. You are not going to build "small" (1200-1400 cu in engines) that are "highly supercharged" without fuel well in advance of the plain 100 octane stuff the US was using in 1940 and into 1941. It is also a bit amusing in that both the Lycoming 1230 and Continental 1430, which had the most Army input (read meddling ) weighed about the same as the Allison and, at least in length, were significantly longer.

Thank god for Roll Royce then. It was powerful enough and tough enough (under the great Hives) to ignore that nonsense from idiots.

People, especially Americans (who have a talent for reinventing history), underestimate how important RR was to creating the Merlin Mustangs. The USAAF didn't want it, NA had some vague ideas but were trying to survive against official obstruction from the USAAF (it's only customer really was the British). The Air Ministry didn't want it (especially Portal) , MAP didn't want it, there were official instructions from those to RR to NOT DO IT, Hives ignored them and told it team to go ahead... hence the Merlin Mustang X... which was a god send to Arnald trying to get some, against endless US and UK opposition, a decent LR fighter.

To be fair I think NA then stuffed up because it took nearly another year to produce the P-51B... it would have been much better to just slap Merlins into P-51As and get them out of the door fast (like a Spit V to Spit IX thing). So instead of P-51Bs arriving in late '43 in very small numbers could have been lots of P-51x's in say March/April 43... but hey Govt/corporate politics....heck the Merlin X was superior to the (much) later P-51B....at least it had guns that fired....

Thinking about it it would have been much smarter to ship P-51 shells across to the UK and let RR convert them....since NA took soooo long to produce a fast, but fairly average and buggy plane, with rubbish and unreliable guns and crappy vision (and a tendency to lose tails). RR was far better at that sort of thing and as master of mass production could have (given their clout with the UK Govt, not even Portal would dare to cross swords with RR, though he did quite happily do that with Arnold) converted heaps of them to become superb planes long before they actually did.

 

[tomo pauk]

<gets popcorn>.