Allision V1710E22 Turbo Compound technology / XP-63H

[R988]

Allison were working on the highly advanced V1710E22 with turbo compound technology, that would have powered the XP-63H, would have put the old Allison at almost 3000hp!

Just found this by accident the other day, really interesting stuff, it's only been in the past 10 years that they have figured out they can use this on trucks, they only stopped researching it because by that stage jets were taking over. I couldn't see any topic on it before so thought I should add it to the knowledge base, the enginehistory.org site is well worth a wider browse as well, some really interesting stories and information on there, especially from the ground crew on early jets.

http://www.scania.co.uk/Trucks/technology/turbocompound/
http://www.holset.co.uk/files/2_5_1_3-turbocompound system.php
http://www.enginehistory.org/v1710tc.htm
http://www.unlimitedexcitement.com/Miss US/Allison V1710 Engine.htm

 

[Twitch]

Ah the Allison. I look back now and puzzle why several land speed racers used it instead of a Merlin whay back in the 1960s. Have to delve into those links and see if there is an answer.

 

[R988]

I think the Allison might have been a bit better at low altitude, also a Merlin needs a supercharger to boost it's power, without it, as on the tank version (called a Meteor?) it wasn't much different in power to the non boosted Allison. I could be wrong though, I'll have to look it up.

 

[KraziKanuK]

The V-1710 had a supercharger. It was a single stage, 2 speed just like on the pre 60 series Merlins. The only Allisons that did not have a superchager were those used on airships.

 

[R988]

So was the two stage, two speed intercooled supercharger the only reason the Merlin was so superior at high altitude to the V1710?

 

[Smokey]

I heard that allegedly the Allison ran smoother than the Merlin and could take more abuse

 

[cheddar cheese]

Likely that there were also a lot more available in surplus after the war.

 

[schwarzpanzer]

Hi R988,

I think the main reason the Merlin and Allison were/are so good is because of the development time spent on them.

This is true of the 'Hemi' engine, enthusistic development over the last, what, half Century? allows immmense outputs for the design...

I have compared (not in amazing detail) the 2 engines and my findings are on another post somewhere (Turbo vs blower thread IIRC?)

I think the Merlin is better at higher altitudes and the Allison better at lower altitude?

I think this may be likely due to different boost vs comp ratios?

I'm not sure though, I believe radials aren't as good as inlines at high altitudes?


The tank version was the Rover Meteor, yes. It wasn't just a de-blowered Merlin you know! It was made from different materials than the Merlin and was, IIRC, tuned for lower revs/de-tuned for higher revs.

A 2-stage blower engine can use a high-altitude blower and a low-altitude blower. A single-stage engine has to make a choice...

BTW: Me and a friend of mine are working on a revolutionary system, very similar Turbo-compounding...


I don't know about the quietness, "it purred" - Me109 test pilot on the Merlin, but the Merlin was a tough little cookie and I think hard to beat (for a water cooled inline).

 

[Gnomey]

Merlin wasn't cooled by water, liquid yes but not water...

"the cooling mixture eventually became 30% glycol as antifreeze in water at +18PSI pressure"

http://www.spitfiresociety.demon.co.uk/engines.htm

 

[schwarzpanzer]

If you want to be absolutely correct, it used indirect air cooling.
(What cools the coolant?? )

Also the presssure was probably a little responsible...This is gonna sound stupid, but was there a water pump? - I thought it'd be obvious.

Water cooled is just kinda slang for liquid cooled, but I take it you already knew that?

 

[helmitsmit]

It is a shame they didn't Turbo-compound more engines, like the Merlin and others like the Napier sabre (which already produced near 3000hp)

It would have been useful on the Griffon 57 used on the Avro Shakleton.

 

[DaveB.inVa]

So was the two stage, two speed intercooled supercharger the only reason the Merlin was so superior at high altitude to the V1710?

Pretty much. To make power youve got to have enough oxygen. With the two speed two stage supercharger the Merlin could get enough at altitude. That alone is just about the biggest reason why the Merlin is so legendary, but few actually realize that is the reason.

 

[syscom3]

The turbocharged Allison maintained its HP at any altitude.

 

[Jabberwocky]

The turbocharged Allison maintained its HP at any altitude.

Not strictly true Sys. While turbosupercharging meant that the Allison retained its power better and in a smooth curve, there was still powerloss above 'critical altitude'.

A P-38Js V-1710-89s could deliver 1550 hp at sea level, 1575 hp at 15,00 feet, 1500 hp at 25,000 feet and 1135 hp at 35000 feet.

Compare this to a Merlin 66, which put out 1,580 hp at sea level, 1,720 hp at 5,000 feet, 15,00hp at 13,000 feet, 1570 hp at 20,000 feet and 1,400 hp at 23,000 feet.

 

[syscom3]

The HP loss's between the two were probably insignificant in terms of performance.

 

[schwarzpanzer]

I suppose the best system would be to use a supercharger for low altitudes and a turbo for high altitudes.

Did any WW2 Aircraft use this system, or was the blower on all the time?

 

[DaveB.inVa]

I truthfully cant think of any turbocharged aircraft in WWII that didnt have a blower that was integral to the engine case.

The P-38 that was mentioned had a turbo feeding the Allisons own case mounted supercharger.

The Wrights and Pratt Whitneys powering bombers were equipped in the same way having a turbo feeding the engine mounted supercharger.

There may have been some that were naturally aspirated but Im sure they were the small type of aircraft like Stinsons.

 

[schwarzpanzer]

That's right, they were used more like a mixer/atomiser than a proper supercharger weren't they?

I think they were driven at crank-speed, but IIRC some were geared-up?

This would make the Merlins Supercharger far superior to the Allisons, if indeed that is the case?

 

[DaveB.inVa]

They were geared to turn faster than crank speed. Your right they do serve to atomize fuel better but they are a true supercharger as well and are there for power.

There were single stage two speed Merlins that were used on some P-40 models alongside some single speed single stage Allisons. Youll find that compared apples to apples both fared about the same.

Also later Allisons were built with a two speed two stage supercharger. These powered the P-82 Twin Mustang and could certainly run with a two speed two stage Merlin.

 

[schwarzpanzer]

It really does depend on whether a radial or inline is used.

I suppose a turbo compounder couldn't be used alongside a turbo back then, the turbine snails being the size they were?

So in that case a supercharger would be almost vital to a turbocompound engine, considering they were mainly desirable for high altitude performance?

If it was me, excluding turbocompounders, I'd have a 2-speed supercharger (low altitude and off!) with at least 2 turbos (1 per bank) on an inline. Would they be too big though, did an inline ever use a similar arrangement at that time?

A radial would probably be better off with a turbo compounder?

Considering turbo's were so big back then, a turbocompounder would be hard to use as well as a turbo?

I'm sure though that some radials used 2 turbo's, or even better a turbo and a turbocompounder?

I've got a Wright Engines 1918-1945 file lying around somewhere...

Sorry for all the questions, don't want to go too off topic if only Allisons are to be discussed?