Single-engined, turbocharged V-1710 pursuit plane viable?

[gjs238]

Is (or was) a single engine, turbocharged V-1710 powered pursuit plane ever a viable or practical possibility?

The P-39 attempted to, but in the end the turbo was removed.
The P-38 did it with 2 engines.
The P-47 did it with a R-2800.
The P-43 did it with a R-1830.

I'm wondering if the V-1710, while benefitting from the turbo up high, can't supply enough power down low to compensate for the extra weight, especially if you want to have inter/aftercoolers.

 

[tomo pauk]

The XP-60A was stated as able to top 420mph at 29,000 ft, with turboed V-1710 providing 1425 HP from take off till above 25,000 ft. It featured a GE Type B-14 turbo, weighted empty 7806 lbs, service ceiling 34600 ft. Those 420 mph were achieved some time in 1943? - the 1st flight of a turbo-less XP-60A was taken on Nov 11th 1942.

So with B-2 turbo (1941 earlier - like the one used in P-38E and earlier) we can expect some 1150 from sea level to 25kft - that beats, by some 100 HP, the mech-supercharged V-1710 that are commonly found in P-40B/C of the same time frame. Above 15kft, it beats them big time - almost twice power at 25kft.
With B-13 turbo, the output increases to some 1300 HP, military power (15 min), and that's from mid/late 1942. Mech supercharged sibling can beat that, but it must go to WEP (5 min only), with possibility to damage the engine.

Think we can agree that USAAC back in 1941-43 didn't needed another single engined plane that is fine down low, but of low performance above 12-15 kft.

With all this talk about Allison that, DB this, R-2800 something else, the two stage Merlin looks like a true winner indeed.

 

[wuzak]

Yes, I believe a single engine turbocharged V-1710 aircraft was possible.

The P-43 carried the correct size turbo for an Allison (B-series), though the fat fuselage would negate any benefit of fitting the sleeker in-line engine.

A slightly larger P-39, eg the P-63, could have carried a turbo. The turbo could have been mounted where the auxiliary stage was on the P-63 (ie behind the engine).

Maybe a concept along the lines of http://www.flightglobal.com/airspac...olls-royce-merlin-xx-supercharger-cutaway.jpg could have been used, with a pair of smaller turbos feeding the engine supercharger (though the picture shows the turbos directly feeding the engine.

Liquid to air intercoolers would have allowed more flexibility in locating components, and the radiator could have been part of the engine coolant radiator system.

 

[Arossihman]

Was'nt the p-47 supposed to come out as an in-line engine fighter first? I think there was a mock up made of that first version.

 

[davebender]

Junkers and Daimler-Benz chose to stick with superchargers for most V12 engines. RR also chose to stick with superchargers for Merlin and Griffon engines. That suggests superchargers were considered more practical for WWII era fighter aircraft engines. Allison probably reached a similiar conclusion concerning the V-1710 engine.

 

[wuzak]

Junkers and Daimler-Benz chose to stick with superchargers for most V12 engines. RR also chose to stick with superchargers for Merlin and Griffon engines. That suggests superchargers were considered more practical for WWII era fighter aircraft engines. Allison probably reached a similiar conclusion concerning the V-1710 engine.

I believe that the Fw190C was to be powered by a turbocharged Damiler-Benz DB603.

Rolls-Royce tested a turbocharged Condor in the 1920s/1930s, and came to the conclusion that the exhaust thrust was more beneficial at high altitudes than the extra power.

I don't believe Allison came to that conclusion, and the USAAC/F was mostly responsible for pushing turbos.

 

[vikingBerserker]

I could see turbos being good for large aircraft, but I would think the lag would not be great for fighters.

 

[wuzak]

I don't think that lag was a great problem for turbos in aircraft, mainly because the engines tended to operate at constant rpm.

 

[Siegfried]

The problem with turbos for gasoline engines is they required a lot of refractory alloys due to the 850c heat: even the US was inclined to ration these mainly to bombers since turbos offered uneqivical advantages in high altitude cruise efficiency. Diesel is a lot cooler; about 550C.

Turbos are good, work well. Germans had to work hard on hollow aircooled turbines and housings and use cooling techniques using steel alloys (sicromal hollow aircooled, a sort of stainless steel) rather than pure non ferrous alloys such as hastelloy, stelite etc.

The NACA tended to recommend turbo ducting without tight bends with the supercharger housing in the airflow and the USAAF tended to listen, hence the bulk of US superchargers.

A look at a BMW 801TQ shows a different philosophy the so called 'integral' turbocharger with turbine, compressor, intercooler in one tight integral package.

For Germans best to use the metal on a jet engine. A Jumo 213E produced over 200kg thrust, a Jumo 004 at 11000m 380kg.

 

[gjs238]

the US was inclined to ration these mainly to bombers.

Huh?
What about the P-38, P-43 and P-47?
The P-39 was intended to be turbocharged as well.
And there were other developmental turbocharged "Pursuit" aircraft as well.

 

[Siegfried]

True, but the P-51 became the premium and primary product for US fighter production. If the P-51 had had not ever been built and P-47 or a turbo P-40s, or P-38's too its place it likely would have caused material difficulties.

 

[Shortround6]

Arossihman, "Was'nt the p-47 supposed to come out as an in-line engine fighter first? I think there was a mock up made of that first version"

Right on both counts but the V-1710 version DID NOT have a turbo.

DaveBender, "Junkers and Daimler-Benz chose to stick with superchargers for most V12 engines. RR also chose to stick with superchargers for Merlin and Griffon engines. That suggests superchargers were considered more practical for WWII era fighter aircraft engines. Allison probably reached a similiar conclusion concerning the V-1710 engine."

It depends on what you mean by "practical". Allison had reach no such conclusion because Allison wasn't pushing the turbo, The USAAC was along with General Electric. Allison NEVER made a single turbo. General Electric (and subcontractors and licensees) made ALL the turbos used on U.S. service aircraft. Allison may have reached that conclusion privately based on the start of their work on a mechanical two stage system (1938). Engine and supercharger technology made tremendous advances during the WW II era and what was true in one year was not also true the following year.

Assuming a country (or company) can actually build a service quality turbo and do it in numbers that amount to anything, both a lot harder than building a few experimental units, the "practical" aspect depends on the height they are expected to be used at. Under 15,000ft (roughly) they are of no use what so ever and in fact hurt the performance of the aircraft. From 15,000-25,000ft they cross over and begin to show a benefit, depending on the exact type of supercharger you are comparing them to. From 25,000ft on up they show an increasing advantage. They have weight and more importantly, bulk which means a larger aircraft (single engine fighter) overall.

Wuzak, "I believe that the Fw190C was to be powered by a turbocharged Damiler-Benz DB603"

Yes and for an idea of the extra drag that would accompany such an installation please see: http://www.focke-wulf190.com/images/fw190C.jpg

Granted this may be more of a proof of concept installation than a true service installation but but you are going to be hard pressed to install a good turbo installation within the confines of the exiting FW 190 fuselage. In the thin air at 25,000ft and up the extra drag doesn't matter so much but at 15,000ft and under hundreds of extra horsepower are going to be needed to offset the extra drag.

Wuzak, "Rolls-Royce tested a turbocharged Condor in the 1920s/1930s, and came to the conclusion that the exhaust thrust was more beneficial at high altitudes than the extra power"

Exhaust thrust was cheap, it was light, it was compact and on a V-12 it is low drag. Many of these companies did not have unlimited funds for R&D during the 30s. While exhaust thrust works well for high speed level flight it doesn't work so well for climb. the basic formula is P= F(d/t) or thrust horsepower is is equal to the basic thrust (weight of the gases x their exit speed) divided by the inverse (?) of the speed. the slower the plane is moving the less "power" it gets from the same amount of thrust. This means that exhaust thrust is much less useful in a full power climb than in level flight. The turbo adds extra weight (and drag) that hurts climb but does offer "full" power for the climb. Exhaust thrust was also relatively new (NACA first experiments were done an a P-35) and without variable geometry exhaust outlets the exhaust nozzles can only be optimized for ONE flight condition. That is to say they can be set up to give best performance for one speed, altitude and throttle setting. any other flight condition will show varying degrees of lesser performance. If a newer version of the engine comes along the exhaust nozzles have to be changed, in fact if the SAME engine is re-rated for a higher boost (more weight of air and fuel per minute flowing through the nozzles) the exhaust stacks/nozzles have to opened up for the new flow or they 'choke' the engine and cause too much back pressure. This means a lower exit velocity and slightly less "power" when the engine is operated at the original boost setting.

I am not trying to say which was better here, just that exhaust thrust, while very useful, did have some limits of it's own.

 

[tomo pauk]

True, but the P-51 became the premium and primary product for US fighter production. If the P-51 had had not ever been built and P-47 or a turbo P-40s, or P-38's too its place it likely would have caused material difficulties.

English language is not my 1st language, so I humbly ask what the 2nd sentence means?

 

[gjs238]

I think he is suggesting that if there had not been a 2-stage supercharged P-51, P-38's and other turbocharged planes would have been used instead, creating "material difficulties."

I suppose that could be a topic of another thread: If there were no P-38 high altitude reliability issues (or if the issues had been resolved earlier), and P-38's were used to escort USAAC bombers in Europe instead of P-51's, would the US have been able to supply enough turbochargers?

 

[tomo pauk]

18,000+ B-24s, almost 13,000 B-17s produced - that's almost 125,000 turbocharger sets produced. Plus 35,000 for P-47 P-38. 160,000 turbos produced for 4 main airframes. Seems unlikely for me that USA was running out from suitable materials.
Of course, without the Merlin in the picture, two-stage V-1710 gets installed into serial P-51, not just at one or two prototypes. Indeed, it has 10% less power than two-stage Merlin high up, but, in the same time, perhaps 30-40% more than a single-stage V-1710 from P-51A. So we loose what, 10 mph vs. P-51B-K, yet we gain perhaps 20 vs. P-51A - achieving 420-430 mph?
And that's without extra money effort spent on development of the V-1710, now that the money is not spent for Merlins.

 

[MikeGazdik]

Another what if, which could have lessened the demand for turbochargers produced by the U.S.A. Turbo charge the existing P-51A, Allison engined Mustang. Which may have brought the Mustang into service earlier with the 8th AF, and eliminated large amounts of P-38's and maybe P-47's. A Mustang replacing a Thunderbolt would be a 1 for 1 exchange, but it would cut in half the amount needed vs the Lightning.

 

[wuzak]

DaveBender, "Junkers and Daimler-Benz chose to stick with superchargers for most V12 engines. RR also chose to stick with superchargers for Merlin and Griffon engines. That suggests superchargers were considered more practical for WWII era fighter aircraft engines. Allison probably reached a similiar conclusion concerning the V-1710 engine."

It depends on what you mean by "practical". Allison had reach no such conclusion because Allison wasn't pushing the turbo, The USAAC was along with General Electric. Allison NEVER made a single turbo. General Electric (and subcontractors and licensees) made ALL the turbos used on U.S. service aircraft. Allison may have reached that conclusion privately based on the start of their work on a mechanical two stage system (1938). Engine and supercharger technology made tremendous advances during the WW II era and what was true in one year was not also true the following year.

It is also interesting to note that for most applications Allison did not provide exhaust systems - the engine supply ended at exhaust adaptor plates. The airframe manufacturers were responsible for exhaust ejector stubs or exhaust manifolds for turbocharged versions.

 

[davparlr]

Another what if, which could have lessened the demand for turbochargers produced by the U.S.A. Turbo charge the existing P-51A, Allison engined Mustang. Which may have brought the Mustang into service earlier with the 8th AF, and eliminated large amounts of P-38's and maybe P-47's. A Mustang replacing a Thunderbolt would be a 1 for 1 exchange, but it would cut in half the amount needed vs the Lightning.

I think a less problematic solution to the P-51A was to develop a really good supercharger.

 

[Siegfried]

The single stage 2 speed merlins could produce around 1685hp, not worse than the two stage two speed intercooled versions, at low altitude. An adaption of this engine into the P-51A would have taken little time.

 

[Shortround6]

The question is WHEN could the Merlin make 1685hp with a single stage supercharger? It needed at least 18lbs of boost.

And at what altitude? 2250ft is low altitude but it is REALLY low altitude. The Allison's in the P-51s were good for 1490hp/4,300ft/56in MAP with 8:80 gears, 1500hp/5,200ft/52in MAP with 7:48 gears and 1410hp/ 9,500ft/ 57in MAP with 9:60 gears.

Some two speed Merlins were good for 1635HP/2,250ft/ 18lbs boost (around 56in MAP) and 1510hp/9,250ft/18lbs boost.

Granted the 2 speed supercharger was more flexible but increasing the low altitude HP of the P-51 by 10% or less really isn't going to change things that much.

What is more important was the fact that the 2 speed Merlin could give 1120hp at 18,500ft instead of the 1150hp at 11,700ft that the 8:80 geared Allison's did.

But both of these are far below the 1330-1390hp at about 23,000ft that the two stage engines offered to start with.