Development potential of piston engines

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spicmart

Staff Sergeant
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May 11, 2008
I wonder how high were the developement potentials of the various piston engines?
How much power were their projected versions aimed to produce with which cubic capacity?
The Merlin and the Allison had 27 liter and 25 liter respectively and could reach about 2000+ hp. Quite respectable for their size.
The DB 603N had 2800 hp and the Jumo213J had 2700 hp plus greater exhaust thrust than the 603.
Don't know about the Griffons power height.
The Napier Sabre arguably surpassed all in power potential per cubic capacity and weight with projected figures at 4000+.

Can you tell more about these and other engines.
 
The Allison was slightly more than the Merlin. The Merlin was the V-1650 (~1,650 cubic inches - actually 1,649 cubic inches, 27.0L) and the Allison was the V-1710 (~1,710 cubic inches - actually 1,710.6 cubic inches, 28.0L).

The ultimate version of the Merlin, the RM.17SM, was tested at over 2,600hp, flight cleared at 2,380hp and rated at 2,200hp in type testing.

2,600hp was achieved with +36psi boost, >PN150 fuel and ADI, and at 3,150rpm.

2,380hp was achieved with +30psi boost, PN150 fuel, dry, and at 3,300rpm.

2,200hp was achieved with +30psi boost, PN150 fuel, dry and at 3,000rpm.

These were MS/low gear. Rated power for the RM.17SM in FS/high gear was 2,100hp @ ~15,000ft.

The RM.17SM was a 2 stage, 2 speed engine with larger first and second stage impellers. It did not receive a mark number or go into production due to the end of the war and the advent of jets.

The V-1650-9 was also rated at around 2,200hp, PN150 fuel, +30psi boost, 3,000rpm. This was used in the P-51H.

The V-1650-9 was a higher altitude rated engine than the -7 (equivalent to Merlin 66) and the RM.17SM, but the high boost lowered the critical altitude for those settings.

The V-1710 was tested as a turbo-compound, getting powers as much as 3,000hp. The next development for this engine would have been for an air-cooled turbine - the ones used in testing were based on the turbine used in the C series turbosupercharger, which was used in the P-47.

The 100-series Griffons added an extra low gear to be 3 speed, 2 stage engines, with over 2,400hp in the low gear.

The Griffon 57s in the Shackleton were single stage, but managed 2,500hp peak power.

New engines from Rolls-Royce were the Pennine (~2,50 cubic inches, 45L) at 2,800hp for take-off and 2,750hp rated power, and the Eagle 22 (2,817 cubic inches, 46.2L) rated between 3,200hp and 3,500hp. The Pennine was air-cooled, and meant for airliners. The Eagle 22 was similar in concept to the Sabre, but bigger and much heavier (included 2 stage supercharger and dual rotation prop drive).
 
The experimental XR-4360 engines, without integral supercharger, with turbocharger (16 in diameter compressor) and with power-recovery turbine (turbo-compound) were to provide 4300 HP for take-off.
 
Wuzak, thanks for the detailed information. Surprising that the Griffon only peaked at 2400 and 2500 hp. I guess there more projects for it.
Interesting is also how much they could had squeazed out of the Jumo 213 or DB 603 using PN 150 fuel additionally to the MW 50 injection. It should be well above 3000 hp.
 
The question is for how long?
The French built Jumo 213s for a number of years after the war and powered about 2 dozen flying boats with them. Granted I doubt the French were investing much in the way of R&D in the 213 in the late 40s and early 50s in this engine although they did try an experimental 24 cylinder engine and a turbo compound.
The plain Jane 213 was rated at 2300hp for take-off at 3250rpm at 52in (11lbs aprox. 1.7 ata) with water injection and 2100hp dry when running on 100/130 fuel. Perhaps they were limiting the power to preserve overhaul life?
The engine is listed at 2,116lb dry weight while a Griffon 57 is listed at 2100lbs. PN 150 fuel is not magic, it only allows for increased cylinder pressure by delaying detonation. It does not increase the cooling capacity of an engine or increase the strength of the parts.

Piston speed of the Griffon was 3025fpm and BMEP was 322lb/sq in at 25lbs boost
Piston speed of the French 213 was 3521fpm and BMEP was 263lb/sq in at 11lbs boost

Trying to increase the RPM/piston speed of the Griffon by 16-17% could well lead to disaster and trying to increase the BMEP of the 213 22% isn't going to end much better.
 

RR never used water/alcohol injection (a.k.a. ADI) on their engines, apart while making experiments, and apart what Packard did with V-1650. ADI allows for much greater boosts than it would've been possible without it, so rest asured that Griffon with ADI would've beaten 3000 HP mark.
 

SR6,

Did the French versions utilize a single lever prop, mixture, throttle lever like the Fw-190s? Also I think all that keeps the FHM Fw-190D-13 from flying is some missing fuel control components.

Cheers,
Biff
 
Today development of piston (and turbojet) engines involves electronics. Whether this will happen with piston pounders much is more of a market and regulatory than a technical issue. Certainly much of the efficiency increase I saw in jet engines was linked to electronic fuel controls. Just look at the technology developments in auto engines, not all of which are pollution linked.

Development means a lot more than just temporary bursts of high HP, efficiency and reliability are worthy if not sexy goals.
 
Hey Shortround,

Reference post #5. Where did you get the BMEP? The formulas I have found for it are for naturally-aspirated engines only, so I have yet to see a good one for boosted engines. Could you post the formula or maybe a link to an article on it?

I'd be happy to swap Excel files on BMEP and Boost / engines formulas.

Thanks and cheers, - Greg
 

I believe the formula for BMEP is the same for supercharged and non-supercharged engines Greg.
 
The flight engineer on a DC6 has a BMEP gage, I don't recall the units, but it is in effect a torque meter.
 
No formula, figures listed in Wilkinson's "Aircraft Engines of the World".
 
Rolls Royce also developed the Eagle which was similar to the Sabre but with 46Litre (Rapier was 36.7L) and a simplified valve drive system.
 
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