How to properly turbo-supercharge the P-39 Airacobra.

phx,

The variation in cylinder head temperature, which can be closely monitored for every cylinder in most modern general aviation aircraft tends to show much less difference in fuel injected engines than in carbureted equivalents. Exhaust gas temperature, which is a much more sensitive indicator of mixture strength can easily vary (harmlessly I hope) more than 80 degrees F in a Lycoming 0-360A4K I regularly fly. (Horizontal carb). The injected equivalent rarely shows 20 deg variation in EGT.

I purposely avoided getting into discussion of cylinder head design, charge stratification or turbulence/swirl, intentional or as is more often the case, inadvertent. In highly supercharged aircraft applications of yesteryear, valve area, heat rejection and positive control of mixture strength were the key topics. Today, at Reno in September, its how much ADI and water spray an engine can tolerate. Yes, they all use carburetors.

Dynasoar
 
The variation in cylinder head temperature, which can be closely monitored for every cylinder in most modern general aviation aircraft tends to show much less difference in fuel injected engines than in carbureted equivalents. Exhaust gas temperature, which is a much more sensitive indicator of mixture strength can easily vary (harmlessly I hope) more than 80 degrees F in a Lycoming 0-360A4K I regularly fly. (Horizontal carb). The injected equivalent rarely shows 20 deg variation in EGT.

I purposely avoided getting into discussion of cylinder head design, charge stratification or turbulence/swirl, intentional or as is more often the case, inadvertent. In highly supercharged aircraft applications of yesteryear, valve area, heat rejection and positive control of mixture strength were the key topics. Today, at Reno in September, its how much ADI and water spray an engine can tolerate. Yes, they all use carburetors.
I'll leave the issues of head design to you, since you obviously understand them better than I do.:)

And, to be clear, that hot wire sensor I mentioned was a notional '40s variant on the '80s Mass Air Flow sensor; my understanding of EGT use is to monitor mixture, not for the FI to control fuel flow.
 
Typically, considering general aviation useage, EGT , whether a carbureted or injected engine, informs the pilot of the extent to which he has manually leaned his engine. The higher the EGT the leaner until, with a carb, lean roughness sets in; with fuel injection providing a much more consistent mixture to each cylinder, the engine, still running smoothly can be leaned to a condition where EGT begins to drop off. Management of lean EGT drop can result in reduced fuel consumption in cruise flight.

Dynasoar
 
Gentlemen,

With much back and forth, I've managed to drag Draconis' excellent second post on this topic into this one. This post triggered my joining the forum, since my resume includes serving as VP Engineering with two groups specializing in the design and manufacture of turbomachinery and compact heat exchangers to control the temperature of relatively high powered electronic systems . This took place during the period from, say 1965 thru 1994, and as a consultant in related fields ever since. Interestingly, After graduation I worked at a Princeton aerospace "think tank" under the mentorship of Prof. Daniel O. Dommasch, who was with Bell Aircraft during their "interest"in the 1946 Thompson trophy race perfomance of a pair of race modified P-39s (One of which won!)

The main difference I wanted to highlight in this thread was the use of a more compact method of intercooling. The air cooled heat exchanger used in all American turbo-supercharged airplanes was an effective but bulky system. Not a problem in a B-17 or B-24 engine nacelle but difficult to fit into a fighter. I probably should have chose another name for this thread to illustrate this idea. But it does show with this system how a turbo-supercharger could have been installed satisfactorily even in a compact plane like a P-39.

Why not use a liquid cooled heat exchanger for fighters? It would be a little more complex as it would require another small radiator with it's own small cowling flap. A pump and tubing will connect the small radiator to the heat exchanger. The heat exchanger is then located in the ducting from the turbo-supercharger just before the carburetors.

The chief advantage of this system is it would be more compact. Especially with the radiator located near as possible to the heat exchanger to reduce the length of the tubing. Considering there is less air ducting used than this type of system maybe no heavier than the air cooled heat exchanger. Because liquid cooling is more efficient then air cooling the size of the radiator and heat exchanger can be made much smaller and still provide effective cooling of the compressed air from the TSC.

In my next post, I'll take up the topic of Draconis' proposed liquid cooled intercooler and offer a self pumped direct air-to-air alternative.

Dynasoar
 
FordCobra.png
This thread is far too technical for me, but I did do a mythical doodle of a turbo-charged direct-injectected Ford GG, just for giggles.
 
Good to see the Ford (In my opinion potentially superior) double overhead cam alternative to the Merlin and Allison in something other than cut down and installed in a tank. Ready to make an Airapython out of what NACA gave us (Airagartersnake).

Dynasoar
 
Anyone interested in the Allison/Merlin topic should look into on-line resources on what has long been, in my opinion the finest liquid cooled aircraft engines ever offered for mass production. It was offered by Ford Motor Company as an alternative to American production of the British Merlin. Using American manufacturing technology (and the much tighter tolerances required for automobile mass production). Using Merlin bore and stroke this engine had the same 1650 cu.in displacement. My understanding is the second engine two cylinder test demonstrator, assembled in late 1940, demonstrated over 175 HP/cylinder on its first full power Dynamometer run. This would point toward 2100HP for 12 cylinders. (Hard to believe,but part of the literature). The usual teething troubles as well as difficulties with the direct cylinder injection system slowed development of the aircraft engine as demand increased for the cut down V8 version, which ultimately was produced in large volume.


Briefly, the cylinder head and valve-porting was pure Leo Goossen (chief engineer -or its equivalent for Harry Miller, Fred Offenhauser, Louie Meyer/Dale Drake et al)- Double overhead cam, four huge valves and free flowing port layout. (He had been involved in other Edsel Ford projects in the past.) The crankcase casting incorporated the cylinder blocks, providing a lighter, but considerably stiffer structure than RR and Allison. Etc- look this engine up for yourselves.

The supercharging, intercooling, integral turbo, aftercooling air to air heat exchanger all look right to me and, with development, as applied to its equivalents, appears ready for a 2500-2600 HP rating.

In an alternate reality, just as North American Aviation produced the P-51 instead of licensing the Curtiss P-40, Ford resources providing NAA with a serious engine, as others pointed out, we might have had a 500MPH Ford Mustang in 1943.

Dynasoar
 
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Briefly, the cylinder head and valve-porting was pure Leo Goossen (chief engineer -or its equivalent for Harry Miller, Fred Offenhauser, Louie Meyer/Dale Drake et al)- Double overhead cam, four huge valves and free flowing port layout. (He had been involved in other Edsel Ford projects in the past.) The crankcase casting incorporated the cylinder blocks, providing a lighter, but considerably stiffer structure than RR and Allison. Etc- look this engine up for yourselves.

The supercharging, intercooling, integral turbo, aftercooling air to air heat exchanger all look right to me and, with development, as applied to its equivalents, appears ready for a 2500-2600 HP rating.

In an alternate reality, just as North American Aviation produced the P-51 instead of licensing the Curtiss P-40, Ford resources providing NAA with a serious engine, as others pointed out, we might have had a 500MPH Ford Mustang in 1943.

Dynasoar


That engine if it would have been as good as you're suggesting would certainly have been used in quite a number of airplanes. What was the name or project designation for this Ford engine?
 
Anyone interested in the Allison/Merlin topic should look into on-line resources on what has long been, in my opinion the finest liquid cooled aircraft engines ever offered for mass production. It was offered by Ford Motor Company as an alternative to American production of the British Merlin. Using American manufacturing technology (and the much tighter tolerances required for automobile mass production). Using Merlin bore and stroke this engine had the same 1650 cu.in displacement. My understanding is the second engine two cylinder test demonstrator, assembled in late 1940, demonstrated over 175 HP/cylinder on its first full power Dynamometer run. This would point toward 2100HP for 12 cylinders. (Hard to believe,but part of the literature). The usual teething troubles as well as difficulties with the direct cylinder injection system slowed development of the aircraft engine as demand increased for the cut down V8 version, which ultimately was produced in large volume.

Hard to believe indeed. Until someone provides the details, like the RPM, manifold pressure etc, I'm afraid that Ford's 1650 cu in engine is something like Bigfoot.


Briefly, the cylinder head and valve-porting was pure Leo Goossen (chief engineer -or its equivalent for Harry Miller, Fred Offenhauser, Louie Meyer/Dale Drake et al)- Double overhead cam, four huge valves and free flowing port layout. (He had been involved in other Edsel Ford projects in the past.) The crankcase casting incorporated the cylinder blocks, providing a lighter, but considerably stiffer structure than RR and Allison. Etc- look this engine up for yourselves.

The supercharging, intercooling, integral turbo, aftercooling air to air heat exchanger all look right to me and, with development, as applied to its equivalents, appears ready for a 2500-2600 HP rating.

In an alternate reality, just as North American Aviation produced the P-51 instead of licensing the Curtiss P-40, Ford resources providing NAA with a serious engine, as others pointed out, we might have had a 500MPH Ford Mustang in 1943.

Dynasoar

Intergal turbo is a no-no until someone, sometimes (like historically Wright did it in late 1943, or the Germans in about same time) invents air cooled blades. Engine has both aftercooling and intercooling? Believeing that Ford 1650 cu in in 1940 (or was it 1942 - sources can't agree with themselves) managed to beat both the turbo and non-turbo R-2800 or 2240 cu in, 3700 rpm Napier Sabre requires giant leap of fait. So does the 500 mph Ford Mustang, in any year.
 
Draconis,

If I had more complete designations for the aircraft variant, I'd have included it. Most information deals with the V8 tank engine variants which were built in thousands. Carbureted and with simplified main bearing details, these engines presented no further development problems. Tank engines, being high priority, went directly into mass production, essentially smothering the V-12 program from both the production capacity and engineering personnel standpoint. As of this instant, use " Ford GG series engines". Will provide more as I find it.
 
Tomo Pauk,

Bigfoot, but with photos, drawings, dynamometer curves and 3/4 size offspring in junkyards all over the world. Will provide more as time permits. In the meantime, enjoy Leo's sideview.

Dynasoar
 
One significant detail for the GG is that it was made, in quantity of, I believe, 3, on production tooling, and did not use forked rods. Further V-12s were constructed as heavy tank engines as well.
 

marathag

Banned
One significant detail for the GG is that it was made, in quantity of, I believe, 3, on production tooling, and did not use forked rods. Further V-12s were constructed as heavy tank engines as well.

Tank version, the GAC, 770HP@2700rpm
Meteor Mk IVA 600HP@2400rpm
 
Anyone interested in the Allison/Merlin topic should look into on-line resources on what has long been, in my opinion the finest liquid cooled aircraft engines ever offered for mass production. It was offered by Ford Motor Company as an alternative to American production of the British Merlin. Using American manufacturing technology (and the much tighter tolerances required for automobile mass production). Using Merlin bore and stroke this engine had the same 1650 cu.in displacement. My understanding is the second engine two cylinder test demonstrator, assembled in late 1940, demonstrated over 175 HP/cylinder on its first full power Dynamometer run. This would point toward 2100HP for 12 cylinders. (Hard to believe,but part of the literature). The usual teething troubles as well as difficulties with the direct cylinder injection system slowed development of the aircraft engine as demand increased for the cut down V8 version, which ultimately was produced in large volume.


Briefly, the cylinder head and valve-porting was pure Leo Goossen (chief engineer -or its equivalent for Harry Miller, Fred Offenhauser, Louie Meyer/Dale Drake et al)- Double overhead cam, four huge valves and free flowing port layout. (He had been involved in other Edsel Ford projects in the past.) The crankcase casting incorporated the cylinder blocks, providing a lighter, but considerably stiffer structure than RR and Allison. Etc- look this engine up for yourselves.

The supercharging, intercooling, integral turbo, aftercooling air to air heat exchanger all look right to me and, with development, as applied to its equivalents, appears ready for a 2500-2600 HP rating.

In an alternate reality, just as North American Aviation produced the P-51 instead of licensing the Curtiss P-40, Ford resources providing NAA with a serious engine, as others pointed out, we might have had a 500MPH Ford Mustang in 1943.

Dynasoar
Wild.:cool: Even if it's not all absolutely true, it's fascinating.

If you find anything else, will you add here, too? (A Ford/Lincoln-licenced Merlin was proposed to replace the Packard.)
 
Gentlemen,

For the moment I forgot that as a founding member of the Aircraft Engine Historical Society I had access to member's archives and an excellent new article on this engine (and an almost endless group of others.. Please go to enginehistory.org and look into the member's section. There may be a nominal initial charge for access to non members. The free section is also huge, but does not seem to have the GG engines. I believe Tomo Pauk will find the data he mentioned.

Events at this end may limit time available to me for a while, but plan to be back.

Best, Dynasoar
 
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Numbers for Tomo et al

From Kimble McCutchon's article on Ford GG Series- In Aviation Historical Society member's website

Takeoff 1800 HP @ 3600 RPM & 60" HgA
Military 1800 HP @ 3600 RPM @32,500 ft, for 15 min
Normal 1500 HP @ 3200 RPM & 54" HgA
Cruise 1350 HP @ 3000 RPM & 48" HgA
Critical altitude 32,500 ft Compression ratio 7.5:1

Dynasoar
 
Numbers for Tomo et al

From Kimble McCutchon's article on Ford GG Series- In Aviation Historical Society member's website

Takeoff 1800 HP @ 3600 RPM & 60" HgA
Military 1800 HP @ 3600 RPM @32,500 ft, for 15 min
Normal 1500 HP @ 3200 RPM & 54" HgA
Cruise 1350 HP @ 3000 RPM & 48" HgA
Critical altitude 32,500 ft Compression ratio 7.5:1

Dynasoar

Do you have the figures for the fuel consumption at those power settings?
 
Numbers for Tomo et al

From Kimble McCutchon's article on Ford GG Series- In Aviation Historical Society member's website

Takeoff 1800 HP @ 3600 RPM & 60" HgA
Military 1800 HP @ 3600 RPM @32,500 ft, for 15 min
Normal 1500 HP @ 3200 RPM & 54" HgA
Cruise 1350 HP @ 3000 RPM & 48" HgA
Critical altitude 32,500 ft Compression ratio 7.5:1

Dynasoar

Hello,
I've joined to the AEHS, and read the article. Some important details need to be listed here. Eg. the 1st GGA engine (ie. a 12 cylinder development of the V2 test mule from 1940) was put on the test stand at late August 1941. Engine used no supercharger during the 1st test phase, that lasted through September, making max 630 HP at 2700 rpm. In November 1941, the GGB engine was on the test stand, that featured a detatchable turbo. The GAA managed 810 HP at 3200 rpm by Dec 1941. Author of the article lists numerous problems, and puts this at the conclusion:
It is clear that the GGB was a long way from production (or even a type test) with myriad problems still unresolved and much detailed testing left to be done. (end of quote)

Basically, the 1800 HP at 32500 ft and other hi-power figures are expected ones, not really attained. With that said - the engine used several innovative features, like the turbine with air-cooled blades, 2-stage turbine-driven compressor, with neat locations for the aftercooler (similar to the Jumo 211J), and DOHC valve train, used only by Mikulin's V12s. The non-usage of engine-driven S/C, at least as initially planed, leaves more power to the prop. Engine also used fuel injection, with it's host of reliability problems experienced.

We can also recall that USArmy-designed 1-clinder test mules worked great, but, once they gave them to Continental and Lycoming so that companies make a full engine, things get very bad, leaving the US fighters to be designed around the privately-developed V-1710 and R-2800, plus the licensed Merlin.
 
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