V-1710 turbocharged plane w/turbo mounted in rear ala P43/P47

[Colin1]

Looking over all of the previous posts, what I see is the P-51 being quite possibly the best candidate...

...and in being so would deprive the Allies of its premier long-range escort, unless you've got somewhere else in mind for the aft fuel cell. It would become pretty ordinary from zero feet up to turbo kick-in altitude. I don't think a turbocharger would have enhanced the P-51 in any way, it would simply become a high-altitude, medium range fighter.

In many respects, only a little better than the P-39.

 

[riacrato]

I don't think the P-51 lends itself that well for an aft-fuselage turbo. Where are you going to route all the pipes along (sorry for that word). It's too slim.

In fact I doubt you can effectively retrofit any airframe with a supercharger. It has to be purposely built for that.

 

[gjs238]

In fact I doubt you can effectively retrofit any airframe with a supercharger. It has to be purposely built for that.

Not V-1710's, but one-off versions of Corsair and Hellcat had turbos:
- Corsair FG-3
- Hellcat XF6F-2

 

[davebender]

If the U.S. Army Air Corps adopts the P-51 early (1941) then just build the historical version powered by a Packard built RR Merlin engine. Replacing the supercharged Merlin engine with a turbocharged Allison engine will likely result in a worse aircraft that enters service late and with a problem plagued engine.

 

[MikeGazdik]

1) I am not saying it would be better than the Mustang we know, in fact it surely would not. I'm just "playing" the game and from what I see it seems to be the best airframe.

2) Riacrato > In my post I stated the fuselage would have to be widened and deepened, I agree it is too slim.

 

[drgondog]

What made the Mustang the airplane it became was a.) extremely low drag and b.) two stage supercharger Merlin

It probably couldn't sustain a width change to the lines and retain the low drag. There was a very small amount of room under the floorboard above the wing after the wing was dropped by 7 inches to accomodate the altered cowling design required for the larger Merlin installation.. but a max of perhaps 5" in ducting heighth could be accomodated under the floor and I have no idea what the horizontal clearance would be due to control cables from Rudder pedals and stick.

 

[Demetrious]

If the U.S. Army Air Corps adopts the P-51 early (1941) then just build the historical version powered by a Packard built RR Merlin engine. Replacing the supercharged Merlin engine with a turbocharged Allison engine will likely result in a worse aircraft that enters service late and with a problem plagued engine.

This begs the question- why are we turbocharging this theoretical Allison-based plane, rather then supercharging it? Were turbochargers cheaper? Turbocharging requires extensive ductwork to get the exhaust gasses that power it back behind the pilot to the turbocharger and yet more ductwork to get the forced air flow from a theoretical belly scoop back up front. A supercharger, by contrast, is powered by the engine itself so you can pretty much just ram her in there (gross simplification, of course, but still.)

Were turbos substantially cheaper then the always-expensive superchargers?

 

[davebender]

I think the opposite is true. Turbocharger installations were substantially more expensive then conventional superchargers.

 

[Shortround6]

This begs the question- why are we turbocharging this theoretical Allison-based plane, rather then supercharging it? Were turbochargers cheaper? Turbocharging requires extensive ductwork to get the exhaust gasses that power it back behind the pilot to the turbocharger and yet more ductwork to get the forced air flow from a theoretical belly scoop back up front. A supercharger, by contrast, is powered by the engine itself so you can pretty much just ram her in there (gross simplification, of course, but still.)

Were turbos substantially cheaper then the always-expensive superchargers?

To get real altitude performance you need either 2 stage superchargers (preferably with inter-coolers) or you need to carry an oxygen supplement system like N2O.

Using a mechanical drive two stage system instead of the turbo means you can ditch the exhaust ducts and the turbo itself. you still need the second compressor, the inter-cooler and all the ducting that connects the 1st stage supercharger to the inter-cooler and from the inter-cooler to the second stage supercharger. Merlin dodged part of this by using an AFTER cooler, they placed the heat exchanger between the the second stage and the engine. They also used a liquid cooled inter cooler which, while more compact at the engine, did require larger ducts/radiator space at other points in the aircraft. This may have helped the CG problem. Inter-cooler radiator and ducts behind CG helping to balance increased weight of engine in front of CG. It also may have required more maintenance and been more susceptible to combat damage.

 

[MikeGazdik]

Okay, lets reverse engineer the P-39. Run ducting forward under the pilot to the nose section. Mount the turbocharger in the nose of the Airacobra, removing all provisions for the cannon. This should keep the CG under control.

All of this ducting is going to eliminate the the enclosed radiator in the fuselage/ wing center of the P-39. A belly scoop system similar to the Mustang will have to be utilized.

Now we have an Airacobra that can get to high altitude, and then hurry back down and land because of fuel starvation!!

 

[Shortround6]

Okay, lets reverse engineer the P-39. Run ducting forward under the pilot to the nose section. Mount the turbocharger in the nose of the Airacobra, removing all provisions for the cannon. This should keep the CG under control.

All of this ducting is going to eliminate the the enclosed radiator in the fuselage/ wing center of the P-39. A belly scoop system similar to the Mustang will have to be utilized.

Now we have an Airacobra that can get to high altitude, and then hurry back down and land because of fuel starvation!!

It also eliminates the whole rational for the Aircobra.

No 37m cannon in nose= equals no need for extension shaft-50lbs, no need for heavy rigid fuselage-50lbs, no need for tricycle landing gear-100lbs, no cannon -200lbs+, no 37mm ammo-???lbs

performance improving already

 

[MikeGazdik]

It also eliminates the whole rational for the Aircobra.

No 37m cannon in nose= equals no need for extension shaft-50lbs, no need for heavy rigid fuselage-50lbs, no need for tricycle landing gear-100lbs, no cannon -200lbs+, no 37mm ammo-???lbs

performance improving already

Not that the rational was sound. I think the design layout of the Airacobra was actually good. It just had too little development. You get some better engineers on board, and the centralized engine can be a good thing. Again I am just trying to apply the turbo concept to what airframes where available.

I guess we are running into what the USAAC had to deal with back then. Airframes that did not lend themselves to the concept, other than what was done...the Thunderbolt and the Lightning.

 

[gjs238]

It also eliminates the whole rational for the Aircobra.

I understand that it's been accepted that the rational for the P-39 was the 37mm cannon.
But I've come to think that the rational provided the opportunity for a turbocharger installation near the engine, not requiring all the ductwork of a front engine/rear turbo (or rear engine/front turbo) layout.

But making this work well is another matter.
It seems there still was not enough room for a well functioning inter/aftercooler setup.

 

[gjs238]

Airframes that did not lend themselves to the concept, other than what was done...the Thunderbolt and the Lightning.

This is what motivated me to start this thread...
* P-39 arranged turbo near engine
* P-38 arranged turbo(s) near engine as well, but solved space limitations w/duel boom design
* P-47 solved space limitation by locating turbo in rear section
* my next thought then is why not use P-47 layout w/inline engine?

 

[Colin1]

Okay, lets reverse engineer the P-39. Run ducting forward under the pilot to the nose section. Mount the turbocharger in the nose of the Airacobra, removing all provisions for the cannon

Engine front and turbo back

or

turbo front and engine back

you still have to run the ducting between them; are you certain there's room in a tight fuselage like the P-39? The drive to the airscrew, though not intrusive, was still visible in the cockpit floor contours with a transmission tunnel.

Getting the ducting to run around that might get interesting, assuming there's head room for it in the first place.

 

[davebender]

Germany developed several turbocharged engines during WWII. The BMW801J for instance. It's my understanding these engines were not mass produced for the same reason Germany did not mass produce the Jumo004A jet engine. A shortage of chromium to produce turbine blades.

Do we have historical test data for the German turbocharged engines? How does reliabilty compare to the supercharged versions of the same engine? How did the Fw-190A perform when powered by the BMW801J engine?

 

[Colin1]

Do we have historical test data for the German turbocharged engines? How does reliabilty compare to the supercharged versions of the same engine? How did the Fw-190A perform when powered by the BMW801J engine?

Could this possibly be the subject of another thread?

 

[riacrato]

Since the problem is the same I think it's okay to leave it here.

And actually the BMW J resulted in the BMW 801 TJ which saw very limited service in the Ju 388. By that time Fw 190 development had already switched more or less completely to the inline engines Jumo 213 and DB 603. The arrangement is imo rather great: All the ducting and the turbine are behind the engine. The changes to the fuselage needed to adapt to this engine wouldn't be much different than what was historically done for the inlines:

Of course for the Fw 190 you would need to re-rout the exhaust a bit


It is my understanding that the BMW 801, even without a turbocharger, was a demanding engine as far as critical resources go, hence the Heimstoffmotor ("home resource engine") project that was meant to reduce the need of scarce resources such as copper and nickel. Some of that projects achievements were incorporated in later D-2 series production (e.g. substitution of some aluminium components by steel).

We can only guess how much more expensive the 'ultimate' turbocharged BMW 801 would've been as compared to the produced variants. But you can probably say with some certainty it was more expensive than the (for Germany) already borderline acceptable BMW 801 D-2.

 

[billswagger]

Something along the lines of a P-60E ???

Looks to have the room for turbo and ducting as well as an engine.

Not sure it would be more desirable than whats already featured here.



Bill

 

[drgondog]

With a turbo charger, the US designer basically had two choices - go big with R2800, big fuselage with enough room below cockpit to run the ducting, or go small (no Cockpit) like the P-38 engine nacelles.

P-39 was simply too small with too much crap competing for space at the cockpit area, or too screwed up as far as cg to try to dump it behind the engine..