Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
The P-51A and Mustang Mk 1 had a single stage supercharger as did the early Spitfires. Later they had a two stage supercharger to give altitude performance. The P-47 and P-38 used an exhaust turbo for one stage and then and engine driven supercharger for the other stage, this works very well but is hard to fit in a single seat fighter. When Rolls Royce were asked to produce an engine for a high altitude Wellington bomber they discounted the use of a turbo just because of the difficulty in adapting it for anything else especially single engine fighters.
Here, from Wiki. "The R-2800 powered several types of fighters and medium bombers during the war, including the U.S. Navy's Vought F4U Corsair, with the XF4U-1 first prototype Corsair becoming the first airframe to fly (as originally designed) with the Double Wasp[7] in its XR-2800-4 prototype version on May 29, 1940,[8] and the first single-engine American fighter plane to exceed 400 mph (640 km/h) in level flight during October 1940. The R-2800 also powered the Corsair's naval rival, the Grumman F6F Hellcat, the U.S. Army Air Forces' Republic P-47 Thunderbolt (which uniquely, for single-engined aircraft, used a General Electric turbocharger), the twin-engine Martin B-26 Marauder and Douglas A-26 Invader, as well as the first purpose-built twin-engine radar-equipped night fighter, the Northrop P-61 Black Widow. When the US entered the war in December 1941, designs advanced rapidly, and long-established engines such as the Wright Cyclone and Double Wasp were re-rated on fuel of much higher octane rating (anti-knock value) to give considerably more power. By 1944, versions of the R-2800 powering late-model P-47s (and other aircraft) had a rating (experimental) of 2,800 hp (2,100 kW) on 115-grade fuel with water injection.[4]"I don't see, or missed, any mention of engine driven on the P-47. All exhaust gas managed by variable ducting ...just didn't see any text to 'engine driven' in that manuals.
Seems, P-47 pilots were taught to manage duct work air flow to and from the turbo-supercharger to maximize engine performance.
Seems, P-47 pilots were taught to manage duct work air flow to and from the turbo-supercharger to maximize engine performance.
Here, from Wiki. "The R-2800 powered several types of fighters and medium bombers during the war, including the U.S. Navy's Vought F4U Corsair, with the XF4U-1 first prototype Corsair becoming the first airframe to fly (as originally designed) with the Double Wasp[7] in its XR-2800-4 prototype version on May 29, 1940,[8] and the first single-engine American fighter plane to exceed 400 mph (640 km/h) in level flight during October 1940. The R-2800 also powered the Corsair's naval rival, the Grumman F6F Hellcat, the U.S. Army Air Forces' Republic P-47 Thunderbolt (which uniquely, for single-engined aircraft, used a General Electric turbocharger), the twin-engine Martin B-26 Marauder and Douglas A-26 Invader, as well as the first purpose-built twin-engine radar-equipped night fighter, the Northrop P-61 Black Widow. When the US entered the war in December 1941, designs advanced rapidly, and long-established engines such as the Wright Cyclone and Double Wasp were re-rated on fuel of much higher octane rating (anti-knock value) to give considerably more power. By 1944, versions of the R-2800 powering late-model P-47s (and other aircraft) had a rating (experimental) of 2,800 hp (2,100 kW) on 115-grade fuel with water injection.[4]"
Apart from the aircraft listed in my post many other American bombers, the problem comes with a single engine fighter because the logical place for the turbo is where the pilot or fuel are. On the allied side the RR Merlin with a two stage two speed supercharger was found to be best, especially with regard to the P-51 because it bolted almost straight in with few modifications. A Turbo version would have the turbo where the P-51s cooling system is.I got all that sir. But what other aircraft has a turbo-supercharging system like the P-47? And, why not?
Unless the Supercharger is two-speed and requires the pilot to manually change speeds, there is no need for the pilot to interact with the Supercharger. Some Superchargers shifted from low speed to high speed automatically, others required the pilot to make the change manually. I'm not sure if the single stage Supercharger on the P-47 was single speed or two speed.I don't see, or missed, any mention of engine driven on the P-47. All exhaust gas managed by variable ducting ...just didn't see any text to 'engine driven' in that manuals.
Seems, P-47 pilots were taught to manage duct work air flow to and from the turbo-supercharger to maximize engine performance.
I don't believe there was enough forward thrust to offset the drag of outlet duct on the P-47. In most cases the energy contained in the exhaust gases is greatly reduced as it is converted to mechanical energy in the Turbocharger. The loss of thrust from the exhaust is one of the downsides of the Turbo-Supercharger.Underneath the star in the insignia. at high altitude most of the exhaust was exiting the aircraft though that duct. I am not sure if it gave any forward thrust or not.
I would note that all other US turbos just dumped the exhaust gas from the turbo out into open air. In part to expose the turbine blades to cool air to keep the temperature down.
As previously mentioned the P-38, and additionally the B-17 and B-29. Once again, the bulk of the system was not well suited for use in a single engine fighter. Additionally it was the U.S.A.A.F. that were true advocates of the Turbo-Supercharger. The U.S.N. and most other countries primarily relied on the Two Stage Supercharger for high altitude performance.I got all that sir. But what other aircraft has a turbo-supercharging system like the P-47? And, why not?
Hi Husky, just in case you don't know what "waste gates" are I'll post this. No insult intended.
A turbocharger has a compressor the same as a supercharger. In WWII, turbochargers were called "turbosuperchargers" leading to modern-day confusion by many people. There are several types of compressors, but the ones in the P-47 look very similar to a supercharger compressor. Both the supercharger and the turbocharger compressors need to be rotated mechanically by something to work. In the case of a supercharger, the compressor is connected to the crankshaft via a gear and the engine supplies the power to turn the compressor. it cnn be 0 - 300 or so horsepower, depending on rpm and boost.
In the case of the P-47 turbocharger, the exhaust is routed through a fanlike arrangement (looks like a turbojet engine turbine blade set) and the flow of the exhaust makes it turn. It is connected via a solid shaft to the compressor and it's sort of like driving a fan with compressed air. If the entire exhaust is routed through the fan at all times, the compressor would be working all the time at maximum boost, which is not desirable. So, they have a pivoting flap (pivots on pins) in the exhaust pipe that opens and closes to let all or any portion of the exhaust flow out the exhaust pipe or through the turbocharger. If the flap closes off the exhaust pipe, all the exhaust goes to the turbo fan. If the flap closes off the fan, the entire exhaust goes out the exhaust pipe and the extra power that could be gained from using it for boost is "wasted" by the waste gate. If the flap is anywhere in between fully open or closed, some portion flows out the exhaust pipe and the rest flows to the turbo fan to spin it and generate boost via the compressor connected to the fan. They use a pressure regulator to control the boost to some desired set point by moving the waste gate.
In the case of the P-47 turbo system above, the exhaust pipe is up near the front and the pipe to the turbo runs along the lower left fuselage in a stainless tunnel to the turbo fan, which is located behind the cockpit just over the belly bump on the bottom rear of the fuselage in front of the tailwheel. The compression generated heats up the air and it goes through a radiator before flowing back forward through aluminum pipes that are routed on either side of the cockpit at about elbow height and back to the pressure carburetor.
Hope that helps. Cheers.
I think you meant to say "At low altitude where the turbo was not needed..."At low altitude where the turbo was needed the wastegates dumped the majority of the exhaust out just behind the oil cooler doors. as the plane climbed the waste gates shut and routed more of the exhaust gas to the turbo, after passing through the turbo the exhaust exited the aircraft though the duct in the bottom of the plane.
From what I read, they later introduced a new propeller to the P-47 that ENORMOUSLY improved the aircraft's climbing ability. Must have been a nasty shock to the Germans.As a kid reading Robert S. Johnsons' "Thunderbolt", I was captured by his exploits and the aircraft he flew. I really became fond of the P-47; I found out it was huge for a fighter, didn't climb all well (not counting zoom climbs), wasn't all that good maneuvering (depending upon profiles of flight).
I think the USAAF also used two stage Supercharged R-2800's in the A-26, B-26, C-46 and early versions of the P-61 but I could be wrong maybe they were single stage.There were 2-stage supercharged R-2800, but they were for the Navy, not the USAAF. The Thunderbolt had a single-stage supercharger for low-altitude boost and an additional turbocharger for boost at higher altitudes.
Not in the early versions, WEP wasn't approved until late 1943 for these aircraft, that changed things a bit. The F4U (and F6F) didn't engage the auxiliary supercharger low gear until they were at several thousand feet. The Corsair and Hellcat(and any other plane using the two stage P&W R-2800) could disengage the aux stage (put it in neutral) and ran on just the engine driven single speed supercharger. The engine in an F4U weighed 215lbs more than the engine in the P-47 due to the weight of the auxiliary supercharger.That would seem to be a disadvantage down low when compared to a two stage Supercharger. Did the Corsair have more horsepower available at take off than the P-47?
The P-61 had the two stage engine, the others were single stage but had two speeds.I think the USAAF also used two stage Supercharged R-2800's in the A-26, B-26, C-46 and early versions of the P-61 but I could be wrong maybe they were single stage.