04.08.2010, 14:25
http://www.thunderboats.org/history/history0323.html
Link gives a good breakdown of specs including supercharger type and ratios. Most of all the turbosupercharged aircraft of WWII also had internally driven chargers that are part of the powerplant but some had additional exhaust driven chargers that were used to boost manifold pressure or in the case of the Wright R-3350 the turbines were coupled directly back into the main crankshaft. These are referred to as turbocompounded powerplants. They powered the Lockheed Constellation. The B-29,s also used turbocharging in addition to the internally driven supercharger but are not turbocompounded. If you read the writeup at the above site you will see that Allison also experimented with turbocompounded powerplants. This is probably a good time to review the termonoloy:
Superchargers are always directly engine driven
Turbochargers are driven by exhaust gases.
Turbosuperchargers are a combination of both of the above. Basically they are all airpumps used to boost manifold pressure. The turbos are making use of some of the heat energy before it passes from the exhaust. Again I will say that all the large in-lines from WWII were supercharged.
Some would probably argue that the V-1710s problems were related to the size of the supercharger and detonation problems in some, You will notice they were fitted with ADI to help alleviate this problem at high boost pressures.
Supercharger: The engine supercharger (second stage supercharger) is contained in the accessory housing and is driven from the flexible inner member of the hydraulic vibration damper. The impeller is 10.25" diameter with 15 vanes and includes a separate rotating reverse-curved inducer guide vane inlet guide, the relationship with the impeller being maintained by the common splined shaft. The diffuser is cast integrally with the supercharger cover, which also contains the inlet to which the injector throttle body mounts. The impeller is overhung, with the shaft supported by two floating lead-bronze steel backed bearings placed on both sides of the supercharger drive gear. The bearing are pressure lubricated with engine oil.
The auxiliary stage is contained in a separate assembly coupled to the engine accessory section. It is intended to provide a critical altitude of 25,000 ft by delivering air to the engine supercharger at pressures close to sea-level when at critical altitude. This requires large volume of low density air to be handled by the auxiliary supercharger -- because of the density of the air at 25,000 ft the supercharger must move 2.23 times more air volume than the engine supercharger, and compress the air to about 2.7 times to deliver sea-level conditions. The auxiliary stage drive was obtained by a power-takeoff from the starter gear which connects to a driveshaft incorporating a universal joint, the driveshaft being contained in a tube coupling the engine accessory section with the remote auxiliary stage. The driveshaft hydraulic torque converter connected to the step-up gears contained in the auxiliary supercharger housing. The torque-converter provides variable speed for the supercharger by varying the amount of oil and therefore the coupling of the torque converter. The speed controlled by a boost-regulating system, permitting infinitely variable control of the speed of the auxiliary stage which was used to control manifold pressure so that power could is controlled while the throttle remains wide-open. The auxiliary supercharger consumes 490 hp from the crankshaft at the 2250 hp WER rating.
Link gives a good breakdown of specs including supercharger type and ratios. Most of all the turbosupercharged aircraft of WWII also had internally driven chargers that are part of the powerplant but some had additional exhaust driven chargers that were used to boost manifold pressure or in the case of the Wright R-3350 the turbines were coupled directly back into the main crankshaft. These are referred to as turbocompounded powerplants. They powered the Lockheed Constellation. The B-29,s also used turbocharging in addition to the internally driven supercharger but are not turbocompounded. If you read the writeup at the above site you will see that Allison also experimented with turbocompounded powerplants. This is probably a good time to review the termonoloy:
Superchargers are always directly engine driven
Turbochargers are driven by exhaust gases.
Turbosuperchargers are a combination of both of the above. Basically they are all airpumps used to boost manifold pressure. The turbos are making use of some of the heat energy before it passes from the exhaust. Again I will say that all the large in-lines from WWII were supercharged.
Some would probably argue that the V-1710s problems were related to the size of the supercharger and detonation problems in some, You will notice they were fitted with ADI to help alleviate this problem at high boost pressures.
{HVY-E}Jinxx Wrote:.041 Safety Wire Wrote:The Allison that powers the P-40 was a supercharged powerplant though it did not have a multistage supercharger.
Sorry sir, but you are incorrect.
The P40 was not supercharged. The British experimented with superchargers in the P-40F model, but it was not powered by the Allison. It was a Merlin powered machine.
As noted in Aviation History's Website.....
"The P-40 was initially designed around the Allison V-1710 liquid-cooled inline engine which offered better streamlining, more power per unit of frontal area, and better specific fuel consumption than did air-cooled radials of comparable power. Unfortunately, the rated altitude of the Allison engine was only some 12,000 feet, rendering combat above 15,000 feet a completely impracticable proposition. The P-40's ancestry dated back as far as 1924; the famed Curtiss Hawk fighters being in the forefront of all US warplanes. But its development was hindered from the start. The overall limitations of its design were such that the addition of multi-speed superchargers was considered inadvisable in view of the pending production of superior fighter designs."
The only P40, (Allison Powered), to have an integral Supercharger was the Prototype.
"One of the most significant steps in P-40 development came in 1941, when a British-built Rolls-Royce Merlin 28 engine with a single-stage, two-speed supercharger was installed in a Kittyhawk I airframe to improve its high-altitude performance. The Curtiss H-87-D, or XP-40F, as the Merlin-powered prototype became known, then had 1,300 hp available for takeoff, and 1,120 hp at 18,500 feet, which offered vast improvements over earlier models and endowed a maximum speed of 373 mph. This was reduced slightly in the YP-40F, which, like later variants, had the Packard-built Merlin V-1650-1 and revised cooling, the air intake above the cowling being incorporated in the radiator scoop. Gross weight climbed to 9,870 lb.
Following experiments in cooling-drag reduction in 1943 with a P-40K-10-CU which had its "beard" radiator removed to wing installations, and in rear vision improvements by installing a "bubble" canopy on a standard P-40L, a general " clean-up " programme was initiated, resulting in the sole XP-40Q. With a 1,425 hp Allison V-1710-121 engine, the XP-40Q was modified from the first P-40K-I to have a "bubble" canopy and cut-down rear fuselage, wing radiators and, eventually, clipped wing tips. A four-blade propeller was fitted, and water injection installed. With a weight of only 9,000 lb, the XP40Q attained a maximum speed of 422 mph. This was still less than the speed attained by contemporary production Mustangs and Thunderbolts , however, and the XP-40Q did not achieve production. "
S!
Supercharger: The engine supercharger (second stage supercharger) is contained in the accessory housing and is driven from the flexible inner member of the hydraulic vibration damper. The impeller is 10.25" diameter with 15 vanes and includes a separate rotating reverse-curved inducer guide vane inlet guide, the relationship with the impeller being maintained by the common splined shaft. The diffuser is cast integrally with the supercharger cover, which also contains the inlet to which the injector throttle body mounts. The impeller is overhung, with the shaft supported by two floating lead-bronze steel backed bearings placed on both sides of the supercharger drive gear. The bearing are pressure lubricated with engine oil.
The auxiliary stage is contained in a separate assembly coupled to the engine accessory section. It is intended to provide a critical altitude of 25,000 ft by delivering air to the engine supercharger at pressures close to sea-level when at critical altitude. This requires large volume of low density air to be handled by the auxiliary supercharger -- because of the density of the air at 25,000 ft the supercharger must move 2.23 times more air volume than the engine supercharger, and compress the air to about 2.7 times to deliver sea-level conditions. The auxiliary stage drive was obtained by a power-takeoff from the starter gear which connects to a driveshaft incorporating a universal joint, the driveshaft being contained in a tube coupling the engine accessory section with the remote auxiliary stage. The driveshaft hydraulic torque converter connected to the step-up gears contained in the auxiliary supercharger housing. The torque-converter provides variable speed for the supercharger by varying the amount of oil and therefore the coupling of the torque converter. The speed controlled by a boost-regulating system, permitting infinitely variable control of the speed of the auxiliary stage which was used to control manifold pressure so that power could is controlled while the throttle remains wide-open. The auxiliary supercharger consumes 490 hp from the crankshaft at the 2250 hp WER rating.