Moderator: Mike Everman
dynajetjerry wrote:Hi, Guys,
Another comment, if I may: Though the mass of ejected exhaust would increase with water injection, its cooling effect might be enough to reduce expansion of the exhaust. Might this also reduce thrust? We must remember that "the hotter the better" in heat engines where efficiencies are paramount. Perhaps such a slight reduction would be more theoretical than real.
I am reminded of the "stealth" fighters and bombers. To reduce heat signatures, they expand and cool the exhausts before they are allowed to exit the plane. My question is this: how much (if any) does this cool-down reduce thrust below that of a similar, uncooled jet engine?
....In normal service, the P-51H Mustang was rated at 1,380 hp, but WEP would deliver up to 2,218 hp. The Vought F4U Corsair, not originally equipped for WEP, later boasted a power increase of up to 410 hp (17%) when WEP was engaged. Several methods were used to boost engine power by manufacturers, including water injection and methanol-water injection. Some earlier engines simply allowed the throttle to open wider than normal, allowing more air to flow through the intake. All WEP methods result in greater-than-usual stresses on the engine, and correspond to a reduced engine lifetime. For some airplanes, such as the P-51, use of WEP required the plane to be grounded after landing and the engine torn down and inspected for damage before returning to the air.
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