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For example, if the static compression ratio is 10:1, and the dynamic compression ratio is 7.5:1, a useful value for cylinder pressure would be 7.5 1.3 × atmospheric pressure, or 13.7 bar (relative to atmospheric pressure). The two corrections for dynamic compression ratio affect cylinder pressure in opposite directions, but not in equal strength.
The Pratt & Whitney TF30 used on the F-111 had a pressure ratio of about 20:1, while newer engines like the General Electric F110 and Pratt & Whitney F135 have improved this to about 30:1. An additional concern is weight. A higher compression ratio implies a heavier engine, which in turn costs fuel to carry around.
The engine pressure ratio (EPR) is the total pressure ratio across a jet engine, measured as the ratio of the total pressure at the exit of the propelling nozzle divided by the total pressure at the entry to the compressor. [1] Jet engines use either EPR or compressor/fan RPM as an indicator of thrust. [2]
The quality the codec can achieve is heavily based on the compression format the codec uses. A codec is not a format, and there may be multiple codecs that implement the same compression specification – for example, MPEG-1 codecs typically do not achieve quality/size ratio comparable to codecs that implement the more modern H.264 specification.
There are several differences, but the main one in practice is that compression ratio is applied to piston engines, pressure ratio to gas turbines. Compression ratio is the cause of the compression, pressure ratio is the result of this compression and increase in pressure. Compression ratio can be calculated easily from the engine's geometry.
The engine can produce any compression ratio from 8:1 to 14:1. The highest torque is achieved at 8:1, giving high acceleration, while the best gas mileage (fuel efficiency) is achieved at 14:1. The electronic engine controller responds to the pressure on the gas pedal, in real-time, altering the compression ratio seamlessly.
The original 3.3 engine, as well as the larger 3.8, are pushrod engine designs. The 3.3 was introduced in 1989 with the 1990 Chrysler Imperial, New Yorker, and related K-series models, and was joined in 1991 by the 3.8. Production on the 3.3 was stopped in 2010 after a run of 5,076,603 [2] engines, while the 3.8 remained in production until May ...
Pressure ratio, the compression ratio of a gas compressor Topics referred to by the same term This disambiguation page lists articles associated with the title Pressure ratio .