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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.
In aeronautical engineering, overall pressure ratio, or overall compression ratio, is the amount of times the pressure increases due to ram compression and the work done by the compressor stages. The compressor pressure ratio is the ratio of the stagnation pressures at the front and rear of the compressor of a gas turbine .
The most common digital compression artifacts are DCT blocks, caused by the discrete cosine transform (DCT) compression algorithm used in many digital media standards, such as JPEG, MP3, and MPEG video file formats. [1] [2] [3] These compression artifacts appear when heavy compression is applied, [1] and occur often in common digital media ...
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 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.
130 kW (180 hp), compression ratio of 5.3 :1. Wolseley W.4A Viper 150 kW (200 hp), compression ratio of 5.3 :1. Wolseley's engineers removed problems with the crankshaft and increased the compression ratio to give more power, with some early engines having a compression ratio of 5.6:1. Wolseley W.4A Viper II 160 kW (210 hp) at 2,000 rpm. [10]
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 graph above shows the intake runner pressure over 720 crank degrees of an engine with a 7-inch (180 mm) intake port/runner running at 4500 rpm, which is its torque peak (close to maximum cylinder filling and BMEP for this engine). The two pressure traces are taken from the valve end (blue) and the runner entrance (red).