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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.
Because TVO has a lower octane rating than petrol, the engine needs a lower compression ratio. On the TVO version of the Ferguson TE20 tractor, the cylinder head was re-designed to reduce the compression ratio to 4.5:1. This reduced the power output, so the cylinder bore was increased to 85 mm to restore the power. [2]
Variable compression ratio (VCR) is a technology to adjust the compression ratio of an internal combustion engine while the engine is in operation. This is done to increase fuel efficiency while under varying loads. Variable compression engines allow the volume above the piston at top dead centre to be changed. Higher loads require lower ratios ...
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 kind of small engine compression release uses a camshaft mounted mechanical lever that pushes the exhaust valve tappet slightly, venting engine compression through the exhaust valve. Once the engine spins to starting speed, centrifugal force causes the lever to move out of the way, and the exhaust valve is allowed to seat fully.
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 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]
This can be achieved by modifying the air-fuel mixture drawn into the engine, modifying the static or dynamic compression ratio of the engine, modifying the fuel used (e.g. higher octane, different fuel types or chemistries), injection of water or methanol, modifying the timing and dwell of ignition events, and compressing the intake air.