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The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine. A fundamental specification for such engines, it can be measured in two different ways.
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 .
Lossless compression of digitized data such as video, digitized film, and audio preserves all the information, but it does not generally achieve compression ratio much better than 2:1 because of the intrinsic entropy of the data. Compression algorithms which provide higher ratios either incur very large overheads or work only for specific data ...
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]
However, a real diesel engine will be more efficient overall since it will have the ability to operate at higher compression ratios. If a petrol engine were to have the same compression ratio, then knocking (self-ignition) would occur and this would severely reduce the efficiency, whereas in a diesel engine, the self ignition is the desired ...
At high overall pressure ratios, the compression system is usually split into two units; a low-pressure (LP) compressor mounted on one shaft followed by a high-pressure (HP) compressor mounted on the HP shaft and driven by its own (HP) turbine. On civil turbofans, the first stage of the LP compressor is often a single-stage fan.
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 ...
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.