Compression ratio

The compression ratio is a single number that can be used to predict the performance of any engine (such as an internal-combustion engine or a Stirling Engine). It is the ratio between the volume of the cylinder, when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke. A high compression ratio allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. High ratios place increased oxygen and fuel molecules into a reduced space; thus, they allow increased power at the moment of ignition and the extraction of more useful work from that power by expanding the hot gas to a greater degree. Higher compression ratios, however, also make engine knocking, also known as detonation or pre-ignition, more likely and this can reduce an engine's efficiency and even physically damage it.
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1. In signal compression, the ratio of the dynamic range of compressor input signals to the dynamic range of the compressor output signals. Note: The compression ratio is usually expressed in dB. For example, a 40-dB input range compressed to a 30-dB output range would be equivalent to a 10-dB compression. 2. In digital facsimile, the ratio of the total pels scanned for the object to the total encoded bits sent for picture information. 3. The ratio of the gain of a device at a low power level to the gain at some higher level. Note: The compression ratio is usually expressed in dB.

The volume of the combustion chamber and cylinder when the piston is at the bottom of its stroke, divided by the volume of the combustion chamber when the piston is at the top of its stroke. (TII1) (TII2)

compression ratio
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RAPPORTO DI COMPRESSIONE [DI UN MOTORE]