compression ratio (redirected from compression ratios)
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compression ratio[kəm′presh·ən ‚rā·shō]
The ratio of the gain of a device at a low power level to the gain at some higher level, usually expressed in decibels. Also known as compression.
The ratio in internal combustion engines between the volume displaced by the piston plus the clearance space, to the volume of the clearance space. Also known as compression.
Ratio of the volume of loose metal powder to the volume of the compact made from it.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
the ratio of the volume of the working fluid at the beginning of compression in the cylinder of an internal-combustion engine to the volume at the end of compression. The working fluid in carburetor engines is an air-fuel mixture; in diesel engines it is air. An increase in the compression ratio causes a decrease in the volume of the working fluid at the end of the compression stroke; the pressure and temperature of the working fluid are increased correspondingly, combustion is accelerated, and heat losses are reduced. A higher compression ratio increases the power output of an engine and improves fuel economy. However, increases in the compression ratio are limited by the fuel’s ability to prevent detonation. Compression ratios for carburetor engines range from 6.5:1 to 9.5:1; those for diesel engines are between 16:1 and 21:1.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
In a cylinder, the piston displacement plus clearance volume, divided by the clearance volume. This is the nominal compression ratio determined by cylinder geometry alone. In practice, the actual compression ratio is appreciably less than the nominal value because the volumetric efficiency of an unsupercharged engine is less than 100%, partly because of late intake valve closing. In spark ignition engines the allowable compression ratio is limited by incipient knock at wide-open throttle. See Combustion chamber, Internal combustion engine
McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.
. The ratio of the volume of fuel-air mixture in a reciprocating engine when the piston is at the bottom dead center to the volume when it is at the top dead center. It is the ratio of the cylinder volume at the end of the intake stroke to the cylinder volume at the end of the compression stroke.ii
. The ratio of the compressor discharge pressure to the compressor inlet pressure. Also called compressor pressure ratio
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
compression ratioThe measurement of compressed data. For example, a file compressed into 1/4th of its original size can be expressed as 4:1, 25%, 75% or 2 bits per byte. See archive program and data compression.
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