Specific fuel consumption
Thacker-Dey, Robert Naval Air Systems Command, Patuxent River, Maryland.
Last reviewed:January 2017
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- Thrust SFC (TSFC) and brake SFC (BSFC)
- Specific impulse of rockets
- Measurement of SFC
- SFC of alternative fuels
- Additional Reading
The normalized rate at which fuel is pumped into a combustion chamber to produce power, in the form of either shaft horsepower or thrust. In specifying the rate of fuel consumption in various applications, it has become an engineering problem not only to standardize a method of measuring the rate of fuel consumed for engines of different sizes but also to normalize such rates to compare engines with different applications. Specific fuel consumption (SFC) for gas turbine engines can be thought of, similarly, as miles per gallon or kilometers per liter in a car. However, there are different uses and purposes of the overall design of the two different types of engines (comparing a normal four-stroke spark-ignited car engine to an engine found on a jet aircraft). A spark-ignition engine running on gasoline operates with individual cylinders firing in the right sequence, with a finite volume of an air-and-fuel mixture within each cylinder, as part of its entire thermal cycle. In this case, it is appropriate to normalize fuel consumption to a set volume of a fuel as the vehicle is propelled a distance. This is not the case in gas turbine engines and rocket applications. A gas turbine engine operates with continuous combustion, with air constantly flowing into the combustion chamber in various amounts under different power settings. In this case, the volume of air or fuel being consumed to deliver thrust or shaft horsepower is not finite at all operational points, nor is it measured under operation. For these reasons, it is not appropriate to normalize fuel consumption to a constant volume of fuel in gas turbine applications, but rather to normalize the rate of fuel by its overall “power” purpose (thrust or horsepower). See also: Aircraft propulsion; Internal combustion engine; Power; Propulsion; Thrust; Turbine propulsion
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