Specific fuel consumption, often shortened to SFC, is an engineering term that is used to describe the fuel efficiency of an engine design w/ a mechanical output. It measures the mass of fuel needed to provide a given power for a given period. The common unit of measure is lb/hp·h - that is, pounds of fuel consumed for every horsepower generated during one hour of operation or kg/kW·h in metric units. Therefore a lower number indicates better efficiency. The way SFC for thrust engines (e.g. turbojets, turbofans, ramjets, rocket engines, etc) is measured is slightly different; the mass of fuel needed to provide a given net thrust for a given period e.g. lb/hr/lbf or g/s/kN in S.I. units. This is called specific impulse. However, gas turbines with a mechanical shaft output (i.e. turboprops and turboshafts) have their efficiency measure interms specific fuel consumption. Engineering is the design, analysis, and/or construction of works for practical purposes. ... An engine is something that produces some effect from a given input. ... Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted. ... Turbojets are the simplest and oldest kind of general purpose jet engine. ... It has been suggested that Fan (turbofan) be merged into this article or section. ... A ramjet, sometimes referred to as a stovepipe jet, is a type of jet engine. ... A cold (un-ignited) rocket engine test at NASA A rocket engine is a reaction engine that can be used for spacecraft propulsion as well as terrestrial uses, such as missiles. ... Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted. ... Cover of brochure The International System of Units. ... The specific impulse (commonly abbreviated Isp) of a propulsion system is the impulse (change in momentum) per unit mass of propellant. ... This machine has a single-stage centrifugal compressor and turbine, a recuperator, and foil bearings. ... A schematic diagram showing the operation of a turboprop engine. ... Schematic diagram showing the operation of a simplified turboshaft engine. ...

SFC is dependent on engine design, but differences in the SFC between different engines using the same underlying technology tend to be quite small. For instance, typical gasoline engines will have a SFC of about 0.5 lb/hp·h or (0.3kg/kW·h = 83g/MJ), regardless of the design of any particular engine. Generally, SFC within a particular class of engine will decrease when the compression ratio is increased. Increasing overall pressure ratio on jet engines also tends to decrease SFC. Diesel engines have better SFCs than gasoline, largely because they have much higher compression ratios and therefore they can convert more of the heat produced into power. Gasoline is a petroleum-derived liquid mixture consisting mostly of hydrocarbons and enhanced with benzene or iso-octane to increase octane ratings, used as fuel in internal combustion engines. ... Bold text 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). ... Overall Pressure Ratio is an engine cycle term used in Gas Turbine Engineering and is defined as the ratio of the stagnation pressure at combustor entry, to that at compression entry. ...

In practical applications, other factors are usually highly significant in determining the fuel efficiency of a particular engine design in that particular application. For instance, in aircraft, turbine (jet and turboprop) engines are typically much smaller and lighter than equivalently powerful piston engine designs, both properties reducing the levels of drag on the plane and reducing the amount of power needed to move the aircraft. Therefore, turbines are more efficient for aircraft propulsion than might be indicated by a simplistic look at the table below. An object falling through a gas or liquid experiences a force in direction opposite to its motion. ...

It should be noted that SFC varies with throttle setting, altitude and climate. For jet engines, flight speed also has a significant effect upon SFC. Consequently, although the nominal SFC is a useful measure of fuel efficiency, the Total Fuel Burn is of more importance to the customer.

Typical Values of SFC

The following table gives the specific fuel consumption of several types of engine. For comparison, the theoretical work that can be derived from burning octane (based on change in Gibbs free energy going to gaseous H₂O and CO₂) is 45.7 MJ/kg, corresponding to 79 g/kWh. R-phrases , , , , S-phrases , , , , , , , Flash point 13 °C Autoignition temperature 220 °C Explosive limits 1. ... In thermodynamics, the Gibbs free energy is a thermodynamic potential which measures the useful work obtainable from a closed thermodynamic system at a constant temperature and pressure. ...

In the category of jet engines, the General Electric CF6-80C2B2F medium sized civil turbofan (at Max Power, Sea Level Static, ISA, uninstalled) uses 0.307 lb/hr per lbf of thrust (8.696 g/s/kN). At a normal cruising speed of 913 km/hr, this comes out to 123 g/kWh. In physics and engineering, including mechanical and electrical engineering, energy efficiency is a dimensionless number, with a value between 0 and 1 or with times 100 given in percent. ... A ramjet, sometimes referred to as a stovepipe jet, is a type of jet engine. ... The four-stroke cycle of an internal combustion engine is the cycle most commonly used for automotive and industrial purposes today ( cars and trucks, generators, etc). ... This article or section does not cite its references or sources. ... Wright R-3350-57 The R-3350 Duplex-Cyclone was one of the most powerful radial aircraft engines produced in the United States. ... The Junkers Jumo 205 aircraft engine was the most famous of a series of diesel engines that were the first, and for more than half a century, the only successful diesel aircraft engines. ... The Nomad was a complex Diesel cycle aircraft engine from Napier & Son of the UK. The Nomad used a turbine to recover power from the exhaust of the otherwise conventional Diesel engine, resulting in a specific fuel consumption that remains unmatched today, 50 years later. ... This page lists automobile engines that Volkswagen or its subsidiaries uses today. ... Volvo Cars is the car maker using the brand Volvo. ... LM6000 GTG in an electrical power plant application. ... Schematic diagram showing the operation of a simplified turboshaft engine. ... The MAN B&W Diesel Group is a supplier of large diesel engines for marine propulsion systems, stationary power supply and rail traction. ... The Wärtsilä-Sulzer RTA96-C turbocharged two-stroke diesel engine is the largest engine in the world, designed for large container ships. ... In a combined cycle power plant, or combined cycle gas turbine (CCGT) plant, a gas turbine generator generates electricity and the waste heat from the gas turbine is used to make steam to generate additional electricity via a steam turbine, this last step enhances the efficiency of electricity generation. ... The worlds first commercial, oil-free gas turbine is manufactured by Capstone. ... CF6 turbofan at the KLM engine shop The General Electric TF39 and CF6 family of high-bypass turbofan engines are the most popular large aircraft turbines in the world, powering civil and military widebodies from a variety of manufacturers. ...

See also

• Energies per unit mass
• Specific impulse