|Thermodynamics and Propulsion|
Sometimes the overall efficiency of aircraft engines is expressed in alternative parameters: specific impulse, , and thrust specific fuel consumption, TSFC or just SFC. Both of these parameters measure how effectively fuel is used, and have dimensions.
Specific Impulse ( or ):
where is the fuel mass flow rate. To find the fuel-air ratio, , we employ a control volume around the combustor and carry out an energy balance.
Specific Fuel Consumption (SFC or TSFC):