Every one of you know how many different engine have been invented but all these engines have some very basic parameters to measure their efficiency regardless they type.
some of them i have listed here
Indicated thermal efficiency
It is the ratio of enegry in indicated power to the input fuel energy its formula is
effeciency=ip /mass of fuel per sec x calorific value of fuel
Brake Thermal Efficiency
It is the ratio between the Brake power “bp” to the input fuel energy.
bp/ mass of the fuel per sec x calorific value
it is the ratio between the Break power and indicated power
as we know that indicated power is the maximum power that can be produced by engine while the break power is the power that we get actually at the wheel .
Mechanical efficiency = bp / ip
Mean Effective pressure
this is an theoretical pressure which when multiplied by the displacement gives work it is useful in comparing the performances of different engines.
it is the ratio between the amount of air-fuel mixture that actually enters the cylinder and the amount of that could enter the cylinder under ideal standard atmospheric conditions.
Relative efficiency or efficiency ratio
It is the ratio of thermal efficiency of an actual cycle to that of the ideal cycle.
Specific power out put
it is defined as the power per unit piston area and is the measure of the engine designer’s size in using available piston area regardless of the cylinder size.
Specific fuel consumption
it is the kg of fuels per unit of power produce in kilowatt houre