Correct Answer - Option 4 : Mechanical efficiency
Explanation:
Mechanical efficiency is defined as the ratio of brake power (delivered power) to the indicated power (power provided to the piston).
\({\eta } = \frac{{P_b}}{{P_i}} = \frac{{P_i~-~P_f}}{{P_i}}=1-\frac{P_f}{P_i}\)
Mechanical efficiency takes into account the mechanical losses in an engine.
Engine Performance Parameter :
Indicated Power:
It is the power developed inside the engine cylinder.
\(ip = \frac{{{p_m}LAN.n}}{{60}}\)
Brake Power:
This is the actual power available at the crankshaft and may be called power output of the engine. It is always less than indicated power.
\(BP = \frac{{2\pi NT}}{{60}}\)
Indicated thermal efficiency :
It is the ratio of IP to fuel power.
\({\eta _i} = \frac{{ip}}{{{{\dot m}_f} \times CV}}\)
Brake thermal efficiency :
It is the ratio of bp to fuel power.
\({\eta _b} = \frac{{bp}}{{{{\dot m}_f} \times CV}}\)
