An engine uses air as the operating substance. At the beginning of compression the pressure is 90 KN /m² and the temp. is 40⁰C. During the adiabatic compression, the volume is reduced to one-sixteenth of its normal value at the beginning of the compression stroke. Heat is then added at constant pressure until the temp. is 1400⁰C. The stroke is completed by adiabatic expansion until the initial volume is reached, when the cycle is closed by a constant volume process.

a) Draw the P-V and T-S diagram of the engine.

b) Determine the temperature and pressure at all the corners of the diagram.

c) Calculate the thermal efficiency of the cycle.

d) Derive the expression used.