Mechanical Engineering - Thermodynamics - Discussion

Process 0-1 a mass of air is drawn into piston/cylinder arrangement at constant pressure.

Process 1-2 is an adiabatic (isentropic) compression of the air as the piston moves from bottom dead centre (BDC) to top dead centre (TDC).

Process 2-3 is a constant-volume heat transfer to the working gas from an external source while the piston is at top dead centre. This process is intended to represent the ignition of the fuel-air mixture and the subsequent rapid burning.

Process 3-4 is an adiabatic (isentropic) expansion (power stroke).

Process 4-1 completes the cycle by a constant-volume process in which heat is rejected from the air while the piston is at bottom dead centre.

Process 1-0 the mass of air is released to the atmosphere in a constant pressure process.

Option C is the correct answer.

But it's more logical and traditional that reversible adiabatic compression (isentropic compression) commences the cycle while heat addition at constant volume (isochoric heat addition) follows before adiabatic expansion (isentropic expansion) and the cycle ends with constant volume heat rejection (isochoric heat rejection).

Thanks.

In Otto cycle, the combination of 4 reversible cycle 2 isentropic and 2 constant volume process in this process heat addition is constant volume and heat rejection at constant volume.

Hence in this figure, the correct answer is c.

Ya. In otto cycle 1-2&3-4 are isentropic processes, then the entropy remains constant. In T-S diagram S remains constant, and also two const volume processes is there in these cycle.

Otto cycle consists of four process 2-isentropic process and 2-constant volume process (heat addition and heat rejection). It is also called SI engine cycle.

Otto cycle (OR) constant volume cycle.

It consists of two constant volume process for heat addition, heat rejection as well as two isentropic processes.

There is very minor difference b/w const pr & cost vol curve in t s diagram. B/W same temp range const pr curve will be more dipper.

In Otto cycle curve 1-2 and 2-3 are isentropic (adiabatic) so on t-s dia entropy for adibatic process is constant so C is correct.

No answer is correct, in option C during compression stroke temp should increase. Option C can be correct if cycle start from 3.

The number sequence is wrong. Process 1 to 2 is isentropic compression. That means pressure and temperature will increase.