Diesel Cycle

Diesel Cycle was devised by Dr. Rudolph Diesel in 1893, with an idea to attain a higher thermal efficiency, with a high compression ratio. This is an important cycle on which all the diesel engines work. It is also known as constant pressure cycle as heat is received at a constant pressure.

The ideal diesel cycle consists of two reversible adiabatic or isentropic, a constant pressure and a constant volume processes. These processes are represented on a p-v and T-s diagrams as shown in Fig. 5.12 (a) and (b) respectively.

The air standard efficiency of this cycle is given by

Notes:

1. The efficiency of the ideal diesel cycle is lower than that of Otto cycle, for the same compression ratio.

2. The diesel cycle efficiency increases with decrease in cut-off and approaches maximum (equal to Otto cycle efficiency) when cutoff is zero, i.e. p = 1.