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


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.


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