DIESEL CYCLE

Diesel cycle

The diesel cycle is a compression ignition (rather than spark ignition) engine. Fuel is sprayed into the cylinder at P2 (high pressure) when the compression is complete, and there is ignition without a spark.

1. Isentropic compression (1à2).

2. Reversible constant pressure heating (2à3).

3. Isentropic expansion (3à4).

4. Reversible constant volume cooling (4à1).

‘

This cycle can operate with a higher compression ratio than the Otto cycle because only air is compressed and there is no risk of auto-ignition of the fuel. Although for a given compression ration the Otto cycle has higher efficiency, because the diesel engine can be operated to higher ratio, the engine can actually have higher efficiency than the Otto cycle when both are operated at compression ratios that might be achieved in practice