Discuss the below:
Q: A simplified representation of the diesel cycle, with just air as the working substance. Show that the efficiency of the engine is:
n = 1 - 1/y((1/rye-1/ryc)/(1/re-1/rc))
where re = V3/V2, the expansion ratio, and rc = V3/V1, the compression ratio.
If re = 5, rc = 15 and y = 1.4, evaluate n.
Notice that the compression ratio can be very much higher in a diesel engine than in a petrol engine because diesels do not suffer from pre-ignition, or pinking, as the fuel is sprayed in at the end of the compression stroke; this allows an increase in re. This is one reason why diesels are more efficient than petrol engines.