Example: Diesel Cycle
An air standard four-stroke Diesel cycle has a clearance volume Vc = 0.5 litre, and a compression ratio r = 16.16. Intake temperature and pressure are 17 ◦C and 1 bar, respectively, and the temperature at the end of the expansion is 707 ◦C. The engine runs at 4400 rpm. We determine temperatures, pressures and specific volume for the four corner points of the process, and compute heat and work for all subprocesses. For the computation we treat the working fluid as air with variable specific heats.
We outline how the various properties are determined, and collect their numerical values in the table below this paragraph. The values for T1, p1 and T4 are given above. From the ideal gas law we have v1 = v4 = RT1 ; from the compression ratio v2 = v1 . The compression process 1-2 is isentropic, so that for the relative volume vr (T2) = vr (T1 ) . With tabulated data for vr (T ) follows T2, while the ideal gas law gives the pressures p2 = p3 = RT2 . With T4 given, the pressure at 4 follows from the ideal gas law, p4 = RT4 . The expansion 3-4 is isentropic, so that pr (T3) = pr (T4) p3 . With tabulated data follows T3, and from the ideal gas law v3 = RT3 . With this, all points are identified, and energies and enthalpies can be found from the property table. Altogether we have
