Many diesel engines can be approximated by a limited-pressure cycle. In a limitedpressure cycle, a fraction of the fuel is burnt at constant volume and the remaining fuel is burnt at constant pressure. Use this cycle approximation with y = cJc, = 1.3 to analyze the following problem:
Inlet conditions: p, = 1.0 bar, T, = 289 K
Compression ratio: 15: 1
Heat added during combustion: 43,000 kJ/kg of fuel
Overall fuellair ratio: 0.045 kg fuelkg air
(a) Half of the fuel is burnt at constant volume, then half at constant pressure. Draw a p-V diagram and compute the fuel conversion efficiency of the cycle.
(b) Compare the efficiency and peak pressure of the cycle with the efficiency and peak pressure that would be obtained if all of the fuel were burnt at constant pressure or at constant volume.