Question

Α 4-stroke spark-ignition engine has a compression ratio of 10 and operates on the ideal constant volume cycle with intake pressure of 50 kPa (throttled) and intake temperature of 300 K. The exhaust pressure is 100 kPa. The heat input from combustion is 2500 kJ/kg and γ = 1.3 for the working fluid.

a. Draw the p-V diagram of the full cycle and indicate all the processes.

b. Calculate the residual gas fraction and the temperature decrease during the exhaust stroke.

c. Calculate the volumetric efficiency and net thermal efficiency of the cycle.

d. Consider the case of boosting for this engine and plot volumetric efficiency, net thermal efficiency, and residual gas fraction as a function of the ratio of intake to exhaust pressure: 0.3 < pi/pe < 1.5. Exhaust pressure in all cases would be 100 kPa. State and justify any assumptions that you make.

Note: For your cycle calculations you will need to perform iterations on the residual gas fraction. 3 iterations are sufficient for showing your work.

Answer 1

comanertion noits (x) (aう 2-3 → coast. volun, e heat additiow antlon v 4-1 cont, volume, tiont eation 0.3 2 1o) x 5 598.5 7 Now: Ta Ty Ty= 1541-01SK ftarnt, at exhaust

Part C and D of this question requires dimension of the cylinder without which we cant calculate the volumetric efficiency and

for thermal effiency we need the calorific value of the fuel