A spark-ignition engine is throttled when operating at part load (the inlet pressure is reduced) while the fuel lair ratio is held essentially constant. Part-load operation of the engine is modeled by...

A spark-ignition engine is throttled when operating at part load (the inlet pressure is reduced) while the fuel lair ratio is held essentially constant. Part-load operation of the engine is modeled by the cycle shown in Fig. 5-2d; the inlet air is at pressure PI* the exhaust pressure is atmospheric pa, and the ambient temperature is T, . Derive an expression for the decrease in net indicated fuel conversion efficiency due to throttling from the ideal constant-volume cycle efficiency and show that it is proportional to (p_ep₁
- 1). Assume mass fuel <>