Prediction of Peak Cylinder Pressure Variations Over Varying Inlet Air Condition of Compression-Ignition Engine

Peak cylinder pressure of a compression-ignition engine can be affected by engine inlet air condition such as its temperature and pressure. The variation of peak cylinder pressure due to varying inlet air temperature and pressure is analytically studied in this paper. An analytical model is developed and thus the variations of peak cylinder pressure can be predicted along with inlet air temperature or pressure varying. It is indicated that cylinder compression ratio (CR) and intake air boost ratio (p_m0/p_i0) play significant roles in affecting the variation of peak cylinder pressure over inlet air temperature and pressure, and the pressure variation is proportional to CR^k and p_m0/p_i0. The predicted results are compared to those from engine experiments, and show a close agreement. The prediction also includes the investigation of the variation in peak cylinder pressure due to varying the cylinder TDC volume. Results from the analytical studies are presented and show that the change in p_max versus a change in the volume is also affected by compression ratio. This indicates that for a certain change in the clearance volume, a higher compression-ratio configuration would produce a greater change in p_max than a lower compression-ratio would with the rest of the engine design parameters remaining unchanged.