Approximate analysis of SI engine knocking using Wavelet and its control with cooled exhaust gas recirculation

Abstract

Engine knocking acts as an obstruction for improving the engine performance, hence limiting the compression ratio below the highest usable compression ratio (HUCR). Even though the design condition is kept much below HUCR, knocking occurs during the long-running conditions due to the reduction in the heat carrying capacity of the coolant. The present study focuses on the prediction of knocking from the acoustic signals produced by the engine using Wavelet theory. Thermodynamic modelling of the spark ignition engine is done to analyse the performance enhancement that could be achieved by increasing the amount of cooled exhaust gas recirculation (EGR). During the occurrence of knocking, cooled exhaust gas is recirculated to control the in-cylinder temperature and hence the knocking. In addition to the reduction in temperature, the analysis shows that the thermal efficiency of the engine has increased about 12% with the cooled EGR.

Keywords

• spark ignition engine
• thermodynamic modelling
• auto-ignition
• knocking
• wavelet
• cooled exhaust gas recirculation