Vibrational Signals Processing for In-Cylinder Pressure Reconstruction of a Four Cylinder Spark Ignition Engine

Abstract

Knock is a phenomenon of abnormal combustion which has to be avoided during the operation of a spark ignition engine. Traditional techniques for knock detection use the in-cylinder pressure signal. At the current state of art, this kind of signal is impossible to measure on a marching vehicle due to several drawbacks. In this work the possibility of reconstructing the in-cylinder pressure by using the engine block vibrational signals is investigated. The reconstruction has been made applying the complex cepstrum transform to the signal coming from an accelerometer which has been placed on the engine head. The presented results show how the reconstruction is possible, with low percentage error, in zone of the pressure waveform over the top dead centre, which is the critical zone for knock occurrence.