DefinePK

Abstract

The article is focused on the study of shock-wave processes in the combustion chamber on the basis of the ion current signal analysis. The possibility of detecting shock waves and estimating their intensity in the combustion chamber from the ion current signal is theoretically substantiated and experimentally proved. A criterion of the non-knock combustion process is given. It is based on spectral power density function analysis of the detected ion current signal. The proposed method for calculating the perturbations of the ion current signal in the shock wave processes is based on calculation of the fundamental and multiple harmonics of the standing wave packet arising in the combustion chamber during knock. The calculation of harmonics for standing waves which is based on the calculation of the conditions for the existence of standing waves and it takes into account the geometric dimensions of the combustion chamber and the velocity of propagation of shock waves. The spectral power density function of the detected ion current signal is calculated to study shock-wave processes. The obtained function of test signal calculation is approximated by a polynomial of the second degree. To estimate the energy of the shock wave packet, the function of the approximating polynomial is subtracted from the spectral power density function of the detected ion current signal. The energy of shock waves is estimated as the sum of the difference in areas under the test and calculated functions in the range of frequencies of standing waves existence calculated for a given combustion chamber. The results of an estimate of the knock intensity of four-stroke internal combustion engine with a combustion chamber diameter of 82 mm are given as an example.