Influence of the resonant frequency on the control of knock in diesel engines

This paper presents an alternative approach to investigating the origin and the development process of knock vibrations that occur in an indirect inje ction (IDI) diesel engine. In contrast to the conventional analysis of the pressure rise rate, this study focuses on the analysis of instantaneous res onant frequencies at different moments during combustion. The smoothed pseu do-Wigner-Ville distribution (SPWVD) and Hilbert transform methods are appl ied to estimate the resonant frequency under different conditions represent ing various knock intensities. Two important factors are found significantl y to influence knock development. Finally, design strategies and preferable fuel injection patterns are suggested for reducing knock intensity.