Detecting the combustion phase and the biodiesel blend using a knock sensor

Existing methods of detecting the combustion phase of a diesel engine are mainly based upon high-cost in-cylinder pressure sensors. This paper presents a method of estimating the location of 75% of the mass fraction burned by using the traditional knock sensor signal. It is observed through experimental data that the knock signal has a close correlation to the location of 75% of the mass fraction burned. In this study, the knock integration is used to represent the knock intensity, while the piecewise knock integration (integration over a crank angle of 1°) is used to detect the location of 75% of the mass fraction burned. The proposed estimation method was validated using the experimental data and provided an accurate estimation of the location of 75% of the mass fraction burned. In addition, the feasibility of using the knock sensor signal to detect the biodiesel content is demonstrated using experimental data.