Effect of Fuel Properties on Knocking Characteristics in Rapid Compression and Expansion Machine

Abstract

The correlations between the autoignition characteristics of methane/DME/air mixtures, methane/n-butane/air mixtures, methane/propane/air mixtures and the knock intensity in a rapid compression and expansion machine were studied. In comparison of methane/DME/ air mixture with methane/n-butane/air mixture, the smaller gradient of autoignition delay time was found to cause the higher flame propagation velocity and the resultant higher knock intensity. On the other hand, in comparison of methane/DME/air mixture with methane/propane/air mixture, the smaller temperature gradient was found to cause the higher flame propagation velocity and the resultant higher knock intensity. As a result, both the gradient of autoignition delay time and temperature gradient were concluded to have a strong influence on the knock intensities.