Autoignition of Binary Fuel Blends of n-Butanol and n-Heptane in a Rapid Compression Machine

Autoignition of binary blends of n-butanol and n-heptane was studied in a rapid compression machine at an equivalence ratio of 0.4 and a compressed pressure of 20 bar with the compressed temperature varying from 700 K to 907 K. Within the temperature range covered in this study, no cool flame or negative temperature coefficient behavior was observed for neat n-butanol. With the presence of n-heptane in the binary fuel mixture, the overall ignition delay is appreciably shortened as compared to that for neat n-butanol. In addition, all of the n-butanol/n-heptane blends investigated in this study exhibit pronounced cool flame behavior at low temperatures. The difference in total ignition delay between neat n-butanol and an n-butanol/n-heptane blend is observed to be temperature-dependent. Furthermore, a nonlinear relationship between the total ignition delay and the mole fraction of n-butanol in the binary fuel mixture is observed at low temperatures.