Autoignition of n-Butanol/n-Heptane Blend Fuels in a Rapid Compression Machine under Low-to-Medium Temperature Ranges

Abstract

Ignition delay times of n-butanol/n-heptane mixtures (0%, 20%, 40%, 60% n-butanol in moles) were measured using a rapid compression machine at compressed pressures of 15, 20, and 30 bar, in the compressed temperature range of 650–830 K, and with equivalence ratios of 0.4, 1.0, and 1.5. Sensitivity analysis and reaction fluxes analysis were performed using a detailed mechanism of blend fuels so as to evaluate the impact of n-heptane addition on the ignition and combustion process. Over the experimental conditions in this study, the blend fuels display apparent low and high temperature reactions and a negative-temperature-coefficient (NTC) behavior; with increasing n-butanol mole fraction in the mixtures, the ignition delay times increased; the pressure curves present two-stage heat release behavior at low temperature but one-stage behavior at high temperature. It is worth noting that the n-butanol mole fraction shows negligible effect on the ignition delay times for equivalence ratios of 1.5 at low tempera...