The investigation on the Ignition Delay of n-heptane/n-butanol Blend Fuel Using a Rapid Compression Machine at Low Temperature Combustion Regime

Abstract

This study presents both experimental and numerical investigation of ignition delay time of n-heptane and n-butanol binary fuel. The O2 concentration in the mixture was set to 9-10% to make high exhaust gas recirculation(EGR) rate condition which leads low NOx and soot emission. Experiments were performed using a rapid compression machine(RCM) at compressed pressure 20bar, several compressed temperature and three equivalence ratios(0.4, 1.0, 1.5). In addition, a numerical study on the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species in the combustion process. The results showed that the ignition delay time increased with increasing the n-butanol fraction due to a decrease of oxidation of n-heptane at the low temperature. Moreover, all of the binary fuel mixtures showed the combustion characteristics of n-heptane such as cool flame mode at low temperature and negative-temperature-coefficient(NTC) behavior. Due to the effect of high EGR rate condition, the operating region is reduced at lean condition and the ignition delay time sharply increased compared with no EGR condition.