Experimental and Kinetic Study of the Promoting Effect of Nitrogen Dioxide on Ethane Autoignition in a Rapid Compression Machine

Abstract

Nitrogen oxides (NOx: NO2 and NO) are the main pollutants produced in combustion. Previous studies have focused on the NOx forming mechanism and control strategies but have paid less attention to the interaction between NOx and hydrocarbon fuels; even a small amount of NOx can significantly affect the ignitions of hydrocarbons. The ignition characteristic is of great importance for the optimization design and operation control of engines such as diesel engines, which are affected by the self-ignition characteristics of fuels. In this study, a rapid compression machine was used to measure the ignition delay times of seven fuel-lean C2H6/O2/Ar mixtures with [NO2]/[C2H6] ranging from 0.0 to 50% at Tc = 760–970 K and Pc = 30 bar. The results exhibit no negative temperature coefficient phenomenon in the ignition of ethane with or without NO2. A great reduction in the ignition delay time and the global activation energy is observed in the presence of NO2, which becomes more noticeable with increasing the NO2 concentration. Subsequently, four literature models involving the C2H6/NO2 chemistry were validated against the new measurements. Moreover, the key elementary reactions and important reaction channels controlling the ignition of C2H6/NO2 mixtures were then identified by the detailed chemical kinetic analysis.