An experimental and kinetic study the effect of nitrogen dioxide addition on autoignition of n-heptane

Abstract Vitiation effect is vital in the combustion-heated wind-tunnel experiments. NO2 is an active vitiated species which can affect the combustion properties of hydrocarbons. Ignition delay time experiments were performed to investigate the NO2 effect on the ignition behavior of n-heptane behind reflected shock waves. The experiments were carried out at pressures of 2 and 10 atm, and temperatures of 700–1400 K with stoichiometric n-heptane/air mixtures. 0.5% and 1.0% NO2 were added to study the vitiation effect on n-heptane ignition. The NO2 effect depends significantly on temperature and NO2 concentration. NO2 addition can promote n-heptane oxidation and dramatically reduce the ignition delay time of n-heptane at high temperatures, but has negligible effect on the autoignition of n-heptane around 700 K. The promoting effect of NO2 is stronger with higher NO2 concentration at high temperatures of T > 860 K. However, at low temperatures of T