Abstract
The contribution of NO(2) to the ethanol ignition delay time was investigated behind reflected shock waves. The experiments were performed at a pressure of 0.20 MPa, temperature range of 1050-1650 K, equivalence ratio of 0.5/1.0/1.5, and ethanol/NO(2) mixing ratios of 100/0, 90/10, and 50/50. The experimental results showed that the addition of NO(2) decreased the ignition delay time and promoted the reactivity of ethanol under all equivalence ratios. With an increase in NO(2) blending, the effect of equivalence ratio on the ethanol ignition delay time decreased, and with an increase in temperature, the effect of NO(2) in promoting ethanol ignition weakened. An updated mechanism was proposed to quantify NO(2)-promoted ethanol ignition. The mechanism was validated based on available experimental data, and the results were in line with the experimental trends under all conditions. Chemical kinetic analyses were performed to interpret the interactions between NO(2) and ethanol for fuel ignition. The numerical analysis indicated that the promotion effect of NO(2) is primarily due to an increase of the rate of production and concentration of the radical pool, especially the OH radical pool. The reaction NO + HO(2) ⇔ NO(2) + OH is key to generating chain-initiating OH radicals.