Effects of N2O addition on the ignition of H2–O2 mixtures: Experimental and detailed kinetic modeling study

Abstract

Ignition delay times of H2/O2 mixtures highly diluted with Ar and doped with various amounts of N2O (100, 400, 1600, 3200 ppm) were measured in a shock tube behind reflected shock waves over a wide range of temperatures (940–1675 K). The pressure range investigated during this work (around 1.6, 13 and 32 atm) allows studying the effect of N2O on hydrogen ignition at pressure conditions that have never been heretofore investigated. Ignition delay times were decreased when N2O was added to the mixture only for the higher nitrous oxide concentrations, and some changes in the activation energy were also observed at 1.5 and 32 atm. When it occurred, the decrease in the ignition delay time was proportional to the amount of N2O added and depended on pressure and temperature conditions. A detailed chemical kinetics model was developed using kinetic mechanisms from the literature. This model predicts well the experimental data obtained during this study and from the literature. The chemical analysis using this model showed that the decrease in the ignition delay time was mainly due to the reaction N2O + M ⇄ N2 + O + M which provides O atoms to strengthen the channel O + H2 ⇄ OH + H.