Hydrogen-nitrous oxide delay times: Shock tube experimental study and kinetic modelling

Hydrogen-nitrous oxide mixtures have been studied for decades. In addition to their fundamental interest, they might play an important role in semi-conductor industry safety. Indeed, in silane-nitrous oxide mixtures, widely used in this industry, the silane molecule readily decomposes into molecular hydrogen which can react violently with nitrous oxide. Despite numerous shock tube studies on H2-N2O delay times, the pressure effect has never been addressed. The present work aims at studying this effect and at developing a detailed kinetic mechanism able to accurately reproduce experimental delay time data. Delay times of H2-N2O-Ar mixtures have been measured behind reflected shock waves in the 1300-2000 K temperature range and at a pressure around 300 kPa. Mixtures equivalence ratios ranged between 0.5 and 2, and the dilution was 98 and 99 mol% Ar. The present results and those from a previous study carried out in our institute show, first that, in the studied conditions, the equivalence ratio has no influence on delay times, and second, that the pressure increase drastically reduces the delay times. A kinetic model has been constructed from previously published mechanisms and tested against the present data with a mean error of 29%. Moreover, other delay time data from the literature for H2-O2-Ar, NH3-Ar and H2-N2O-Ar mixtures are also correctly reproduced as well as macroscopic parameters such as reduced activation energies.