Hydrogen oxidation near the second explosion limit in a flow reactor

Abstract

This work investigates the oxidation of hydrogen near its second explosion limit in a turbulent flow reactor at pressures of 1 to 8 bar, temperatures of 950 K and an equivalence ratio of 0.035. The concentrations of H2, O2 and H2O are measured along the reactor and simulated using several kinetic models from the literature. These experiments demonstrate evident negative pressure dependence from roughly 1 to 4 bar, with further increases in pressure resuming its positive impact on reaction rates.The simulated and measured species concentrations along the reactor generally agree within a factor of 2.Further investigation is then conducted to measure the rate coefficient of reaction H + O2 (+ M) = HO2 (+M) (R2), which is one of the most sensitive reactions in hydrogen's oxidation chemistry at these conditions. This investigation is conducted by using nitric oxide (NO) as a dopant and measuring the resulting, quasi-steady-state concentrations of NO2. The rate coefficients are obtained at 950 -1010 K. Combined with literature results, an Arrhenius expression is proposed, 2 2,0 N k = 4.50×10 20 (T/K) -1.73 [cm 6 mole -2 s -1 ], for the reaction rate at the low-pressure limit over 500 K -2000 K with N2 as the bath gas. Simulations using the models from the literature with the proposed Arrhenius expression for this reaction then demonstrate improved agreement with the experiments.