Laminar Burning Velocities for Hydrogen-, Methane-, Acetylene-, and Propane-Nitrous Oxide Flames

Abstract

Mixtures of four fuels (hydrogen, methane, acetylene and propane) with nitrous oxide were studied to experimentally and numerically determine the laminar flame speeds at near atmospheric pressure (0.8 atm). Using the flat flame method, laminar flame speeds for these nitrous oxide flames were determined for different levels of dilution with nitrogen. A comprehensive hydrocarbon oxidation mechanism in the literature was integrated with a hydrogen-nitrous oxide sub-mechanism, and computational flame speed results using this mechanism were compared to experimental data. For all four fuel systems (hydrogen-, methane-, acetylene-, and propane-nitrous oxide), the compiled chemical mechanism under-predicted the measured laminar flame speeds over the whole range of equivalence ratio investigated. Flame speed sensitivity analyses for the hydrogen-, acetylene-, and propane-nitrous oxide systems have shown that the most sensitive reactions are within the hydrogen-nitrous oxide sub-mechanism. A revision to the reaction rate constant expression for the N2O + H ⇌ N2 + OH pathway, one of the most sensitive reaction steps, within the reported uncertainty has improved computational predictions of experimental flame speed data, although further optimization and validation of the kinetic mechanism are required.