A study of the ignition mechanism of methane-air mixtures by inert and catalytic hot surfaces

Experimental and numerical studies have been conducted on the hot surface ignition of methane-air mixtures in a closed vessel. Experiments without the feedback control of surface temperature have been performed using platinum strip in normal gravity. The results indicate the increase of the surface temperature due to the heat release of catalytic reaction. In order to define the initial condition and make the analysis simple, the following control unit was developed: which heats the wire to the setting temperature in a very short time, and maintains the wire temperature constant until ignition. Experiments with the feedback control have been performed using nickel wire and platinum wire in normal gravity and microgravity. The results describe the effects of natural convection, catalytic reaction, and oxidation of nickel on ignition delay and ignition temperature. Numerical calculations, including catalytic reaction for platinum, have been performed to analyze the experimental results in microgravity. Numerical results show that reactants near platium wire are consumed by catalytic reaction, therefore, the higher temperature is required to ignite the mixture with platinum wire. The catalytic inhibition of hot surface ignition is simulated successfully by the numerical model.