The effect of catalytic reaction on hot surface ignition

The hot surface ignition of methane-air mixtures in microgravity has been s tudied experimentally and numerically. Experiments on the ignition of the m ixtures with electrically heated nickel wires and platinum wires in microgr avity have been performed. Numerical calculations, including the catalytic reaction rate for platinum, have been performed to understand the experimen tal results obtained in microgravity. The ignition delays and ignition temp eratures for a wide range of equivalence ratios were investigated. Experime ntal results show that the ignition temperatures with platinum wires have a maximum near the stoichiometric mixture ratio, while those with nickel wir es increase as the equivalence ratio increases. Ignition temperatures with platinum wires are higher than those with nickel wires. Numerical results s how that reactants next to platinum wires are consumed by the catalytic rea ction. Therefore, a higher temperature is required to ignite mixtures with platinum wires. The catalytic inhibition of hot surface ignition is simulat ed successfully by the numerical model.