Ignition studies of hydrogen-air mixtures over hot wire

Abstract

Hot surface ignition of combustible gas mixtures poses a safety threat in many engineering applications. Gaseous mixtures ignite when hot surface temperature reaches the ignition threshold. In the present work, two-dimensional numerical simulations with detailed reaction mechanism are performed to simulate the flow of stoichiometric hydrogen-air mixture over a stationary hot wire. The effect of heating rates, wire diameters, mixture inlet velocities, and mixture equivalence ratios on the ignition threshold is investigated. In all the cases investigated, ignition is found to occur at the rear stagnation point, and wire heating rate did not influence the ignition phenomenon significantly. With an increase in mixture inlet velocity and mixture equivalence ratio, the ignition threshold increases, whereas the threshold has been found to decrease with increasing wire diameters. The role of the local equivalence ratios at the ignition point and reaction rates prior to the ignition process has been studied to help better understand the ignition phenomenon under different conditions.