Flame initiation near a cold isothermal wall: ignition by an instantaneous thermal dipole

Abstract

he ignition process produced by the instantaneous application of a linear local heat source near a cold wall is studied using irreversible Arrhenius kinetics. Special attention is devoted here to investigate the limiting case when the instantaneous source is located at a distance from the wall small in comparison with the thermal width of the flame. The ignition problem in this case is reduced to the study of flame initiation by means of a thermal dipole. Changes in the critical values of the dipole intensity for successful ignition are presented as a function of the Lewis number. The results are compared with the configuration in which the distance between the source and the cold wall is finite. This study is also relevant for safety issues in the sense of preventing accidental ignition of combustible mixtures.