Ignition of a gas by a hot horizontal cylinder

Abstract

The modern thermal theory of ignition makes the assumption that the substance in the heating zone is stationary. However, in describing the process of ignition in liquid and gaseous systems, this assumption is inadmissible. To fully take into account the effect of natural convection, it is necessary to jointly solve the equations describing the ignition process and the equations of motion. The authors consider the problem of the ignition of a chemically reacting gas by a cylindrical body in the presence of natural convection. In order to solve the equations of a nonstationary boundary layer, the method of successive approximations was used. The convective motion in a gaseous system transforms the temperature profiles in the preheating stage of ignition, leading to the localization of ignition. The heating wave is propagated around the circumference of the cylinder at the same time it moves into the medium. Natural convection affects ignition in other ways, influencing the nonstationary ignition characteristics in such a way that there is a considerable reduction in ignition lag as compared with the heat conduction case. It was found that the chemical reaction leads to an increase in the natural convection development time. This is associated with a decreasemore » in the temperature drop between the heated cylindrical surface and the ambient medium, whose temperature rises as a result of chemical heat release.« less