Two Mechanisms of Kernel Ignition in Shock Tubes

The structure of the flow and temperature field behind a reflected shock wave in a shock tube is studied by numerical modeling. Two possible scenarios of the formation of the regions of elevated temperature, which are the potential ignition kernels of the gaseous mixture under the study, are demonstrated. Both scenarios are assessed as equally probable; however, depending on the parameters of the flow and diameter of the tube, one of the scenarios may be implemented earlier than the other, which is demonstrated by the example of a hydrogen–air mixture. The scenario with the ignition on the axis is the most probable one for the case of high temperatures and narrow channels, while ignition in the region of the boundary layer is implemented with a higher probability at moderate temperatures in wide channels.