摘要
The supersonic mixing layer flow,consisting of a relatively cold,slow diluted hydrogen stream and a hot,faster air stream,is numerically simulated with detailed transport properties and chemical reaction mechanisms.The evolution of the combustion process in the supersonic reacting mixing layer is observed and unsteady phenomena of ignition,flame propagation and extinction are successfully captured.The ignition usually takes place at the air stream side of braid regions between two vortexes due to much higher temperature of premixed gases.After ignition,the flame propagates towards two vortexes respectively located on the upstream and downstream of the ignition position.The apparent flame speed is 1569.97 m/s,which is much higher than the laminar flame speed,resulting from the effects of expansion,turbulence,vortex stretching and consecutive ignition.After the flame arrives at the former vortex,the flame propagates along the outer region of the vortex in two branches.Then the upper flame branch close to fuel streamside distinguishes gradually due to too fuel-riched premixed mixtures in the front of the flame and the strong cooling effect of the adjacent cool fuel flow,while the lower flame branch continues to propagate in the vortex.
The supersonic mixing layer flow, consisting of a relatively cold, slow diluted hydrogen stream and a hot, faster air stream, is numerically simulated with detailed transport properties and chemical reaction mechanisms. The evolution of the combustion process in the supersonic reacting mixing layer is observed and unsteady phenomena of ignition, flame propagation and extinc- tion are successfully captured. The ignition usually takes place at the air stream side of braid regions between two vortexes due to much higher temperature of premixed gases. After ignition, the flame propagates towards two vortexes respectively located on the upstream and downstream of the ignition position. The apparent flame speed is 1569.97 m/s, which is much higher than the laminar flame speed, resulting from the effects of expansion, turbulence, vortex stretching and consecutive ignition. After the flame arrives at the former vortex, the flame propagates along the outer region of the vortex in two branches. Then the up- per flame branch close to fuel streamside distinguishes gradually due to too fuel-riched premixed mixtures in the front of the flame and the strong cooling effect of the adjacent cool fuel flow, while the lower flame branch continues to propagate in the vortex.
