摘要：Supersonic film cooling tangentially ejected through a half Laval nozzle set in a backward-facing slot was numerically simulated to investigate the structures of flowfield and the mechanisms of heat transfer after the slot. In particular, changes in flowfield near the turning point in the cooling effectiveness curve were studied. The turning point is defined by extrapolation of the cooling effectiveness curve using a power-law relationship. The point corresponds to the stream?wise position where the hot mainstream is reaching the wall protected by the film coolant and to the disappearance of the unsmooth transition points in streamwise velocity profiles, where the growth rate of velocity in wall normal direc?tion changes gradually from one state to another. The transition of velocity becomes smooth downstream of the turning point. The unsmooth transition point also exists in other profiles of flow parameters, such as the mole fraction of film gas and the total temperature of the fluid, which are indicators of the mixing extent between the mainstream and film coolants. Moreover, the unsmooth transition point is more evident in the film coolant of nitrogen than that of helium due to the slower drop rate of effectiveness in the current configuration of the supersonic film cooling.
关键词：Supersonic film cooling; backward-facing step; slot; numerical simulation
