A numerical study of segmented cooling-stream injection in supersonic film cooling

The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate, and numerically investigates the effect of segmented cooling-stream injection on supersonic film cooling. The results indicate that without shock-wave impingement and with helium as the coolant, segmented cooling-stream injection can reduce the mixing between the mainstream and the cooling stream to produce better cooling performance than single injection, especially at larger coolant Mach numbers. However, with nitrogen as the coolant, the cooling effect of the segmented-injection system is very close to that of the single-injection system. Mixing at the impinging region is enhanced significantly when there is an incident shock wave. When the shock wave impinges between the two coolant inlets, segmented cooling-stream injection improves film cooling effectiveness in the midstream and downstream regions more than single injection because only part of the cooling stream undergoes the enhanced mixing effect of the shock wave. The advantage of segmented injection is reduced when the impinging region is behind the second coolant inlet. The further downstream the impinging region, the smaller the associated advantage.