A numerical simulation is used to investigate the
effect of adding secondary hole branched out from a compound
angle injection hole. The use of secondary holes
with compound angle film cooling is considered as a novel
concept of compound angle film cooling. The used orientation
angle is 30°. The diameter of the secondary hole is half
of the main diameter (compound angle injection hole diameter).
The studied cases are considered at blowing ratios of
0.5, 0.75, 1.0, 1.5, 2.0, and 2.5. The study was carried out
using the realizable k-ε model. The presence of the secondary
hole improves the film cooling at all studied blowing
ratios except at M = 0.5 due to the weakness of the coolant
flow through the main hole. The flow through the secondary
hole tries to damp the vortex coming out from the
main hole. The optimum blowing ratio is at M = 0.75–1.0.
The enhancement in the overall film cooling effectiveness
at M = 1 is 0.12 as compared to the compound angle injection
hole case by about 83%. |
