A Numerical Study on Improving Large Angle Film Cooling Performance through the Use of Sister Holes

The present study evaluates a novel sister hole cooling technique using large inclination angle cylindrical holes simulated numerically. Here, a 55° inclination angle has been applied to simulate more realistic turbine conditions. Two sister holes bound the primary injection hole and are shifted slightly downstream to promote flow adhesion. As a means of determining the validity of the technique, adiabatic effectiveness and vortex flow structures were evaluated at four blowing ratios: 0.2, 0.5, 1.0, and 1.5. The results indicate that the sister hole technique dramatically reduces the primary kidney vortex pair offering significant improvements in effectiveness at all blowing ratios.