Mixing Flow Haracteristics Of Tip Leakage And Coolant Injection Of Turbine Blade

Experimental investigations on the mixing characteristics of coolant injection with the leakage from turbine blade tip and stator wall (shroud) were conducted by a particle image velocimetry (PIV) system, at first. A three-time scaled profile of the GE-E3 blade was used as specimen. Two rows of cylindrical film-cooling holes with 1.5mm diameter were arranged in the blade tip. One row with 5 holes was placed in pressure side just below groove floor, and the other with 11 holes was equidistantly arranged on the tip along mid camber line. To observe the effect of the coolant injection from different rows on the leakage flow, several typical velocity fields were captured by the PIV system, and the mixing characteristics were discussed. To estimate quantitatively the reduction of the tip leakage rate caused by the coolant injection, numerical investigations on the leakage mass rate were carried out by the commercially available software CFX 11.0 and the previous experimental results were used as a data source to validate the turbulence model and computational program. The numerical and experimental results indicate that the position of film holes is an important factor that influences the mixing characteristics of the tip leakage with the injected coolant. The coolant injection from the film hole at the pressure side can reduce the impingement intensity of the mainstream to the pressure side in the upstream of the film holes, is more effective to decrease the mass rate of the leakage flow, and a larger coolant blowing ratio corresponds to a higher resistance to the leakage flow and a smaller leakage mass rate.