NUMERICAL STUDY ON THE CONSOLE HOLE FILM COOLING PERFORMANCE WITH VARIED HOLE INLET SHAPE

The shaped holes are widely used to improve the film cooling performance in gas turbine thermal protection. Among them, the converging slot-hole (console) is a well-performed shaped hole, but its cooling effectiveness can be severely deteriorated near the centerline at a small incident degree. In this paper, the geometry of the console, particularly the inlet shape, was adjusted using numerical simulation methods to improve the cooling performance of the console. Different consoles with varying inlet widths but the same inlet area were tested on a flat plate with an injection angle of 30 degrees, and the blowing ratios ranged from 0.5 to 2.0. The mainstream Reynolds number was set to 10000 based on the film hole inlet diameter, and the density ratio was 1.5. The RANS equations were closed by the RNG k-ε model and the structured grid consisting of 7.64 million cells was adopted to provide a relatively accurate predictive result. It is found that kidney vortices near the centerline of the typical console are responsible for the severe deterioration in cooling performance, resulting in the loss of coolant protection in the downstream centerline region and exhibiting trace bifurcation. These kidney vortices mainly originate from flow separation generated when coolant flows from the plenum into the hole. Widening the inlet width of the console increases the spacing between kidney vortices within the hole. This reduces the mutual induction between the vortices and suppresses their development within the hole, ultimately eliminating the kidney vortices along the downstream centerline. In the flow field of the console with a larger inlet width, the predominant structures are anti-kidney vortices. Although this leads to a slightly shorter length of coolant trace, an appropriate increase in the console inlet width can increase the area-averaged cooling effectiveness by up to 117.3% within the downstream range of 40D.