Numerical investigation of rectangular twisted hole on film cooling for gas turbine blades

This paper investigates a new method of film cooling using swirling coolant flow through a rectangular twisted film cooling holes with spirally corrugated tube. Two different air flows with different in temperatures were used in this study. Throughout the investigation, blowing ratio was varied from 0.5 to 2.0 with several configuration of rectangular twisted angle of 0°, 90°, 180°, 270° and 360°. The results of cooling effectiveness obtained were compared against a standard untwisted tube. Results show that the overall thermal effectiveness improved significantly when the temperature difference between the air flows is at 25 degrees. Such improvement is supported by heat transfer enhancement that obtained from 19% to 57%. Based on the findings, the study concludes that using a simple geometry of film cooling hole with specific twisted configuration may result to improve the convective heat transfer coefficient