CFD based parametric investigations of film cooling effectiveness for various coolant injection hole geometries and injection angles

Computational analysis on film cooling effectiveness over a flat plate using different coolant injection hole geometries are reported. The designed computational setup and flow physics are suitably validated against the existing experimental results for an injection angle of 30°. The present study reports and compares the degree of film cooling effectiveness obtained by the different orientations of the coolant injection holes and their geometry, hole arrangements in the rows and number of rows. The computational domain was designed using Ansys Fluent. The blowing ratio is systematically ranged between 0.67 and 1.67. The performance of a given film cooling scheme is reported in terms of centreline (ηcl) and spatially averaged (η_sa) adiabatic effectiveness. It is observed that for single hole configuration, the semi-elliptic geometry increases the ηcl by ~66.67% up to x/D(ratio of downstream distance from hole to diameter of hole) = 50 at lower blowing ratios (0.67 and 1.00) and by ~50% up to x/D=100 at higher blowing ratios (1.33 and 1.67). For ηsa, an increment of ~200% and ~60% is achieved for all blowing ratios using the triangular and semi-elliptic geometries, respectively. For the multiple row arrangements, the two staggered rows delivered an increment in ηcl of ~77% up to x/D=50 and ~54% up to x/D=100. The two staggered configurations at 0° gave the highest effectiveness increment of ~177% up to x/D=50 while it was ~100% for up to x/D=100. Results indicate that the triangular geometry shows the highest values of the film cooling effectiveness, and a semi- elliptic geometry utilizes ~50% of the coolant mass flow than other coolant injection hole geometries while delivering higher effectiveness values.