Effects of Hole Geometry on Film Coverage and Cooling Capability

A numerical simulation was conducted to investigate the film effectiveness of film cooling using a single hole with two types of geometry: cylindrical hole with constant cross section and shaped hole with conically widened exit. The film cooling jet was injected through a 30° inclined hole to the surface and with lateral directions of 0°, 45° and 90°, for the blowing rates of 0.5, 1.0 and 2.0, respectively. The film effectiveness analyzing method was discussed based on the simulation. An effort is performed to form a more comprehensive evaluation technology with the definition of three parameters, film coverage, average cooling capability and uniformity of film. The results indicate that the film quality of compound angle injection depends on the equilibrium between the lateral and axial momentum components of coolant jet, and that the film protects the surface effectively at moderate blowing rate. The use of a shaped hole shows noticeable advantage.