Study of film cooling injection geometries: Measured flow and thermal fields with lateral, compound and in-line injection

Temperature field measurements taken with a traversing thermocouple are presented for compound angle injection with Φ = 45°. These are compared with data from lateral injection, Φ = 90°, and in-line injection, Φ = 0, cases. Near-wall values of these measurements, which are adiabatic effectiveness values, η, show the effect of Φ on film cooling performance. Complementary velocity field measurements, including streamwise and cross-stream velocity components, taken with triple-wire anemometry, are also presented for compound angle injection. These are compared with similar data for lateral and in-line injection cases presented in the literature. The main feature of the flow pattern with compound angle injection is the presence of an asymmetrical pair of counter-rotating vortices of unequal strength, the nature of which depends on the ratio of the momentum flux of the coolant and the mainstream and the injection angle, Φ. For compound angle injection, the stronger vortex appears to draw free stream fluid towards the wall, as with lateral injection, but to a lesser degree. Triple-sensor anemometry measurements also yield turbulent Reynolds stress distributions which allow discussion of anisotropy of turbulent transport. Eddy diffusion in cases of isotropic turbulence would follow the gradient diffusion model in which the shear stress vectors are perpendicular to the velocity gradients. Due to anisotropy, this is not the case over most of the flow field, however.