Film cooling performance and flow field of compounded double jet holes with trench

Abstract

Film cooling performance of a novel double jet configuration is numerically analysed. The proposed scheme has a primary compound angle hole along with a secondary hole compounded in the laterally opposite direction. The primary hole is provided with a trench at the coolant hole exit. Numerical analysis is performed using RANS equations along with standard k-ω turbulence model. The numerical scheme is validated through the excellent agreement between the available experimental data for tangential, compound, and crater designs having similar primary hole geometric parameters. It is seen that the proposed compounded double jet trench design (DJT) combines the advantages of compound angle, double jet and trenched configurations and provides better lateral and uniform coolant distribution, reduced jet lift off, and higher coolant attachment in the stream wise direction. The vortex mechanisms responsible for the coolant spread in near-hole and down stream regions are identified. The various flow structures that are responsible for higher effectiveness are compared with other configurations. The effect of free stream turbulence at various blowing ratios is studied and found that the increase of turbulence produced significant increase in lateral effectiveness at higher blowing ratios. This effect is predominant at far downstream locations of the coolant exit plane.