Numerical Analysis of Film Cooling Flow Over Flat Plate With Convective Heat Transfer Conditions

Abstract

Abstract Film cooling is a systematically designed and widely used technique in cutting-edge gas turbine engines to reduce the surface temperature of gas turbine blades and endwalls, thereby lowering material temperature. Cooling air is emitted from the film holes to protect the external surface, which is exposed to high temperatures from the mainstream gas. As a result, the flow physics of cooling air mixing with the mainstream is critical, and it remains difficult for gas turbine designers to improve cooling efficacy due to the complexity of heat convection phenomena. This paper presents a numerical study onto problems of convective heat transfer in film cooling flow over a flat plate model using 3D computational fluid dynamics (CFD) available in STAR CCM+. The SST k-ω turbulence model and the realizable k-ε turbulence model with two-layer all y+ wall treatment are taken into consideration. To solve the problems, the flat plate surface is subjected to adiabatic (Cases 1-2) and constant heat flux conditions of 500 and 1000 W/m2 (Cases 3-6, respectively). The study is conducted at the density ratio (DR) of 1.2 and blowing ratios (BRs) of 0.3 and 0.6. Numerical solutions for both conditions are presented in terms of adiabatic film effectiveness (ηad), dimensionless temperature (θ), and Nusselt number (Nu). Based on a comparative analysis of adiabatic and heat flux conditions, the results show that both the centerline and laterally adiabatic film effectiveness at the two BRs decrease streamwise. At the same BR, the dimensionless temperature values are lower at 1000 W/m2 than at 500 W/m2. This includes less film coverage in the downstream. At BR = 0.6, increasing heat flux from 500 W/m2 to 1000 W/m2 significantly reduces film coverage size in both streamwise and spanwise directions.