Numerical Analysis for Film Cooling Performance Under Different Jet Design Criteria

Abstract

Cooling gas turbine blades is a crucial technique to allow higher turbine inlet temperatures. A higher turbine inlet temperature allows boosting gas turbine efficiency, which reduces fuel consumption. One of the main cooling techniques of the turbine blades is film cooling where a relatively low air temperature is used to form a blanket of cool air around the blade to shield it from high temperature gases. Many complex interrelated geometry and flow parameters affect the effectiveness of the film cooling. The complex interrelations between these parameters are considered the main challenge in properly understanding the effect of these parameters on film cooling. Testing such cooling techniques under actual engine conditions is even more challenging due to difficulty of installing proper instrumentations. Numerical techniques are viable analysis techniques that are used to better understand film cooling techniques. In this study, a simplified 2D film cooling jet blown from the slot jet is investigated under multiple variable parameters, mainly, the blowing ratio, jet angle, density ratio and centrifugal force. The performance of the film cooling is reported using local and average adiabatic film effectiveness. The main contribution of this study is exploring the effect of the centrifugal force and wall material selection using conjugate heat transfer on film cooling effectiveness. The centrifugal force reduces the overall adiabatic film effectiveness. A correlation between the blowing ratio, density ratio and injection angle is developed in this work. The highest film cooling performance was founded at a blowing ratio of 0.8, an injection angle of 30° and density ratio of 1.2.