Numerical Investigation of the Heat Transfer and the Flow Characteristics of a Cooled Turbine End Wall

Abstract

he end wall region of gas turbine blade is subjected to high thermal gradient and requires cooling. Film cooling is mainly used because it gives a protection against high temperature. This work deals with the numerical investigation of an end wall film cooling. The purpose of this study is to compare simulation to experiment results and to validate the CFD. This study starts with a literature review about the current end wall aerodynamic situation, heat transfer and cooling knowledge. Experiment was conduct by Robin Brakmann. This experimental study is compare to numerical simulation run with TRACE V8. The numerical approach uses the RANS and k-omega methods with a turbulent Prandtl constant of 0.9. The numerical results are also confronted to the data found in the literature review. Four other boundary conditions were tested to validate the model: wall function versus low Reynolds, k-omega turbulence model versus Menter SST k-omega, adiabatic walls versus isothermal walls and adiabatic walls versus heat transfer qw=20000W/m². Regarding the results of the simulations the model can be optimize. The comparison between experimental and numerical results is focus on the Influence of the outlet Mach number and the coolant mass flow. For the same Mach number increasing the coolant mass flow increases the adiabatic film cooling effectiveness. For the lowest coolant mass flow increasing the Mach number increases adiabatic film cooling effectiveness. For the biggest coolant mass flow increasing the Mach number decreases the adiabatic film cooling effectiveness. The validation of the model has allowed to determine an possible optimization of the model. With the low Reynolds wall treatment and isothermal wall the model is closer to the experiment.