Effect of Vane/Blade Interaction for a Cooled Turbine Blade — Part I: Comparison of Experimental and Numerical Results

Abstract

Flow fields in axial gas turbines are highly complex and unsteady due to the interactions of rotating and stationary components. The current study incorporates experimental and computational analyses of a modern, rotating high-pressure turbine stage to examine the nature and effects of unsteadiness at vane passing scales. Increased knowledge of the unsteady flow field and its impacts on heat transfer will help engineers to produce higher quality thermal predictions of gas turbine components with efficient use of computing resources. Computational research was carried out using single sector simulations using steady, sliding mesh, and harmonic balance treatments. Simulation results are compared to measurements of heat flux and pressure on the rotating airfoils of a cooled turbine stage operating at design corrected conditions. Unsteady analysis of experimental and computational results highlights the importance of unsteady considerations in gas turbine research. Simulation results of unsteady pressure and heat transfer linked to vane passing perform well in some regions of the blade, but single sector computations cannot predict frequencies below vane passing frequency. It is therefore important to perform experiments and simulations in turbine representative environments. Comparisons between results from the various computational models and experimental data form a basis for evaluating the benefits and drawbacks for each type of model treatment. Harmonic balance and sliding mesh simulations both increase the level of agreement between heat transfer data and results to within unsteadiness bounds, and each tends to have specific advantages. Harmonic balance simulations are particularly well equipped for comparisons in the frequency domain, but nearly double the memory requirement, making them more expensive to perform. Part I of this paper focuses on the computational approaches implemented and how they compare to experimental results. Part II investigates the unsteady mechanisms that cause differences between steady and time-accurate solutions, as well as how they impact the flow over the rest of the airfoil.