Numerical and experimental study of flow in a gas turbine chamber.
This thesis examines the cooling performance and the flow on a gas turbine blade. Numerical and experimental methods are described and implemented to assess the influence of film cooling effectiveness. A modem gas turbine blade geometry has been used. The blade is considered as a solid body with the blade cross section from hub to shroud varying with a degree of skewness. Computational Fluid Dynamics (CFD) is employed to assess blade film cooling effectiveness via simulation of the effect of varying blowing ratios (BR=1, 1.5 and 2), varying coolant fluid temperature (Tc=153 K and Tc=287.5 K), various angles of injection (35°,45° and 60°), increasing the number of cooling holes (32 and 42) and increasing the cooling holes diameter (D= 0.5 mm and 1mm). A full three-dimensional finite-volume method has been utilized in this study via the FLUENT 6.3 code with a k-epsilon (RNG) turbulence model.Results of the CFD models were carefully validated by studying aerodynamic flow and heat transfer in turbine blade film cooling performance. A two-dimensional channel and NACA 0012 airfoil were selected to investigate turbulence effects. The solution accuracy is assessed by carrying out a sensitivity analysis of mesh type and quality effects with enhancement wall treatment and standard wall function effects also addressed for turbulent boundary layers. In this study, four different turbulence models were utilized (S-A, mu-epsilon, (RNG), and (SST) mu-o). The computations were compared with available Direct Numerical Simulation (DNS) and experimental data. Good correlation was observed when using the RNG turbulence model in comparison with other turbulence models.Film cooling effectiveness and heat transfer along a flat plate has been analyzed for four different plate materials, namely steel, carbon steel, copper and aluminum, with 30° angle of injection. The cooling holes arrangement was simulated for a hole diameter of D=1 mm and different sections of the blade showing cooling effectiveness and heat transfer characteristic variation with increasing (BR = 0.5, 1). Furthermore a symmetrical single hole at 35° angle of injection was studied both the solid and shell plate cases. Cooling effectiveness numerical results were compared with available experimental data and the effect of material thermal properties for the solid plate on cooling performance evaluated. Numerical modeling has clearly identified that there is no benefit in reducing the number of holes as this decreases film cooling effectiveness. The experimental investigation showed the effect of increasing volumetric flow rate V°=1000, 800 and 600 cm3/min, as a term of the blowing ratio (BR) and angle of injection (35°,45° and 60°) for a modem gas turbine blade specimen using Thermal Paint Technology (TPT) and a Thermal Wind Tunnel (TWT). Both methods confirmed that the blade specimen with angle of injection of 45°, blowing ratio of BR=2 (which corresponds to 1000cm[3]/min), cooling holes diameter D=lmm and 42 holes developed a better film cooling effectiveness compared with the 35° and 60° cases. In addition TPT is a sufficient and relatively easy method for evaluating temperature distributions in experimental studies.
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Sheffield Hallam University (United Kingdom).