A series of experiments were carried out to measure the effects of convex surface curvature on film cooling. In the first series of experiments cooling holes were positioned along the vane such that their non-dimensional curvature parameter, 2r/d, was matched. Single row of holes with the same diameter were placed at high and moderate curvature position along a turbine vane resulting in 2r/d = 28 and 40, accordingly. A third row of holes was installed on the vane at the same location as the moderate curvature row with a larger hole diameter, resulting in 2r/d = 28, matching the high curvature row. Adiabatic temperature measurements were then carried out for blowing ratios of M = 0.30 to 1.60 tested at a density ratio of DR = 1.20. The results indicated that there was some scaling of performance present with matching 2r/d, but there was not an exact matching of performance. The second series of experiments focused on the effects of a changing surface curvature downstream of injection. Two row of holes were positioned along the vane surface such that the local radius of curvature and hole diameters were equivalent, with one row positioned upstream of the maximum curvature point and the other downstream of the maximum curvature point. Adiabatic temperature measurements were carried out for blowing ratios of M = 0.30 to 1.60 and tested at a density ratio of DR = 1.20. The results show that the change in curvature downstream plays a significant role in the performance of film cooling and that the local surface curvature is insufficient in capturing its effects. Additional experiments were carried out to measure the effects of the approaching boundary layer influence on film cooling as well as the effect of injection angle at a weakly convex surface. / text

The current demands for higher performance in gas turbine engines can be reached by raising combustion temperatures to increase thermal efficiency. Hot combustion temperatures create a harsh environment which leads to the consideration of the durability of the combustor and turbine sections. Improvements in durability can be achieved through understanding the interactions between the combustor and turbine. The flow field at a combustor exit shows non-uniformities in pressure, temperature, and velocity in the pitch and radial directions. This inlet profile to the turbine can have a considerable effect on the development of the secondary flows through the vane passage. This thesis presents a computational study of the flow field generated in a non-reacting gas turbine combustor and how that flow field convects through the downstream stator vane. Specifically, the effect that the combustor flow field had on the secondary flow pattern in the turbine was studied. Data from a modern gas turbine engine manufacturer was used to design a realistic, low speed, large scale combustor test section. This thesis presents the results of computational simulations done in parallel with experimental simulations of the combustor flow field. In comparisons of computational predictions with experimental data, reasonable agreement of the mean flow and general trends were found for the case without dilution jets. The computational predictions of the combustor flow with dilution jets indicated that the turbulence models under-predicted jet mixing. The combustor exit profiles showed non-uniformities both radially and circumferentially, which were strongly dependent on dilution and cooling slot injection. The development of the secondary flow field in the turbine was highly dependent on the incoming total pressure profile. For a case with a uniform inlet pressure in the near-wall region no leading edge vortex was formed. The endwall heat transfer was found to also depend strongly on the secondary flow field, and therefore on the incoming pressure profile from the combustor. / Master of Science

The aim of this thesis is to provide research into turbocharger regulation, and analyze the force load of vanes in the VNT mechanism of Garrett turbocharger by CFD simulation. In the thesis there is one model with two different mesh densities. It describes the relevance of supercharging vehicle engines and the kinds of supercharging aggregates in the introduction. Then, the thesis is divided into two chapters. The first chapter provides research, describing primary principle of supercharging, turbocharger construction and kinds of air regulation. The practical part of the thesis solves the force load of VNT mechanisms. It was necessary to optimalize the 3D Garrett turbocharger model, create two meshes with different element densities, specify boundary conditions and analyse the results of both cases. A general description of solved problems, comparison of results of force load vanes and propose simplifying and verifying the CFD calculation are included in the conclusion.

Coal gasification and combustion can introduce contaminants in the solid or molten state depending on the gas clean up procedures used, coal composition and operating conditions. These byproducts when combined with high temperatures and high gas stream velocities can cause Deposition, Erosion, and Corrosion (DEC) of turbine components downstream of the combustor section. The objective of this dissertation is to use computational techniques to investigate the dynamics of ash deposition in a leading edge vane geometry with film cooling. Large Eddy Simulations (LES) is used to model the flow field of the coolant jet-mainstream interaction and the deposition of syngas ash in the leading edge region of a turbine vane is modeled using a Lagrangian framework. The three row leading edge vane geometry is modeled as a symmetric semi-cylinder with a flat afterbody. One row of coolant holes is located along the stagnation line and the other two rows of coolant holes are located at ±21.3° from the stagnation line. The coolant is injected at 45° to the vane surface with 90° compound angle injection. The coolant to mainstream density ratio is set to unity and the freestream Reynolds number based on leading edge diameter is 32000. Coolant to mainstream blowing ratios (B.R.) of 0.5, 1.0, 1.5, and 2.0 are investigated. It is found that the stagnation cooling jets penetrate much further into the mainstream, both in the normal and lateral directions, than the off-stagnation jets for all blowing ratios. Jet dilution is characterized by turbulent diffusion and entrainment. The strength of both mechanisms increases with blowing ratio. The adiabatic effectiveness in the stagnation region initially increases with blowing ratio but then generally decreases as the blowing ratio increases further. Immediately downstream of off-stagnation injection, the adiabatic effectiveness is highest at B.R.=0.5. However, in spite of the larger jet penetration and dilution at higher blowing ratios, the larger mass of coolant injected increases the effectiveness with blowing ratio further downstream of injection location. A novel deposition model which integrates different sources of published experimental data to form a holistic numerical model is developed to predict ash deposition. The deposition model computes the ash sticking probabilities as a function of particle temperature and ash composition. This deposition model is validated with available experimental results on a flat plate inclined at 45°. Subsequently, this model was then used to study ash deposition in a leading edge vane geometry with film cooling for coolant to mainstream blowing ratios of 0.5, 1.0, 1.5 and 2.0. Ash particle sizes of 5, 7, 10μm are considered. Under the conditions of the current simulations, ash particles have Stokes numbers less than unity of O(1) and hence are strongly affected by the flow and thermal fields generated by the coolant interaction with the main-stream. Because of this, the stagnation coolant jets are successful in pushing and/or cooling the particles away from the surface and minimizing deposition and erosion in the stagnation region. Capture efficiency for eight different ash compositions are investigated. Among all the ash samples, ND ash sample shows the highest capture efficiency due to its low softening temperature. A trend that is common to all particle sizes is that the percentage capture efficiency is least for blowing ratio of 1.5 as the coolant is successful in pushing the particles away from the surface. However, further increasing the blowing ratio to 2.0, the percentage capture efficiency increases as more number of particles are transported to the surface by strong mainstream entrainment by the coolant jets. / Ph. D.

In the United States, natural gas turbine generators account for approximately 7% of the total primary energy consumed. A one percent increase in gas turbine efficiency could result in savings of approximately 30 million dollars for operators and, subsequently, electricity end-users. The efficiency of a gas turbine engine is tied directly to the temperature at which the products of combustion enter the first stage, high-pressure turbine. The maximum operating temperature of the turbine components’ materials is the major limiting factor in increasing the turbine inlet temperature. In fact, current turbine inlet temperatures regularly exceed the melting temperature of the turbine vanes through advanced vane cooling techniques. These cooling techniques include vane surface film cooling, internal vane cooling, and the addition of a thermal barrier coating (TBC) to the exterior of the turbine vane. Typically, the performance of vane cooling techniques is evaluated using the adiabatic film effectiveness. However, the adiabatic film effectiveness, by definition, does not consider conjugate heat transfer effects. In order to evaluate the performance of internal vane cooling and a TBC it is necessary to consider conjugate heat transfer effects. The goal of this study was to provide insight into the conjugate heat transfer behavior of actual turbine vanes and various vane cooling techniques through experimental and analytical modeling in the pursuit of higher turbine inlet temperatures resulting in higher overall turbine efficiencies. The primary focus of this study was to experimentally characterize the combined effects of a TBC and film cooling. Vane model experiments were performed using a 10x scaled first stage inlet guide vane model that was designed using the Matched Biot Method to properly scale both the geometrical and thermal properties of an actual turbine vane. Two different TBC thicknesses were evaluated in this study. Along with the TBCs, six different film cooling configurations were evaluated which included pressure side round holes with a showerhead, round holes only, craters, a novel trench design called the modified trench, an ideal trench, and a realistic trench that takes manufacturing abilities into account. These film cooling geometries were created within the TBC layer. Each of the vane configurations was evaluated by monitoring a variety of temperatures, including the temperature of the exterior vane wall and the exterior surface of the TBC. This study found that the presence of a TBC decreased the sensitivity of the thermal barrier coating and vane wall interface temperature to changes in film coolant flow rates and changes in film cooling geometry. Therefore, research into improved film cooling geometries may not be valuable when a TBC is incorporated. This study also developed an analytical model which was used to predict the performance of the TBCs as a design tool. The analytical prediction model provided reasonable agreement with experimental data when using baseline data from an experiment with another TBC. However, the analytical prediction model performed poorly when predicting a TBC’s performance using baseline data collected from an experiment without a TBC. / text