Numerical Investigation Of Impingement Cooling And Film Cooling For Blades In High Temperature Gas Turbines

With more and more gas turbines being widely used for aircraft propulsion, sea-based ship propulsion and land-based power generation, it is extremely important to increase the turbine thermal efficiency. Based on the principle of Brayton cycle for gas turbines, increase in turbine inlet temperature can increase turbine thermal efficiency and power generation. Currently, the turbine fan F119-PW-110has a turbine inlet temperature of about1600℃, but it is still far lower than the requirement of advanced turbines which require the temperature should be of about2200℃Considering the gas temperature is far beyond the allowable metal melting points, new thermal resistant material and advanced cooling technologies should be developed and applied. Compared with the contribution of raised turbine inlet temperature by developing new thermal resistant material, utilization of advanced cooling technology benefits more. Impingement cooling and film cooling are two of the most effective cooling ways. It deserves more attention. This thesis is using numerical methods to investigate the flow field and heat transfer characteristics of impingement and film cooling on a gas turbine blade working under high temperatures. It consists of two parts:Part I Impingement cooling in laminated platesIn this part, the work was concentrated on the study of impingent cooling and film cooling in the laminated plates which are used in turbine blades and combustor liners. Prior to the numerical simulation, the best turbulence model was chosen through the comparison of the flow fields by numerical simulation with PIV results and further validated via the comparison of the surface temperature of laminated plates with Infrared measurements. It was found that the Shear Stress Transport k-co (SST k-ω) turbulence model agreed best with the experimental data. Hence, this model was adopted for the following laminated plate cooling analyses. Firstly, the fluid-thermal coupled calculation method involving both fluid and solid regions was applied to discuss the effects of factors including, number ratio of impingement holes to ribs to film holes, ribs arrangement and inclined angles of film hole on film cooling performance and press losses of laminated plates. Secondly, a one-way coupled method, with the assumption that the deformation of the plates caused by thermal stress is small and it has no effect on the temperature filed in the solid and no change to the flow fields in and around the plate, was adopted to calculate thermal stress distribution in the laminated plates using the temperature as the body load obtained directly from CFD. After that, a Goodman-diagram method is used to assess the fatigue characteristics of the plate. Lastly, the method of combining design of experiments and numerical simulation is used to analyze the influences of film hole inclined angle, diameter of rib, rib arrangement, height of ribs, and blowing ratio on the laminated cooling performance and pressure losses, which is valuable for helping design an optimal plate.Part II Film cooling on transonic gas turbine rotorsIn this part, a one-stage high load transonic turbine for high efficient energy engine made by Pratt&Whitney was chosen for investigating the effects of stator-rotor interaction on the aerodynamic characteristic and film cooling performance on the rotor under the turbine design condition. Since the flow features in the turbine passages are significantly different from thoese of laminated plates, it is again necessary to compare and choose an appropriate turbulence model. Due to the lack of experimental data of the blade at turbine representative conditions with film cooling, the static pressure distributions for flow passing through the stator and rotor cascades, and a convergent-divergent nozzle are referenced for comparison. Through the comparison, the Realizable k-s turbulence was chosen over other models And this model was applied to futher discuss the effects of trailing edge coolant injection on the flow field in a rotor cascade, and film cooling characteristics on the stator in the stator cascade. After that, a2D analysis of the effects of stator-rotor interaction on the pressure distribution and film cooling performance on the rotor at the turbine mid-span followed. And then it was concluded by discussing the effects of using twisted blade on the flow features in the rotor passage and film cooling performance on the rotor under three blowing ratios.