Investigation On Closed-Loop Steam Cooling Method Of A Gas Turbine Rotor Blade

As one of the most important power machines, gas turbine is widely used in various fields such as aircraft propulsion, power generation and so on. With the increase of turbine inlet temperature, the performance of gas turbine can be improved. Due to the temperature limitation of high temperature alloy used for the manufacture of turbine vane and blade, advanced cooling technology is necessary for the turbine with the increased inlet temperature. In closed-loop steam cooling, the blade is cooled by the superheated steam through a closed-loop channel. Compared to open-loop air cooling, steam cooling reduces the quantity of cooling air and avoids the mixing loss, so it can improve the performance of turbine obviously. However, few technical details about closed-loop steam cooling are revealed in open literature. This dissertation aims to achieve the replacement of air cooling configuration in a heavy-duty gas turbine rotor blade with closed-loop steam cooling.Based on the experimental data of the C3X vane, conjugate heat transfer simulations are carried out by using CFX software. The influence of several factors such as turbulence models on the numerical results was investigated. The distributions of pressure on the vane surface computed by using four turbulent models demonstrated little difference and matched well with the experimental data. In contrast, the prediction of heat transfer on the vane surface was greatly affected by turbulent models. Among the four turbulence models applied, SST γ-o model, which accounts for the transition from laminar to turbulent flow, could predict relatively accurately the flow and heat transfer characteristics of the vane, though there are still some problems in dealing the pressure side transition. The inlet turbulence intensity of coolant affected the flow development and the conjugate heat transfer results of the vane greatly. When heat transfer coefficient correlations were applied to the cooling channel thermal conditions, it could save the calculation resource. But the computed heat transfer and temperature distributions on the vane surface could not match the data well due to the larger heat transfer coefficients calculated by using the correlations.The flow and heat transfer of the turbine rotor blade were different from the turbine vane blade due to the existence of tip clearance. After verifying the simulation method with the experimental data of GE-E°engine HP turbine blade, the influences of four tip configurations on the tip leakage flow and heat transfer of a heavy-duty gas turbine rotor blade were analyzed in the rotating working condition. It’s showed that the different tip configurations changed the leakage flow patterns and the pressure distribution on the suction surface near the tip region, which also changed the flow losses in the passage. Among the four tip configurations, the full squealer tip resulted in the lowest total pressure loss and the minimum leakage flow. The suction side squealer tip resulted in the lowest overall heat transfer coefficient on the blade tip. The heat transfer coefficient distributions of the blade also showed that heat transfer near the tip was the strongest for the whole blade.A conjugate heat transfer simulation was performed for the original air-cooled turbine rotor blade. The flow near the tip region and heat transfer characteristics of the blade was analyzed. Numerical results showed that the blade can be well protected by the air-cooled configurations. According to the distributions of thermal loading around the blade, an initial steam cooling configuration was proposed for the blade. After analyzing the cooling efficiency of the initial configuration, the corresponding modification designs were provided. It’s showed that the gas turbine rotor blade could be cooled sufficiently by the final closed-loop steam cooling scheme. In addition, compared to the original air-cooled design, the steam-cooled design improved the performance of the turbine.