Effect of Shaft Seal Leakage on IP First-stage Steam Cooling Performance of an Ultra-supercritical HIP Combined Steam Turbine

The effect of shaft seal leakage on intermediate-pressure (IP) first-stage steam cooling performance of an ultra-supercritical high & intermediate pressure (HIP) combined steam turbine was numerically investigated by coupled flow-field calculation and conjugated heat-transfer method, while the steam cooling characteristics were analyzed and compared respectively under no steam cooling, steam cooling and leakage steam cooling conditions. Results show that turbine stage efficiency at first stage of IP cylinder decreases with the rise of shaft leakage flow rate; for a shaft leakage flow rate of 9.68 kg/s, the turbine stage efficiency would be decreased by 0.68% in comparison with the zero leakage case; the cooling mechanism of leakage steam on the first-stage components is same as that of the cooling steam, and their cooling effects are different due to their different flow rates and temperatures; compared with the steam cooling condition, the cooling effect on blade root by steam mixture from both shaft leakage and coolant flow weakens with the rise of leakage flow rate, resulting in increased temperature but reduced temperture gradient at blade root.