涡轮径向轮缘密封非定常燃气入侵和封严效率的数值研究

Numerical Investigations on Unsteady Gas Ingestions and Sealing Effectiveness of Turbine Radial Rim Seal

关键词:  燃气轮机  径向轮缘密封  燃气入侵  封严效率  数值模拟

Key words:  Gas turbine  Radial rim seal  Gas ingestion  Sealing effectiveness  Numerical simulation

摘要:

为防止燃气入侵涡轮盘腔，提高运行安全性，对盘腔和轮缘密封间隙内非定常流动机理进行了深入研究。采用数值求解三维URANS（Unsteady Reynolds Averaged Navier-Stokes）和SST湍流模型的方法，研究了涡轮径向轮缘密封的非定常燃气入侵和封严效率。数值计算的径向轮缘密封的封严效率和环量比与实验数据吻合一致，验证了数值方法的可靠性。分析了6种冷气流量下径向轮缘密封的非定常压力分布、封严效率和燃气入侵与冷气出流特性。研究表明：冷气流量的增加阻止了径向轮缘密封处的燃气入侵和强化了冷气出流，径向轮缘密封盘腔内的封严效率随着冷气流量的增加而增加；动盘附近的封严效率高于静盘；入侵燃气基本被限制在径向轮缘密封的间隙区域。径向轮缘密封间隙出口处的主流周向时均压力随着冷气流量的增加而增加，周向时均压力最大值与最小值的差值随着冷气流量的增加而减小。当动叶前缘与静叶尾缘距离较近且不断靠近的过程，主流周向压力最大值与最小值的差值增大，动静叶相分离的过程周向压力最大值和最小值的差值减小。在静叶和动叶间非定常干涉作用下，轮缘密封间隙出口区域主流周向压力最大值与最小值差值较大时刻的主流低压区域具有优良的封严效率，同时高压区域的燃气入侵导致封严效率降低。

Abstract:

In order to prevent gas ingestion and improve the operation safety， the unsteady flow mechanism in cavity and rim seal gap was studied. The unsteady gas ingestion and sealing effectiveness of the turbine radial rim seal was numerically investigated using three-dimensional unsteady Reynolds-Averaged Navier-Stokes （URANS） solutions and SST turbulence model. The numerical sealing effectiveness and swirl ratio of the turbine radial rim seal were well agreement with the experimental data. The accuracy of the numerical method was validated. The unsteady static pressure distribution， sealing effectiveness， gas ingestion and coolant egress of the turbine radial rim seal at six different coolant flow rates were analyzed. The numerical results show that increase of the coolant flow rate prevents the gas ingestion and strengthens the coolant egress. The sealing effectiveness of the turbine radial rim seal cavity increases with the coolant flow rate increasing. The sealing effectiveness near the rotational disk is higher than that of the stationary disk. The ingestion gas is almost restricted within the clearance region of the turbine radial rim seal. Circumferential time averaged static pressure of the mainstream at the radial rim seal exit increases with the coolant flow rate increasing. The maximum circumferential static time averaged pressure difference decreases with the coolant flow rate increasing. The maximum circumferential static pressure difference increases when the leading edge of the rotational blade closes to the trailing edge of the stationary vane and decreases during the separation process between the stationary vane and rotational blade. The high sealing effectiveness of the radial rim seal in the low static pressure regions at the times of the larger maximum circumferential static pressure difference is obtained. In addition， the sealing effectiveness decreases due to the gas ingestion in the high static pressure regions.