透平级气动及运行参数对轮缘密封封严性能影响的数值研究

Effects of Aerodynamic and Operational Parameters on Sealing Performance of Turbine Rim Seal

以燃气轮机中常用的径向轮缘密封为研究对象,系统深入地研究了透平级压比、转速等参数的改变对轮缘密封封严性能的影响规律。通过求解三维RANS方程组和SST湍流模型,在基于添加示踪流体湍流输运附加变量控制方程的基础上,首先计算得到了4种透平进出口压比、4种透平级转速工况条件下的典型径向轮缘密封的封严效率;其次,对比了不同动静叶片周向相对位置对轮缘密封封严性能的影响。研究结果表明:当透平级压比和转速变化时,将通过影响动叶前缘压力势场分布来影响轮缘密封封严性能;随着压比的增加,周向压力不均匀程度变大,封严效率降低,入侵强度明显强化;当转速由小到大变化时,周向压力不均匀程度得以改善,因此轮缘密封的封严效率得以提高;动静叶相对位置变化会引起静叶尾迹与动叶前缘势场的相对干涉,导致轮缘密封封严效率出现变化,随着动叶的旋转,盘内的入侵流呈现出周期性的强化与减弱。

Three-dimensional unsteady Reynolds-averaged Navier-Stokes （URANS） equations coupled with a fully-developed shear stress transport （SST） turbulent model were used to investigate the sealing performance of rim seal. The sealing behaviors of conventional radial rim seal at different pressure ratios and rotational speeds were numerically predicted. Based on solving the turbulence transport governing equation for additional variable used for tracing fluid, the sealing effects of conventional radial rim seal were obtained at four different pressure ratios and rotational speeds. And then the investigation on the effect of relative location of rotor and stator on the sealing performance of the radial rim seal was carried out. Numerical results showed that pressure ratio and rotational speed are the key factor influencing the seal performance of radial rim seal. Pressure ratios and rotational speeds change the sealing efficiency by influencing the blade leading edge＇s potential field. The seal efficiency decreases with the pressure ratio because of enhancing non-uniformity of the circumferential pressure field. And the seal efficiency increases with the rotational speed because of the improvement on the non-uniformity of circumferential pressure field. The change of relative position between vane blade and rotor blade would induce the variation of interaction between the pressure potential fields at vane blade wake and rotor blade leading edge, and hence influencing the seal efficiency. With the blade rotating, the ingestion in wheel space presents periodic enhancing and weakening.