可倾/固定密封内流体激振力计算与试验比较

Calculation and Experimental Comparison of Fluid Induced Force Between the Titling Pad Seal and the Fixed Pad Seal

提出可倾式密封减小密封内气流激振力的理论,其本质在于通过密封块的自适应摆动从而改变流场。利用ANSYS CFX建立可倾密封流固耦合分析模型,计算时应用动网格的方法来实现密封块的自适应摆动。计算并比较了两种形式密封内气流激振力随入口压力、转子偏心以及转速的变化情况。结果表明,随着三个参数的增大,密封内气流激振力均普遍增大。在所有工况下,可倾密封气流激振力均小于固定密封气流激振力,两种密封气流激振力的差值随三个参数的增大而增大。设计密封汽流激振力的试验装置,应用传递函数法识别了密封气流激振力,通过共振的方法提高了识别精度。试验证实了计算得到的现象。对于现代超临界、超超临界机组,两种密封内气流激振力的差别预计会更大。

A new theory to reduce fluid induced force in seal is presented. The main idea is to change fluid field by the automatic tilting motion of seal pad. Using ANSYS CFX, the fluid-solid coupling model is set up. The tilting motion of seal pads are realized by mesh deformation method. Calculation results of seal force under different rotation speed, eccentric ratio and pressure are given. Comparison between the two kinds of seal shows that force increase with the increase of three parameters. In total cases, force of the tilting pad seal is smaller then force of the fixed pad seal. The difference becomes larger in case of large pressure, rotation speed and eccentric ratio. The test rig is set up. Seal force is identified by using transfer function method. Influence of seal force is enlarged to improve accuracy by test near the resonance region. The calculation results are verified by experiment. The seal force difference between the two kinds of seal may be large for the modem super critical turbines due to the large inlet pressure.