透平机械动密封动力特性数值方法研究

Numerical Method Study on Rotordynamic Characteristics of Turbine Machinery Dynamic Seals

密封动力特性系数是评价透平机械转子稳定性的重要参数。对现有密封动力特性数值方法进行了综述,为了比较分析不同的密封动力特性数值方法,分别建立了基于控制体方法的双控体求解模型和基于CFD方法的稳态旋转坐标系与瞬态转子平动、转子单/多频椭圆涡动求解模型,综合比较分析了控制体法、CFD稳态旋转坐标系法和CFD瞬态平动法、单/多频法之间的差异以及适用范围,研究了转子涡动频率对密封气流力和动力特性系数的影响。研究结果表明:控制体法求解速度较快,但求解精度较低,稳态旋转坐标系法只适用于转子做小轨迹同心涡动的求解模型,瞬态平动法求解速度较慢;瞬态单/多频法考虑了转子的涡动频率,更符合密封的实际工作情况;应用瞬态单/多频法得到的密封气流力变化频率与转子涡动频率相同,但气流力的相位滞后于转子涡动位移的相位;密封的直接刚度系数随着转子涡动频率的增加而增大,交叉刚度系数和阻尼系数的绝对值随着转子涡动频率的增加而减小。

The rotordynamic coefficients of seals are important parameters to evaluate the stability of the turbomachinery. The numerical methods of the existing seals rotordynamic characteristics were summarized,and two control volume model based on control volume method,and steady moving rotating frame and transient rotor translation, single/multi-frequency rotor whirling models based on CFD method were established to compare their differences and scopes of application. The effects of the rotor whirling frequency on the air force and rotordynamic characteristics were also studied. The research results show that, the control method has high solution speed,but its solution precision is slow. The steady moving rotating frame method need meet a condition that rotor motion is concentric whirl with a small orbit. The solution speed of transient translation method is slow. The change frequencies of air force obtained by transient single/multi-frequency methods are the same as the frequencies of the whirling motion of the rotor,but the phase of air force lag behind rotor whirl. Direct stiffness coefficients increase with the increase of the rotor whirling frequency,while the opposite trend for the absolute value of cross stiffness coefficients and damping coefficients.