反旋流对密封静力与动力特性影响的理论与试验研究

设计加工无/有反旋流共4种密封结构,从理论与实验两个方面研究反旋流对密封静力与动力特性的影响规律。建立反旋流密封静力特性CFD模型,理论分析反旋流对密封间隙流体切向速度、周向压力分布以及泄漏特性的影响;设计搭建反旋流密封动力特性试验台,试验测试无/有反旋流密封的泄漏特性,应用不平衡同频激励法试验研究反旋流对密封动力特性的影响。研究结果表明:反旋流可减小密封间隙流体的切向速度,进而降低密封间隙流体的周向压力差,且密封间隙流体周向压差随切向速度的减小而降低,这是反旋流抑制密封气流激振力的主要原因;密封的泄漏量随进出口压比的增加而增大,两者近似呈线性关系;与无反旋流密封相比,反旋流密封增加了密封的泄漏量,且随着进出口压比的增加,两者泄漏量差异增大;密封的动力特性系数的随密封进出口压比与转速的增加而增大。在相同工况下,主刚度大于交叉刚度约一个数量级,主阻尼与交叉阻尼数量级相同,且主阻尼大于交叉阻尼;反旋流可有效降低密封的等效刚度,增加密封的等效阻尼,提高密封的稳定性。

Theoretical and Experimental Research on the Performance of Anti-swirl Flow for the Static and Dynamic Characteristics of Seals

Four kinds of seals with and without anti-swirl flow are designed and processed. Theoretical and experimental research on the performances of anti-swirl flow for the static and dynamic characteristics of seals is investigated. The anti-swirl flow seal static characteristics CFD theoretical model is set up to analyze the performance of anti-swirl flow on the tangential velocity, leakage and pressure distribution. Experiments are presented to test the leakage and the rotordynamic coefficients for the seals with and without anti-swirl flow. The rotordynamic coefficients are identified using an improved impedance method based on unbalanced synchronous excitation method. The results show that, compared to the traditional seals, the seals with anti-swirl flow have lower fluid tangential velocity, smaller circumferential pressure difference, and the fluid circumferential pressure difference decreases with the decreasing of the circumferential pressure difference. It is the main reason for anti-swirl flow reduces flow-induced force. Seal leakage increases almost linearly with inlet/outlet pressure ratio. The anti-swirl flow increases seal leakage, the leakage difference between with and without anti-swirl flow seal increases with the increase of inlet/outlet pressure ratio. Seal rotordynamic characteristic coefficients increase with inlet/outlet pressure ratio and rotational speed. In the same operating conditions, compare the cross-couple stiffness, direct stiffness has an order of magnitude higher. Cross-couple damper and direct damper have the same order of magnitudes, direct damper is bigger than cross-couple damper. The anti-swirl flow can effectively reduce the effective stiffness and increase the effective damping for variable conditions.