非均匀进汽时迷宫密封汽流激振动力特性的研究

摘要

采用基于转子多频椭圆涡动模型和动网格技术的URANS方程求解方法,研究了动、静叶干涉作用以及级间补汽导致的非均匀进汽温度和压力条件下叶顶迷宫密封汽流激振转子动力特性,计算分析了进汽预旋比为0.2、0.5、0.7时叶顶迷宫密封转子动力特性系数,并与均匀进汽温度和压力条件下迷宫密封转子动力特性系数进行了比较.研究结果表明:密封转子稳定性随进汽预旋比的增加而降低;非均匀和均匀进汽条件下迷宫密封腔室周向旋流强度和腔室压力分布的差异随进汽预旋比的增加而逐渐减小,2种进汽条件下密封转子动力特性系数之间的差异随进汽预旋比的增加而减小;与均匀进汽相比,进汽预旋比为0.2时非均匀进汽下迷宫密封交叉刚度至少降低82.7％,交叉阻尼至少增加30.7％;进汽预旋比为0.5时非均匀进汽下迷宫密封有效阻尼仅在涡动频率为50～i00 Hz时较均匀进汽低8.4％～12.4％;进汽预旋比增加至0.7时,非均匀和均匀进汽条件下迷宫密封转子动力特性系数基本相同.显然,进汽预旋比较高时进汽均匀性对迷宫密封汽流激振转子动力特性系数的影响可以忽略.%The effect of non-uniform inlet flow temperature and pressure conditions due to stator/ rotor interaction and supplementary steam on fluid excited rotordynamic characteristics of blade tip labyrinth seal was numerically investigated by unsteady Reynolds-averaged Navier-Stokes (URANS) solution based on the multi-frequency elliptical orbit rotor whirling model and dynamic mesh technique.The rotordynamic coefficients of blade tip labyrinth seal were calculated at three different inlet preswirl ratios of 0.2,0.5 and 0.7.The rotordynamic characteristics of the blade tip labyrinth seal were comparatively analyzed under the conditions of non-uniform and uniform inlet flow temperature and pressure.The obtained results show that the increasing inlet preswirl ratio weakens rotor stability of labyrinth seal;the discrepancies of the circumferential swirl strength and pressure under non-uniform inlet and uniform inlet conditions are gradually reduced with the increasing inlet swirl ratio,and the differences of rotordynamic characteristics under the two conditions are also reduced when inlet preswirl ratio increases.At least a reduction of 82.7 ％ in cross-coupling stiffness Kxy,an increase of more than 30.7 ％ in cross-coupling damping Cxy of the blade tip labyrinth seal under non-uniform inlet conditions are observed at inlet preswirl ratio of 0.2 compared with uniform inlet conditions.When inlet preswirl ratio increases to 0.5,the effective damping under non-uniform inlet condition is only 8.4％-12.4％ lower than that of uniform inlet condition at whirling frequencies from 50 Hz to 100 Hz.The same rotordynamic coefficients of the blade tip labyrinth seal are captured for the non-uniform and uniform inlet conditions at inlet preswirl ratio 0.7,so the effect of the inlet flow condition on the rotordynamic characteristics can be omitted at higher inlet preswirl ratio.