进口预旋和孔序对蜂窝密封动力学特性影响研究

Effect of Inlet Preswirl and Hole Arrangement Patterns on the Dynamic Characteristics of Honeycomb Seals

蜂窝密封是抑制透平机械流体泄漏、提高系统稳定性的重要部件。建立蜂窝密封非定常数值计算模型,研究不同进口流体预旋比和孔序对密封动力特性的影响,并分析蜂窝密封内部流动特性。研究表明:不同预旋比和孔序对蜂窝密封直接刚度系数和直接阻尼系数影响较小,但正预旋比和交错孔结构会导致蜂窝密封平均交叉刚度系数增大、有效阻尼系数降低,负预旋比将降低蜂窝密封平均交叉刚度系数、提高有效阻尼系数。预旋可有效改善蜂窝密封孔内周向压力分布的均匀程度,然而交错孔结构易增加孔内周向压力不均匀程度。进口流体正预旋和交错孔结构使转子表面负的气流力绝对值减小,增大转子涡动速度和位移,降低系统稳定性。而负预旋可有效增大负的气流力的绝对值,进而提高系统稳定性。进口流体预旋对蜂窝密封泄漏量影响较小,而交错孔蜂窝密封泄漏量降低(~2.5%)。

Honeycomb seals are a crucial component to restrict the fluid leakage and improve the system stability of turbomachines. An unsteady model for the honeycomb seal was established to study its dynamic characteristics with different inlet preswirl ratios and hole arrangement patterns, as well as to analyze its flow characteristics. Results showed that different preswirl ratios and hole arrangement patterns had slight effects on its direct stiffness coefficient and direct damping coefficient. The positive preswirl ratios and interlaced hole structure tended to improve the average cross-coupled stiffness coefficient and reduce the effective damping coefficient. However, the negative preswirl ratios showed a reduction in the average cross-coupled stiffness coefficient and an increase in the effective damping coefficient. Results also indicated that the preswirl would improve the unevenness distribution of the circumferential pressure inside the honeycomb hole. While the interlaced hole structure will increase the unevenness distribution of the circumferential pressure. The positive preswirl and interlaced hole structure would reduce the absolute value of the negative flow-induced forces. This phenomenon would increase the rotor whirling displacement and velocity and degrade the system stability. On the contrary, the negative preswirl could effectively increase the absolute value of the negative flow-induced forces, and then improve the system stability. The inlet preswirl would decrease slightly the leakage rate. While the leakage rate of the honeycomb seal with interlaced holes decreases significantly(~2.5%).