Swirl brakes are usually introduced at the seal entrance in industry to improve the seal stability,especially for labyrinth seals suffering low seal clearance and high inlet preswirl ratio.However,how to arrange swirl...Swirl brakes are usually introduced at the seal entrance in industry to improve the seal stability,especially for labyrinth seals suffering low seal clearance and high inlet preswirl ratio.However,how to arrange swirl brakes at the seal entrance to obtain better seal stability retains unknown,such as the axial distance between the brake trailing edge and the first tooth.To this end,the effects of the distance between brakes and the first tooth on the leakage flow rate and seal rotordynamic coefficients were numerically investigated at typical inlet preswirl ratios of 0.45 and0.8,and the predicted results were in comparison with the results for no-brake configuration.The obtained results disclose that the brake configuration arranged against the first tooth produces lower circumferential velocity in the downstream of the brakes as a result of the larger counterclockwise vortex moving from the brake trailing edge to the brake leading edge when compared to the brake configuration away from the first tooth.Besides,the dropped circumferential velocity in the downstream of brakes will cause larger pressure fluctuation in the circumferential direction and thus generates larger tangential force to restrain the rotor forward whirl.On the other hand,the effective damping is further increased when the distance between brakes and the first tooth decreases to zero,that is,the crossover frequency is even disappeared at the inlet preswirl ratio of 0.45 and successfully drops from 69.9 Hz to 32.7 Hz at the preswirl ratio of 0.8.展开更多
API 617标准中要求,离心压缩机产品(包括辅助设备)应确保其最短使用寿命为20年,不间断连续运转时间至少为5年。本文中的压缩机组高压缸转子在实际运行中发生了动力学失稳现象。通过分析,认为对于该机组的转子稳定性分析,应该考虑叶轮气...API 617标准中要求,离心压缩机产品(包括辅助设备)应确保其最短使用寿命为20年,不间断连续运转时间至少为5年。本文中的压缩机组高压缸转子在实际运行中发生了动力学失稳现象。通过分析,认为对于该机组的转子稳定性分析,应该考虑叶轮气动效应的影响,并发现考虑叶轮气动效应后的转子稳定性与实际运行情况一致,且不满足API 617的要求,为了改善该压缩机的转子稳定性,在叶轮口圈和平衡盘密封处添加阻旋栅,从分析结果看,该措施提高了转子的对数衰减率,满足API 617的要求。展开更多
基金funded by the National Key R&D Program of China(No.2017YFB0601804)the National Natural Science Foundation of China(No.51776152)。
文摘Swirl brakes are usually introduced at the seal entrance in industry to improve the seal stability,especially for labyrinth seals suffering low seal clearance and high inlet preswirl ratio.However,how to arrange swirl brakes at the seal entrance to obtain better seal stability retains unknown,such as the axial distance between the brake trailing edge and the first tooth.To this end,the effects of the distance between brakes and the first tooth on the leakage flow rate and seal rotordynamic coefficients were numerically investigated at typical inlet preswirl ratios of 0.45 and0.8,and the predicted results were in comparison with the results for no-brake configuration.The obtained results disclose that the brake configuration arranged against the first tooth produces lower circumferential velocity in the downstream of the brakes as a result of the larger counterclockwise vortex moving from the brake trailing edge to the brake leading edge when compared to the brake configuration away from the first tooth.Besides,the dropped circumferential velocity in the downstream of brakes will cause larger pressure fluctuation in the circumferential direction and thus generates larger tangential force to restrain the rotor forward whirl.On the other hand,the effective damping is further increased when the distance between brakes and the first tooth decreases to zero,that is,the crossover frequency is even disappeared at the inlet preswirl ratio of 0.45 and successfully drops from 69.9 Hz to 32.7 Hz at the preswirl ratio of 0.8.
