Abstract: The pressure drop distribution between the multi-stage brush seals directly affects the seal characteristics and the service life of the brush seals. The existing multi-stage brush seals structure have the problem that the pressure drop is unbalanced at different stages, leading to premature seal failure. In this paper, a three-dimensional fluid-solid interaction multi-stage brush seals model is established, and a multi-stage brush seals experimental device is designed. Based on the mutual verification of numerical calculation and experimental test results, the influence law of working condition parameters and structural parameters on the interstage pressure drop distribution of multi-stage brush seals is investigated. The mechanism of interstage pressure drop imbalance of multi-stage brush seals is revealed. The results show that under the research conditions in this paper, the pressure drop ratio of the two-stage brush seals of the same structure are 32%-35% and 65%-68%, and the pressure drop ratio of the three-stage brush seals are different:21%-27%, 27%-32%, 41%-52%. The pressure drop of the multi-stage brush seals is gradually increased, and the pressure ratio of the inlet and outlet has little effect on the distribution of interstage pressure drop. By increasing the radial gap between the bristle tow and the rotor surface, the gap between the bristles and the height of the backplate can improve the pressure drop distribution of each level, and the amount of leakage will also increase. The main reason that affects the pressure drop balance of the multi-stage brush seals is the uneven increase of volume flow rate step by step, and the pressure drop of each stage increases with the increase of the volume flow unevenness step by step. Increasing the cross-sectional area of the downstream level can effectively reduce the volume flow rate and balance the pressure drop between multi-stage brush seals. The research results in this paper provide a theoretical basis for the design of multi-stage brush seals structure.

Key words: multi-stage brush seals, interstage pressure drop distribution, three-dimensional modeling, fluid-solid interactions, interstage pressure drop imbalance