Investigation on the flow-induced tangential force characteristic of labyrinth seals under different operation parameters

The flow-induced tangential force Ft is crucial for the annular gas seal stability. In this paper, a three-dimensional CFD model is established to study the Ft characteristics of the labyrinth seal. The overall Ft of the seal section is decomposed into each seal cavity. The Ft characteristic of each seal cavity versus rotation speed ω and inlet pressure pin is analyzed. The result shows that the sign of Ft in each seal cavity changes from the negative to the positive along the leakage direction, resulting in a specific crossing tooth number Nc at which Ft≈ 0 N. When the tooth number is smaller than Nc, the seal stability increases with the increase of ω and pin. When the tooth number is larger than Nc, the trend is reversed. When the tooth number equals Nc, the seal stability is in a critical state, showing no dependency to the ω and pin. The Nc is a novel index for the labyrinth seal stability.