Improving the rotordynamic stability of short labyrinth seals using positive preswirl

Abstract

Introducing a negative preswirl at the upstream of annular gas seals has been considered as an effective way to improve the system stability. This paper demonstrates a stability enhancement approach for a short labyrinth seal using positive preswirls. The static and dynamic characteristics of the labyrinth seal with various blade numbers (5, 10, 15), inlet preswirl ratios (-0.3,-0.15, 0, 0.15, 0.3) were studied. Results show that the inlet preswirl ratio has a dramatic effect on the circumferential location of the high-pressure spot for each seal cavity, particularly for the first cavity. The inlet preswirl ratio has opposite effects on the system stability due to the difference of high-pressure spot locations between the first cavity and the others. An increasing positive inlet preswirl could improve the system stability for the labyrinth seal with fewer blades (e.g. 5 blades). Its characteristics is mainly dominated by the first seal cavity. For the labyrinth seal with 10 blades, the system characteristics shows slight dependency on the inlet preswirl ratio. For the labyrinth seal with more blades (e.g. 15 blades), the negative inlet preswirl still increases the system stability, which agrees with the conventional conclusion. The paper provides a deeper understanding on the stability improvement of the labyrinth seal.

Study on Leakage Performance and Rotordynamic Characteristics of a Novel Semi-Y Type Labyrinth Seal

“…The rotation and whirling speed are ω and Ω, respectively. The fluid-induced forces are modeled by: Generally, there are three methods to calculate rotordynamic coefficients, which are the finite perturbation method [32], the whirling rotor method [24,33], and the transient simulation method [23]. When considering the complexity of transient analysis and mov- To simplify the computation, we assume that…”

“…when two of the above parameters change, the other two parameters are kept the same. Generally, there are three methods to calculate rotordynamic coefficients, which are the finite perturbation method [32], the whirling rotor method [24,33], and the transient simulation method [23]. When considering the complexity of transient analysis and moving mesh, the whirling rotor method is adopted in this paper.…”

“…They presented that the negative pre-swirl was a stabilizing factor that had a great development of effective damping and the positive pre-swirl generated the opposite function. However, the results of Zhang et al [24] showed that a positive pre-swirl could enhance the stability of the labyrinth seal with few blades. Furthermore, Untaroiu et al [25] proposed a novel labyrinth seal with swirl brakes designed to increase system stability.…”