Influence Factors of Honeycomb Seal Performance and Stability Analysis of Rotor System

Abstract

Structural parameters and inlet preswirl have great influences on the static and dynamic characteristics of honeycomb seals. In this paper, a multifrequency elliptical vortex dynamic model of a honeycomb seal was established by an unsteady dynamic grid technique. Based on verification of the numerical model, the effects of honeycomb cell size, axial length, and inlet preswirl on seal performance were investigated. Rotor–bearing–seal stability experiments were carried out to measure the logarithmic decrement rate of the rotor system under different rotational speeds, and the stability of the rotor system was further analyzed. The results showed that with increasing hole depth, leakage of the honeycomb seal increased initially due to the increasing airflow rate in response to vortex formation, and thereafter decreased, caused by the intense dissipation effect of turbulence. With increasing opposite-edge distance of core cell and decreasing axial length, the decreasing number of honeycomb cores on stator surfaces weakened the dissipation capacity of the turbulence, resulting in increases of leakage. Inlet preswirl had little effect on the leakage. However, it had a lower absolute value of tangential airflow excitation force and a lower effective damping coefficient under a higher inlet preswirl, indicating a lower dynamic characteristic of the honeycomb seal. Compared with other seals with different parameters, the honeycomb seal with structural parameters of B3H3L96 showed a higher effective damping coefficient under different inlet/outlet pressure ratios and different vortex frequencies and a higher logarithmic decrement rate under different rotational speeds, indicating a better stability of the rotor system.