Experimental Research on Rotordynamic Characteristics of Labyrinth Seals at High Inlet Preswirl

To better understand the rotordynamic characteristics of a labyrinth seal at high inlet preswirl and elucidate the mechanism of instability induced by airflow, the rotordynamic characteristic test rig of Xi'an Jiaotong University was utilized to research the effects of pressure ratio and rotational speed on the rotordynamic characteristics of the labyrinth seal at high inlet preswirl(preswirl ratio μ0>0.8). The frequency-dependent rotordynamic coefficients were measured at two pressure ratios(π=3.0, 4.0)and three rotational speeds(n=3 000, 6 000, 12 000 r/min). The results show that at high inlet preswirl, the labyrinth seal had always a large positive cross-coupled stiffness so that its effective damping was always negative, which was not conducive to the stability and may cause instability of the rotor system. It is also shown that the rotordynamic characteristics were significantly affected by the pressure ratio:As the ratio increased, the direct stiffness increased greatly, the cross-coupled stiffness was always positive and increased greatly, and the effective damping decreased significantly and that the rotordynamic characteristics were slightly affected by the rotational speed:Direct stiffness and direct damping were insensitive to speed change and remained substantially unchanged, and the cross-coupled stiffness increased slightly along with the speed increase, resulting in a slight decrease of effective damping. © 2022 Xi'an Jiaotong University. All rights reserved.