Session: 21-06: Labyrinth and Damper Seals

Paper Number: 127426

127426 - Assessment of Rotordynamic Characteristics for the Hole-Pattern Damper Seal in a 150MW Steam Turbine 

Damper seals and swirl brakes have been commonly used for many years as a solution for the rotor vibration instability in multiple-stage centrifugal compressor. However, there are few literatures focusing on the application assessment of damper seals and swirl brakes in high-pressure steam turbines.

This paper presents two attempt schemes (swirl brake, damper seal) to resolve the strong subsynchronous vibration instability for a 150MW 3000rpm multistage single casing steam turbine. The rotor vibration instability has been demonstrated to be caused by the steam whirl forces generated at the balance piston seal location in combination with a long flexible rotor. The original balance piston seal scheme is a staggered labyrinth seal with both teeth on stator and rotor, yielding high cross-coupling stiffness and large negative effective damping at high inlet preswirl condition. To resolve the subsynchronous vibration instability and allow full load operation of the steam turbine, a straight swirl brake was designed and implemented at seal entrance for the staggered labyrinth seal. What is more, the effects of the swirl brake number also were discussed. The hole-pattern damper seal with/without inlet swirl brake, damper seal schemes, were designed as the replacement of the original staggered labyrinth seal. A comprehensive assessment and comparison was conducted on the static and rotordynamic characteristics for the original staggered labyrinth seal and the new hole-pattern damper seal, using a proposed transient CFD-based perturbation method based on the multiple-frequency elliptical-orbit rotor whirling model and the mesh deformation technique.

Presenting Author: Zihan Zhang Xi'an Jiaotong University

Presenting Author Biography: Zihan Zhang is a Master Student in Xi'an jiaotong University. His research topic is focusing on the leakage and rotordynamic characteristics of annular gas seals.

Authors:

Weijun Zhao Dongfang Turbine CO.,LTD.
Biao Huang Dongfang Turbine CO.,LTD.
Chunbo Zheng Dongfang Turbine CO.,LTD.
Zihan Zhang Xi'an Jiaotong University
Zhigang Li Xi'an Jiaotong University