Session: 21-06: Labyrinth and Damper Seals

Paper Number: 127379

127379 - Assessment of Rotordynamic Characteristics for the Fully-Partitioned Pocket Damper Seal in a 150MW Steam Turbine 

As well known, labyrinth seals are widely used in turbomachinery and have the potential to provoke rotordynamic instability associated with subsynchronous vibration induced by the destabilizing seal fluid forces. Since the seal fluid forces are directly proportional to the fluid pressure drop and density, the rotordynamic instability is more likely to be induced by the labyrinth seal in high-pressure turbomachines such as steam turbines and centrifugal compressors. Pocket damper seal, Hole-pattern/Honeycomb damper seals have been commonly used for many years as damper seals in multiple-stage centrifugal compressor, introducing additional damping to improve the shaft rotordynamic stability if designed properly. For steam turbine, however, there are few literatures focusing on the application assessment of damper seals in high-pressure steam turbines.

This paper presents a comprehensive assessment and comparison on the static and rotordynamic characteristics of a fully-partitioned pocket damper seal and a staggered labyrinth seal used as the balance piston seal in a 150MW 3000rpm multistage single casing steam turbine. The staggered labyrinth seal is an original seal scheme where the steam turbine experienced strong subsynchronous rotordynamic instability, preventing full load operation of the machine. The fully-partitioned pocket damper seal was designed (the same sealing clearance, inner diameter and axial length) to increase the rotor net damping and eliminate the subsynchronous vibration. The straight swirl brake device also was implemented at seal entrance as a solution scheme to reduce the swirl velocity and enhance the seal net damping capability at high inlet preswirl condition. Numerical results of seal leakage flow rates, rotordynamic force coefficients, cavity dynamic pressure and swirl velocity developments were presented and discussed, 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: ZHIGANG LI Xi'an Jiaotong University

Presenting Author Biography: Zhigang Li is the professor in the Institute of Turbomachinery at Xi’an jiaotong University. His research interests are in heat transfer and cooling of gas turbine blades, in advanced sealing techniques of turbomachinery. He has over 20 peer reviewed publications on AIAA Journals and ASME Journals, and has given several invited, keynote, and plenary lectures at international conferences.

Authors:

Weijun Zhao Dongfang Turbine CO.,LTD.
Wei Sun Dongfang Turbine CO.,LTD.
Zepei Li Dongfang Turbine CO.,LTD.
Zihan Zhang Xi'an Jiaotong University
ZHIGANG LI Xi'an Jiaotong University