Session: 23-10 Labyrinth Seals

Paper Number: 153351

Rotordynamic Coefficients and Leakage Analysis of Labyrinth Seals in Oil-Free Centrifugal Compressor Using Transient CFD Approach With Refrigerants 

The increasing demand for refrigeration, data center cooling, and heat pumps is driving advancements in oil-free centrifugal compressors running with refrigerants. These systems require highly efficient seals to minimize secondary flow leakage and ensure optimal performance and energy efficiency. This study specifically investigates the rotordynamic characteristics and leakage flow rates of three labyrinth seal configurations: tooth on stator (TOS), tooth on rotor (TOR), and interlocking labyrinth seal (ILS), in conjunction with four refrigerants—R134A, R515B, R513A, and R1234ZE—widely used in modern chiller systems. This study utilizes an advanced numerical method, which integrates a multiple frequencies elliptical whirling orbit model with a transient Reynolds-averaged Navier–Stokes (RANS) solution. This method, combined with a computational fluid dynamics (CFD) approach and mesh deformation technique, allows for highly accurate simulations of dynamic pressure fields and the calculation of force coefficients. Furthermore, this study introduces a comparative analysis of the accuracy of the transient CFD method against two other common methods in labyrinth seal analysis: the bulk flow method and the steady eccentric 3D CFD method. While both the bulk flow and steady eccentric methods are widely used for gas labyrinth seals, their results are poor for high-speed machines and small clearance seals.

The comparison reveals significant discrepancies between the methods in predicting frequency-dependent force coefficients, underscoring the limited accuracy of conventional approaches like the bulk flow method when applied to high-speed machines and small clearance seals. This accuracy is crucial for understanding the rotordynamics behavior of compressors running with refrigerants. The results of this study reveal that while the ILS configuration offers a reduction in leakage compared to the conventional TOS and TOR designs, its rotordynamic behavior, particularly in terms of effective damping (Ceff), can be less favorable for maintaining rotor stability under certain conditions. The ILS’s performance is highly dependent on the refrigerant used, and though it provides superior leakage reduction, the trade-offs in rotordynamic stability suggest that it may not always be the optimal choice for high-speed compressor systems. In contrast, the TOS and TOR configurations, though offering slightly higher leakage rates, demonstrate more consistent and predictable rotordynamic performance. These results contribute to the ongoing development of more efficient and stable compressors, which are critical for applications in chillers, data centers, and heat pumps as energy demands continue to rise globally.

Presenting Author: Wenjie Yin Copeland Corporation

Presenting Author Biography: Wenjie Yin is an Engineer Lead at Copeland (previously part of Emerson Electrics). His research focuses on turbomachinery, rotordynamics, electrical submersible pumps, centrifugal compressor and gas foil bearing. He has published several technical papers patents. Wenjie received his B.S. in Mechanics from University of Science and Technology of China (China), and his M.S. and Ph.D. in ME from Texas A&M University Turbomachinery Lab.

Authors:

Wenjie Yin Copeland Corporation
Ammasai Palani Copeland Corporation
Robert Wang Copeland Corporation