Abstract
Annular seals of turbomachinery usually suffer from various degrees of eccentricities and disturbances due to the rotor–stator misalignment and radial loads, while the discussion of annular seal under both large static eccentricities and dynamic disturbances is relatively limited. In this paper, the applicability of linear assumption and reliability of nonlinear dynamic model for eccentric annular seals under large eccentricities and disturbances is discussed based on the investigation of seals with various rotor motions through computational fluid dynamics (CFD). After the validation of transient CFD methods by comparison with experimental and bulk theory results, the dynamic behaviors of annular seal are analyzed by adopting both direct transient simulations and the nonlinear Muszynska model. The results show that the nonlinear dynamic model based on rotor circular whirls around seal center can predict the fluid excitations of different types of rotor motions well under small static eccentricities, while it is limited severely with large static eccentricities, which indicates that the dynamic characteristics of annular seal under large eccentricities are related with the rotor’s motion ways. The paper provides a reference for studies of rotor–seal system with complex rotor motions considering radial loads or running across the resonance region.
Highlights
Hydraulic machinery such as pumps and turbines is widely applied in various energy fields, playing a significant role in energy development, utilization and transformation
Wu et al [16] developed a new transient computational fluid dynamics (CFD) method, which is based on rotor’s variable-speed whirl; the results show that this new method can keep good accuracy of traditional transient method and save much computational time and cost in the meantime
The leakage rates and force coefficients of annular seal under different static eccentricity positions and same whirl amplitude ratio (∆Eccentricity ratio (e/Cr) = 1%) are computed using the numerical scheme based on transient CFD simulations
Summary
Hydraulic machinery such as pumps and turbines is widely applied in various energy fields, playing a significant role in energy development, utilization and transformation. The vibration caused by the fluid forces generated in gap seals of hydraulic machinery tend to have important effects on the efficiency and vibration of rotor system [1]. Due to the rise of safety and efficiency concerns, dynamic characteristics of various annular seals have been studied by researchers [2,3,4,5]. Almost all of these studies are based on the assumption of small perturbation, linear dynamic characteristics of annular seals can be investigated. Under the condition of static equilibrium, the rotor is normally concentric with the annular seal
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