Steady-State Response of a Flexibly Mounted Stator Mechanical Face Seal Subject to Dynamic Forcing of a Flexible Rotor

Abstract

Mechanical face seals are constitutive components of much larger turbomachines and require consideration of the system dynamics for successful design. The dynamic interplay between the seal and rotor is intensified by recent trends toward reduced clearances, higher speeds, and more flexible rotors. Here, the “rotor” consists of the flexible shaft and the rotating seal seat. The objective here is to, for the first time, determine how the rotor affects the seal performance and vice versa. Thresholds can then be established beyond which the rotor influences the seal but not vice versa (i.e., the rotordynamics can be sent to the seal analysis as an exogenous input). To this end, a model of a flexibly mounted stator face seal is provided including the coupled dynamics of the flexible rotor. The model accounts for axial and angular deflections of the rotor and seal. Coupled rotordynamics are modeled using a lumped-parameter approach including static and dynamic rotor angular misalignments. For expediency, linearized expressions for fluid forces are used, and the resulting steady-state equations of motion are solved analytically to investigate how rotor inertia, speed, and angular misalignment influence the coupled seal dynamics. Importantly, results from the study reveal that in some operating regimes, neglecting the rotordynamics implies healthy seal operation when instead intermittent rub exists between the faces. This work also shows that when the rotor inertia is much larger than the seal inertia, the rotordynamics can be solved separately and used in the seal model as an external input.

Transient response and rub-impact phenomenon of liquid lubricated non-contacting mechanical seals during external pressure fluctuation

“…The equilibrium film thickness h 0 is the initial position at steady state. The film thickness distribution h(r,θ,t) in polar coordinates system can be expressed as [15]:…”

“…Varney and Green [3] investigated heavy contact and failure via instability-induced severe contact on flexibly mounted stator (FMS). Furthermore, they put forward a coupled rotor dynamics model using a lumped-parameter approach including static and dynamic rotor angular misalignments [15]. Falaleev defined the range of applicability for a two-mass dynamic model of face gas seals on amplitude and frequency [16].…”

Frequency‐Domain‐Based Nonlinear Response Analysis of Stationary Ring Displacement of Noncontact Mechanical Seal

“…e response is used to analyze system stability and determine system leakage. Varney and Green [6], Songtao et al [7], and Badykov and Falaleev [8], respectively, used the pressure caused by the change of the rotating shaft speed, the stationary unbalanced force of the stationary ring caused by the pressure difference between the inside and outside of the sealed cavity, and the speed step as the excitation, and calculated the stationary ring time. e response within the domain is used to analyze the follow-up of the dynamic and stationary ring and to acquire system leakage.…”

Eliminating the Fluid‐Induced Vibration and Improving the Stability of the Rotor/Seal System Using the Inerter‐Based Dynamic Vibration Absorber

“…e fluid circumferential average velocity ratio is considered a key parameter for the instability vibration control. It can be realized using the various seals to disrupt the fluid flow [2][3][4]. e antiswirl flow in the seal was a typical method to eliminate the instability [5].…”