Dynamic modeling of an eccentric face seal including coupled rotordynamics, face contact, and inertial maneuver loads

2017 ◽  
Vol 232 (6) ◽  
pp. 732-748
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Dynamic Modeling ◽  
Equations Of Motion ◽  
Center Of Mass ◽  
Contact Friction ◽  
Face Seal ◽  
Transient Operation ◽  
Angular Misalignment ◽  
The Face ◽  
Mechanical Face Seal ◽  
Constitutive Components

Mechanical face seals are constitutive components of turbomachines, which in turn can be constitutive to other systems (e.g. aircraft). Furthermore, the rotating element of a face seal is inextricably coupled to the turbomachine via a flexible mount, and the stationary seal element is coupled to the rotating seal element via the fluid film existing between the seal faces. Consequentially, understanding interactions between the seal and turbomachine is important for quantifying seal performance and improving its design. With few exceptions, previous works study the face seal dynamics independent from the rotordynamics. In addition, most prior investigations consider only angular and axial seal dynamics and neglect eccentric (i.e. lateral) deflections of the seal element(s). For the first time, this work develops a comprehensive and novel model of a mechanical face seal in the inertial reference frame including coupled rotordynamics and inertial maneuver loads of the overall system. The model is developed for a general seal geometry where both seal elements, stationary and rotating, are flexibly mounted and allowed to undergo angular, axial, and eccentric deflections. In addition, the seal model presented here accounts for transient operation, fluid shear forces, seal face contact, friction, and thermoelastic deformation. Finally, various faults due to manufacturing imperfections, component flaws, and/or installation errors can be accounted for by incorporating static angular misalignment of both seal elements, dynamic angular misalignment of the rotating seal element, eccentric rotating imbalance, and axial offset of the rotating seal element center of mass. Throughout this work, the equations of motion developed are valid for both steady-state and transient operation. This comprehensive model significantly advances the state of the art in mechanical face seal dynamic modeling and represents a pivotal step towards analyzing seal performance regarding a broad diversity of realistic problems.

scholarly journals Feasibility of Contact Elimination of a Mechanical Face Seal Through Clearance Adjustment

1999 ◽  
Author(s):  
Min Zou ◽  
Joshua Dayan ◽  
Itzhak Green
Keyword(s):  
Pattern Recognition ◽  
Power Spectrum ◽  
Real Time ◽  
Parametric Study ◽  
Experimental Results ◽  
Face Seal ◽  
Angular Misalignment ◽  
Adjustment Mechanism ◽  
Mechanical Face Seal

The feasibility of eliminating contact in a noncontacting flexibly mounted rotor (FMR) mechanical face seal is studied. The approach for contact elimination is based on a parametric study using FMR seal dynamics. Through clearance adjustment it is possible to reduce the maximum normalized relative misalignment between seal faces and, therefore, eliminate seal face contact Clearance is measured by proximity probes and varied through a pneumatic adjustment mechanism. Contact is determined phenomenologically from pattern recognition of probe signals and their power spectrum densities as well as angular misalignment orbit plots, all calculated and displayed in real-time. The contact elimination strategy is experimentally investigated for various values of stator misalignment and initial rotor misalignment Contrary to intuition but compliant with the parametric study, the experimental results show that for the seal under consideration contact can be eliminated through clearance reduction.

Three-dimensional nonlinear coupled dynamic modeling of a tip-loaded rotating cantilever

2018 ◽  
Vol 24 (22) ◽  
pp. 5366-5378 ◽  
Author(s):  
Mohammed Khair Al-Solihat ◽  
Meyer Nahon ◽  
Kamran Behdinan
Keyword(s):  
Dynamic Response ◽  
Rigid Body ◽  
Dynamic Modeling ◽  
Equations Of Motion ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Dissipation Function ◽  
Internal Damping ◽  
Symbolic Code ◽  
Mass Position

This paper presents a general three-dimensional flexible dynamic model of a tip-loaded rotating cantilever beam. For generality, the beam tip is assumed to be loaded with a rigid body with an arbitrary center of mass position, and subject to external force and moment. The coupled longitudinal (axial), bending–bending, and twist elastic motions are considered to formulate the system dynamics. The beam structural internal damping is modeled utilizing Rayleigh’s dissipation function. As well, the influence of gravity is considered. A symbolic code is developed to derive the equations of motion, and it is subsequently used to simulate the dynamics of two numerical case studies. The time response results are found to be in an excellent agreement with those reported from the literature. The effects of internal damping and coupling among the elastic motions on the system dynamic response are then investigated.

Rotordynamics of a Mechanical Face Seal Riding on a Flexible Shaft

1994 ◽  
Vol 116 (2) ◽  
pp. 345-350 ◽  
Author(s):  
An Sung Lee ◽  
Itzhak Green
Keyword(s):  
Dynamic Analysis ◽  
High Speed ◽  
Center Of Mass ◽  
Steady State Response ◽  
Face Seal ◽  
Rotating Shaft ◽  
State Response ◽  
Flexible Shaft ◽  
Mechanical Face Seal ◽  
Rotor Center

A mechanical face seal is a triboelement intended to minimize leakage between a rotating shaft and a housing, while allowing the shaft to rotate as freely as possible. All dynamic analysis to date have concentrated on the seal itself. In reality, however, especially in high speed turbomachinery, shafts are made flexible and the dynamics of seals must be coupled with the dynamics of shafts. (Perhaps the dynamics of other triboelements, such as gears, bearings, etc., have to be included as well.) In this work the complex extended transfer matrix method is established to solve for the steady state response of a noncontacting flexibly mounted rotor mechanical face seal that rides on a flexible shaft. This method offers a complete dynamic analysis of a seal tribosystem, including effects of shaft inertia and slenderness, fluid film, secondary seal, flexibly mounted rotating element, and axial offset of the rotor center of mass. The results are then compared to those obtained from an analysis that implicitly assumed the shaft rigid. The comparison shows that shaft dynamics can greatly affect the seal performance even at relatively low speeds.

scholarly journals Semi Salix Leaf Textured Gas Mechanical Face Seal with Enhanced Opening Performance

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7522
Author(s):  
Linqing Bai ◽  
Pengcheng Zhang ◽  
Zulfiqar Ahmad Khan
Keyword(s):  
Friction Torque ◽  
Contact Friction ◽  
Textured Surface ◽  
Face Seal ◽  
Textured Surfaces ◽  
Positive Effects ◽  
Mechanical Face Seal ◽  
Gas Face Seal ◽  
Hydrodynamic Effects ◽  
The Impact

Seal performance of a novel gas mechanical face seal with semi salix leaf textures was introduced and theoretically investigated with the purpose of enhancing hydrostatic and hydrodynamic opening performance. First, a theoretical model of a laser surface textured gas mechanical face seal with semi salix leaf textures was developed. Second, the impact of operating and texturing parameters on open force, leakage, and friction torque was numerically investigated and has been discussed based on gas lubrication theory. Numerical results demonstrate that the semi salix leaf textured gas face seal has larger hydrostatic and hydrodynamic effects than the semi ellipse textured seal because of the effect of the inlet groove. All semi salix leaf textured surfaces had better open performance than the semi ellipse textured surface, which means that the inlet groove plays an important role in improving open performance and consequently decreasing contact friction during the start-up stage. Texturing parameters also influenced the seal performance of thee semi salix leaf textured gas face seal. When the inclination angle was 50°, the radial proportion of the inlet groove was 0.8, the dimple number was 9, and the open force resulted in the maximum value. This research has demonstrated the positive effects of the applications of a semi salix leaf textured gas mechanical face seal that combines the excellent hydrostatic and hydrodynamic effects of groove texture and the excellent wear resistance of microporous textures.

Piezoelectric Vibration Control of a Sandwich Beam With Tip Mass

2018 ◽  
Author(s):  
Eshagh Farzaneh ◽  
Oumar Barry ◽  
Pablo Tarazaga
Keyword(s):  
Equations Of Motion ◽  
Center Of Mass ◽  
Sandwich Beam ◽  
Sensors And Actuators ◽  
Finite Element Software ◽  
The Face ◽  
Parametric Studies ◽  
Generalized Differential ◽  
Tip Mass ◽  
Piezoelectric Vibration

This paper studies the vibration mitigation of a sandwich beam with tip mass using piezoelectric active control. The core of the sandwich beam is made of foam and the face sheets are made of steel with a bonded piezoelectric actuator and sensor. The three-layer sandwich beam is clamped at one end and carries a payload at the other end. The tip mass is such that its center of mass is offset from the point of attachment. The extended higher-order sandwich panel (HSAPT) theory is employed in conjunction with the Hamilton’s principle to derive the governing equations of motion and boundary conditions. The obtained partial differential equations are solved using the generalized differential quadrature (GDQ) method. Free and forced vibration analyses are carried out and the results are compared with those obtained from the use of the commercial finite element software ANSYS. Derivative feedback control algorithm is employed to control the vibration of the system. Parametric studies are conducted to examine the arrangement impact of the piezoelectric sensors and actuators on the system vibrational behavior.

An Analysis of Mechanical Face Seal Vibrations

1981 ◽  
Vol 103 (3) ◽  
pp. 428-433 ◽  
Author(s):  
I. Etsion ◽  
Y. Dan
Keyword(s):  
Small Perturbation ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Design Parameters ◽  
Face Seal ◽  
Axial Motion ◽  
Flexible Support ◽  
Operation Conditions ◽  
Mechanical Face Seal ◽  
Three Degrees Of Freedom

The motion of a flexibly mounted ring in a mechanical face seal is described in its major three degrees of freedom. The equations of motion include fluid film as well as flexible support forces and moments. These equations are linearized using small perturbation analysis. It is shown that for small perturbation the axial motion is uncoupled with the two angular ones and is always stable. A condition for angular stability is derived relating seal operation conditions to its geometry and other design parameters.

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

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Steady State ◽  
Equations Of Motion ◽  
External Input ◽  
Face Seal ◽  
Flexible Rotor ◽  
State Equations ◽  
Fluid Forces ◽  
Flexible Rotors ◽  
Successful Design ◽  
Constitutive Components

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.

Feasibility of Contact Elimination of a Mechanical Face Seal Through Clearance Adjustment

2000 ◽  
Vol 122 (3) ◽  
pp. 478-484 ◽  
Author(s):  
Min Zou ◽  
Joshua Dayan ◽  
Itzhak Green
Keyword(s):  
Pattern Recognition ◽  
Power Spectrum ◽  
Real Time ◽  
Parametric Study ◽  
Experimental Results ◽  
Face Seal ◽  
Angular Misalignment ◽  
Adjustment Mechanism ◽  
Mechanical Face Seal

The feasibility of eliminating contact in a noncontacting flexibly mounted rotor (FMR) mechanical face seal is studied. The approach for contact elimination is based on a parametric study using FMR seal dynamics. Through clearance adjustment it is possible to reduce the maximum normalized relative misalignment between seal faces and, therefore, eliminate seal face contact. Clearance is measured by proximity probes and varied through a pneumatic adjustment mechanism. Contact is determined phenomenologically from pattern recognition of probe signals and their power spectrum densities as well as angular misalignment orbit plots, all calculated and displayed in real-time. The contact elimination strategy is experimentally investigated for various values of stator misalignment and initial rotor misalignment. Contrary to intuition but compliant with the parametric study, the experimental results show that for the seal under consideration contact can be eliminated through clearance reduction. [S0742-4795(00)01503-9]

The Prediction of Film Thickness in a Mechanical face Seal with Circumferential Waviness on both the face and the seat

1982 ◽  
Vol 24 (1) ◽  
pp. 37-43 ◽  
Author(s):  
A. V. Ruddy ◽  
D. Dowson ◽  
C. M. Taylor
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Closed Loop ◽  
Lubrication Theory ◽  
Fluid Film ◽  
Squeeze Film ◽  
Two Dimensional ◽  
Face Seal ◽  
The Face ◽  
Mechanical Face Seal

The effect of two-period waviness on both the face and the seat of a mechanical face seal is examined theoretically in this paper. A closed-loop cyclic solution of the two-dimensional Reynolds' equation including squeeze-film effects is described. Results for a 45 mm diameter seal are presented which show that squeeze-film effects play an important role in protecting the fluid-film over parts of the cycle where the entraining effect is small. The analysis can be extended to allow for misalignment of the sealing faces and for the incorporation of mixed-lubrication theory.

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