Nonlinear responses and bifurcations of a rotor-bearing system supported by squeeze-film damper with retainer spring subjected to base excitations

2020 ◽  
Vol 102 (4) ◽  
pp. 2143-2177
Author(s):  
Xi Chen ◽  
Xiaohua Gan ◽  
Guangming Ren
Keyword(s):  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Nonlinear Responses ◽  
Rotor Bearing ◽  
Bearing System

Study of Transfer Matrix of Rolling Bearing Including Squeeze Film Damper

2012 ◽  
Vol 490-495 ◽  
pp. 618-622
Author(s):  
Hua Tao Tang ◽  
Xin Yue Wu
Keyword(s):  
Transfer Matrix ◽  
Transfer Matrix Method ◽  
Matrix Method ◽  
Rolling Bearing ◽  
Squeeze Film ◽  
Body System ◽  
Squeeze Film Damper ◽  
Rotor Bearing ◽  
Multi Body ◽  
Bearing System

The transfer matrix of rolling bearing including squeeze film damper (SFD) is studied, and the rotor – bearing system is modeled by transfer matrix method of multi-body system. It is proved by an example that the method, which provides a new idea to solve the problem of complex rotor – bearing system, is feasible and effective.

On the Effect of the Gap of End Seals on Force Coefficients of a Test Integral Squeeze Film Damper: Experiments and Predictions

2020 ◽  
Author(s):  
Luis San Andrés ◽  
Xueliang Lu ◽  
Bonjin Koo ◽  
Scott Tran
Keyword(s):  
Theory And Practice ◽  
Squeeze Film ◽  
Test Element ◽  
Inlet Temperature ◽  
Dynamic Force ◽  
Virtual Mass ◽  
Squeeze Film Damper ◽  
Force Coefficients ◽  
Rotor Bearing ◽  
Bearing System

Abstract An integral squeeze film damper (ISFD) offers the advantages of a lower number of parts, a shorter axial span, a lighter weight, a split manufacturing and high precision on its film clearance construction. An ISFD does not only add damping to reduce shaft vibration amplitudes and to enhance the stability of a rotor-bearing system but also can be used to tune a rotor-bearing system natural frequency, and thus increasing the operational safety margin between the running shaft speed and the system critical speed. In spite of the numerous commercial applications, the archival literature is scant as per the experimental quantification of force coefficients for ISFDs. This paper details the results of an experimental and analytical endeavor to quantify and to predict the dynamic force coefficients of an ISFD, hence bridging the gap between theory and practice. With an axial length of 76 mm, the test damper element has four arcuate film lands, 73° in arc extent at a diameter of 157 mm, and each with a clearance (c) equaling to 0.353 mm. As is customary, the damper has its axial ends sealed with end plates produced by a set of installed shims giving an axial gap (d) equal to 1.5c, 1.21c, and 0.8c. A baseline configuration, namely open ends, is also tested without the end seals in place. In the test rig, the ISFD and its housing are flexibly mounted while the rotor is rigid and stationary (no spinning). The lubricant is an ISO VG46 oil supplied at a low pressure, 1 to 2 bar(g) and ∼ 47 °C inlet temperature, typical of compressor applications. The test procedure applies static loads on the ISFD and records the bearing static offset or eccentricity to verify the structure stiffness, and meanwhile, individual hydraulic shakers deliver dynamic loads along two orthogonal directions to produce motions over a set frequency range, 10 Hz to 160 Hz. The ISFD produces direct damping and inertia that increase with the journal static eccentricity albeit at a lower rate than predictions from a computational squeeze film flow model that includes lubricant compressibility. The end seals are effective in significantly raising the damping coefficient while reducing the oil through flow rate. The damper with the tightest sealed ends (d = 0.8c) shows nearly 20 times more damping that the open ends ISFD albeit also revealing a significant stiffness hardening (negative virtual mass) as the excitation frequency increases. On the contrary, the open ends ISFD and the sealed ends configurations with gaps d = 1.21c and 1.5c produce a (positive) virtual mass that exceeds the test element physical mass and thus softens the test element direct dynamic stiffness. For the configurations with loose end seals (d = 1.21c or larger to open ends), the model predicts well the damping coefficients but under predicts the added masses by 50% or more. Note this virtual mass coefficient, largely ignored in practice, can make the test element either extremely stiff as with the sealed damper configuration with the smallest gap d = 0.8c, or very soft as with the ISFD with end seals gap = 1.21c or 1.5c. Hence, designers are cautioned not to pursue overly tight end sealed dampers as the mineral lubricant, nearly incompressible though always having a small amount of entrapped gas, may behave distinctly when confined to a squeezed film volume and having no adequate routes to escape or flow through.

On the Effect of the Gap of End Seals on Force Coefficients of a Test Integral Squeeze Film Damper: Experiments and Predictions

2021 ◽  
Vol 143 (1) ◽  
Author(s):  
Xueliang Lu ◽  
Luis San Andrés ◽  
Bonjin Koo ◽  
Scott Tran
Keyword(s):  
Theory And Practice ◽  
Squeeze Film ◽  
Test Element ◽  
Inlet Temperature ◽  
Dynamic Force ◽  
Virtual Mass ◽  
Squeeze Film Damper ◽  
Force Coefficients ◽  
Rotor Bearing ◽  
Bearing System

Abstract An integral squeeze film damper (ISFD) offers the advantages of a lower number of parts, a shorter axial span, a lighter weight, a split manufacturing, and high precision on its film clearance construction. An ISFD does not only add damping to reduce shaft vibration amplitudes and to enhance the stability of a rotor-bearing system but also can be used to tune a rotor-bearing system natural frequency, and thus increasing the operational safety margin between the running shaft speed and the system critical speed. In spite of the numerous commercial applications, the archival literature is scant as per the experimental quantification of force coefficients for ISFDs. This paper details the results of an experimental and analytical endeavor to quantify and to predict the dynamic force coefficients of an ISFD, hence bridging the gap between theory and practice. With an axial length of 76 mm, the test damper element has four arcuate film lands, 73 deg in arc extent at a diameter of 157 mm, and each with a clearance (c) equaling to 0.353 mm. As is customary, the damper has its axial ends sealed with end plates produced by a set of installed shims giving an axial gap (d) equal to 1.5c, 1.21c, and 0.8c. A baseline configuration, namely, open ends, is also tested without the end seals in place. In the test rig, the ISFD and its housing are flexibly mounted while the rotor is rigid and stationary (no spinning). The lubricant is an ISO VG46 oil supplied at a low pressure, 1 to 2 bar(g) and ∼47 °C inlet temperature, typical of compressor applications. The test procedure applies static loads on the ISFD and records the bearing static offset or eccentricity to verify the structure stiffness, and meanwhile, individual hydraulic shakers deliver dynamic loads along two orthogonal directions to produce motions over a set frequency range, 10 Hz to 160 Hz. The ISFD produces direct damping and inertia that increase with the journal static eccentricity albeit at a lower rate than predictions from a computational squeeze film flow model that includes lubricant compressibility. The end seals are effective in significantly raising the damping coefficient while reducing the oil through flow rate. The damper with the tightest sealed ends (d = 0.8c) shows nearly 20 times more damping that the open ends ISFD albeit also revealing a significant stiffness hardening (negative virtual mass) as the excitation frequency increases. On the contrary, the open ends ISFD and the sealed-ends configurations with gaps d = 1.21c and 1.5c produce a (positive) virtual mass that exceeds the test element physical mass and thus softens the test element direct dynamic stiffness. For the configurations with loose end seals (d = 1.21c or larger to open ends), the model predicts well the damping coefficients but under predicts the added masses by 50% or more. Note this virtual mass coefficient, largely ignored in practice, can make the test element either extremely stiff as with the sealed damper configuration with the smallest gap d = 0.8c, or very soft as with the ISFD with end seals gap = 1.21c or 1.5c. Hence, designers are cautioned not to pursue overly tight end sealed dampers as the mineral lubricant, nearly incompressible though always having a small amount of entrapped gas, may behave distinctly when confined to a squeezed film volume and having no adequate routes to escape or flow through.

Numerical investigation of dynamic and hydrodynamic characteristics of the pad in the fluid pivot journal bearing

2021 ◽  
pp. 135065012110330
Author(s):  
Tuyen Vu Nguyen ◽  
Weiguang Li
Keyword(s):  
Computational Models ◽  
Journal Bearing ◽  
Squeeze Film ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Properties ◽  
Squeeze Film Damper ◽  
Lubricant Oil ◽  
Oil Flow ◽  
Flow Through ◽  
Bearing System

The dynamic and hydrodynamic properties of the pad in the fluid pivot journal bearing are investigated in this paper. Preload coefficients, recess area, and size gap, which were selected as input parameters to investigate, are important parameters of fluid pivot journal bearing. The pad’s pendulum angle, lubricant oil flow through the gap, and recess pressure which characterizes the squeeze film damper were investigated with different preload coefficients, recess area, and gap sizes. The computational models were established and numerical methods were used to determine the equilibrium position of the shaft-bearing system. Since then, the pendulum angle of the pad, liquid flow, and recess pressure were determined by different eccentricities.

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