Hydrostatic Squeeze Film Damper Research Articles

Semi-Analytical Analysis of a Rigid Rotor Mounted on Four-Pad Hydrostatic Squeeze Film Damper with Single-Action Membrane-Type Restrictors

Abstract The current study is a semi-analytical analysis of the vibratory behaviour of a rigid vertical rotor, supported by a new hydrostatic squeeze film damper (HSFD), consisting of four hydrostatic pads fed through four single-action membrane-type variable-flow restrictors. The Reynolds equation based on the Newtonian theory of lubrication is used and then adapted to our work, which is solved semi-analytically. In this paper, we study the effect of different parameters, the eccentricity, membrane geometry coefficient, pressure ratio and rotational speed, on the main characteristics of a four-pad HSFD. From the simulation results, we observed that at the critical speed, the rigid rotor fed by membrane restrictor shows a decrease in transmitted forces, a decrease in vibration response and good system stability as compared with a similar rotor fed by capillary restrictor. From the results reported in this work, we observed good agreement between our study and other works.

Dynamic behavior of hydrostatic squeeze film dampers fed through four capillary restrictors with micropolar lubricant

PurposeThe purpose of this research is to study the dynamic behavior of hydrostatic squeeze film dampers made of four hydrostatic pads, fed through four capillary restrictors with micropolar lubricant.Design/methodology/approachThe modified version of Reynolds equation is solved numerically by the finite differences and the Gauss–Seidel methods to determine the pressure field generated on the hydrostatic bearing flat pads. In the first step, the effects of the pad dimension ratios on the stiffness and damping coefficients are investigated. In the second step, the damping factor is evaluated with respect to the micropolar properties.FindingsThe analysis revealed that the hydrostatic squeeze film dampers lubricated with micropolar lubricants produces the maximum damping factor for characteristic length of micropolar lubricant less than 5, while the same bearing operating with Newtonian lubricants reaches its maximum damping factor at eccentricity ratios larger than 0.4.Originality/valueThe results obtained show that the effects of micropolar lubricants on the dynamic performances are predominantly affected by the pad geometry and eccentricity ratio.

Experimental investigation for novel hybrid journal bearing with hydrostatic squeeze film and metal mesh damper in series

PurposeThis study aims to present a novel hydrostatic squeeze film-metal mesh journal bearing (HS-MMJB), which uses both hydrostatic squeeze film damper (HSFD) and metal mesh damper (MMD), to suppress the vibration of rotor-bearing systems.Design/methodology/approachThe lubrication equations were introduced to calculate the dynamic characteristics of HS-MMJB, and the response analyses of rotor systems were carried out. Experiments were conducted to study the vibration reduction of a rotor system with HS-MMJB. In addition, experiments for different oil supply pressures in the HS-MMJB were conducted.FindingsThe theoretical and experimental results show that the HS-MMJB exhibits excellent damping and vibration attenuation characteristics. Moreover, the stability of the rotor system can be improved by controlling the oil supply pressure.Originality/valueThere is a dearth of research on vibration characteristics of rotor system support by journal bearing combining HSFD and MMD. Moreover, the active oil pressure control is implemented to improve the stability of rotor system.

Dynamic behavior analysis of a rigid rotor supported by hydrostatic squeeze film dampers compensated with new electrorheological valve restrictors

PurposeThis paper aims to propose a new hydrostatic squeeze film damper compensated with electrorheological valve restrictors to control the nonlinear dynamic behavior of a rigid rotor caused by high unbalance eccentricity ratio. To investigate the effect of electrorheological valve restrictors on the dynamic behavior of a rigid rotor, a nonlinear model is developed and presented.Design/methodology/approachThe nonlinear results are compared with those obtained from a linear approach. The results show good agreement between the linear and nonlinear methods when the unbalanced force is small. The effects of unbalance eccentricity ratio and electric field on the vibration response and the bearing transmitted force are investigated using the nonlinear models.FindingsThe results of simulation performed that the harmonics generated by high unbalance eccentricities can be reduced by using hydrostatic squeeze film damper compensated with electrorheological valve restrictors.Originality/valueThe numerical results demonstrate that this type of smart hydrostatic squeeze film damper provides to hydrostatic designers a new bearing configuration suitable to control rotor vibrations and bearing transmitted forces, especially for high speed.

Influence of different flow regimes on the performance characteristics of a four-pad hydrostatic squeeze film damper loaded between pads

PurposeThe purpose of this paper is to study the influence of different flow regimes on the dynamic characteristics of four-pad hydrostatic squeeze film dampers (SFDs) loaded between pads.Design/methodology/approachA numerical model based on Constantinescu’s turbulent lubrication theory using the finite difference method has been developed and presented to study the effect of eccentricity ratio on the performance characteristics of four-pad hydrostatic SFDs under different flow regimes.FindingsIt was found that the influence of turbulent flow on the dimensionless damping of four-pad hydrostatic SFDs appears to be essentially controlled by the eccentricity ratio. It was also found that the laminar flow presents higher values of load capacity compared to bearings operating under turbulent flow conditions.Originality/valueIn fact, the results obtained show that the journal bearing performances are significantly influenced by the turbulent flow regime. The study is expected to be useful to bearing designers.

Analytical analysis of a rigid rotor mounted on three hydrostatic pads lubricated with micropolar fluids

Analytical analysis of rigid rotor set vertically, supported by a new hydrostatic squeeze film damper consisting in three hydrostatic pads fed through three capillary restrictors operating with micropolar lubricant is presented. The modified Reynolds equation is obtained using the micropolar lubrication theory and solving it analytically. The calculation of the flow rate, dimensionless vibratory amplitude and amplitude of transmitted forces are determined by resolving the equations of rotor motion using nonlinear methods. It has been observed that a rigid rotor operating with micropolar lubricant shows an increase in the value of transmitted forces at high speeds and a reduction in the value of vibratory response at critical speed when compared to a corresponding similar rigid rotor operating with Newtonian lubricant.

Static and dynamic characteristics of an orifice compensated three-pad hydrostatic squeeze film damper

PurposeThe purpose of this study is to examine the dynamic performance of an orifice-compensated three-pad hydrostatic squeeze film damper.Design/methodology/approachA numerical model has been developed and presented to study the effect of eccentricity ratio and pressure ratio on the static and dynamic characteristics of an orifice-compensated three-pad hydrostatic squeeze film damper. It is assumed that the fluid flow is incompressible, laminar, isothermal and steady-state. The finite difference method has been used to solve Reynolds equation governing the lubricant flow in film thickness of hydrostatic bearing. The numerical results obtained are discussed, analyzed and compared between three- and four-lobe hydrostatic journal bearings available in the literature.FindingsIt was found that the influence of eccentricity ratio on dynamic characteristics of an orifice-compensated three-pad hydrostatic squeeze film damper appears to be essentially controlled by the concentric pressure ratio. It was also found that the three-pad hydrostatic squeeze film damper has higher stiffness than three and four-lobe hydrostatic journal bearings.Originality/valueIn fact, the results obtained show that this type of hydrostatic squeeze film damper provides hydrostatic designers a new bearing configuration suitable to control rotor vibrations.

Performance analysis of four-pad hydrostatic squeeze film dampers loaded between pads under laminar and turbulent flow conditions

This paper presents a theoretical study of the effects of Poiseuille Reynolds number and eccentricity ratio on the performance of four-pad hydrostatic squeeze film dampers. The finite difference method has been used to solve Reynolds equation based on Constantinescu’s turbulent lubrication theory. The numerical results obtained are analysed and compared between three and four-lobe hybrid journal bearings. The computed results indicate that the performance of a hydrostatic squeeze film damper loaded between pads is significantly influenced by the flow regimes. The results presented in this work can be useful to the bearing designers.

Numerical analysis of a rigid rotor mounted on four-pad hydrostatic squeeze film damper lubricated with micropolar lubricant

The present work deals with a numerical resolution of the modified Reynolds equation using micropolar lubrication theory to study the effects of coupling number and the characteristic length of the micropolar lubricant on the performance characteristics of hydrostatic squeeze film damper, which consists of four hydrostatic pads fed through four capillary restrictors. According to the results, the bearing operating with micropolar lubricant shows an increase in the value of pressure inside the recess. These results suggest that the influence of micropolar effect on the bearing performance is predominantly affected by the pressure ratio. Therefore, the bearing operator must judiciously choose an appropriate value of the pressure ratio in order to get an overall enhanced bearing performance.

Dynamic analysis of a rigid rotor supported by three-pad hydrostatic squeeze film damper lubricated with ferrofluid

This work describes an analytical study on the dynamic behaviour of a three-pad hydrostatic journal bearing lubricated with ferrofluids. Each pad is fed with an external pressure through a capillary restrictor-type hydraulic resistance. Ferrofluid or magnetic fluid is a colloidal dispersion of magnetic nano-particles in a carrier liquid. In this study, a non-linear method was performed using Jenkins model in order to investigate the effect of ferrofluids lubrication on the vibrations amplitude and the transmitted forces of hydrostatic squeeze film dampers. The results presented in this paper showed that the ferrofluid lubrication is useful in controlling the bearing vibrations and transmitted forces. The results illustrated in this work are expected to be quite useful to the bearing designers.

Performance characteristics of a three-pad hydrostatic squeeze film damper compensated with new electrorheological valve restrictors

A numerical analysis is carried out in order to investigate the effect of the electric field on the performance characteristics of a three-pad hydrostatic squeeze film damper compensated with new electrorheological valve restrictors. The bearing design is composed of three identical hydrostatic bearing pads. Each hydrostatic bearing pad is fed with a negative electrorheological fluid through an electrorheological valve. The numerical analysis showed that the viscosity of a smart fluid inside to each electrorheological valve can be controlled by using an electric field in order to control the static and dynamic characteristics. The results presented in this study can be made more useful to control rotor vibrations and force transmissibility especially around the critical speeds.

Nonlinear Dynamic Analysis of a Rigid Rotor Supported by a Three-Pad Hydrostatic Squeeze Film Dampers

The aim of this article is to study the nonlinear dynamic behavior of rigid rotors, supported by a new hydrostatic squeeze film damper (HSFD). A nonlinear model of an HSFD is presented. The results are compared with those obtained from a linear approach that is only valid for small vibrations around the equilibrium position. Compared to the four-pad HSFD, the advantage of using a three-pad HSFD consists of reducing the cost due to the need for a feeding system and the volumetric flow rate used in hydrostatic lubrication. In this study, the effects of the pad dimensions ratios, capillary diameters, and rotational speed on the flow rate, unbalance responses, and transmitted forces are investigated using a nonlinear method and the results are analyzed and discussed. The results obtained show that this type of HSFD provides hydrostatic designers with a new bearing configuration suitable to control rotor vibrations and bearing transmitted forces for high speeds.

Nonlinear Dynamic Behavior of a Flexible Shaft Supported by Smart Hydrostatic Squeeze Film Dampers

The aim of this research is to study the nonlinear dynamic behavior of a flexible shaft supported by smart hydrostatic squeeze film dampers, which are filled with a negative electrorheological fluid (NERF). A nonlinear model of the hydrostatic squeeze film damper has been developed in order to study the effect of the electrorheological fluid on the dynamic behavior of a flexible shaft. The results obtained are discussed and compared with the linear model, which is restricted to only small vibrations around the equilibrium position. A new smart hydrostatic squeeze film damper is proposed to reduce the transient response of the shaft and transmitted forces by applying an electric field to the NER fluid, which results in modifying its viscosity. The results show that it is possible to effectively monitor the electric field and the viscosity of the fluid inside the hydrostatic squeeze film dampers (HSFD) for a better control of flexible shaft vibration and bearing transmitted forces.

Nonlinear Dynamic Behavior of a Rigid Rotor Supported by Hydrostatic Squeeze Film Dampers

Abstract This research project aims to study the nonlinear dynamic behavior of a rigid rotor supported by hydrostatic squeeze film dampers (HSFDs). The investigated HSFD consists of four hydrostatic bearing flat pads fed by capillary restrictors. A nonlinear hydrostatic squeeze film damper model is developed, and the results are compared with those obtained using a linear approach. The effect of unbalance eccentricity on the vibration response and the transmitted force of the HSFD are investigated using the linear and nonlinear models. The results show good agreement between the linear and nonlinear methods when the unbalance force is small. However, as the unbalance forces become larger, the results obtained using the linear models cease to be representative of the real behavior of rotor dynamics and a nonlinear approach must be conducted. The effects of supply pressure, viscosity, pressure ratio, and rotational speed on the response and the force transmitted to the HSFD are investigated using a nonlinear approach.

Analysis of Hydrostatic Journal Bearings With End Seals

An approximate analysis for the pressure field and dynamic force coefficients in turbulent flow, centered hydrostatic journal bearings (HJBs) with fluid inertia and liquid compressibility effects is presented. Results from the analysis show that HJBs with end seals have increased damping, better dynamic stability characteristics, as well as lower flow rates, than conventional HJBs. However, hydrostatic (direct) stiffness may be lost if excessively tight end seals are used. End seals are shown to compensate for the effect of liquid compressibility within the recess volume, and prescribe a net reduction in the whirl frequency ratio for hybrid operation. Hydrostatic squeeze film dampers (HSFD) with end seals are shown to be a viable alternative in applications where a tight control of the bearing leakage is important such as in jet-engines. Furthermore, HSFDs with end seals could be used as an active device to control the available damping in a typical application.