Squeeze Film Research Articles

Development and Experimental Investigations of Squeeze Film Damper Setup for High Rotational Speeds and Oil Pressure

Development and Experimental Investigations of Squeeze Film Damper Setup for High Rotational Speeds and Oil Pressure

Dynamic Characteristics Study of Elastic Ring Squeeze Film Damper with Rigid–Elastic–Oil Coupled Model

Due to the coupling of the damper journal with the elastic ring and oil film, the elastic ring squeeze film damper (ERSFD) shows better dynamic performance in comparison with the traditional squeeze film damper (SFD). Therefore, a novel rigid–elastic–oil coupled mathematical model was established. The elastic ring deformation, as the key point, is solved according to the planar bending theory. Then, based on the pressure governing equation of the oil film, using the central finite difference method, the oil film pressure was addressed. Meanwhile, the Simpson method was implemented to calculate the dynamic characteristic coefficients (equivalent stiffness and damping Ce) of ERSFD (DCCEs). Also, we analyzed the influence of journal eccentricity, oil film radius clearance, flexibility coefficient and damping hole diameter on the DCCEs, and the results were compared and verified with the existing literature. The sensitivity of each parameter to the DCCEs was analyzed by using the linear regression method. According to the results, the flexibility coefficient has the greatest effect on the DCCEs, followed by the oil film radius clearance. The eccentricity of the journal and damping hole diameter have the least impact. This work will provide a theoretical basis for reflecting on the bearing dynamic characteristics more truly and accurately.

A novel two-dimensional non-contact platform based on near-field acoustic levitation

Near-field Acoustic Levitation (NFAL) is an advanced non-contact handling method with promising applications in the field of manufacturing semiconductors and Micro-Electro-Mechanical Systems. This study presents a novel two-dimensional non-contact platform based on NFAL, constructed by two independent bumped and holed rails. The bumped rail is cross-placed under the holed rail, and the bumps are passed through the holes to ensure two rails being nested and combined. The effective region of the platform is consisted of bumped and non-holed regions simultaneously. So, the distribution of the bumps and holes can be designed to optimize the performance of two-dimensional transportation. Two rails can be vibrated independently to realize one-dimensional transportation and simultaneously to realize two-dimensional transportation. The governing equation of squeeze film, considering the amplitude distribution of the rails, is established to analyze the performances. An experimental test-bed is constructed to test the levitation and transportation performance to verify the numerical study. Both numerical and experimental results prove that the platform based on NFAL is a feasible and easy method to realize non-contact two-dimensional transportation.

Development of non-contact floating mechanism utilizing squeeze film levitation under vacuum environment

Results of an experimental study on the levitation of a light object created by the squeeze-film mechanism under both vacuum and atmospheric conditions are presented and discussed. Two working substances were used, that is vacuum pump oil and ionic liquid. It was determined that vacuum pump oil produced a much higher levitation altitude of the floating light object compared to the ionic liquid. Also, it was established that levitation can be achieved under both vacuum and atmospheric conditions. The levitation height of the light object was slightly higher under vacuum conditions.

Mathematical modelling of the dynamic response of an implantable enhanced capacitive glaucoma pressure sensor

Glaucoma as an eye disease influences the optic nerve, resulting in progressive vision loss and, thus, blindness. For this disease, the most important risk factor is high intraocular pressure. Therefore, it is important to accurately measure the intraocular pressure. The present work aimes to present a mathematical description of a capacitive pressure sensor based on a Micro-Electro-Mechanical-Systems (MEMS) to measure intraocular pressure (IOP). The relatively high working bias voltage of MEMS capacitive pressure sensors restricts their potential applications as implantable sensors. Hence, Polydimethylsiloxane (PDMS) is employed as a porous elastomeric substance between the deformable and fixed electrodes of the capacitor. With a low young modulus and a higher dielectric constant, it reduces the sensor's working bias voltage. The PDMS's permittivity and young modulus are a function of the porosity volume fraction based on displacement in terms of a power law with fractional power constant. The dynamic equation of the microplate's transversal motion is used in the developed model, taking mid-plane stre-tching into account along with the generated force owing to the PDMS film squeezing. To decompose the governing nonlinear equation, a weak formulation is used with appropriate basis functions, thus integrating the attained ordinary differential equations over time. The sensor response to static pressure and step-wise alteration of the applied pressure is examined by dynamic and static analysis. The results of pull-in voltage reveal that using the PDMS as a dielectric causes a considerable reduction. Additionally, the effect of the PDMS elasticity on the capacitance and displacement was assessed along with the effects of the geometrical parameters on the sensor response.

Optimal shape design of spherical squeeze film bearings using genetic algorithms

The optimal shape design of hydrodynamic axisymmetric spherical bearings under conditions of transient axisymmetric pure squeeze is investigated using genetic algorithms (GA). The optimization problem is to determine the radial clearance shape which maximizes the load impulse resulting from transient ball motion to a target minimum film thickness specification. For fully-hemispherical cups, non-dimensional analysis shows that GA-based optimal designs yield significantly larger non-dimensional impulse values when compared with those obtained either randomly or from optimal ellipsoidal geometry. A sample design application with specified load history shows that an optimal GA-inspired composite clearance specification amenable to fabrication can be constructed from preferred features obtained from the GA-based optimal shapes. The optimal composite shape design is shown to provide significantly better bearing performance, as measured by minimum film thickness, after a specified time interval than an optimal ellipsoidal design. The optimal composite shape design is also found to be less sensitive to realistic deviations in clearance shape, load impulse, and viscosity variation when compared with similar variations to an optimal ellipsoidal cup design.

Dynamic Forced Performance of an O-Rings Sealed Squeeze Film Damper Lubricated With a Low Supply Pressure and a Simple Method to Quantify Air Ingestion

Abstract Contemporary squeeze film dampers (SFDs) in air-breathing engines are short in length to limit weight and part count and lubricated with a low feed pressure to reduce oil storage and pumping power. In SFDs, O-rings (ORs) restrict side leakage and increase the viscous damping while a adding a modest centering stiffness. Continuing a long-term project characterizing SFDs for aircraft engines and extending the original work (San Andrés and Rodríguez, 2021, “On the Experimental Dynamic Force Performance of a Squeeze Film Damper Supplied Through a Check Valve and Sealed With O-Rings,” ASME J. Eng. Gas Turb. Power, 143(11), p. 111011) the paper details measurements of the forced performance of an OR sealed damper (OR-SFD) with diameter D = 127 mm, land length L = 0.2 D, and radial clearance c = 0.0022 D. Lubricant ISO VG 2 supplied at 0.69 bar(g) fills an upstream oil plenum and flows into the middle of the land through a single orifice configured with a check valve. Measurements of applied single-frequency dynamic loads, along with the ensuing damper displacements and accelerations serve to identify the parameters of the test structure, ORs, and SFD. The tests encompass centered whirl motions with amplitude r = 0.05–0.45c, and a range of whirl frequencies, ω = 10–130 Hz. Note the squeeze velocity vs = rω reaches 102 mm/s. The ORs force coefficients are nearly invariant with frequency but do depend on the orbit amplitude. The ORs' stiffness (KOR) decreases by 75% as the motion amplitude increases, r → 0.45c, likely due to the large elastic deformations and slow recovery of the ORs material. For small amplitude motions (r/c = 0.05 and 0.10), the ORs damping coefficient (COR) is ∼10% of the overall coefficient for the lubricated system (CL), while for r/c > 0.25, COR ∼ 0.03CL. For small amplitudes of whirl (r ≤ 0.25c), the SFD experimental viscous damping (CSFD) and added mass (MSFD) coefficients, identified over a shorter frequency range (vs<30 mm/s) equal theoretical magnitudes for a fully sealed damper. As the orbit size grows to r = 0.45c MSFD drops nearly by 75% and CSFD decreases by ∼40% due to the onset of both lubricant cavitation and air ingestion occurring for squeeze velocities vs ≥ 24.5 mm/s, as also seen in the recorded dynamic pressures and video recordings of a bubbly mixture leaving the damper. A comprehensive flow model predicts CSFD and MSFD about 8% and 12% larger than the experimentally identified coefficients. A novel approach enables the estimation of the gas volume fraction (GVF) generated in the damper which rapidly increases as vs grows. The simple procedure draws into a deflated balloon the material contents in the squeeze film, weighs the sample, and identifies its volume to produce an estimate of the GVF. The procedure to quantify the GFV will assist in the validation of predictive tools.

Investigation on the dynamic characteristics of a rotor-damper-casing coupling system under diving-climbing maneuver

The thin-walled casing and squeeze film damper (SFD) of an aero-engine have significant effects on the vibration of the rotor during maneuvering flight. However, few studies have been conducted on the vibration responses of a rotor-damper-casing coupling system under this condition. This paper uses Lagrange's principle to derive the equation of motion for a rotor system that considers the flexible casing and static eccentricity of the SFDs during maneuvering flight. The model of a casing is established, and the frequency response functions (FRFs) with pre-stress are calculated by converting the flight parameters to pre-stress. Then, the FRFs are generated for various flight statuses and combined with the rotor finite element model using the linear interpolation method. The vibrations of a dual-rotor system during the diving-climbing maneuver are calculated by the Hilber-Hughes-Taylor-α (HHT-α) method. The results indicate that the deflection will appear in the rotor vibrations during maneuvering flight. The flexible supports of a casing make the vibration transfer between the High Pressure and Low Pressure rotors, and there are harmonic and subharmonic components in the vibrations of a rotor-damper-casing coupling system. Due to the influence of a flexible casing, the vibrations of a rotor vary at different speeds under the diving-climbing maneuver, even if the speed is far from the critical speed. This study illustrates the significance of considering the flexible casing and the SFD during maneuvering flight.

Dynamic characteristics analysis of an aeroengine rotor system subjected to aerodynamic excitation

This paper aims to investigate the dynamic characteristics of an aeroengine rotor subjected to aerodynamic excitation. Firstly, the dynamic model of the turbo-shaft engine rotor system is established by means of finite element (FE) method, taking into account the blade-tip clearance-induced aerodynamic force and oil-film force induced by squeeze film damper. Next, the critical speeds and mode shapes of the rotor are achieved by calculation, simulation and experiment to illustrate the validity of the established model. Then, using bifurcation diagram, rotating orbit and time-domain waveform, the dynamic responses of the turbo-shaft engine high-pressure (HP) rotor with aerodynamic excitation are analyzed, and the effects of blade-tip clearance, inlet and outlet angles on the dynamic responses of the rotor are discussed, respectively. The numerical results reveal that the system maintains a stable-periodic motion at low-speed region. In contrast, at high-speed region, there is a noticeable appearance of instability. Besides, the magnitude of the response decreases with the growth of the blade-tip clearance. The growth of the inlet angle will result in an increase of the magnitude of the response, and the magnitude of the response reduces with the growth of the outlet angle. The aerodynamic force at resonance is greater than that at non-resonance. The research results can assist in understanding the dynamic characteristics of the rotor subjected to aerodynamic excitation, and provide theoretical guidance for the structural design of an aeroengine rotor system.

Dynamic characteristics of open-ends squeeze film dampers with air ingestion

Abstract In order to explore the air ingestion characteristics of the open-ends squeeze film dampers (SFD), a 3D computational fluid dynamics solution model of the SFD was proposed based. The setting of opening boundary conditions was considered, which was verified experimentally by the bidirectional excitation. The results revealed that with the same precession frequency, the smaller radial clearance leads to the greater oil film damping. An increasing oil supply and oil holes led to the smaller air ingestion range at the end. The design guideline for the open-ends SFD was investigated in the present work.

Mathematical Model to Study the Squeeze Film Characteristics of Diseased Human Synovial Knee Joint

Synovial fluid functions as a biological lubricant and lubricates articular cartilage to reduce friction and wear. Lubricin and hyaluronic acid are the primary components of synovial fluid responsible for its lubricating properties. The loss of properties in synovial fluid and articular cartilage due to aging and activities can restrict mobility in synovial joints, resulting in the degradation of articular cartilage and ultimately leading to pathological synovial joints, which is a major cause of disability. Thus, research on synovial joints remains crucial, and despite previous investigations on synovial joint lubrication, there are several issues related to squeeze film lubrication that require further attention. The Newtonian model of squeeze film lubrication in synovial joints needs to be extensively studied. In this study, lubrication and other related properties of synovial fluid are studied theoretically. In this paper, we have studied the flow of synovial fluid in the diseased synovial joint. Further, we have studied the effect of the viscosity of the synovial fluid, the permeability of articular cartilage, thickness of articular cartilage, and fluid film thickness on the characteristic of the squeeze film formed between the articular cartilages of the diseased human knee joint. The flow of synovial fluid is modeled by considering it as a viscous, incompressible and Newtonian fluid. We have derived the modified Reynolds equation using the principle of hydrodynamic lubrication and continuum mechanics theory and solved it by applying the suitable boundary conditions according to the physical considerations. Subsequently, we obtained the expression for pressure distribution in fluid film, load-bearing capacity, and squeeze time and have done the theoretical analysis on these properties for different parameters. Pressure increases with squeeze velocity and viscosity of the synovial fluid and decreases with permeability and fluid film thickness. Human knee joint becomes diseased due to excessive pressure, and the mobility of the knee joint decreases. The load capacity increases with viscosity and squeeze velocity and decreases with permeability resulting in the reduction of the load-carrying capacity of the knee joint in diseased conditions. Moreover, the squeeze time also increased in the diseased state of the joint.

Wavelet lifting method for the numerical solution of micropolar lubrication problem of porous journal bearing

The pivotal aim of this paper is to develop the wavelet lifting method for the numerical solution of the micropolar lubrication problem of porous journal bearings. To ensure the applicability of the proposed method initially, test problems are considered and the numerical findings are presented in figures and tables elucidate that, the proposed method is more efficient and promising with the consumption of lesser computational CPU time. Subsequently, the effect of micropolar fluid on the porous journal bearing is analyzed by solving the corresponding non-dimensional Reynolds equation of the lubrication problem is considered. The obtained results for pressure distribution and load carrying capacity with varied parameters show that the squeeze film pressure and load carrying capacity are significantly increased by the micropolar fluid effect as compared to the Newtonian case.

Dynamic Characteristics of MR Fluid Short Squeeze Film Damper in Terms of Reynolds Number

Magnetorheological (MR) fluids are suspensions of fine micron-sized particles suspended in an appropriate carrier medium. Their rheological properties can be controlled by the application of an appropriate magnetic field and can be used in a variety of applications where damping and stiffness characteristics need to be controlled at a particular excitation frequency, based on the requirements. This cannot be accomplished with conventional fluids and thus MR fluids find application in squeeze film dampers of aircraft jet engines to provide variable damping in accordance with the magnetic field, at a particular excitation frequency. Limited information is available on the stiffness and damping characteristics of magnetorheological fluid squeeze film dampers in the literature. This paper provides information on the stiffness and damping characteristics of MR fluids used as external damping medium in Squeeze film Dampers in terms of the Reynolds number of the squeeze film. The paper calibrates the stiffness and damping characteristics of particular magnetorheological fluid squeeze film damper theoretically in terms of Reynolds number of the squeeze film for two clearance and L/D ratios operating at low eccentricity ratios, using a constant field viscosity model. The stiffness and damping characteristics are found to decrease with the increase in Reynolds number. The Reynolds number of the squeeze film is very low, highlighting the fact that the flow in the film has ceased and has solidified in accordance with the literature. The dynamic coefficients are presented in the form of empirical equations based on the theoretical investigations for different clearance, L/D ratio and eccentricity ratio, in terms of Reynolds number of the damper and enables its easy evaluation for a particular damper configuration by a mere knowledge of the Reynolds number of the squeeze film. The results assist the designer in obtaining the stiffness and damping characteristics of the squeeze film damper, based on the Reynolds number. Alternatively, the stiffness and damping characteristics of the squeeze film damper are calibrated in terms of Reynolds number for particular damper configurations. However, the research focuses on the stiffness and damping coefficients for a limited number of damper configurations under a constant excitation frequency whilst a large number of clearances, L/D ratios and excitation frequencies have not been taken into account .This research is thus intended only to showcase the method of approach by selecting finite number of damper configurations. Future work should be focused towards investigations that present the empirical equations for the entire range of clearance, L/D ratio and eccentricity ratio.

Dynamic analysis of the rotor system with elastic ring squeeze film damper considering oil film temperature

Dynamic analysis of the rotor system with elastic ring squeeze film damper considering oil film temperature

Performance analysis of annular disks with non-Newtonian Rabinowitsch fluid model: Influence of squeeze film pressure, surface roughness, porosity and viscosity variation

In various systems of energy, such as turbo-machinery and viscous-lock system, squeeze film plays a crucial role for improving transport systems. The importance of the aforementioned applications led us to explore the physical behavior of Rabinowitsch fluid flow for several values of viscosity, [Formula: see text], load capacity [Formula: see text], nonlinear factor, [Formula: see text], dimensionless film thickness [Formula: see text], dimensionless radius of the capillary tube [Formula: see text], dimensionless thickness of porous pad [Formula: see text]), inner and outer radius ratio [Formula: see text], roughness parameter [Formula: see text] through a squeeze film with two rough porous annular discs. Five-point Gauss quadrature integral formula has been used to examine the characteristics of annular discs, and small perturbation method has been used to discretize the governing Rabinowitsch fluid flow (RFF) equations. The modified Reynolds equation for rough, porous and viscosity change with film thickness is developed using Christensen’s stochastic theory, modified Darcy’s theory and the association between viscosity and film thickness agreement. The impacts of [Formula: see text] on the behavior of porosity and viscosity variability of RFF have been visually depicted in terms of film pressure, load capacity and squeeze reaction time of annular discs. It has been determined that for RFF with variable viscosity and roughness parameter on a porous media, the performance of the annular disks enhances for [Formula: see text] (dilatant lubricant), and diminishes for [Formula: see text] (pseudo-plastic lubricant). It has been found that the film pressure in case of dilatant lubricant is increased by the influence of Rabinowitsch fluids on porous walls, but the behavior of pseudo-plastic lubricants has an opposite tendency relative to Newtonian lubricants. It has also been found that the impact of variability in porosity, roughness and viscosity diminishes the load-carrying capacity (LCC) with increased film thickness than the case of nonporous, smooth surface and constant viscosity of Rabinowitsch fluid.

Effects of Surface Roughness and MHD on Squeeze Film Characteristics for Various Finite Porous Plate Geometries with Couple-Stress Fluid

Effects of Surface Roughness and MHD on Squeeze Film Characteristics for Various Finite Porous Plate Geometries with Couple-Stress Fluid

Vibration attenuation characteristics of squeeze film dampers in spiral bevel gear systems

A central drive bevel gear system of aero-engines extracts power from a high-pressure rotor. The high speed of the high-pressure rotor aggravates the gear system's vibration. This work adopts squeeze film dampers (SFD) as damping devices to suppress excessive vibration of the spiral bevel gear rotor system. This paper establishes the general Reynolds equation of SFD and calculates the nonlinear oil-film force of SFD in real-time based on the finite element method. Besides, the finite element method and Timoshenko beam element are employed to model the flexible gear shaft. Then, the dynamic model of the spiral bevel gear system supported by SFDs is established, including the nonlinear oil-film force of SFD and time-varying meshing stiffness of the gear system. The dynamic response of the spiral bevel gear system is analyzed theoretically and experimentally to study the vibration attenuation characteristics of SFD. The findings indicate that SFD can effectively suppress the vibration amplitude of the system at high speeds. The theoretical analysis and experimental amplitude are within an order of magnitude, and the changing trend is consistent.

Squeeze Film Effect and Its Influence on the Lubrication Characteristics of Slipper Oil Film under Pressure Pulse

This study aims at the lubricant film between the slipper and swashplate of an axial piston pump. Based on a single piston/slipper assembly model, a mathematical model for the squeeze film effect is developed according to the pressure-flow transfer process as well as the dynamics of the piston/slipper assembly. The squeeze film effect on the slipper lubricant film has been predicted by nonlinear numerical calculations and computational fluid dynamic (CFD). The slipper lubricant film thickness and leakage flow, sealing land pressure distribution, and load carrying capacity are evaluated as important parameters to indicate the performance of slipper oil film. The influence of piston/slipper assembly geometric parameters, oil compressibility, and oil viscosity on the squeeze film effect under pressure pulse has been studied, and the effect of squeeze film speed on the support force of slipper lubricant film has been given out.

Optimization of Control Parameters of Magnetorheological Squeeze Film Dampers to Minimize the Vibration Amplitude of Rotors Passing the Critical Speed

Rotors are often coupled with a stationary part by rolling element bearings. To suppress their excessive vibration, the bearings are inserted in squeeze film dampers. The control of damping in the support elements offers the possibility to minimize the oscillation amplitude of accelerating or decelerating rotors, passing the regions of critical speeds. The controllable damping effect can be achieved if the squeeze film dampers are lubricated with magnetorheological oil. The change in the applied current feeding the electric coil changes magnetic induction in the damper gap, which changes the oil damping properties. The minimum vibration amplitude of the rotor running up or down through the resonance area is accomplished if the current increase or decrease is not sudden, but if it is distributed in some time interval. This article concentrates on determination of the optimum parameters of this manipulation. The developed procedure leads to solving an unconstrained optimization problem with the implicit objective function. The evolution method was used for its solving. In the investigated case, the proposed procedure made it possible to reduce maximum vibration amplitude by about 40% compared with the uncontrolled current decrease. The main contribution of the conducted research work is presentation of a new and original procedure for controlling the damping effect in the rotor supports. It provides a new idea to the designers and engineers regarding how to minimize amplitude of the rotor vibration when passing the critical speed. In addition, the article points to a new area of utilization of controllable magnetorheological squeeze film dampers.

On the effect of temperature in friction force measurements for a simplified piston cylinder set-up: Squeeze film combined with minimum oil film thickness measurements and viscosity index effect

The lubricated interface at the piston-ring and liner and its interaction with different lubricants and testing conditions is examined in terms of experimental measurements that show the minimum oil film thickness developed at the lubricated or depending on conditions partly lubricated conjunction and the surface interaction intensity, as measured from the friction sensor. An analysis is carried out with the use of different parameters for the experiments as well as different lubricants in a simplified piston-ring simulation test rig. This analysis is further enhanced with the squeeze film effect investigations close to the stroke reversals and together with cavitation initiation and load-carrying effect results from previous experimental data, light is shed on the interacting surface’s behaviour at the different lubrication regimes. Another parameter, the viscosity index of the lubricant is used as an indication of the effects of squeeze film shift and friction force measurements and how the load and temperature effect are influencing the squeeze film.