A Journal Bearing With Variable Geometry for the Reduction of the Maximum Amplitude During Passage Through Resonance

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Athanasios Chasalevris ◽  
Fadi Dohnal
Keyword(s):  
Film Thickness ◽  
Relative Motion ◽  
Vibration Amplitude ◽  
Journal Bearing ◽  
Dynamic Properties ◽  
Maximum Amplitude ◽  
Variable Stiffness ◽  
Fluid Film ◽  
Bearing Ring ◽  
Fluid Film Thickness

A concept for a journal bearing with variable stiffness and damping properties is developed in order to decrease the vibration amplitude of a rotor-journal bearing system during passage through resonance. The introduction of an additional fluid film thickness in the bearing is proposed in this work in order to alter the dynamic properties in the bearing. The bearing ring is divided into two parts with the upper part being fixed with the housing and the lower part being flexibly mounted by a preloaded spring in parallel with a viscous damper. This allows relative motion between the two parts of the bearing ring. The relative motion introduces an additional fluid film zone in the bearing under the passive displacement of the lower part due to increased impedance forces that are developed in the lubricant film at resonance operation. The general concept is to change the system's damping and stiffness coefficients using this extra fluid film thickness only when the system passes through its critical speed in order to quench the vibration amplitude. For rotational speeds outside of the resonant regions, the bearing is considered to be fixed in order to behave as it was designed under the nominal loading operational conditions.

Performance Analysis of a Nonrecessed Hybrid Conical Journal Bearing Compensated With Capillary Restrictors

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Prashant G. Khakse ◽  
Vikas M. Phalle ◽  
S. S. Mantha
Keyword(s):  
Performance Analysis ◽  
Film Thickness ◽  
Journal Bearing ◽  
Fluid Film ◽  
Load Parameter ◽  
Radial Load ◽  
Wide Range ◽  
Bearing Stiffness ◽  
Fluid Film Thickness ◽  
Film Stiffness

The present paper deals with the performance analysis of a nonrecessed hole-entry hydrostatic/hybrid conical journal bearing with capillary restrictors. Finite element method has been used for solving the modified Reynolds equation governing the flow of lubricant in the clearance space of journal and bearing. The hole-entry hybrid conical journal bearing performance characteristics have been depicted for a wide range of radial load parameter (W¯r  = 0.25–1.5) with uniform distribution of holes at an angle of 30 deg in the circumferential direction. The numerically simulated results have been presented in terms of maximum fluid film pressure, minimum fluid film thickness, lubricant flow rate, direct fluid film stiffness coefficients, direct fluid film damping coefficients, and stability threshold speed. However, the proposed investigation of nonrecess hole-entry hybrid conical journal bearing shows important performance for bearing stiffness and minimum fluid film thickness at variable radial load and at given operating speed.

Linking Rigid and Flexible Multibody Systems via Thin Fluid Films Actively Controlled

2008 ◽  
Author(s):  
Edgar A. Estupinan ◽  
Ilmar F. Santos
Keyword(s):  
Film Thickness ◽  
Multibody Systems ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Fluid Films ◽  
Thin Fluid ◽  
Dynamically Loaded ◽  
Reaction Forces ◽  
Fluid Film Thickness

This work describes in details the steps involved within the mathematical modelling of multibody systems (rigid and flexible) interconnected via controllable thin fluid films. The dynamics of the mechanical components are described with help of multibody dynamics and finite element method. In this paper, the methodology is applied to reciprocating machines such as hermetic reciprocating compressors and internal combustion engines. In previous studies [1], it has been shown that for a light duty vehicle, the friction losses may reach until 48% of the total energy consumption of an engine and from that, almost 30% are coming from bearings and crankshaft. Therefore, considering that the dynamics of the fluid films in the journal bearings can be actively controlled by means of different types of actuators, allowing significant reduction of wear and vibrations, one of the aims of this paper is to study the feasibility of applying active lubrication to the main journal bearings of reciprocating machines. In this framework the paper gives a theoretical contribution to the combined fields of fluid-structure interaction and active vibration control. The hydrodynamic pressure distribution for an active lubricated finite journal bearing dynamically loaded can be calculated by numerically solving the modified Reynold’s equation [2], by means of finite-difference method and integrated over the pressure area in order to obtain the dynamic reaction forces among components. These forces are strongly nonlinear and dependent on the relative kinematics of the system. From the point of view of active lubrication and specifically considered the case of a dynamically loaded journal bearing, the injection pressure should be controlled in the time domain. However, taking into account that the pressures and reaction forces in a reciprocating machine have a cyclic behaviour, the fluid film thickness of the main bearings may be modified by controlling the oil pressure injection, depending on the crank angle and the load bearing condition. It can be mentioned that the pressure and flow may be controlled by mechanical cam systems, piezoelectric nozzles [3] [4] or servovalves [5] [6], therefore, an adequate control strategy has to be defined. The fluid film forces are coupled to the set of nonlinear equations that describes the dynamics of the mechanical system. Such a set of equations is numerically solved giving some insights into the following parameters: a) maximum fluid film pressure, b) minimum fluid film thickness, c) maximum vibration levels and d) viscous frictional forces. The behaviour of such parameters is investigated when the system operate with conventional hydro-dynamic lubrication, passive hybrid lubrication and controlled hybrid lubrication.

Influence of wear on the performance of hole-entry hybrid misaligned journal bearing in turbulent regime

2014 ◽  
Vol 66 (4) ◽  
pp. 509-519 ◽  
Author(s):  
Nathi Ram ◽  
Satish C. Sharma
Keyword(s):  
Film Thickness ◽  
Design Parameter ◽  
Journal Bearing ◽  
Fluid Film ◽  
Turbulent Regime ◽  
Laminar Regime ◽  
Content Type ◽  
Fluid Film Thickness ◽  
System Operating ◽  
Bearing System

Purpose – The present work aimed to study analytically the influence of wear on the performance of a capillary-compensated hole-entry hybrid misaligned journal bearing system operating in a turbulent regime. The numerically simulated results are presented for the chosen values of restrictor design parameter, Reynolds numbers, wear depth and misalignment parameters. Design/methodology/approach – The wear caused on the bearing surface due to start/stop operations is modeled using the Dufrane’s abrasive wear model. The modified Reynolds equation based on Constantinescu’s lubrication theory is solved using finite element method together with capillary restrictor flow equation. Findings – It is found that the value of minimum fluid-film thickness increases significantly for a constant value of restrictor design parameter when unworn aligned bearing operates in turbulent regime vis-à-vis laminar regime. Further, it has also been observed that when a worn bearing operates in laminar/turbulent regimes, the reduction in the value of minimum fluid-film thickness is more due to journal misalignment as compared to the aligned bearing operates in laminar regime. Originality/value – The present work is original concerning the performance of worn hole-entry hybrid misaligned journal bearing system operating in turbulent regime. The results are expected to be quite useful for the bearing designer.

Rheological Behaviors of Pressure-Driven Radial Flow

2007 ◽  
Author(s):  
Z. Xie ◽  
Q. Zou ◽  
D. Yao
Keyword(s):  
Film Thickness ◽  
Radial Flow ◽  
Practical Interest ◽  
Fluid Film ◽  
Fluid Viscosity ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Shear Dependent Viscosity ◽  
Fluid Film Thickness ◽  
Pressure Driven

The characteristics of fluid flows confined within microscale space are of theoretical and practical interest [1]. Such flow includes the thin lubrication films, the liquid flow between biological cells, and the flow of polymer melts in a micro-injection molding machines, etc. A pressure-driven radial flow microrheometry (PDRFM) is used to characterize high-shear microscale fluids. The shear-dependent viscosity of the pressure-driven radial flow is modeled to investigate the possible size effect on the fluid viscosity. In the modeling, the surface shear rate and surface shear stress at the edge of the radial flow are expressed in terms of three measurable parameters, i.e. the flow rate, the loading force, and the fluid film thickness. By decreasing the fluid film thickness to microscale level, this model can be used to study the microscale effect of any homogeneous fluids. The analysis has been verified by using CFD simulations as digital testing platforms. Furthermore, the preliminary experimental results of Newtonian and non-Newtonian flows also proved the rheological modeling.

Surface Deformations Enable High Pressure Operation of Axial Piston Pumps

2011 ◽  
Author(s):  
Matteo Pelosi ◽  
Monika Ivantysynova
Keyword(s):  
Film Thickness ◽  
Material Properties ◽  
Fluid Film ◽  
Cylinder Block ◽  
Steel Cylinder ◽  
Elastic Deformations ◽  
Piston Cylinder ◽  
Fluid Film Thickness ◽  
The Impact ◽  
Axial Piston

In this paper, a fully coupled fluid-structure interaction and thermal numerical model developed by the authors is used to demonstrate the impact of surface elastic deformations on the piston/cylinder fluid film thickness and on the overall axial piston pump rotating kit performance. The piston/cylinder interface is one of the most critical lubricating interfaces of axial piston machines. This interface fulfills simultaneously a bearing and sealing function under oscillating load conditions in a purely hydrodynamic regime. It represents one of the main sources of energy dissipation and it is therefore a key design element, determining axial piston machine efficiency. In the past years, the research group of the authors studied the impact of advanced micro surface design and fluid film thickness micro alteration in the piston/cylinder interface through extensive simulations and experiments. However, the numerical models used did not include the influence of surface elastic deformations, heat transfer and therefore material properties on the piston/cylinder interface behavior. Hence, the aim of this paper is to show the alterations on fluid film thickness and on the consequent coupled physical parameters due to the solid boundaries pressure and thermal surface elastic deformations. A simulation study considering two different material properties for the cylinder bores is performed, where a steel cylinder block and a steel cylinder block with brass bushings are separately studied. Piston/cylinder gap pressure field and coupled gap surface elastic deformations due to pressure and thermal loading are shown for the different materials. The impact of the different materials behavior on lubricating interface performance is discussed.

Theoretical Studies of a Continuously Adjustable Hydrodynamic Fluid Film Bearing

2001 ◽  
Vol 124 (1) ◽  
pp. 203-211 ◽  
Author(s):  
J. K. Martin ◽  
D. W. Parkins
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Solution Procedure ◽  
Fluid Film ◽  
Theoretical Studies ◽  
Analysis Model ◽  
Operating Characteristics ◽  
Hydrodynamic Bearing ◽  
Wide Range ◽  
Fluid Film Thickness

Principles of a continuously adjustable hydrodynamic bearing are described together with an analysis model for studying its theoretical performance. The model included an expanded form of the governing Reynolds equation which took account of non-uniform variations in the fluid film thickness. A solution procedure was devised whereby for a given set of adjustment conditions, simultaneously converged fields of fluid film thickness, temperature, viscosity and pressure would result, together with oil film forces. A wide range of operating characteristics were studied with results predicting advantages and benefits over conventional hydrodynamic bearings.

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