Oil Groove Research Articles

A Numerical Investigation on the Characteristics of the Radial Force in a Cycloid Gerotor Pump

In order to improve the performances of a cycloid gerotor pump, the variations of the radial force induced by different rotating speeds and outlet pressures are analyzed numerically. Using the numerical simulations as a basis, an improved oil inlet and outlet groove structure is proposed. The results show that the radial force decreases with the decrease of the outlet pressure and of the rotor speed. Compared with the original model, the large-end oil inlet line and pressure line of the new oil groove are claw-shaped. This configuration can effectively weaken the pressure changes inside the gerotor pump and reduce accordingly the radial force on the inner rotor.

Advanced simulation of coupled physics in thrust bearings

In hydro power units with very large reversible pump turbines, tilting pad thrust bearings may operate at the edge of the field of experience regarding sliding speed, contact pressure, size, and shape. Here, advanced numerical simulation methodologies offer the possibility to precisely predict the bearing performance and to safely reach guaranteed properties while minimizing the need for experimental investigations. Hence, objective of this work is to develop and validate an advanced method which fully resolves coupled physics in large thrust bearings of reversible pump turbine units. By applying this method, layout tools can be validated and calibrated for an extended design space. Moreover, a better understanding of physical phenomena and how they interact allows for the improvement of design standards. The present contribution introduces an accurate and robust coupling and solution procedure including finite element analyses of thermal and mechanical deformations of pad and thrust runner, mesh motion analyses, and conjugate heat transfer (CHT) analyses. CHT analyses account for flow and heat generation in oil film and groove as well as heat transfer in pad and runner. By applying the procedure to a large bearing investigated at a prototype-sized test rig, all analysis steps are verified and validated using accurate and extended measuring data.

Experimental and numerical investigation on thermodynamic performance of full-floating ring bearings with circumferential oil groove

Floating ring bearing systems in engine-oil lubricated turbochargers commonly withstand severe radial and axial thermal gradients. An engineered thermal management of the heat flows out of the bearing system is paramount in order to ensure the component's mechanical integrity and the reliability of the bearing systems. Therefore, oil flow plays an important role in maintaining an uninterrupted oil film and removing a large fraction of the thermal energy generated by rotational drag and the heat flow disposed from a hot shaft to cool the bearings. The floating rings usually feature circumferential oil groove on their outer surfaces for the increase of flow rate. This work presents experimental and numerical investigations into the operating parameters of full-floating ring bearings with a circumferential oil groove. A comprehensive model, including a transient form of thermal energy balance, is built to analyze relevant bearing parameters like temperature distribution, mechanical power loss, and ring speed ratio for various oil supply conditions. The Reynolds equation is solved by a separation of variables method satisfying the appropriate boundary conditions. For model validation purposes, an extensive experimental study on a cold-gas turbocharger test bench was conducted. As with the test data, the predictions show that oil supply conditions lead to different degrees of influence on the operating parameters of the investigated floating ring bearings.

A numerical analysis and experimental investigation of three oil grooves sleeve bearing performance

PurposeThis paper aims to reveal the cavitation characteristics of three oil wedges sleeve bearing and set the theoretical and experimental basis for defining the oil film boundary condition.Design/methodology/approachComputational fluid dynamics model of three oil wedges sleeve bearings based on the Navier–Stokes equation is set using Fluent considering turbulent situation and two-phase flow theory. The cavitation characteristics of bearing is investigated by taking pictures of experiment.FindingsThe rupture region of oil film and the contours of air volume fraction increase distinctly with the increase of rotating speed and the decrease of input pressure. The critical rotating speed of cavitation occurrence and oil film pressure increases with the increase of input pressure. The change trend of experiment cavitation with the rotating speed and input pressure is consistent with theoretical cavitation in general.Originality/valueThe finite element model of three oil wedges sleeve bearings is established based on the Navier-Stokes calculation equation of the fluid, two-phase flow theory and turbulent model. Sleeve bearing is transparent, the pictures of cavitation can be easily taken by high-speed camera, the cavitation characteristics of bearing is studied by experiment. The cavitation performance of three oil wedges bearings is studied with the change of input pressure and rotating speed, the change trend is basically consistent for theory and experiment. The study on critical rotating speed of cavitation occurrence is benefit for defining the oil film boundary condition.

ANALYSIS OF BEARING CLEARANCE AND WIDTH OF AN OIL GROOVE ON THE CHARACTERISTIC OF FLUID FILM IN HYDRODYNAMIC MAIN CRANKSHAFT BEARINGS

Paper represents an analysis of the influence of oil groove width and bearing clearance on the characteristics of oil film in a hydrodynamic journal main crankshaft bearing. Analysis was performed to define the influence of bearing clearance and dimensions of oil grooves on static characteristics and manufacturability of half-shelf bearings in industrial high-volume production. Computer simulations were made using an ARTbear program, which was developed in Department of Machine Construction and Vehicle Design in Gdańsk Technical University. The analysis allowed defining the correlation between groove geometry and load capacity and working conditions of bearings. Potential opportunities of possible shortening of production time in high-volume production were also indicated.

Analysis of Oil Film Characteristics of Two-Axial Groove Sleeve Bearings

Abstract Based on the finite finite difference method, the Reynolds equation, the flow equilibrium relationship of oil film gradient, and the oil film thickness equation are solved for different groove locations and depths in two-axial groove sleeve bearings. The oil film pressure, extent of the cavitation zone, and carrying capacity of two-axial groove sleeve bearings are computed at different oil groove locations and depths. With the increase of oil groove depth, the oil film pressure of two-axial groove sleeve bearings decreases noticeably, and the bearing capacity decreases gradually. It can be concluded that the maximum oil film pressure and bearing capacity of two-axial groove sleeve bearings are lower than that of the common sleeve bearing. With the groove position moving along the circumferential direction, the oil film pressure peak heights and bearing capacities decrease and then increase. The oil film pressure peak heights and load capacities reach maximum when the position of the two-axial oil groove is about 20° and 200°. It has been proven that different positions of oil grooves show different influences on the extent of the cavitation zone. The first oil groove is always located in the full oil film region, and the second oil groove may be located in the full oil film region or the cavitation region because of the change of distance from the convergent wedge of the bearing. The cavitation area firstly decreases and then increases with the movement of the groove in the circumferential direction.

Fretting-fatigue induced failure of a connecting rod

Abstract This paper analyses the failure of an oblique split connecting rod with serrated joint faces in a medium-speed gas engine at a cogeneration plant. Engine failure occurred suddenly after 20,000 h of service by malfunctioning without the engine control system providing an automatic engine shutdown signal. The failure affected two trains, which were mounted on the same crankpin and to the crankshaft itself. The analysis was concentrated on the connecting rod in which fatigue features on the fracture surface were observed. The location of the fracture in this connecting rod occurred close to the lower joint within the vicinity of the connecting rod axis. Beach marks on the fracture surfaces indicated that the crack initiated from the big end internal surface, approximately 5 mm from the oil groove, away from any geometric stress concentration. To determine the fracture cause, a material characterization and an analysis of the material state near the fracture initiation point was conducted. The analysis was extended to the bearing shells of the damaged trains and to the bearing shells of a connecting rod that did not fail. The results suggest that the mechanism of failure of the engine may have probably been fretting-fatigue produced by the relative micro-movements between the bearing back and the housing bore.

Effect of structural parameters of oil groove on hydro-viscous drive torque with variable rotational speed

PurposeIn this paper, a kind of an oil groove structure which could improve the transmission torque of an oil film was designed, i.e. the width and depth of oil groove gradually decrease with the increase in the radius.Design/methodology/approachEffects of the structural parameters of the oil groove on the hydro-viscous drive (HVD) characteristics with variable rotational speed were investigated by means of numerical calculation.FindingsResearch results show that with the decrease of the width and depth of the oil groove at the outer diameter, transmission torque increases, while the temperature is almost unchanged. Keeping the effective area unchanged, comparing the transmitted torque under the oil groove angle θ2 = 0.5° and θ2 = 4.5°, the former was almost 200 per cent of the latter; the torque transmitted with h2 = 0.05 mm was almost 150 per cent of that with h2 = 0.2 mm.Originality/valueIn this paper, the authors analyze the friction surface of the friction plate between the oil groove, oil distribution and oil film transfer torque from the oil groove structure parameters and found methods to improve the transmission torque. For the first time, the influence of the structural parameters of oil groove on the characteristics of HVD was studied under the condition of variable rotational speed, and a better method to improve the transmission torque was proposed.

Analysis of influencing factors on oil film shear torque of hydro-viscous drive

PurposeThe hydro-viscous drive (HVD) has been widely used in fan transmission in vehicles, fans, and scraper conveyors for step-less speed regulating and soft starting. It is an efficient method to save energy and reduce consumption. This study aims to analyze the influencing factors of oil film shear torque accurately.Design/methodology/approachThe shear torque calculation model of double arc oil groove friction pairs was established. The influence of groove structure parameters on shear torque was analyzed. The interaction between viscosity temperature and shear torque was considered. Meanwhile, the equivalent radius was calculated when the rupture of oil film appeared. Finally, the test rig of torque characteristics was set up. The variance of shear torque with the input rotation speed under different oil film thickness, different oil temperature, and different flow rate was seen.FindingsThe results show that the shear torque increases with the growth of rotation speed. However, the increase of torque is quite gradual because of the effect of the change of viscosity, which is caused by the rise of temperature. The shear torque increases with the decrease of thickness, the increase of inlet flow rate, and the decrease of inlet oil temperature. Meanwhile, when the feeding flow rate is less than the theoretical, the oil film gets ruptured and the shear torque decreases sharply.Originality/valueThe influence on shear torque during full film shear stage in HVD can be achieved much more accurately through both experimental research and theoretical modeling in which groove parameters, influence of temperature, and oil film rupture are considered. Therefore, the shear torque of HVD can be predicted by theoretical model and experimental research in full film shear stage.

Research on the effects of double arc oil groove parameters on oil film torque in hydro-viscous drive

In order to study the influence of double arc oil groove parameters on oil film torque in hydro-viscous drive, the numerical simulation and parameterized analyzing platform were built. The flow field characteristics were carried out using CFX. The parameter analysis platform was integrated with parameterized design of grooves, numerical simulation, and design of experiment (DOE). The effects of groove parameters on output torque were analyzed. The results indicate that the output torque consists of shear torque and impact torque, and the oil film shear torque plays a more important role in total torque. The shear torque is mainly affected by coefficient of effective area and velocity distribution. The velocity distribution and dynamic pressure on sidewalls are the main influencing factors on impact torque. The effect of eccentricity and oil grooves depth on the output torque is positive, but others are negative. In addition, the eccentricity and inner diameter of eccentric circle are sensitive parameters. The effects of oil groove parameters on oil film torque are analyzed accurately using the parameterized analyzing platform that is integrated with CAD, CFX, and DOE. A new method and theoretical foundation are provided for design of complex oil grooves in hydro-viscous drive.

Analysis of Steady State Characteristics for Single-axial Groove Sleeve Bearing

The finite difference method is used to solve the Reynolds equation and the steady state characteristics of single-axial groove bearings are obtained theoretically. It is assumed that the groove is located in four different positions on the top, the bottom, the left and the right of the bearings. The pressure distribution curves and bearing capacity of groove at four different positions are analyzed under the predefined boundary conditions. It has been shown that the oil film pressure distribution and bearing capacity remain unchanged with the common sleeve bearing when the groove is located in the divergence area of oil film; when the groove is located in the convergence area of oil film, the oil film pressure distribution will change greatly. Compared to the sleeve bearing with groove located in the divergence area, the bearing capacity of the sleeve bearing with groove located in the convergence area will decrease to a certain extent, the amplitude of the decrease will change with the different positions of groove in the convergence area of oil film. When oil groove is in the convergence area, though the carrying capacity and pressure decreases, the pressure forms the two pressure strips and the stable performance of sleeve bearing is improved.

Piston skirt friction loss and dynamic analyses based on FEM method

PurposeThe analysis carried out in this study can provide guidance for manufacturers and researchers to design a piston for the development of engines.Design/methodology/approachRunning conditions for pistons have become very severe because of the high combustion pressure and increase in piston temperature in the past 10 years. The precision of the model has a great effect on the power transmission, vibration noise emission. In this paper, the model was established with lubrication and dynamic governing equations, which were solved using finite element method coupled with Runge–Kutta method. A piston of an inline six-cylinder engine was studied, and some structural parameters were used to investigate its effect on the friction loss with lubrication and dynamic motion theory.FindingsBased on the analyses, the effect of the friction load at the oil groove and thermal deformation of piston skirt were added to the model, and some useful information about the friction loss and dynamic characteristics were compared.Originality/valueAll the results will provide guidance for the development of the piston and reduction in the friction loss and wear.

Lubrication performance analysis of crankshaft bush in compressor

Abstract The instability of lubricating oil film has a great effect on the wear of friction pairs and carrying capacity of the parts as well as smooth running of the machine. The lubrication system of crankshaft bush plays an important role in the good operation of compressor unit, reduces production cost while improving production efficiency. In this paper, lubrication performance of the crankshaft bush in compressor was investigated. Parameters involved in the lubrication of bush are studied and analyzed systematically during the stable rotation of crankshaft. Effects of lubrication parameters, such as width diameter ratio, crankshaft speed, inlet pressure, attitude angle and the minimum oil film thickness, on the pressure and distribution of lubricant film were discussed. At last, the optimum value and recommended range of some parameters of bush are determined, and the quantization is carried out within a certain range. The results show that two symmetrical distributions of positive and negative high pressure concentrated areas on both sides of bush oil groove can be formed when the crankshaft is stable. The speed and width diameter ratio have a great effect on the maximum pressure value of oil film. The inlet oil pressure and the minimum oil film thickness are the second, and the inlet attitude angle has little effect. With the increase of width diameter ratio, the maximum pressure value of the positive high pressure concentrated area increases, and the negative areas decreases. With the increase of oil inlet pressure, the maximum oil film pressure increases too but the influence is small. With the increasing of minimum oil film thickness, the maximum pressure and carrying capacity of oil film decrease. If the clearance between crankshaft and bush is too small, oil film can't be formed. For the analysis model in this paper, it is recommended that the radius clearance of bush is 0.04 mm. The inlet oil pressure range of lubricating oil is 0.32–0.36 MPa. Those results can be used in the design, testing and evaluation of the crankshaft system in compressor.

Free modal analysis of wet friction plates with three different kinds of oil groove structures

In this paper, in order to study the vibration characteristics of wet friction plates commonly used with three different kinds of oil groove structures, three-dimensional finite element models were established for no groove wet friction plate, radial groove wet friction plate and the spiral groove wet friction plate. The free modal analyses of the friction plates with three different kinds of oil groove structures are carried out by using the ANSYS Workbench software. The seventh-order to twelfth-order vibration modes are obtained. At the same time, the modal analyses show that the natural frequencies of the non-groove friction plate are larger than the natural frequencies of the other two kinds of friction plates, and the natural frequencies of the radial groove friction plate and the spiral groove friction plate is changed with the change of the number of the oil groove.

Free modal analysis of wet friction plates with three different kinds of oil groove structures

In this paper, in order to study the vibration characteristics of wet friction plates commonly used with three different kinds of oil groove structures, three-dimensional finite element models were established for no groove wet friction plate, radial groove wet friction plate and the spiral groove wet friction plate. The free modal analyses of the friction plates with three different kinds of oil groove structures are carried out by using the ANSYS Workbench software. The seventh-order to twelfth-order vibration modes are obtained. At the same time, the modal analyses show that the natural frequencies of the non-groove friction plate are larger than the natural frequencies of the other two kinds of friction plates, and the natural frequencies of the radial groove friction plate and the spiral groove friction plate is changed with the change of the number of the oil groove.

CFD simulation of air effect on flow field characteristics of hydro-viscous clutch with constant speed difference

The purpose of this paper is to study the air effects on transmission characteristics of hydro-viscous clutch and reveal the distribution law of the flow field of the oil film. The computational-fluid-dynamics (CFD) simulation model of oil film with radial oil grooves between friction pairs is taken as the study object. Considering the air effects, the pressure field, two-phase distribution, transmission torque and temperature field of the oil film are analyzed comparatively by using the CFD technology. The results show that the presence of air changes the pressure and temperature distributions of the oil film. With increase of the absolute rotational speed, the air volume fraction increases and the radius value of the air-liquid boundary decreases under condition of constant speed difference, which makes the coverage rate of the oil film on the surface of the friction disks reduce and the transmission torque of the oil film decrease. These simulation results are attributed to the study of hydro-viscous-drive and its applications. This paper also can provide a theoretical basis for the mechanism of power transmission through oil film in the presence of air effects.

Effects of structural parameters of oil groove on transmission characteristics of hydro-viscous clutch based on viscosity-temperature property of oil film

PurposeThe purpose of this paper is to study the influence of structural parameters of oil groove (such as central angle number, depth and so on) on pressure, flow, load capacity and transmitted torque between friction pairs of hydro-viscous clutch.Design/methodology/approachAccording to the working process of friction pairs of hydro-viscous clutch, mathematical models of hydrodynamic load capacity and torque transmitted by the oil film were built based on viscosity-temperature property. Then analytical solutions of pressure, flow, load capacity and transmitted torque were obtained; effects of central angle of oil groove zone and friction contact zone, oil film thickness, number of oil grooves on pressure, flow, load capacity and torque were studied theoretically.FindingsThe research found that the central angle of oil groove zone, number of oil grooves and oil groove depth have similar effects on flow, which means that with the increase of central angle, number or depth of oil grooves, the flow also increases; pressure in friction contact zone and oil groove zone drops along radial direction, whereas its value in oil groove zone is higher. With the increase of the central angle of oil groove zone, pressure in friction contact zone and friction contact zone rises, and the load capacity increases, whereas the transmitted torque drops. Number of oil grooves has little effect on load capacity. When the oil film thickness increases, its flow increases accordingly, whereas the pressure, load capacity and transmitted torque drops. Meanwhile, the transmitted torque decreases with the increase of number of oil grooves, whereas the oil groove depth nearly has no effects on transmitted torque.Originality/valueIn this paper, mathematical models of hydrodynamic load capacity and torque transmitted by oil film were built based on viscosity-temperature property in the working process of hydro-viscous clutch, and their analytical solutions were obtained; effects of structural parameters of oil groove on transmission characteristics of hydro-viscous clutch based on viscosity-temperature property were revealed. The research results are of great value to the theory development of hydro-viscous drive technology, the design of high-power hydro-viscous clutch and relative control strategy.

Improvement of the damping capacity of the linear damper with an oil groove in the linear guideway system

This article presents an experimental investigation into the damping characteristics of a linear damper with a newly designed oil groove. The damping performance of the damper is tested in four different viscosity grades by the sweep frequency method. And a test bench is used to move the damper for a several kilometers to examine the damping maintenance. The experimental results show that a higher oil viscosity leads to a higher damping capacity of the linear damper, and the increase in the oil viscosity will improve the damping maintenance of the damper. The newly designed oil groove efficiently improved the damping capacity of the linear damper; a proper oil selection will further optimize the effect of the oil groove via minimizing the oil leakage.

Application of Computational Fluid Dynamics Simulation to Squeeze Film Damper Analysis

Squeeze film dampers (SFDs) are used in high-speed turbomachinery to provide external damping to the system. Computational fluid dynamics (CFD) simulation is a highly effective tool to predict the performance of SFDs and obtain design guidance. It is shown that a moving reference frame (MRF) can be adopted for CFD simulation, which saves computational time significantly. MRF-based CFD analysis is validated, then utilized to design oil plenums of SFDs. Effects of the piston ring clearances, the oil groove, and oil supply ports are studied based on CFD and theoretical solutions. It is shown that oil plenum geometries can significantly affect the performance of the SFD especially when the SFD has a small clearance. The equivalent clearance is proposed as a new concept that enables quick estimation of the effect of oil plenum geometries on the SFD performance. Some design practices that have been adopted in industry are revisited to check their validity. Based on simulation results, a set of general design guidelines is proposed.

Load capacity of lubricated bismuth bronze bimetal bearing under elliptical sliding motion

Leaded tin bronze alloys are widely used in heavy machinery bearings operating in boundary and mixed lubrication regions due to the excellent dry lubrication properties of lead. However, restrictions on the use of lead have created an increasing demand for lead-free or low-lead bearing materials. In the present study, suitability of a novel bismuth bronze bimetal material for possible substitution of leaded tin bronze was studied with a special thrust bearing test device, which simulates the contact conditions in the main thrust bearing of mineral crushers. The oil-lubricated test bearings have a flat-on-flat type contact with oil grooves and a constant eccentric motion against a case hardened steel counter plate under a periodically increased axial pressure. The test was continued until a sudden rise in friction, which indicates bearing failure and risk of an imminent seizure. The bismuth bronze showed a load capacity of the same level with the reference material, continuously cast CuSn10Pb10. Characterization by electron microscopy showed that the dry-lubricating bismuth precipitations had a fine grain size and an even distribution, which explains the good load carrying capacity. It was concluded that the bismuth bronze has potential for substituting the leaded tin bronzes in the studied operating conditions.