Oil Film Pressure Distribution Research Articles

Experimental study on the pressure distribution of piston/cylinder lubricating interface based on time domain location method

The piston/cylinder lubricating interface is one of the most critical components in piston pumps. The characteristics of the interface, such as pressure distribution, leakage flow and viscous friction, etc., have significant effect on the performance of the piston pump. Previous experiments obtained data distribution by installing pressure sensors on a fixed cylinder block. However, too many measurement points on the cylinder block may disrupt the lubricating film; insufficient measurement points will result in incomplete oil film pressure distribution. This paper presents a novel time domain location testing method which a measuring point is placed on each cylinder surface as a time-domain calibration reference, enabling the acquisition of the pressure distribution over one shaft revolution. Real-time pressure between the piston and cylinder is measured under various operating conditions. Further research results show that the pressure distribution obtained through this method exhibits a high degree of conformity with the simulation results.

Friction and wear performances of 7075 aluminum alloy surface with V-shaped microtexture via numerical simulation and experimental characterizations

Purpose The purpose of this study is to design and process the optimal V-shaped microstructure for 7075 aluminum alloy and reveal its wear resistance mechanism and performance. Design/methodology/approach The hydrodynamic pressure lubrication models of the nontextured, V-shaped, circular and square microtextures are established. The corresponding oil film pressure distributions are explored. The friction and wear experiments are conducted on a rotating device. The effects of the microstructure shapes and sizes on the wear mechanisms are investigated via the friction coefficients and surface morphologies. Findings In comparison, the V-shaped microtexture has the largest oil film carrying capacity and the lowest friction coefficient. The wear mechanism of the V-shaped microtexture is dominated by abrasive and adhesive wear. The V-shaped microtexture has excellent wear resistance under a side length of 300 µm, an interval of 300 µm and a depth of 20 µm. Originality/value This study is conductive to the design of wear-resistant surfaces for friction components.

Experimental and numerical study on the dynamic and lubrication characteristics of the rotor-bearing-frame system in a variable-speed scroll compressor

The variable-speed scroll compressors can adapt to the various demands of heating and cooling capacity, and the rotational speeds significantly influence the rotor dynamic and bearings lubrication, which might cause performance and reliability issues. In this paper, numerical models for the rotor-bearing-frame system are developed by coupling the Reynolds equation, rotor dynamic equation, and the flexibility equation of the frame. The experimental apparatus is also established to directly measure the journal displacement response in the hermetic high-pressure shell of the compressor. The predicted journal center trajectories are compared with the experimental results and they show good agreement. Results show that the whirl radius decreases with the increase of rotational speed at the measuring point, while the opposite tendency can be observed at the bottom of the main bearing. Transient dynamic analysis of the rotor shows that the tilting and deformation of the rotor vary with respect to different rotational speeds. The displacement of the crank part could lead to the separating tendency between orbiting and fixed scrolls through the coupled orbiting bearing, especially at the lower rotational speed, due to the pull of main balance weight. The numerical results also reveal that the distribution of oil film pressure is dominated by the squeeze effect due to the relatively stable magnitude but the variable direction of loads on the shaft. The influence of the deformation of the cantilevered bearing frame on the oil film thickness is significant but the maximum deformation moves downward at the higher rotational speed.

Hybrid lubrication model study of slip ring combination seal under the influence of frictional heat

This paper presents an experimental and theoretical investigation into the factors influencing the sealing performance of combined slip rings. Factoring in the frictional heat from micro convex bodies and convective heat exchange between the slip ring, oil film, and air, we formulate a thermoelastic flow hybrid lubrication model for the combined slip ring seal. This model calculates the distribution of oil film thickness, pressure, temperature, velocity, and viscosity in the sealing zone, drawing on the generalized average Reynolds equation and the transmembrane average energy equation, in conjunction with the heat conduction equation of the slip ring. Utilizing the Archard wear model, we also examine the wear characteristics of the combined slip ring seal, providing insights into seal wear under these conditions. The model enables an analysis of the interplay between parameters and their impact on seal performance. The method proposed accurately predicts friction and leakage in line with experimental data, thereby providing a theoretical foundation for further numerical investigation of seal characteristics.

Dynamic analysis of magnetorheological damper incorporating elastic ring in coupled multi-physical fields

The elastic ring assumes a multifunctional role, crucially providing support and reshaping oil-film thickness distribution in applications such as squeeze film dampers, demonstrating its practical efficacy. In this work, a magnetorheological damper (MRD) incorporating an elastic ring is proposed for the first time to improve the performance of damper. The innovative configuration of the elastic ring magnetorheological damper (ERMRD) is fabricated and integrated into a test platform of rotor system. The multi-filed coupling dynamic model of ERMRD is developed involving magnetic field interactions governed by Kirchhoff law, magnetorheological fluid flow dynamics derived from lubrication theory, and the elastic ring deformation based on thin plate theory. The intricate influence mechanisms of elastic ring and excitation current on oil-film characteristic of ERMRD, encompassing oil-film pressure, oil-film force, oil-film stiffness and damping, are investigated in detail. To substantiate the capabilities of ERMRD, it is implemented within the rotor system and a coupled dynamic model is established using Lagrange equation. This is followed by an in-depth analysis of the dynamic response using the Newmark-β method, including a comparative assessment with the conventional MRD. The results reveal that the elastic ring and excitation current influence oil-film pressure distribution in ERMRD from different perspectives, leading the oil-film force to present diverse variation characteristics. Compared to MRD, ERMRD exhibits weaker nonlinearity and superior damping performance.

Experimental Investigation of Main Journal Bearing Performance in Marine Applications with Heavy Loads at Slow Speeds Utilizing Different Grade Oils

Heavy loads are known to be among the most critical operational factors affecting the behavior of the lubricating oil film within journal bearing related to marine slow speed diesel engines. In light of the fact, a comprehensive investigation was carried out to examine the performance of journal bearing under heavy loads resulting from increased maximum pressure within the combustion chamber. Further, the research test trial procedures have been extended to cover the different speed ranges of 40 rpm, 85 rpm and 105 rpm, as corresponding to the engine loads (40 %, 85% and 100 % respectively), together with the different oil grades of 20W50, 5W40 and 0W30. Universal Journal Bearing Test Rig (UJBTR) was utilized for conducting the experimental test trials due to its capability to contain versatile variations regarding the key operational factors. Experimental test trials basically based on tracing the changes in the oil film pressure distribution and the maximum oil film pressure values, have given insight into the behavior of heavy-loaded journal bearing of diesel engine related to ships. Based all the experimental test trials under optimal and heavy load conditions, oil grade 5W40 was concluded to provide the most optimal operating conditions for all tested speed ranges.

Experimental Investigation of Main Journal Bearing Performance in Marine Applications with Heavy Loads at Slow Speeds Utilizing Different Grade Oils

Heavy loads are known to be among the most critical operational factors affecting the behavior of the lubricating oil film within journal bearing related to marine slow speed diesel engines. In light of the fact, a comprehensive investigation was carried out to examine the performance of journal bearing under heavy loads resulting from increased maximum pressure within the combustion chamber. Further, the research test trial procedures have been extended to cover the different speed ranges of 40 rpm, 85 rpm and 105 rpm, as corresponding to the engine loads (40 %, 85% and 100 % respectively), together with the different oil grades of 20W50, 5W40 and 0W30. Universal Journal Bearing Test Rig (UJBTR) was utilized for conducting the experimental test trials due to its capability to contain versatile variations regarding the key operational factors. Experimental test trials basically based on tracing the changes in the oil film pressure distribution and the maximum oil film pressure values, have given insight into the behavior of heavy-loaded journal bearing of diesel engine related to ships. Based all the experimental test trials under optimal and heavy load conditions, oil grade 5W40 was concluded to provide the most optimal operating conditions for all tested speed ranges. Keywords: Hydrodynamic Lubrication, Pressure Distribution, heavy loads, Slow Speeds, Oil Grades.

Study on the influence of journal form and position errors on the lubrication performance of four‐recess capillary restrictor hybrid journal bearing

AbstractIn the actual working condition, due to the manufacturing errors, improper installation, load, thermal deformation or other factors can cause the journal surface to produce the form and position errors. The mathematical models are developed that takes into account the form and position errors, the lubrication performance of four‐recess capillary restrictor hybrid journal bearings with different journal tilt angles and cylindricities is studied, and the effect of eccentricity on the oil film lubrication performance is analysed. The results show that the dimensionless oil film pressure and loading capacity increase as the journal tilt angle and eccentricity increase considering journal tilt, and the friction coefficient tends to increase and then decrease. Compared with journal alignment, the oil film thickness distorts, the oil film pressure peak shifts to the edge of bearing, and the horizontal tilt has a greater impact on bearing when the journal is tilted. The oil film pressure distribution has no significant change considering cylindricity errors, while the oil film pressure value increases, the loading capacity increases and the coefficient of friction decreases as the cylindricity and eccentricity increase. The research shows that the presence of a certain cylindricity error contributes to the lubrication performance of four‐recess capillary restrictor hybrid journal bearings.

Analysis of Elastohydrodynamic Lubrication (EHL) Characteristics of Port Plate Pair of a Piston Pump

This article presents a steady-state elastohydrodynamic lubrication model for the contact and sliding interface of an axial piston pump’s port plate pair. The wedge-shaped oil film thickness, pressure, viscosity, and elastic deformation distribution of the port plate pair were investigated by using the finite difference method. The elastohydrodynamic lubrication characteristics for different operating parameters and two materials of the port plate pair were analyzed for comparison. Existing conditions for the EHL were calculated, and variations in leakage and friction coefficients were investigated. The results show that the elastic deformation of the interface greatly influences the oil film’s overall performance, which is related to the material, inlet pressure, velocity, viscosity, and the minimum oil film thickness that determines the EHL. The deformation caused by oil film pressure greatly influences the model leakage and friction coefficient, especially when the deformation is equal to the oil film clearance.

Measurement of Piston Pin-Bore Oil Film Pressure under Engine Operation

Thin-film sensors were used to measure the oil film pressure distribution at the piston pin-bore interface in order to ascertain the stress distribution on the piston pin of a gasoline engine during actual operation. Thin-film sensors have been manufactured by a sputtering method to a total film thickness of about 3–6 μm. The features of thin-film sensors have been utilized to successfully measure the oil film pressure on engine main bearings, connecting rod bearings and piston skirts of both diesel and gasoline automotive engines. However, as engine lubrication conditions have become more severe year by year, it has become necessary to develop thin-film pressure sensors with higher durability. The use of diamond-like carbon (DLC) coating for the protective film of the thin-film sensor has enabled accurate measurement of oil film pressure under engine operating conditions. The AVL EXCITETM Power Unit was used in simulations with the application of elastic fluid lubrication theory. The calculated values were compared with measured data, and a comparison was made of the effect of the model constraint condition.

Meshing Characteristics of Spur Gears Considering Three-Dimensional Fractal Rough Surface under Elastohydrodynamic Lubrication

Taking the effect of actual surface topography under elastohydrodynamic lubrication (EHL) conditions on the contact state of gear pairs into consideration, a combination model with the analytical sliced method and two-dimensional (2D) EHL model is proposed to characterize the three-dimensional (3D) meshing characteristics of spur gears. Firstly, the surface topology of gears is tested by a surface profiler, which reflects that the topography of tooth surface accords with fractal characteristics. Thus, by adopting the Weierstrass–Mandelbrot (W-M) fractal function, the gear surface is characterized. Secondly, the numerical 2D EHL model with fractal roughness is established, and distributions of oil film pressure (OFP) and oil film thickness (OFT) at different meshing positions are obtained. Finally, considering the different topography distributions in the direction of face width, time-varying mesh stiffness (TVMS) is calculated based on the analytical sliced method. Thus, the influence of 3D surface topography can be considered. The Hertz contact stiffness is substituted by the time-varying lubricating oil film stiffness (OFS). The influences of tooth surface topography and lubricant film characteristics on meshing characteristics are investigated. The results show that the 3D rough tooth surface may be well characterized by a fractal function with random phase. Moreover, there is a great difference in the distribution of OFP and OFT between rough and smooth surfaces, which certainly influences the gear meshing characteristics.

Machine learning calculation model for hydrodynamic lubrication characteristics of a miter gate bottom pivot

The bottom pivot is a vital support device in the miter gate but often subject to poor lubrication and wear failures. Calculating the hydrodynamic lubrication characteristics of the bottom pivot is a complex three-dimensional (3D) problem, and most of existing models adopt simplified assumptions to reduce the calculation difficulty. To solve this issue, this work develops a 3D model to calculate the hydrodynamic lubrication characteristics of the miter gate bottom pivot. The finite difference method is used to solve the oil film thickness and pressure distribution based on the spherical coordinates Reynolds equation. The component forces in three directions are calculated from the pressure distribution and compared with the theoretical values to generate the calculation difference. Then, the genetic algorithm (GA) is used to minimize the difference to determine the optimal initial parameters for the 3D model. The analysis results show that the calculation accuracy can be significantly improved by using the optimal initial model parameters. When our initial pressure is 5.64MPa, the results meet the engineering accuracy requirements.

Modeling of lubricated translational joints in rigid-partially flexible multibody systems and its application in two-stroke marine diesel engines

In this paper, a new tribodynamic model for the translational joints with clearance is proposed by coupling the mixed lubrication model and the rigid-flexible multibody system dynamic model. The lubrication behavior is described by the average Reynolds equation and the Greenwood-Tripp asperity contact theory. Under a unified framework of the absolute nodal coordinate formulation (ANCF), motion equations of the rigid-flexible multibody system are established. The assembled equations of tribodynamic model are solved by a stable and effective algorithm. An application example of a two-stroke marine diesel engine is then used to study the tribological and dynamic behaviors of the crosshead-guide translational joint with clearance. The results show that considering the elastic deformation of components will lead to more intense secondary motion and smaller local clearance, resulting in an oil film pressure distribution with great difference from the rigid body modeling.

Study on the hydrodynamic behaviour of journal bearing with herringbone grooved sleeve considering cavitation

This work proposes the development of a hydrodynamic model for journal bearing with herringbone grooved sleeve considering cavitation. The equations of motion for this system are obtained by CFD method and the effects related to hydrodynamics, friction and lubrication. The simulation model used in this paper is based on the multiphase flow model, considering the effects of cavitation on the pressure distribution of oil-film. The proposed model is further verified by the results of published experiment data. Further analysis reveals that the eccentricity ratio, rotational speed, groove depth and number of groove have a great influence on the hydrodynamic behaviour of herringbone grooved journal bearing. Therefore, it is necessary to develop a more realistic simulation model of journal bearing with herringbone grooved sleeve that provide a reference for the journal bearing design.

Experimental Studies on Friction Processes in Sliding Thrust Bearings

A technique for conducting experiments on determining wear features for thrust slide bearings is presented. The friction coefficient depending on the load and on the rotation velocity of the samples, on the changes in the wear weight fraction, and on the surface roughness parameters are determined. The effect of thickness, propagation, and interaction on the oil film formed in a hydrodynamic friction mode on the wear of friction pairs is considered. An instrumental support of the experiment is described, the results and conclusions are presented. It is noted that the local maximum of the friction coefficient is reached at approximately 900 rpm for all the samples and, for each load level, a corresponding minimum of friction coefficient is observed, which increases with increasing rotation velocity. In the course of testing, the minimum values of friction coefficient have been observed in the ranges of 550–650 rpm and 1050–1150 rpm. For the used testing mode, the smallest change in the surface roughness of the samples amounted to Ra = 0.46–045 μm for steel samples and Ra = 0.75–0.89 μm for bronze samples, respectively. These roughness values have been subjected to changes to a lesser extent, being close to the equilibrium roughness in the course of the testing. It should be noted that the greatest weight wear level of the samples occurs under running-in, and, when equilibrium roughness and the minimum friction coefficient have been reached, the sample wear level exhibits a decrease. In addition, upon the experiments, the distribution of the hydrodynamic oil film pressure over the surfaces of the samples was revealed based on the wear scars in the outer circuit, and its high-pressure belt was expanded in the circumferential direction.

Hydrodynamic Bearing Performance Trade-Off Study and Fuzzy-Based Multi-Objective Optimization on an Offset Surface Textured Journal Bearing

The main purpose of this research is to determine the behavior of bearing performance having various operating conditions. Experimental studies are performed to analyze the dynamic characteristics of phosphorous bronze hydrodynamic journal bearing with a surface textured under various loading conditions with multi-grade oil as lubricating at different constant rotational speeds (i.e., 1000 to 4000 rpm). The results indicated that the experimentally obtained oil film pressure and temperature distribution profile were in good agreement with the theoretical results. In this experimental study, Fuzzy-based Taguchi optimization was used to predict the optimal input parameters that result in the optimal temperature combination and stated that the theoretical findings are in good agreement with the oil film pressure and temperature distribution profile obtained experimentally. To maximize the output parameters, this analysis also aims to explain the implementation of the fuzzy logic-based Taguchi analysis.

Numerical analysis and optimization of rectangular texture for gas foil thrust bearing

Accurate surface texture design is of great significance to improve the performances of gas bearings. In this article, the finite difference method and Newton’s method were combined to obtain the oil film pressure distribution, and the effect of rectangular groove on the lubrication performance was analyzed by changing representative texture parameters. The results show that the performances were more affected by the rectangular texture size compared with the distribution and the bottom shape of texture. The increasing of the surface texture number can only enhance the stability of the bearing. The bearing can provide 30% more bearing capacity by choosing larger size, radial arrangement and plane bottom. These results and analysis can provide technical reference for the bearing texture design.

WITHDRAWN: Experimental investigation of hydrodynamic pressure and oil film temperature of surface textured offset halves journal bearing

Abstract The present aim of this paper is to fabricate the surface textured Offset halves journal bearing to study the performance characteristic of the journal bearing. Experimental investigations is carried out to measure the hydrodynamic offset-halve journal bearing performance parameters like oil film pressure and temperature distribution at different loads and constant speed with hydrogl 68 as the lubricating oil. Results reported that the oil film pressure and effective temperature distribution of the lubricating oil are influenced significantly on the radial load and rotational speed. With an increase in the radial load and rotational speed oil film pressure and temperature also increased along the mid-plane of the lobe. The experimental evidence shows that the bearing performance has been improved with surface texture on hydrodynamic journal bearing.

The effects of material and structure of main bearing caps on crankshaft lubrication of diesel engine

The elastic deformation of the crankshaft and engine block has important effects on lubrication performance of main bearings of the diesel engine. But the effect of main bearing caps was rarely analyzed. The purpose of this article is to analyze and compare the tribological performances of main bearings of a 20-V medium-speed diesel engine with different materials and structures of main bearing caps. A coupled multi-elastic body and elasto-hydrodynamic model is established for a 20-V medium-speed diesel engine. The deformations of engine block, crankshaft and bearing caps are simulated with finite element modal condensation method. The bearing lubrication analysis is based on the extended Reynolds equation considering the deformation of contact surface and solved by finite difference method. Two materials and four structures of the main bearing cap are analyzed with the coupled model. The distribution of oil film pressure, thickness and bearing thermal loads are obtained and analyzed. The main bearing cap of iron is better than steel on bearing lubrication performance. With the lower edge stiffness of bearing cap, the maximum oil film pressure of bearing can be reduced by 13%. Meanwhile, the bearing thermal load can be reduced by 53%. The results show that when the bearing cap material is iron and with large trough on both sides of bearing cap, the peak value of edge pressure and the average heat load of main bearing can be reduced effectively under the premise of ensuring stiffness.

A novel assessment study on a dynamic analysis of hydrodynamic journal bearing performance: A Taguchi-fuzzy based approach optimization

The primary objective of this research is to study the bearing performance characteristics having different operating conditions. Experimental investigations are carried out on phosphorous bronze hydrodynamic journal bearing with a surface textured at different loading conditions with multi-grade oil as lubricating at different constant rotational speeds (i.e.,1000–4000 rpm) for studying the dynamic characteristics. Results reported that oil film pressure and temperature distribution profile obtained experimentally are in good agreement with the theoretical results. Fuzzy-based Taguchi optimization has been used in this experimental analysis to predict the optimal input parameters, which result in the optimal combination of temperature and reported that the oil film pressure and temperature distribution profile obtained experimentally, are in good agreement the theoretical results. This analysis also attempts to describe the application of the fuzzy logic-based Taguchi analysis to optimize the performance parameters.