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Purpose This paper aims to study different morphology Cu6Sn5 effect on Babbitt alloy tribological properties. Design/methodology/approach Different morphology Cu6Sn5 of Babbitt was conducted by different cooling modes. Bare Babbitt was marked by Babbitt-0, Babbitt modified by first cooling mode (marked by Babbitt-1) and Babbitt modified by second cooling mode (marked by Babbitt-2). The microstructure and microhardness of specimens were tested. Then, tribological properties of Babbitt-0, Babbitt-1 and Babbitt-2 were performed by reciprocating mode under lubricated condition. Findings The results showed that shape Cu6Sn5 of Babbitt was changed from mixed needle and star-like shape to short rod-like or granular shape. The microhardness of Babbitt-1 was highest than that of Babbitt-0 and Babbitt-2. Compared with Babbitt-0 and Babbitt-2, tribological properties of Babbitt-1 were better under lubricated condition due to short rod-like and sparse distribution of Cu6Sn5. Moreover, the simulation result of strain and stress of Babbitt-1 was lowest than that of Babbitt-0 and Babbitt-2. Originality/value Different morphology (shape and distributed) of Cu6Sn5 was obtained by different cooling modes. Modulated different forms of Cu6Sn5 around SnSb was beneficial to improve Babbitt alloy tribological properties.

Purpose Currently, lubrication analysis of piston ring is generally done under engine rated operating condition. However, the engine (such as the vehicle engine) does not always operate in rated operating condition, and its operating condition changes frequently in actual use. In addition, the lubrication status of piston ring is generally assumed as the flooded lubrication or a certain form of poor lubrication in most of the lubrication analysis. Design/methodology/approach In this paper, based on the equations about the flow rate of lubricating oil and the variation of control volume, the flow model of lubricating oil in the piston ring-cylinder liner conjunction is established. The lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done, in which the lubricating oil at the inlet of piston ring is considered as the lubricating oil attached on the relevant location of cylinder wall after the piston ring moves over at the previous stroke. Findings There is remarkable difference for the lubrication characteristics of the piston ring under different engine operating conditions. The worst lubrication status of piston ring may not take place under engine rated operating condition. Originality/value In this paper, based on the measured engine cylinder pressure, the lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done in which the lubricating oil supply condition at the inlet of piston ring is considered. The results of this paper are helpful for the design and research of engine piston ring-cylinder liner conjunction.

Currently used turbulent lubrication model that considers the effects of surface roughness can only handle the isotropic rough surfaces and cannot handle the rough surfaces with directional properties. In this paper, based on the stochastic method and the Ng-Pan turbulent model, the stochastic turbulent lubrication models of one-dimensional longitudinal rough surface, one-dimensional transverse rough surface and isotropic rough surface are derived. The turbulent lubrication performance of a journal bearing with isotropic rough surface is calculated by the stochastic turbulent lubrication model. The results are in good agreement with the corresponding experimental data. Moreover, the proposed stochastic turbulent lubrication models are also suitable for parts of friction pairs such as journal bearing and thrust bearing.

In the journal-bearing system, the journal inevitably moves along the bearing axis, and the axial movement of journal may affect the performance of misaligned journal bearing. In this article, a numerical model for the thermohydrodynamic lubrication of bearing considering the axial movement of journal is established, and based on which a comprehensive analysis on the performance of misaligned journal bearing is conducted by solving the generalized Reynolds equation, heat conduction equation and energy equation. The results show that axial movement of misaligned journal has more obvious influence on the bearing lubrication characteristics at the lower speed, larger inclination angle and eccentricity. The impact of axial movement on the bearing lubrication performance is greatly affected by the thermal effect and surface roughness.

In actual operation of an engine, the crankshaft will move along the axis direction of engine main bearings under the combined influence of various influencing factors. Considering the axial movement and crankshaft deformation, a new lubrication model of engine main bearings with rough surface was built based on the average Reynolds equation. The influence of axial movement of deformed crankshaft on performance of main bearing with rough surface was studied. In this study, the axial movement law of deformed crankshaft is measured through experiment, and the finite element method was applied to solve the tilting of crankshaft in the bearing bore resulted from the crankshaft deformation. The results show that the axial movement of deformed crankshaft has a significant impact on performance of main bearing with rough surface. No matter whether or not the surface roughness is considered, the journal center trajectories of main bearings are unclosed three-dimensional space curve due to the axial movement of deformed crankshaft. The influence level of the axial movement of deformed crankshaft on lubrication characteristics of main bearings is directly related to the surface roughness. The influence trend and level of the surface roughness on lubrication characteristics of main bearings are obviously changed when considering the axial movement of crankshaft.

Based on the coordinate transformation method, the generalized turbulent lubrication equation considering the axial motion of the journal is derived. The finite-difference method is used to solve the generalized turbulent lubrication equation. The variations of turbulent lubrication performance with axial displacement for different axial movement velocity of the journal, journal misalignment angle, and initial mid-plane eccentricity ratio are obtained. The results show that when the axial movement velocity of the journal increases, the mid-plane eccentricity ratio of the bearing and the minimum film thickness remain unchanged, the average Reynolds number, maximum film pressure, load capacity, frictional power, and side leakage increases. As the axial displacement of the journal increases, the greater the misalignment angle of the journal, the greater the degree of misalignment, maximum film pressure, load capacity, and misalignment moment of the bearing. The greater the initial mid-plane eccentricity ratio, the greater the degree of journal misalignment, maximum film pressure, load capacity, frictional power, and misalignment moment.

In current lubrication analysis of piston skirt, the flooded status is generally considered in the piston skirt–cylinder liner frictional pair in all strokes of an engine operating cycle. However, the quantity of lubricating oil at the entrance of piston skirt cannot always ensure the sufficient lubrication status of piston skirt–cylinder liner frictional pair when the piston moves from the bottom dead center to the top dead center in actual engine. In this article, based on the model of piston secondary motion, fluid lubrication, and lubricating oil flow, the lubrication performance of piston skirt–cylinder liner frictional pair is analyzed, in which the quantity of lubricating oil detained on the surface of cylinder liner after the piston skirt moves from the top dead center to the bottom dead center and is considered as the quantity of lubricating oil at entrance of piston skirt when the piston moves from the bottom dead center to the top dead center. The results show that compared with current analysis, in which the sufficient lubrication of piston skirt–cylinder liner frictional pair is assumed in all strokes of engine, there are remarkable changes for the lubrication performance of piston skirt–cylinder liner frictional pair and the piston secondary motion when the lubrication status of the frictional pair in the upstroke of piston is determined by considering actual lubricating oil transport in the lubrication analysis of piston skirt.

Unbalanced inertia force and moment of crankshaft generated by cylinder pressure have a significant effect on the vibration characteristics of diesel engine, but the study on the lubrication characteristics of crankshaft by balance rate needs to be studied. Based on Greenwood-Tripp asperity contact theory and average Reynolds equation, an elastohydrodynamic (EHD) lubrication model of the main bearing for a V-12 diesel engine is developed, and the influence of different balance rates on lubrication characteristics is analyzed. On this basis, a factorial experiment of ten influencing factors including the balance rate is designed, and the factors that significantly affected the lubrication characteristics of the main bearing are screened out by factor effect diagram, statistical analysis and residual probability diagram. The results show that the crankshaft with different balance rate has a great influence on the lubrication performance. With the increase of balance rate, the minimum oil film thickness first increases and then decreases, and the maximum oil film pressure first decreases and then increases. The balance rate, bearing width, bearing clearance, bush repair and oil viscosity have significant effects on the performance of main bearing, among which the balance rate of crankshaft has the greatest effect on the minimum oil film thickness, the maximum rough contact pressure and the average friction power loss.

The generalized turbulent lubrication equation for isotropic rough surface bearings is presented by integrating the Hashimoto turbulent lubrication model and the Patir-Cheng laminar flow lubrication model. The finite difference method is used to solve the generalized turbulent lubrication equation and energy equation. And the variations for turbulent lubrication performance of journal bearing with the nominal eccentricity ratio and nominal average Reynolds number are obtained under the influence of surface roughness and journal misalignment. As the dimensionless surface roughness height of the bearing and the journal increases or the degree of misalignment increases, the dimensionless maximum film pressure, dimensionless load capacity and dimensionless misalignment moment of the bearing increases. The research of journal misalignment, thermal effect, and surface roughness is needed.

The status of the lubricating oil transport in the piston skirt-cylinder liner has important influence on the lubrication of piston assembly frictional pair, the consumption of lubricating oil, the emission, and the performance degradation of lubrication oil. In this paper, based on the model of piston secondary motion, fluid lubrication and lubricating oil flow, the status of the lubricating oil transport between the piston skirt and the cylinder liner on different engine operating condition is calculated, and the quantity of lubricating oil retained on the surface of cylinder liner is mainly analyzed when the piston skirt moves from the top dead center to the bottom dead center. The results show that the variation of the quantity of retained lubricating oil is almost same in the corresponding stroke on different engine operating condition; the quantity of retained lubricating oil is dissimilar at different moment and is equal in principle at the piston top and bottom dead center. The quantity of lubricating oil retention is dissimilar at different moment in the intake stroke or expansion stroke, but the quantity of lubricating oil retention is equal in principle at the top and bottom dead center on different engine operating condition. When the engine is on the same load condition, as the engine rotational speed increasing, the quantity of retained lubricating oil is decreased in the whole intake stroke and the middle and later parts of expansion stroke, but the quantity of retained lubricating oil is increased in the front part of expansion stroke. When the engine is on the same rotational speed condition, the quantity of retained lubricating oil increases with the increasing engine load in the front part of expansion stroke, it does not vary with the engine load in principle in the middle and later part of expansion stroke, the variation that the quantity of retained lubricating oil varies with the engine load is dissimilar in the intake stroke on different engine rotational speed condition.

Generally, the movement of journal along the direction of bearing axis under the combined action of various factors is neglected in the lubrication study of bearing, which is quite different from the actual working condition of bearing in the shaft-bearing system. In this paper, with a comprehensive consideration of the axial movement of journal, the surface topography of journal and bearing and the misalignment of journal, a new model about the hydrodynamic lubrication of misaligned journal bearing is established based on the average Reynolds equation. Considering the effect of the axial movement of misaligned journal, the lubrication characteristics parameters of rough journal bearing is presented and mainly discussed. The results show that the axial movement of misaligned journal has a distinct effect on the bearing lubrication characteristics. The influence of the axial movement of misaligned journal on the bearing lubrication characteristics is slightly reduced when considering the surface roughness.