Abstract:Journal misalignment is common in journal bearings. When severe journal misalignment takes place, it affects nearly all aspects of bearing performance. This paper provided a comprehensive analysis of misaligned journal bearings based on two different mass-conservative models which appropriately took into account film rupture and reformation. The lubrication characteristics and performance parameters including the cavitation zones, pressure distribution, density distribution, oil leakage, load capacity, moment,… Show more
“…A mass-conserving elastohydrodynamic lubrication (EHL) algorithm is implemented in the mixed lubrication model. He et al (2013) analyzed the effect of the cavitation on the lubrication of journal-bearing with cavitation model without surface roughness and inter-asperity cavitation model. Nishikawa (2012) analyzed the oil film thickness in the piston pin boss bearing to reduce piston pin noise of a semi-floating piston.…”
Abstract:Running conditions for piston pin boss bearing have become very severe due to the high combustion pressure and piston temperature increase over the past ten years. The aim of this paper was to analyze the friction and lubrication characteristic of piston pin boss bearings and a connecting rod small end bearing. This paper provided a comprehensive analysis of piston pin based on a multi-body dynamic model which considers the oil film cavitation and structure deformation. Effects of different lubrication models, pin structures, and thermal deformation on the lubrication were discussed. The lubrication characteristics and performance parameters including oil film pressure distribution, asperity contact pressure, the minimum oil film thickness, the maximum oil film pressure, and friction power loss were listed. The results showed that the minimum oil film thickness was very different and the maximum oil film pressure was nearly the same. A parabola profile of pin bore can reduce the wear to some extent, and a flare profile intensified wear in some places and caused the wear to be concentrated on a smaller area. Reducing the inner diameters will reduce the wear of the pin boss. However, in a realistic design of the pin, avoiding high inertial force of the piston system and satisfying the demand for reliability of the pin, increasing the inner diameters and reliability is a 'trade off' problem. A suitable design of the hollow diameter is very important. The results can provide guidance for the design of the pin boss bearing.
“…A mass-conserving elastohydrodynamic lubrication (EHL) algorithm is implemented in the mixed lubrication model. He et al (2013) analyzed the effect of the cavitation on the lubrication of journal-bearing with cavitation model without surface roughness and inter-asperity cavitation model. Nishikawa (2012) analyzed the oil film thickness in the piston pin boss bearing to reduce piston pin noise of a semi-floating piston.…”
Abstract:Running conditions for piston pin boss bearing have become very severe due to the high combustion pressure and piston temperature increase over the past ten years. The aim of this paper was to analyze the friction and lubrication characteristic of piston pin boss bearings and a connecting rod small end bearing. This paper provided a comprehensive analysis of piston pin based on a multi-body dynamic model which considers the oil film cavitation and structure deformation. Effects of different lubrication models, pin structures, and thermal deformation on the lubrication were discussed. The lubrication characteristics and performance parameters including oil film pressure distribution, asperity contact pressure, the minimum oil film thickness, the maximum oil film pressure, and friction power loss were listed. The results showed that the minimum oil film thickness was very different and the maximum oil film pressure was nearly the same. A parabola profile of pin bore can reduce the wear to some extent, and a flare profile intensified wear in some places and caused the wear to be concentrated on a smaller area. Reducing the inner diameters will reduce the wear of the pin boss. However, in a realistic design of the pin, avoiding high inertial force of the piston system and satisfying the demand for reliability of the pin, increasing the inner diameters and reliability is a 'trade off' problem. A suitable design of the hollow diameter is very important. The results can provide guidance for the design of the pin boss bearing.
“…5 g). Their oil film thickness h pi 21 , 27 under different cases are expressed as follows: Figure 3 Schematic of piston texture. Figure 4 Schematic piston eccentricity and inclination.…”
In order to accurately predict the damping characteristics of a hydraulic shock absorber under piston inclination and eccentricity conditions, especially, considering effects of piston surface construction. In present work, taking account of piston slight inclination and eccentricity, a more detailed mathematical model was developed to estimate effects of piston texture on damping characteristics. Based on the mathematical models of reservoir and compression stroke coupled with Reynolds equation, a new damping force model was developed, which analyzed effects of piston structure on damping characteristics. The mathematical models of piston texture, piston slight inclination, piston eccentricity and combinations of three cases are developed to analyzed in detailed effects of piston texture at different work conditions on damping characteristics. The results shown that the friction force of piston increases parabolically with increasing depth ratio, and that of piston increases linearly with increasing area ratio. Piston textures have little effects on damping characteristics at specific structural parameters conditions when piston normal operation, however, textures of slight inclined and eccentric piston have great effects. As a result, piston textures might cause high damping force, destroyed comfort and safety. Therefore, it is necessary that effects of piston surface construction were precisely predicted on damping characteristics under different work conditions. The results might provide a new insight for the design of hydraulic shock absorber and investigation of vehicle system dynamics.
“…While, in numerically solving the Reynolds equation, there are also significant discrepancies in the results obtained under different boundary conditions. Currently, the mass conservation boundary condition based on hydrodynamic cavitation theory proposed by Jakobsson, Floberg and Olsson (also called JFO boundary condition), double Reynolds boundary condition and Reynolds boundary condition are three commonly used boundary conditions in bearing numerical solutions [5,6]. The Reynolds boundary condition and the double Reynolds boundary condition do not satisfy the lubricant mass conservation condition at the boundary where the oil film rupture and reforms.…”
This study aims to reveal the role of the mass conversation cavitation boundary on the tribo-dynamic responses of five kinds of micro-groove water-lubricated bearing under mixed lubrication. By introducing the mass conservation boundary, the tribo-dynamic model of the water-lubricated micro-groove bearing is established and numerically solved by the control volume method. The accuracy of the developed model is verified by comparing the calculated results with the existing experimental and simulation results. The effects of cavitation under Reynolds and mass conservation boundary conditions on different micro-groove bearings were analyzed using the model, and the rotational speed and microgroove depth parameters were analyzed. The simulation results show that , regardless of the shape of the bottom of the microgroove, cavitation can stabilize the journal movement and enhance the dynamic pressure effect of the micro-grooves. The parameter analysis of rotational speed and micro-groove depth proves that rotational speed significantly influences the micro-groove cavitation zone and the dynamic pressure effect. Moreover, the greater the micro-groove depth, the smaller the enhancement effect of cavitation to dynamic pressure. The water-lubricated micro-groove bearing with the bottom shape of the left-triangle has the best lubricating performance during the whole analysis process.
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