Abstract:A theoretical analysis is presented of the mixed lubrication of a piston ring pack. The analysis comprises Patir and Cheng's average flow model and Greenwood and Tripp's asperity interaction model, and is developed to consider the shear thinning effect of a non‐Newtonian fluid, multigrade lubricant. The friction characteristics of the piston ring pack for both monograde and multigrade lubricants are investigated. It is found that a decrease in the lubricant viscosity is effective in reducing the friction loss,… Show more
“…Later on, these results were used by the same authors to make predictions about the friction in the mixed lubrication regime. Hamatake et al 6,7 showed that the piston ring friction was influenced by a kind of lubricant oil when contact occurred in the mixed lubrication regime. In addition to this element, the effects on the friction forces of the lubrication conditions (starved and pure hydrodynamic) were analytically examined of a piston ring pack.…”
A 2D axisymmetric hydrodynamic model was developed considering fluid structure interaction analysis in order to solve the Navier–Stokes equations. The effect of lubricants viscosities in terms of both monograde and multigrade oils, on the produced piston ring friction force are compared, using smooth and textured piston rings. The novelty of the current paper is the solution of the Navier–Stokes equations with the use of power law lubricants, which act in non-Newtonian shear for the piston ring friction problem. The lubricant viscosity variation in relation to the temperature has been taken into account. Simulation shows a good prediction at lower loads and higher piston speeds. The hydrodynamic pressure, the oil film thickness and the friction force on smooth and textured flat piston ring are predicted and presented.
“…Later on, these results were used by the same authors to make predictions about the friction in the mixed lubrication regime. Hamatake et al 6,7 showed that the piston ring friction was influenced by a kind of lubricant oil when contact occurred in the mixed lubrication regime. In addition to this element, the effects on the friction forces of the lubrication conditions (starved and pure hydrodynamic) were analytically examined of a piston ring pack.…”
A 2D axisymmetric hydrodynamic model was developed considering fluid structure interaction analysis in order to solve the Navier–Stokes equations. The effect of lubricants viscosities in terms of both monograde and multigrade oils, on the produced piston ring friction force are compared, using smooth and textured piston rings. The novelty of the current paper is the solution of the Navier–Stokes equations with the use of power law lubricants, which act in non-Newtonian shear for the piston ring friction problem. The lubricant viscosity variation in relation to the temperature has been taken into account. Simulation shows a good prediction at lower loads and higher piston speeds. The hydrodynamic pressure, the oil film thickness and the friction force on smooth and textured flat piston ring are predicted and presented.
“…However, another more accurate fit over wider temperature rage 33,34 is Vogel equation 35 (equation (4)). The Vogel equation is widely used in PRL lubrication models 28,29,36–38 and is expressed as follows Figure 3.Temperature-dependent viscosity variation of two different SAE-indexed multigrade oils.…”
Section: Mathematical Modelmentioning
confidence: 99%
“…Artificial surface modification such as honing is not considered in the present study; thus, as supposed by previous studies, 29,36,44 δ is assumed to follow the Gaussian distribution in the current work. Therefore, h T is expressed as follow 36 where σ=σ12+σ22.…”
Emerging clearances caused by out-of-round cylinder bores alter the tribological performance of piston compression rings. This change in performance intensifies during engine warm-up. To analyze the development of tribo-characteristics, a 2D mixed lubrication model is considered in the simulation of piston ring conjunction with a distorted bore during the entire warm-up period of a four-stroke spark ignition engine. Piston ring axial dynamics and conformability analyses are incorporated in the simulation. Oil film thickness, frictional loss, asperity interaction, and lubricant flow to the combustion chamber are investigated. The effect of the magnitude of bore distortion on ring conformability, oil transport, and energy loss per warm-up is also evaluated. Variations in oil transport and energy loss per warm-up per unit change in bore distortion are subsequently analyzed. Results show that despite the high film thickness, frictional losses remain substantially high during the initial warm-up phase. An uneven lubricating film resulting from bore non-circularity reduces this energy loss, but drastically increases the already augmented oil transport during the cold engine start-up. The temperature-dependent variation in performance is sensitive to bore distortions.
“…In recent years, many results have been achieved. For example, Harigaya [1], Hamatake [2], Froelund, K [3], Ejakov [4], Hamatake, Toshiro [5], Toshiro and Y [6] Harigaya have studied the effects of lubricant viscosity on the film thickness and friction force of piston ring-cylinder liner components. TIAN [7][8] and the research impact of the dynamics of piston and piston ring set on the effect of friction and lubrication.…”
In the lubrication analysis of piston ring-cylinder liner components for a diesel engine, it is usually assumed that the oil is Newton fluid. But in practice, the lubricant is not always in line with the law of viscosity, that is to say that the lubricant can characterize some non-Newtonian effect. In this paper, a power law fluid was taken as an example to establish the non-Newtonian liquid lubrication model of piston ring-cylinder liner components for a diesel engine. The model was solved by a MATLAB program simultaneously with the load equation. It was found by the results that when considering the non-Newtonian effect of lubricating oil, oil film pressure was different when the power law coefficient was different, but the distribution and the change trend of the oil film pressure was similar; and the highest oil film pressure appeared at a similar position .However, the value of the oil film pressure increased with the increase of the power law coefficient, that is, the greater the power law coefficient, the greater was the oil film bearing capacity. The power law coefficient had little effect on the maximum oil film pressure.
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