Analysis Of Thermo Hydrodynamic Performance Of Dynamically Loaded Bearings In Consideration Of Non-netonian, Deformation And Surface Topograhpy

Crankshaft bearings are one of the most critical deputy frictions of internalcombustion engine (ICE), its lubricating performance relates directly to thereliability and durability of the ICE. In recent years, with the rapid developmentof industry, legal, regulatory and environmental are made to a higher demandfor design of the ICE, which makes the operating conditions of the ICE,particularly the crankshaft bearings become very harsh. In this case, crankshaftbearings lubrication and even damage will be closely related to various factorssuch as temperature, deformations, non-Newtonian of lubricants and surfacemorphology. Crankshaft bearing is typical dynamically loaded bearing. In viewof this, this paper conducts a study on the lubrication problems of dynamicallyloaded bearings taking multiple factors into account. The research contents andresults are as follows:Based on hydrodynamic lubrication theory, the thermodynamic simulationmodel of dynamically loaded bearings is developed. This model involves thesimultaneous solution of generalized Reynolds equation with mass conservationboundary, three-dimensional energy equation and solid heat conductionequation. The discrete and solving methods of the model equations are given, and the model validation is also provided. Taking a typical main bearing asexample, the impact of thermal effects on lubrication performance of thedynamically loaded bearing is examined. The results showed that thermaleffects make the minimum film thickness decrease, the maximum film pressureincrease, friction instantaneous power loss significantly decrease, leakage flowincrease.The theoretical study is conducted for shear thinning problems ofcommonly used lubricants (multi-grade oil). Combined the constitutive equationproposed by Gecim, the thermohydrodynamic lubrication model of dynamicallyloaded bearing is presented, which includes non-Newtonian behavior oflubricants. In-depth analysis of the effects of shear thinning characteristics ondynamically loaded bearing lubricant thermal hydrodynamic lubricationproperties. It can be found that shear thinning characteristic of lubricants makesviscosity reduced, which results in the minimum film thickness, the averagepower loss decrease, the maximum oil film pressure and the average flow rateincrease. Meanwhile, the reduced viscosity also leads to viscous dissipationdecrease. Correspondingly, the maximum operating temperature of the bearingdecreases.Considering the effects of deformations and surface topography, thethermoelastohydrodynamic mixed lubrication model of dynamically loadedbearings is established. In the light of the stability of the calculation, give thevarious deformations (elastic and thermal deformation of the bushing, the journal thermal expansion) and the coupling solving method with thegeneralized Reynolds Equation. Taking a gasoline engine main bearing asexample, the effects of various deformation and surface morphology onlubrication properties of dynamically loaded bearing is analyzed systematically,and some valuable conclusions are obtained.From the perspective of engineering applications, using the analysis modelof dynamically loaded bearing in consideration of multi-factors effects, andcombined with experimental design method, the impact parameters onlubrication performance of the main bearing is analyzed. From the bearing(structure, design, materials, processing methods, etc.), lubricant and operatingconditions, thirteen parameters affecting on the bearing lubrication performanceare selected, and thirteen factors and three levels of orthogonal experimentaltable is design. By range analysis method, the primary and secondary order ofthe effect of parameters is studied. On the basis, the optimum design solutionsfor reducing friction loss are developed, and which are verified throughexperimental.