Non-Newtonian Fluid Application of the Mobility Method in Engine Journal Bearing
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ght © 2020 KSAE/ 11723 pISSN 12299138/ eISSN 19763832
NON-NEWTONIAN FLUID APPLICATION OF THE MOBILITY METHOD IN ENGINE JOURNAL BEARING Minje Park1), Siyoul Jang2) and Kyoungdoug Min1)* Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea 2) Department of Automotive Engineering, Kookmin University, Seoul 02707, Korea
1)
(Received 12 November 2019; Revised 20 December 2019; Accepted 20 December 2019) ABSTRACTThe mobility method is frequently used to analyze the performance of journal bearings subjected to dynamic loads in an internal combustion engine. As the mobility method generally assumes Newtonian fluid, the realistic approach for the multigrade lubricant in engine bearing lubrication is limited. The new mobility approach for non-Newtonian fluid is introduced in this study. A power-law model is applied to describe the behavior of a real non-Newtonian fluid. Additionally, the mobility method for a finite length bearing is developed to estimate the eccentricity ratio for realistic engine bearing dimensions. The new mobility model provides sufficient accuracy and solution details comparable to finite element analysis and experiments while maintaining computational efficiency. Consequently, the realistic approach of the bearing friction analysis is suggested by the eccentricity ratio that can be predicted by the mobility model with finite length bearing and nonNewtonian fluid conditions. KEY WORDS : Non-Newtonian fluid, Mobility method, Eccentricity ratio, Bearing friction, Engine
NOMENCLATURE A C D F Fx Fy h hm K L M MF MS n P Pf Ps Pl r ρ ε θ Φ η
Ý μ
: area, m2 : bearing clearance : bearing diameter : total bearing load : bearing load in x direction : bearing load in y direction : film thickness : minimum film thickness : power-law coefficient : bearing length : mobility value : mobility value (finite length bearing approximation) : mobility value (short bearing approximation) : power-law index : oil film pressure : finite length bearing oil film pressure : short bearing oil film pressure : song bearing oil film pressure : bearing radius : density : eccentricity ratio : bearing angle : attitude angle : apparent viscosity
: shear rate : absolute fluid viscosity
1. INTRODUCTION The automotive industry is facing unprecedented challenges owing to energy and environmental issues. The emission regulation is becoming stricter, the oil price is increasing, and automotive manufacturers should meet the CO2 regulations (Adatepe et al., 2011). The stringent requirements of the fleet average emissions legislation and the compulsory standard on fuel economy have caused considerable effort that can reduce energy loss in an internal combustion engine such as engine cooling, emission of exhaust gas, and mechanical loss (Arghir et al., 2002; Eberth et al., 2004; Fan et al., 2014; Jamrozik, 2015; Kang et al., 2018; Lee et al., 2017a; Lee et al., 2017b; Wang et al., 2015; Yoon and Park, 2016). In the recent decades, improvements in thermal efficiency for vehicles have been introd
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