Design and prototype of dual loop lubricant system to improve engine fuel economy, emissions, and oil drain interval
Author(s)
Plumley, Michael J
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Massachusetts Institute of Technology. Department of Mechanical Engineering.
Advisor
Victor W. Wong.
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Regulations aimed at improving fuel economy and reducing harmful emissions from internal combustion engines place constraints on lubricant formulations necessary for controlling wear and reducing friction. Viscosity reduction results in fuel economy improvement, with benefits of up to three percent reported in some studies. Such reductions are limited by engine durability constraints. Recent limits on oil additives, driven by emissions aftertreatment requirements, impose additional design tradeoffs. The benefit of segregating lubrication systems, in light of modern formulation constraints, is investigated through modeling and experiment. Many findings are applicable to spark and compression ignition engines, with an emphasis placed on diesel engines, given the implementation of the first heavy duty diesel fuel economy regulations. Nearly all engines used today employ a lubrication system with a pump delivering an oil to all engine regions. Axiomatic design concepts are applied to describe the associated design tradeoffs. Two dual loop prototypes were developed, incorporating independent oil systems for the engine valve train and power cylinder, decoupling many lubricant functional requirements. Oil analysis and friction measurement were used to quantify performance. A combination of high viscosity lubricant in the valve train, with low viscosity in the power cylinder, increased fuel economy while maintaining wear protection. Effective protection of subsystems from contamination and oil degradation, particularly the elimination of soot in the valve train, was demonstrated. Detailed friction and oil composition modeling was used to investigate opportunities for further friction and wear reduction. Techniques for investigating oil composition changes along the liner in modern friction models are developed. Differences in lubricant functional requirements along the liner are highlighted. Model results indicate that vaporization along the liner increases lubricant viscosity near piston top dead center, providing a potential wear reduction benefit.
Description
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. Cataloged from PDF version of thesis. Includes bibliographical references (pages 181-193).
Date issued
2015Department
Massachusetts Institute of Technology. Department of Mechanical EngineeringPublisher
Massachusetts Institute of Technology
Keywords
Mechanical Engineering.