Optimization Of Gasoline Engine Lubrication System

Lubrication system is one of the most significant subsystems in gasoline Internal Combustion Engine, it provides hydrodynamic lubrication for friction pairs of the engine. The performance of lubrication system determines the performance and life of the engine directly. And nowadays the energy crisis becomes more and more serious, people pay more and more attention on improving engine fuel economy. Therefore, the project which this paper worked on is to investigate how to reduce the friction loss of the engine and driven power of the oil pump by optimizing lubrication system, so that the engine fuel economy can be improved due to lubrication system optimization.In this paper, main bearings and conrod bigend bearings, which are two most important oil consumers of lubrication system, were investigated using multi-body dynamics (MBD) and elasto-hydrodynamics (EHD), detailed bearing performance was obtained. Owning to the high computation cost of MBD and EHD, Kriging interpolation method was implemented in this paper, to establish approximation models of engine bearings pioneeringly. Latin Hypercube Sampling (LHS) was used to conduct Design of Experiment (DOE). Bearings parameters screening was first proceeded, 6 parameters were chosen from lots of parameters as design variables to attend the optimization. Multi-objective optimization of the bearings based on approximation models was conducted using Non-dominated Genetic Algorithm (NSGA). Oil Consumption and friction loss of the bearings were reduced. Over a whole speed range, the friction loss of the engine dropped 14.14%, up to 686.27W was saved. And then the pipes diameters of lubrication system were optimized based on optimized bearings, in order to reduce the flow resistance. Under the optimization of both bearings and lubrication pipes, the same oil pressure level was reached as premise, the oil pump size was reduce from 8.80 ml/rev to 7.989 ml/rev, the driven power was dropped 11.02% over the whole speed range, up to 71.46W driven power was saved. Finally, compared with baseline engine, the economy was improved up to 0.7964%.