On The Friction Characteristics Of Low-Viscosity And Low-Friction Lubricating Oil In Automobile Engine

As one of the most cost effective energy saving methods,engine lubricating oil is closely related to the performance of the lubrication system,having important influence on the friction characteristics of the engine and the vehicle,to achieve the goal of carbon peak and carbon neutrality and to satisfy the fleet fuel consumption regulation.Low-viscosity and low-friction are two main trends of the development of engine lubricating oil formulation.Although there has been a lot of researches and applications on engine key friction pairs and friction m performance,there were still limited theoretical studies on the research of low-viscosity and low-friction lubricating oil on the friction reduction mechanism in internal combustion engine.Car manufactures prefer vehicle fuel economy researches according to test cycles defined by fuel consumption specification,but neither the precision of the tests nor the cost control is satisfying.Apart from the theoretical analysis and experiment of the anti-friction mechanism of low-viscosity and low-friction engine lubricating oil,this dissertation also introduced the Stribeck curve to study the anti-friction mechanism of low-viscosity lubricants in engine system.Significant fuel economy effect can be achieved with the help of suitable low-viscosity grade and effective friction modifier additives.A systematic study of vehicle WLTC fuel consumption test was conducted,reducing the variation of test result from 0.12 to 0.02.Besides,the engine friction torque test method was developed,so as to reduce the research period and investment.This dissertation consisted of the following topics:(1)The influence of low-viscosity technology on the minimum oil film thickness and friction power consumption of key friction pairs was studied by classic lubrication model.Kinetic analysis and lubrication model were carried out for the piston-cylinder liner system and crankshaft main bearing,with a dedicated SAE 30 turbocharged engine compatible oil.(2)The influence law of low-friction lubricating oil on engine friction characteristics was obtained.The piston ring-liner friction test,MTM test and engine mechanical friction loss test were conducted to study the low-viscosity lubricating oil in the mixed lubrication and fluid lubrication on the friction coefficient of friction pair and the engine.(3)The influence law of low-friction lubricating oil on engine friction characteristics was obtained.The SRV test,piston ring-liner friction test and engine mechanical friction loss test were conducted to study the low-friction lubricating oil in the boundary lubrication and mixed lubrication on the friction coefficient of friction pair and the engine.(4)The effects of low-viscosity technology,low-friction technology and their combination on the tribological power consumption of the three lubrication types(boundary lubrication,mixed lubrication and fluid lubrication)were discussed in combination with Stribeck curve model analysis and friction characteristics test results in engine system as a whole.(5)The precision of vehicle fuel economy test on chassis dyno was improved and engine friction torque test method based on WLTC cycle was developed.The engineering application of low-viscosity and low-friction lubricant was verified.In order to improve the problem of poor testing accuracy of vehicle fuel consumption,various influencing factors were systematically studied and strict precision control strategy was introduced to accurately evaluate the fuel economy improvement of oil samples.Then an engine friction torque test method based on WLTC cycle was developed to support the vehicle fuel consumption test.Finally,GED test and GETC test were conducted on low-viscosity and low-friction lubricating oil according to the parts development process of vehicle enterprises to verify its engineering application and estimate its application value.