Study On The Influence Of Engine Oil Viscosity On Fuel Consumption Under Two Cyclical Conditions

The rapid growth of car ownership has led to increasing environmental pollution and energy shortages,so China has issued stringent fuel consumption and emission regulations,and the latest emission regulations have replaced NEDC(New European Driving Cycle)cycle conditions with WLTC(Worldwide Light-duty Test Cycle)cycle conditions.In order to meet the requirements of national fuel consumption and emission regulations,a vehicle company is committed to improving the fuel economy of the engine and reducing the fuel consumption of the vehicle.In this paper,the engine of a certain SUV model is studied,through the theoretical and experimental research on the oil viscosity and two cycle conditions,the effects of oil viscosity on engine lubrication and vehicle fuel consumption under two cyclic conditions are studied,which has obtained the oil product that meets the fuel consumption target of the vehicle under the two cycle conditions.The research work and results of this paper are as follows:(1)Introduce the lubrication system of the engine and the main friction pair.The theoretical analysis of the three friction pairs of cylinder liner-piston,crankshaft journal-main bearing and cam-follower is carried out to determine the change of lubrication state and its influencing factors during the working process,which lays a theoretical foundation for subsequent experimental research.(2)Introduced the viscosity grade and quality grade classification standard of the oil,as well as the viscosity characteristics and viscosity-temperature characteristics of the main physical and chemical indicators of the oil.The original oil of the vehicle was used as the comparative oil,and three different test oils with different viscosities were prepared;Through the friction torque bench test and SRV friction and wear test of the engine,the influence of the viscosity of the lubricating oil on the friction coefficient of the main friction pair of the engine was investigated.The results show that reducing the viscosity of the oil can effectively reduce the friction torque of the engine and improve the friction state of the engine,but the improvement effect on the valve trains mostly in the boundary lubrication is not obvious.(3)The basic conditions of WLTC and NEDC are introduced.Then,the appearance characteristics of the two cycle conditions are compared in detail,and the eigenvalues of the two cycles are analyzed to obtain the difference between the two cycles.The specific performance.Finally,through the combination of relevant knowledge and practical experience,the impact of the difference between the two cycles on fuel consumption is qualitatively judged.(4)The experimental method of the fuel consumption test of the whole vehicle and the control of the test accuracy are introduced.The fuel consumption of the four different viscosity oils under the two cycle conditions is calculated by the vehicle fuel consumption test.According to the experimental results,the viscosity of the oil is reduced.It can effectively reduce the fuel consumption of the whole vehicle.To a certain extent,the lower the viscosity of the oil,the better the fuel consumption effect.However,when the viscosity of the oil is too low,the fuel consumption of the whole vehicle will increase.For the cycle conditions,under the same conditions under other conditions,simply changing the NEDC cycle condition to the WLTC cycle condition will result in an increase in fuel consumption of the vehicle,which is between 2% and 3%;In terms of test oil 3#,the fuel consumption is the best.In the NEDC cycle,the fuel consumption is reduced by 1.23%.In the WLTC cycle,the fuel consumption is reduced by 1.35%.Finally,the engine oil product that meets the fuel consumption target of the vehicle is obtained.