Experiment Of Mechanical Oil Pump Energy Saving Potential In Passenger Car Driving Cycles

Under the development trend of the global economic changing from high energy consumption to low energy consumption,the development of automobile energy-saving technology has become one of the most important directions in the world.At present,a policy named"Energy-saving and New Energy Vehicle Technology Roadmap 2.0"was released,and this policy further clarified the development direction of China’s automobile industry in the next 15 years.In addition,the policy also clearly indicated that the low friction technology is an important method to realize the development strategy of energy-saving vehicles.Meanwhile,the optimization of engine lubrication system to reduce its driving power is one of the important components of low friction technology.And the optimization strategies of engine lubrication system include the utilization of using variable displacement oil pump,low-viscosity lubricating oil,variable circulating lubricating oil technology,engine thermal management technology and so on.The oil pump can realize the functions such as lubrication,cooling,hydraulic drive and pressure control by providing lubricating oil for the engine.At the same time,it has an important impact on the power performance,fuel consumption,reliability and other aspects of the engine.However,most of the current researches are based on oil pump performance and engine fuel consumption in steady-state working conditions,and there are few studies on the matching of oil pumps and engine lubrication systems in driving cycles.It is too difficult to accurately reflect the impact of oil pump design improvement on engine mechanical power loss,because many factors will affect the engine performance test results.Meanwhile,in the steady-state working conditions,there are many difficulties to reflect the energy consumption of the oil pump under the vehicle actual condition.Therefore,based on the above problems,the internal gerotor oil pump of the 1.4L gasoline engine is taken as the research object in this study.And the matching working state of the oil pump and the engine lubrication system in driving cycles is studied deeply.Firstly,the main components of the lubrication system of passenger car gasoline engine are introduced in detail,such as bearing,lubrication pipeline,oil filter,oil collector,etc.And the mathematical models of the lubrication system are established.Secondly,the comprehensive performance test system of the oil pump is built,which can accurately measure the speed,torque,oil supply flow,pressure,lubricating oil density,and other parameters of the oil pump.Then the NEDC driving cycle and the WLTC driving cycle are selected as test conditions.Next,based on the NEDC driving cycle,slope acceleration test conditions and acceleration and deceleration test conditions are designed.At the same time,a calculation method of matching the working state between the oil pump and engine lubrication system is proposed according to the requirements of engine lubrication pressure and flow.Finally,taking these test conditions as the operating conditions of the oil pump,and the oil pump is tested.Thirdly,the matching states of the oil pump and lubricating system in driving cycles are studied.Based on the engine lubrication pressure and flow requirements,safe margins of oil pressure and flow considering engine acceleration were deduced.And at the same time,the pump driving energy-saving potential based on the safe margins is proposed.The results show that there are much more acceleration conditions in WLTC driving cycles than NEDC,which make much severer lubricating conditions.The excessive hydraulic power provided by the oil pump is approximately proportional to engine speed in the speed range over piston spay cooling.The oil pump driving energy can be reduced by 5.8%by a fully variable oil pump displacement in the WLTC driving cycle and lubricating oil temperature of 100℃.Finally,according to the test results of the oil pump under transient acceleration condition,the response characteristics of the oil pump and engine lubrication system in transient acceleration conditions are studied.And the influence of variable displacement lubricating oil pump control strategy on dynamic matching state and driving energy consumption of engine lubrication system is evaluated.The results show that the lag time of the lubrication flow response is longer than that of lubrication pressure in transient acceleration condition.With the increase of angular acceleration and lubricating oil temperature,the response lag time of lubrication flow and pressure decreases linearly.under the transient acceleration condition of lubricating oil temperature of 100℃and engine angular acceleration of 40 rad/s~2,the pressure relief power loss of oil pump is huge,even greater than the output hydraulic power.Compared with the traditional fixed displacement pump,the one stage and two stages variable displacement pressure control strategy can reduce the mechanical driving power by 30.8%and 40.0%respectively.VVT working pressure and piston injection pressure can be selected as variable displacement pressure control points to meet the nonlinear matching requirements of engine lubrication pressure.