Experimental study on the oil pump driving energy consumption and lubrication safety in a PFI engine under NEDC and WLTC

We studied the transient driving power of an oil pump for 1.6 L PFI engine in a passenger car under the new European driving cycle (NEDC) and worldwide harmonized light-duty test cycle (WLTC), and analyze the influence of control strategies on the energy-saving potential of the oil pump. To measure the dynamic matching conditions between the oil pump supplements and the engine lubrication requirements, a test system of the engine lubrication performance in passenger cars was built using the hardware-in-the loop (HiL) method. Subsequently, a set of acceleration and deceleration test cycles was designed to represent the harsh lubrication conditions in the standard driving cycles, so as to facilitate analysis of the reasons for driving energy loss of oil pump under transient conditions. Further, three kinds of control strategies of oil pumps used in engine design were analyzed and a comparison was given on their effects on the driving energy consumption and lubrication safety under NEDC and WLTC. The test results indicate that the hydraulic energy losses caused by the pressure relief valve opening and lubricant flow hysteresis were the main reasons for the driving energy increments in the oil pump under transient conditions. In addition, the variable lubrication flow control strategies were effective in reducing the pressure relief valve opening duration and hydraulic energy losses, yet had minimal influence on the hydraulic energy losses caused by lubricant flow hysteresis. Compared with the constant one, 2-stage variable control strategy reduced the overall driving energy by 42.7 % and 46 % in NEDC and WLTC, respectively, while the corresponding hydraulic energy output fulfilled the requirements of engine lubrication. By the 2-stage oil pump, the total fuel consumption of vehicle in WLTC was reduced by 1.93 % and 0.94 % at 25 °C and 100 °C, respectively.