One Dimensional Flow Analysis And Optimization Of Variable Displacement Oil Pump

The variable displacement oil pump(VDOP)is a technology developed on fixed displacement pump, and its displacement can be changed with engine working condition which saves engery 2% to 3%. Taking the gear type electricmagnetic switching variable displacement oil pump as the research object, the math and one-dimensional model were established and validated by bench test. After this, the characteristic of VDOP was analyzed and optimized.Firstly, on the basis of working principle and math model, one-dimensional model was established. Using two methods to simulate the changes of gear pump inner volumes and flow surfaces, one is CAD measuring, and the other is creating the flow rate formula.Variable displacement pump(VDOP)model can be obtained by connecting gear pump and constant pressure valve whose accuracy was validated by bench test.Secondly, the pump fluid and motion characteristic were optimized and analyzed. It includes analyzing the change of filtered pressure and flow rate, exploring constant pressure valve characteristic and the influence of its structure on pump, calculating the volumetric efficiency with the meshing width, analyzing the driving torque characteristic,the influence of filter and engine load on pump. Results shows, before 1462r/min, the pump displacement is fixed. After this, system turns into variable displacement stage and filtered pressure was controlled as active balance by constant pressure valve and the pressure value determined by the valve structure.Finally, the optimization object was determined by characteristic analyzing. Within the pressure and flow rate design range, taking the pressure wave in steady state and pressure impact in switching process minimized as the optimization objective, the structure parameterss of gear and valve were optimized with NLPQL(Non-Linear Programming byQuadratic Lagrangian)algorithm after choosing the variables and determined the bound range. After optimization, the pressure and flow rate are all in design range, the low steady pressure wave decreases by 25.88%,and the high 25.91%, the pressure impact weaken obviously.This thesis is to analyze and optimize the pump characteristic by modeling and test.The model can be regarded as a technology support on pump concept design and improvement. In addition, the one-dimensional modeling method of variable displacement pump may be a reference for modeling other types of variable displacement pump.