Research On Power Output Model Of Gasoline Engine

With the wide application of automotive electronic control systems,the engine as the main power source of traditional and hybrid vehicles,its power output plays an important role in the matching and control of the powertrain.For hybrid vehicles,how to coordinate the engine and motor output during the mode switching process to make the car run smoothly has always been a research hotspot of hybrid vehicles.The key to this problem is not only about how to quickly and accurately coordinate the control through the motor,but also about how to accurately predict and control the power output of the engine.Therefore,it is important to study the engine power output model to achieve accurate prediction of engine power output for vehicle control.Therefore,based on the analysis of the existing gasoline engine modeling method,the average model and the two-zone combustion model are studied by the combination of theory and experiment.The specific works are as follows:(1)Using the engine bench test,the engine steady-state bench test is carried out on two domestic gasoline engines(naturally aspirated and turbocharged),and a more comprehensive steady-state bench test data of the gasoline engine is obtained.The engine data is analyzed to obtain the influence of gas manifold pressure,intake timing,excess air coefficient on engine power and economy,study the influence of ignition timing on torque output,brake specific fuel consumption and combustion characteristic parameters,and the cycle fluctuation of engine indication mean effective pressure is analyzed quantitatively.(2)The three sub-models of the traditional engine mean value model including the intake dynamic model,the fuel dynamic model and the crankshaft dynamics model are theoretically studied.Combining with the bench test data and engine type,the traditional average model is improved and the key parameters of the improved mean value model are identified.(3)Based on thermodynamic theory and computational combustion theory,the theoretical analysis and formula derivation of the two-zone combustion model of gasoline engine are carried out.The modeling process of sub-models including heat transfer model,in-cylinder geometric model and intake and exhaust flow calculation model are analyzed.Aiming at the long simulation time of the two-zone combustion model,it is proposed to divide the calculation process into two major types of large-step process and small-step process,and take the off-line calculation method for the thermodynamic properties of the working fluid.The running time of the model is reduced on the premise of ensuring the simulation accuracy.On the basis of using the Runge-Kutta method to obtain the cylinder pressure,the calculation method of the engine output torque and the instantaneous cranking torque in the working cycle is further derived.(4)According to the measured steady-state bench test data,the accuracy of established average model is checked.The calibration mean value model is used to simulate the steady-state speed characteristics,torque characteristics and full throttle dynamic acceleration process.The steady-state cylinder pressure of the two-zone combustion model is checked,the indicated torque and cyclic crank torque are calculated,and steady-state speed characteristics,torque characteristics are simulated.The simulation results are compared with experimental data and the causes of model error are analyzed.Finally,the accuracy of mean value model and the two-zone combustion model are compared by accuracy,real-time and applicability of the model simulation results.