Mean Value Modeling Of A Pre-mixed Spark Ignition Gas Engine

The electronic control is an important technical way to exert the exhaust cleanness and improve the power performance of the spark ignition gas fuel engine, and also is very important to use energy sources efficiently and protect environment. In the model-based and faced application-oriented V-mode development process for the electronic control system,the modeling of the controlled object is a key step.At the early stage of the electronic control unit development,the dynamic simulation model is used in the design of Rapid Control Prototyping(RCP), Software-in-the-loop Simulation(SILS),and Hardware-in-the-loop Simulation (HILS) to evaluate feasibility of a control system hardware scheme and software version.Thereby,it can reduce development cost and shorten development period greatly.In this paper,the controlled object was a small-sized pre-mixed spark ignition gas engine with double valves control structure.In order to develop an electronic control unit,the mean value modeling of the engine was studied by the method combined mechanism analysis with system identification based on the test bench experiment data.The main work as follows:(1) The steady calibration experiment and the dynamic response experiment of the engine intake system were carried out on the vacuum pump flow test-bed,and the flow characteristics of the new control valves were studied.In order to get experiment data for modeling,the steady state operation condition experiment and dynamic response experiment of throttle valve step change were made on the engine bench with compressed natural gas.The engine operation characteristics were simply analyzed on the basis of experiment data.(2) Based on the modular design concept and by means of the Matlab/Simulink software,the sub-models in the engine mean value model were built.These sub-models mainly contained:air valve sub-model,fuel gas valve sub-model,mixer sub-model,throttle valve body sub-model,intake manifold sub-model and crankshaft dynamic sub-model.All the sub-models were verified by the intake system steady calibration experiment data and the engine test bench experiment data.(3) The system simulation model of the whole per-mixed spark ignition gas fuel engine was established with combined sub-models,and the model was validated using the throttle step changed dynamic experiment data.The results show that the model can represent engine air/fuel ratio and speed variety under the transient operating condition.It established foundation for the development of the engine electronic control system as a virtual object.