A Study For Modeling And Simulation On Pre-mixed Spark Ignition Gas Engine

It is very significant to develop the electronic control system for gas engine. As it can use energy sources efficiently, and improve the structure of energy, then protect the global environment. Developing the electronic control simulation system for pre-mixed spark ignition gas engine can provide a worktable for the studies of control strategy based on model and the development of the electronic control system. This paper studied the models of pre-mixed spark ignition gas engine particularly, which adopted the method of mechanism analysis and system identification.Firstly, for the collection of engine characteristic parameters correctly, the static and dynamic calibration experiment of the hot type of mass air flow sensors was brought to success on the calibration experiment stage which was designed by us. The static assembled polynomial model based on subsection fitting of the hot film and wire type of MAF sensors and dynamic nonlinear model of the hot film type of MAF sensor based on assembled Hammerstein models and linear neural network model were identified correctly.Secondly, the flow characteristic of the intake system of pre-mixed spark ignition gas engine was studied on the vacuum pump. The discharge coefficient models of the air valve, the gas valve and the subsystem of the mixer and throttle were modeled. Their working flow characteristics were analyzed. And the dynamic model of the intake system was identified.Thirdly, a mass of engine experiments were done on the engine experiment bench, which were under the steady condition using compressed natural gas and LPG and the dynamic condition using LPG. The manifold pressure model, crank dynamics model, volumetric efficiency model, manifold pressure and speed and exhaust emission predicted model, indicated thermal efficiency model and speed governor system model were identified respectively. The exhaust emission characteristic of the engine using compressed natural gas was analyzed by simulating based on the exhaust emission predicting model.Lastly, the whole engine system simulation model based on MATLAB— SIMULINK were established through assembling all the sub models. The characteristics of part steady conditions using LPG were simulated on the model, and compared with the experiment results. So were the dynamic characteristics as stepping the throttle and load which were actuating signal and disturbance signal. The study result showed that the system simulation model can simulate the steady and dynamic characteristics of pre-mixed spark ignition gas engine. And the simulation model had certain generalness, which were the same with CNG and LPG. Only some parameters such as theoretical A/F ratio and modified coefficients of sub models needed to modify little, when simulating the characteristics of engine using different gas.A series of simulation experiments could be carried out by using the systemic simulation model. So the varied law of each parameter of the engine could be studied further, and the control parameters could be optimized. This is the basis of studying the appropriate control strategy, implementing the regulation of the real time simulation control system with ECU, and developing the real intelligent electronic control system.