Study Of Electronic Fuel Injection Controller For DME Engine

Finding substitute fuels for vehicle have been put on the agenda with energy shortages and the increasing environment pollution. The development of clean fuel to replace petroleum has a real and long-term strategic sense. By analyzing the requirements of clean substitute fuels for vehicle, dimethyl ether (DME) with its clean and efficient combustion and high cetane number and other characteristics become the ideal substitute fuel of diesel. Currently, there are still many problems for DME directly applying to diesel engines. Such as producing air resistance phenomena in fuel supply system, lubrication problems, and easy compression. They have a more influence on injection timing and injection rate. In order to ensure the power, emissions and other performances of engine, engine fuel injection system must be improved.First, the engine was established in AMESim to study single-cylinder engine start condition and idling condition. Secondly, the fuel injection duration control strategy model was established in MATLAB / Simulink. Using software interface, the two models were co-simulated with S-function. According to the engine speed signal from the crankshaft position sensor and cooling water temperature signal, the fuel injection duration was adjusted. Then the basic law between the fuel injection duration and engine speed and the basic law between the fuel injection duration and cooling water temperature were obtained. Third, the signal processing circuits were designed for the selected engine sensors and the drive circuit for the electromagnetic valve of electronically controlled injector. Fourth, based on the simulation data, control procedures were written in CodeWarrior IDE4.6 with C language. Finally, under laboratory conditions, using DEMO9S12XDT512 board as the minimum development system, the designed hardware and the controlled procedures were co-simulated for simulation experiment.Simulation results show that: when the engine starts from the beginning to the idling condition, the cooling water temperature greatly affect the operation, the engine speed may fluctuate greatly and intake pressure is instability. Now, the fuel injection duration should be determined in accordance with cooling water temperature and relatively stable engine speed to ensure a successful engine start. Simulation experiment shows that: the designed reshape and amplify circuits is right. Through the DEMO9S12XDT512 minimum development system, the electronic fuel injection system controller for DME engine was composed by the designed periphery circuits and written program. The controller can collect real-time sensor signals. According to the fuel injection duration control requirements, the controller can output driven signal for electromagnetic valve. The basic function of the control system can be realized. According to the real-time detecting operating parameters, the controller can accurately calculate the amount needed fuel and fuel injection time to realize the optimal control of engine fuel injection and increase engine power, economy and emission performances.