| In the latest decades, since troubles brought by Energy Crisis and Global Warming have become more and more serious, it is extremely urgent to improve the fuel economy of engines on condition that the engines meet the vehicle emission legislations first. As the heat efficiency of gasoline engine is lower and its fuel economy is worse than that of diesel engine, how to decrease the fuel consumption of gasoline engines has become a problem which is necessary to be solved in automotive industry right now. Developing vehicle engines which both have the advantages of gasoline engines and high fuel economy under light load operation conditions like diesels is one of the primary goals of the main automotive companies all over the world. As a new stage of gasoline engine technology, Gasoline Direct Injection (GDI) technology has become a leading research direction for improving the fuel economy of gasoline engines. Generally, GDI engine can improve fuel economy by 20 percents.At present, because the research level of GDI engine is still in the beginning stage in our country, it is meaningful to research and develop GDI engine product independently in China. Engine electronic control system is the core of vehicle electronic control systems, however, there is a common phenomenon called"Technology Vacancy"in Chinese automotive industry which means that most enterprises do not command the key technologies including the electronic control technology instead of choosing a developing mode named"Assembling". In respect that increasing the product value of automotive industry will mainly depend on the research and improvement of automotive electronic products, eliminating the phenomenon of"Technology Vacancy"as soon as possible, carrying out researching on automotive electronic control technology, and develop automotive electronic control products which have independent intellectual property rights are important and pressing tasks for Chinese automotive industry. Nowadays, the electronic control system products of PFI (Port Fuel Injection) engine made by Chinese companies are not reliable enough yet. GDI electronic control technology has many differences compared with that of PFI engine, such as the control task is heavier and the control logic is much more complicated, etc. There is no electronic control system product of GDI engine made by Chinese company in the market so far. So it is necessary to synchronize the development of GDI engine and its electronic control system development. Leading by national enterprises and cooperating with the related universities and institutes is a rather good mode for product research and development.A GDI engine electronic control system has been developed for a 1.8T GDI engine named EA888 based on analysing the work principles of the control system of the engine in detail in this thesis. And then, a series of experiments were carried out for researching the lean combustion characteristics of GDI engine based on the self-developed electronic control system. The main work of this thesis is as follows:(1) A GDI engine test-bed system has been found.(2) The MCU named MC9S12DP512MPVE produced by Freescale was chosen as the main controller of ECU(Electronic Control System) at the beginning, then the signal processing circuit module design, main controller system circuit module design, actuator driving circuit module design, system hardware anti-jamming design were finished. At last, the PCB (print circuit board) of ECU was designed and the real hardware of ECU was made.(3) According to the control software demand analysis, the framework of the control software was determined. According to software framework, hardware design of ECU, based on CodeWarrior IDE (Integrated Development Environment), applying modularization design method, each module of the control software was programmed one by one to realize its function. The control software developed in this thesis can realize the basis control functions coupled with the hardware of ECU.(4) Simple calibration software was developed by applying the software LabVIEW. With applying the calibration software, engine operation parameters can be colleted and the engine control parameters can be tuned online. (5) Finally, based on the self-developed ECU, a series of experiments were carried out to research the lean combustion characteristics of GDI engine on the engine test-bed. Test results show that:①Two stage injection strategy, which means injection occurs in intake stroke firstly and then occurs in compression stroke, was proved to be feasible and reliable to realize lean mixture combustion.②With applying two stage injection strategy, the ratio of second injection pulse width to first injection pulse width affects lean combustion stability obviously. There is an optimum ratio which make engine operate most stably. Under the operation condition of the experiments in this thesis, when the ratio equals to 1/3, engine combustion is robust and there are fewest misfires, engine runs stably.③With applying two stage injection strategy, the second injection timing affects lean combustion stability obviously. The proper second injection timing is in a very narrow range. Under the operation condition of the experiments in this thesis, the proper injection timing is 66°CA BTDC (before top dead center). So the second injection timing must be controlled accurately in a narrow range.④With applying two stage injection strategy, ignition advance angle affects lean combustion stability obviously. The proper ignition timing is also in a narrow range. Under the operation condition of the experiments in this thesis, the proper ignition timing is 26°CA BTDC. So it's necessary to control the ignition timing in a narrow window when the engine runs at stratified charge lean combustion mode.⑤With applying two stage injection strategy, ignition timing must be matched with second injection timing well.⑥Compared with the emissions of GDI engine running at lean combustion mode of idling operation condition with those of equivalent combustion mode, CO emission is lower, HC emission is much higher, NOX is little higher.
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