| Energy crisis, increasingly tough emission rules and effects of greenhouse gases are the three focuses of major contradictions on today's environmental aspects of world development. In order to relieve the conflicts and promote the harmonious development of human society, countries had drafted strategies to develope new automotive technologies and seek alternative fuels As a new type of vehicles alternative fuel,natural gas was mainly popularized because of rich reserves, energy-saving and low emission, inexpensive, using flexibly, money-saving and safety; With the strong support of government policies, popularizing of natural gas vehicles and rapid replacement of electronic control technology and automotive technology, the failure diagnostics of natural gas engine become more difficult. This phenomenon was more prominent in developing countries such as China, so it was necessary and urgent to study its failure mechanism and diagnosis method.With the funding and support of the Shaanxi transportation technology projects, in this paper, Mitsubishi 4G15S electronically controlled GASOLINE/CNG flexible-fuel engine was used as the main study object, the classification of natural gas engine, the structural composition, operation principle and the signal features of relevant sensors and actuators components of gas system were introduced systematically, the gas system's common faults that may occur was analyzed. With the testing bench and emission analysis for foundation, with Advantech PCI-1712 acquisition card, front-end signal processing circuits, signal loss circuits as well as the cutting off circuits of the original machines/analog signals for hardware, with LabVIEW software as technical support, failure simulation system of electronically controlled GASOLINE/CNG flexible-fuel engine gas system had been designed, the impact of associated sensors (such as the inlet air pressure sensor, gas injection pressure sensors, oxygen sensors, etc.) and actuators (such as the pressure reducer components, fuel switching devices, etc.) failures on power output, economy and the various emission targets under the gas state were analyzed, and the desired results had been achieved. The failure simulation system was designed to reproduce real-time fault provided a platform for the study of the natural gas engine failure mechanism, and was of better versatility. On the basis of engine failure simulation test, ANN and MATLAB software were used, compressed natural gas (CNG) engine diagnosis model on failure was established and it had been verified. It was of wide range of adaptability.Due to the promotion of natural gas vehicle and the development of EFI technology, the failure diagnostics of natural gas engine was an entirely new topic itself. Overall, the innovative points of this paper are mainly embodied in:(1)The structure, composition and function of the electronically controlled GASOLINE/CNG flexible-fuel engine gas system are described.It is the first time to complete the related failure simulation test of the gas system,analyze the impact of the associated sensor and actuator failures of gas system on the performances of the engine and summarize its laws.(2)With the combination of flexible-fuel engine test technology, virtual technology and control theory, the failure simulation system of electronically controlled GASOLINE/CNG flexible-fuel engine has been designed, and a new kind of diagnostics for natural gas engine was provided.(3)ANN (BP and FNN) is introduced to the modeling and simulation of diagnostics for the CNG engine and the ideas of CNG engine diagnostics was broadened which was used for reference.(4)Expert system ideas and artificial intelligence are added in CNG engine diagnosis on failure software. The promotion of a certain significance is contianed in the development diagnosis on failure software. |
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