| Along with the rapid growth of the production scale and the population of global vehicles, the supply and demand relationship of the petroleum has become increasingly tense with the development of the national economy in China. Facing to National Emission Regulation StageⅣimminently implemented, the strict emission control has also become an increasingly serious problem. However, liquefied petroleum gas is considered as a clean alternative fuel for automobiles that has the most mature technology available and most likely to be promoted for using. Since the country started"'Ninth Five-Year-Plan'Technological Breakthrough Action for clean vehicle"in 1999, LPG-vehicles have been developed comparatively well. The number of LPG-vehicles has already reached to 200,000 in 2004, and the application promotion of LPG-vehicles has experienced a tortuous process. Under the background of China's energy security endangered by the shortage of energy sources, and with more and more rigorous emission regulations, it is an effective measure without fail to focus and to promote application of the mature alternative fuels, which is in order to adjust the energy structure, reduce the emission quantity of greenhouse gas, and realize sustainable development. Based on"National Regulation StageⅣ– the development of Single-LPG-BSH"in the"863"Project of National Ministry of Science and Technology, research on the emission control technology of Single-LPG-Engine was performed, and analysis results are as follows:1. The best conversion window range of BSH's catalytic converter is 0.950≤λ≤1.005. When excess air ratio is in this range, the conversion efficiency of three kinds of emission pollutants were all over 95 percent. Based on BSH's original catalytic converter, we carried out the calibration for its electronic control system on total operation conditions and made the Maps.2. When gasoline was switched to LPG for the engine, the experiment results are as follows:a) In the process of switching to LPG, and on the condition of same engine speed and same torque, the main influencing factor was the coolant temperature. During the fuel switching process, the lower the coolant temperature was, the greater the fluctuation of emission numerical values was. With the increase of coolant temperature, the fluctuation of emission numerical values declined.b) On the same torque and temperature condition, the fluctuation of emission numerical values during low-speed switching process was smaller than the one of high-speed switching process.c) On the same engine speed and same temperature condition, the lower the torque was, the smaller the emission quantity and fluctuation of emission numerical values was during the switching process. Moreover, because calorific values of gasoline and LPG are different and the one of LPG is lower, engine power declined in a fuel-switching instant. On the same engine speed condition, the engine torque declined, which resulted in working-instability of engine. So we should avoid switching fuel as far as possible on high-torque operation condition.d) Since misfire problem was existing in the switching process, we should avoid switching fuel as far as possible when Tcoolant=30℃and Ttq=20N?m, which is in order to avoid premature aging of catalytic converter, and reduce unburned HC emission.e) During fuel switching from gasoline to LPG, it is in a condition that fuel can be switched automatically, namely, N=1600r/min, Tcoolant=50℃and Ttq=50N·m.3. During fuel switching from gasoline to LPG, the test results show that we should avoid switching fuel as far as possible when Tcoolant=30℃and Ttq=20N?m due to misfire problem. And when Tcoolant=30℃, we should also avoid switching fuel because of greater fluctuation of emission numerical values.4. The circulation-test experiment of National Regulation StageⅣwas carried out on the chassis dynamometer. Test results indicate that the Maps made on the test bench and the requirement of fuel switching are comparatively reasonable, which made Single-LPG-BSH pass the circulation-test of National Regulation StageⅣsmoothly.
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