【作者】 朱涛；

【导师】 汪洋；

【作者基本信息】 天津大学 ， 动力机械及工程， 2004， 硕士

【摘要】 汽车的排放法规越来越严格，欧3相对于欧2，欧4相对于欧3每一次排放法规的提升NOx排放限值都降低了一半。EGR技术（Exhaust Gas Recirculation）将一部分废气重新引入气缸，降低了氧浓度和燃烧温度，抑制了NOx的生成，现在已经成为改善排放的一个有效手段。国外对EGR技术进行了比较深入的研究，积累了丰富的经验。国内由于排放法规的滞后，净化技术与国外仍然存在着较大的差距。本文通过在一台单缸汽油机上应用EGR技术，在分析废气再循环对汽油机性能和排放影响的基础上，对各种负荷下不同比率的EGR进行了研究，为今后在发动机上采用EGR技术降低NOx排放和确定最佳EGR率提供了依据。作者选取邦德富士达CG125单缸两气门四冲程汽油机作为实验样机，加装了外部排气再循环装置。开发了一套基于Visual Basic的串口通讯控制程序，可以实时获得发动机转速，节气门开度和进气温度的信号并灵活地调节喷油脉宽和点火提前角。开发了电控燃油喷射系统，采用进气口喷射方式。电控燃油喷射系统保持了原机的动力性，经济性大幅改善，HC和CO的排放处于同一水平，但是NOx的排放增加。在此基础上，通过废气引入量的调节，进一步降低NOx的排放。实验结果表明：EGR在不同负荷下都可以有效降低NOx排放，但是废气的引入在低负荷时容易造成失火，全负荷时功率不足，EGR的主要应用领域是中高负荷；适当比率的EGR在保持动力性和经济性的基础上，大幅度降低了NOx排放。研究结果对于改善汽油机的性能和排放具有一定的指导意义。更多还原

【Abstract】 Emission regulation is more and more stern in recent years, the limit of NOx in Euro 4 is half of that in Euro 3.EGR (Exhaust Gas Recirculation) introduces part of exhaust into cylinder, due to reduced oxygen concentration and combustion temperature, generation of NOx is constrained. Study on EGR has been carried on deeply and abundant experience has been accumulated in developed countries. However, there is a great lag between our emission control technology and advanced level. This study focuses on reducing NOx with the respect of no influence in performance and fuel economy.A CG125 single cylinder four–stroke gasoline engine is selected as sample engine with external EGR system. A communication program based on VB is developed with flexible adjusting on injection pulse width and ignition timing, in the meantime, engine’s speed, intake temperature and throttle opening are fed back through transducer. With electrically controlled injection and ignition, effects of EGR on performance and emissions of gasoline engine are studied at different EGR ratios. The experimental results show that NOx emission is reduced effectively by EGR at various loads, however, EGR is restricted at low load by quench and at full load by insufficient power output; at part load, power and fuel economy are retained with optimal EGR ratio while NOx emission is reduced obviously. The study is helpful to the improvement of fuel consumption and emission control of gasoline engine.更多还原