在1台汽油缸内直喷(GDI)发动机上添加进气道乙醇喷射(EPI)系统,将其改装为燃料混合比例实时可调的双燃料双喷射系统发动机.将改进的发动机应用于典型城市工况,重点对燃油经济性、微粒数量和质量排放特性进行研究,同时分析燃烧特性和气态常规排放物.研究结果表明:随着进气道乙醇喷射比(质量分数)Rethanol增加,当量比油耗bESFC降低,摩尔乘数效应增强,更多燃烧产物在膨胀行程做功,从而提高有效热效率.碳氢化合物(HC)排放随着Rethanol增加而逐渐降低,不依赖于发动机负荷的变化.各负荷下微粒数量和质量排放均随Rethanol增加而降低.乙醇良好的蒸发特性和较高的含氧量能够抑制碳烟前驱物的生成,增强微粒氧化特性.乙醇与汽油混合形成的共沸点混合物能够增强汽油的挥发性,改善混合气质量,进而降低微粒排放.%An ethanol port injection (EPI) system was installed on a gasoline direct injection (GDI) engine and a dual-fuel dual-injection system was assembled so that the blended ratio of fuel could be timely adjusted. By employing the innovative EPI and GDI dual-fuel dual-injection system at typical urban operating conditions, the fuel economy, particle number and mass emissions were studied, and the combustion characteristics and gaseous regulated emissions were also analyzed. The results show that bESFC(equivalent specific fuel consumption) decreases with the increase of Rethanol (ethanol port injection ratio), and mole multiplier effect is enhanced by adding ethanol. More combustion products are available to do more work during the expansion process, and thereby improves the brake thermal efficiency. Hydrocarbon (HC) emission decreases with the increase of Rethanol and is independent of engine loads. Particles number and mass under various conditions decrease with the increase ofRethanol. Favorable evaporation characteristics as well as higher oxygen content of ethanol leads to less soot precursors formation and enhanced particle oxidation. Ethanol forms an azeotropes with gasoline, which enhances the volatility of gasoline and improves the mixture quality, and further reduces particle emission.
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