短链醇酯与柴油混合燃料燃烧过程分析  

Combustion process in a diesel engine using diesel blends with short-chain ethanol and ester

作　　者：杜家益[1] 戴鹏飞[1] 徐行 梅德清[1] 吴焓 陈晨 陶俊 

机构地区：[1]江苏大学汽车与交通工程学院,江苏镇江212013 [2]江苏苏扬包装股份有限公司,江苏扬州211400

出　　处：《扬州大学学报（自然科学版）》2017年第4期42-46,共5页Journal of Yangzhou University：Natural Science Edition

基　　金：国家自然科学基金资助项目(51376095;51506101);江苏省科技厅重点研发计划资助项目(BE2016139);江苏高校品牌专业建设工程资助项目(苏政发办[2014]82号)

摘　　要：为了解短链醇酯混合燃料的燃烧特性,在柴油机上燃用不同比例乙醇-碳酸二甲酯(DMC)-柴油多元混合含氧燃料,并运用Chemkin软件模拟缸内燃烧氧化动力学性质,探究含氧官能团对燃烧过程影响的机理.结果表明:由于短链醇酯燃料具有较高的汽化焓及较低的十六烷值,延缓了混合燃料的着火过程,故随混合燃料中乙醇和DMC掺混比例的增加,缸压曲线不断后移,压力峰值逐步降低;但由于着火延迟期内形成的可燃混合气量增多,使放热率峰值逐步上升.反应动力学结果显示:低温区活性自由基·OH主要由正庚烷(柴油替代物)脱氢生成,乙醇和DMC的加入能争夺低温反应区内的·OH,使反应活性较强的·OH转化为活泼性稍差的H_2O_2,抑制了整个燃烧过程,使着火延迟期变长;在高温阶段,乙醇分子中C—C和C—O键的断裂优于C—H和O—H键,而DMC主要发生C—O的裂解,C=O键因键能更高未断裂.In order to understand the combustion characteristics of short-chain ethanol and ester mixed fuel, oxygenated ethanol-DMC-diesel fuel blends with various mixing ratios are used in a diesel engine. Using the detailed reaction kinetics analysis based on Chemkin, the influences of oxygen-containing functional groups on the combustion process are explored. It is revealed that with the increase of ethanol and DMC fractions, the ignition delay is prolonged due to the low cetane number of oxygenated fuel blends, and the bulk gas temperature in cylinder is declined as well because of their high vaporization enthalpy. Therefore, the pressure profiles move backward gradually. Meanwhile, the pressure peak declines while the heat release peak raises progressively resulted from more flammable mixtures. According to detailed reaction kinetics, ·OH is mainly generated by dehydrogenation of n-heptane （as a surrogate of diesel） at the stage of low temperature reaction. However, active ＊OH is absorbed by ethanol and DMC, and then turns into H20 2 ？ which holds the whole combustion process slowly. Then, the ignition delay is prolonged. At the stage of high temperature reaction, the break of C -C bonds and C -O bonds in ethanol molecules is easier than that of C -H bonds and O -H bonds, while in DMC molecules, the break mainly occurs at C-O bonds, and the C=0 bonds are rare broken due to higher bond energy.

关 键 词：乙醇 碳酸二甲酯 混合燃料 化学反应动力学 燃烧特性 

分 类 号：TK421.3[动力工程及工程热物理—动力机械及工程]