【作者】 覃军；

【导师】 陈辉；

【作者基本信息】 武汉理工大学 ， 动力机械及工程， 2007， 博士

【摘要】 随着柴油机排放法规的日益严格,后处理技术是满足欧Ⅳ及以上排放法规必须采用的技术措施。在商用车满足欧Ⅳ和欧Ⅴ排放法规技术路线中,目前国际上普遍采用两种技术路线,其一是通过燃烧系统优化降低微粒排放采用选择性催化还原（SCR）降低NOx排放;其二是通过废气再循环（EGR）降低NOx排放采用微粒过滤器后处理技术。通过大量的理论和国外应用情况分析,作者认为SCR技术更适合我国当前国情。为此,本文在YC6L350-40重型柴油机上对选用SCR后处理技术进行了应用研究,并成功开发了国内第一台满足欧Ⅳ排放商用柴油机。研究内容包括SCR系统的基础特性研究,还原剂剂量控制策略的制定,SCR系统的评价验证试验以及低温运行条件下和使用高硫柴油SCR系统的适用性研究,并对SCR技术应用存在问题进行了分析。本文首先研究了氧化还原型金属氧化物催化剂的作用机理和氨气（NH₃）—SCR反应的原理,对计量单元流量特性进行了标定,并对计量阀开启频率进行了研究。通过试验与理论相结合的研究方法,绘制了发动机NOx原机排放脉谱图、排气背压脉谱图、催化器的降低量脉谱图以及NOx最大转化率脉谱图,通过脉谱图与计量装置流量特性标定结果,初步制定了稳态下还原剂剂量控制策略。在此基础上,根据发动机排温和尿素水溶液温度对控制策略进行了修正,同时SCR系统氨气滑失不易控制,提出了对还原剂剂量控制策略进行催化剂储氨能力修正的思路。按照GB17691—2005《车用压燃式、气体燃料点燃式发动机与汽车排气污染物排放限值及测量方法》中对采用排气后处理措施重型柴油机国Ⅳ排放检验要求,在中国汽车技术研究中心对YC6L350-40柴油机采用SCR系统进行了ESC和ETC评价验证试验。结果表明,采用本课题所研究控制策略的SCR系统重型发动机在燃用欧Ⅲ和欧Ⅳ标准油的情况下,排放都可以达到我国第Ⅳ阶段排放要求。为了研究公交车运行条件下SCR系统的适用性,本文根据武汉市公交车路谱试验数据确定了十五个工况,以此作为SCR系统1000小时可靠性试验循环工况。工况特点是低速部分负荷运行比例高、发动机排温低,使用的柴油含硫量接近2000ppm。试验结果表明SCR系统在低排温和使用高硫柴油条件下,当尿素水溶液最低喷入温度为230℃时催化器的活性比较稳定;但当最低喷入温度为200℃时催化器的活性略有下降。作者最后根据国外SCR应用经验,提出了我国建设“添蓝”加注站的方案,并预测了方案具体实施中可能遇到的问题。本文研究结果对开发满足国Ⅳ排放商用柴油机有重要的参考价值,探索了开发符合我国国情的国Ⅳ排放商用柴油机技术路线,研究结果有很高的应用价值,对我国降低商用柴油机排放、减少大气污染有重要的社会意义更多还原

【Abstract】 The after-treatment technologies are the major measures to meet the emerging stringent emission legislation limits. Inducing all the Routes studied by diesel engine manufactures to deal with Euro IV and Euro V treaties two kinds are concluded, which one is reduce NO_X emission with selective catalytic reduction （SCR） technologe on the basis of combustion optimization to reduce PM and the other debase NO_X emission with exhaust gas recycle （EGR） and PM with PDF.By the analysis of the principle and the ultilization of SCR, the author draws a conclusion that the SCR System is very the proper choice taking into account Chinese reality. So a set of SCR devices are fited on a YC6L350-40 HD diesel engine and investigated, including the base performance of the SCR System, the study of reducer control strategy, the investigation of the SCR System, the applicability evalutation of the SCR System for running with high sulphur content fuel on the engine and the analyse of issues with the system. As a result the first Euro IV HD diesel engine is produced by China.At the very start the action mechanism of the metal oxid catalyst with redox and the reaction mechanism of NH₃-SCR are introduced detailedly, and then the dosing unit performance is calibrated, and the on-off frequency of the dosing valve is investigated also. The control strategy of reducer is studied combining with raw NO_X emission map, exhaust gas pressure map, catalyst reduction map and NO_X conversion map obtained through engine test and theory analysis, and then the strategy is amended according to exhaust temperature and urea solution temperature, at the same time the thought about the modification due to the effect of the ammonia storage capbility of the catalyst is induced. The SCR System is demonstrated according to GB17691-2005 requirements for diesel engine and exhaust after-treatment systems through ESC tests and ETC tests at the Chinese Automobile Test Center and the conclusion is drawed that the HD engine equipped with the SCR System even in the case of running Euro III standard diesel meets the NO. IV era emission standards.In order to investigate the applicability for the SCR System to work as city bus after-treatment device, fifteen modes most located in low speed and portial load are induced as 1000 hour cycle modes with nearly 2000 ppm sulphur content fuel. The conclusion is drawed that on the condition of high sulfur content the catalyst activity keeps steaty with reducer lowest delivery temperature of 230℃and some attenuation with 200℃. In the end, the project and troublesome concerning "Adblue" station constructure is discussed referring to oversea correlative experience.The author’s production possesses important reference value for Euro IV HD diesel engine development. The reasonable technology route for the NO. IV era emission control is explored according to the situation of our country. The production takes on rich utility value and has far-reaching society meaning for China to low engine baleful emission and to decrease environment pollution.更多还原