实现低NO_(x)排放的紧耦合后处理器匹配  

A Close-Couple Aftertreatment Matching Research for Low NO_(x) Emissions

作　　者：李金成 尧命发[1] 郑尊清[1] 王浒[1] Li Jincheng;Yao Mingfa;Zheng Zunqing;Wang Hu(State Key Laboratory of Engines,Tianjin University,Tianjin 300350,China)

机构地区：[1]天津大学内燃机燃烧学国家重点实验室,天津300350

出　　处：《内燃机学报》2023年第2期141-149,共9页Transactions of Csice

摘　　要：重型柴油机排放法规不断降低氮氧化物(NO_(x))限值,采用紧耦合选择性催化还原(SCR)是预期技术路线之一,但是否需采用紧耦合柴油氧化催化器(DOC)以改善紧耦合SCR入口NO_(2)比例仍需要进一步探讨.通过一台商用柴油机,在GT-Power平台分别搭建DOC和SCR小样模型,基于小样试验数据和遗传算法对反应动力学机理参数进行初步标定,然后使用测试循环数据对机理参数进行修正,进而构建了DOC-DPF-SCR-ASC系统模型.基于系统模型对采用紧耦合DOC的必要性进行了探讨,结果表明:紧耦合DOC会增加紧耦合SCR前的热惯性,使紧耦合SCR的冷起动性能变差.基于系统模型还开展了两级SCR之间的体积匹配,可知柴油机采用主SCR体积为9.94 L时,匹配紧耦合体积为2.13 L的SCR可使系统冷起动工况SCR转化效率由63.0%提高到77.8%,NO_(x)排放降低了42.4%;冷、热起动世界统一瞬态循环(WHTC)加权后的NO_(x)排放由0.38 g/(kW·h)下降到0.21 g/(kW·h),降低了44.7%.Heavy-duty diesel engine emission regulations continue to reduce nitrogen oxide(NO_(x)) limits,and using close-couple selective catalytic reduction(SCR) is one of the expected technical routes. However,whether it is necessary to use a close-couple diesel oxidation catalytic(DOC) to improve the NO_(2)ratio at the inlet of the closecouple SCR still needs further investigation. The DOC and SCR small sample models were respectively developed in this study based on GT-Power platform for a commercial diesel engine. Initial calibration of reaction kinetic mechanism parameters based on small sample test data and genetic algorithms,a DOC-DPF-SCR-ASC combined system model was built by preliminary calibration,and then using the test cycle data to correct the mechanism parameters. Based on the system model,the necessity of using close-couple DOC was discussed,and the results show that close-couple DOC will increase the thermal inertia before the close-couple SCR and reduce the cold start performance of the close-couple SCR. A volume matching study between the two-stage SCRs was also carried out.When the main SCR volume is 9.94 L,matching the close-couple SCR with a volume of 2.13 L can make the SCR conversion efficiency under cold start to increase from 63.0% to 77.8% and NO_(x)is decreased by 42.4%. Weighted NO_(x)specific emissions obtained on hot and cold world harmonized transient cycle(WHTC) operating cycles are decreased from 0.38 g/(k W·h) to 0.21 g/(kW·h),a decrease of 44.7%.

关 键 词：重型柴油机 低NO_(x)排放 紧耦合柴油氧化催化器 转化效率 

分 类 号：TK421.5[动力工程及工程热物理—动力机械及工程]