柴油机颗粒过滤器再生过程的碳氢喷射模拟(英文)

摘要

Diesel oxidation catalyst (DOC) upstream of catalyzed diesel particulate filter (CDPF) with additional diesel injection (hydrocarbon injection,HCI) were used to control the particulate matter (PM) emissions to meet stringent emission regulations for heavy-duty diesel vehicles.This study optimized the location of injector upstream of DOC by evaluating the uniformity of HC distribution on the entrance of DOC.An HCI was used in active regeneration to enhance the exothermic heat of CDPF to initiate the soot regeneration.Numerical analysis was established for the combination of after-treatment technology DOC-CDPF,and a spray model for HCI was implemented into a commercial CFD code named AVL FIRE.Different locations and orientations of the injector were tested.The results show that injector location has a significant effect on the optimal mixing between the exhaust gas and injected hydrocarbon (HC).Optimum injector location is the injector located farthest from DOC,while the long distance between injector and DOC allows enough time for injected HC to form secondary droplets,as it mixes well with exhaust gas downstream.Using HCI upstream of DOC causes the exhaust gas temperature to increase and reaches 550 ℃ at the entrance of CDPF,which is enough to initiate active DPF regeneration.%为满足严格的重型柴油机排放法规,柴油催化氧化器(DOC)和催化型柴油颗粒捕集器(CDPF)得到了广泛的应用.碳氢喷射(HCI)是一种实现DPF主动再生的有效方法.该文通过改变柴油喷嘴位置来优化DOC入口的碳氢化合物(HC)分布.使用计算流体力学软件AVL-FIRE,建立了DOC-CDPF模型,用软件内置HCI喷雾模型,对喷射器的安装位置和喷射方向进行了数值模拟.模拟结果显示:喷射器的位置对HC分布有很大的影响,喷射器位置距离DOC越远,DOC入口处的HC混合均匀性越高,这是因为喷雾在DOC前有更长的距离和时间形成均匀混合气;排气管喷射柴油可以使DPF入口温度达到550℃,满足了CDPF主动再生的需求.