A reliable mathematical model of urea-water-solution(UWS) droplet evaporation and thermolysis is developed.The well known Abramzon–Sirignano evaporation model is corrected by introducing an adjustment coefficient con...A reliable mathematical model of urea-water-solution(UWS) droplet evaporation and thermolysis is developed.The well known Abramzon–Sirignano evaporation model is corrected by introducing an adjustment coefficient considering the different evaporation behaviors of UWS droplet at different ambient temperatures. A semidetailed kinetic scheme of urea thermolysis is developed based on Ebrahimian's work. Sequentially, the evaporation characteristics, decomposition efficiency of a single UWS droplet and deposit formation are simulated. As a result, the relation of evaporation time, relative velocity, exhaust temperature and droplet initial diameter is presented. Synchronously, it indicates that temperature is the decisive factor for urea thermolysis. Different temperatures result in different deposit components, and deposit yield is significantly influenced by temperature and decomposition time. The current work can provide guidance for designing urea injection strategy of SCR systems.展开更多
Diesel vehicles have caused serious environmental problems in China.Hence,the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in...Diesel vehicles have caused serious environmental problems in China.Hence,the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in the latest China VI standard.To fulfill this stringent legislation,two major technical routes,including the exhaust gas recirculation(EGR)and high-efficiency selective catalytic reduction(SCR)routes,have been developed for diesel engines.Moreover,complicated aftertreatment technologies have also been developed,including use of a diesel oxidation catalyst(DOC)for controlling carbon monoxide(CO)and hydrocarbon(HC)emissions,diesel particulate filter(DPF)for particle mass(PM)emission control,SCR for the control of NOx emission,and an ammonia slip catalyst(ASC)for the control of unreacted NH3.Due to the stringent requirements of the China VI standard,the aftertreatment system needs to be more deeply integrated with the engine system.In the future,aftertreatment technologies will need further upgrades to fulfill the requirements of the near-zero emission target for diesel vehicles.展开更多
基金Supported by the National High Technology Research and Development Program of China(2013AA065301)the Fundamental Research Funds for the Central Universities(2016QNA4014)the State Key Laboratory of Clean Energy Utilization at Zhejiang University(ZJUCEU2016006)
文摘A reliable mathematical model of urea-water-solution(UWS) droplet evaporation and thermolysis is developed.The well known Abramzon–Sirignano evaporation model is corrected by introducing an adjustment coefficient considering the different evaporation behaviors of UWS droplet at different ambient temperatures. A semidetailed kinetic scheme of urea thermolysis is developed based on Ebrahimian's work. Sequentially, the evaporation characteristics, decomposition efficiency of a single UWS droplet and deposit formation are simulated. As a result, the relation of evaporation time, relative velocity, exhaust temperature and droplet initial diameter is presented. Synchronously, it indicates that temperature is the decisive factor for urea thermolysis. Different temperatures result in different deposit components, and deposit yield is significantly influenced by temperature and decomposition time. The current work can provide guidance for designing urea injection strategy of SCR systems.
基金supported by the National Key R&D Program of China(No.2017YFC0211101)the Key Project of National Natural Science Foundation(No.21637005)+1 种基金the Cultivating Project of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDPB1902)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23010200)。
文摘Diesel vehicles have caused serious environmental problems in China.Hence,the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in the latest China VI standard.To fulfill this stringent legislation,two major technical routes,including the exhaust gas recirculation(EGR)and high-efficiency selective catalytic reduction(SCR)routes,have been developed for diesel engines.Moreover,complicated aftertreatment technologies have also been developed,including use of a diesel oxidation catalyst(DOC)for controlling carbon monoxide(CO)and hydrocarbon(HC)emissions,diesel particulate filter(DPF)for particle mass(PM)emission control,SCR for the control of NOx emission,and an ammonia slip catalyst(ASC)for the control of unreacted NH3.Due to the stringent requirements of the China VI standard,the aftertreatment system needs to be more deeply integrated with the engine system.In the future,aftertreatment technologies will need further upgrades to fulfill the requirements of the near-zero emission target for diesel vehicles.
