结构参数对Urea-SCR系统性能的影响研究
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摘要
通过建立SCR系统数值模型,对柴油机SCR系统尿素水溶液喷雾分解和催化剂表面的化学反应过程进行模拟。结合台架试验,研究了喷嘴喷射角度α、催化器扩张角β和混合器及其安装位置等因素对SCR系统NO_x转化率、NH_3分布均匀性和液膜质量等的影响规律。结果表明:喷射角度和催化器扩张角的影响规律比较复杂,须根据具体情况选定;加装混合器后,可产生明显的排气旋流,有效延长UWS液滴的运动轨迹,促进其与排气的良好混合,明显提高SCR系统NO_x的转化率,它安装于喷嘴下游100～200mm处较为合理。
A numerical model for selective catalytic reduction( SCR) system is established,on which the spray decomposition of urea water solution( UWS) and the chemical reaction process on the catalyst surface of diesel SCR system are simulated. Bench tests are also conducted to study the influence of the nozzle injection angleα,the expansion angle β of catalyzer and the mixer and its location on the NO_x conversion rate,the NH_3 distribution uniformity and the liquid film mass of SCR system. The results show that the influence rule of the nozzle injection angle α and the expansion angle β of catalyzer are rather complicated so they should be chosen according to specific situations,while the adding of mixer can produce apparent exhaust swirl,effectively extend the motion trajectory of UWS drops,promote their good mixing with exhaust gas and greatly increase the NOxconversion rate of SCR system,and it is more reasonable to install the mixer at a location 100-200 mm downstream of the nozzle.
A numerical model for selective catalytic reduction( SCR) system is established,on which the spray decomposition of urea water solution( UWS) and the chemical reaction process on the catalyst surface of diesel SCR system are simulated. Bench tests are also conducted to study the influence of the nozzle injection angleα,the expansion angle β of catalyzer and the mixer and its location on the NO_x conversion rate,the NH_3 distribution uniformity and the liquid film mass of SCR system. The results show that the influence rule of the nozzle injection angle α and the expansion angle β of catalyzer are rather complicated so they should be chosen according to specific situations,while the adding of mixer can produce apparent exhaust swirl,effectively extend the motion trajectory of UWS drops,promote their good mixing with exhaust gas and greatly increase the NOxconversion rate of SCR system,and it is more reasonable to install the mixer at a location 100-200 mm downstream of the nozzle.
引文
[1]帅石金,唐韬,赵彦光,等.柴油车排放法规及后处理技术的现状与展望[J].汽车安全与节能学报,2012,3(3):200-217.
[2] JOHNSON T. Vehicular emissions in review[J]. SAE International Journal of Engines,2012,7(3):1207-1227.
[3] LI Z,DENG J,LI L,et al. A study on the factors affecting heated wall impinging characteristics of SCR spray[C]. SAE Paper 2011-01-1311.
[4] BALETA J,VUJANOVI C'M,PACHLER K,et al. Numerical modeling of urea water based selective catalytic reduction for mitigation of NOxfrom transport sector[J]. Journal of Cleaner Production,2015,88(12):280-288.
[5] LUNDSTROM A,STROM H,SKOGLUNDH M. Dispersion aspects of NH3-delivery strategies for NH3-based SCR systems[J].Topics in Catalysis,2013,56(1-8):75-79.
[6] OH J,LEE K. Spray characteristics of a urea solution injector and optimal mixer location to improve droplet uniformity and NOxconversion efficiency for selective catalytic reduction[J]. Fuel,2014,119(1):90-97.
[7] RAJADURAI S. Improved NOxreduction using wiremesh thermolysis mixer in urea SCR system[C]. SAE Paper 2008-01-2636.
[8]陈冯.车用柴油机Urea-SCR系统数值模拟与试验研究[D].镇江:江苏大学,2014:25-29.
[9] JAMBHEKAR V A. Forchheimer porous-media flow models-numerical investigation and comparison with experiment data[D].Stuttgart:University of Stuttgart,2011:20-23.
[10] COLOMBO M,NOVA I,TRONCONI E,et al. Mathematical modelling of cold start effects over zeolite SCR catalysts for exhaust gas aftertreatment[J]. Catalysis Today,2014,231(231):99-104.
[11]蔡忆昔,唐炜,王军,等.基于NOx传感器NH3交叉感应的柴油机Urea-SCR的试验[J].内燃机学报,2015,33(5):461-465.
[12] ZUKERMAN R,VRADMAN L,HERSKOWITZ M,et al. Modeling and simulation of a smart catalytic converter combining NOx storage,ammonia production and SCR[J]. Chemical Engineering Journal,2009,155(1-2):419-426.
[13] ZHAN R,LI W,EAKLE S T,et al. Development of a novel device to improve urea evaporation,mixing and distribution to enhance SCR performance[C]. SAE Paper 2009-01-2879.
[14] WELTENS H,BRESSLER H,TERRES F,et al. Optimisation of catalytic converter gas flow distribution by CFD prediction[C].SAE Paper 930780.
[15] ZHAN R,LI W,EAKLE S T,et al. Development of a novel device to improve urea evaporation,mixing and distribution to enhance SCR performance[C]. SAE Paper 2010-01-1185.
[2] JOHNSON T. Vehicular emissions in review[J]. SAE International Journal of Engines,2012,7(3):1207-1227.
[3] LI Z,DENG J,LI L,et al. A study on the factors affecting heated wall impinging characteristics of SCR spray[C]. SAE Paper 2011-01-1311.
[4] BALETA J,VUJANOVI C'M,PACHLER K,et al. Numerical modeling of urea water based selective catalytic reduction for mitigation of NOxfrom transport sector[J]. Journal of Cleaner Production,2015,88(12):280-288.
[5] LUNDSTROM A,STROM H,SKOGLUNDH M. Dispersion aspects of NH3-delivery strategies for NH3-based SCR systems[J].Topics in Catalysis,2013,56(1-8):75-79.
[6] OH J,LEE K. Spray characteristics of a urea solution injector and optimal mixer location to improve droplet uniformity and NOxconversion efficiency for selective catalytic reduction[J]. Fuel,2014,119(1):90-97.
[7] RAJADURAI S. Improved NOxreduction using wiremesh thermolysis mixer in urea SCR system[C]. SAE Paper 2008-01-2636.
[8]陈冯.车用柴油机Urea-SCR系统数值模拟与试验研究[D].镇江:江苏大学,2014:25-29.
[9] JAMBHEKAR V A. Forchheimer porous-media flow models-numerical investigation and comparison with experiment data[D].Stuttgart:University of Stuttgart,2011:20-23.
[10] COLOMBO M,NOVA I,TRONCONI E,et al. Mathematical modelling of cold start effects over zeolite SCR catalysts for exhaust gas aftertreatment[J]. Catalysis Today,2014,231(231):99-104.
[11]蔡忆昔,唐炜,王军,等.基于NOx传感器NH3交叉感应的柴油机Urea-SCR的试验[J].内燃机学报,2015,33(5):461-465.
[12] ZUKERMAN R,VRADMAN L,HERSKOWITZ M,et al. Modeling and simulation of a smart catalytic converter combining NOx storage,ammonia production and SCR[J]. Chemical Engineering Journal,2009,155(1-2):419-426.
[13] ZHAN R,LI W,EAKLE S T,et al. Development of a novel device to improve urea evaporation,mixing and distribution to enhance SCR performance[C]. SAE Paper 2009-01-2879.
[14] WELTENS H,BRESSLER H,TERRES F,et al. Optimisation of catalytic converter gas flow distribution by CFD prediction[C].SAE Paper 930780.
[15] ZHAN R,LI W,EAKLE S T,et al. Development of a novel device to improve urea evaporation,mixing and distribution to enhance SCR performance[C]. SAE Paper 2010-01-1185.