模拟碳烟在DPF过滤壁面上沉积特性的试验
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摘要
基于可视化单通道试验台架,采用固体颗粒发生器产生来流颗粒使颗粒均匀沉积到柴油机颗粒捕集器(DPF)过滤壁面上,使用激光位移传感器在线测量过滤壁面上颗粒层厚度和电镜离线观测颗粒层形貌与结构,对碳黑颗粒特性和灰沉积量在DPF过滤壁面上的沉积过程开展研究.结果表明:针对颗粒层厚度曲线,沉积过程可分为深床期、长树期、搭桥期及颗粒层期;而针对过滤压降曲线分为深床期、过渡期和颗粒层期.随壁面过滤速度增大,过滤压降增大,颗粒层厚度增大,形成的颗粒层越致密,且厚度曲线进入颗粒层期的厚度从15μm增加至约30μm.在固定的壁面过滤速度工况下,由于碳黑颗粒特性存在差异,颗粒自身团聚程度越高(SB4A>FW200>PU),对应的最终过滤压降和堆积密度越大.在有灰沉积的工况下,随着灰沉积量从0 g/L增加至6 g/L,沉积碳黑颗粒时,DPF的初始压降增大,但最终过滤压降和碳黑颗粒层的堆积密度呈先减小后增大的趋势,尤其在灰沉积量为2 g/L时同时达到最低.
Based on a visualized single channel filtration testing bench,on which a solid particle generator is used to generate particles on the diesel particulate filters'(DPF)surface,the deposition characterization of particle layer in diesel particle filter was investigated online by laser displacement measurement and offline by microscopic technology.Then,the effect of surface filtration velocity,carbon blacks' specification and ash loading was investigated in the experiment. Results show that the soot deposition process could be divided into four stages based on the particle layer thickness curve:the deep bed filtration stage,the particle tree growth stage,the particle tree connection stage and the particle layer filtration stage. It also could be divided into deep bed filtration stage,transition stage and particle layer filtration stage based on the pressure drop curve. The particle deposition process begins at the particle layer filtration stage when the layer thickness reaches about 15—30 μm under the different surface filtration velocities tested.Increasing the surface filtration velocity leads to the increase of pressure drop and layer thickness with denser soot layer. The aggregation degrees of different commercial carbon black particles(SB4 A>FW200>PU)plays an important role in filtration pressure drop and bulk density. With the increase in the amount of ash deposited on the surface(0—6 g/L),the initial pressure drop increases,but the filtration pressure drop and soot cake bulk density decrease at first and then increase gradually. When the ash deposition is 2 g/L,the final pressure drop and soot cake bulk density reach their minimum values.
Based on a visualized single channel filtration testing bench,on which a solid particle generator is used to generate particles on the diesel particulate filters'(DPF)surface,the deposition characterization of particle layer in diesel particle filter was investigated online by laser displacement measurement and offline by microscopic technology.Then,the effect of surface filtration velocity,carbon blacks' specification and ash loading was investigated in the experiment. Results show that the soot deposition process could be divided into four stages based on the particle layer thickness curve:the deep bed filtration stage,the particle tree growth stage,the particle tree connection stage and the particle layer filtration stage. It also could be divided into deep bed filtration stage,transition stage and particle layer filtration stage based on the pressure drop curve. The particle deposition process begins at the particle layer filtration stage when the layer thickness reaches about 15—30 μm under the different surface filtration velocities tested.Increasing the surface filtration velocity leads to the increase of pressure drop and layer thickness with denser soot layer. The aggregation degrees of different commercial carbon black particles(SB4 A>FW200>PU)plays an important role in filtration pressure drop and bulk density. With the increase in the amount of ash deposited on the surface(0—6 g/L),the initial pressure drop increases,but the filtration pressure drop and soot cake bulk density decrease at first and then increase gradually. When the ash deposition is 2 g/L,the final pressure drop and soot cake bulk density reach their minimum values.
引文
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[14]Boger T,Rose D,Nicolin P,et al.Oxidation of soot(Printex U)in particulate filters operated on gasoline engines[J].Emission Control Science&Technology,2015,1(1):49-63.
[15]Jing H U,Zhun H U,Zhang J,et al.XPS analysis of the soot oxidation characteristics with Si-Al catalyst effects[J].Journal of Automotive Safety&Energy,2016,7(2):236-240.
[16]Dilip K V,Vasa N J,Carsten K,et al.Incineration of diesel particulate matter using induction heating technique[J].Applied Energy,2011,88(3):938-946.
[17]龚金科,龙罡,余明果,等.微粒捕集器连续再生速率与压降特性研究[J].湖南大学学报:自然科学版,2009,36(6):22-27.
[18]Piscaglia F,Ferrari G.A novel 1D approach for the simulation of unsteady reacting flows in diesel exhaust after-treatment systems[J].Energy,2009,34(12):2051-2062.
[19]谭丕强,邹乐华,胡志远,等.重型柴油机起动工况的颗粒数量排放特性[J].内燃机学报,2016,34(5):431-437.
[20]田维,张洵,赵家辉.颗粒物粒径对EGR冷却器沉积物及换热效率的影响[J].内燃机学报,2017,35(4):326-331.
[21]Fang J,Meng Z W,Li J,et al.The influence of ash on soot deposition and regeneration processes in diesel particular filter[J].Applied Thermal Engineering,2017,124:633-640.
[2]Johnson T V.Review of diesel emissions and control[J].International Journal of Engine Research,2010,10(5):275-285.
[3]Wang D,Liu Z C,Han Y Q,et al.Experimental studies on pressure drop performance and regeneration safety of diesel particulate filter[C]//ICEICE Paper.Wuhan,Hubei,China,2011:2175-2178.
[4]孟忠伟,宋蔷,姚强,等.柴油机颗粒捕集器内颗粒沉积结构的实验研究[J].燃烧科学与技术,2012,18(1):20-26.
[5]Mokhri M A,Abdullah N R,Abdullah S A,et al.Soot filtration recent simulation analysis in diesel particulate filter(DPF)[J].Procedia Engineering,2012,41:1750-1755.
[6]Bensaid S,Marchisio D L,Fino D,et al.Modelling of diesel particulate filtration in wall-flow traps[J].Chemical Engineering Journal,2009,154:211-218.
[7]Daido S,Takagi N.Visualization of the PM deposition and oxidation behavior inside the DPF wall[C]//SAEPaper.Detroit,Michigan,USA,2009,2009-01-1473.
[8]Tan P Q,Li Y,Shen H Y.Exhaust particle properties from a light duty diesel engine using different ash content lubricating oil[J].Journal of the Energy Institute,2018,91(1):55-64.
[9]Liati,Eggenschwiler D,Gubler M,et al.Investigation of diesel ash particulate matter:A scanning electron microscope and transmission electron microscope study[J].Atmospheric Environment,2012,49(3):391-402.
[10]Sappok A,Santiago M,Vianna T,et al.Characteristics and effects of ash accumulation on diesel particulate filter performance:Rapidly aged and field aged results[C]//SAE Paper.Detroit,Michigan,USA,2009,2009-01-1086.
[11]Viswanathan S,Rakovec N,Foster D E.Microscale study of ash accumulation process in DPF walls using the diesel exhaust filtration analysis(DEFA)system[C]//ASME 2012 Internal Combustion Engine Division Fall Technical Conference,2012:537-549.
[12]Tighe C J,Twigg M V,Hayhurst A N,et al.The kinetics of oxidation of diesel soots and a carbon black(Printex U)by O2 with reference to changes in both size and internal structure of the spherules during burnout[J].Carbon,2016,107:20-35.
[13]Sánchez N E,Salafranca J,Callejas A,et al.Quantification of polycyclic aromatic hydrocarbons(PAHs)found in gas and particle phases from pyrolytic processes using gas chromatography-mass spectrometry(GC-MS)[J].Fuel,2013,107(9):246-253.
[14]Boger T,Rose D,Nicolin P,et al.Oxidation of soot(Printex U)in particulate filters operated on gasoline engines[J].Emission Control Science&Technology,2015,1(1):49-63.
[15]Jing H U,Zhun H U,Zhang J,et al.XPS analysis of the soot oxidation characteristics with Si-Al catalyst effects[J].Journal of Automotive Safety&Energy,2016,7(2):236-240.
[16]Dilip K V,Vasa N J,Carsten K,et al.Incineration of diesel particulate matter using induction heating technique[J].Applied Energy,2011,88(3):938-946.
[17]龚金科,龙罡,余明果,等.微粒捕集器连续再生速率与压降特性研究[J].湖南大学学报:自然科学版,2009,36(6):22-27.
[18]Piscaglia F,Ferrari G.A novel 1D approach for the simulation of unsteady reacting flows in diesel exhaust after-treatment systems[J].Energy,2009,34(12):2051-2062.
[19]谭丕强,邹乐华,胡志远,等.重型柴油机起动工况的颗粒数量排放特性[J].内燃机学报,2016,34(5):431-437.
[20]田维,张洵,赵家辉.颗粒物粒径对EGR冷却器沉积物及换热效率的影响[J].内燃机学报,2017,35(4):326-331.
[21]Fang J,Meng Z W,Li J,et al.The influence of ash on soot deposition and regeneration processes in diesel particular filter[J].Applied Thermal Engineering,2017,124:633-640.