催化转化器内部瞬态流动过程CFD分析
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摘要
运用计算流体力学(computational fluid dynamics,CFD)方法分析了催化转化器内部瞬态流场的变化。结果表明:沿催化转化器载体轴向,由于入口处壁面的影响及尾部发生边界层分离,在进出口处分别出现两个气流速度低峰;在载体某一截面径向方向上,气流速度和温度都呈现中央高而边缘低的分布;由于固相热导率和热容量大,催化转化器固相上的温度变化很小;在一个工作循环中,随着曲轴转角变化,由于管壁处形成的漩涡区,催化转化器中气流均匀性系数先降低后升高,而由于流动阻力的影响,压力损失先上升后下降。研究可为催化转化器设计及性能分析提供依据与参考。
The transient flow distribution ina catalytic convertor is comprehensively analyzed with employing computational fluid dynamics.The simulationresults show that the axial flow velocity in the carrierof the catalytic converteris relatively stable, howevertwo low velocity peaks come out near the entrance and outlet of the carrier respectively, which are due to the wall effects at the front entrance and the boundary layer separation at the outlet. At one given section in the carrier, in radial the velocity and temperature tend to decline from the center to the edge of wall. The temperature of the solid phase changes little due to its' high thermal conductivity and capacity. In a working cycle, the pressure drop increases first and then decreases with the increase of crank angle due to vortex zones formed at the wall while the coefficient of uniformity is just opposite owing to flow resistance. The results above can providea favorable basis and reference for the designof catalyst converter as well as its' s performance analysis.
The transient flow distribution ina catalytic convertor is comprehensively analyzed with employing computational fluid dynamics.The simulationresults show that the axial flow velocity in the carrierof the catalytic converteris relatively stable, howevertwo low velocity peaks come out near the entrance and outlet of the carrier respectively, which are due to the wall effects at the front entrance and the boundary layer separation at the outlet. At one given section in the carrier, in radial the velocity and temperature tend to decline from the center to the edge of wall. The temperature of the solid phase changes little due to its' high thermal conductivity and capacity. In a working cycle, the pressure drop increases first and then decreases with the increase of crank angle due to vortex zones formed at the wall while the coefficient of uniformity is just opposite owing to flow resistance. The results above can providea favorable basis and reference for the designof catalyst converter as well as its' s performance analysis.
引文
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[8]钱多德,姚炜.汽油机排气歧管内流场CFD模拟[J].内燃机与动力装置,2010,119(5):30-32.(Qian Duo-de,Yao Wei.The CFD simulationof interior flowfor gasoline engine exhaust manifold[J].Internal Combustion Engine&Powerplant,2010,119(5):30-32.)
[9]邓帮林,刘敬平,杨靖,等.基于双向流固耦合的汽油机排气歧管热应力分析[J].内燃机学报,2011,29(6):549-554.(Deng Bang-lin,Liu Jing-ping,Yang Jing,et al.Thermal stress analy-sis of gasoline engine exhaust manifold based on two-way FSI[J].Transactions of CSICE,2011,29(6):549-554.)
[2]帅石金,王建昕,庄人隽.车用催化转化器流场的数值模拟[J].小型内燃机,2000,29(5):23-26.(Shuai Shi-jin,Wang Jian-xin,Zhuang Ren-jun.Numerical simula-tion of automotive catalytic converters[J].Small Internal Combus-tion Engine,2000,29(5):23-26.)
[3]梅德纯,高为群,刘志鑫.催化转化器内单孔道化学反应的研究[J].小型内燃机与摩托车,2013,42(6):29-32.(Mei De-chun,Gao Wei-qun,Liu Zhi-xin.The research of chemical reactions of single span way in catalytic converter[J].Small Internal Combustion Engine And Motorcycle,2013,42(6):29-32.)
[4]范晓梅,许勇,杨群立,等.发动机排气压力波性能仿真分析[J].计算机仿真,2010,27(2):282-285.(Fan Xiao-mei,Xu Yong,Yang Qun-li,et al.Simulationand analysiso fangine exhaust pressure wave[J],Computer Simulation,2010,27(2):282-285.)
[5]Shuai Shi-jin,Wang Jian-xin.Unsteady temperature fields of mono-liths in catalytic converters[J].Chemical Engineering Journal,2004(100):95-107.
[6]Chakravarthy V K,Conklin J C,Daw C S,et al.Multi-dimensional simulations of cold-start transients in a catalytic converter under steady inflow conditions[J].Applied Catalysis A:General:2003(241):289-306.
[7]Gao Xi,Zhu Ya-ping,Luo Zheng-hong.CFD modeling of gas flow in porous medium and catalytic coupling reaction from carbon monoxide to diethyl oxalate in fixed-bed reactors[J].Chemical Enginee-ring Science,2011(66):6028-6038.
[8]钱多德,姚炜.汽油机排气歧管内流场CFD模拟[J].内燃机与动力装置,2010,119(5):30-32.(Qian Duo-de,Yao Wei.The CFD simulationof interior flowfor gasoline engine exhaust manifold[J].Internal Combustion Engine&Powerplant,2010,119(5):30-32.)
[9]邓帮林,刘敬平,杨靖,等.基于双向流固耦合的汽油机排气歧管热应力分析[J].内燃机学报,2011,29(6):549-554.(Deng Bang-lin,Liu Jing-ping,Yang Jing,et al.Thermal stress analy-sis of gasoline engine exhaust manifold based on two-way FSI[J].Transactions of CSICE,2011,29(6):549-554.)