Research On The Influence Of Boundary Condition On Lean NO_x Trap Adsorption Path

In this paper,the adsorption of LNT was researched,and Ba?NO₃?₂ and BaO-NO₂site fraction were used to characterize nitrate and nitrite adsorption path.Then the optimal lean-rich time was applied to study the influence of EGR on nitrate and nitrate paths occupation and ratio,finally the effect of CO₂ and inlet temperature on adsorption paths were analyzed.The results are beneficial to enrich adsorption mechanism,improve adsorption efficiency and couple with different after-treatment systems.Firstly,the paper compared adsorption saturation degree and outlet NOx concnentration under different rich-lean absolute duration and ratio through the validated model.The results show that,while time ratio is 8,the influence of absolute duration on adsorption weakens as time follows,and adsorption reaches saturation at56s.When the rich time is 7s,Ba?NO₃?₂ site fraction increases and Ba?NO₃?₂ site fraction decreases at th end of adsorption phase with ratio increasing.Based on above research,the optimal lean-rich time is 56s:7s.Secondly,the boundary conditions with different exhaust components and concentrations under six EGR rates 0%,10%,15%,20%,25%,30%were researched.The occupation ratio of nitrate and nitrite path at 250?is 1:1.82,1:2.41,1:3.77,1:10.25,1:6.61,1:4.73 respectively.At 350?,the ratio is 1:1.63,1:1.89,1:1.22,1:2.92,1:2.68,1:2.47.20%EGR rate is adsorption effect boundary point.Under 0%¹5%EGR rates,occupation ratio increses as EGR rate increases,which means nitrite path intensifies.EGR has inhibition on nitrate path and early inhibition late promotion on nitrite path,the effect intensifies as EGR increases.During 20%³0%EGR rate,as for nitrate path,EGR has promotion at 250?and inhibition at 350?.And EGR has early inhibition and late promotion on nitrite path.The effect on the two paths varies under different temperature.Finally,the influence of CO₂ on two paths during 150?⁵50?was researched.The results show that CO₂ inhibits both nitrate and nitrite path.And the influence on the nitrite path is more significant,but it weakens with CO₂ concentration increasing.The influence on outlet NOx of CO₂ is weak,but the effect on NOx brekthrough is obvious.The temperature has significant influence on adsorption paths.At low temperature interval of 150?²00?,nitrite path dominates.And two paths coexist at moderate temeperatute.Expecially,at 300?and 350?,At 400?,nitrite paths dominates again.At high temperature interval of 450?⁵50?,Ba?NO₃?₂ site fraction approaches zero,and nitrite path dominates.And outlet NOx overflows quickly,and concentration is high.