孔道结构对柴油机DPF压降及再生特性的影响

Pressure drop and soot regeneration characteristics through DPF with different cell structures

针对微粒捕集器(DPF)内部碳烟及灰分颗粒特征,运用AVL-Fire软件建立了六边形孔道结构柴油机微粒捕集器模型。针对不同排气流量、进口温度、孔密度、碳烟和灰分沉积量,对六边形孔道及四边形孔道DPF压降特性和碳烟再生特性进行分析,并研究灰分分布形式对不同孔道形状DPF的影响。结果表明:排气质量流量越大,进口温度越高,不同孔道结构的压降敏感性增大;与传统四边形孔道DPF相比,当碳烟沉积量较低时,六边形孔道DPF压降损失较高;随着碳烟沉积量的增加,六边形孔道DPF压降损失较低,且碳烟承载量较大;灰分在DPF孔道表面层状分布可以有效阻止碳烟深床捕集模式,降低压降损失;六边形孔道DPF能够有效提高碳烟及灰分容量,且碳烟捕集及再生效率较高,再生速率较快,热应力较小,可以降低DPF主动再生频率,延长使用寿命。

A computational fluid dynamics model of hexagonal cell DPF was built by AVL-Fire software code according to the soot and ash deposition characteristics within the filters.The pressure drop and soot regeneration characteristics of hexagonal and conventional square cell DPFs were investigated under various inlet mass flow rates,inlet temperatures,cell densities,soot loads and ash loads.Different cell geometry shapes of DPF were evaluated under various ash distribution types.Results showed that pressure drop increases with the increased DPF inlet mass flow and inlet temperature.In comparison with the conventional square cell DPF,when a small quantity of soot is deposited inside the DPF,the hexagonal cell DPF exhibits a higher pressure loss.Nonetheless,the hexagonal cell DPF has better pressure loss and higher soot capacity at higher soot load.The ash deposited on inlet channel walls prevents soot accumulation and results in lower pressure loss.The hexagonal cell DPF can improve soot and ash capacity,exhibit higher regeneration efficiency and soot oxidation rate,and reduce the thermal stress,which reduces the active regeneration frequency,and pro-longs the DPF life.