柴油机DPF流场压降及微粒沉积特性数值模拟

摘要

Overall pressure drop and soot particle accumulation performance of a diesel particulate filter (DPF)were studied by numerical simulation.The 3-D computational model of DPF was built on the base of AVL-FIRE software code to investigate the effects of inlet mass flow rate,inlet temperature,soot distribution on the overall pressure drop.Especially the effects of asymmetric cell technology (ACT),ash capacity and distribution on the overall pressure drops and soot particle accumulation performance were studied.The results show that the overall pressure drop increases with the increase of DPF inlet mass flow,inlet temperature,soot loading and ash accumulation.But the variation of overall pressure drop takes a non-linear relationship with the inlet temperature.Along the axis direction of the DPF,the PM distribution is non-uniform and both ends of the DPF contain higher soot loading than the middle part.It is also found that the "linear decrease" soot distribution pattern has a lower pressure loss and a faster regeneration rate.In addition,the ash deposited on inlet channel walls has a significant effect on the pressure drop and soot particle accumulation.ACT design filter can significantly reduce the pressure drop and improve the soot particle accumulation performance,thus prolong the DPF life.%运用AVL-FIRE软件建立柴油机微粒捕集器(DPF)三维模型,模拟柴油机微粒捕集器内部压降和微粒沉积特性.针对DPF不同排气流量、进口温度、微粒沉积量及分布类型,对DPF压降特性进行模拟,并着重研究非对称孔结构(ACT)和灰分沉积量及分布形式对DPF压降和微粒沉积特性的影响.结果表明:随着DPF排气流量、进口温度、微粒沉积量和灰分沉积量的增加,DPF的压降增大,且DPF压降变化与进口温度呈非线性关系;沿DPF轴线方向,微粒沉积量呈先减小后增大趋势;“逐渐减少”型微粒分布形式压降损失较小,且再生速率较快.灰分在壁面上的层状分布对DPF压降和微粒沉积影响较大;非对称孔结构有利于降低DPF压降和提高微粒沉积能力,从而延长DPF寿命.