Effect Of The Structural Parameters Of Diesel Particulate Filter On Trapping Characteristics Of Ultrafine Particles

With the development of society, the problem of environment pollutionbecomes more and more serious,"PM2.5" and "haze" has gradually becomethe focus of the society. As the important pollution source of urban air,the internal combustion engine emission is becoming more and moreattention. Compared with gasoline engine particulate emission, the dieselengine s is the dozens times more, therefore, within the scope of ourcountry and around the world have strict requirement for the dieselparticulate emission. As the emission regulations have becomeincreasingly restrictive, in recent years, the new combustion theory hasalso got the gradually development. Due to the volatile of the gasolinefuel is good and it is good for solving the premixed problems, currentresearch scholar have studied gasoline/diesel blended fuel on theinfluence of the engine combustion and emission. The diesel particulatefilter (DPF) is one of the important means of reducing particulateemission of diesel engine, the research for DPF on the trappingcharacteristics of particulate emission when using the blended fuel isof great significance.In this paper, I mainly studied the trapping characteristics of DPFfor diesel engine ultrafine particulates by using the means of simulationand experiment. Simulating and analyzing the two-phase flow in DPF, todiscuss the influence of the structure parameters and inlet boundary ofDPF on the flow uniformity. Meanwhile I study the trapping efficiency ofDPF on different modal particle under different conditions, differentboundary and burning the different added proportional gasoline/diesel blend fuel. The results show that:1) The internal DPF was simulated by ANSYS FLUENT. This paper mainlystudy the concentration distribution of particles with diameters of0.1μm and0.3μm in DPF. The results turn out that with decrease ofparticle diameter, the inertia of particles decrease accordingly. Whenthe particles are small enough, they can move according to Brownian motiontrajectory. Therefore, the homogeneity of concentration distribution ofparticles is fine.2) The paper studies the uniformity of air flow movement in DPF ondifferent wall permeability, inlet speed and divergence angle. The wallpermeability has no effect on the uniformity of air flow movement, whichonly influences its speed. Reducing intake air speed can improve theuniformity, but the airflow velocity is constrained by the load conditionof diesel engine, thus can t change. Reducing divergence angle canimprove the uniformity of particle concentration quickly. The DiscretePhase Model was also analyzed on particles movement in filtering channel.With DPF s axial position increase, airflow velocity is reduced in intakechannel, while increased in exhausted channel and reaches the highest inexit of DPF. The wall permeability velocity also rises gradually.3) DPF has relatively high filtration efficiency on different modeparticles. DPF has nucleation and acceleration mode through windows, whenthe diameters of exhausted particles are at the through windows, it caninfluence DPF s filtration efficiency, resulting in increasedproportion of particles between this particle size after DPF.4) For the same diameter particles, the DPF s filtration efficiencyis related to the engine s conditions. There exits optimal condition.The DPF s filtration efficiency is best under medium speed and mediumload conditions. The variation of speed has more effect on filtrationefficiency compared with load. With the injection timing advance, the proportions of the nucleation mode and ultrafine particles increaseaccordingly.5) For the fuels of different percentage of gasoline, compared withpure diesel, when use the blend fuel of30%percentage of gasoline, theproportion of nucleation mode particles below50nm before DPF decrease,but after DPF the proportion of nucleation mode particles rise. Theresults can be explained that the gasoline/diesel blend fuels can reducethe proportion of nucleation mode particles effectively. However, thediameters of most nucleation mode particles are at the through window ofDPF, which can result in the increase proportion of nucleation modeparticles after DPF. For ultrafine particles, the proportion of particledecrease slightly when compared with pure diesel. Therefore, DPF cancontrol the ultrafine particle emissions of gasoline/diesel blend fuels.