Research On The Trap Characteristics Of Gasoline Particulate Filters

The mixture gas of gasoline direct injection engines is formed in a similar way asdiesel engines, they are both inject fuel into the combustion chambers to form themixture gas. This feature determines the presence of a relatively large number ofparticles in the GDI engines’exhaust.As an effective wayto deal with engines’exhaustparticulates, particulate filters can effectively control the vehicles’particulate emission.This paper mainly studied the trap characteristics of gasoline engine particulate filtersand three-way catalysts, and analyzed factors that influence the capture efficiency ofparticles. According to experiment results, optimization of the GPF parameters wasdone by using GT-POWER. Meanwhile the simulation study of how the carrierparameters and entry conditions vehicle infect the particles’trap process.There got the conclusion during the pressure drop characteristics experiment that: thepressure drop increase with linear trend along with the exhaust flow rate both beforeand after the particles were loaded.When the exhaust flow is less than60g/s, the GPF’spressure drop was small no matter the particles were loaded or not. But with the exhaustgas flow rate increases, the GPF’s pressure drop was significantly greater when theparticles were loaded in the carrier.The particle size distribution of different work conditions was obtained from theparticulate emissions’ characteristic test. The experimental results show that, theparticle number concentration is larger at low speed and small load condition, especiallyfor the nuclei mode particles. But its mass concentration is relatively small. As theengine’s speed and load increases, particle mass concentration has a tendency to rise.And it also found that the concentration of nuclei mode particles has a strong correlationwith the amount of HC emission. Besides, particle concentration increased when theengine running at a full load.The trap efficiency of the GPF and TWC during different working conditions wasgot through the particulate trap efficiency experiment. The results showed that, theTWC always had high processing efficiency on the particle number concentration (especially nuclei mode particles) when the engine was running at low speed and smallload. But the processing efficiency decreased obviously with the increase of speed andload. However the GPF had relative high trap efficiency for particle emission over allworking condition. And it also had the problem that the trap efficiency will decrease asthe speed and load increased, but it was not that much obvious as the TWC. The mainreason is that the increasing airspeed leads to the increased particles inertial, and thebrown diffusion trapping effect weakened relatively. And it leaded to lower trapefficiency. By contrast with the TWC, the GPF had relatively stable trap efficiency bothwith the accumulation mode particles and nuclei mode particles, meanwhile the three-way catalysts usually had low processing efficiency on the accumulation mode particles.The result showed that the GPF had relative high pressure drop when the enginerunning at full load. Therefore, this article used the GT-POWER to build a model ofgasoline particulate filter, and the carrier’s parameters were optimized by using theorthogonal analysis. The optimized carrier has high particle trap efficiency and lowback pressure. Meanwhile, the study of how the porosity, wall thickness, average porediameter, exhaust gas temperature and flow rate effect the capture process was done.And it is helpful for the understanding of particles’trap process.