Study On Mechanisms Of Ash Deposition And Its Effect On DPF Performance

Wall Flow Diesel Particulate Filter(DPF)is the most internationally accepted diesel exhaust particulate control technology in the world.The technology has been widely used at home and abroad.For particulate filters,the ultra-low particulate emission limits require that filters be able to efficiently capture the particulate matter and safely and reliably regenerate.In the process of capture and regeneration,however,incombustible ash will be deposited inside the filter.It will not only influence the pressure drop performance of DPF and reduce the available space of DPF,but also affect the choice of active regeneration timing increase the regeneration frequency per unit period,which influences the fuel economy.At the same time,ash deposition in DPF is also a key factor in determining its service life.From this point of view,this study plays a practical significance and may lay a solid foundation for the development of reasonable regeneration strategy.Based on the GT-POWER software,a mathematical model of DPF particulate trapping and continuous regeneration with ash deposition was established.Then,the key parameters in the mathematical model were calibrated in combination with experimental study.On the basis of model simulation,the influence of ash deposition on the soot loading and continuous regeneration of soot in DPF inlet channel was explored.The main contents of this paper are as follows:1.With the help of the GT-POWER software,a mathematical model of particle trapping based on the “unit collector” filtration theory was established;a mathematical model and a trapping efficiency calculation model of the soot layer and ash layer were established;a mathematical model of one-dimensional flow field including mass conservation,momentum conservation,energy conservation and pressure drop calculation was established.2.The DPF rapid aging test bench was established to study the pressure drop characteristics of clean DPF and the pressure drop characteristics of soot loading under different loading conditions.The pressure drop characteristics of CJ-4 oil ash loading process were studied by adding oil to diesel-a method of the DPF rapid aging.Combined with the experimental data,the parameters of the substrate wall,the soot cake layer and the ash cake layer were calibrated in the simulation model,and the accuracy of the model was verified.3.Combined with the calibrated model,simulation study was carried out on the variation of soot loading pressure drop and the thickness of the soot layer with different ash cake layer loading.The effects of different ash end plug loading on the pressure drop and the thickness of the soot were studied under the same ash loading mass.It can be seen from the study that controlling ash deposits more at the end of the channel is beneficial to reducing DPF pressure drop.4.In combination with the mechanism of continuous regeneration of CDPF,two factors that affect the rate of continuous regeneration of ash are proposed: the inactivation by catalyst surface coverage and the inhibition of reverse diffusion of NO2.On the basis of the simulation model,a calculation study on CDPF regeneration rate changes with different ash cake layer deposition.From this study,it shows that the deposition of ash will decrease the continuous regeneration rate of the catalytic particulate filter.