Numerical Study On Ash Deposition Characteristics Of Spherical Filter In Diesel Particulate Filter

Because of its excellent power and fuel economy,diesel engine has been widely used in road vehicles,construction machinery,Marine power and other fields.However,due to the ignition mode of compression combustion and the characteristics of diesel fuel,the particulate matter in its exhaust emissions has caused great pollution and threat to the atmospheric environment and human respiratory tract health.At present,Diesel Particular Filter(DPF)is mandatory to be installed in national sixth standard to reduce particulate matter pollution.However,the accumulated soot and ash deposition on the filter surface will affect the capture and flow performance,and then affect the engine power and economy.The deposited soot can be treated by regeneration,but there is no simple and efficient cleaning method for non-oxidized ash components.This paper aims to design a rotary spherical DPF filter with self-cleaning function.Through the design of structure and control strategy,a new idea is provided for the cleaning of DPF ash.By understanding the flow characteristics and deposition of ash particles in the pore of DPF filter body,it lays a foundation for the subsequent design,development and optimization of DPF structure.The main work of this paper is as follows:(1)The spherical DPF filter and other accessories are designed by three-dimensional modeling.Through the overall 180° rotation,the inlet and outlet direction is changed,so that the exhaust air becomes the energy source for cleaning the ash material in the DPF channel.The relevant control system and strategy are designed.Based on GT-Power,a 6-cylinder diesel engine model and a DPF model with ash loading function were built,and the engine model was calibrated by bench test.The exhaust terminal data is used as the initial boundary conditions for subsequent research.(2)Secondly,the influence of inlet and outlet channel width and porosity on DPF average pressure drop and ash plug length was studied.Multi-factor correlation analysis was carried out by response surface model fitting.The results show that the overall pressure drop of the asymmetric orifice is smaller than that of the symmetric orifice of the original scheme.The design of the spherical DPF filter orifice as the asymmetric orifice is beneficial to enhance its exhaust flow.The three influencing factors were optimized by NSGA-Ⅱ,and two structural optimization schemes were obtained.Compared with the original scheme,the average pressure drop decreased by 48.8%and 49.1%respectively.Ash plug length was reduced by 54.4%and 34.6%.(3)DPM Discrete Phase Model was used for gas-solid two-phase flow.The flow path and trapping and deposition characteristics of particulate matter in DPF channels were studied,and the fluid domain model of DPF channels was constructed and meshing was carried out.In the comparison of structural forms,the acceleration effect of asymmetric channels on exhaust velocity is more obvious,the static pressure is higher than that of symmetrical channels,and the pressure drop rate is slower.Under the same incident particle mass flow rate,the ash accumulation rate in asymmetric channels is faster and the ash collection rate is more uniform on the wall surface.On the basis of studying the deposition distribution of particulate matter,this paper built a test verification platform and ash fast loading device suitable for the reverse blowing of particulate catcher.By setting different exhaust flow rates and loading ash components,it explored the removal efficiency of ash retained in DPF orifice after changing the inlet and outlet directions.The test results show that the maximum ash reverse blowing efficiency is 90%,and the minimum reverse blowing efficiency is over 70%.Under the conditions of ash loading of 12g and exhaust flow of 400kg/h,the maximum ash removal efficiency can reach 93%,and reverse blowing can be realized and the efficiency is in line with expectations.