Research On Flow Field,regeneration Characteristics And Key Influencing Factors Of Silicon Carbide DPF In Diesel Engine

With the extensive application of engines in engineering and machinery,it has led to an increase in emissions.At present,the purification in the machine can no longer meet the requirements of the regulations.The combination of the Diesel Oxidation Catalyst(DOC)and the particulate trap(Diesel Particulate Filter,DPF)can not only greatly reduce the emission of particulate matter,but also reduce HC and CO of emissions.In this paper,experimental and numerical simulation methods are used to study the factors affecting the flow and heat transfer characteristics of DOC+DPF and the regeneration characteristics of DPF.Based on a DOC+DPF package structure,three optimization schemes for different diversion devices were designed,and the simulation of the flow and heat transfer characteristics was carried out.The results show that:(1)The greater the aperture ratio of the flow guiding device of the packaging structure,the better the internal flow uniformity.The DOC front-end speed uniformity index and DPF pressure drop of the optimal solution are 96.7% and 2.17 k Pa,respectively;(2)Simulation of the thermal stress of the package structure with or without a flow guide device found that the areas with larger stresses are inlet and outlet At the transition position of the air cavity and the carrier,the maximum stress value of the two schemes is 94 MPa,and the stress in the transition region of the carrier is significantly reduced after the installation of the flow guiding device,and the maximum stress value is 84 MPa.Based on the diesel engine equipped with DOC+DPF post-treatment test bench,the DPF injection ignition regeneration test with and without flow guide device and the DPF fuel injection assisted combustion regeneration test with flow guide device were carried out.The results showed that:(1)The DPF carrier of the flow device has a higher regeneration temperature in the center than other regions.The maximum regeneration temperature reaches 1239℃ and the maximum temperature rise rate reaches 73.9°C/s.After optimizing the fuel injection strategy and installing the flow guide device,the maximum temperature is significantly reduced,the maximum temperature is 845℃,and the maximum temperature rise rate is 14.9℃/s;Oil ignition regeneration temperature characteristics,the results show that the internal temperature trend of the carrier of the two regeneration methods is consistent,and the positions of the front section,middle section,and rear section increase along the same axial direction of the carrier,and sequentially decrease in the same radial direction.The temperature rise rate of fuel injection assisted combustion mode regeneration is lower than that of fuel injection ignition mode,and the overall temperature uniformity is better.The numerical simulation results of the structural parameters on the regeneration characteristics of DPF show that:(1)When the carbon load is 8g/L,the maximum regeneration temperature increases and the regeneration rate increases with the increase of the carrier wall thickness,mesh number,and outlet aperture ratio;(2)The pressure drop of the carrier increases with the increase of the wall thickness,and decreases with the increase of the mesh number and the inlet and outlet aperture ratio.The numerical simulation results of soot deposition on DPF regeneration characteristics show that:(1)When the amount of soot is 8g/L,the "uniformly distributed" soot regeneration temperature has the highest value and the highest carrier pressure drop,and the regeneration rate is the fastest.The "linear increase" type distribution of carbon smoke has the fastest temperature rise rate in the initial period of regeneration,and the lowest carrier pressure drop and regeneration rate.The numerical simulation results of ash deposition on DPF regeneration characteristics show that:(1)When the amount of soot is 8g/L and the ash distribution coefficient is 1,the pressure drop and maximum temperature of the carrier increase with the increase of ash content,soot regeneration rate Increased with the increase of ash content;(2)When the amount of soot is 8g/L and the amount of ash deposition is 40g/L,with the increase of ash permeability coefficient,the maximum temperature of DPF regeneration,regeneration pressure drop,soot regeneration rate Both are lower;(3)When the amount of soot is 8g/L and the amount of ash deposition is 40g/L,as the ash distribution coefficient increases,the regeneration pressure drop of DPF carrier and the maximum temperature of regeneration decrease,soot regeneration rate increases,Should reduce the deposition of ash at the end of the tunnel.