Optimization Of Dpf Structure Parameters And Analysis Of The Influence Factors Of Regeneration

Particulate Matter(PM)is one of the main pollutants produced by diesel engine.In order to reduce the pollution of PM to the environment,it is necessary to take measures to cut down the PM produced by diesel.At present,the widely used PM external post-processing technology is Diesel Particulate Filter(DPF).The structure of DPF has a great influence on the performance of itself and engine,and there is a coupling relationship between filtering structure parameters.Therefore,the establishment of a multi-objective optimization method is of important engineering significance to ensure the reliability and stability of the structure design of DPF.On the basis of previous studies,this paper calculates and analyzes the influence on the capture efficiency and pressure drop about the DPF of the DPF filter structure parameters(channel density(CPSI),the filter pore diameter,filtering wall thickness,porosity,and permeability)under different exhaust flow with Design of Experiments(DOE),and the structure parameters are optimized by multi-objective optimization method.The optimization results show that the optimized filter structure parameters can make the DPF capture efficiency more than 95%,and the pressure drop is reduced by 30%~50% before the optimization under the same conditions.The internal flow characteristics of DPF are numerically calculated based on the theory of porous media and computational fluid dynamics.The calculation results show that the smaller the expansion angle of DPF,the smaller the change in pressure drop,and the more uniform the gas flow in DPF,which is beneficial to the capture of the particles in the exhaust gas of DPF.The smaller the diameter ratio of the filter,the smaller the increase of the pressure drop of the gas through the filter,and the less influence of the long diameter ratio on the flow uniformity.In addition,the filter element structure symmetry of inlet channel and outlet channel will produce certain effect on the pressure drop: Compared with the pressure drop generated when the inlet and outlet passages have the same diameter,the pressure drop decreases by about 40% when the inlet passage diameter is smaller than the outlet passage diameter,and the pressure drop increases by about 20%~30% when the inlet passage diameter is larger than the outlet passage diameter.The back pressure of exhaust continue rising as the PM accumulates in the particle trap when the diesel engine is running.It will seriously affect the economy and power performance of the engine when the PM accumulates to a certain amount.Therefore,it is necessary to periodically remove the soot in the DPF,that is,DPF regeneration.For the DPF regeneration problem,this paper studies the influence law of exhaust flow,amount of carbon load,oxygen quality fraction in exhaust gas,and inlet exhaust gas temperature of DPF.The results show that it is beneficial to the energy saving under the heavy load conditions.The regeneration efficiency is the highest when the amount of soot load is around 10g/L.In addition,the oxygen mass fraction(0.07~0.10)of engine exhaust is suitable oxygen content range for the regeneration,which does not require additional oxygen supply to assist the regeneration.When the exhaust temperature entering DPF is around 500℃,it can achieve safe and efficient regeneration.