Performance Simulation And Influencing Factors Of Diesel Particulate Traps

With emission regulations getting more and more stringent,it is urgent to control emissions of diesel engines.However,Chinese emissions standard(IV)cannot be met only by interior purification,so engine-out purification technology is needed.Nowadays,it is the most effective and convenient way of reducing PM in exhaust to collect soot particulates by DPF.In the spreading and industrialization of DPF,it is key to the research to improve its capture performance and regeneration efficiency.In this paper,capture performance and regeneration efficiency of DPF was investigated and its parameters of structure and regeneration were optimized.In addition,effect of DPF devices on power performance and fuel economy of the diesel engine was analyzed.(1)According to standard of QC/T829-2010"Test method for diesel exhaust aftertreatment device";rational experiment scheme was proposed and regeneration process of DPF in diesel engine was investigated.Results show that in regeneration experiment of DPF supported by DOC,with the increase of exhaust temperature,PM starts to burn.Average temperature of carrier wall increases from 300 ℃ to 730 ℃along the axis from inlet to outlet.Pressure loss of the carrier first increases then decreases.In the meantime,conversion efficiency of co、THC by DOC reaches over 90%.(2)Based on experiments on test-beds,simulation model of DPF was established using GT-power software.Processes of capturing and regeneration were studied.And effect of structural parameters of DPF on capture performance were investigated.Results show that,when porosity of the DPF increases,its Pressure loss and capture efficiency go up.When porosity increases from 0.34 to 0.66,pressure loss of DPF increases from 2.3kPa to 5.8kPa.Pore size cannot directly affect pressure loss of DPF,but it has significant effect on initial capture efficiency.When pore size increases from 0.012mm to 0.024mm,initial capture efficiency of DPF falls from 99%to 86%.When the wall thickness of carrier increases from 0.2mm to 0.4mm,pressure loss of carrier increases from 2.8kPa to 6.5kPa.Meanwhile,initial capture efficiency of the carrier increases.When channel length or wall permeability of the carrier increases,pressure loss of DPF decreases but both capture efficiencies remains almost the same.(3)Three key parameters in regeneration process of DPF,initial soot load,oxygen content in exhaust and temperature rising rate are studied.Results show that When initial soot load rises from 3g/L to 11g/L,pressure loss of carrier goes up from 3.2kPa to 12.8kPa.Also,maximum temperature of wall of carrier rises from 610 ℃C to 900℃.Therefore,when there is more initial soot loads,pressure loss in regeneration process of DPF gets higher.Oxygen content in exhaust should be over 7%in order to guanrantee the stable combustion of soot.Rational temperature rise rate contributes to reliable regeneration of DPF.(4)Based on a 1-D model of D19 diesel engine established using GT-Power,effect of after-treatments on engines were investigated from power,torque,cylinder pressure,fuel consumption rate.Results show that,after installing DPF,exhaust back pressure increases.Power output and torque decrease.In-cylinder peak pressure decreases.Fuel consumption rate goes up.Also,this trend becomes more evident with the increase of soot in carrier.When soot load in DPF reaches 10g/L,power and torque of D19 engine tends to decrease significantly.Largest drop could reach about 4%,meanwhile fuel consumption goes up steeply.Therefore,it will improve power and economy performance of the diesel engine to choose appropriate regeneration time and to decrease exhaust back pressure.