Study On The Performance And Regeneration Control Strategies Of4D83Car’s DPF

Particulate Matte（rPM）is one of major pollutants of diesel engine exhaust emissions.With the increasingly strict emission regulations, diesel engine must carry thepost-processing system can meet the requirements of emission regulations in thefuture. Accumulated particles in the DPF carrier will increase the resistance ofexhausting and the process on the same time have the adverse influences on thedynamic property and economy of engine. So we need regenerate DPF regularlly andeliminate the particles on the carrier. In conclusion, we need to carry out DPFregeneration regularly to eliminate the PM in substrate.Based on the national "863project" common rail diesel engine development", webuilt the engine test bench, and built the1D and3D model of DPF. The DPF workingperformance and regeneration control strategy are studied based on simulation andexperimental methods. In this paper, the research content includes four parts: DPFcollection efficiency, pressure drop characteristics, theory analysis and mathematicalmodeling of DPF regeneration process; Flow uniformity analysis in DPF; Simulationanalysis of collection efficiency and pressure drop characteristics; Experimental studyand development on DPF regeneration control strategy.In this paper, the DPF collection efficiency and pressure drop characteristics arestudied based on DPF visualization experiments. Clarify the three stages of PMloading and the DPF pressure drop procedure; The changing process of PM and thepressure drop in the DPF regeneration process are described in detail. Based on theparticle capture theory and Darcy’s law, the collection efficiency and pressure dropmathematical model are set up; DPF regeneration process of mathematical model is set up based on mass, energy and chemical dynamics balance equation. These studiesprovide a theoretical basis to collection efficiency and pressure drop characteristicsanalysis and the analysis of the regenerative process.AVL Fire software is used to establish3D DPF simulation model, and introduceuniformity coefficient equation to analysis the flow uniformity in DPF. The influenceof entrance expansion tube cone Angle, length-width ratio of substrate; exist of theDOC in front of the DPF and steady-state engine conditions to flow uniformity arestudied through simulation calculation. The flow uniformity is better when expansiontube cone angle is smaller, substrate length-width is close to1. Exist of the DOC infront of the DPF has an effect of dispersion on exhaust gas flow uniformity. Theexhaust flow rate and temperature of Engine steady working condition have almost noeffect to flow uniformity.GT-Power software is used to establish a DPF one-dimensional simulation model andthe DPF collection efficiency and pressure drop characteristics are studied. First, pressdrop model of fresh DPF is calibrated and get the result of wall permeabilityk0=9.4e-14。 Through the simulation analysis, illustrating the DPF collectionefficiency and changing the pressure drop along with PM loading process, and thecontribution of substrate wall and PM layer to them. Then the effect of inlet cells,porosity, pore diameter, wall thickness, initial particle loading on the collectionefficiency and pressure drop characteristics are studied and the reasonable range ofthe various factors are obtained. The above two parts of simulation analysis laid thefoundation for optimal design of DPF, provides technical reserves of developinghigher performance of DPF.Built engine test bench and complete after treatment system control strategy relatedexperiments. By the DOC light-off temperature and DPF balance temperatureexperiments and get DOC to HC transformation temperature T90=330℃, DPFbalance temperature is375℃. Then influence of supercharging pressure, maininjection timing, EGR rate and fuel after injection to the exhaust temperatureexperiments, DOC temperature rising characteristic experiment, PM loading andregeneration characteristics research are studied. And based on this, the DPF regeneration strategy is studied and developed, it contains3parts: DPF regenerationtiming, temperature rising strategy and DPF regeneration process control."Multi-level regeneration time determination" is put forward in this paper, and thenrealizing the coupling of PM mathematical model, fuel consumption and the pressuredrop method, enhancing the accuracy of regeneration time controlling.“All conditionsregional regeneration” is put forward, dividing the engine conditions into differentareas based on the vehicle’s running conditions. Take different temperature risingmethods for different condition areas, to make the exhaust temperature of mostworking conditions reach the requirements of the DPF regeneration. From excessexothermic at the start of regeneration， Temperature spike when “runawayregeneration”happens and Uneven temperature distribution during regeneration, howto control the temperature and oxygen of regeneration process to realize theregeneration process control is analyzed. Analysis the question of engine conditionsuddenly dropped to idle in regeneration process,Especially the analysis to the problem when engine suddenly dropped to idle inregeneration process, put forward by adjusting the EGR rate, engine speed and inletthrottling methods to complete controlling of the DPF regeneration process. Byimproving the uniformity of the airflow movement, We can improve the uniformity oftemperature and particle loading in DPF. Thus uneven temperature distribution duringregeneration can be avoided.