Study On Soot Load Estimation Of DPF Based On Pressure Drop And Temperature Between Inlet And Outlet Sides

As China's automobile production and ownership rapidly increase,the pollution of automobile exhaust to the atmosphere have become increasingly serious.Among them,particulates?PM?are one of the main pollutants of diesel engine exhaust,which can easily cause huge harm to air and human health.Diesel Particulate Filter?DPF?is one of the most effective technical methods to reduce diesel particulate emissions.When the PM deposited in the DPF reaches a certain amount,it needs to be regenerated.The key technology of the regeneration method is to accurately estimate the soot loading in the DPF.This paper built a DPF test system based on a diesel engine test bench.It consists of diesel engine,DPF,pressure drop and temperature measurement device,and data collection device.Based on the DPF pressure-drop composition,this paper established a DPF pressure-drop mathematical model,and fitted the functional relationship between soot loading and DPF wall permeability according to related studies.Meanwhile the simulink software was used to establish and verify the simulation program.The results showed that the maximum average relative error between the calculated value and the tested value was 9.3%within the test range,and it accurately reflected the stage changes in the DPF capture process.Through the bench test,the axial temperature distribution of the steady-state and transient conditions was investigated.The results showed that there was no significant difference in the temperature of the DPF inlet and outlet under steady-state conditions.The temperature of the DPF inlet and outlet had a significant delay under transient conditions,and the maximum delay time reached 33 s.According to the heat transfer mode between the gas and the carrier,a DPF temperature model was established,and a solution formula for the temperature of the DPF channel gas and the carrier was obtained.Finally the simulink software was used to establish the DPF temperature control model.The maximum relative error under steady state conditions was 4.9%and the maximum relative error under transient conditions was 4.8%.The effects of exhaust flow,the DPF channels per square inch?CPSI?,the DPF length,and the soot loading on the axial temperature were explored.The results showed that increasing the exhaust flow,the delay time t_max and the axial temperature gradient decreased,meanwhile the rate of decline decreased.Increasing the carrier CPSI,t_max and axial temperature gradient both decreased linearly.Increasing the carrier length,t_max increased linearly,the axial temperature gradient decreases and the rate of decline decreased.When the diesel engine operating conditions and DPF size specifications were determined,the peak value of the DPF axial temperature difference and the integral of the temperature difference curve increased linearly with the increase of the sooting loading,but the linear relationship under different operating conditions was not the same.A cooperative estimation model of DPF soot loading was established,and the estimation of DPF soot loading was analyzed through three groups of heating working condition.The results showed that the soot loading curve calculated by the pressure-drop method under steady-state conditions remained stable after the rise process,and it very closed to the actual value.Under transient conditions,a peak appears in the soot loading curve,and the calculated value drifted greatly away from the actual value.The soot loading curve obtained from the temperature method remained unchanged under steady state conditions.During the transient conditions,the soot loading curve rose rapidly and remained stable near the actual value.The cooperative estimation model could effectively combine the advantages of the pressure-drop and temperature methods,eliminated the data drift of the pressure-drop estimation model,and quickly calculated the soot loading,limited the calibration range to specific conditions.By comparing the data errors obtained from the three estimation models,it was found that the cooperative calculation method maintains the lowest relative error regardless of the operating conditions.When the soot loading was 1 g/L,working condition was switched from 600 r/min,0 N·m to 1382 r/min,1361 N·m,the maximum relative error of the pressure-drop method was 37.5%,the temperature method was 14.2%and cooperative method was 10%,showing a higher accuracy.