Establishment and application of MAP for regeneration back-pressure threshold value of diesel particulate filter

Abstract: In order to obtain the regeneration back-pressure threshold value of a diesel particulate filter (DPF) to provide the estimated criterion of regeneration time, the working principle of a burner-type DPF was introduced, and the estimated method of DPF exhaust back-pressure was put forward based on the total fuel consumption rate. A simulation model of a diesel engine with DPF was built by AVL-BOOST software. Through reasonable simplification, setting its parameters, and defining the boundary conditions, the working performances were simulated and DPF's back-pressure under the allowed total fuel consumption rate of different working conditions was calculated, then verified the simulation values of fuel consumption rate, power, torque, exhaust gas temperature and DPF's back-pressure on the DPF regeneration test bench. It shows that the results of the simulation are in close agreement with the experiments. Under diesel engine's full load working condition, the maximum error and the relative error of power was 3.9 kW and 7.83%, respectively, and that of fuel consumption rate was 12.3g/(kW.h) and 4.82%, and the error of DPF's back-pressure between the simulations and the experiments was less than 2.5kPa. Under the diesel engine's partial load working conditions, changes of power, fuel consumption rate, torque, exhaust gas temperature and DPF's back-pressure were consistent with those of full load working conditions, and likewise the simulation value agreed with the experimental data. It showed that the simulation model was valid and able to supply high density and precision measure values instead of the test bench. Based on the multivariate linear regression analysis theory, with the least square fitting method and piecewise linear interpolation technology along the vertical and horizontal direction distribution of the engine's working conditions, respectively, the values of fuel consumption rate were obtained under the diesel engine's all working conditions, and with the help of MATLAB software's powerful mathematics function and graph disposal capability, the curve surface of equal fuel consumption rate was simulated for the diesel engine with clean DPF. To set up the soot layer thickness with 0.0025mm increments in the DPF module of simulation and to record the fuel consumption rate of each working condition, the back-pressure was taken as the threshold value with the fuel consumption rate at 5% more than that of the diesel engine with clean DPF; further, the threshold value MAP of DPF regeneration back-pressure was built. From test results of the MAP application, it shows that DPF regeneration can be completed in 5-10 minutes. Through embedding three temperature measure probes in equal intervals along the axis of DPF's central inlet channels, real-time monitoring on temperature and its gradient were carried out on each measuring point. From the selected four regeneration cases, the peak value and maximum gradient of temperature was 1230, 1180, 1085, 1047K and 26.3, 24.6, 21.5, and 20 K/cm, respectively, which was below the safe threshold value. It indicated that the back-pressure threshold value MAP is very practical. It provides technology references on fast and safe regeneration for DPF.