Numerical Simulation Study Of The Diesel WF-DPF And Urea-SCR Performance

With the serious regional air pollution, the emission regulations become stricter in our country, to need combine the internal purification technology with the external purification technology to reduce the vehicle exhaust pollutant. Compared with gasoline vehicles, the PM and NOX emissions of diesel vehicles are more serious, usually diesel PM emission is about 30 ~ 80 times as much as gasoline, especially in- use diesel vehicle, which will have more pollutant emissions and more need to governance. This paper bases on GT-Power to simulation study the performance of Wall Flow Diesel Particulate Filter(WF-DPF) and Urea Selective catalyst reduction(Urea-SCR), to analysis the influence trend of each structure parameter or influence factors to filtration and regeneration performance of WF-DPF and reduction performance of Urea-SCR; and to obtain the main conditions affecting its performance by the orthogonal experiment method. The conclusion can be applied for specific optimizing performance of existing WF-DPF or Urea-SCR, and has a guiding significance for the modification of the in- use vehicle. The paper ’s main conclusions are as follows:(1) The indexes of evaluating WF-DPF filtration performance are initial filtration efficiency and the pressure drop. In a fixed parameter range, when optimizing the initial filtration efficiency, the mainly consider way are increasing filter diameter, filter wall thickness and porosity, reducing the pore diameter at the same time. when optimizing the pressure drop, the mainly consider way are reducing the density of channel, filter wall thickness and porosity, increasing filter diameter at the same time. The better project of filter performance of WF-DPF in this simulation experiment are, the filter length is 300 mm, the filter diameter is 350 mm, the density of channelis 150 CPSI, filter wall thickness is 0.3mm, pore diameter is 0.015 mm, porosity is 0.6, then the initial filtration efficiency of WF-DPF is 99.7%, the pressure drop is 1.452 kPa.(2) The indexes of evaluating WF-DPF regeneration performance are the largest peak temperature of the wall and regeneration time when regeneration efficiency reaches 90%. In a fixed parameter range, when optimizing the largest peak temperature of the wall, the mainly consider way are reducing the PM density of initial deposition and exhaust temperature. when optimizing regeneration time, the mainly consider way are increasing exhaust temperature and volume flow rate of the exhaust. The better project of regeneration performance of WF-DPF in this simulation experiment are, the PM density of initial deposition is 1g/L, volume flow rate of the exhaust is 210L/s, exhaust oxygen concentration is 16%, exhaust temperature is 450℃, then the largest peak temperature of the wall of WF-DPF is 454.6℃, the regeneration time when regeneration efficiency reaches 90% is 175 s.(3) The indexes of evaluating Urea-SCR reduction performance are the NO_x reduction efficiency and the NH3 concentration at the outlet. In a fixed parameter range, when optimizing the NO_x reduction efficiency, the mainly consider way are increasing NO2/NO_x(no higher than o.5) and NH3/NO_x. when optimizing the NH3 concentration at the outlet, the mainly consider way are reducing exhaust temperature and increasing NO2/NO_x. The better project of Urea-SCR performance in this simulation experiment are, NH3/NO_x is 1.0, NO2/NO_x is 0.5, exhaust temperature is 250℃, exhaust oxygen concentration is 2%, then the NO_x reduction efficiency is 93.9%, the NH3 concentration at the outlet. is 0.85 ppm.