An Experimental Investigation into the Effect of NO2 and Temperature on the Passive Oxidation and Active Regeneration of Particulate Matter in a Diesel Particulate Filter

Abstract

The kinetics of particulate matter (PM) oxidation in a catalyzed particulate filter (CPF) under different exhaust temperature and NO2 conditions is presented along with a literature review of the related PM kinetic studies. The study was conducted with a 2013 heavy-duty engine that had NO2 levels significantly higher than engines that met the earlier 2007/2010 EPA standards, and the results show a significant increase in PM oxidation rate that is possible under normal vehicle operating conditions, to diminish the need to actively regenerate the DPF. The detailed procedure for determining the PM oxidized during the experiments is described. Two types of tests were conducted to determine the NO2 assisted as well as the thermal oxidation kinetics. Passive Oxidation (PO) tests were conducted for selected engine conditions that would cover the range of exhaust NO2 concentrations (137 to 1013 ppm tested) and temperatures (299 to 388 °C tested) during regular engine operation. Active regeneration (AR) tests were conducted to determine the thermal oxidation kinetics at exhaust temperatures from 498 to 575 °C which was induced by post fueling. The CPF was first loaded with PM to a target loading, and then the PM was oxidized under specific exhaust temperature and NO2/O2 concentration conditions. The data obtained in this study can also be used to calibrate a CPF model. The activation energies and pre-exponential factors for NO2 assisted and thermal oxidation were developed from the PO and AR data. It was also found that PM reactivity during PM loading was greater than for the passive oxidation tests.