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

In this study the oxidation of particulate matter (PM) retained in a catalyzed particulate filter (CPF) is investigated to understand the kinetics of PM oxidation. Seven passive oxidation and four active regeneration experiments were performed on a Cummins ISB 2013 280 hp engine and the production aftertreatment system adapted to a lab setup, in order to study the NO2 assisted and thermal oxidation of the PM retained in the CPF. The CPF was loaded with PM produced by the engine and the PM was then oxidized in the CPF under various Passive Oxidation (PO) and Active Regeneration (AR) conditions. First, the engine was operated at an engine condition that produced PM at a greater rate than the production setting, in order to load the CPF to 3.0 ± 0.4 g/L in a suitable time of 6 hours. To study the NO2 assisted oxidation, exhaust at pre-determined engine conditions with low PM concentration (\u3c 5 mg/scm) and the required NO2 concentration and temperature was flowed through the CPF. During the PO testing, the exhaust temperature into the CPF varied from 299 – 385 °C, the NO2 concentration varied between 137 – 1013 ppm and the exhaust mass flowrate varied between 3.63 – 12.0 kg/min. Thermal oxidation was studied by operating the engine at a specific condition where the exhaust at the Diesel Oxidation Catalyst (DOC) inlet was at a higher temperature than the light-off temperature of hydrocarbon oxidation in the DOC (300 °C). Late combustion cycle fuel dosing was performed and the hydrocarbons in the dosed fuel were oxidized across the DOC. This created an exotherm and raised the exhaust temperature into the CPF to the required value between 498 – 575 °C to oxidize the PM retained in the CPF at the end of loading, by reaction with O2. The O2 concentration into the CPF varied between 8.17 to 9.03%. It was found that the NO2 assisted kinetics could be represented using the standard Arrhenius equation. The activation energy obtained using the standard Arrhenius model, is 94 kJ/gmol and the pre-exponential factor obtained is 25.5 1/ppm/s. The thermal oxidation reaction rate could be similarly represented using the O2 concentration and temperature over the range of conditions studied. The activation energy for thermal oxidation was found to be 136 kJ/gmol and the pre-exponential factor obtained is 3.56 1/ppm/s. It was found that for two of the passive oxidation tests, the reaction rates were higher than that predicted using the Arrhenius representation. The Loading Engine Condition also showed higher reaction kinetics than the NO2assisted kinetics. The engine and exhaust conditions as well as reaction rates obtained as part of this study are intended to be compared to the corresponding values obtained for a SCR-in-DPF substrate that is currently being studied at Michigan Tech as the next phase of study. The purpose of this comparison is to understand the difference in performance of both aftertreatment systems in light of their respective weights and volumes. The data obtained during this study is also being used to calibrate the 1-D CPF model at MTU. An introduction to the model is provided in this thesis, and the important variables of the study that are also used for model calibration are presented in the appropriate sections