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AN EXPERIMENTAL INVESTIGATION INTO NO2 ASSISTED PASSIVE OXIDATION WITH AND WITHOUT UREA DOSING AND ACTIVE REGENERATION OF PARTICULATE MATTER FOR A SCR CATALYST ON A DPF
Date of Award
Campus Access Master's Thesis
Master of Science in Mechanical Engineering (MS)
Administrative Home Department
Department of Mechanical Engineering-Engineering Mechanics
Committee Member 1
In this study, the combination of a DPF and SCR catalyst technology together on a single substrate was investigated for both loading and oxidation performance. Johnson Matthey together with Corning have developed the latest in diesel aftertreatment technologies with the SCRF®. To test the steady state oxidation performance of the pre-production system, a series of fourteen NO2 assisted passive oxidation (PO) tests (seven with urea injection, and seven without) and four active regeneration tests were performed on a 2013 Cummins ISB engine. The aftertreatment production system was modified to allow for experimental investigation into passive oxidation with and without urea dosing and active regeneration of particulate matter for a SCR on a DPF. The primary focus of this study was to carry out passive oxidation (with and without urea dosing), active regeneration and to measure species concentrations, PM mass retained, flowrates, substrate temperature distributions, pressure drop across the filter, and to determine the PM oxidation performance of the SCRF® and compare it to the baseline system. The data from this study will be used in the development and calibration of the MTU SCR-F model.
The passive oxidation performance of the SCRF® was experimentally studied by oxidizing the accumulated PM at five distinct engine and exhaust conditions. These conditions were intended to span a wide range of standard space velocities (10.3-38.2 k/hr), substrate temperatures (273-377°C), and NO2 concentrations (117-821 ppm). The tests were repeated, once with and once without the injection of urea in the form of diesel exhaust fluid. Urea dosing was performed at a target ammonia to NOX ratio of 1.0 to investigate both the NOX reduction performance, as well as the effect it has on the PM passive oxidation performance. Each test began with an accelerated loading stage designed to accumulate 1.7±0.4 g/L. The two loading stages and the two post oxidation stages were intended not only to accumulate particulate matter for the passive oxidation stage, but also to characterize the difference to the production system.
The study found that the SCRF® was able to achieve 88-99% reduction in NOX with urea for the steady state PO conditions studied and there was 51% lower PM reaction rates, and 60% lower rate constants k, compared to without urea injection.
The thermal oxidation performance was studied by investigating three different active regeneration tests points above 500°C where the contribution of NO2 assisted oxidation was less than 10% based on other studies. The different target inlet temperatures 500°C, 550°C and 600°C were achieved through in cylinder post fuel dosing.
From the conclusions of the study, it was found that the PM loading performance of the SCRF® was very similar to the production CPF, but resulted in a higher pressure drop across the filter. The PM passive oxidation performance of the system was significantly affected (51% lower reaction rates and 60% lower rate constants) by the injection of urea during the passive oxidation stage. The kinetics of PM passive oxidation using the standard Arrhenius model resulted in an activation energy of 99.2 kJ/gmol and pre exponential factor of 113.7 1/ppm/s without urea injection. Likewise, the kinetics of PM passive oxidation with urea dosing had an activation energy of 96.2 kJ/gmol and pre exponential factor of 23.1 1/ppm/s. Finally the kinetics of thermal oxidation were found to have an activation energy of 211.5 kJ/gmol and 2.52E+05 1/ppm/s for the pre exponential factor.
Gustafson, Erik, "AN EXPERIMENTAL INVESTIGATION INTO NO2 ASSISTED PASSIVE OXIDATION WITH AND WITHOUT UREA DOSING AND ACTIVE REGENERATION OF PARTICULATE MATTER FOR A SCR CATALYST ON A DPF", Campus Access Master's Thesis, Michigan Technological University, 2016.