Date of Award

2019

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Gordon G. Parker

Advisor 2

John H. Johnson

Committee Member 1

Jeffrey D. Naber

Committee Member 2

Sunil S. Mehendale

Abstract

This research focuses on modeling and control of PM and NOx in diesel engine exhaust using an SCR catalyst on a Diesel Particulate Filter (SCR-F). A 2D SCR-F model was developed that is capable of predicting internal states: 2D temperature, PM and NH3storage distributions and filtration efficiency, pressure drop, PM mass retained in the PM cake and substrate wall and outlet NO, NO2and NH3concentrations. The SCR-F model was used to simulate a DOC + SCR-F + DOC + SCR ultra-low NOx system that can achieve > 99.5% NOx conversion efficiency.

The model was calibrated with experimental data from a Johnson Matthey SCRF® with a Cummins 2013 ISB engine. The impact of SCR reactions on passive PM oxidation rate and PM loading on SCR reactions was determined. A comparison of the experimental and model data for different ammonia to NOx ratios, PM loading, and passive oxidation conditions is presented. A 2D SCR-F state estimator was developed by combining a simplified version of the 2D SCR-F model with pressure drop, outlet thermocouple and NOx sensormeasurements using an Extended Kalman Filter. The temperature, PM mass retained and NH3coverage fraction states were predicted which can be used to develop fuel dosing and urea dosing strategies for the SCR-F.

A 2D SCR-F + 1D SCR system model was used to simulate the experimental data collected on a SCR-F + SCR system from a Cummins 2013 ISB engine. The NO2/NOxratioat the SCR-F and SCR inlet was found to be limiting factor for NOx conversion efficiency of this system. An ultra-low NOxsystem was developed with a DOC downstream of the SCR-F that maintains an optimum NO2/NOxratio of 0.5 at the downstream SCR inlet by using 2 urea injectors. This system was simulated with a combination of 1D DOC, 2D SCR-F, and 1D SCR models and it was found to be capable of > 99.5% NOxconversion efficiency, a 90% increase in PM oxidation rate compared to an SCR-F + SCR system with 1 injector for typical engine operating conditions.

Available for download on Friday, May 15, 2020

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