Date of Award

Spring 2020

Document Type

Open Access Dissertation

Department

Mechanical Engineering

First Advisor

Tanvir I. Farouk

Abstract

The primary objective of this thesis work is focused on the chemical kinetic modeling of the formation of Oxides of Nitrogen (collectively termed as NOx), regarded as a major pollutant emitted by combustion devices, and the application of that model to simulate transport coupled multidimensional distribution of NOx in a reacting flow. The underlying motivation of this kinetic modeling is the noted discrepancies among the existing models, which become critical in selecting the correct model in advanced gas turbine and engine research. The first part of this work is the performance evaluation and comparison of the existing models. Based on their performances, an updated kinetic model is proposed to predict NOx emission during syngas combustion. The proposed model performs reasonably well against global as well as detailed validation targets over a wide range of temperature, pressure and fuel loading. The second part is the extension of the kinetic modeling to simulate NOx formation during natural gas combustion. This extension is focused to predict emission characteristics during natural gas combustion in gas turbines and engines. In addition to the available literature data, the performance of the extended chemical kinetic model is also tested against new experimental measurements on flow reactors, provided by one of our collaborators.

The third part of this work evaluates the performance of the proposed chemical kinetic model to predict multi-dimensional experiments. A pressure based finite volume code under OpenFOAM platform is utilized to simulate the experiments involving McKenna burner driven flow reactor configuration. The model is capable to capture the flat flame and post flame structure. The predictions identify an oscillatory pattern of the reacting flow inside the flow tube, dictated by the constantly evolving recirculation zone, originated from the back-flow dilutions.

A methodology is proposed to minimize NOx emission by the application of external electric field. The final part of this work reports simulation results on the influence of DC driven radial electric field on the emission characteristics of NOx and CO for premixed CH4/air jet flame. The simulations are conducted over a range of equivalence ratio and jet flow rate for a configuration representative of a test-scale experimental setup. Over the entire range of flowrate conditions, both the stoichiometric and rich fuel-oxidizer mixture showed a decrease in maximum NOx in presence of electric field. For CO emissions, the presence of electric field reduces the concentration under fuel rich conditions and vice versa for stoichiometric flame. Another feature of this modeling work is the utilization of both homogeneous and transport-dependent experimental validation targets. The performance of the model shows reasonably well against various experimental venues.

Available for download on Sunday, November 08, 2020

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