Author ORCID Identifier

https://orcid.org/0009-0009-6122-2612

Semester

Summer

Date of Graduation

2024

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Fabien Goulay

Committee Co-Chair

Kenneth Showalter

Committee Member

Kenneth Showalter

Committee Member

Stephen Valentine

Committee Member

Mark Tinsley

Committee Member

V’yacheslav Akkerman

Abstract

The effect of externally applied DC electric fields on flame structure was investigated in a stationary atmospheric axisymmetric laminar H2–Air flame with less than 100 ppm carbon equivalent impurities. Flame OH chemiluminescence signals were recorded using a UV-sensitive CCD array as a function of voltage (+10 to -10 kV) applied to a stainless-steel ring electrode placed around the burner nozzle. Changes in chemiluminescence signal are reported as a function of electrode height above the burner, airflow, and fuel composition. Significant changes in OH* distributions were observed for voltages below -5 kV. Under optimum conditions, the height of the chemiluminescence flame decreases by up to 67% at the maximum applied voltage. The flame transitions from a teardrop shape to an open-tip flat flame at a voltage corresponding to an inflection point in the flame height–voltage profiles. The voltage of the inflection point depends on both the electrode height above the burner and the airflow rate. Increasing the air flow rate shifts the inflection point to more negative values, until almost suppressing the effect of the electric field on the flame structure. The effect of carbon impurities was investigated by adding controlled amounts of ethylene to the fuel line. The experimental data provides a dataset collected under well-controlled conditions for the understanding of the effect of electric fields on a simplified combustion system. Numerical studies have been conducted using existing mechanisms to visualize the H3O+ ion profiles in H2–O2 flames with added C2H4 impurities ranging from 0 to 4000 ppm. The model data shows that H3O+ number density reaches a saturation value of ~4 ×106 ions cm-3 in the brut gas regain of zero impurity H2–O2 flame. Overall, the H3O+ number density in the reaction zone increases by a factor of 450 from 0 to 250 ppm and by a factor of 5 from 250 to 2000 ppm. One of the main findings was that hydrocarbon impurities as low as 10 ppm may generate sufficient charge carriers to observe changes in H2−Air flame properties under externally applied electric fields.

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