Gregory Belk

Date of Award

Spring 2020

Document Type

Open Access Thesis


Mechanical Engineering

First Advisor

Tanvir I. Farouk


The objective of this project was to design, build, and test a plasma reactor capable of operating in the supercritical conditions. The reactor allows for the initiation of a plasma discharge in different fluids driven by a direct current (DC) power supply operating either in steady state mode or pulsing mode. The reactor was specifically designed for igniting plasmas within supercritical carbon dioxide, which has a pressure of 72.9 atm and 31.1 degrees Celsius.

A series of runs were conducted for varying pressures and inter-electrode separation, which allowed testing the operation regimes of the reactors. Finally, plasma experiments were conducted under supercritical carbon dioxide. Several diagnostics were performed which included high speed image acquisition, voltage-current characterization, as Schlieren imaging. Measurements indicated the presence of severe parasitic capacitance in the power circuit, which resulted in significant ringing and oscillatory patterns in the current signals. The Schlieren images showed the formation of density/pressure waves forming between the electrodes. Unexpected events such as electromagnetic pulses, sharp gradients and rise in discharge currents, spectral line broadening, electrode degradation, and discharge driven shockwaves in liquid were observed. Some of these observations will help in guiding the way to design and build an improved supercritical reactor that can mitigate some of these negative or unwanted effects.