Plasma Assisted Ignition in a Three-dimensional Scramjet Combustor with a Photon-preserving Radiation Model

This thesis studies how plasmas created by nanosecond repetitive pulsed discharges (NRPD) can affect and improve the combustion characteristics in a high-speed fluid flow that simulates scramjet conditions. This is done by creating a computational code that incorporates the effects of plasmas, high-speed fluid dynamics, combustion chemistry, and photoionization. Many physical effects across multiple temporal and spatial scales appear, and creating a code that efficiently and accurately models these effects was the biggest contribution of this research. A new chemical mechanism has been created that incorporates high energy states for nitrogen and oxygen. This code was applied to examine how NRPD is affected by high-speed fluid flows and different electrode geometries. In quiescent simulations, the multiple pulses couple with each other increasing the overall temperature, which can lead to ignition due to the plasma added. When there is a freestream flow the convection of the previous pulses plasma can prevent coupling between the pulses. Without modification to pulse characteristics (increase in frequency, intensity, or length), combustion may not be achieved. Next, a more applied study of a three-dimensional scramjet is conducted to examine how the plasma affects the flow by the scramjet geometry and conditions. These larger simulations add effects from turbulence by implementing an LES-EDC model. These simulations show how plasmas generated by NRPD can affect the fluid flow inside a scramjet combustor cavity.