Plasma Assisted Ignition in a Three-dimensional Scramjet Combustor with a Photon-preserving Radiation Model
| dc.contributor.author | Shetty, Rajath Krishna | en |
| dc.contributor.committeechair | Massa, Luca | en |
| dc.contributor.committeemember | Young, Gregory | en |
| dc.contributor.committeemember | Meadows, Joseph | en |
| dc.contributor.committeemember | England, Scott Leslie | en |
| dc.contributor.department | Aerospace and Ocean Engineering | en |
| dc.date.accessioned | 2025-01-23T09:00:55Z | en |
| dc.date.available | 2025-01-23T09:00:55Z | en |
| dc.date.issued | 2025-01-22 | en |
| dc.description.abstract | 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. | en |
| dc.description.abstractgeneral | Chemical kinetics is often too slow compared to turbulent mixing in high-speed propulsion, limiting the effectiveness of conventional flame stabilization devices. This project investigates how a non-equilibrium plasma can support combustion in a turbulent supersonic combustor at Mach 2. Plasma can support both vibrational-electronic energy exchanges and radical branching boosting the ignition time-scales up to the microsecond range. This thesis centers around the development of a CFD model that incorporates the effects of high-speed convection, photoionization, and plasma effects by using the drift-diffusion equation. In addition, a novel chemistry model has been developed to model the ultra-fast chemistry of triplet nitrogen states, these states appear in the plasmas that are studied. A verification and validation process is conducted on the code and its various components. This code is then used to study how nanosecond repetitive pulsed discharges (NRPD), which are an efficient way to create plasmas, are affected by scramjet flow conditions. The results in this thesis show that these plasmas can increase the temperature and improve the conditions for combustion. Two major studies have been done in this thesis with this code. First, the physics of the energy transfer is studied for the NRPD in a computational domain containing differently shaped electrodes (both flat and curved electrodes). The flat electrodes provide the strongest energy transfer to the plasma and the fluid. Next, large-scale simulations on three-dimensional scramjet geometries are performed and compared to the experiments. The effect of the electrode placement in the cavity is discussed. | en |
| dc.description.degree | Doctor of Philosophy | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:42461 | en |
| dc.identifier.uri | https://hdl.handle.net/10919/124320 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Plasma-assisted combustion | en |
| dc.subject | CFD | en |
| dc.subject | Radiation | en |
| dc.title | Plasma Assisted Ignition in a Three-dimensional Scramjet Combustor with a Photon-preserving Radiation Model | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Aerospace Engineering | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |
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