Date of Award

Summer 8-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical and Computer Engineering

Committee Director

Chunqi Jiang

Committee Member

Linda Vahala

Committee Member

Shu Xiao

Committee Member

Peng Zhang

Abstract

The generation of repeatable and stable nanosecond pulsed atmospheric pressure plasmas is important to non-thermal plasma applications in various fields including medicine, material processing, food processing, and plasma ignition for combustion. This dissertation investigates the atmospheric pressure plasma initiation and formation under 10 – 200 ns pulsed power for electrode configurations applicable for transient plasma ignition (TPI) for combustion. The impacts of pulsed power parameters, gas condition, and electrode geometry on the discharge initiation and modes (i.e., streamer, transient spark and spark) are systematically evaluated for applying TPI for combustion. We evaluated the discharge modes driven by both longer and shorter voltage pulses in a needle-to-plate electrode configuration. In addition to the voltage and current waveforms, criteria of the discharge modes were assessed using energy deposition as well as gas temperatures measurement. Under longer voltage pulses two discharge modes (streamer and spark) were observed, whereas three discharge modes (streamer, transient spark, and low-impedance spark) were identified when the discharge was driven by shorter voltage pulses (10 ns). Lower PRF or shorter pulses require higher applied voltage for the streamer initiation and its transition to spark, whereas longer pulses or higher PRFs significantly reduces the required voltage. Among the three discharge modes, it has been found that the transient spark mode is the most efficient discharge regime as it can generate relatively higher reduced electric field (E/N).

Determining the electric field during discharge mode transition is hence important for the understanding of the Transient Plasma Ignition (TPI) process and ultimately allowing for the control of plasma chemistry. Using the Electric Field Induced Second Harmonic Generation (EFISH) technique, we determine the electric field (E) dynamics in a pin-to-pin electrode configuration in extremely lean CH4/air mixtures at 1 bar. It is revealed that the peak electric field occurs during the rising of the voltage pulse, and a minimum E/N of ~405 Td (E≈ 66 kV/cm) is required to form a transient spark under single-pulse conditions. Under Two-pulse sequences, higher PRFs enable transient spark formation at a lower applied voltage, while E/N increases due to elevated gas temperature, underscoring the advantage of high PRF repetitive TPIs over single or low PRF TPIs for lean combustion.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

DOI

10.25777/vbsz-f576

ISBN

9798193214229

ORCID

0000-0003-1775-7491

Download

Share

COinS