Ignition and hydrodynamic ejections by laser-induced breakdowns
type: CreativeWork
description: A focused laser can cause optical breakdown of gas, forming a high-temperature plasma that rapidly absorbs laser energy. As a source of heat and radical species, laser-based energy deposition can be an effective ignition source, and its relative versatility and precision make it an attractive alternative to conventional ignition methods. Understanding of the breakdown-induced flow, its dependence on details of the plasma generation, and how it can alter and tailor ignition and subsequent flame growth will facilitate incorporation into engineering applications such as internal combustion engines and supersonic propulsion systems. Direct numerical simulation with five gas models, in conjunction with an energy-deposition model that reproduces key experimental observations, is used to analyze the post-breakdown flow and ignition dynamics by direct numerical simulation. A perfect-gas model shows that the breakdown-induced flow occurs primarily by hydrodynamic processes that explain a curious experimental observation: hot gas ejects from the breakdown region along the laser axis, traveling up to distances several times the plasma kernel size, and can reverse direction for small changes in breakdown conditions. Vorticity-generating mechanisms are quantified and shown to be sensitive to asymmetries in the kernel's hydrodynamic expansion, and changes to the kernel geometry can lead to the observed ejection or its reversal. Even subtle alterations—such as a 20% increase in aspect ratio—can lead to qualitative differences in the vorticity dynamics and ultimate flow pattern. Rich flow phenomenology is caused by dual-pulse configurations, and mechanisms by which the ejection can be disrupted or enhanced by the second deposition are analyzed. For simultaneous depositions, vorticity generation can be suppressed by even a small secondary kernel, preventing the ejection from forming, whereas for time-delayed depositions, asymmetry in the kernel expansion can amplify ejection or prec…
abstract: A focused laser can cause optical breakdown of gas, forming a high-temperature plasma that rapidly absorbs laser energy. As a source of heat and radical species, laser-based energy deposition can be an effective ignition source, and its relative versatility and precision make it an attractive alternative to conventional ignition methods. Understanding of the breakdown-induced flow, its dependence on details of the plasma generation, and how it can alter and tailor ignition and subsequent flame growth will facilitate incorporation into engineering applications such as internal combustion engines and supersonic propulsion systems. Direct numerical simulation with five gas models, in conjunction with an energy-deposition model that reproduces key experimental observations, is used to analyze the post-breakdown flow and ignition dynamics by direct numerical simulation. A perfect-gas model shows that the breakdown-induced flow occurs primarily by hydrodynamic processes that explain a curious experimental observation: hot gas ejects from the breakdown region along the laser axis, traveling up to distances several times the plasma kernel size, and can reverse direction for small changes in breakdown conditions. Vorticity-generating mechanisms are quantified and shown to be sensitive to asymmetries in the kernel's hydrodynamic expansion, and changes to the kernel geometry can lead to the observed ejection or its reversal. Even subtle alterations—such as a 20% increase in aspect ratio—can lead to qualitative differences in the vorticity dynamics and ultimate flow pattern. Rich flow phenomenology is caused by dual-pulse configurations, and mechanisms by which the ejection can be disrupted or enhanced by the second deposition are analyzed. For simultaneous depositions, vorticity generation can be suppressed by even a small secondary kernel, preventing the ejection from forming, whereas for time-delayed depositions, asymmetry in the kernel expansion can amplify ejection or prec…
author: Wang, Jonathan M
language: en
keywords: Laser-induced breakdown, ignition, combustion, laser-energy deposition, nonequilibrium plasma, compressible flow, fluid dynamics
date published: 2021-03-05T21:36:44Z
date modified: 2026-07-22T22:24:50Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/109325