Simultaneous Species Concentration and Temperature Measurements Using Laser Induced Breakdown Spectroscopy with Direct Spectrum Matching

Master's Thesis

Abstract

Laser induced breakdown spectroscopy (LIBS) is used to simultaneously measure hydrocarbon fuel concentration and temperature in high temperature, high speed, compressible, and reacting flows, a regime in which LIBS has not been done previously. Emission spectra from the plasma produced from a focused laser pulse is correlated in the combustion region of a model scramjet operating in supersonic wind tunnel. A 532 nm Nd:YAG laser operating at 10 Hz is used to induce breakdown. The emissions are captured during a 10 ns gate time approximately 75 ns after the first arrival of photons at the measurement location in order to minimize the measurement uncertainty in the turbulent, compressible, high-speed, and reacting environment. Three methods of emission detection are used and a new backward scattering direction method is developed that is beneficial in reducing the amount of optical access needed to perform LIBS measurements. Measurements are taken in the model supersonic combustion and the ignition process is shown to be highly dependent on fuel concentration and gas density as well as combustion surface temperature, concentration gradient, and flow field. Direct spectrum matching method is developed and used for quantitative measurements. In addition, a comprehensive database of spectra covering the fuel concentrations and gas densities found in the wind tunnel of Research Cell 19 at Wright Patterson Air Force Base is created which can be used for further work.

Attributes

Attribute NameValues
URN
  • etd-02232015-101626

Author Brendan Joseph McGann
Advisor Hyungrok Do
Contributor Flint Thomas, Committee Member
Contributor Scott Morris, Committee Member
Contributor Hyungrok Do, Committee Chair
Degree Level Master's Thesis
Degree Discipline Aerospace and Mechanical Engineering
Degree Name MSAeroE
Defense Date
  • 2015-01-27

Submission Date 2015-02-23
Country
  • United States of America

Subject
  • Laser Diagnostics

  • Combustion

  • LIBS

  • Reacting Flows

Publisher
  • University of Notre Dame

Language
  • English

Record Visibility and Access Public
Content License
  • All rights reserved

Departments and Units

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