Laser diagnostic investigation of the structure of steady and driven hydrogen jet diffusion flames
Hancock, Robert Dean
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Permalink
https://hdl.handle.net/2142/22412
Description
Title
Laser diagnostic investigation of the structure of steady and driven hydrogen jet diffusion flames
Author(s)
Hancock, Robert Dean
Issue Date
1996
Doctoral Committee Chair(s)
Lucht, Robert P.
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
The structure of hydrogen jet diffusion flames has been investigated using coherent anti-Stokes Raman scattering (CARS) and laser-induced fluorescence (LIF) to obtain temperature and nitric oxide (NO) concentrations in steady laminar flames and during the interaction of induced fuel-side vortices with the diffusion flame sheet. The accuracy of the CARS system was evaluated by comparing experimental temperature measurements from H$\sb2$/air flames produced with a Hencken burner with adiabatic flame temperatures found using the NASA Lewis equilibrium code. The experimental temperature and mole fraction profiles are compared with the results of direct numerical simulations (DNS) of the flames. From a comparison of measured and calculated temperatures in steady, laminar, H$\sb2$ jet diffusion flames, thermal diffusion was found to be a significant effect. The experimental and computational results for the steady flames show good agreement when thermal diffusion effects are included in the DNS model.
CARS radial temperature profiles were obtained during vortex-flame interactions in $\rm H\sb2/N\sb2$ and $\rm H\sb2/N\sb2/He$ flames. It has been predicted by Katta and Roquemore (Combust. Flame 100:61-70 (1995)) that the local flame temperature in non-unity Lewis number flames can depart significantly from the local steady-state temperature during vortex-flame interactions. The CARS and DNS model results support this prediction and show similar temperature departures from the steady-state solution. The experimental and numerical NO LIF radial profiles show good quantitative agreement and similar trends. The flames with the highest concentration of nitrogen in the flame zone typically had the highest levels of NO.
A dual-pump CARS apparatus was developed for the simultaneous measurement of gas-phase temperature and the relative concentrations of molecular nitrogen and oxygen. A polarization technique was used to vary the relative intensities of the two CARS signals and expand the dynamic range of the relative concentration measurements. Temperature and oxygen mole fraction measurements obtained in the stabilization region of a $\rm H\sb2/N\sb2$ jet diffusion flame indicate that there exists a region below the nozzle rim where significant amounts of oxygen are found on the fuel side of the flame zone.
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