ABSOLUTE NUMBER DENSITY MEASUREMENTS OF HYDROPEROXYL RADICAL IN A NANOSECOND PULSE DISCHARGE USING CAVITY RING-DOWN SPECTROSCOPY

A recently implemented cavity ring-down spectrometer has been used to perform absolute number density measurements of hydroperoxyl radical (HO$_{2}$) generated in a repetitive nanosecond-duration, pulse discharge sustained in a mixture of H$_{2}$/O$_{2}$/Ar. The probe source for the spectrometer is a custom-built, injection-seeded, optical parametric oscillator emitting an idler beam in the 1500 nm region accessing the first overtone (2$\nu$$_{1}$) of the O-H stretch. Water vapor was used as a standard species to characterize the spectrometer and provide estimates of the spectral linewidth, sensitivity, and noise level. A specially constructed ring-down cell, with the central portion consisting of rectangular quartz channel tubing and a pair of copper plate electrodes, was used to produce a repetitively pulsed discharge in a H$_{2}$/O$_{2}$/Ar mixture. Narrow bandwidth cavity ring down spectra are acquired of a hydroperoxyl absorption feature composed of numerous closely spaced ro-vibrational lines centered at 6638.20 \wn and number density is determined from the resulting spectral line. This is believed to be the first detection and quantitative measurement of hydroperoxyl radical produced in a nanosecond pulse discharge. The measured number density is compared to the value predicted by the kinetic model of a nanosecond pulse discharge in a reacting H$_{2}$/O$_{2}$/Ar mixture

Diagnostic development for determining the joint temperature/soot statistics in hydrocarbon-fueled pool fires : LDRD final report.

A joint temperature/soot laser-based optical diagnostic was developed for the determination of the joint temperature/soot probability density function (PDF) for hydrocarbon-fueled meter-scale turbulent pool fires. This Laboratory Directed Research and Development (LDRD) effort was in support of the Advanced Simulation and Computing (ASC) program which seeks to produce computational models for the simulation of fire environments for risk assessment and analysis. The development of this laser-based optical diagnostic is motivated by the need for highly-resolved spatio-temporal information for which traditional diagnostic probes, such as thermocouples, are ill-suited. The in-flame gas temperature is determined from the shape of the nitrogen Coherent Anti-Stokes Raman Scattering (CARS) signature and the soot volume fraction is extracted from the intensity of the Laser-Induced Incandescence (LII) image of the CARS probed region. The current state of the diagnostic will be discussed including the uncertainty and physical limits of the measurements as well as the future applications of this probe

ABSOLUTE NUMBER DENSITY MEASUREMENTS OF HYDROPEROXYL RADICAL IN A NANOSECOND PULSE DISCHARGE USING CAVITY RING-DOWN SPECTROSCOPY

A recently implemented cavity ring-down spectrometer has been used to perform absolute number density measurements of hydroperoxyl radical (HO$_{2}$) generated in a repetitive nanosecond-duration, pulse discharge sustained in a mixture of H$_{2}$/O$_{2}$/Ar. The probe source for the spectrometer is a custom-built, injection-seeded, optical parametric oscillator emitting an idler beam in the 1500 nm region accessing the first overtone (2$\nu$$_{1}$) of the O-H stretch. Water vapor was used as a standard species to characterize the spectrometer and provide estimates of the spectral linewidth, sensitivity, and noise level. A specially constructed ring-down cell, with the central portion consisting of rectangular quartz channel tubing and a pair of copper plate electrodes, was used to produce a repetitively pulsed discharge in a H$_{2}$/O$_{2}$/Ar mixture. Narrow bandwidth cavity ring down spectra are acquired of a hydroperoxyl absorption feature composed of numerous closely spaced ro-vibrational lines centered at 6638.20 \wn and number density is determined from the resulting spectral line. This is believed to be the first detection and quantitative measurement of hydroperoxyl radical produced in a nanosecond pulse discharge. The measured number density is compared to the value predicted by the kinetic model of a nanosecond pulse discharge in a reacting H$_{2}$/O$_{2}$/Ar mixture

Diagnostic development for determining the joint temperature/soot statistics in hydrocarbon-fueled pool fires : LDRD final report.

A joint temperature/soot laser-based optical diagnostic was developed for the determination of the joint temperature/soot probability density function (PDF) for hydrocarbon-fueled meter-scale turbulent pool fires. This Laboratory Directed Research and Development (LDRD) effort was in support of the Advanced Simulation and Computing (ASC) program which seeks to produce computational models for the simulation of fire environments for risk assessment and analysis. The development of this laser-based optical diagnostic is motivated by the need for highly-resolved spatio-temporal information for which traditional diagnostic probes, such as thermocouples, are ill-suited. The in-flame gas temperature is determined from the shape of the nitrogen Coherent Anti-Stokes Raman Scattering (CARS) signature and the soot volume fraction is extracted from the intensity of the Laser-Induced Incandescence (LII) image of the CARS probed region. The current state of the diagnostic will be discussed including the uncertainty and physical limits of the measurements as well as the future applications of this probe