Title: Pure-rotational H₂ thermometry by ultrabroadband coherent anti-Stokes Raman spectroscopy

Abstract

Coherent anti-Stokes Raman spectroscopy (CARS) is a sensitive technique for probing highly luminous flames in combustion applications to determine temperatures and species concentrations. CARS thermometry has been demonstrated for the vibrational Q-branch and pure-rotational S-branch of several small molecules. Practical advantages of pure-rotational CARS, such as multi-species detection, reduction of coherent line mixing and collisional narrowing even at high pressures, and the potential for more precise thermometry, have motivated experimental and theoretical advances in S-branch CARS of nitrogen (N₂), for example, which is a dominant species in air-fed combustion processes. Although hydrogen (H₂) is of interest given its prevalence as a reactant and product in many gas-phase reactions, laser bandwidth limitations have precluded the extension of CARS thermometry to the H₂ S-branch. We demonstrate H₂ thermometry using hybrid femtosecond/picosecond pure-rotational CARS, in which a broadband pump/Stokes pulse enables simultaneous excitation of the set of H₂ S-branch transitions populated at flame temperatures over the spectral region of 0–2200 cm^–1. We present a pure-rotational H₂ CARS spectral model for data fitting and compare extracted temperatures to those from simultaneously collected N₂ spectra in two systems of study: a heated flow and a diffusion flame on a Wolfhard-Parker slot burner. From 300 tomore » 650 K in the heated flow, the H₂ and N₂ CARS extracted temperatures are, on average, within 2% of the set temperature. For flame measurements, the fitted H₂ and N₂ temperatures are, on average, within 5% of each other from 300 to 1600 K. In conclusion, our results confirm the viability of pure-rotational H₂ CARS thermometry for probing combustion reactions.« less

Authors:

Courtney, Trevor L. ^[1]; Bohlin, Alexis  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-4383-8332"

Patterson, Brian D. ^[1]; Kliewer, Christopher J. ^[1]

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1. Sandia National Lab. (SNL-CA), Livermore, CA (United States)

Publication Date:

Mon Jun 12 00:00:00 EDT 2017

Research Org.:

Sandia National Lab. (SNL-CA), Livermore, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1473952

Alternate Identifier(s):

OSTI ID: 1363700

Report Number(s):

SAND-2018-10035J
Journal ID: ISSN 0021-9606; 667836

Grant/Contract Number:  

AC04-94AL85000

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 146; Journal Issue: 22; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY