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Title: Dual-pump CARS temperature and major species concentration measurements in counter-flow methane flames using narrowband pump and broadband Stokes lasers

Dual-pump coherent anti-Stokes Raman scattering (CARS) is used to measure temperature and species profiles in representative non-premixed and partially-premixed CH{sub 4}/O{sub 2}/N{sub 2} flames. A new laser system has been developed to generate a tunable single-frequency beam for the second pump beam in the dual-pump N{sub 2}-CO{sub 2} CARS process. The second harmonic output ({proportional_to}532 nm) from an injection-seeded Nd:YAG laser is used as one of the narrowband pump beams. The second single-longitudinal-mode pump beam centered near 561 nm is generated using an injection-seeded optical parametric oscillator, consisting of two non-linear {beta}-BBO crystals, pumped using the third harmonic output ({proportional_to}355 nm) of the same Nd:YAG laser. A broadband dye laser (BBDL), pumped using the second harmonic output of an unseeded Nd:YAG laser, is employed to produce the Stokes beam centered near 607 nm with full-width-at-half-maximum of {proportional_to}250 cm{sup -1}. The three beams are focused between two opposing nozzles of a counter-flow burner facility to measure temperature and major species concentrations in a variety of CH{sub 4}/O{sub 2}/N{sub 2} non-premixed and partially-premixed flames stabilized at a global strain rate of 20 s{sup -1} at atmospheric-pressure. For the non-premixed flames, excellent agreement is observed between the measured profiles of temperature and CO{submore » 2}/N{sub 2} concentration ratios with those calculated using an opposed-flow flame code with detailed chemistry and molecular transport submodels. For partially-premixed flames, with the rich side premixing level beyond the stable premixed flame limit, the calculations overestimate the distance between the premixed and the non-premixed flamefronts. Consequently, the calculated temperatures near the rich, premixed flame are higher than those measured. Accurate prediction of the distance between the premixed and the non-premixed flames provides an interesting challenge for future computations. (author)« less
Authors:
; ; ; ; ;  [1]
  1. School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)
Publication Date:
OSTI Identifier:
21328639
Resource Type:
Journal Article
Resource Relation:
Journal Name: Combustion and Flame; Journal Volume: 157; Journal Issue: 7; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; METHANE; CARBON DIOXIDE; LAMINAR FLAMES; COUNTERFLOW SYSTEMS; CONCENTRATION RATIO; DISTANCE; ATMOSPHERIC PRESSURE; CALCULATION METHODS; NONLINEAR PROBLEMS; RAMAN EFFECT; CHEMICAL COMPOSITION; FORECASTING; TEMPERATURE DISTRIBUTION; OXYGEN; NITROGEN; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 1000-4000 K Dual-pump CARS; Non-premixed flames; Partially-premixed flames; Laminar counter-flow flames; Laser diagnostics