Flow-tagging velocimetry using UV-photodissociation of water vapor

Goss, L. P.; Chen, T.; Trump, D. D.; Sarka, B.; Nejad, A.

doi:10.2514/6.1991-355

Cited by 10 publications

(5 citation statements)

References 18 publications

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“…In the ozone tagging velocimetry approach [8,9], molecular oxygen is laser dissociated and forms ozone, which is subsequently observed by laserinduced fluorescence. Similarly, water vapour can be dissociated with a laser to form OH radicals, which, again, are observed by laser-induced fluorescence [10,11]. The latter approach is particularly useful for studies of combustion [12].…”

Section: Introductionmentioning

confidence: 99%

The RELIEF flow tagging technique and its application in engine testing facilities and for helium-air mixing studies

Miles

Grinstead

Kohl³

et al. 2000

Meas. Sci. Technol.

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Raman excitation plus laser-induced electronic fluorescence (RELIEF) images the motion of oxygen molecules in air and other gas mixtures. This is accomplished by tagging oxygen molecules through vibrational excitation and imaging them after a short period of time by laser-induced electronic fluorescence. The vibrational lifetime of oxygen is sufficiently long and the signal sufficiently strong to allow this technique to be used over a wide range of flow conditions, from low subsonic to hypersonic, and in a variety of gas mixtures including high humidity environments. The utilization of a molecular tagging technique such as this is critical for environments in which seeding is impossible or unreliable and for measurements in which a wide range of scales needs to be observed simultaneously. Two experiments which have been conducted at national laboratories in medium- to large-scale facilities are reported. At the Arnold Engineering Development Center, RELIEF was used to examine velocity in a 1 m diameter tunnel for applications in the area of engine testing. At the NASA Langley Research Center, RELIEF is being used to examine supersonic mixing of helium in air in a coaxial jet in association with studies of fuel-air mixing in hypersonic engines. These applications are two examples of the wide range of practical uses for this new technology.

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Section: Introductionmentioning

confidence: 99%

The RELIEF flow tagging technique and its application in engine testing facilities and for helium-air mixing studies

Miles

Grinstead

Kohl³

et al. 2000

Meas. Sci. Technol.

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“…In this work, 2 nm × 248 nm photons excite water to the electronic C state, which results in at least 50% vibrationally hot photofragments (ν ≥ 1) [35]. The primary difference between the current work and previous efforts using 2 nm × 248 nm excitation [25,26] is the use of OH tracers in the first vibrationally excited state instead of the ground state. The physical process of forming vibrationally hot photofragments via thẽ C state is described elsewhere [36,37].…”

Section: Tag Formation Strategy and Experimental Systemmentioning

confidence: 90%

“…Previously, HTV measurements have been made using either 1 nm × 193 nm or 2 nm × 248 nm photons [18][19][20][21][22]25,26,32,34] to dissociate water to form the OH (ν 0) photofragment that is the molecular tracer via either the predissociativeÃ state for 1 nm × 193 nm excitation or the predissociativeC state for 2 nm × 248 nm excitation. In this work, 2 nm × 248 nm photons excite water to the electronic C state, which results in at least 50% vibrationally hot photofragments (ν ≥ 1) [35].…”

Section: Tag Formation Strategy and Experimental Systemmentioning

confidence: 99%

“…However, these seeds can be expensive, toxic, damaging to the experimental apparatus, or not viable in reacting flows. Therefore, unseeded methods have also been developed and implemented using linear processes to create O 3 [18] and OH [hydroxyl tagging velocimetry (HTV)] [18][19][20][21][22], and nonlinear techniques to make NO (APART) [23,24], OH [25,26], vibrationally excited O 2 (RELIEF) [27][28][29], and electronically excited N 2 using nanosecond [30] and femtosecond (FLEET) [31] lasers.…”

Section: Introductionmentioning

confidence: 99%

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Vibrationally excited hydroxyl tagging velocimetry

Grady

Pitz

2014

Appl. Opt.

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A new molecular-based velocity method is developed for high-temperature flame gases based on the hydroxyl tagging velocimetry (HTV) technique. In vibrationally excited HTV (VE-HTV), two photons from a KrF laser (248 nm) dissociate H₂O into a tag line of vibrationally excited OH (v=1). The excited state OH tag is selectively detected in a background of naturally occurring ground state OH (v=0). In atmospheric pressure laboratory burners, the OH (v=1) tag persists for 5-10 μs, allowing single-shot velocity measurements along a 2 cm line under lean, stoichiometric, and rich flame conditions with temperatures reaching 2300 K. Mean velocity measurements are demonstrated in a lean (ϕ=0.78) premixed H₂/air turbulent flame (Re=26,550) laboratory flame. The VE-HTV method is best suited to measure high-speed velocities in hot combustion environments in the presence of background OH.

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“…Flow tagging based on vibrational excitation of molecular oxygen, which has been termed Raman excitation followed by laser induced electronic fluorescence, has been applied both to low speed turbulent air jets (Noullez et al 1997) and to supersonic flow (Miles et al 1989). Gas phase flow tagging based on in situ laser production of hydroxyl radicals (Boedeker 1989, Goss et al 1991 and, more recently, ozone (Ribarov et al 1999) has also been reported. An inverse type of tagging, in which a two-colour, multi-photon absorption is used to photo-bleach sodium that is seeded into a flow, has also been reported recently (Barker et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Flow tagging velocimetry using caged dye photo-activated fluorophores

Lempert

Harris

2000

Meas. Sci. Technol.

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The use of caged dye photo-activated fluorophore velocimetry is described and representative examples are presented. After a brief survey of recently reported measurements, a more detailed example of the flow produced in a cylinder with a single rotating end wall is presented. Simultaneous stereoscopic image sets in the (r,z) and (r,θ) planes have been obtained over a Reynolds number range of roughly 102-105. At low Reynolds numbers (≃0-2000), the steady, axisymmetrical flow is found to quantitatively agree with predictions from a numerical flow solver. At higher Reynolds numbers (from 5×103 to 105), the flow develops considerable turbulent three-dimensional structure.

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Flow-tagging velocimetry using UV-photodissociation of water vapor

Cited by 10 publications

References 18 publications

The RELIEF flow tagging technique and its application in engine testing facilities and for helium-air mixing studies

The RELIEF flow tagging technique and its application in engine testing facilities and for helium-air mixing studies

Vibrationally excited hydroxyl tagging velocimetry

Flow tagging velocimetry using caged dye photo-activated fluorophores

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