Stereoscopic flow-tagging velocimetry

Krüger, Sascha; Grünefeld, Gerd

doi:10.1007/s003400050844

Cited by 34 publications

(20 citation statements)

References 1 publication

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“…MTV can be accomplished by direct seeding of the gas using biacetyl [9], N 2 O [11], NO 2 [12], NO [10,13], tert-butyl nitrate [14], and other molecular seeds [15][16][17]. However, these seeds can be expensive, toxic, damaging to the experimental apparatus, or not viable in reacting flows.…”

Section: Introductionmentioning

confidence: 98%

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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Section: Introductionmentioning

confidence: 98%

Vibrationally excited hydroxyl tagging velocimetry

Grady

Pitz

2014

Appl. Opt.

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“…Nitric oxide is a very stable MTV tag that has been used in both low-and high-temperature gas flows [23][24][25][26][27][28][29][30][31]. In low-pressure high-speed flows, NO can be naturally present (e.g., arc-heated tunnel) or directly added to the gas.…”

Section: Introductionmentioning

confidence: 99%

“…NO 2 has been added and photodissociated to form either ground-state NO [25,[27][28][29][30] or vibrationally excited NO that can be imaged in a background of ground-state NO [25,29]. Finally, tert butyl nitrate has been photodissociated to form an NO grid in a gas flow to measure velocity in 3D [31]. All of these NO tag MTV methods generally require the addition of a toxic gas [e.g., NO, NO 2 , (CH 3 ) 3 CONO] to the flow, limiting their application due to safety concerns.…”

Section: Introductionmentioning

confidence: 99%

N2O molecular tagging velocimetry

Elbaz

Pitz

2012

Appl. Phys. B

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A new seeded velocity measurement technique, N 2 O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO tag line. Nitrous oxide "laughing gas" is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N 2 O to O( 1 D) that subsequently reacts with N 2 O to form NO. O 2 fluorescence induced by the ArF laser "writes" the original position of the NO line. After a time delay, the shifted NO line is "read" by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with 4% N 2 O in air, ∼1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations predict 800-1200 ppm of NO for 190-750 K at 1 atm and 850-1000 ppm of NO for 0.25-1 atm at 190 K. Decreasing the gas pressure (or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation. The very short NO formation time (<10 ns) makes the N 2 O MTV method amenable to low-and highspeed air flow measurements. The N 2 O MTV technique is demonstrated in air jet to measure its velocity profile. The N 2 O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of N 2 O with O( 1 D) from N 2 O photodissociation and thus does not depend on the bulk gas composition.

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“…The tracer molecule NO, which is not normally present in air, can be produced in several different ways: by dissociating NO 2 molecules in the focus of a 308-nm XeCl excimer laser [6], by dissociation of tert-butyl nitrite [7], or by irradiating air with an intense ArF laser beam. The latter is known under the acronym of APART (air photolysis and recombination tracking), and has been developed in our group over the last ten years [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Molecular tagging velocimetry in turbulence using biacetyl

2012

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We evaluate various molecular tagging velocimetry (MTV) techniques for application in turbulent flows of gases where the smallest length scales must be resolved. We argue that tracer diffusion dictates the use of large complex molecules and discuss a few candidate molecules. The accuracy of MTV is determined by the profile of written lines which widen due to molecular dynamics, including both diffusion and chemical reaction. We evaluate these profiles for tagging with phosphorescing biacetyl molecules, which is a commonly used probe in MTV. For relatively large laser power, these profiles are determined not by molecular diffusion, but by the triplet-triplet annihilation reaction of excited biacetyl molecules. We identify a new reaction pathway, and present a model for the observed line shapes. The rapid widening of tagged lines of biacetyl molecules due to chemical reaction restricts this MTV technique to large-scale turbulent motion in gases of comparable molecular weight.

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Stereoscopic flow-tagging velocimetry

Cited by 34 publications

References 1 publication

Vibrationally excited hydroxyl tagging velocimetry

Vibrationally excited hydroxyl tagging velocimetry

N2O molecular tagging velocimetry

Molecular tagging velocimetry in turbulence using biacetyl

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