title: Flame flow tagging velocimetry with 193-nm H2O photodissociation.
abstract: In a new nonintrusive, instantaneous flow tagging method called hydroxyl tagging velocimetry (HTV), a molecular grid of hydroxyl (OH) radicals is written into a flame and the displaced grid is imaged at a later time to give the flame's velocity profile. Single-photon photodissociation of vibrationally excited H(2)O, when a 193-nm ArF excimer laser is used, produces a tag line of superequilibrium OH and H photoproducts in a high-temperature flow field that itself may contain ambient OH. The tag line OH concentration is composed mostly of direct OH photoproducts, but OH is also indirectly produced through H photoproduct reactions with oxygen-bearing species. For lean and modestly rich flames the OH tag lifetime is of the order of 1 ms. For very rich H(2)-air flames (equivalence ratio of 4.4) the lifetime drops to 200 ns. After displacement the position of the OH tag line is revealed through fluorescence caused by OH (A-X) (3 <-- 0) excitation by using a 248-nm tunable KrF excimer laser. A HTV grid of multiple tag lines, providing multipoint velocity information, is experimentally demonstrated in a turbulent H(2)/N(2)-air diffusion flame.
authors.affiliation: Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA. wehrme@vuse.vanderbilt.edu
authors.forename: J A
authors.initials: JA
authors.lastname: Wehrmeyer
authors.forename: L A
authors.initials: LA
authors.lastname: Ribarov
authors.forename: D A
authors.initials: DA
authors.lastname: Oguss
authors.forename: R W
authors.initials: RW
authors.lastname: Pitz