Gas Flow Visualization Using Laser-induced Fluorescence

Abstract

Laser-induced fluorescence (LIF) is one of the methods for visualization of mixing and velocity field of supersonic flows. The method permits almost nonintrusive study of gas flow dynamics in jet engines with a high temporal and spatial resolution. The nature of supersonic flow implies large pressure, temperature and density gradients which might introduce considerable errors into the interpretation of the images, because LIF intensity strongly depends upon excited particle fluorescence decay lifetime in addition to its number density in the medium. An excited particle quenching rate usually depends on the local gas density and temperature. Therefore, for correct interpretation of the images it is necessary to know the temperature dependence of the quenching rate constants. In this work the method is developed to measure the temperature dependence of the quenching rate constant of the fluorescing particle using LIF.

Confounding effects of temperature in laser-induced fluorescence concentration measurements with iodine vapor

“…[60] 532 0.71 < 30 Ar i C S Muruganandam et al [24] 532 1.03 < 6 air C S Wu et al [25] 532 1.22 < 2.5 N 2 C S Wu et al [26] 527 1.22 < 2.5 N 2 C S Xu et al [27] 527 1.22 < 2.5 N 2 C S C S -CMOS/CCD camera sensor, i C S -intensified CCD camera sensor Iodine vapor was first used as a LIF tracer by Hiller & Schmidt-Ott (1977) [9] for flow visualization of low density gas-jets. Since then, iodine vapor has been employed for flow visualization over a wide range of flow regimes: subsonic [23][24][25][26][27], transonic [4,28], supersonic [10,29,30], hypersonic [31,32], and rarified flows [33,34]. Iodine vapor was also used to make quantitative measurements of flows, including pressure [35][36][37][38], velocity [10,14,39], temperature [37,[40][41][42], and scalar concentration fields [23,37,[43][44][45][46][47].…”