Mixture fraction, soot volume fraction, and velocity imaging in the soot-inception region of a turbulent non-premixed jet flame

Abstract

An experimental study is performed to investigate the feasibility of conducting simultaneous mixture fraction, soot volume fraction and velocity imaging in sooting jet flames. The measurements are performed in the soot-inception region of ethylene jet flames, where the yellow luminous region first appears in the flame. Three-component velocity and soot volume fraction are measured by stereoscopic particle image velocimetry and laser-induced incandescence, respectively. The mixture fraction is inferred from laser-induced fluorescence of krypton gas seeded into the fuel stream. To obtain mixture fraction from the fluorescence signal, the signal must be corrected for density and fluorescence quenching effects. This correction is accomplished by invoking an assumed state relationship that is derived from a laminar strained-flame calculation. Once properly calibrated, the krypton planar laserinduced fluorescence data give the mixture fraction, temperature and major species near the regions of soot formation. The krypton is seeded into the fuel jet at a mole fraction of approximately 4%. The fluorescence of krypton is achieved by two-photon absorption at 214.7 nm and the resulting fluorescence is collected at 760.2 nm. The krypton fluorescence signal is rather weak, particularly near the reaction zones where density is lowest, and so adequate signal-to-noise ratios could be achieved in a sheet only about 1 mm in height, which effectively limited this study to a line measurement of mixture fraction. The temperature field derived from the mixture fraction field was compared to temperatures obtained from thermocouple measurements. The mean radial temperature profiles using the different techniques show excellent agreement and this serves to validate the methodology used to map from fluorescence signal to mixture fraction and temperature. The resulting data are of high enough quality as to allow the investigation of the kinematics, thermo-chemical state and even the dissipation fields near regions of soot formation.

Large-Eddy Simulation and analysis of a sooting lifted turbulent jet flame

“…Maximum LES values of f v are always located between 1400 K < T < 1700 K, which is well within the range observed in measurements that extends over 1350 K < T < 1750 K [16,35,38,40,42].…”

“…Measurements in flames with similar fuels disagreed as to whether such a correlation exists [34] or not [35]. Several experimental studies of soot statistics (e.g., [36,37]) and correlated soot statistics (e.g., [38][39][40][41][42][43]) have been published since. Comparison with these experimental results will be discussed during the analysis of the present LES results.…”

“…Correlated statistics of soot and related quantities have been used to advance the understanding of soot evolution in turbulent flames both by measurements (e.g., [38][39][40][41][42][43]) and simulations (e.g., [7,24,47,77,78]). Such correlated statistics have also been measured in the investigated SLTJF by Gu et al [16].…”

Development of a soot concentration estimation library for industrial combustion applications using Lagrangian parcel tracking

“…However, a strong correlation has been shown between mixture fraction and soot concentration [71]. Also, soot is known to form in flame regions with temperatures between 1300 K and 1600 K [15].…”

Development and testing of a soot particle concentration estimator using Lagrangian post-processing

“…It should be noted that this list was based in part from a trial-and-error process that has not yet been exhaustive. However, a strong correlation has been shown between mixture fraction and soot concentration (Park, Burns, Buxton, & Clemens, 2017). Also, soot is known to form in flame regions with temperatures between 1300 K and 1600 K (Turns, 2000).…”