Joint Temperature and Soot-Volume-Fraction Measurements in Turbulent Meter-Scale Pool Fires

The development of a combined dual-pump coherent anti-Stokes Raman scattering (CARS) and laser-induced incandescence (LII) instrument for the spatially resolved measurement of subgrid-scale temperature/soot data in liquid-fueled pool fires is discussed. Temperature pdfs obtained from the N2 Q-branch CARS signal at the center of a 2-m-diameter toluene/methanol pool fire are summarized. A more detailed discussion of the recent development of a water-jacketed, fiber-optically coupled LII probe for in-fire soot-volume-fraction imaging is presented. Tomographically resolved laser-light-extinction characterization of the soot field in a fuel-rich premixed ethylene-air flame used for calibration of the LII technique is reported, and the performance of the LII-imaging system in the calibration flame is discussed. Two-dimensional LII images, which are representative of the spatially resolved, instantaneous soot-volume-fraction distributions in a 2-m-diameter toluene/methanol pool fire are provided, and a histogram of the LII signal that is representative of the pdf of the soot-volume-fraction fluctuations at the center of the fire are extracted from these in-fire imaging results. These data demonstrate the potential of the CARS and LII instruments to determine temperature and soot volume fraction in a sooting fire with high temporal and spatial resolution