화학공학소재연구정보센터
Combustion and Flame, Vol.163, 90-99, 2016
Combustion kinetics of laser irradiated porous graphite from imaging Fourier transform spectroscopy
The combustion plumes arising from laser-irradiated graphite targets were investigated experimentally using hyperspectral, imaging Fourier transform spectroscopy (IFTS). Porous graphite targets were irradiated with a 1.07 pm, 20-kW ytterbium fiber laser at irradiances of 0.25-4 kW/cm(2). Emissive plumes from the oxidation of graphite in air were monitored using a mid-wave infrared imaging Fourier-transform spectrometer with spatial resolution of 0.52 mm per pixel. Strong spectral emission of CO and CO2 were observed in the infrared between 1900 and 2400 cm(-1) with an instrument spectral resolution of 2 cm(-1). A homogeneous single-layer plume, line-by-line radiative transfer model (LBLRTM) and two band models (EM2C and RADCAL) were applied to estimate spatial maps of temperature and column densities of CO and CO2 with a temporal resolution of 0.47 s per hyperspectral image. Steady surface temperatures of 1800-2900 K are achieved after 1 mm for irradiances of 0.25-1.0 kW/cm(2). A stable, gas phase combustion layer extends from 4 to 12 mm from the surface, with buoyancy driving a gas flow of similar to 8 m/s. Plume extent and intensity is greater for the larger porosity (6 mm particle size) samples. Steady-state gas temperatures exceed surface temperature by up to 400 K. Column densities for CO and CO2 of up to 1018 molec/cm(2) were observed. The CO/CO2 concentration ratio peaks at 2500 K. The initial rise with temperature is consistent with effective activation energies of 149-111 kJ/mol at distances between 0.72 mm and 3 mm, respectively. Published by Elsevier Inc. on behalf of The Combustion Institute.