Hansen, L
1992
CARS Temperature Measurements in the Brigham Young University Controlled Profile Reactor in Natural Gas and Natural Gas-Assisted Coal Flames
Pyper, D.K.; Blackham, S.; Warren, D.; Hansen, L.; Christensen, J.; Haslam, J.; Germane, G.J. and Hedman, P.O.
Fall Meeting of the Western States Section/Combustion Institute, Berkeley, CA, October 1992. Funded by ACERC.
Coherent anti-Stokes Raman spectroscopy (CARS) is a laser diagnostic technique that can be used to determine temperature and major species concentrations in harsh combustion environments without the disturbing influence of a sample probe. CARS can be applied to dirty, luminous systems because it has a large signal to interference ratio due to high signal conversion efficiency and the coherent nature of the CARS spectral emission. CARS has been shown to be an effective means of determining the temperature and species concentrations in clean gas flames (Boyack, 1990). CARS measurements are more difficult to make in particle-laden flames due to the increased luminosity and enhanced background caused by particle and gas breakdown. The increased luminosity and breakdown alter the shape and intensity of the CARS signal, thus making analysis with unmodified versions of standard CARS fitting codes more complex.
The objectives of this study were to extend the capability at Brigham Young University (BYU) of making temperature measurements in the BYU-ACERC Controlled Profile Reactor (CPR) with gaseous and pulverized coal fuels, to demonstrate the ability of making reliable CARS temperature measurements in both clean and dirty flame, and to collect representative sets of data in a natural gas and in natural gas assisted coal flames. CARS temperatures were produced with a natural gas flame and with a mixture of natural gas and Utah Blind Canyon bituminous coal. The CARS signal in the natural gas-assisted coal flame showed the same resonant spectra from particle-induced gas breakdown as has been seen previously (Hancock, 1991 and 1992). The techniques of Hancock were used to account for the background spectra in analyzing the data from the coal flame. The coal concentration in the flame was limited by the CARS signal strength and the particle-induced gas breakdown signal strength at the detector.
CARS measurements were obtained at 4 cm intervals from -20 to +40 cm across the diameter of the 80 cm combustor. These radial data sets were collected at 10 different axial locations along the 2.5 m height of the reactor, giving a total of 160 separate locations. Two hundred single laser pulses were used at each location within the reactor to collect "single shot" temperature data, which allowed the calculation of local mean temperatures as well as probability density functions. These 200 single shots were repeated at least twice during the same test and several tests were duplicated. It was found that the temperature measurements were in good agreement during a single test, but the accuracy was in the order of ±100 K from test to test.
Hansen, L
1992
CARS Temperature Measurements in the Brigham Young University Controlled Profile Reactor in Natural Gas and Natural Gas-Assisted Coal Flames
Pyper, D.K.; Blackham, S.; Warren, D.; Hansen, L.; Christensen, J.; Haslam, J.; Germane, G.J. and Hedman, P.O.
Fall Meeting of the Western States Section/Combustion Institute, Berkeley, CA, October 1992. Funded by ACERC.
Coherent anti-Stokes Raman spectroscopy (CARS) is a laser diagnostic technique that can be used to determine temperature and major species concentrations in harsh combustion environments without the disturbing influence of a sample probe. CARS can be applied to dirty, luminous systems because it has a large signal to interference ratio due to high signal conversion efficiency and the coherent nature of the CARS spectral emission. CARS has been shown to be an effective means of determining the temperature and species concentrations in clean gas flames (Boyack, 1990). CARS measurements are more difficult to make in particle-laden flames due to the increased luminosity and enhanced background caused by particle and gas breakdown. The increased luminosity and breakdown alter the shape and intensity of the CARS signal, thus making analysis with unmodified versions of standard CARS fitting codes more complex.
The objectives of this study were to extend the capability at Brigham Young University (BYU) of making temperature measurements in the BYU-ACERC Controlled Profile Reactor (CPR) with gaseous and pulverized coal fuels, to demonstrate the ability of making reliable CARS temperature measurements in both clean and dirty flame, and to collect representative sets of data in a natural gas and in natural gas assisted coal flames. CARS temperatures were produced with a natural gas flame and with a mixture of natural gas and Utah Blind Canyon bituminous coal. The CARS signal in the natural gas-assisted coal flame showed the same resonant spectra from particle-induced gas breakdown as has been seen previously (Hancock, 1991 and 1992). The techniques of Hancock were used to account for the background spectra in analyzing the data from the coal flame. The coal concentration in the flame was limited by the CARS signal strength and the particle-induced gas breakdown signal strength at the detector.
CARS measurements were obtained at 4 cm intervals from -20 to +40 cm across the diameter of the 80 cm combustor. These radial data sets were collected at 10 different axial locations along the 2.5 m height of the reactor, giving a total of 160 separate locations. Two hundred single laser pulses were used at each location within the reactor to collect "single shot" temperature data, which allowed the calculation of local mean temperatures as well as probability density functions. These 200 single shots were repeated at least twice during the same test and several tests were duplicated. It was found that the temperature measurements were in good agreement during a single test, but the accuracy was in the order of ±100 K from test to test.