Investigation on spherically expanding flame temperature of n-butane/air mixtures with tunable diode laser absorption spectroscopy |
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| Institution: | 1. Physico-Chemical Fundamentals of Combustion, RWTH Aachen University, Schinkelstraße 8, D-52062 Aachen, Germany;2. Institute of Technical Thermodynamics, RWTH Aachen University, Schinkelstraße 8, D-52062 Aachen, Germany;1. Spectral Energies, LLC, 4065 Executive Dr., Beavercreek, OH 45430, USA;2. Air Force Research Laboratory, Wight-Patterson Air Force Base, OH 45433, USA;1. Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551, USA;2. Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA;3. X-Ray Sciences Division, Argonne National Laboratory, Argonne, IL 60439, USA;1. Key Laboratory for Power Machinery and Engineering of MOE, Shanghai Jiao Tong University (SJTU), Shanghai 200240, PR China;2. National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, PR China;3. School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, PR China |
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| Abstract: | A joint schlieren imaging, pressure recording and tunable diode laser absorption spectroscopy (TDLAS) thermometry technique was developed to simultaneously determine the flame radius, pressure and line-of-sight averaged temperature of spherically expanding flames of n-butane/air mixtures at initial temperature of 298 K, initial pressure of 1 atm and equivalence ratios of 0.9–1.5. To probe the flame temperature, a mid-infrared interband cascade laser at 4.2 µm was used to measure the time-resolved direct absorption spectra of CO2 which are strongly related to flame temperature, CO2 mole fraction, flame radius and pressure. Quantitative line-of-sight averaged temperatures of burnt gas were obtained by fitting the normalized absorbance spectra. Three typical stages, including the spark affected initial stage, quasi-steady stage and the pressure induced growing stage are determined from the evolution of measured temperature as a function of time and flame radius. The relation between flame temperature, stretch rate and burning velocity of burnt gas are analyzed. Stretch rate is found to have minor effect on the measured temperature in the quasi-steady stage. The relative variation of temperature is much smaller than that of velocity. The flame with lower normalized temperature tends to propagate slower. |
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