Publications (3)3.63 Total impact
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Article: Basic aspects of OH(A), CH(A), and C2(d) chemiluminescence in the reaction zone of laminar methane–air premixed flames
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ABSTRACT: Detailed spatial intensity profiles of OH(A), CH(A), and C2(d) chemiluminescence in the reaction zone were revealed in “two-dimensional” laminar premixed flames (ϕ=0.85–1.5) using spatially resolved emission measurements with a resolution-enhanced Cassegrain-type optical probe. A numerical simulation of one-dimensional laminar premixed flames using the PREMIX code, with GRI-Mech 3.0 incorporating with reaction and quenching kinetics for OH(A), CH(A), and C2(d), was compared with the experimental result. The measured and simulated profiles showed reasonable agreement in shape, peak location, emission zone thickness, and peak-intensity variation in fuel-lean and stoichiometric flames. We found disagreement between the experimental and numerical results under fuel-rich conditions, which likely resulted from incomplete C2(d) chemistry used in the present study. Stoichiometry dependence of chemiluminescence peak-intensity ratio, OH(A)/CH(A), observed experimentally was clearly supported by the simulated result.Combustion and Flame. -
Article: Local chemiluminescence spectra measurements in a high-pressure laminar methane/air premixed flame
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ABSTRACT: The spatially resolved chemiluminescence in the reaction zone of a laminar premised methane/air flamewas measured. The pressure dependence of the flame front structure and chemiluminescence spectra were examined up to 1.5 MPa. Local point measurements of chemiluminescence were obtained using the Cassegrain optics system that we have developed, which has a high spatial resolution of d=0.1 mm and L=0.8 mm. Two types of measurements were performed: a local point chemiluminescence measurement with an ICCD camera with monochromator and selected chemiluminescence intensity measurements to obtain its profile and the flame front thickness at the flame front. The chemiluminescence at different pressures was examined to identify the main OH*, CH*, and C2* spectra. Background spectra related to CO-O* were observed at pressures greater than 0.5 MPa. Detailed OH* and CH* spectra were measured at different pressures, and the results indicate that each vibrational and rotational peak is in the same location, regardless of the pressure. The chemiluminescence intensity ratio of OH*/CH* at different pressures was examined. Less dependence on pressure was observed, although the individual chemiluminescence intensities changed with increasing pressure. The CO-O* broadband spectrum was significant at 0.5 MPa: its intensity remained at the same level at pressures greater than 0.5 MPa. This background spectrum was not observed at 0.1 MPa. In order to examine these chemiluminescence intensity profiles with the reaction zone and their dependence on pressure, the peak locations of OH*, CH*, and C2* were measured. The OH* peak was located inside the CH* and C2* curves for all measured pressures.Proceedings of the Combustion Institute 29(2):1495-1501. · 3.63 Impact Factor -
Article: Spatially resolved measurement of OH*, CH*, and C2* chemiluminescence in the reaction zone of laminar methane/air premixed flames
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ABSTRACT: Spatially and spectrally resolved chemiluminescence were measured in the reaction zone of a laminar premixed methane/air flame at equivalence ratios of 0.9–1.5 in atmospheric pressure using a new Cassegrain mirror system and a spectrometer with an intensified charge-coupled device. The measurement volume of the Cassegrain optics was estimated to be 100 μm in diameter and 800 μm long. Local flame spectra of the reaction zone showed remarkably high intensity of OH*, CH*, and C2* emission bands. The distributions of OH*, CH* and C2* emission intensities near the flame front were roughly revealed. The emission zone thickness of C2* was found to be the thinnest among these radicals. The OH* emission zone had a sharp distribution within a reaction zone, but its thickness was a little wider than that of either CH* or C2*. Highly spectrally resolved local OH*, CH*, and C2* chemiluminescent spectra were obtained at the local flame front. It was found that the dependence of the intensity of each rotational and vibrational head of the chemiluminescence on the equivalence ratio was almost the same as that of spectrally integrated band emissions of OH*, CH* and C2*. It was found that the strong correlations between the peak intensity ratios of OH*/CH*, C2*, and C2*/OH* in the reaction zone to the equivalence ratio could be used to investigate the local flame stoichiometry. OH*/CH* can be a good marker to determine the local flame stoichiometry in the reaction zone of methane/air premixed flames for a wide range of equivalence ratios.Proceedings of the Combustion Institute.
