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Spectroscopic Investigation of Nitromethane Flames
Author(s) -
Eckl Wilhelm,
Weiser Volker,
Weindel Martin,
Eisenreich Norbert
Publication year - 1997
Publication title -
propellants, explosives, pyrotechnics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.56
H-Index - 65
eISSN - 1521-4087
pISSN - 0721-3115
DOI - 10.1002/prep.19970220316
Subject(s) - nitromethane , chemistry , infrared , combustion , analytical chemistry (journal) , spectral line , adiabatic flame temperature , ultraviolet , diatomic molecule , radical , atmospheric temperature range , infrared spectroscopy , emissivity , photochemistry , molecule , materials science , organic chemistry , optics , thermodynamics , combustor , physics , optoelectronics , astronomy
Nitromethane (CH 3 NO 2 ) Pool Fire Flames have been investigated analysing both, the radiation emitted from intermediate combustion radicals (diatomic molecules) in the ultraviolet (UV) and visible (VIS) spectral range, and the near infrared spectra dominated by broad water bands. Comparing the UV/VIS spectra to calculated band profiles, rotational and vibrational temperatures (T rot , T vib ) of OH, NH and CN have been determined. At local thermal equilibrium T rot and T vib must be equal. The determined temperatures show that the OH and NH emissions originate from pure thermal excitation (T rot = T vib = 2300 K–2380 K) but the CN emissions show additionally a chemical excitation indicated by different vibrational and rotational temperatures in the Boltzman factor (T rot = 2100 K, T vib = 4300 K). For a more detailed study of the flame, the emission of OH radicals has been investigated more extensively by monitoring a two‐dimensional rotational temperature and emissivity profile. In cooler flame regions, the observed spectra are dominated by the near infrared radiation emitted from stable combustion products like water and carbon dioxide. Therefore, NIR spectra (1000 nm to 2500 nm) have been compared to broad band profiles calculated with a self‐developed code basing on the data of the ‘Handbook of Infrared Radiation of Combustion Gases’. The flame temperatures obtained by this method range from 1800 K to 1900 K. The results are correlated to flames of methane and nitrogen oxide which emit similar spectra indicating similar reaction mechanisms in the gaseous phase.