Determination of liquefied petroleum flame temperatures using emission spectroscopy

emission spectroscopy was used in the temperature determination of lpg (liquefied petroleum gas) premixed flames. natural emission of ch* radicals was investigated in flames under three different burning conditions: fuel/oxydizer stoichiometric ratio, fuel excess (rich flame), and oxidizer excess (lean flame). an average value of 2845 ± 70 k was obtained for ch* rotational temperature in the set up used in the experiments. this value did not show significant change with the type of flame analyzed and it is compatible with the calculated adiabatic flame temperatures of the investigated systems. this temperature value also agrees with that determined by an indirect measurement, using the sodium line reversal method, which is independent from the radical natural emission and well established in literature. vibrational temperatures of ca. 4600 k were calculated, indicating that the ch* lifetime is insufficient for the establishment of an equilibrium state between the rotational and vibrational modes.