Medições de temperaturas de chamas de etanol utilizando fluorescência induzida por laser / Temperature Measurements in Ethanol Flames Using Laser Induced Fluorescence

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Conventional methods for the study of combustion are usually intrusive methods (for example, the use of thermocouples to measure flame temperatures), which might disturb the burning process (thermal, catalytic or aerodynamic effects). The diagnostics techniques using lasers, in addition to being non-intrusive, have high temporal and spatial resolution. They allow the “mapping” of in which the combustion zone and the identification, at each point of the flame, the various states in which the transient radicals are formed. In this work, the technique of Laser Induced Fluorescence (LIF) was used. This technique is based on the spectral emission from the OH radical species for the determination of the temperature in ethanol/oxigênio/air flames. This technique is largely employed in other countries, but in Brazil it has not been employed to study combustion processes. In the first step of our studies, a liquid fuel burner was constructed, producing premixed flames. Experimental setups for LIF emission (309,5 nm - 311,5 nm) and excitation, in two regions of the OH radical absorption spectrum A-X (0,0) (303 nm and 309 nm) and A-X (1,0) (278 nm - 280 nm) were tested. The best results were obtained by excitation in the region of the transitions S21(1) - S21(13) of the A-X (1,0) band, using the plot of Boltzmann. Measurements in ethanol flames at different positions along the burner vertical axis were obtained, and for flowsrates with equivalence ratios 1.0; 1.4 and 0.82. The results were compared with those obtained with the sodium line-reversal technique and agree within the experimental error values. The temperature values measured throughout a 55 mm distance above the burner in the ethanol flame varied from 2008 K ± 40 K to 2246 K ± 90 K for equivalence ratio 0.82; from 2198 K ± 65 K to 2295 K ± 127 K for equivalence ratio 1.0 and from 1905 64 K ± to 2238 K ± 155 K for equivalence ratio 1.4. Mixture of propane/butane flames were also studied in three positions throughout a 15 mm distance above the burner for equivalence ratios,equivalence ratio 1.0 equivalence ratio = 1.5 and equivalence ratio 0.87. The temperatures measured varied from 2423 K ± 102 K to 2622 K ± 106 K for equivalence ratio 0.87; from 2441 K ± 110 K to 2631 K ± 100 K for equivalence ratio 1.0 and from 2403 K ±109 K to 2605 K ±124 K for equivalence ratio 1.5. The present study shows that the LIF technique is suitable for “mapping” flame temperatures of gaseous as well as liquid. The temperatures measured showed experimental deviations lower than 8 %.

ASSUNTO(S)

fluorescência induzida por laser combustão ethanol etanol combustion laser induced fluorescence

ACESSO AO ARTIGO

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