Experimental Assessment of Thermal Radiation Behavior Emitted by Laminar Diffusion Flames


Nattan Roberto Caetano†, Giulio Lorenzini‡, Marcos Antonio Klunk‡†, Luiz Alberto Oliveira Rocha‡†


† Federal University of Santa Maria, Santa Maria, RS, Brazil
‡ University of Parma, Parma, Italy
‡† University of Vale do Rio dos Sinos, São Leopoldo, RS, Brazil

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The present study consists of carrying out experimental measurements of thermal radiation emitted by laminar flames produced from the combustion of natural gas and ambient air. Therefore, we built a workbench containing a typical non-premixed flames burner. An intensity radiation sensor was connected to an oscilloscope to perform the measurements of the flow of radiant heat from the flame. Thus, measurements were made in the infrared spectral range, between 1.5 and 4.8 µm wavelength. The total energy emitted to the ambient has been obtained from integrating the radiant flux, measured in different flame configurations, on the lateral area of a virtual cylinder. The results allow us to quantify the radiant fraction and compare the models described in the literature. Moreover, bandpass spectral optical filters were used, centered at 3.75 and 4.75 µm, to assess the contribution of thermal radiation emitted by the soot particles and the CO2 contained in the hot gases produced from the fuel reaction. The measurement results show that the fraction of energy transferred by the mechanism of thermal radiation accounts for about 10% of the fuel’s latent energy. Therefore, approximately 2% of this radiation quantity is produced by soot particles, and about 14% due to CO2. These results are essential to support numerical model construction that represents the thermal radiation distribution emitted by flames.