Water-in-Oil (W/O) emulsions are a promising technology that could be used in order to reduce pollutant emissions with respect to classical hydrocarbon fuels [1]. The pollutant reduction is partially due to a phenomenon called micro-explosion, which results from the difference in boiling temperature between the continuous and the dispersed phase. This secondary atomization of the emulsion droplets ends up in a cloud of dispersed child droplets, allowing a more efficient combustion because of the better fuel-air mixing [2]. Experiments shown that the behavior of the dispersed (water) phase during the heating has a strong influence on the micro-explosion occurrence and its quality. Unstable and coarse emulsions will undergo fast coalescence of the water droplets in bigger one [3], while fine emulsions will be subject to convective motion due to the heterogeneity of the temperature field within the emulsion drop [4]. This convective motion of the water droplets reduces the coalescence rate, resulting in a lower micro-explosion occurrence. The present study focuses on the measurement of the temperature of the water droplets within an emulsion droplet under radiant heating. The 2-colors Laser-Induced-Fluorescence (2CLIF) is used, with one dye and two bands of detection. Water phase is seeded with Rhodamine 6G, which is only soluble in water and gives a strong response signal to the excitation by a continuous laser of wavelength 532 nm. The emulsion droplet is heated by a radiant infrared panel which temperature can be controlled. A previous experiment demonstrated that convective motion of the water droplets happens even when the heat source is located at the top of the emulsion drop, because of the focusing effect of the emulsion drop which tends to create a hot zone located somewhere in the lower region of the emulsion drop. In the present study, the objective is to give an insight of the temporal and spatial evolution of the water phase temperature during the heating. [1] Abdollahi, B., Ghobadian, B., Najafi, G., Hoseini, S., Mofijur, M., Mazlan, M., "Impact of water - biodiesel - diesel nano-emulsion fuel on performance parameters and diesel engine emission", Fuel. 280 (2020). [2] Moussa O., Tarlet D., Massoli P. , Bellettre J., "Investigation on the conditions leading to the micro-explosion of emulsified fuel droplet, using two colors LIF method", Experimental Thermal and Fluid Science. 116 (2020). [3] Tarlet, D., Josset, C., Bellettre, J., "Comparison between unique and coalesced water drops in micro explosions scanned by differential calorimetry", International Journal of Heat and Mass Transfer.95: 689-692 (2016). [4] Naudin, T., Tarlet, D., Calabria, R., Massoli, P., Bellettre, J. "Experimental study of water-in-oil droplet micro-explosion using LIF measurements: effect of radiative heating configuration", ILASSAmericas 32nd Annual Conference on Liquid Atomization and Spray Systems, Madison, USA, paper VII-11, pp 766-773.
Experimental study of emulsion dispersed phase temperature under radiant heating using 2clif method
CALABRIA Raffaela;MASSOLI Patrizio;
2023
Abstract
Water-in-Oil (W/O) emulsions are a promising technology that could be used in order to reduce pollutant emissions with respect to classical hydrocarbon fuels [1]. The pollutant reduction is partially due to a phenomenon called micro-explosion, which results from the difference in boiling temperature between the continuous and the dispersed phase. This secondary atomization of the emulsion droplets ends up in a cloud of dispersed child droplets, allowing a more efficient combustion because of the better fuel-air mixing [2]. Experiments shown that the behavior of the dispersed (water) phase during the heating has a strong influence on the micro-explosion occurrence and its quality. Unstable and coarse emulsions will undergo fast coalescence of the water droplets in bigger one [3], while fine emulsions will be subject to convective motion due to the heterogeneity of the temperature field within the emulsion drop [4]. This convective motion of the water droplets reduces the coalescence rate, resulting in a lower micro-explosion occurrence. The present study focuses on the measurement of the temperature of the water droplets within an emulsion droplet under radiant heating. The 2-colors Laser-Induced-Fluorescence (2CLIF) is used, with one dye and two bands of detection. Water phase is seeded with Rhodamine 6G, which is only soluble in water and gives a strong response signal to the excitation by a continuous laser of wavelength 532 nm. The emulsion droplet is heated by a radiant infrared panel which temperature can be controlled. A previous experiment demonstrated that convective motion of the water droplets happens even when the heat source is located at the top of the emulsion drop, because of the focusing effect of the emulsion drop which tends to create a hot zone located somewhere in the lower region of the emulsion drop. In the present study, the objective is to give an insight of the temporal and spatial evolution of the water phase temperature during the heating. [1] Abdollahi, B., Ghobadian, B., Najafi, G., Hoseini, S., Mofijur, M., Mazlan, M., "Impact of water - biodiesel - diesel nano-emulsion fuel on performance parameters and diesel engine emission", Fuel. 280 (2020). [2] Moussa O., Tarlet D., Massoli P. , Bellettre J., "Investigation on the conditions leading to the micro-explosion of emulsified fuel droplet, using two colors LIF method", Experimental Thermal and Fluid Science. 116 (2020). [3] Tarlet, D., Josset, C., Bellettre, J., "Comparison between unique and coalesced water drops in micro explosions scanned by differential calorimetry", International Journal of Heat and Mass Transfer.95: 689-692 (2016). [4] Naudin, T., Tarlet, D., Calabria, R., Massoli, P., Bellettre, J. "Experimental study of water-in-oil droplet micro-explosion using LIF measurements: effect of radiative heating configuration", ILASSAmericas 32nd Annual Conference on Liquid Atomization and Spray Systems, Madison, USA, paper VII-11, pp 766-773.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
