Processing of individual rainbow signals
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The characterization of droplets under evaporation is still a challenge, especially to evaluate the droplet temperature. A promising technique is rainbow refractometry, which determines instantaneously the refractive index (temperature) and size of fuel droplets by characterizing the light distribution around the rainbow angle. As for other techniques, recorded signals must be efficiently processed to extract relevant information. This paper is devoted to the description of a new powerful processing strategy including the ripple structure which permits to increase the measurement accuracy. The algorithm has also been successfully applied to experimental rainbow signals recorded at ONERA-Toulouse with a special attention devoted to the measurement of ethanol droplets.