Concentration and composition measurement of sprays with a global rainbow technique

Applications of the global rainbow technique to measure the concentration of a sprayed bi-component solution or the composition and the relative proportions of two sprays of different solutions at a local point are investigated. For a dual spray, the global rainbow signal is processed by optimally fitting the initial global rainbow signal with two global rainbow signals. For each composition, the value of the refractive index and size distribution is measured. In the case of spray mixing, the relative proportion of each composition can be retrieved from this information. The algorithms are validated by the processing of simulated global rainbows. Experimental rainbows of water-ethanol solutions with volume concentration from 0% to 100% and two sprays of water and ethanol are measured. The limitations of the global rainbow technique for concentration and composition measurements are discussed.