| This thesis is centered on Rainbow Refractometry, an optical measurement technique capable of measuring droplet temperatures within a spray. This study accomplishes three goals. First, the capabilities and limitations of the Rainbow Refractometer, as applied to an actual spray (a multi-size, poly-disperse spray), are determined. Second, alternative approaches to enhance the measurement technique, which include the development of a new filtering technique and the indirect application of the Lorenz-Mie Theory, are presented. These alternative approaches are intended to increase the accuracy, resolution and precision, as well as simplify and increase the efficiency of the data processing. The third goal is to perform and present actual droplet temperature measurements of various multi-sized, poly-disperse sprays. These first-of-its-kind measurements provide insight into the heat and mass transfer associated with sprays as well as information into the capabilities of the measurement technique.; There are two significant advances in Rainbow Refractometry that are contained in this thesis. First, a new filtering technique used in filtering the raw rainbow signal has been proposed. In this technique, the diameter determined by the PDPA is used to determine the appropriate filtering parameters. The PDPA diameter based filtering technique offers a more precise method of obtaining the "pure" supernumerary arcs from the measured light intensity signal and is less susceptible to potential distortions in the measured signal.; Second, a method of indirectly applying the Lorenz-Mie Theory, which is the exact solution to the rainbow scattering problem, has been proposed. This indirect method uses tabulated data, generated by the Fourier Lorenz-Mie Theory (FLMT), to determine the droplet refractive index and size. This proposed method has been shown to be an effective method of determining droplet refractive index and diameter. The Airy Theory, which has been the use in Rainbow Refractometry, is only an approximation of the actual rainbow scattering problem. It was discovered that the PDPA/Rainbow diameter comparison methodology, which is used to eliminate erroneous measurements, has a tendency to eliminate droplets with higher refractive indices when the Airy Theory is used. This tends to bias the measurements towards droplets with lower refractive indices. |
