The purpose of this research is to develop a measurement system allowing the characterization of the diameter and the velocity of fuel droplets in sprays by laser anemometry. Knowing both these two parameters is indeed essential so as to characterize the properties of sprays generated in combustion systems with the view to improve the efficiency of air-fuel mixing and oxidation processes, but also to observe and study the differences induced by the use of a biofuel instead of a standard fossil fuel. To do so, laser anemometry has been used in order to perform local measurements in sprays. This technique consists in illuminating a specific region of the studied spray by means of two converging laser beams while collecting the scattered light using photodiodes connected to an acquisition card, the obtained signals being finally processed via a program developed with the Matlab® software. A literature review conducted as part of this work first summarized the theoretical elements governing the laser anemometry approach. This theoretical analysis also allowed identifying and comparing the different existing anemometry systems in order to have a broad vision of the possibilities provided by this technique. On the basis of this study, a standard Phase Doppler Anemometry (PDA) configuration with 3- detectors has been chosen due to the presence of a laser Doppler velocimeter (LDV) that, however, does not allow droplet size to be measured at the Thermo-Fluid for Transport (TFT) laboratory of École de Technologie Supérieure (ÉTS). A Matlab® code has then been developed to extract the relevant information (velocity and droplet diameter) from the signals detected by the photodiodes. The operating principle of the system developed has been validated through measurements made in a spray generated using a nebulizer used to inject distilled water. The results obtained have also been compared with those issued from the use of an ombroscopy technique. Difficulties have still been highlighted during this work (particularly regarding the limited sampling frequency of the acquisition card used) thus opening avenues for further works aiming at improving the system developed during this research.
Suel, P.-A. (Author),
Seers (Supervisor),
Lemaire (Co-supervisor) &
Belleau (Co-supervisor),
27 Nov 2019Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering