Optical and laser diagnostics : The versatility of Imaging

Optical and laser diagnostics is a field where optical techniques are developed that offer remote, non-intrusive measurements in order to characterise a system. Imaging is a big part of this field and the versatility it offers makes it a great tool in the hands of researchers and in practical applications. In this thesis, multiple applications of imaging are presented, together with possible data processing routines that are used to obtain qualitative and quantitative information. Intuitive ways of presenting big datasets along with trends and variations in them are shown, for both, time-resolved and single-shot measurements. Efforts to enhance the efficiency of internal combustion engines are discussed and a study on the interaction of spray jets and prevailing combustion in light-duty diesel engines is shown. A thorough optical investigation of methanol combustion in compression ignition engines is presented, along with a characterisation of the injection process and fuel distribution for methanol inside a heavy-duty optical engine. The potential of methanol as a renewable fuel and energy carrier is discussed in a wider perspective, together with demonstrating the benefits of such a propulsion system. In addition, a study of exhaled respiratory particles is presented, in an attempt to characterise the potential for transmission of diseases through the respiratory tract. This consisted of an evaluation of everyday tasks such as talking and singing, which is not commonly found in the literature as most studies are focused on sneezing and coughing. Finally, a novel approach on Background Oriented Schlieren, known as Laser Speckle-based BOS, is presented together with some preliminary results. There is great potential for this technique to be used in combustion engine diagnostics, as it requires minimal optical access to create the pattern and the sensitivity of the setup relies less on the distance of the subject to the background pattern