Ultrafast Imaging Of Fuel Sprays Development Of Optical Diagnostics Image Processing

Download or read book Ultrafast Imaging of Fuel Sprays : Development of Optical Diagnostics, Image Processing written by Harsh Purwar and published by . This book was released on 2015 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel atomization plays a very crucial role in determining the overall efficiency of diesel internal combustion engines. This work focuses on developing fast optical diagnostic tools for the study of the liquid fuel atomization with an aim to characterize the fuel sprays in the near-field of the injector nozzle. At first, classical imaging techniques using continuous illumination with a high-speed camera and an ultra-short pulsed illumination with a high-resolution CCD camera are reviewed. Next, the possibility of supercontinuum (SC) derived illumination is investigated. It was observed that the spray images obtained with such an illumination were almost free from laser speckle, which tremendously improved the clarity of these images. An application of the classical imaging technique to a preliminary study of cavitation inside a transparent injector is presented. In the next part of the thesis optical techniques to reduce the noise originating due to the multiple scattering of light from its interaction with the fuel spray are studied. Optical Kerr effect based time-gate in its primitive crossed-beam configuration is reviewed and a novel approach with collinear overlap of the pump and probe beams for time-resolved imaging of fuel spray with time resolution 1 ps is proposed. Ballistic images of fuel spray in the near-nozzle region with high spatial resolution are obtained. The possibility of using SCderived illumination with the optical time-gate configuration is also discussed. Preliminary time-gated spray images obtained by using SC-derived probe beam for spray illumination in the optical-gate setup shows that laser speckle is substantially reduced maintaining a similar time resolution. The change in the optical polarization properties of the Kerr medium on introduction of the pump pulse are completely characterized by measuring its Mueller matrix (MM). The polarization parameters - depolarization, diattenuation, and retardance are then quantified by decomposing the measured MM using polar decomposition formalism.