Preignition is an ignition event that happens before it is expected and, many times, where it is not expected to happen. Understanding this phenomenon is of great importance as it influences the design and operation of modern downsized boosted internal combustion engines. In this thesis, a comprehensive study of the preignition tendency of various chemical systems is presented. Firstly, renewable fuels like ethanol, methanol and a surrogate of conventional fuels, n-hexane, are characterized by traditional shock tube techniques, such as the measurements of ignition delay times and pressure-time histories, to identify thermodynamic conditions which promote non-ideal ignition behavior. End-wall high-speed imaging was implemented to visualize the combustion process taking place inside the shock tube. In order to carry out detailed characterization of the ignition homogeneity or the lack-thereof, a novel imaging section was designed which enabled simultaneous lateral and endwall imaging by using a longitudinal slit window. This diagnostic strategy was implemented in both low- and high-pressure shock tube facilities. Various theories and criteria for the onset of preignition were tested in comparison to the experimental observations to propose an adequate predictor of non-ideal ignition phenomena in practical applications. A non-dimensional number, relating the ignition delay sensitivity and laminar flame speed of the mixtures, was found to be the best criterion to elucidate ignition regimes.
Miguel is a Ph.D. Candidate in Mechanical Engineering, member of the Chemical Kinetics and Laser Sensors Laboratory led by Prof. Aamir Farooq. He received his Bachelor's degree in Engineering Physics in 2012 and a Master's degree in 2014, both from Monterrey Institute of Technology and Higher Education in Mexico. His research interests revolve around the characterization of physicochemical systems. His work at KAUST is focused on the application of visualization techniques on the investigation of preignition in shock tubes and rapid compression machines.
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