First principles based fuel design: investigating fuel properties and combustion chemistry

  • Ahfaz Ahmed

Student thesis: Doctoral Thesis


Advanced combustion engine concepts require fuels which are meticulously designed to harness full potential of novel engine technologies. To develop such fuels, better understanding of fuel properties and their effect on combustion parameters is needed. The investigations reported in this work establishes relationships between several fuel properties and combustion parameters at engine relevant conditions. Further, these findings along with conclusions from other studies are utilized to synthesize fuels and surrogate fuels with tailored combustion properties. This approach of designing fuels relies on constrained non-linear optimization of several combustion properties simultaneously to design surrogate fuels for transportation fuels to enable combustion simulations. This scheme of fuel design has been devised and presented as Fuel Design Tool in Ahmed et al. Fuel 2015. Detailed investigations have been made to understand the effect of fuel properties on the ignition of fuels in Rapid compression machines utilizing a custom built multi-zone model. The study was further extended to explore fuel effects on engine combustion utilizing experiments and modelling to gather understanding of instances of engine knocking and pollutant formation. Bio-blended fuels allow mitigation of harmful pollutants and also enables engines to operate at higher efficiency. Ignition characteristics of two high octane bio-blended gasolines were studied experimentally in rapid compression machine and shock tube and detailed chemical kinetic analysis was conducted to understand how the presence of biofuels (i.e., ethanol) in gasoline influences the evolution of important radicals controlling ignition. Another set of biofuels namely methyl acetate and ethyl acetate were studied employing fundamental experimental and computational methods. The investigation involved development and analysis of combustion chemistry models, speciation studies in jet stirred reactors, ignition delay measurements and determination of laminar burning velocities. These fuels are found suited for high performance advanced spark ignition engines and the developed model and analysis will lead to optimization of combustion performance. The developed fuel design tool along with enhanced understanding of combustion chemistry and fuel properties enables a complete toolkit ready to be utilized to develop fuels with better suited properties for the advanced combustion modes.
Date of AwardJul 2018
Original languageEnglish
Awarding Institution
  • Physical Science and Engineering
SupervisorWilliam Roberts (Supervisor)

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