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Title:Physicochemical and performance study of next generation alternative jet fuels
Author(s):Oldani, Anna Lucrezia
Director of Research:Lee, Tonghun
Doctoral Committee Chair(s):Lee, Tonghun
Doctoral Committee Member(s):Wagoner Johnson, Amy J.; Rodríguez, Luis; Wissa, Aimy
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):alternative energy
jet fuel
fuel database
Abstract:This work examined the physicochemical properties of aviation fuels and their impact on combustion performance in relevant applications for existing and emerging engine architecture with a particular focus on next generation alternative jet fuels (AJF). The Federal Aviation Administration (FAA) Center of Excellence for Alternative Jet Fuels and Environment (ASCENT) identified fuel property variability and low temperature, lean fuel environments as key to AJF integration. To accomplish these goals, a national archive of jet fuel property and test data was established as a starting point to collect disparate jet fuel research that has been completed over recent decades. With this assembled data collection, statistical analyses were conducted on the dataset to establish new physicochemical property correlations for AJFs and to identify fuel features to target in subsequent experimental testing. This testing revealed further insights into unique autoignition phenomena, pertinent to supporting the expansion of AJF integration into current aviation fuel systems. Chemical kinetics simulations and reaction chemistry evaluations supplemented this experimental data and allowed a deeper analysis into the influence of fuel composition on resulting performance. This new knowledge can accelerate AJF development by facilitating efforts to streamline existing fuel certification processes through an enhanced understanding of the relations between fuel makeup and performance to optimize fuel blending strategies. In the initial stage of this effort, the Alternative Jet Fuel Test Database (AJFTD) was developed as a centralized knowledgebase for the aviation research community. Fuel test data, technical reports, and chemical kinetic mechanisms from academic, government, and industry research groups were assembled into this data repository. It contains pertinent approval testing and specification property results for conventional and approved alternative jet fuels. To facilitate the analysis of this data, a non-relational (NoSQL) database was constructed that contains unique JavaScript Object Notation (JSON) files for each fuel classified by a singular identification number (POSF) as assigned by the Air Force Research Laboratory (AFRL) or other fuel testing information for fuels lacking a POSF designation. The multi-year AFJTD project continues to evolve, serving as a valuable resource to disseminate aviation data from development to end-use. With the data processed into a more readily accessible format, new analyses on the considerable collection of jet fuel test data were performed that were previously unattainable. This included statistical analyses of the variability present in conventional and alternative jet fuels for specification properties. These property distributions illustrate both the existing jet fuel landscape and the differences across approved AJF types. This can inform future efforts to annex additional AJFs and provide guidelines to evaluate new fuels against the current fuel experience base. New AJF thermophysical relations were developed utilizing AJFTD resources to provide property estimations as a starting point for fuel pre-screening efforts. The relations focused on specification properties, providing a method for early identification of fuels with high certification likelihood while also identifying fuels with problematic features. These variability and correlation analyses demonstrate the need for AJF continued testing to create robust datasets for use in such evaluations. Following the evaluation of physicochemical properties and fuel variability, experimental tests and kinetic simulations were done to further examine fuel features of particular interest for AJF blending and performance in key environments. Fuel testing involved rapid compression machine (RCM) and shock tube (ST) experiments to evaluate fuel autoignition phenomena. Testing focused on low to intermediate temperatures for fuel lean to stoichiometric conditions at varying pressure rates, relevant to engine applications. These conditions highlighted unique multi-stage ignition profiles, varying negative temperature coefficient (NTC) trends, and key fuel reactivity differences. The experimental results prompted further inquiry, and chemical kinetics simulations were conducted to elucidate the principal reaction chemistry responsible for the observed ignition properties. The combined experimental testing and autoignition modeling data provided key insight into the influence of chemical composition on resulting fuel performance for both neat and blended conventional and alternative jet fuels. In summary, the following work has made a wealth of relevant jet fuel data accessible to the aviation and combustion research communities and has generated novel property relations with a focused examination of unique alternative fuel autoignition. The establishment of the first national archive of jet fuel testing data is a major step towards enabling the advanced development and deployment of alternative fuels into current operations. Using this database, physicochemical property correlations were determined to identify relations across fuel composition and combustion characteristics in an effort to elucidate factors that can predict engine testing results. Current conventional fuel data was analyzed and new thermophysical relations for AJFs were developed to better assess the variability across fuel categories. This knowledge can then facilitate pre-screening efforts of fuels currently in the development pipeline. Finally, novel fuel testing and autoignition analyses expanded the current knowledge of fuel performance in unique combustion conditions. These combined efforts deepen the critical understanding of the relationship between prominent fuel physical and chemical characteristics and key combustion performance parameters. This research enables future development and integration of alternative fuel options. Successful deployment of these fuels will help to secure domestic energy resources, mitigate fuel price volatility, provide skilled jobs to the national economy, lessen the environmental impact of aviation fuels, and ensure fuel performance in current and next generation engine technologies.
Issue Date:2019-04-08
Rights Information:Copyright 2019 Anna Lucrezia Oldani
Date Available in IDEALS:2019-08-23
Date Deposited:2019-05

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