No description available.

No description available.

No abstract available.

Thesis (Ph.D.)--Tennessee Technological University, 2008. / Bibliography: leaves 175-192.

Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on Feb. 18, 2010). Includes bibliographical references.

Thesis (Ph. D.)--Lehigh University, 2005. / Includes bibliographical references and vita.

Thesis (M.S.)--University of Wisconsin--Madison, 1961. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 50-51).

Thesis (M.S. in Operations Research)--Naval Postgraduate School, September 2009. / Thesis Advisor(s): Nussbaum, Daniel A. "September 2009." Description based on title screen as viewed on November 6, 2009. Author(s) subject terms: Energy efficiency, fuel savings, cost of fuel, discount factor, prioritization listing, surface fleet. Includes bibliographical references (p. 37-38). Also available in print.

Submitted by Marcele Costal de Castro (costalcastro@gmail.com) on 2017-10-02T18:24:17Z No. of bitstreams: 1 JOÃO JACHIC D.pdf: 4694106 bytes, checksum: f610bf160c523083f77b7b3b8e752662 (MD5) / Made available in DSpace on 2017-10-02T18:24:17Z (GMT). No. of bitstreams: 1 JOÃO JACHIC D.pdf: 4694106 bytes, checksum: f610bf160c523083f77b7b3b8e752662 (MD5) Previous issue date: 1981 / This thesis describes the development of a fuel depletion strategy that maximizes cycle length in boiling water reactor (BWR) cores. The cycle length maximization problem was formulated in terms of a core reactivity maximization scheme which provided solution to a terminal state optimization problem as well as to the optimal depletion strategy search. The nonlinear optimization problem was solved through an iterative application of linear programming involving linearization of the objective function and constraint equations. The nuclear-thermal-hydraulic model representing BWR cores was solved in a fully coupled, nonlinear form outside of the linear programming algorithm. For our numerical study, a large BWR core was modeled through a finite-difference form of the axial one-dimensional, two group neutron diffusion equation with control rods and thermal-hydraulic feedback represented. The optimal terminal state that results in maximum cycle length at the end-of-cycle for a given fuel loading is obtained through two phases, involving burnup shape optimization and cycle length extension, respectively. The optimal fuel depletion strategy is obtained through optimization of control rod pattern such that the loss in core reactivity over each depletion interval is minimized subject to power distribution constraints. The maximum cycle length obtained in our one dimensional axial depletion calculation indicates an increase of 7.4% over the corresponding Haling result, suggesting potential improvement in fuel utilization through proper control poison management. We also conclude that both the optimal terminal state and the optimal depletion strategy strongly depend upon the power distribution constraints. The fuel cycle is extended at the expense of power peaking margin. The optimal terminal state results in a bimodal bottom-peaked burnup shape and a top-peaked power distribution with the power peaking factor at the design limit. The optimal depletion calculation shows that the optimal power distribution is bimodal and time dependent with, the peaking factor at the design limit. The optimal power distribution is more skewed than the traditional Haling shape and bottom-peaked for most of the fuel cycle. For a short time interval around a coreaverage burnup of 3 GWD/T the power distribution is toppeaked reflecting the high depletion rate of the distributed burnable poison.

This body of work investigated the influence of alternative jet fuel properties on aviation gas turbine performance at threshold combustor operating conditions. It focused on altitude blowout performance and was in part motivated by results that were encountered during an aviation industry evaluation of synthetic kerosene that complied with the Jet A-1 specification, but differed from the fuel that was used as a reference in terms of some significant properties. As a consequence the relative impact of physical properties and reaction chemistry properties were of primary interest in this study. The thesis considered the potential to blend a range of different alternative jet fuel formulations which exhibited independent variations in properties relating to evaporation and reaction behaviour whilst still conforming to legislated physical fuel specifications. It further explored the potential for said variations having a detectable and significant influence on the simulated high altitude extinction behaviour in a representative aviation gas turbine combustor. Based on the findings, appropriate metrics were suggested for scientifically quantifying the appropriate properties and conclusions were drawn about the potential impact of alternative jet fuel properties on blowout performance. These subjects were addressed primarily through the theoretical analyses of targeted experimental programmes. The experimental design adopted a novel approach of formulating eight test fuels to reflect real-world alternative fuel compositions while still enabling a targeted evaluation of the influences of both physical and chemical reaction properties. A detailed characterisation was performed of the test fuels' physical and reaction properties. The extinction and spray behaviours of the fuels were then evaluated in a laboratory scale combustor featuring dual-swirl geometry and a single prefilming airblast atomiser. The various experimental data sets were interpreted within the context of a theoretical model analysis. In doing so the relative performance of alternative jet fuel formulations under laboratory burner conditions were translated to predict relative real world altitude performance. This approach was validated against aforementioned industry evaluation results and demonstrated to be consistent. A technically defensible explanation was provided for the previously unexplored anomalous altitude extinction results that were observed during the industry evaluation of synthetic jet fuel. A conclusive case was made for the extinction limit differences having been caused by the relative differences in chemical ignition delays of the fuels. The probability of volatility (distillation profile) and fuel physical properties playing a significant role in the impaired altitude performance was discredited. Evaporation-controlled combustion efficiency was, however, shown to become a significant factor at low air mass flow rates or when the fuel evaporation is compromised. The influence of flame speed and chemical ignition delays were investigated. Laminar flame speed was shown not to correlate with LBO, discrediting its use as a proxy for reaction rate. The study showed a correlation between the lean blowout behaviour of jet fuels and the ignition delays associated with their derived cetane numbers. Additionally, there was substantive support indicating that an even stronger correlation could be obtained by operating the IQT™ device that is used to measure these delays at an elevated temperature. The thesis makes a contribution towards the development of both technical understanding and practical tools for evaluating the potential operating limits of alternative jet fuel formulations.