Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Feasibility Analysis and FDS Modeling of Water Mist Fire Suppression Systems for Protection of Aircraft Hangars(2021) Steranka, Karolyn; Milke, James; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Concern about PFAS containing foam fire suppression agents’ negative environmental impact motivated the U.S. Air Force to perform a two-phase feasibility analysis of water mist systems for protection of aircraft hangars. Phase I involved a feasibility analysis of COTS water mist technologies based on manufacturer specifications, literature, and previous test data. Phase I identified seven manufacturers who have developed systems with potential for successful protection of aircraft hangars. Phase II used FDS to model two low pressure and one high pressure system identified in Phase I. Phase II completed an analysis and validation simulations of the Lagrangian particle, extinction, and evaporation model in FDS. Following validation simulations each nozzle was tested in a full-scale hangar configuration for protection of a JP-8 spill fire. The results found the high-pressure mist system was able to extinguish the fire and earlier activation times lead to less damage to the aircraft and hangar compartment.Item Guided Lamb Wave Structural Health Monitoring Techniques for Aircraft Applications(2019) McCullum, Jacob Ryan; Wereley, Norman M; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Growing aerospace industry interest in structural health monitoring (SHM) has led to the development of many damage detection and localization techniques which make use of guided Lamb Waves (GLW). To continue this growth, further development of these techniques is necessary with an industry-focused mindset through studies with realistic, complex aircraft structures. The present study applies GLW techniques to two aircraft structures and examines the feasibility of their use for practical SHM applications. Particularly this work focuses on evaluating the effects of complex structural features found in aircraft, examining the human interaction with GLW techniques, and enhancing GLW techniques using nontraditional dual PZT transducers. Several damage case studies are performed showing that damage can be detected and located, and limitations to the techniques are characterized. Moreover, the use of dual PZT transducers shows improvements to damage localization techniques which potentially enable greater flexibility for aircraft applications.Item Gas Turbine / Solid Oxide Fuel Cell Hybrids: Investigation of Aerodynamic Challenges and Progress Towards a Bench-Scale Demonstrator(2019) Pratt, Lucas Merritt; Cadou, Christopher P; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Modern aircraft are becoming more electric making the efficiency of on-board electric power generation more important than ever before. Previous work has shown that integrated gas turbine and solid oxide fuel cell systems (GT-SOFCs) can be more efficient alternatives to shaft-driven mechanical generators. This work advances the GT-SOFC concept in three areas: 1) It develops an improved model of additional aerodynamic losses in nacelle-based installations and shows that external aerodynamic drag is an important factor that must be accounted for in those scenarios. Additionally, this work furthers the development of a lab-scale prototype GT-SOFC demonstrator system by 2) characterizing the performance of a commercial off-the-shelf (COTS) SOFC auxiliary power unit that will become part of the prototype; and 3) combining a scaled-down SOFC subsystem model with an existing thermodynamic model of a small COTS gas turbine to create an initial design for the prototype.Item SUSTAINING THE PACIFIC CARRIER AIR WAR: THE DEVELOPMENT OF U.S. NAVAL AVIATION MAINTENANCE AND THE ENLISTED AIRCRAFT TECHNICIAN IN WORLD WAR II(2019) Fisher, Stanford Edward; Sumida, Jon T; History; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The ability of the United States Navy to fight a protracted war throughout the Pacific Ocean in World War II was not solely the result of technology, tactics, or admiralship. Naval aviation maintenance played a major role in the U.S. victory over Japan. Naval aviation leadership throughout the period between World War I and World War II focused on the improvement of technology and tactics rather than training a new, and in the event of war, necessarily large cohort of enlisted personnel. Aircraft maintenance was an afterthought for much of the era because of the small number of carriers and aircraft. When the United States realized a two-ocean naval war was imminent and a drastic increase in the size of its aviation fleet was ordered, the navy was forced to reconsider its earlier practices and forge new polices and processes. The U.S. naval air war against Japan did not achieve sustained success until enough aircraft technicians were in place to support the doctrine of the Fast Carrier Task Force. The United States Navy was not ready to fight a protracted war at sea until its carrier aircraft technicians were trained and in place. The historiography of U.S. naval warfare in the modern era lacks any comprehensive study on the subject of naval aviation maintenance. This dissertation demonstrates the importance of considering all elements of the military institution, not just those that correspond to operational-battle history when studying the full dimensions of modern naval war in the age of the aircraft carrier. Recognizing the drastic institutional changes that accompanied an increase in maintenance personnel from less than 10,000 to nearly 250,000 over four years, a complete restructuring of the aviation navy’s technical educational system, and the development of highly specialized skilled labor force on board the aircraft carrier are essential to creating a more complete historiography World War II naval warfare. Analyzing the effect that aircraft maintenance and the aircraft technician had on carrier warfare is an added layer to the complex study of war that should not be overlooked. Even in the era of modern-technologically advanced warfare, people still matter.Item APPLYING RELIABILITY ANALYSIS TO DESIGN ELECTRIC POWER SYSTEMS FOR MORE-ELECTRIC AIRCRAFT(2014) Zhang, Baozhu; Xu, Huan; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The More-Electric Aircraft (MEA) is a type of aircraft that replaces conventional hydraulic and pneumatic systems with electrically powered components. These changes have significantly challenged the aircraft electric power system design. This thesis investigates how reliability analysis can be applied to automatically generate system topologies for the MEA electric power system. We first use a traditional method of reliability block diagrams to analyze the reliability level on different system topologies. We next propose a new methodology in which system topologies, constrained by a set reliability level, are automatically generated. The path-set method is used for analysis. Finally, we interface these sets of system topologies with control synthesis tools to automatically create correct-by-construction control logic for the electric power system.