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Viewing 1 to 30 of 547
2012-10-22
Journal Article
2012-01-2236
Edward Dawidowicz, Thomas Podlesak, Fee Leung
The effectiveness of elements comprising a hybrid electric power generating system was studied. The wind and photovoltaic renewable resources served as integral components of the hybrid systems configuration. A HMMWV towable trailer system provided an intermediary basis for formulation of methodology needed for optimization of power generation and energy storage capacity constrained by cost, size and weight of the system. The methodology employed in this paper is scalable from kilowatts to megawatts or from man portable systems to significantly larger systems which can be housed in 40 foot ISO containers.
2012-10-22
Technical Paper
2012-01-2237
Julianne Douglas, Michael Zalewski, Jorge-Luis Romeu
Although important, decreasing soldier burden does not begin and end with energy density and fuel consumption. Power transmission is a heavy endeavor at low voltage. For a typical Army squad or platoon's electronic devices' operating voltages of 12 or 24/28Vdc, distributing one kilowatt (kW) of power means that the high amperages require sets of cable up to an inch in diameter and weighing nearly one pound per foot. More than 10 or 20 yards of copper cable can require a team lift. With new focus on decreasing soldier burden, reducing fuel consumption, and reducing cost savings, various alternatives are being considered for one traditionally costly endeavor: powering the myriad of electronic devices that the warfighter uses. With power generation at a distance from the loads (radios, lights, chargers, etc), the power distribution cable weight, cost and power losses become a significant issue.
2012-10-22
Technical Paper
2012-01-2238
Donald J. Kessler
This paper presents an investigation into the feasibility of utilizing commercial off the shelf (COTS) components to implement an optically linked embedded electromechanical actuator (EMA) for aircraft flight control. A joint 1990s USAF, USN, NASA Electrically Powered Actuator Design (EPAD) program sought to replace hydraulically powered aircraft actuators with those powered electrically, either Electrohydrostatic (EHA) or Electromechanical (EMA). A follow-on NASA research effort in 1992 sought to then replace the electrical control links associated with the EHA/EMA with fiber-optic technology [1][2]. Attempts at implementing an optically-linked EMA while successful, experienced technical challenges and exposed fundamental limitations and shortfalls in some of the COTS technologies available at that time.
2012-10-22
Technical Paper
2012-01-2230
Yeong-Ren Lin, Yang Hu, Lei Zhou, David Woodburn, Thomas Wu, Louis C. Chow, Quinn Leland
In the aviation community, there is a high priority to develop all-electric aircraft. Electro-mechanical actuation systems would replace traditional, large, heavy and difficult-to-maintain hydraulic actuation systems. This movement from hydraulic actuation to electrical actuation enhances the flexibility to integrate redundancy and emergency system in future military aircraft. Elimination of the hydraulic fluid removes the possibility of leakage of corrosive hydraulic fluid and the associated fire hazard, as well as environmental concerns. The switch from hydraulic to electrical actuation provides additional benefits in reduced aircraft weight, improved survivability and improved maintainability. The heat load in an electro-mechanical actuation (EMA) is highly transient and localized in nature; therefore a phase change material could be embedded in the heat generating components to store peak heat load.
2012-10-22
Technical Paper
2012-01-2232
Yang Hu, David Woodburn, Yeong-Ren Lin, Thomas Wu, Louis C. Chow, Quinn Leland
In all-electric aircraft, electromechanical actuators (EMAs) will be used to replace hydraulic actuators. Due to the highly transient mission profiles of the aircraft operation, thermal management of EMAs is a significant issue. In this paper, we study the heat problem of the control and drive units of EMAs, and build a model to calculate and simulate the power loss and heat generation in the driver board. The driver unit consists of a power inverter, a capacitor, a power dissipating resistor and a control circuit. The power loss of each component is studied. The heat loss in the power inverter comes mainly from the power switches: IGBTs. The on-state loss is proportional to the current of the motor, and the switching loss is determined by the switching frequency as well as current.
2012-10-22
Technical Paper
2012-01-2183
Michael Ballas, Fred Potter
The development of the microprocessor controlled power MOSFET switch, as a circuit protection device for aircraft electrical power systems, has led to significant improvements in packaging, performance and thermal efficiencies over traditional thermal/mechanical systems. The electronic circuit breaker (ECB) inherently provides multiple functions (protect, sense, diagnose, and control). Employing the ECB as a “live” switching element in the system for active control, provides for significant integration of functions, previously requiring separate LRUs, additional wiring and more power to operate. This paper proposes an optimized electrical power distribution via intelligent control of electronic circuit breakers to provide maximum integration of existing utility management functions (i.e. window heat, de-icing, thrust reversers, etc.), reduction in aircraft wiring, reduced system weight and complexity.
2012-10-22
Technical Paper
2012-01-2186
Weibo Chen, David W. Fogg, Michael Izenson, Cable Kurwitz
Future electronics and photonics systems, weapons systems, and environmental control systems in aircraft will require advanced thermal management technology to control the temperature of critical components. Two-phase Thermal Management Systems (TMS) are attractive because they are compact, lightweight, and efficient. However, maintaining stable and reliable cooling in a two-phase flow system presents unique design challenges, particularly for systems with parallel evaporators during thermal transients. Furthermore, preventing ingress of liquid into a vapor compressor during variable-gravity operation is critical for long-term reliability and life. To enable stable and reliable cooling, a highly stable two-phase system is being developed that can effectively suppress flow instability in a system with parallel evaporators. Flow stability is achieved by ensuring that only single-phase liquid enters the evaporators.
2012-10-22
Technical Paper
2012-01-2184
Michael Baldwin
This paper will illustrate how the increasing electrical demands to power military and aerospace applications can successfully be met by high performance electromechanical relays. To meet these higher demands engineering compatibility must be properly understood between the intended application and relay switching performance parameters. With high performance electromechanical relays continuing to play a critical part in military and aerospace applications it is more important than ever before that engineers capture all of the military and aerospace electrical power requirements. A critical area within powering military and aerospace systems is capacitive load switching. Capacitive loads can generate high current levels that are transient in duration and adversely affect the relay at the component level and the military or aerospace applications at the higher systems levels. As capacitance increases the amplitude and duration of the current transient also increase.
2012-10-22
Technical Paper
2012-01-2189
Brian P. Tucker, Joseph Homitz, Janelle Messmer
High power levels and high power densities associated with directed energy weapon systems, electronic warfare systems, and high thrust-to-weight aircraft propulsion systems require the development of effective and efficient thermal management solutions. As the objective for many high-power electronic systems is integration onto mobile platforms, strict requirements are also placed on the size, weight, and power draw of the corresponding thermal management system. High peak waste heat loads cannot be efficiently rejected to ambient air in a package integrated onto a mobile platform, leading to the need to store large amounts of energy in a compact, lightweight package. Thermal storage devices must not only be able to store energy rapidly at high power levels but they must also reject energy efficiently, allowing the thermal storage device to recharge for multiple uses.
2012-10-22
Technical Paper
2012-01-2187
Larry Byrd, Andrew Cole, Stephen Emo, Jamie Ervin, Travis E. Michalak, Victor Tsao
The Air Force Research Laboratory (AFRL), in cooperation with the University of Dayton Research Institute (UDRI) and Fairchild Controls Corporation, is operating an in-house advanced vapor compression refrigeration cycle system (VCS) test rig known as ToTEMS (Two-Phase Thermal Energy Management System). This test rig is dedicated to the study and development of VCS control and operation in support of the Energy Optimized Aircraft (EOA) initiative and the Integrated Vehicle ENergy Technology (INVENT) program. Previous papers on ToTEMS have discussed the hardware setup and some of the preliminary data collected from the system, as well as the first steps towards developing an optimum-seeking control scheme. A key goal of the ToTEMS program is to reduce the risk associated with operating VCS in the dynamic aircraft environment.
2012-10-22
Technical Paper
2012-01-2173
Kevin McCarthy, Alex Heltzel, Eric Walters, Richard Deitrich, Justin Coffey, Sam Septembre, Michael McGonigle
Advanced tactical aircraft and their propulsion systems produce an order of magnitude more heat than legacy designs and offer fewer viable heat rejection opportunities. The current approach uses aircraft fuel as a primary heat sink which is either cooled by ram air and returned to the aircraft, or rejected off the aircraft when burned by the engine. Traditionally, aircraft have been limited in mission capability by the design performance and the available fuel quantity; however, potential thermal limitations have presented a new mission challenge. Joker and bingo range notifications based on fuel quantity remaining are common on modern fighters to ensure the pilot has the foresight to complete a mission segment and return to base before running out of fuel. Now, pilots may need to consider the possibility of a similar thermal joker/bingo concept until alternative LO heat rejection methods are discovered that remove limitations.
2012-10-22
Technical Paper
2012-01-2172
Megan Kania, Justin Koeln, Andrew Alleyne, Kevin McCarthy, Ning Wu, Soumya Patnaik
Modern air vehicles face increasing internal heat loads that must be appropriately understood in design and managed in operation. This paper examines one solution to creating more efficient and effective thermal management systems (TMSs): vapor cycle systems (VCSs). VCSs are increasingly being investigated by aerospace government and industry as a means to provide much greater efficiency in moving thermal energy from one physical location to another. In this work, we develop the AFRL (Air Force Research Laboratory) Transient Thermal Modeling and Optimization (ATTMO) toolbox: a modeling and simulation tool based in Matlab/Simulink that is suitable for understanding, predicting, and designing a VCS. The ATTMO toolbox also provides capability for understanding the VCS as part of a larger air vehicle system. The toolbox is presented in a modular fashion whereby the individual components are presented along with the framework for interconnecting them.
2012-10-22
Technical Paper
2012-01-2168
Rebekah Lee Puterbaugh, Jeffrey Brown, Ryan Battelle
Recent turbine engine numerical modeling developments have significantly improved the capability to accomplish integrated system-level analyses of aircraft thermal, power, propulsion, and vehicle systems. Combining desired aircraft performance with thermal management challenges of modern aircraft, which include increased heat loads from components such as avionics and more-electric accessories, as well as maintaining engine components at specified operating temperatures, demands we look for solutions that maximize heat sink capacity while minimizing adverse impacts on engine and aircraft performance. Development of optimized aircraft thermal management architectures requires the capability to directly analyze the impact of thermal management components, such as heat exchangers, on engine performance. This paper presents a process to evaluate the impact of heat exchanger design and performance characteristics (e.g., volume and pressure drops) on engine performance.
2012-10-22
Technical Paper
2012-01-2169
Hitoshi Oyori, Noriko Morioka, Daiki Kakiuchi, Yukio Shimomura, Keisuke Onishi, Fumito Sano
This paper describes a study on electrical power management for the More Electric Aircraft (or MEA) and the More Electric Engine (or MEE). This study explored power management solutions based on an integrated engine/power control system and a permanent magnet motor. In recent years, electrical power management has emerged as a key aspect of aircraft system design. In cases in which the Electromechanical Actuator (or EMA) systems are used for flight control, the power bus systems must also be designed to dissipate the power regenerated from flight control systems. In their study, the authors focused on achieving an optimal balance between aircraft power management and operational requirements of the aero-engines. The study results suggest an effective and novel power control concept based on integrated engine control technologies that ensure stable power systems.
2012-10-22
Technical Paper
2012-01-2170
Alex J. Heltzel, Kevin McCarthy, Soumya Patnaik
Although computational fluid dynamics (CFD) simulations have been widely used to successfully resolve turbulence and boundary layer phenomena induced by microscale flow passages in advanced heat exchanger concepts, the expense of such simulations precludes their use within system-level models. However, the effect of component design changes on systems must be better understood in order to optimize designs with little thermal margin, and CFD simulations greatly enhance this understanding. A method is presented to introduce high resolution, 3-D conjugate CFD calculations of candidate heat exchanger cores into dynamic aerospace subsystem models. The significant parameters guiding performance of these heat exchangers are identified and a database of CFD solutions is built to capture steady and unsteady performance of microstructured heat exchanger cores as a function of the identified parameters and flow conditions.
2012-10-22
Technical Paper
2012-01-2161
Blake A. Moffitt, Rachid Zaffou
Over the past decade, fuel cell systems have begun to appear as both primary and auxiliary power sources for aircraft. Fuel cells enable quiet electric aircraft with endurances that exceed equivalent battery powered vehicles, but have been limited to efficient fixed-wing aircraft due to low fuel cell power-to-weight ratios. This paper begins by discussing polymer electrolyte membrane fuel cell (PEFC) advancements at United Technologies Corporation (UTC) that have resulted in a significant increase in both the power-to-weight and power-to-volume ratios of fuel cell systems. As a result of these advances, UTC PEFC systems can now enable longer endurance missions for smaller UAVs as well as be considered for electric aircraft requiring vertical takeoff and landing capability. The move into vertical takeoff for electric aircraft is of particular interest as capabilities such as hover, perch and stare, and runway independence are enabled.
2012-10-22
Technical Paper
2012-01-2162
Scott L. Swartz, Gene B. Arkenberg, Joshua S. Emerick, Chad T. Sellers, Lora B. Thrun
NexTech Materials is developing sulfur tolerant solid oxide fuel cell stacks for military applications in the 1 to 10 kW range, including unmanned aerial vehicles. NexTech's stacks are based on its patented “FlexCell” planar cell design. There are several unique attributes associated with this design and NexTech's associated planar stack technology, including sulfur tolerance that facilitates the use of military logistic fuels, and high single-pass fuel utilization that enables high overall stack (and system) efficiency. This paper will describe the status of NexTech's SOFC stack technology, stack-level demonstrations of sulfur, and current development initiatives.
2012-10-22
Technical Paper
2012-01-2226
Jeff Knowles
Given the goal of developing energy-optimized aircraft that employ increasingly higher power loads such as electric flight control actuation, directed energy weapon systems and on-demand cooling systems, advances in battery technology and associated integration methodology will be required to achieve a robust electrical power system design. Batteries based on various Lithium-Ion chemistry technologies represent a 50% improvement in both specific energy and specific power over legacy NiCad and Lead-Acid chemistries. However, along with these benefits come challenges in terms of overall safety, cost and availability. Safety considerations primarily include failure modes that result from the battery being subjected to short-circuit conditions and over-charge conditions. Cost and availability challenges arise primarily from one-off point designs and ensuing low production volumes, but also stem from limited marketplace competition.
2012-10-22
Technical Paper
2012-01-2214
Marco Amrhein, Jason Wells, Thomas Baudendistel
Electric actuation on aerospace platforms has significant advantages compared to its hydraulic counterparts, particularly in terms of enhanced reliability, reduced maintenance, advanced diagnostic/performance capabilities, and possibly reduced weight and cost. It is thus not surprising that military and commercial aerospace sectors are introducing more electrical actuation architectures. A logical continuation of this trend is the replacement of hydraulic utility actuators in applications with harsh environments such as wide-range ambient temperatures and high vibration, where hydraulic actuation is still dominating. Such environments provide new challenges to the design of electric actuators, particularly considering that performance, weight, volume, and cost should be competitive with the equivalent hydraulic systems.
2012-10-22
Technical Paper
2012-01-2212
Jennifer C. Shaw, Stuart Galloway, Patrick Norman, Graeme Burt
NASA has compiled a set of research goals for five year periods starting 2015, 2020 and 2025 for three classes of future subsonic aircraft, N+1 (2015), N+2 (2020) and N+3 (2025). With the intention of progressively making reductions in noise emissions, greenhouse gas emissions, fuel burn and energy consumption at each of these points to achieve Technology Readiness Levels (TRL's) of between 4 and 6. In the last few years much progress has been made towards achieving these goals through the development of new technologies and designs. This paper assesses how the current More Electric Aircraft (MEA) design concepts are advancing to allow the near term, N+1 goals of reducing 32 dB of noise emissions, 60% of the landing and take-off (LTO) NOx emissions, 55% of cruise emissions and 33% saving of fuel burn and energy consumption, relative to single aisle B737-800, could be met and eventually surpassed.
2012-10-22
Technical Paper
2012-01-2213
Zhenning Liu, Randy Fuller, Wayne Pearson
There is a growing need for high voltage direct current (HVDC) power distribution systems in aircraft which provide low-loss distribution with low weight. Challenges associated with HVDC distribution systems include improving reliability and reducing the size and weight of key components such as electric load control units (ELCUs), or remote power controllers (RPCs) for load control and feeder protection, and primary bus switching contactors. The traditional electromechanical current interrupting devices suffer from poor reliability due to arcs generated during repeated closing and opening operations, and are generally slow in isolating a fault with potentially high let-through energy, which directly impacts system safety.
2012-10-22
Journal Article
2012-01-2211
Terrill B. Atwater, Paula Tavares
The benefits of lithium battery systems lie within their high energy density (Wh/L) and high specific energy (Wh/kg). Manganese dioxide (MnO2) is an attractive active cathode material because of its high energy density and low material cost. Manganese dioxide is an intercalating compound for lithium that functions by solvating and desolvating lithium cations from the electrolyte in solid state. The lithium cations are deposited into the vacancies of the MnO2 cathode crystal structure. The objective of this effort focuses on the limited cycle life of rechargeable lithium manganese-based electrochemical systems, most importantly capacity fading of the cathode. These two characteristics are considered the major technology hurdles in rechargeable lithium battery technology.1, 2, 3, 4
2012-10-22
Journal Article
2012-01-2200
David A. Wetz, Biju Shrestha, Peter M. Novak
The desire of the US Department of Defense (DoD) to field new directed energy systems for a variety of applications increases daily. This desire stems from recent advances in energy storage and solid-state switch technologies, which enable researchers to make systems more compact and energy dense than ever before. While some systems can draw power from the mobile platform on which they are mounted, other systems need to operate independent of a platform and must be completely self-sufficient. The transient and repetitive operation of these directed energy systems requires that the prime energy source provide high power to intermediate energy storage devices. The ability of electrochemical energy storage devices, such as lithium-ion batteries, to source high power quickly has previously been limited. However, battery manufacturers have recently produced cells that are more power dense then previously available.
2012-10-22
Journal Article
2012-01-2209
Brice R. McPherson, Robert Shaw, Jared Hornberger, Alex Lostetter, Roberto Schupbach, Brad Reese, Ty McNutt, Takukazu Otsuka, Yuki Nakano, Takashi Nakamura
The demands for high-performance power electronics systems are rapidly surpassing the power density, efficiency, and reliability limitations defined by the intrinsic properties of silicon (Si)-based semiconductors. The advantages of silicon carbide (SiC) are well known, including high temperature operation, high voltage blocking capability, high speed switching, and high energy efficiency. These advantages, however, are severely limited by conventional power packages, particularly at temperatures higher than 175°C and ≻100 kHz switching speeds. Here, APEI, Inc., presents the design process and testing data of its newly developed high performance HT-2000 SiC power module for extreme environment systems and applications.
2012-10-22
Technical Paper
2012-01-2203
Street A. Barnett, Zachary Lammers, Benjamin Razidlo, Quinn Leland, Justin DelMar
An Electromechanical Actuation System (EMAS) are an important component for an all electric Aircraft. EMAS would be lighter and require less system maintenance and operational costs than hydraulic actuators, typically used in aircraft systems. Also, hydraulic actuation systems require a constant power load to maintain hydraulic pressure, whereas EMAS only use power when actuation is needed. The technical challenges facing EMAS for aircraft primary flight control includes jam tolerance, thermal management, wide temperature range, high peak electric power draw, regenerative power, installation volume limit for thin wings, etc. This paper focuses on a laboratory test setup to simulate EMAS flight control environment to test and evaluate three important performance parameters of EMAS; thermal management, transient peak power draw, and regenerative power.
2012-10-22
Technical Paper
2012-01-2210
Steve Majerus, Daniel Howe, Steven Garverick, Walt Merrill, Kenneth Semega
Four application specific integrated circuits (ASICs) which provide sensing, actuation, and power conversion capabilities for distributed control in a high-temperature (over 200°C) environment are presented. Patented circuit design techniques facilitate fabrication in a conventional, low-cost, 0.5 micron bulk Complimentary Metal Oxide Semiconductor (CMOS) foundry process. The four ASICs are combined with a Digital Signal Processor (DSP) to create a distributed control node. The design and performance over temperature of the control system is discussed. Various applications of the control system are proposed. The authors also discuss various design techniques used to achieve high reliability and long life.
2012-10-22
Journal Article
2012-01-2208
Dennis P. Shay, Clive A. Randall
Mn and/or rare earth-doped xCaTiO₃ - (1-x)CaMeO₃ dielectrics, where Me=Hf or Zr and x=0.7, 0.8, and 0.9 were developed to yield materials with room temperature relative permittivities of Εr ~ 150-170, thermal coefficients of capacitance (TCC) of ± 15.8% to ± 16.4% from -50 to 150°C, and band gaps of ~ 3.3-3.6 eV as determined by UV-Vis spectroscopy. Un-doped single layer capacitors exhibited room temperature energy densities as large as 9.0 J/cm₃, but showed a drastic decrease in energy density above 100°C. When doped with 0.5 mol% Mn, the temperature dependence of the breakdown strength was minimized, and energy densities similar to room temperature values (9.5 J/cm₃) were observed up to 200°C. At 300°C, energy densities as large as 6.5 J/cm₃ were measured. These observations suggest that with further reductions in grain size and dielectric layer thickness, the xCaTiO₃ - (1-x)CaMeO₃ system is a strong candidate for integration into future power electronics applications.
2012-10-22
Technical Paper
2012-01-2190
Douglas Johnson, Soumya Patnaik, Jamie Ervin
In this work we present our recent effort in developing a novel heat exchanger based on endothermic chemical reaction (HEX reactor). The proposed HEX reactor is designed to provide additional heat sink capability for aircraft thermal management systems. Ammonium carbamate (AC) which has a decomposition enthalpy of 1.8 MJ/kg is suspended in propylene glycol and used as the heat exchanger working fluid. The decomposition temperature of AC is pressure dependent (60°C at 1 atmosphere; lower temperatures at lower pressures) and as the heat load on the HEX increases and the glycol temperature reaches AC decomposition temperature, AC decomposes and isothermally absorbs energy from the glycol. The reaction, and therefore the heat transfer rate, is controlled by regulating the pressure within the reactor side of the heat exchanger. The experiment is designed to demonstrate continuous replenishment of AC.
2012-10-22
Technical Paper
2012-01-2198
Marshall Soares, Michael Brown, Richard Rea
Full computational systems are needed at extreme environments (to 300°C) to increase functionality and reduce cost in the ever advancing aerospace, oil and gas, geothermal, and automotive industries. Some suppliers have developed components designed specifically for extreme environments only to find market volumes too small to support the development cost. Low volumes and high cost have limited the choices available to the system designer. Design paradigms for extreme environment suppliers must be altered to address the variety of industry requirements in a cost conscious manner. Designing with extreme environment technology restricts the complexity of a design, not the flexibility. A case study of memory and microcontroller components designed specifically for the extreme environments illustrating development tradeoffs favoring lowering cost and improved flexibility is presented.
2012-10-22
Technical Paper
2012-01-2192
F.Javier Fernandez-Garcia, Javier Valdeolmos
Today's civil airliners integrate electrical power capability properly sized to supply the growing demands of modern aircraft systems, that are more electrical than ever. The conversion of civil aircraft into a military derivative aircraft faces the challenge of rearranging the available generation capability to feed the new power-hungry military systems while at the same time minimizing the impact on certification of the base aircraft for use on civil operations. This challenge is particularly difficult when the new military systems demand high peak power consumption, as in the case of the conversion of a civil airliner into a military Multi-Role Transport Tanker aircraft with high performance multipoint refueling capabilities. In fact the selection of the type of actuation (either electrical or hydraulic) for the refueling systems is heavily conditioned by the excess of either electrical or hydraulic power available in the base aircraft.
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