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Viewing 1 to 30 of 547
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
2012-01-2161
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
Journal Article
2012-01-2164
Clarence Lui, Matthew Dooley, Jacquelyn Duchene
The high electrical power demand and heat rejection characteristics of a high energy laser pose new challenges to airframe power and thermal system designers. Typically, the power demand requires additional power storage devices and electrical generator upsizing which will adversely impact the engine performance and installation envelope. The thermal system is complicated by an already limited onboard heat sink, resulting in a bulkier system. Utilizing conventional approaches, the aircraft will suffer from additional weight, less available installation volume, and lower overall performance. This paper presents a potential integrated power and thermal system with attributes to minimize aircraft penalty. The system is a collection of various integration techniques that will be discussed individually for potential standalone application.
2012-10-22
Journal Article
2012-01-2163
Michael J. Armstrong, Christine A. H. Ross, Mark J. Blackwelder, Kaushik Rajashekara
This paper outlines power system architecture trades performed on the N3-X hybrid wing body aircraft concept under NASA's Research and Technology for Aerospace Propulsion (RTAPS) study effort. The purpose of the study to enumerate, characterize, and evaluate the critical dynamic and safety issues for the propulsion electric grid of a superconducting Turboelectric Distributed Propulsion (TeDP) system pursuant to NASA N+3 Goals (TRL 4-6: 2025, EIS: 2030-2035). Architecture recommendations focus on solutions which promote electrical stability, electric grid safety, and aircraft safety. Candidate architectures were developed and sized by balancing redundancy and interconnectivity to provide fail safe and reliable, flight critical thrust capability. This paper outlines a process for formal contingency analysis used to identify these off-nominal requirements. Advantageous architecture configurations enabled a reduction in the NASA's assumed sizing requirements for the propulsors.
2012-10-22
Journal Article
2012-01-2166
Antonio Dumas, Michele Trancossi, Mauro Madonia
This paper presents a model of energetic consumption and photovoltaic production for a large airship which acts as feeder connecting the ground with a large cruiser. The analysis of energy needs and productivity allows defining both an ideal sizing and operative mission profiles. The specialised mission of this airship is to ascent and descent. It includes also the connection with the airport buildings on the ground and with the cruiser at high altitude. Photovoltaic production has evaluated in terms of hydrogen and electric propulsion. They have estimated both and a calculation methodology has proposed. The evaluation has supported by CFD evaluations on aerodynamic behaviour of the system at various altitudes.
2012-10-22
Journal Article
2012-01-2165
Michael J. Armstrong, Christine A. H. Ross, Mark J. Blackwelder, Kaushik Rajashekara
NASA's N3-X aircraft design under the Research and Technology for Aerospace Propulsion Systems (RTAPS) study is being designed to meet the N+3 goals, one of which is the reduction of aircraft fuel burn by 70% or better. To achieve this goal, NASA has analyzed a hybrid body wing aircraft with a turboelectric distributed propulsion system. The propulsion system must be designed to operate at the highest possible efficiency in order to meet the reduced fuel burn goal. To achieve maximum efficiency, NASA has proposed to use a superconducting and cryogenic electrical system to connect the electrical output of the generators to the motors. In addition to being more efficient, superconducting electrical system components have higher power density (kW/kg) and torque density (Nm/kg) than components that operate at normal temperature. High density components are required to minimize the weight of the electric propulsion system while meeting the high power demand.
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
Journal Article
2012-01-2167
Michael Corbett
Variable cycle engines offer the potential to operate a turbine engine more like a high-bypass turbofan during subsonic cruise and more like a turbojet or low-bypass turbofan for high-performance maneuvers or when supercruising. Variable geometry within the engine enables flow holding, allowing it to ingest the maximum amount of air that the inlet can capture even at reduced throttle settings. This approach reduces spillage drag compared to the conventional approach which cuts back engine airflow by reducing fan speed. To achieve the desired thrust, airflow is modulated between the core, inner bypass, and outer bypass. The air in the outer bypass duct, known as the 3rd stream, has been proposed as a heat sink for various engine and aircraft heat loads since it is at a comparatively low temperature, having only passed through the fan portion of the engine's compression system.
2012-10-22
Journal Article
2012-01-2155
Bernard L. Koff
The remarkable evolution of the gas turbine engine has made the world much smaller and provided power for worldwide use. I often think of growing up in a farm environment, being fascinated with machinery and then having the opportunity to take part in the design and development of the world's most complex product. I worked with brilliant engineers and experienced the transition from slide rules and “hand calculation” methods to computers and more precise finite element modeling. Perhaps this story will present insight for current and future design engineers who create the manufactured products used by mankind.
2012-10-22
Technical Paper
2012-01-2157
Serhiy Bozhko, Tao Yang, Greg Asher
The paper deals with the development of active front-end rectifier model based on dynamic phasors concept. The model addresses the functional modeling level as defined by the multi-layer modeling paradigm and is suitable for accelerated simulation studies of the electric power systems under normal, unbalanced and line fault conditions. The performance and effectiveness of the developed model have been demonstrated by comparison against time-domain models in three-phase and synchronous space-vector representations. The experimental verification of the dynamic phasor model is also reported. The prime purpose of the model is for the simulation studies of more-electric aircraft power architectures at system level; however it can be directly applied for simulation study of any other electrical power system interfacing with active front-end rectifiers.
2012-10-22
Journal Article
2012-01-2156
Patrick Norman, John Timothy Alt, Graeme Burt
Uncontrolled rectifiers are featured heavily in aircraft electrical power systems performing a number of the power conversion and conditioning functions. Detailed modeling and simulation of these and other converters as part of a wider aircraft power system, whilst accurate, can be very computationally intensive, resulting in impractically slow simulation speed. One potential solution to this issue is the use of average-value converter models, which offer a much lower computational requirement and can utilize larger time steps. Of the average-value diode rectifier modeling methods presented in the research literature the parametric method is particularly well suited to system-level simulation because it can be readily derived to represent all modes of rectifier operation. To date however, published results utilizing this methodology have been limited to simpler power system architectures.
2012-10-22
Technical Paper
2012-01-2159
Tao Yang, Greg Asher, Serhiy Bozhko
The more-electric aircraft (MEA) is the major trend for airplanes in the next generation. Comparing with traditional airplanes, a significant increase of on-board electrical and electronic devices in MEAs has been recognized and resulted in new challenges for electrical power system (EPS) designers. The design of EPS essentially involves in extensive simulation work in order to ensure the availability, stability and performance of the EPS under all possible operation conditions. Due to the switching behavior of power electronic devices, it is very time-consuming and even impractical to simulate a large-scale EPS with some non-linear and time-varying models. The functional models in the dq0 frame have shown great performance under balanced conditions but these models become very time-consuming under unbalanced conditions, due to the second harmonics in d and q axes. The dynamic phasor (DP) technique has been proposed to solve that problem.
2012-10-22
Technical Paper
2012-01-2158
Anthony Camarano, Thomas Wu, Mitch Wolff, Jon Zumberge
Preliminary investigations of nonlinear modeling of aircraft synchronous generators using neural networks are presented. Aircraft synchronous generators with high power density tend operate at current-levels proportional to the magnetic saturation region of the machine's material. The nonlinear model accounts for magnetic saturation of the generator, which causes the winding flux linkages and inductances to vary as a function of current. Finite element method software is used to perform a parametric sweep of direct, quadrature, and field currents to extract the respective flux linkages. This data is used to train a neural network which yields current as a function of flux linkage. The neural network is implemented in a Simulink synchronous generator model and simulation results are compared with a previously developed linear model. Results show that the nonlinear neural network model can more accurately describe the responsiveness and performance of the synchronous generator.
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
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
2012-01-2199
Roger Brewer
Abstract The value of “ultracapacitors” (also referred to as “supercapacitors” or “electric double layer capacitors” in some literature) as an augmentation device when placed in parallel with “electrochemical” energy storage (i.e. battery) is presented in this paper. Since ultracapacitors possess unique attributes due to their higher value of energy storage density (or Joules/WattHrs per mass) compared to conventional capacitors while maintaining the peak power providing capability (to some degree) typical of conventional capacitors they may provide a near term solution in applications demanding longer battery operating life when placed in parallel. Such demands may be pronounced by the onset of More-Electric-Aircraft peak loads and “cold-crank” Auxiliary Power Unit (APU) electric-starting in demanding cold temperature environments.
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
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
2012-01-2206
Thomas Allen Baudendistel, Michael Boyd, Jon Zumberge
With the advent of modern parallel computing systems, larger and more accurate simulation models have been developed to simulate real-world hardware. These models require verification and validation (V&V), the latter using data acquired from representative hardware to ascertain the uncertainty of the model. An understanding of the errors introduced by the measurement system into the validation assessment allows for the model assessor to attribute errors to the measurement system as opposed to the model or experimental setup. Once the model(s) have been through the validation process, decision makers can better understand the risk associated with using these models. This paper describes one possible procedure to quantify the uncertainty of the data acquisition (DAQ) system.
2012-10-22
Journal Article
2012-01-2205
Jason Wells, Maher Hasan, Charles Lucas
The combination of increasing performance demands, increasing system complexity, and the need for reduced program development schedule and budget costs in the aerospace industry is driving engineers to increasingly rely upon modeling, simulation, and analysis (MS&A) in the platform development cycle. One approach to ensuring that such integrated system simulations remain computationally tractable is co-simulation utilizing technology found in commercially available packages, such as PC Krause and Associates, Inc.'s (PCKA's) Distributed Heterogeneous Simulation (DHS) / FastSim software. In such co-simulation environments, dynamic models are executed in independent model spaces, with coupling between subsystems achieved by exchanging a minimal set of required data typically found at subsystem boundaries.
2012-10-22
Technical Paper
2012-01-2204
Chirag Jagadish, Suman Sadhu, Chinmaya Patil
The approach towards building hybrid vehicles has evolved with time and requirements. What used to be direct prototype building activity has moved towards building mathematical models before the actual prototypes are built. These models are utilized in optimizing component sizes, design and calibrate controllers and to estimate fuel economy improvements. If model results show promise, the actual prototype building activity is started. But modeling of vehicles still has a long way to go before aligning with businesses and aiding them as decision making tools on R&D investments. The reason being - the model building activity itself is prolonged and expensive. In addition to this, a lot of proprietary information such as component efficiency maps is required in order to build the model. In absence of these component level data, extensive testing becomes necessary where again vast amounts of resources have to be allocated.
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
2012-01-2192
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.
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
2012-01-2197
Brian C. Raczkowski, Benjamin Loop, Marco Amrhein, Jason Wells, Eric Walters, Oleg Wasynczuk, Sean Field, Peter Lamm
More electric aircraft (MEA) architectures have increased in complexity leading to a demand for evaluating the dynamic stability of their advanced electrical power systems (EPS). The system interactions found therein are amplified due to the increasingly integrated subsystems and on-demand power requirements of the EPS. Specifically, dynamic electrical loads with high peak-to-average power ratings as well as regenerative power capabilities have created a major challenge in design, control, and integration of the EPS and its components. Therefore, there exists a need to develop a theoretical framework that is feasible and useful for the specification and analysis of the stability of complex, multi-source, multi-load, reconfigurable EPS applicable to modern architectures. This paper will review linear and nonlinear system stability analysis approaches applicable to a scalable representative EPS architecture with a focus on system stability evaluation during large-displacement events.
2012-10-22
Technical Paper
2012-01-2196
Novica A. Losic
The comparison between a proposed aircraft cabin and cargo heater control system and conventional control schemes is presented together with the key performance figures of the systems. An active AC/DC converter comprising a Phase-Locked Loop (PLL) is proposed to control the energy supplied by the AC Variable Frequency (VF) source to the heater loads instead of controlling the energy by means of a Pulse-Width Modulated (PWM) AC power flow. The proposed system eliminates problems associated with interharmonics generated in the AC VF PWM case - a material advantage. It draws a close to sinusoidal current from the VF source, features a near unity power factor, and operates within the VF range due to the use of PLL.
2012-10-22
Technical Paper
2012-01-2195
Novica A. Losic
Modeling and analysis of a reduced order tracking 3-phase Phase-Locked Loop (PLL) based on a combined control principle (error + disturbance) to improve PLL locking performance is presented in this work. The principle is in synthesizing a feedforward control that is added to a Stationary/Floating Frame Transformation PLL or Synchronous (Delta Q) Frame Transformation PLL. The feedforward comprises a frequency-to-voltage converter based on a phase/frequency estimation using an algebraic summation while implementing an inverse feedforward control principle relative to the part of the feedback loop seen after the summing junction. The reduced order tracking PLL is shown to desensitize the system relative to the conventional part PI controller tuning parameters and is operated to lock on either linear or nonlinear load current waveform and for arbitrary frequency/phase profile while maintaining stability by minimizing system dynamics.
2012-10-22
Journal Article
2012-01-2193
Derick Balsiger, Todd Kazmirski, Mike Shaw
Electro-mechanical actuation systems are becoming more common in aerospace applications. Systems that have been traditionally based on hydraulic-mechanical (HM) actuators are now being replaced by electro-mechanical actuation systems in pursuit of the more electric airplane. The actuator's primary purpose is to convert energy (hydraulic or electrical) to mechanical energy and this operating mode occupies the primary design focus. A secondary design concern is the conversion of mechanical energy back into hydraulic or electrical energy. This energy results from potential and kinetic energy stored in the mechanical system during actuation. A portion of this energy flows back through the actuator towards the source. In the case of HM actuation, the management of this energy is well understood. In electro-mechanical actuation systems, this energy is commonly referred to as regenerated energy or regen for short.
2012-10-22
Journal Article
2012-01-2180
Angela Lowe, Dimitri N. Mavris
Turboelectric propulsion is a technology that can potentially reduce aircraft noise, increase fuel efficiency, and decrease harmful emissions. In a turbo-electric system, the propulsor (fans) is no longer connected to the turbine through a mechanical connection. Instead, a superconducting generator connected to a gas turbine produces electrical power which is delivered to distributed fans. This configuration can potentially decrease fuel burn by 10% [1]. One of the primary challenges in implementing turboelectric electric propulsion is designing the power distribution system to transmit power from the generator to the fans. The power distribution system is required to transmit 40 MW of power from the generator to the electrical loads on the aircraft. A conventional aircraft distribution cannot efficiently or reliably transmit this large amount of power; therefore, new power distribution technologies must be considered.
Viewing 1 to 30 of 547

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