AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0100: High-Speed Propulsion

Davis, Doug

937-255-7057

We conduct research on ramjet/scramjet and mixed-cycle propulsion components applicable to supersonic and hypersonic flight regimes. This includes fluid-dynamic studies of inlet, combustor, and nozzle components. We also pursue development of efficient computational methods, turbulent models, and kinetic schemes for reacting, high-speed flows. Our research approach necessitates the integration of experimental and theoretical methods to address challenges in (1) turbulent transport, entrainment, and mixing of multistream flows and/or two-phase flows including fuel injection, atomization, droplet transport and evaporation, flame stabilization, and blowout limits; (2) nonintrusive, multidimensional diagnostic instrumentation and concepts, including hardware and software, for applications to realistic combustor flow environments; and (3) time-averaged and time-dependent computational-fluid-dynamics codes for flow and combustion simulations in complex geometries. Available equipment includes extensive computer facilities (mini's to high-speed, mutiprocessor supercomputers), two combustor thrust rigs, a research combustor designed for a wide range of operations and applications of laser diagnostics, and a spray tunnel facility with associated optical and conventional diagnostic equipment. Also available is a stand-alone supersonic flow research facility, specifically designed for nonintrusive probing of the supersonic flowfield for simultaneous field measurements of pressure, temperature, velocity, and species concentration.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0101: Combustion and Spray Studies and Diagnostic Development

Gord, James

937.255.7431

This research addresses the physics and chemistry of processes in gas turbine combustors and pulsed-detonation engines through the study of isolated and interacting droplets, sprays, jet premixed and diffusion flames, swirling flames, and bluff-body stabilized flames. Continuing work requires experimental and theoretical approaches related to the following: (1) turbulent transport, mixing, entrainment, evaporation, droplet drag, drop-spacing effects, atomization, finite-rate chemistry, flame stability, ignition, and blow-out; (2) development of laser-based diagnostic techniques to support combustion and spray experiments; and (3) studies using either time-averaged or large-scale, time-dependent simulations. Numerous well-equipped laboratories contain small- and large-scale combustion tunnels and advanced laser apparatus designed for two-dimensional imaging, coherent anti-Stokes Raman spectroscopy; laser Doppler anemometry; phase Doppler particle sizing; laser-induced florescence techniques; and femto/picosecond chemistry studies. Access to various combustion flow codes and the DOD ASC Major Shared Resource Center is available for theoretical studies.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0102: Model Development and Validation Experiments for Aircraft Fuel

Edwards, James

937.255.3524

Aviation fuels are not only the energy source for advanced aircraft; they are also used to cool airframe and engine components. Under high thermal loads, hydrocarbon fuels can react with dissolved oxygen or undergo pyrolysis to form gums and other deposits that reduce the efficiency of heat exchangers and cause fouling of fuel-system components. Computer models that can be used to estimate the thermal decomposition of hydrocarbon fuels in simple heat exchangers are in an early stage of development. The models are time dependent and include global chemistry, fluid mechanics, and thermodynamic effects. Many of the fundamental processes associated with thermal degradation of fuel are not well understood. One of the objectives of the models is to improve our understanding of selected issues in physics and chemistry. Of particular interest is experimental and theoretical research on the influence of dissolved oxygen content, turbulence, thermal loads, pressure, catalytic reactions, or heat-exchanger geometry on the thermal degradation of hydrocarbons found in jet fuels. Dedicated minicomputers and reacting flow codes are available for theoretical studies. This research includes current fuels (JP-5,7,8,10), as well as alternative (non-petroleum) fuels. Alternative fuels include those derived from coal or biomass through the Fischer-Tropsch process, as well as aviation fuels derived from oil shale and tar sands and direct liquefaction of coal. "Biojet" fuels, analogous to biodiesel, are also of interest.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0103: Advanced Turbine Engine Lubrication

Forster, Nelson

937.255.4347

This research focuses on developing advanced lubricants and related mechanical components (bearings, gears, and seals) required for turbine engines to power aircraft in the twenty-first century. We are developing novel mechanical and magnetic systems to minimize the weight and complexity of the traditional lubrication system. Finite element methods are used to model heat dissipation, stress fields, and shaft dynamics. We are currently interested in creating a graphical user interface to couple bearing analytical software codes with commercial FEA packages such as ANSYS. Continuing research in high-temperature lubrication addresses thermal-oxidative degradation; and tribological, toxicological, and environmental properties of candidate lubricants. World class facilities equipped with unique test equipment and instrumentation are available for analytical, simulation, oxidative-thermal degradation, bearing and gear performance, rolling contact fatigue, elastrohydrodynamic film, high-pressure viscometric, diagnostic, and magnetic bearing studies. Dedicated minicomputers, a Silicon Graphics Octane workstation, and finite element and tribological modeling software are available for theoretical studies.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0104: Aero and Thermodynamics of Rotating Machinery

Rivir, Richard

937.255.2744

An improved understanding of internal flows and heat transfer under nonsteady conditions is necessary for the continued advancement of turbine engine performance. The inability to accurately predict heat transfer of cooled and uncooled components in the hot section significantly impacts the design and development cost of new engines and component lifetime. Reductions in specific fuel consumption are largely related to our ability to increase turbine inlet temperature and cycle pressure ratio. Important research areas include cooling of disk cavities, turbine blades, shrouds, vanes (internally and externally), and their resulting losses. Nearly all of these flows are three dimensional and unsteady. Low Reynolds numbers result in separation of the flow from the suction surfaces in low-pressure turbines resulting in losses in turbine efficiency. Flow control by both passive and active techniques is investigated in linear cascades and rotating engine hardware. Experimental and computational investigations involve increases in film cooling effectiveness, techniques for increasing and decreasing heat transfer coefficients, methods of flow control to increase blade loading, reduce passage, hub and tip losses, and techniques for controlling aeroelastic effects and damping. Characterization of aerodynamic thermal and structural effects requires non steady two- and three-dimensional computational schemes, and experimental techniques capable of similar spatial and temporal resolution. These spatial scales/temporal resolutions need to approach wall flow scales in order to provide the accurate time-resolved blade vane interaction effects, as well as loss mechanisms and heat transfer associated with other nonsteady secondary flow phenomena that are present. Nonsteady shocks and shock boundary layer interactions can also be present. Specific computational interests are three-dimensional nonsteady, multidisciplinary approaches that are capable of optimizing aerodynamic, thermal, and structural designs. Strong pressure gradients, density gradients, curvature, rotation, and compressive effects are present in many of these flows.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0105: Diffuser/Fan Interaction Modeling and Simulation

Puterbaugh, Steve

937.255.7432

A number of future aircraft platforms under study incorporate gas turbine propulsion systems that are embedded within the air frame. Further, the diffuser, which sits between the inlet and the propulsion system may be of serpentine or some other odd geometric shape. A diffuser with curved walls will generate secondary flow, which is likely unsteady, that will influence the behavior of the fan module of the engine. Complex total pressure distortion patterns in combination with significant flow angularity is expected to be present at the Aerodynamic Interface Plane. The Compressor Aero Research Lab (CARL) is pursuing a combination experimental and computational research program to determine the interaction effects of such a system. The ultimate goal of the computational part of the research is to fully model the unsteady fluid mechanics occurring within the diffuser and a full-annulus representation of the research fan stage. Disparate time and length scales of the two components make this a challenge.

There are two areas of the computational work of particular interest to the CARL effort. First is development and implementation of solver and turbulence modules that will interface with the in-house developed, object-oriented computational framework to provide a reliable computational tool for the problem at hand. Second is the development and implementation of co-processing tools for analysis and display of computational results generated by this grand challenge-scale computational effort. The in-house developed framework accommodates solver components for simulations ranging from 1-D analyses to 3-D RANS to LES to DNS. A number of reduced order and high-fidelity methodologies exist for the solution of the coupled inlet-propulsion system. It is desired to implement and compare a number of these methods within the framework – particularly unsteady RANS and LES –to promote consistency between solutions. This will also allow recommendations and best practices to be formulated. As simulation sizes increase, specifically for unsteady RANS and LES analyses, the amount of data available for 3-D flowfields has skyrocketed to > 1TB for many datasets. As such, it is incredibly important for some data reduction to occur during solver execution in order to eliminate the need to write excessive unsteady data. Capabilities are sought to meaningfully reduce the 3-D flowfields into manageable, analyzable extracts. Examples include particle tracking, accumulators (time-averaging and statistics), cut planes and isosurfaces, and feature detection (shocks, wakes, vortices). Successful implementation of the solver and co-processing capabilities will result in improved capability to quickly evaluate the efficacy of methods to capture coupling effects, distortion transfer, and relevant physics.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0106: Computational Modeling for Advanced Concepts in Gas Turbine Engine Combustion

Sekar, Balu

937.255.2668

Computational fluid dynamics (CFD) is becoming a powerful tool in the design and analysis of advanced air-breathing propulsion including conventional and unconventional systems. The latest improvements in numerical algorithms, geometric modeling, numerical discretization, grid generation, physical parameter modeling, and adaptability in the supercomputing environment (including parallel architecture), CFD tools are applied throughout the development process of combustion systems. The Combustion Branch of the Turbine Engine Division conducts research in interdisciplinary areas for gas turbine combustor flows. These areas include CFD, phenomenological physical modeling for turbulence for more accurate diffusion modeling, reduced reaction kinetics for hydrocarbon fuels, large eddy simulation techniques, turbulence-chemistry effects, multiphase flows, supercritical fuel technology, combustion aids and flame stabilization, and numerical acceleration schemes to improve convergence including solution adaptive techniques and unstructured grid technology. This research will emphasize numerical multi-dimensional analysis, reduced order analysis, analytical, computational, physical and numerical model developments including appropriate validations. Excellent computational platforms and high-speed graphic workstations are also available. The research will enhance our capability to design, analyze and optimize efficient combustion systems for turbo machinery.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B0112: Studies of Novel Combustion Concepts for Propulsion Systems

Zelina, Joseph

937.255.7487

AFRL's Combustion Branch plans, develops, and transitions basic research and applied technology development programs for military air-breathing engines. We do this by executing in-house and contracted programs that enhance the capability of turbo-propulsion systems through design, analysis, development, and test of advanced combustion systems. Additionally, the branch explores novel propulsion concepts critical to meeting future Air Force requirements. Some of these novel concepts include pulsed-detonation engines, inter-turbine burners, and trapped vortex combustors. The branch has in-house activities associated with these concepts.

The branch evaluates and enhances component capabilities through the understanding and innovative use of chemistry, aerodynamics, heat transfer, materials, diagnostics, computational fluid dynamics, and design tools. Areas of fundamental research include fuel injection, fuel-air mixing, fuel atomization, chemical kinetics, flame stability, supercritical fuel injection, flame dynamics and ignition phenomena. A growing focus area is the understanding the chemistry and combustion characteristics of alternative fuels for new propulsion systems. Well-equipped laboratory laboratories and computational resources are available to carry out the research activities. The laboratories can operate at sub-atmospheric to 40 atmosphere conditions, and include a host of intrusive and non-intrusive diagnostic capabilities.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B5437: Advanced Diagnostics for High-Speed Flows

Carter, Campbell

937.255.7230

This research addresses technologies essential to high-speed, air-breathing propulsion, including fuel-air mixing processes in subsonic and supersonic flows and the role of turbulent transport on mixing and combustion in high-speed flows. Objectives include the following: (1) incorporation of science into preliminary design and advanced development of ram/scramjet combustors; (2) development and application of accurate CFD tools for the design and analysis of ramjet/scramjet combustors; (3) development and application of advanced non-intrusive optical diagnostic techniques for high-speed reacting flows; (4) study of ionized flows on a confined supersonic flow, especially for enhanced combustion; and (5) transition of basic research ideas, concepts, and findings to exploratory development programs. In particular three areas of focus are supported: (1) multi-phase flow, including gaseous fuel/air, fuel droplets, and plasma, (2) shock-boundary interactions within reactive media, and (3) multi-disciplinary laser measurements for benchmarking modeling and simulation of high-speed, reacting flows. Both laboratory scale (e.g., the stabilization of attached and lifted turbulent jet flames) and the large scale (e.g., stabilization of flames within a supersonic combusting ramjet engine) experiments are employed. Facilities include extensive high-speed wind tunnels, where conventional and advanced diagnostics can be employed, and a well-equipped optics laboratory, where techniques and ideas can be explored in small-scale flows prior to being employed in the large-scale facilities.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B5438: Structural Dynamics of Turbomachine Components

Cross, Charles

937.255.7206

For continued improvements in gas turbine engine performance and durability, a better understanding of the structural dynamics and vibrational response of airfoils, disks, and blisks is essential. Vibration of turbomachine airfoils and disks is a significant source of gas turbine engine failures and the need for both unscheduled and scheduled maintenance. Additionally, to meet the performance requirements of advanced gas turbine designs, new compressor designs tend toward airfoils with higher tip speeds, lower aspect ratios, more closely spaced airfoil rows, and fewer stages. These trends result in advanced components experiencing higher loading forces while having a reduced structural capability. The result is increased vibratory response and stress, leading to destructive high cycle fatigue failures. Our research goal is to assess life capability and vibrational characteristics of turbine engine components. Quantification of the capability of components under cyclic loading can reduce or even alleviate the need for costly repairs and diminish the possibility of failure.

Research areas in the study of airfoil and disk dynamics include investigation of mistuning in higher order modes, interaction of closely spaced modes, evaluation of inherent and added damping in airfoil systems, and integration of experimental results into prediction codes and FEM. Proposed research areas for improved bench experimentation include the development of simulated engine operating conditions (rotational forces, contact mechanics, component interactions), the development of innovative test techniques for component characterization, and the validation of advanced instrumentation techniques.

To support research in these areas, the Turbine Engine Fatigue Facility (TEFF) of AFRL's Propulsion Directorate is available. The TEFF is a state-of-the-art research facility, which performs structural and vibrational evaluations of turbine engine components. The TEFF provides support to Air Force development programs through basic research and analysis in the areas of structural characterization, vibrational response, life prediction, and application of advanced measurement techniques. Experimental capabilities include scanning vibrometry, ping dynamic frequency analysis, travelling wave excitation, , large-scale dynamic shakers, high-temperature ovens, and single and multiaxial fatigue test stands.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B5439: Injection and Flameholding in Supersonic Flows

Gruber, Mark

937.255-7350

The success of a hydrocarbon-fueled scramjet depends on the ability of the combustor to sustain efficient combustion over a wide operating range. During a typical flight, the combustor will experience several transient events that, if not robustly managed by the flameholding system, could compromise engine performance and even vehicle life. For example, the flowfield that exists inside the combustor before ignition is significantly different than the flowfield after ignition. Also, as the engine accelerates from low to high flight velocity (e.g., Mach 4 to 8), the character of the flow within the combustor changes, the combustor fuel distribution may change, and the fuel itself may change (as a result of endothermic cracking). All of these changes may significantly impact the behavior and stability of the flameholder. Our research focuses on the understanding of flameholding in supersonic flows. We then strive to use that improved understanding to design and investigate more robust flame stabilization techniques for hydrocarbon-fueled scramjets. We have several experimental resources available to execute the research including two combustor thrust stands, a research combustor designed for a wide range of operation, and a stand-alone supersonic research facility specifically designed for non-intrusive probing of reacting and non-reacting flowfields to flameholding in a supersonic combustor. A wealth of conventional and advanced instrumentation is also available for measurements of pressure, temperature, velocity, and species concentration.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B5859: Gas Turbine Control Systems and Engine Health Management Research

Behbahani, AR

937.255.5637

The development of control systems and software that can deal with the dynamic and uncertain nature of highly integrated turbine engine systems depends on a fundamental understanding of the physics of propulsion. Robust, distributed, model based, and model predictive control concepts must be explored to achieve the desired capabilities in new gas turbine engine designs. While advances in control system technology will impact system performance at a given instance in time, a focus on tracking engine degradation is required to optimize performance over the life of the system. Research is required to develop a greater understanding of performance degradation mechanisms, and the impact of component degradation on system behavior.

The Air Force Research Laboratories Propulsion Directorate has established a Turbine Engine Dynamic Simulator (TEDS) as a real-time test bed for the development of advanced engine controls, diagnostics and prognostics. This simulator, data acquisition equipment and comprehensive engine models are used to explore simulation-based approaches for real-time, physics-based controls and health management algorithms. In a simulation based approach, a model of the propulsion system is embedded within the control system and tracks engine performance to continuously adjust to changes in the engine or operating environment. The use of a simulation based approach is also useful both in the context of virtual test where testing with actual systems is cost or time prohibitive and as embedded control system software to predicted sensed values where actual sensors could not be used.

As a result of this work, researchers gain a better understanding of the complex system interactions that exist in new propulsion systems and apply this knowledge in the development of future high performance, highly integrated systems.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B6706: Unsteady Aerodynamics and Heat Transfer in Turbines

Clark, JP

937-255-7152

An accurate accounting of unsteady flow phenomena is critical to the successful design of turbine components. This is especially true for future systems, where it is desirable both to increase engine performance and to reduce operating costs. Phenomena of current interest include vane-blade interactions, unsteady shock boundary-layer interaction, boundary-layer transition, separation control, and unsteady heat transfer and cooling as a result of the passage of turbine blade tips over outer air seals. Research opportunities in the turbine branch of the Turbine Engine Division typically have combined design, analysis, and experimental aspects. A complete design, analysis, and optimization system is in place to create advanced turbine components for validation testing in the laboratory. For example, by capitalizing on advances in transition modeling made at the laboratory, the system was used successfully to define exceptionally high lift low pressure turbine airfoils. High pressure turbine components with low heat load have also been defined and validated and we anticipate that further advances in the state-of-the-art in turbine aerothermodynamics are achievable with these design tools. Therefore, we are particularly interested in analytical work to improve the design system, including improvements in optimization techniques. In addition, a hybrid Reynolds-Averaged Navier Stokes/Large Eddy Simulation code is now being developed for incorporation into the system. It is also possible to access computational resources at the US Air Force Shared Resource Center to support projects. Experimental facilities available for design system validation and other research run the gamut from low-speed wind tunnels suitable for the assessment of fundamental flow physics on flat plates and cylinders in cross-flow, to low- and high-speed linear cascades (with and without heat transfer and/or cooling) and full scale, rotating transonic turbine rigs.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.01.B9931: System Integration Optimized for Energy Management

Wolff, J.

(937) 904-9644

On demand systems require attention to issues of system integration and energy management for optimal performance and capability. Integrated system modeling and simulation spans a broad range of technical expertise such as thermal management, power generation, power distribution, and load management in a highly dynamic environment. Energy conversion is critical in the efficient design of on demand systems. For aircraft applications, the majority of energy conversion takes place in the gas turbine. Therefore, significant opportunities exist for optimizing this process, especially the consideration of auxiliary systems and how they interface with the hot gas engine sections. Gear boxes and starter/generators are key components of power generation leading to power distribution which is then connected to load management. Methods of storing and dissipating energy such as high-energy density batteries, super-capacitors, and heat exchangers are also vital for on demand system optimization which has regenerative energy capability. Underlying these system integration issues is the basic energy management issue of on demand highly dynamic thermal management. Depending on the on demand energy rates, fundamental assumptions such as thermodynamic equilibrium are violated. Therefore, research into various fundamental non-equilibrium thermodynamics methods such as mesoscopic thermodynamic descriptions of non-equilibrium thermodynamics, quantum thermodynamics, and extended irreversible thermodynamics is being accomplished. From an experimental view, hardware in the loop (HIL) system integration optimization for energy management will continue to be pursed. In particular, remote HIL system integration is vital to advancements in aircraft system integration. Finally, research into integrated system health management will continue to be utilized to optimize the complete system.

Keywords: System integration; Thermal management; Power handling; Energy conversion; Gas turbines; Non-equilibrium thermodynamics; Hardware in the loop (HIL); Health management; Heat exchangers

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.02.B0109: Physics of Electric Discharges

Adams, Steve

937.255.2923

Basics atomic, molecular, and optical physics of electrically excited gas discharges are studied in a number of configurations including direct current, radio frequency, and microwave excitation. Also, basic research on ion deposition of large area, high temperature dielectric thin films is studied. Research is primarily experimental and includes studies of ionization cross sections and ion-molecule reaction rates, excitation processes, energy transfer processes under non-equilibrium conditions, electron transport, and thin film production mechanisms. Experimental facilities include a high resolution Fourier-transform mass spectrometer, modified for ionization cross section measurements, pulsed inductively coupled plasma source, plasma diagnostics including optical emission and absorption spectrometers, microwave interferometer and Langmuir probes, and systems for both microwave deposition and low-energy ion-beam deposition of large area thin films. Applications include plasma processing and deposition of high temperature electronic materials, control of plasma characteristics, and early stages of spark ignition of complex fuel molecules.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.02.B0110: Applied Atomic and Molecular Spectroscopy

Ganguly, Biswa

937.255.2923

Spectroscopic methods are developed and applied for quantitative measurements in nonequilibrium plasmas and high-temperature reacting flows. Well-defined low to medium pressure discharges using CW and pulsed direct current, low frequency to radio frequency, microwave excitations, and tandem pulsed-microwave excitations are investigated for their application to flow control in hypersonics, plasma enhanced etching, surface modifications, and dielectric breakdown. Experimental and theoretical studies are being conducted to characterize homogeneous and heterogenous processes in plasmas including plasma-surface interactions, plasma assisted ignition, and the creation and influence of self-ordered nanoparticles in plasmas. Power deposition scaling of atmospheric and near atmospheric pressure plasma properties including microplasmas are quantified by Stark spectroscopy, one- and two-photon allowed laser-induced fluorescence, Raman scattering, and photo absorption measurements using tunable visible to near-infrared, narrow line width diode laser sources. Experimental results are supported by theoretical modeling of electron kinetics and heavy particle interactions in nonequilibrium plasmas. A triple stage differentially pumped mass spectrometer is used to study transient discharge phenomena and photocatalytic reactions at medium to high pressure. We are also investigating the flux scaling properties of atmospheric pressure or near atmospheric pressure DBD plasma jet excited by short pulse duration, high reduced electric field dielectric barrier discharges for both vacuum ultraviolet/ultraviolet light source and low-cost surface coating applications.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.02.B4272: Research and Development of Efficient and Novel Thermal Management Approaches for Airborne Vehicles

Yerkes, Kirk

937.255.5721

Heat acquisition, transport, storage, and rejection represent fundamental limitations for future high-power, high-energy missions and for high-performance aerospace vehicles. Basic and applied heat-transfer and thermodynamic phenomena are examined analytically and experimentally with emphasis on their adaptation to airborne power-systems, electronic component thermal management, and directed energy weapon thermal management. Areas of interest include, but are not limited to single-phase, two-phase, multiphase systems, and high-performance rapid-responding thermodynamic systems; novel working fluid approaches for low and high temperatures (-55oC to >300oC for high-performance dielectric materials); nano and micro scale thermophysics; concurrent and countercurrent heat-transfer devices; capillary and other augmented heat-transfer methods for variable gravity applications; novel thermophysical and heat-transfer phenomena characterization; high- and low-temperature heat-transfer fluid-properties verification; unsteady heat transfer in pulsed and transient-phase change processes; analysis and verification of direct and indirect liquid cooling for electronic component temperature control; and the solution of the conjugate problem associated with this configuration for silicon carbide applications.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.02.B4833: Lithium-Ion Conducting Channel

Scanlon, Lawrence

937.255.2832

Rechargeable lithium polymer batteries are of interest because of the very high-energy densities achievable relative to that of current generation batteries such as nickel-hydrogen. A key problem associated with the development of this battery has been the poor performance of the polymer electrolyte at ambient and subambient temperatures. Recent developments within our laboratory have demonstrated that a solid-state lithium ion conducting electrolyte (lithium ion conducting channel) can function over a broad temperature range from + 100�C to -50�C with very high specific conductivities on the order of 10 to 100 mS/cm. This electrolyte is particularly attractive since the transference number for lithium is one. The electrolyte was designed by computational chemistry with this feature as the anion matrix provides a constant negative electrostatic potential throughout the molecular system. This characteristic is important for operating over a broad temperature range since lithium ion transport no longer depends on polymer segmental motion but on the electric field gradient created by the potential difference of the electrodes within the electrochemical cell. Our goals are to simulate the electric field gradient using computational chemistry and applying it to the lithium ion conducting channel molecular system in order to correlate molecular structure with ionic conductivity. In addition, we intend to investigate the electrolyte/electrode interface through computational chemistry. We conduct research on ramjet/scramjet and mixed-cycle propulsion.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.02.B4834: Wide Temperature Range Power Semiconductors

Scofield, James

937.255.5949

Research opportunities exist in the areas of power device design, development, and reliability assessment as they relate to wide bandgap power switch and diode performance in harsh environments. In addition to a consideration of carrier transport phenomena over wide temperature operational ranges, current research is focused on the thermo-mechanical aspects of device packaging to minimize CTE-related stresses and enhance reliability while providing the requisite electrical functionality. Novel composite and metallurgical materials are being investigated in module designs which aim to functionally optimize heat transfer efficiency and temperature distributions to minimize the stresses which drive conventional packaging failure modes. FEA modeling and simulation are extensively used to drive component designs which are subsequently validated empirically. In conjunction with this area of research is an interest in developing thermal models of heat transport across small-dimensional layers and interfaces that are not accurately described by Fourier conduction theory. A closely related area of research is in improving our understanding of the fundamental physics and chemistry of device failure in these emerging wide bandgap material systems. Efforts to determine activation energies and correlate device failure data with resident dislocations, inclusions, micropipe, and other defects is an area of high priority. Research interest also exists to develop sensors and optical interrogation techniques that are capable of providing accurate, repeatable, high-resolution response to small changes (<5%) in pressure, temperature, electrical current, voltage, and fluid flow under similar thermal environments.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.02.B4962: Superconductors, Thermoelectrics, Carbon Nanotubes, and Magnetic Materials for Advanced Power Applications

Haugan, Timothy

937.225.7163

The discovery of high-temperature superconductors (HTS), carbon nanotubes, thermoelectrics, and advanced magnetic materials offers many possibilities for their application in power systems such as generators, motors, and transformers. However, a fundamental understanding of these materials, uniquely engineered structures, or the discovery of new materials and superconductors with their associated development is necessary to realize these applications, both experimental and theoretical. Current emphasis on superconductors is the search for new superconductors at higher temperatures or more isotropic at liquid nitrogen temperatures. Basic research is also performed for the development of the HTS coated conductors, especially using YBCO, with emphasis on magnetic flux pinning enhancement, ac loss minimization, and stability and quench. Pinning enhancements include nanoparticulate dispersions among others. AC loss minimization includes losses associated with hysteretic, eddy current, coupling, ferromagnetic, and self-field transport. Pulsed laser deposition, MOCVD, and MOD are principally used to produce the superconducting films for study. Advanced development includes conductor configurations and coil windings, and design studies of power devices such as superconducting magnetic energy storage (SMES) or all-superconducting motor or generators. Thermoelectrics explore properties at higher temperature for waste heat applications. Emphasis is on multilayers, oxides, and carbon nanotubes, but others are considered. Carbon nanotubes are studied to achieve long lengths for electrical wiring and thermal transport properties. Magnetic materials research focuses on developing improved permanent magnets, such as high saturation and nanoparticle composite materials, and on soft magnetic material.

Eligibility: Open to U.S. citizens

AFRL/RZ WRIGHT PATTERSON AF BASE, OHIO

13.30.02.B6421: Logistic Fuel Capable, Power Dense Fuel Cells for Military Applications

Reitz, Thomas

937.255.4275

Many current and future military applications require power generation technologies that are both fuel efficient and quiet. Because of their high efficiency and low signatures, fuel cells are a promising power system technology that could enable these critical long endurance missions. Furthermore, because they have few moving parts, the projected maintainence costs are expected to be far less than internal combustion engines. The Department of Energy has been investigating these technologies for domestic applications but the emphasis is on achieving low cost, high duty power units for centralized power generation. The performance requirements of defense applications, by contrast, are significantly more demanding mandating the research and development of high performance fuel cell systems. The objective of this research effort is to explore materials and technologies for significantly improving the performance of fuel cell technology. In order to accomplish these objectives, two focuses will be explored. They include the examination of materials and application processes that reduces barriers to achieving high performance utilization of military logistic fuels and examination of electrochemical factors which influence high performance. Logistic fuel operability is the most pressing issue associated with the adaptation of fuel cells for defense applications. In order to achieve sustained JP-8 operability several approaches are envisioned which include; discrete fuel reformation, indirect fuel reformation, and direct oxidation fuel cells. Of these approaches, direct oxidation is the most challenging. In order to achieve the goals associated with direct electrochemical conversion of logistic fuels, significant research in the areas of ion conductive materials, high-temperature electrocatalysis, and interfacial science are being explored. Basic electrochemical analysis is applied in order to elucidate electrochemical factors that influence power dense, high performance operation. Methods for decreasing interfacial impedances through exploration of novel electrode structuring are of primary interest.

Eligibility: Open to U.S. citizens