The design, construction and operation of aircraft based on the scientific study or art of flight.
New Concepts in Film Cooling for Turbine Blades
In one of NASA Glenn's innovations, a shaped recess can be formed on a surface associated with fluid flow. Often V-shaped, this shaped recess can be configured to create or induce fluid effects, temperature effects, or shedding effects. For example, the shaped recess can be paired (upstream or downstream) with a cooling channel. The configuration of the shaped recess can mitigate the lift-off or separation of the cooling jets that are produced by the cooling channels, thus keeping the cooling jets trained on turbine blades and enhancing the effectiveness of the film-cooling process. The second innovation produced to improve film cooling addresses problems that occur when high-blowing ratios, such as those that occur during transient operation, threaten to diminish cooling effectiveness by creating jet detachment. To keep the cooling jet attached to the turbine blade, and also to spread the jet in the spanwise direction, NASA Glenn inventors have successfully used cooling holes that reduce loss by blowing in the upstream direction. In addition, fences may be used upstream of the holes to bend the cooling flow back toward the downstream direction to further reduce mixing losses. These two innovations represent a significant leap forward in making film cooling for turbine blades, and therefore the operation of turbine engines, more efficient.
Conditionally Active Min-Max Limit Regulators
Current aircraft engine control logic uses a min-max control selection structure to prevent the engine from exceeding any safety or operational limits during transients due to throttle commands. This structure is inherently conservative and produces transient responses that are slower than necessary. By activating the NASA Glenn's conditionally active limit regulators, engine response can be improved while preserving all necessary safety limits. An engine controller using CA limit regulators will get a faster engine response while ensuring engine safety. The improved performance is attained by eliminating unnecessary limit regulator activations and by utilizing more of the available safety margins. This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities.
GPS-Enhanced Onboard Navigation System (GEONS)
While real-time positioning computed by standard GPS service is adequate for some onboard applications, inherent position discontinuities are not acceptable for high-precision instrument applications, such as view-period prediction and maneuver planning, both of which are computations that require a continuous prediction of the spacecraft state. Real-time positioning also requires simultaneous measurements from four GPS satellites, a mission-limiting factor that must be considered. GEONS processes data from standard GPS receivers, onboard communication equipment, and/or attitude sensors, producing accurate absolute and relative navigation solutions in real time. Other functions, including onboard maneuver control and relative navigation for keeping formations are also supported by GEONS. All information is quickly available to scientists when it is included in the down-linked telemetry stream. GEONS provides high-quality solutions with fewer than four visible GPS space vehicles by employing an extended Kalman filter (EKF) augmented with physically representative models for gravity, atmospheric drag, solar radiation pressure, clock bias, and drift to provide accurate state estimation and a realistic state error covariance. GEONS incorporates the information from all past measurementscarefully balanced with GEONS data of the physical models governing these measurementsto produce an optimal estimate of the user spacecrafts orbit. GEONS high-fidelity state dynamics model reduces sensitivity to measurement errors and provides high-accuracy velocity estimates, permitting accurate state prediction during signal outages or degraded coverage. Autonomous navigation reduces total mission cost by eliminating the need for routine, ground-based orbit determination and special tracking services, and it is required for advanced mission concepts, such as satellite formation flying. GEONS was designed for autonomous operation within the very limited resources of an onboard computer. Autonomous initialization and enhanced fault detection capabilities are implemented using instantaneous geometric GPS solutions. By incorporating information from past measurements, GEONS provides highly accurate orbit estimates even with one visible GPS space vehicleand even during signal outages or degraded coverage. This unprecedented accuracy and reliability reduces navigation errors and does it autonomously with minimal onboard computer resources. Additionally, GEONS processes Doppler measurement data from onboard attitude sensors. These different types of measurements are all incorporated into the GEONS software, producing a navigation system capable of handling multiple orbit regimes and navigation subsystems, while requiring no additional hardware. Fusion of these data types increases system stability and reliability and enables graceful degradation in the event that a component fails during orbit.
Spanwise Adaptive Wing
Prior efforts to actuate wing articulation were unsuccessful, largely because the systems designed were too large, heavy, and complex to be practical for use. NASA's comparatively simple SAW concept centers on a wing actuator fabricated from lightweight SMA material, which is trained to deform to a specific shape as it becomes heated. SMA actuators are composed of high-strength alloys, such as nickel-titanium-hafnium, and can feature elements such as trained tubes, wires, cables, or sheets. For example, a high-temperature, high-force SMA torque tube can be embedded in an outboard chordwise hinge line of a wing. Every embodiment of the SMA actuator features integrated heaters and cooling devices that enable better control authority. A novel hinge line mechanism both provides a two-piece wing connection and houses the actuator assembly. When the actuator is heated, the SMA apparatus triggers the articulation of the wing to a predefined position. Once the desired position is reached, the heater maintains a constant temperature, causing the SMA to maintain its deformity. As needed, the cooling system can be used to allow the wing to return to its original geometry. Multiple actuators can be employed on a single wing, allowing the various parts of the wing to articulate independently. By adapting the geometry of the wing during all phases of operation, from ground to subsonic and supersonic/hypersonic flight, NASA's SAW offers the first practical method of using wing articulation to improve aircraft performance and fuel efficiency.
Aircraft Engine Icing Event Avoidance and Mitigation
Glenn's novel system uses an engine-system simulation tool and a compression flow-analysis code to detect icing risk and location for aircraft. The existence of an ice-crystal environment in the atmosphere will be determined by one or more of three methods: (1) an external data monitoring system that detects ice crystals directly; (2) the control system that detects changes in key engine parameters, such as the ratio of fan speed to core engine speed or fuel flow rate; and (3) advanced radar that detects ice crystals in the flight path of the aircraft. If risk of icing is present, Glenn's tool signals the control system to modify the engine operating parameters so as to pre-emptively prevent a significant amount of accretion from occurring, or alternatively, guides the aircraft to a location where ice crystals accretion will not occur. Standard practice has been for pilots to navigate at least 100 miles around visible storms, but with the improved accuracy provided by Glenn's innovation, the pilot can fly as close as 20 miles to the ice-crystal environment, while still maintaining enhanced safety. Since the magnitude of change to the engine operating parameters is so small (and the level of engine thrust set by the pilot remains the same), any modification will be imperceptible to both the pilot and passengers. In addition, Glenn's system can be easily integrated into new engines or retrofitted into existing technologies. This innovation proactively avoids or mitigates one of aviation's most serious threats ice accretion while simultaneously offering reduced fuel and maintenance costs.
Compact, Lightweight, CMC-Based Acoustic Liner
NASA researchers are extending an existing oxide/oxide CMC sandwich structure concept that provides mono-tonal noise reduction. That oxide/oxide CMC has a density of about 2.8 g/cc versus the 8.4 g/cc density of a metallic liner made of IN625, thus offering the potential for component weight reduction. The composites have good high-temperature strength and oxidation resistance, allowing them to perform as core liners at temperatures up to 1000°C (1832°F). NASA's innovation uses cells of different lengths or effective lengths within a compact CMC-based liner to achieve broadband noise reduction. NASA has been able to optimize the performance of the proposed acoustic liner by using improved design tools that help reduce noise over a specified frequency range. One such improvement stems from the enhanced understanding of variable-depth liners, including the benefits of alternate channel shapes/designs (curved, bent, etc.). These new designs have opened the door for CMC-based acoustic liners to offer core engine noise reduction in a lighter, more compact package. As a first step toward demonstrating advanced concepts, an oxide/oxide CMC acoustic testing article with different channel lengths was tested. Bulk absorbers could also be used, either in conjunction with or in place of the liners internal chambers, to reduce noise further if desired.
A Method for Reducing Broadband Noise
This NASA technology is ideally suited to absorb sounds below 1000 Hz (at the low end of human auditory range), which commercially available materials have struggled to absorb effectively. NASA innovators designed the acoustic liner to mimic the geometry and the low-frequency acoustic absorption of natural reeds. To provide excellent noise absorption that endures even in a variety of challenging conditions, researchers have created and tested prototypes of acoustic filters using thin and lightweight parallel-stacked tubes one-fourth to three-eights of an inch in diameter. The assembly can feature a porous or perforated face sheet positioned on one or more sides of the acoustic absorber layer to increase noise-reduction capability as needed. These filters have demonstrated exceptional acoustic absorption coefficients in the frequency range of 400 to 3000 Hz. Results indicate that these assemblies can be additively manufactured from synthetic materials, generally plastic; however, ceramics, metals, or other materials can also be used. The reeds can be narrow or wide, hollow or solid, straight or bent, etc., giving this acoustic liner remarkable flexibility and versatility to meet the needs of virtually any application. This technology effectively demonstrates that a new class of structures can now be considered for a wide range of environments and applications that need durable, lightweight, broadband acoustic absorption that is effective at various frequencies, particularly between 400 and 3000 Hz.
System and Method for Providing a Real Time Audible Message to a Pilot
The invention provides receipt of text messages that are communicated by, or received by, aircraft that are within a selected distance from the inquiring pilots aircraft. This information is filtered by a Pilots Aircraft receiver using a list of Target Words and Phrases (TWP) for which the subject is of concern to the pilot. Messages containing one or more of the selected TWPs are presented in a selected order as text or, alternatively as a verbal message for review by the pilot. Upon receipt of the TWPs, the pilot determines if any action should be taken in order to avoid or minimize delay associated with the information. Communication between the inquiring pilot and any other pilot within the prescribed range, geographic sector, and/or time interval is implemented using a publish and subscribe approach to exchange relevant data. A pilot determines which information to share and with whom and from whom the pilot is interested in receiving information (subscribe). This approach will avoid the radio chatter that often accompanies a party line system. Each such message may be assigned a priority with messages having higher priority being given preference in a message queue. The messages can be filtered and received as coded or encrypted, depending upon a situation or security concerns.
Aeroelastic Wing Shaping
Distributed propulsion and lightweight flexible structures on air vehicles pose a significant opportunity to improve mission performance while meeting next generation requirements including reduced fuel burn, lower emissions, and enhanced takeoff and landing performance. Flexible wing-shaping aircraft using distributed propulsion enable the ability to achieve improved aerodynamic efficiency while maintaining aeroelastic stability. Wing shaping concepts using distributed propulsion leverage the ability to introduce forces/ moments into the wing structure to affect the wing aerodynamics. This can be performed throughout the flight envelope to alter wing twist, hence local angle of attack, as the wing loading changes with air vehicle weight during cruise. Thrust-induced lift can be achieved by distributed propulsion for enhanced lift during take-off and landing. For a highly flexible wing structure, this concept could achieve a 4% improvement in lift-to-drag ratio, hence reduced fuel burn, as compared to a conventional stiff wing. This benefit is attributed to a reduction in lift-induced drag throughout the flight envelope by actively shaping the spanwise lift distribution using distributed propulsion. Vertical tail size could be reduced by utilizing differential thrust flight-propulsion control. This will result in weight reduction to achieve further fuel savings. Aeroelastic stability is addressed in the design process to meet flutter clearance requirements by proper placement of the propulsion units. This technology enables synergistic interactions between lightweight materials, propulsion, flight control, and active aeroelastic wing shaping control for reducing the environmental impact of future air vehicles.
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