Double-Fed Induction Linear Alternator

Glenn's novel system supports the NASA Aeronautics Research Mission Directorate (ARMD) strategic plan to leverage advancements in technologies over the next 25 years and beyond, leading to new aircraft configurations with enhanced performance, improved energy efficiency, and reduced CO2 emissions. The electric system is a multi-megawatt micro-grid that converts mechanical energy to electric via generators, and electric energy to mechanical via motor-driven fans. This innovation would use the variation in aircraft throttle settings to produce a high-voltage (20 kilovolts), variable-frequency 9-phase AC distribution system. Using doubly fed electric machines (generator, propulsor, and flywheel) allows for field excitation that can cause variable-frequency or variable speed operation around the commanded throttle setting. The flywheel enables an energy storage system that recovers and reuses energy, while the flywheel slews with the throttle control using the electromagnetic torque produced by the doubly fed electric machine. This design permits both sub-synchronous and super-synchronous operation using limited field excitation power provided through power converters. Finally, the reduced switchgear mass facilitated through the use of a high-frequency AC system, setting-less protection zones, and simplified switches for fault clearance provides enhanced operational capability. This system can be controlled so that fault energy is minimized, preventing collateral damage to aircraft structures even with high voltage distribution. Glenn's innovative system adds performance, efficiency, reliability, and cost savings to cutting-edge hybrid electric technology. This is an early-stage technology requiring additional development, and Glenn welcomes co-development opportunities.

Commercial soft magnetic cores used in power electronics are limited by core loss and decreased ferromagnetism at high temperatures. Extending functional performance to high temperatures allows for increased power density in electric systems with fixed power output and elevated operating temperature. The innovators at Glenn developed a unique composition and process to improve the temperature capability of the material. Nanocomposite soft magnetic materials are typically comprised of a combination of raw materials including iron, silicon, niobium, boron, and copper. Instead of niobium, NASA's material utilizes small cobalt and tantalum additions. The raw materials are combined to form an amorphous precursor through melt spinning. NASA&#39s innovation with the fabrication lies in the thermal annealing step, which nucleates and crystallizes the precursor to form the composite structure of the material. By adjusting the temperature and magnetic field of the thermal annealing step, Glenn's process results in good coupling between the crystalline and amorphous matrix phases. Innovators at Glenn demonstrated the temperature robustness using small test cores of their material and are investigating additional quality attributes compared to other well-known soft magnetic materials (see two Figures below).

The SHEARLESS composite boom has a rollable structure with a large moment of inertia per unit of stored height that does not suffer from shear-derived problems. The boom is fabricated from joining two independent tape-springs front-to-front with the use of a durable seamless polymer sleeve. This sleeve allows the two parts to slide past each other during the coiling/deployment process so as to minimize shear and its derived problems. The innovation enables a lightweight structure that can be stowed on a reel without appreciable shear stresses developing in its constitutive composite parts, allowing for unprecedentedly small coiling diameters for the total thickness of the structure. As demonstrated, through specific laminate design of the two inner composite parts, the SHEARLESS composite boom can also be fabricated with a special inherent feature, bi-stability, which enables designs with minimal mechanisms and aids in deployment controllability and reliability.

Modern production of e-textiles utilizes an embroidery technique called “e-broidery” that directly stitches circuit patterns with conductive thread onto textiles. This automated manufacturing process combines steps of e-broidery and milling to expand the application of e-textiles to high-current and high-speed uses. Manufacturing begins with two layouts of the desired conductive pattern. After assembling the layers of conductive and nonconductive materials, e-broidery is performed with the second layout and nonconductive thread to secure the layers together and designate the pattern for the conductive material. The secured assembly is transferred to an automated milling or laser cutting machine, which cuts the desired conductive pattern and releases the unneeded portions of the conductive material. The resulting e-textiles are tightly woven together, providing higher surface conductivity and impedance control. Initial comparison tests assessing the performance of fabric-based spiral antennas developed with this method, compared to conventional antennas, indicated no loss in performance across multiple metrics, including voltage standing wave ratio (VSWR), radiation pattern, and axial ratio performance. The Method and Apparatus for Fabric Circuits and Antennas is a technology readiness level (TRL) 6 (system/subsystem prototype demonstration in a relevant environment). The innovation is now available for your company to license. Please note that NASA does not manufacture products itself for commercial sale.

Glenn's thermoacoustic power converter reshapes the conventional Stirling engine from a toroidal shape into a straight colinear arrangement. Instead of relying on failure-prone mechanical inertance and compliance tubes, this design achieves acoustical resonance by using electronic components. In a typical Stirling engine, the acoustical wave travels around a toroid and reflects back, forming a standing wave. In Glenn's device, by contrast, the wave instead travels in a straight plane where a transducer receives the acoustical wave and electrical components modulate the signal. A second transducer on the diametrically opposed side reintroduces the acoustic wave with the correct phasing to achieve amplification and resonance. Glenn's design allows the transducers to operate at high frequency while presenting a mass rather than stiffness impedance. Glenn's magnetostrictive alternator uses stacked magnetostrictive materials under a biased magnetic and stress-induced compression. The acoustic energy from the engine travels through an impedance-matching layer (which can be formed from aerogel materials) that is physically connected to the magnetostrictive mass. Compression bolts keep the structure under compressive strain, allowing for the micron-scale compression of the magnetostrictive material and eliminating the need for bearings. The alternating compression and expansion of the magnetostrictive material creates an alternating magnetic field that then induces an electric current in a coil wound around the stack. This alternator produces electrical power from the acoustic pressure wave and, when the resonant frequency is tuned to match the engine, can replace the linear alternator to great effect.