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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A Vibrational Energy Harvesting Sensor Based on Linear and Rotational Electromechanical Effects

In this investigation, a magnetically coupled double-spring design is presented for harvesting low-level non-stationary random vibrational energy. The sensor relies on multimodal coupling between the translation and rotation of a two-spring magnet and coil system to widen the harvesting bandwidth. Energy methods are used to develop a model to characterize the electromechanical response of the system, the solution of which is obtained using stochastic techniques based on a particle swarm algorithm. This approach provides an efficient method to estimate system parameters that otherwise are difficult or impossible to determine with independent measurements. The experimental results demonstrate agreement with the theoretical predictions over a limited bandwidth. The sensor can effectively harvest non-stationary vibration energy down to 10 -4 g within a limited bandwidth of 130–150 Hz. The sensor prototype has an operational volume of 2.6 cm 3 with a calculated power density of 0.2 W/cm 3 . The sensor’s small size results in a coupling efficiency of approximately 6% across the tested bandwidth.

42 ENGINEERING↗
DOE OSTI2023

Investigating the Electromechanical Sensitivity of Carbon-Nanotube-Coated Microfibers

The piezoresistance of carbon nanotube (CNT)-coated microfibers is examined using diametric compression. Diverse CNT forest morphologies were studied by changing the CNT length, diameter, and areal density via synthesis time and fiber surface treatment prior to CNT synthesis. Large-diameter (30–60 nm) and relatively low-density CNTs were synthesized on as-received glass fibers. Small-diameter (5–30 nm) and-high density CNTs were synthesized on glass fibers coated with 10 nm of alumina. The CNT length was controlled by adjusting synthesis time. Electromechanical compression was performed by measuring the electrical resistance in the axial direction during diametric compression. Gauge factors exceeding three were measured for small-diameter (<25 μm) coated fibers, corresponding to as much as 35% resistance change per micrometer of compression. The gauge factor for high-density, small-diameter CNT forests was generally greater than those for low-density, large-diameter forests. A finite element simulation shows that the piezoresistive response originates from both the contact resistance and intrinsic resistance of the forest itself. The change in contact and intrinsic resistance are balanced for relatively short CNT forests, while the response is dominated by CNT electrode contact resistance for taller CNT forests. These results are expected to guide the design of piezoresistive flow and tactile sensors.

36 MATERIALS SCIENCE↗
NASA NTRS1965

Electromechanical flowmeter accurately monitors fluid flow

Electromechanical flowmeter remotely and accurately monitors the flow rate and total volume of a transparent liquid discharged from a dispensing system. A dual dispensing tube system provides a relative reference level which permits compensation for temperature variations.

Grant, D. J.↗
NASA NTRS1969

Electromechanical rotary actuator operates over wide temperature range

Electromechanical rotary actuator, which operates over wide temperature range, contains a spring stop which has been calculated to limit internal deceleration loads to a magnitude equal to stall torque. Cryogenic capability is obtained by using dry lubricant on the gears and no lubrication on the bearings.

Sullivan, S. F.↗
NASA NTRS1973

Dynamics of electromechanical flow structures.

Free-surface gravity flows and capillary wicking provide examples of flow structures with fluid partially ducted at free surfaces by external forces. Wall-less electromechanical flow structures are developed which have a similar nature, but with polarization forces providing the orientation at free surfaces. Like their mechanical counterparts, these have the ability to ingest liquid or expel vapor through their walls. The structures consist of electrodes running in the flow direction z with slowly varying cross sections in a plane transverse to the flow. A formulation is given of the long-wave nonlinear (principal mode) dynamics, with use made of energy functions to represent a broad class of possible mechanical and electrical structure geometries.

Jones, T. B., Jr.↗
NASA NTRS1973

New principles of construction of electromechanical vibration inducers

Electromechanical vibration inducers with high reliability and low noise level were created to study premature operating losses in their support bearings. An investigation was also made of the feasibility of developing stable synchronous operation of two vibrational inducers, rigidily fastened to a solid body with and without flexible suspension.

Ashmonas, K. A. P.↗
NASA NTRS1974

Hydrostatics and steady dynamics of spatially varying electromechanical flow structures

The hydrostatic and steady laminar hydrodynamic equilibria of spatially varying electromechanical flow structures are investigated. Under certain conditions the relationship between the dielectric height of rise and the applied voltage is found to be double valued. It is found that one of the two equilibrium values is always unstable. This gives rise to the experimentally observed spontaneous rise of the fluid to the top of the structure, once a certain critical voltage is reached. Starting above this critical voltage with the structure completely filled and decreasing the applied voltage toward the critical value results in pinch-in failure at an intermediate point along the structure and trapping of dielectric fluid at the top. The simple mathematical model developed predicts all these phenomena, without recourse to tedious point-by-point surface force equilibrium determination. Experiments are reported which verify the results for the hydrostatic case.

Jones, T. B.↗
NASA NTRS1974

Evaluation of the electromechanical properties of the cardiovascular system

Cardiovascular electromechanical measurements were collected on returning Skylab crewmembers at rest and during both lower body negative pressure and exercise stress testing. These data were compared with averaged responses from multiple preflight tests. Systolic time intervals and first heart sound amplitude changes were measured. Clinical cardiovascular examinations and clinical phonocardiograms were evaluated. All changes noted returned to normal within 30 days postflight so that the processes appear to be transient and self limited. The cardiovascular system seems to adapt quite readily to zero-g, and more importantly it is capable of readaptation to one-g after long duration space flight. Repeated exposures to zero-g also appear to have no detrimental effects on the cardiovascular system.

Bergman, S. A., Jr.↗
NASA NTRS1978

Electromechanical flight control actuator, volume 2

Schematic diagrams are given for both the four-channel electromechanical actuator and the single-channel power electronics breadboard. Detailed design data is also given on the gears used in the differential gearbox and a copy of the operations manual for the system is included. Performance test results are given for the EMA motor and its current source indicator, the drive control electronics, and the overall system. The power converter waveform test results are also summarized.

Source record↗