Mechanical & Fluid Systems

Mechanisms for Achieving Non-Sinusoidal Waveforms on Stirling Engines

The current state-of-the-art Stirling engines use sinusoidal piston and displacer motion to drive the thermodynamic cycle and produce power. Research performed at NASA Glenn has shown that non-sinusoidal waveforms have the potential to increase Stirling engine power density, and could possibly be used to tailor engine performance to the needs of a specific application. However, the state-of-the-art Stirling engine design uses gas springs or planar springs that are very nearly linear, resulting in a system that resonates at a single frequency. This means that imposing non-sinusoidal waveforms, consisting of multiple frequencies, requires large forces from the drive mechanism (either the alternator or the crank shaft). These large forces increase losses, and increase the size and requirements of the control system. This innovation aims to reduce the external forcing requirements by introducing internal mechanical components that provide the forces necessary to achieve the desired waveforms.

Posted in: Briefs, Mechanical Components, Mechanics, Motion Control, Alternators, Alternators, Crankshafts, Engine efficiency, Stirling engines
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RFID Cavity

Potential applications include inventory tracking for containers such as waste receptacles or storage containers.

This technology provides a method for interrogating collections of items with radio-frequency identification (RFID) tags. It increases the read accuracy, meaning that more of the item tags will be successfully read. It also permits smaller tag antennas than would otherwise be necessary.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Downsizing, Antennas, Antennas, Product development, Radio-frequency identification, Reliability, Reliability
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Method for Asteroid Volatile Extraction in Space

The method would support human missions to Mars or other distant objects.

Some meteorites representative of certain classes of asteroids are 25% or more water by weight. This is consistent with infrared spectra of some asteroids, indicating hydrated minerals are abundant in some varieties of carbonaceous chondrite asteroids. Since water is very valuable in space, it would be desirable to be able to process asteroids to recover this water and other volatiles. The Asteroid Redirect Mission concept has formulated a method for returning asteroids of 1,000-ton mass into the Earth-Moon system orbit using only ~10 tons of propellant. If ~25% of that returned asteroid mass were recovered as volatiles and solar power used to make those volatiles into propellant, then the overall system would generate approximately 25 times as much propellant as it uses. This could be used to make sustainable human missions to Mars or otherwise spread humanity into the solar system.

Posted in: Briefs, Aerospace, Fluid Handling, Mechanical Components, Mechanics, Water reclamation, Life support systems, Booster rocket engines, Solar rocket engines, Spacecraft
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Improving Stirling Engine Performance Through Optimized Piston and Displacer Motion

Stirling engines typically achieve high efficiency, but lack power density. Low power density prevents them from being used in many applications where internal combustion engines are viable competitors, and increases system costs in applications that require Stirling engines. This limits their operating envelope in both terrestrial and space applications. Sinusoidal piston and displacer motion is one of the causes of low power density. Previous work proposed solving this problem by replacing sinusoidal waveforms with waveforms that more closely approximate those of the ideal Stirling cycle. However, when working with real engines, imposing ideal waveforms has been shown to reduce power density and efficiency due to increased pressure drop through the regenerator and heat exchangers.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Motors & Drives, Engine efficiency, Pistons, Stirling engines
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Magnetic Relief Valve

A magnetically retained pressure-relief valve enables quick-open on/off operation when overpressure is reached.

Inventors at NASA’s Kennedy Space Center have developed a magnetically retained, fast-response pressure relief valve that is designed to fully open at precise cracking pressures, and that operates in a fully open/fully closed manner. The use of a magnetically controlled relief valve, as opposed to a spring-based relief valve, enables quick-open on/off relief operation when overpressure is reached. This is due to the rapid decay of the magnetic field as the fluid medium pushes the valve poppet to an open position. Spring-based relief valves require increasing pressure and force to continually compress the spring and open the relief valve. This requirement greatly complicates the design of a system relief mechanism. A magnetic relief valve reduces these design complexities by eliminating the spring.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Magnetic materials, Valves
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Work Piece Cleaning Apparatus and Method with Pulsating Mixture of Liquid and Gas

NASA Goddard’s scientists have developed a novel, volatile organic compound (VOC)-free system for cleaning tubing and piping that significantly reduces cost and carbon consumption. The innovative technology enables the use of deionized water in place of costlier isopropyl alcohol (IPA), and does not create any waste for which costly disposal is usually required. It uses nitrogen bubbles in water, which act as a scrubbing agent to clean equipment. The cleaning system quickly and precisely removes all foreign matter from tubing and piping.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Water, Tools and equipment, Gases
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Safety Drain System for Fluid Reservoir

Researchers at NASA’s Marshall Space Flight Center have developed a system that reduces the entrapment risks associated with a pool or spa’s recirculation drain. The technology prevents hazards caused by suction forces on the body, hair, clothing, or other articles. Employing a novel configuration of drainage openings along with parallel paths for water flow, the system redistributes force over a much larger area, minimizing suction force at any localized area. With more efficient drainage and recirculation, the device improves performance, increases safety, and decreases operating costs. The technology can also provide thorough chemical mixing, which improves processes in systems and allows continued operation in the event of localized debris clogging a portion of the recirculation area. All of these benefits come without a protrusive drain cover, leaving the area safe and aesthetically pleasing.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Water, Human factors, Parts
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Locking Mechanism for a Flexible Composite Hinge

This compact, self-deploying and locking boom has application in deployable booms, commercial satellites, and robotic vehicles that require high-data-rate communications.

Composites have excellent strength characteristics, are lightweight, and are increasingly being used in space applications. However, they are highly inflexible and require hinged joints when used as deployable structures. This is a challenge for CubeSats/SmallSats, as the hinges and actuation mechanisms get very small and require multiple custom precision parts. A method of impregnating carbon fibers with a silicone matrix has been developed, which makes the composite flexible. This also makes it self-deploying, as the strain energy in the fibers will cause it to straighten. Unfortunately, a purely flexible beam does not have the required rigidity to maintain dimensions accuracy, as it can sag.

Posted in: Briefs, Mechanical Components, Mechanics, Composite materials, Lightweight materials, Materials properties, Parts, Satellites
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Temperature-Compensating PMT Housing

Shrinking or contracting light guides is a problem when photomultiplier tubes (PMTs) are glued to the guides. If there is no way to allow movement of the PMTs, when the temperature goes down, the light guide contracts and breaks the glue joint. The PMTs cannot be left loose to rattle around inside the detector. They must be held precisely, yet gently, and allowed to move.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Optics, Optics, Thermodynamics, Thermodynamics, Adhesives and sealants
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Jet Engine Exhaust Nozzle Flow Effector

Shape memory alloy provides variable shape control of aircraft structure through actively deformable surfaces.

NASA’s Langley Research Center has created novel flow effector technology for separation control and enhanced mixing. The technology allows for variable shape control of aircraft structure through actively deformable surfaces. The flow effectors are made by embedding shape memory alloy actuator material in a composite structure. When thermally actuated, the flow effector deflects into or out of the flow in a prescribed manner to enhance mixing or induce separation for a variety of applications, including aeroacoustic noise reduction, drag reduction, and flight control. NASA developed the active flow effectors for noise reduction as an alternative to fixed-configuration effectors, such as static chevrons, that cannot be optimized for airframe installation effects or variable operating conditions, and cannot be retracted for off-design or failsafe conditions.

Posted in: Briefs, Aerospace, Aviation, Mechanics, Alloys, Smart materials, Nozzles, Exhaust pipes, Jet engines
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