Mechanical & Fluid Systems

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, Mechanical Components, Mechanics, Fluid Handling, Motors & Drives

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Pedal Position Sensing in Heavy-Duty Vehicles

Pedal position detection is nothing new when it comes to operation of heavy duty equipment. However, the age old system operation of mechanical linkages between the pedal and the engine just might be coming to an end. New sensor technology is now enabling non-contact, drive-by-wire that can reduce total system cost while standing up to the harsh environments of off highway equipment.

Posted in: White Papers, Mechanical Components, Fluid Handling, Motion Control, Data Acquisition, Sensors

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Machine Positioning Uncertainty with Laser Interferometer Feedback

Laser interferometers are used as a measurement reference for machine correction and accuracy validation in the production of many high precision motion systems. Under controlled environmental conditions, laser interferometer measurement can provide low measurement uncertainty relative to the achievable accuracy of most commonly used motion control devices. As such, when processes require the utmost precision, laser interferometer measurement near the machine’s work point is frequently used as the feedback mechanism for machine control. In these instances, the use of laser interferometry to characterize the machine’s motion is unjustified because the measurement uncertainty of the metrology system is equivalent or higher than the motion error. The accuracy of these machines’ motion must be equated to an uncertainty in the feedback system’s measurement of the defined work point’s motion.

Posted in: White Papers, Mechanical Components, Mechanics

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How to Make Low Flow Measurements Using Turbine Flow Meters

Accurate low flow measurement represents significant challenges in many applications. Some typical low flow applications in the aerospace market include: small UAV fuel consumption, satellite thruster fuel consumption, and fuel/chemical/water injection. The low dynamic energy associated with flow rates down to 0.001 GPM exceed the capabilities of most mechanical flow meters and force the use of less accurate flow meter technologies.

Posted in: White Papers, Instrumentation, Mechanical Components, Data Acquisition, Sensors

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Magnetic Relief Valve

A side view of the relief valve sections (left), and a view inside the relief valve (right). 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, Mechanical Components, Mechanics, Fluid Handling

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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, Mechanical Components, Mechanics, Fluid Handling

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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, Mechanical Components, Mechanics, Fluid Handling

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