Tech Briefs

Bearing-Seal System for Safe Motion Transfer in Deep Submersible Pressure Vessels

Elastomeric bearings permit leak-free transfer of rotary motion through the hull. Designers of deep submersibles are reluctant to use conventional shafts and seals to penetrate the hulls of deep sub- mersible, pressure vessels fearing seal failure under extreme pressures. The unique design of this patented system, designated LAMIFLEX®, incorporates elastomeric bearings in order to achieve an absolute hermetic seal and permit leak-free transfer of rotary motion up to at least 15 degrees through the hull of these highly pressurized vessels. External functions, such as control surface deflection, can be driven internally with inherent safety and backup. There are no sliding surfaces (packings, lip, or face seals) that could fail. It also exhibits a smooth spring-like reaction and limited shaft movement without friction. The new designs have been implemented and tested at pressures of 10,000 psi for more than a million cycles at ±15 degrees with no leakage.

Posted in: Mechanics, Briefs

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Larger-Stroke Piezoelectrically Actuated Microvalve

Liquids carrying small particles could be handled. A proposed normally-closed microvalve would contain a piezoelectric bending actuator instead of a piezoelectric linear actuator like that of the microvalve described in the preceding article. Whereas the stroke of the linear actuator of the preceding article would be limited to ≈6 μm, the stroke of the proposed bending actuator would lie in the approximate range of 10 to 15 μm — large enough to enable the microvalve to handle a variety of liquids containing suspended particles having sizes up to 10 μm. Such particulate-laden liquids occur in a variety of microfluidic systems, one example being a system that sorts cells or large biomolecules for analysis.

Posted in: Mechanics, Briefs, TSP

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Piezoelectrically Actuated Microvalve for Liquid Effluents

Power consumption and size would be reduced. Modifications have been proposed to effect further improvement of the device described in “Improved Piezo- electrically Actuated Microvalve” (NPO-30158), NASA Tech Briefs, Vol. 26, No. 1 (January 2002), page 29. To recapitulate: What is being developed is a prototype of valves for microfluidic systems and other microelectromechanical systems (MEMS). The version of the valve reported in the cited previous article included a base (which contained a seat, an inlet, and an outlet), a diaphragm, and a linear actuator. With the exception of the actuator, the parts were micromachined from silicon. The linear actuator consisted of a stack of piezoelectric disks in a rigid housing. To make the diaphragm apply a large sealing force on the inlet and outlet, the piezoelectric stack was compressed into a slightly contracted condition during assembly of the valve. Application of a voltage across the stack caused the stack to contract into an even more compressed condition, lifting the diaphragm away from the seat, thereby creating a narrow channel between the inlet and outlet. The positions of the inlet and outlet, relative to the diaphragm and seat, were such that the inlet flow and pressure contributed to sealing and thus to a desired normallyclosed mode of operation.

Posted in: Mechanics, Briefs, TSP

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Methane Clathrate Hydrate Prospecting

Methane hydrate deposits would be detected indirectly through thermal, magnetic, and electric measurements. A method of prospecting for methane has been devised. The impetus for this method lies in the abundance of CH4 and the growing shortages of other fuels. The method is intended especially to enable identification of subpermafrost locations where significant amounts of methane are trapped in the form of methane gas hydrate (CH4·6H2O). It has been estimated by the U.S. Geological Survey that the total CH4 resource in CH4·6H2O exceeds the energy content of all other fossil fuels (oil, coal, and natural gas from non-hydrate sources). Also, CH4·6H2O is among the cleanest-burning fuels, and CH4 is the most efficient fuel because the carbon in CH4 is in its most reduced state. The method involves looking for a proxy for methane gas hydrate, by means of the combination of a thermal-analysis submethod and a field submethod that does not involve drilling. The absence of drilling makes this method easier and less expensive, in comparison with prior methods of prospecting for oil and natural gas.

Posted in: Briefs, TSP

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Slotting Fins of Heat Exchangers To Provide Thermal Breaks

Heat exchangers that include slotted fins (in contradistinction to continuous fins) have been invented. The slotting of the fins provides thermal breaks that reduce thermal conduction along flow paths (longitudinal thermal conduction), which reduces heat-transfer efficiency. By increasing the ratio between transverse thermal conduction (the desired heat-transfer conduction) and longitudinal thermal conduction, slotting of the fins can be exploited to (1) increase heat-transfer efficiency (thereby reducing operating cost) for a given heat-exchanger length or to (2) reduce the length (thereby reducing the weight and/or cost) of the heat exchanger needed to obtain a given heat-transfer efficiency. By reducing the length of a heat exchanger, one can reduce the pressure drop associated with the flow through it. In a case in which slotting enables the use of fins with thermal conductivity greater than could otherwise be tolerated on the basis of longitudinal thermal conduction, one can exploit the conductivity to make the fins longer (in the transverse direction) than they otherwise could be, thereby making it possible to make a heat exchanger that contains fewer channels and therefore, that weighs less, contains fewer potential leak paths, and can be constructed from fewer parts and, hence, reduced cost.

Posted in: Briefs

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Scanning Microscopes Using X Rays and Microchannels

In principle, resolutions of the order of nanometers could be attained. Scanning microscopes that would be based on microchannel filters and advanced electronic image sensors and that utilize x-ray illumination have been proposed. Because the finest resolution attainable in a microscope is determined by the wavelength of the illumination, the xray illumination in the proposed microscopes would make it possible, in principle, to achieve resolutions of the order of nanometers — about a thousand times as fine as the resolution of a visible-light microscope. Heretofore, it has been necessary to use scanning electron microscopes to obtain such fine resolution. In comparison with scanning electron microscopes, the proposed microscopes would likely be smaller, less massive, and less expensive. Moreover, unlike in scanning electron microscopes, it would not be necessary to place specimens under vacuum.

Posted in: Briefs, TSP

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Software Simulates Chewing Biomechanics for Anthropology Study

Research could lay the groundwork for studies of extinct early humans. Fossils of primates and early humans exhibit great diversity in the size and shape of the jaw, teeth, and facial skeleton. Anthro- pologists theorize that these different skull forms were evolutionary adaptations to chewing different types of food. Dr. David S. Strait, anthropologist and assistant professor at the New York College of Osteopathic Medicine of the New York Institute of Technology (NYIT), is testing these theories by simulating the chewing biomechanics of living primates with ALGOR finite element analysis (FEA) software. Dr. Strait’s research may help to explain why there is such diversity among living primates, and could lay the groundwork for future studies of extinct early humans.

Posted in: Bio-Medical, Briefs

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