Mechanical & Fluid Systems

Laser Anemometer Measures Flow in a Centrifugal Compressor

High-resolution data are representative of flows in practical centrifugal compressors.

Detailed measurements of complex flow fields within the NASA Low Speed Centrifugal Compressor (LSCC) have been acquired. The measurement data provide insight into the fundamental physics of flow in centrifugal compressors, and can be used to assess computational fluid dynamics codes and to develop flow-physics models. The resultant benefit is better predictive computational tools and shorter design cycle times.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Computational fluid dynamics, Measurements, Compressors, Test equipment and instrumentation

Magnetostrictive Inertial-Reaction Linear Motors

Fine positioning could be achieved at temperatures from near absolute zero to ambient.

Linear-translation motors containing inertial-reaction masses driven by magnetostrictive actuator elements are undergoing development. These motors could be used to make fine position adjustments in diverse scientific and industrial instruments that operate at temperatures ranging from near absolute zero to room temperature; for example, they could be used to drive translation stages in scanning tunneling microscopes that operate at liquid-helium temperature (4 K), or to move cryogenic-temperature optical elements that must be located at long but precise distances from each other (as in interferometers). [These motors should not be confused with proposed magnetostrictive motors that would move in "inchworm" fashion and would be used for similar purposes, described in "Magnetostrictive Actuators for Cryogenic Applications," NASA Tech Briefs, Vol. 20, No. 3 (March 1996), page 84.]

Posted in: Briefs, Mechanical Components, Mechanics, Optics, Sensors and actuators, Optics, Sensors and actuators, Electric motors, Test equipment and instrumentation, Industrial vehicles and equipment

Pulse-tube Refrigerator Unit

The working fluid for this new device is helium, which is nontoxic to humans and harmless to the environment.

Pulse-tube Refrigerators can be operated over a wide range of temperatures. These units can be used in numerous space and commercial refrigeration applications, including food refrigerator/freezers, laboratory freezers, and freeze dryers. Pulse-tube Refrigerators can also be used to cool detectors and electronic devices.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Cooling, Refrigerants

Deflection of Stretched Circular Membrane Under Pressure

Previously reported equations are generalized to account for a stretch preload.

Equations have been derived to describe the deflection of a circular membrane under both in-plane and transverse loads. More specifically, the equations describe the radial (in-plane) and perpendicular-to-the-plane deflections for the case of a circular membrane that has been stretched at its periphery with a uniform preload to keep it taut, then clamped rigidly at its periphery, and then subjected to differential pressure.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Mathematical models, Test procedures

Improved Lifetime for Stirling Cryogenic Coolers

Core-technology advances extend maintenance-free operating life of coolers to more than 50,000 hours.

A Stirling cooler is a mechanical system that approximates the ideal gas cycle. Often associated with airborne or portable cooling applications that require compact design and low input power, Stirling coolers are suitable for such applications because of their high efficiency. Compared to Gifford-McMahon and Joule-Thomson cycles, Stirling offers more than twice the cooling performance in the capacity range from 1-100 W. The coolers have a variety of military and commercial applications in infrared receivers and thermal imaging equipment.

Posted in: Briefs, Mechanical Components, Mechanics, Imaging, Imaging and visualization, Imaging, Imaging and visualization, Cooling, Gases, Thermal testing

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