Mechanical & Fluid Systems

Periodically Discharging, Gas-Coalescing Filter

In effect, small bubbles would be made to coalesce into very large ones.

A proposed device would remove bubbles of gas from a stream of liquid (typically water), accumulate the gas, and periodically release the gas, in bulk, back into the stream. The device is intended for use in a flow system (1) in which there is a requirement to supply bubble-free water to a downstream subsystem and (2) that includes a sensor and valves, just upstream of the subsystem, for sensing bubbles and diverting the flow from the subsystem until the water stream is again free of bubbles. By coalescing the gas bubbles and then periodically releasing the accumulated gas, the proposed device would not contribute to net removal of gas from the liquid stream; nevertheless, it would afford an advantage by reducing the frequency with which the diverter valves would have to be activated.

Posted in: Briefs, Mechanical Components, Mechanics, Sensors and actuators, Product development, Gases, Valves
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System Would Detect Foreign-Object Damage in Turbofan Engine

Vibration-sensor and gas-path-analysis data would be fused.

A proposed data-fusion system, to be implemented mostly in software, would further process the digitized and preprocessed outputs of sensors in a turbofan engine to detect foreign-object damage (FOD) [more precisely, damage caused by impingement of such foreign objects as birds, pieces of ice, and runway debris]. The proposed system could help a flight crew to decide what, if any, response is necessary to complete a flight safely, and could aid mechanics in deciding what post-flight maintenance action might be needed.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Computer software and hardware, On-board diagnostics, On-board diagnostics (OBD), Sensors and actuators, Fans, Turboprop engines
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Recovering Residual Xenon Propellant for an Ion Propulsion System

Most of the otherwise unusable xenon is recovered.

Future nuclear-powered Ion-Propulsion- System-propelled spacecraft such as Jupiter Icy Moon Orbiter (JIMO) will carry more than 10,000 kg of xenon propellant. Typically, a small percentage of this propellant cannot be used towards the end of the mission because of the pressure drop requirements for maintaining flow. For large missions such as JIMO, this could easily translate to over 250 kg of unusable xenon.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Recycling, Nuclear energy, Propellants, Spacecraft fuel
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Predicting Tail Buffet Loads of a Fighter Airplane

Airframes can be designed to be more robust.

Buffet loads on aft aerodynamic surfaces pose a recurring problem on most twin-tailed fighter airplanes: During maneuvers at high angles of attack, vortices emanating from various surfaces on the forward parts of such an airplane engine inlets, wings, or other fuselage appendages) often burst, immersing the tails in their wakes. Although these vortices increase lift, the frequency contents of the burst vortices become so low as to cause the aft surfaces to vibrate destructively.

Posted in: Briefs, Mechanical Components, Mechanics, Aerodynamics, Military aircraft
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System Finds Horizontal Location of Center of Gravity

Mass and center-of-mass data are updated at a rate of = 267 Hz.

An instrumentation system rapidly and repeatedly determines the horizontal location of the center of gravity of a laboratory vehicle that slides horizontally on three air bearings (see Figure 1). Typically, knowledge of the horizontal center-of- mass location of such a vehicle is needed in order to balance the vehicle properly for an experiment and/or to assess the dynamic behavior of the vehicle.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Bearings, Test equipment and instrumentation, Vehicle dynamics
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Water Containment Systems for Testing High-Speed Flywheels

Water-filled containers are stacked like bricks.

Water-filled containers are used as building blocks in a new generation of containment systems for testing high-speed flywheels. Such containment systems are needed to ensure safety by trapping high-speed debris in the event of centrifugal breakup or bearing failure. Traditional containment systems for testing flywheels consist mainly of thick steel rings. While steel rings are effective for protecting against fragments from conventional and relatively simple metal flywheels, they are also expensive. Moreover, it is difficult and expensive to configure steel-ring containment systems for testing of advanced flywheel systems that can include flywheels made of composite materials, counter-rotating flywheels, and/or multiple flywheels rotating about different axes. In contrast, one can quickly, easily, and inexpensively stack waterfilled containers like bricks to build walls, (and, if needed, floors, and ceilings) of sufficient thickness to trap debris traveling in any debris traveling in any possible direction at the maximum possible kinetic energy that could be encountered in testing a given flywheel system.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Containers, Flywheels, Test procedures
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Mechanically Biased, Hinged Pairs of Piezoelectric Benders

Unit cells can be stacked to obtain greater stroke for a given voltage.

The upper part of the figure depicts an actuator that comprises two mechanically biased piezoelectric benders hinged together at their ends and equipped with tabs at their mid-length points for attachment to the relatively moving objects that are to be actuated. In the example of the figure, the attachment tabs are labeled to indicate that the actuator is used to drive a pump piston relative to a base plate. Actuators of this type could be used to drive lowpower, small-volume pumps in consumer, medical, and aerospace applications, and to generate and measure linear displacements in such robotic applications as teleoperation and tactile feedback. Each bender is a bimorph — a unitary plate that comprises an upper and a lower piezoelectric layer plus electrode layers. Benders may also be made of several layers arranged to produce the same effect at the lower operating voltages. As stated above, each bender is mechanically biased; it is fabricated to have a small permanent curvature (the bias curvature) in the absence of applied voltage. As on other bimorphs, the electrical connections on each bender are arranged so that an applied voltage of suitable polarity causes the upper layer to expand and the lower layer to contract. In this case, the net effect of applying the voltage is that the plate becomes more concave as viewed from below. Conversely, an applied voltage of the opposite polarity causes the plate to become less concave as viewed from below.

Posted in: Briefs, Mechanical Components, Mechanics, Electrical systems, Sensors and actuators, Electrical systems, Sensors and actuators
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Oscillating-Linear-Drive Vacuum Compressor for CO2

A vacuum compressor has been designed to compress CO2 from ˜1 psia (˜6.9 kPa absolute pressure) to ˜75 psia (˜0.52 MPa), to be insensitive to moisture, to have a long operational life, and to be lightweight, compact, and efficient. The compressor consists mainly of (1) a compression head that includes hydraulic diaphragms, a gas-compression diaphragm, and check valves; and (2) oscillating linear drive that includes a linear motor and a drive spring, through which compression force is applied to the hydraulic diaphragms. The motor is driven at the resonance vibrational frequency of the motor/spring/compression-head system, the compression head acting as a damper that takes energy out of the oscillation. The net effect of the oscillation is to cause cyclic expansion and contraction of the gas-compression diaphragm, and, hence, of the volume bounded by this diaphragm. One-way check valves admit gas into this volume from the low-pressure side during expansion and allow the gas to flow out to the high-pressure side during contraction. Fatigue data and the results of diaphragm stress calculations have been interpreted as signifying that the compressor can be expected to have an operational life of >30 years with a confidence level of 99.9 percent.

Posted in: Briefs, Mechanical Components, Mechanics, Carbon dioxide, Compressors
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Rotating Vessels for Growing Protein Crystals

Rotation would ameliorate adverse effects of gravitation.

Rotating vessels have been proposed as means of growing larger, more nearly uniform protein crystals than would otherwise be possible in the presence of normal Earth gravitation. Heretofore, nonrotating vessels have been used.

Posted in: Briefs, Mechanical Components, Mechanics, Research and development, Materials properties
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Tool Measures Depths of Defects on a Case Tang Joint

Precise measurements can be made consistently.

A special-purpose tool has been developed for measuring the depths of defects on an O-ring seal surface. The surface lies in a specially shaped ringlike fitting, called a “capture feature tang,” located on an end of a cylindrical segment of a case that contains a solid-fuel booster rocket motor for launching a space shuttle. The capture feature tang is a part of a tang-and-clevis, O-ring joint between the case segment and a similar, adjacent cylindrical case segment. When the segments are joined, the tang makes an interference fit with the clevis and squeezes the O-ring at the side of the gap.

Posted in: Briefs, Mechanical Components, Mechanics, Finite element analysis, Measurements, Tools and equipment, Seals and gaskets, Booster rocket engines
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