Hydroelectric plants make life miserable for migrating fish. Salmon ladders may lead to higher water behind the dam, but the only way back is through the generator turbine blades. Some 15% of the fish never make it.
NREC's proprietary software programs COMIG for CAE and VISION for CFD, helped create the impeller shape. Serpentine impeller gie migrating fish safe passage through hydroelectric power stations.
Reasons include the sudden pressure drop, as well as cutting action of the blades themselves. A new impeller addresses these problems by 1) decreasing blade number from the usual 13-18 to three, and 2) lengthening the distance over which the pressure drop occurs by a factor of ten.
A collaborative effort between NREC and Alden Research Labs, Holden, MA, the fish-safe turbine reduces kill rate to less than one-half percent. Turbine efficiency drops only slightly from the 94% range to about 90%.
James Watts, Northern Research and Engineering Corp., 39 Olympia Ave., Woburn, MA 01801-2073, 617-935-9050.
| Patented microprocessor/surface mount electronic circuit in the unit uses the change in flux density to determine the proportion of clogging in the filter.
Most of today's hydraulic filter monitors provide only a yes/no indication of the filter's status. Either it's completely clogged, or it isn't. As a result, the user doesn't know there's a problem until it's too late.
Engineers at Western Filter Corp., however, have found a better way. Their Intelligent Filter Indicator (IFI) tells how much the filter is clogged. To accomplish that, the IFI device uses a piston containing a magnet. As the filter clogs, differential pressure across it increases, causing the piston to move. When the magnet in the piston moves closer to a Hall Effect sensor, the sensor detects a change in magnetic flux density. To account for the effect of temperature changes, the circuitry also reads temperature data from a thermistor and, as a result, is able to prevent false indications due to "cold start" conditions.
With the IFI, users can have continuous, remote readouts of pressure and differential pressure for factory-wide monitoring of filters in real time. As a result, they can replace filters before they are completely clogged, thus prolonging the life of hydraulic equipment.
Kanwar Suri, Western Filter Corp. , 26235 Technology Drive, Valencia, CA 91355, 805-295-0800.
Balanced-pilot check valve
| The balanced check has been cycle tested without lubrication for 10 million cycles with no sign of wear or failure.
Most ball- or poppet-type check valves that lock pneumatic cylinders in position, require high opening forces. Forces wear on the valve each time it's cycled. A balanced design increases valve life by reducing operating forces.
With air trapped behind the poppet (output side), the checked piston tries to pull the poppet off its seat. Slightly increasing the pressure area behind the poppet makes it larger than the piston area, and partially biases the poppet to its seat. With pressure applied to the pilot, the force required to open the poppet is the small difference in pressure between poppet and balancing piston.
Norbert J. Kot, NGT LLC, P.O. Box 5223, Elm Grove, WI 53122-5223, (414) 782-6125 or Fax (414) 782-0197.E-mail: firstname.lastname@example.org or www.ngtvalves.com
| ERM pumps use engaged teeth to maintain seal instead of the tangential surface of two lobed rotors. Higher vacuum levels and less leakage result.
Large working teeth, superimposed on the primary rotor's involute teeth, engage large grooves on the secondary rotor. Working teeth compress one chamber to expel fluid, while the other chamber expands to draw in fluid.
This design reduces noise and vibration by eliminating eccentric rotating masses found in most fluid-compressor designs. Applications include compressors, hydraulic pumps and motors, metering and vacuum pumps, hydraulic stepless speed regulators, and rotary engines.
Frank Hu, 4444 Thrushfield Ct., Flint, MI 48507, (810) 257-3966.