Wind Tunnel Lined for Sound
NASA HAS COMPLETED
A SOUND INSULATION project in the world's largest wind tunnel to
help the U.S. aircraft industry design quieter engines and test
advanced helicopters and other new aircraft. During the refurbishing
that began in September 1994, workers installed a dense acoustic
lining in the National Full-Scale Aerodynamics Complex (NFAC) at
NASA's Ames Research Center at Moffett Field, California. The purpose
was to reduce the test section's background noise and echoes during
jet engine tests in the wind tunnel's 40-foot by 80-foot test section.
Background noise and echoes adversely affect the accuracy of sound
measurement during jet engine tests, according to Project Manager
Joe Hurlbut of Ames. Hurlbut said the refurbished wind tunnel will
enable engineers to conduct very accurate acoustic tests.
Insulation material and 1,600 acoustic panels in the floor, walls
and ceiling of the wind tunnel's 40-foot by 80-foot test section
were installed. The new custom-made metal gray panels are made of
perforated sheet metal bonded to stainless steel mesh, similar to
that used in automobile oil filters. The insulation material behind
the panels is similar to the spun fiberglass commonly used to insulate
NASA engineers also upgraded the wind tunnel's control system
to improve efficiency, and National Electric Company of Columbus,
Ohio, modified the wind tunnel's main fan drive system to reduce
noise. The Scott Company of San Leandro, California, served as the
project's primary contractor.
Each of the wind tunnel's six fan-drive motors has 22,500 horsepower,
for a total of 135,000 horsepower. These motors are capable of generating
air speeds of up to 345 miles per hour in the 40-foot by 80-foot
test section and up to 115 miles per hour in the 80-foot by 120-foot
test section. Each of the six fans measures 40 feet in diameter
and contains 15 variable pitch blades. The wooden blades weigh 800
pounds each and measure 15 feet in length.
Hurlbut said a series of technical problems, including the discovery
of cracks in the fan blades in May 1995, delayed the completion
of the project. The cracks have since been sealed with an epoxy
resin, and the blades have been wrapped with a carbon and fiberglass
composite to strengthen them.
Tests are scheduled to resume in the wind tunnel following the
completion of the integrated systems testing in October. In November,
Ames engineers are scheduled to begin a two-month test of the Subsonic
High Alpha Research Concept (SHARC) aircraft. Sponsored by the Department
of Defense and the U.S. Air Force, SHARC is a design concept being
studied to improve the maneuverability of jet fighter aircraft.
For more information, contact Joe Hurlbut at Ames Research Center.
Call: 650/604-4953, Fax: 650/604-7197, E-mail: firstname.lastname@example.org
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