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The operating envelope of the Abe Silverstein 10-
by 10-Foot Supersonic Wind Tunnel (10x10 SWT) at the NASA Lewis
Research Center was recently expanded to include operation at
subsonic test section speeds. This new capability generates test
section air speeds ranging from Mach 0.05 to 0.35 (32 to 240 kn).
Most of the expansion in air speed range was obtained by running
the tunnel's main compressor at much lower speeds than ever before.
The compressor drive system, consisting of four large electric
motors, was run with only one or two motors energized to obtain
the lower compressor speed range. This new capability makes the
10x10 SWT more versatile and gives U.S. researchers an enhanced
ability to perform subsonic propulsion and aerodynamic testing.
The 10x10 SWT was designed and built in the early
1950's as a supersonic wind tunnel capable of test section speeds
of about 2 to 3.5 Mach. However, in the late 1970's, tunnel operation
was modified so that subsonic test section speeds could be obtained,
roughly 0.1 to 0.35 Mach. The tunnel main compressor was run near
its minimum speed, around 565 rpm, with all four of the drive
motors energized. This operation caused very high air flow rates
and vibrations in the main compressor bypass pipeline and was
later stopped because of suspected structural damage. Because
of the current high demand for subsonic testing, subsonic operation
of the 10x10 SWT was revisited in early 1996.
The new subsonic capability resulted from two efforts. Initially, the old method of subsonic operation was investigated to determine which part of the speed range caused structural problems for the compressor bypass pipeline. Vibration, strain, and displacement instrumentation placed on the bypass line showed that structural vibrations were prohibitive at test section air speeds below Mach 0.25 but were tolerable at test section air speeds of about Mach 0.25 to 0.35.
Next, and more importantly, the main compressor drive
motor operation was modified to further reduce the compressor
operating speed and, therefore, the amount of compressor bypass
line flow. The number of motors energized was reduced from four
to one or two to achieve new compressor operating speeds, as low
as 220 rpm. The resulting test section air speeds range from about
0.05 to 0.25 Mach. Also, by reducing the compressor speed and
the number of drive motors, the electric power consumption was
significantly reduced, providing energy and dollar savings. The
first test program utilizing the new capability was run in the
fall of 1996.
Find out more about the Abe Silverstein 10- by 10-Foot Supersonic Wind Tunnel.
Previous articleLast updated April 29, 1997
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