Upgrades to the 150-psig combustion air piping system servicing the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center have resulted in significant improvements to the test facility and a safer, quieter working environment for Center employees. Upgrades were commissioned by Glenn’s Facility Management and Planning Office and were accomplished through collaborative efforts of AAPL facility staff, Glenn’s Facilities Division staff, and ZIN Technologies and Mainthia Technologies Incorporated contractors. Work entailed replacement of facility flow-control butterfly valves with low-noise V-Ball valves, installation of a noise-attenuator plate (an adjunct and complementary component to new low-noise valves), replacement of flow-metering venturi and associated instrumentation, fortification of piping supports and pipe sections to meet national consensus code requirements, removal of pipe penetrations through the interior inlet-tunnel walls, and upgrade of facility noise-barrier walls to achieve roughly 55-dBA noise attenuation through the walls. The total project investment was about ¤120,000.
Result of facility modifications on AAPL test chamber background noise at a freejet flow condition of mach 0.30 (as measured at the 90° microphone position).
Long description of figure 1.
The most significant performance result of this upgrade was a 20-dB reduction of freejet background noise within the test chamber near the loudest test condition over the frequency range of interest for model jet testing. In a facility where a few decibels of improvement in test hardware are significant, a 20-dB reduction in the facility background noise floor is enormous. This enables a whole new category of quieter model jet hardware to be tested at the AAPL, and it improves the quality of jet-noise acoustic measurements at most levels of interest. It also makes the AAPL more competitive with benchmark facilities such as GE Cell 41 and the Boeing Low Speed Acoustic Facility. Other performance benefits resulting from the upgrade include improved flow-metering accuracy and ease of setting and maintaining test-flow conditions.
The most significant safety benefit of the work was the hard-to-quantify improvement in piping system safety, reliability, and confidence achieved by upgrading to meet or exceed national consensus code requirements. Perhaps the most appreciated health and safety benefit was a 5- to 6-dBA reduction in AAPL exterior piping noise, which produced a quieter and less annoying environment for Glenn employees working or traveling in the AAPL vicinity.
Find out more about this research:
AAPL: http://facilities.grc.nasa.gov/aapl
Glenn’s Acoustics Branch: http://www.grc.nasa.gov/WWW/Acoustics/
Last updated: December 15, 2007
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