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Wind Tunnel High Temperature Heater Element

Description:

OBJECTIVE: To develop and demonstrate a scalable electrically-powered heater element to generate 2800 degree Fahrenheit continuous airflow in the test section of a supersonic/hypersonic wind tunnel. DESCRIPTION: To replicate the conditions experienced by vehicles flying at high Mach number, sustained airflow temperatures of 2800 degrees Fahrenheit are required. Some tunnels, such as the NASA Langley Research Center 8-ft High Temperature Tunnel (HTT) facility and the NASA Glenn/Plum Brook Hypersonic Tunnel Facility (HTF) have not only met this temperature requirement, but have exceeded it; however, the solutions chosen have provided insufficiently short run times, have introduced undesirable test media from combustion products introduced into the flow in the case of vitiation heated facilities, such as HTT, or from foreign object debris (FOD) into the flow in the case of facilities like the HTF, and/or have required difficult or excessive levels of maintenance. Heater elements for high Mach wind tunnels, in general, have been in use for decades now, ranging from combustion air systems with run times on the order of seconds to combinations of gas heat exchangers and electric boost heat which may run continuously. However, the availability of ground test facilities which can provide large clean air mass air flows (~150 lbm/sec) and high temperatures (~2800 deg F) continuously that closely simulates flight conditions has proven elusive thus far. A favorable heater element, or group of elements, will be capable of being installed in a 1-3 foot diameter duct, withstand static pressures of 2000 psi, provide continuous operation for periods lasting up to four hours, and have a minimum total expected life of 200 hours at maximum operating condition. Electrical and mechanical properties will not be noticeably degraded due to oxidation and other phenomena during the 200-hour operating life. PHASE I: A single heater element, or group of elements, will be constructed and demonstrated. Current, voltage, thermal shock, thermal expansion, and mass/structural characteristics will be examined. A candidate integrated heater final design concept to be developed as a Phase II, and performance validated in a government-furnished wind tunnel facility, will be delivered. PHASE II: The Phase II effort will fully develop and fabricate the final design concept from Phase I for demonstration in a government-furnished wind-tunnel environment. PHASE III: Development of large-scale wind tunnels for military high Mach number aircraft, propulsion systems, and weapons. REFERENCES: 1. W900KK-08-R-0017 Amendment 4 Broad Agency Announcement - Advanced Instrumentation Systems Technology Science & Technology (AIST S & T). 2. Thomas, Scott R.; Lee, Jinho; Stephens, John W.; Hostler, Robert W.; and Von Kamp, William D.: The Mothball, Sustainment, and Proposed Reactivation of the Hypersonic Tunnel Facility (HTF) at NASA Glenn Research Center Plum Brook Station. AIAA-2010-4533. 3. Reardon, J. and Warmbrod, J.: Design of a Radiant Heater for AEDC Tunnel C. AEDC-TR-89-1, Feb. 1989. 4. Micol, J.R.: Langley Aerothermodynamics Facilities Complex: Enhancements and Testing Capabilities. AIAA 98-0147. 5. Steinle, FW; Tatum, KC; and Groff, RD: Feasibility of Mach 6 Clean Air Continuous-Flow Heater Using SiC Elements."AIAA 2009-7360.
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