No abstract

Regenerative storage heater (RSH) technology is a potential means for supplying clean air as a propulsion test medium for high speed/hypersonic weapon systems and flight vehicles. The current state-of-the-art for reliable, long-life RSH technology uses high-purity, high-density, alumina cored bricks as the heat storage bed. An alumina RSH can supply clean air at stagnation temperatures representative of flight through the earth's atmosphere up to approximately Mach 6.4. Through application of advanced, yttria-stabilized zirconia materials, it will be possible to extend the upper limit of clean air, true temperature propulsion test capability to the Mach 7-8 range. Earlier attempts (in the 1960s and 1970s) to demonstrate zirconia RSH technology had limited success, due primarily to zirconia destabilization, thermal stresses, and consequent damage to the zirconia materials. These problems resulted from limitations of the zirconia materials available at the time as well as storage heater brick designs that did not adequately limit thermal stresses. Subsequent advances in both zirconia materials and storage heater designs led to a renewed effort, initiated in 2006, to develop clean air RSH technology for aeropropulsion test facilities. The research program is evaluating the application of a commercially available yttria-stabilized zirconia (YsZ) material to the design of a high temperature RSH to supply clean air for a propulsion test faculty. The program has included materials evaluation and testing in specially designed test rigs to subject the YsZ materials to conditions representative of a fullscale RSH. A preliminary concept has also been developed for a full-scale RSH system as part of a clean air test leg for the Aerodynamic and Propulsion Test Unit (APTU) facility atAEDC. This test leg would provide clean air at representative stagnation temperatures over a Mach number range of 2-8, with available run times of at least 120 seconds over the full Mach range. The research program results obtained to date are encouraging, though additional materials tests and pilot-scale RSH testing will be required to establish the final maximum operating capability. NomenclatureAPTU = Aerodynamic and Propulsion Test Unit M = Mach number MHD = magnetohydrodynamic RSH = Regenerative Storage Heater T b = cored brick web bulk temperature T s = cored brick hole surface temperature TTT = True Temperature Tunnel YsZ = yttria-stabilized zirconia * Senior