CERAMIC MATRIX COMPOSITES FOR MAGNETOHYDRODYNAMIC AIR PREHEATERS

THIN-WALL CERAMIC COMPOSITE HEAT TRANSFER MATERIALS WITH SUITABLE CORROSION RESISTANCE IN POTASSIUM SEED-LADEN COAL COMBUSTION PRODUCTS ARE POTENTIALLY THE MOST EFFECTIVE METHOD TO PREHEAT THE COMBUSTION AIR DELIVERED TO A MAGNETOHYDRODYNAMIC (MHD) COMBUSTOR. THREE CRITICAL ISSUES CONFRONT CERAMIC MATRIX COMPOSITES (CMCS) IN THIS APPLICATION: SUITABLE HIGH TEMPERATURE, LONG-LIFE CERAMIC FIBERS; OXIDATIVELY STABLE FIBER INTERFACES; AND CERAMIC MATRICES THAT ARE COMPATIBLE WITH THE COAL COMBUSTION PRODUCTS-POTASSIUM SEED (WHICH HAS BEEN DEMONSTRATED TO SEVERELY DAMAGE NONOXIDE MATRICES SUCH AS SILICON CARBIDE AND SILICON NITRIDE). PHASE I IS MAKING USE OF HPZ (A COMMERCIALLY AVAIABLE DOW CORNING PRODUCT) FIBERS WITH AN OXIDE/NONOXIDE INTERFACE SYSTEM AND OXIDE MATRICES PRODUCED BY AN OXIDATIVE PYROLYSIS PROCESS AS WELL AS A PRECERAMIC POLYMER-BASED MATRIX MATERIAL BASED ON ALKYL AND ALKOXIDE CHEMISTRIES. TESTS AND EVALUATION OF THESE MHD PREHEATER CMCS ARE BEING PERFORMED IN AN MHD TEST RIG AT THE UNIVERSITY OF TENNESSEE SPACE INSTITUTE.