HIGH TEMPERATURE IGNITION OF COATED BORON PARTICLES IN A SHOCK TUBE

IN ADVANCED PROPELLANT APPLICATIONS, THE IGNITION OF BORON PARTICLES IS INHIBITED BY THE BUILD UP OF A NON-VOLATILE BORON OXIDE LAYER ONTHE OUTER SURFACES. TECHNIQUES ARE CURRENTLY BEING DEVELOPED TO PREPARE BORON PARTICLES COATED WITH HIGH BURNING RATE METALS, IN THE EXPECTATION THAT SUCH COATINGS WILL SIGNIFICANTLY ACCELERATE THE IGNITIONAND BURNING OF THE BORON FUEL AND THUS ENHANCE ITS OVERALL COMBUSTION EFFICIENCY. IN ORDER TO EXAMINE SYSTEMATICALLY THE IGNITION BEHAVIOR OF COATED AND UNCOATED BORON PARTICLES, PHYSICAL SCIENCES INC (PSI)PROPOSES TO MEASURE IGNITION DELAYS AND BURNING RATES OF COATED AND UNCOATED BORON PARTICLES BEHIND REFLECTED SHOCK WAVES IN A SHOCK TUBE. A PREVIOUSLY DEVELOPED, NOVEL RADIAL PARTICLE INJECTOR WILL PROVIDEUNIFORM, DILUTE CLOUDS OF PARTICLES IN AR AND AR/O2 BATHS, WHICH WILL BE RAPIDLY HEATED TO SELECTED COMBUSTION TEMPERATURES (1800 TO 3000K) BY REFLECTED SHOCK WAVES. A VARIETY OF STATE-OF-THE-ART OPTICAL EXTINCTION AND SPECTRAL EMISSION DIAGNOSTICS, AT VISIBLE AND INFRARED WAVELENGTHS, WILL BE USED TO MONITOR THE TIME-RESOLVED KINETIC BEHAVIOR OF PARTICLES AND KEY GAS-PHASE COMBUSTION SPECIES SUCH AS BO AD BO2. THE RESULTS OF THE PHASE I EFFORT WILL BE DETERMINATIONS OF THE COMPARATIVE IGNITION BEHAVIOR FOR A LIMITED SELECTION OF COATED AND UNCOATED BORON PARTICLES, AND DEFINITION OF MORE COMPREHENSIVE PHASE II INVESTIGATIONS OF COATED BORON COMBUSTION PHENOMENA.