HEAT TRANSFER TO A SOLID-PROPELLANT ROCKET-MOTOR NOZZLE
BATTELLE MEMORIAL INST COLUMBUS OH
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The heat transfer to a small-scale rocket nozzle was studied under the conditions imposed by the combustion of two high-energy solid propellants. The exhaust contains large quantities of aluminum oxide. The heat-transfer problem can be separated into the heat transfer from the hot combustion products to a layer of deposited ALUMINA AND THE HEAT TRANSFER FROM THE ALUMINA LAYER TO THE UNDERLYING SOLID MATERIAL. Temperature histories at several locations in Mb nozzles were measured with high-temperature thermocouples. The heat-transfer rate was computed from the deposited alumina to the nozzles. During some periods of the motor firings, the heat transfer across the alumina layer could be deduced from steady-state relations. The temperature at the exposed alumina surface and the heat-transfer coefficient between the combustion products and the alumina was determined and agreed with turbulent heat-transfer theory. Although the alumina deposit layer insulates the nozzle structure and in so doing strongly influences the temperature history, transfer is negligible. Nozzle surface-temperature history was computed for various ceramic nozzle materials. Calculations successfully predicted the time in the firing at which melting or thermal degradation occurred.