Reaction of Aluminum in Gas Phase Near Burning Surface of AP Composite Propellants

Abstract

To design a rocket motor, thrust and burning rate of propellant are important factors. The combustion efficiency of a rocket motor is determined by combustion of aluminum (Al). It is needed to ignite aluminum particles near the burning surface of propellant. The temperature in the reaction zone increases with increasing the distance from burning surface and reaches high temperature about 2000K, therefore it is possible to ignite aluminum particles near the burning surface in the reaction zone. The reaction zone length at burning surface of propellant is less than 1mm at 0.1MPa. It is difficult to observe the reaction zone with a video camera and to evaluate the gas reaction. We measured temperature histories in this reaction zone with a small thermo-couple. The temperature fluctuation occurred near the burning surface. The temperature fluctuation appeared by combustion of solid particles like Al. Heat of reaction in the gas phase is proportional to the partial derivative of the second order with respect to the distance (heat flow) at steady state. Aluminum ignited in the reaction zone, and burned in the luminous flame zone. Hydrogen and carbon reacted easily in the reaction zone, and generated hydrogen oxide and carbon dioxide. In the luminous flame zone there are no oxygen, but only H2O and CO2, aluminum burned in high temperature gases of carbon dioxide and hydrogen oxide. Aluminum for propellant is used small particles, because they first melt and vaporize and mix with the surrounding gas. They need a time to combust completely. The combustion efficiency of Al increases with increasing pressure in a rocket motor, and also increases with increasing stay time in the motor.