Determination of plateau burning effect of catalyzed double-base propellant

Abstract

Combustion wave structures of noncatalyzed and catalyzed double-base propellants were studied to clearly identify and explain the plateau burning mechanism with photographic observations and temperature profile measurements. The propellants used in this study were specially formulated to obtain a wide range plateau burning region that would occur at the lowest possible pressure and burning rate. The reaction processes in the dark zone were unchanged by the addition of the catalyst. While the burning rate remained constant in the plateau region, the luminous flame of the catalyzed propellant approached the burning surface more rapidly than the luminous flame of the noncatalyzed propellant, when the pressure was increased. The temperature gradient in the fizz zone was significantly different for the noncatalyzed and catalyzed propellants. The temperature gradient in the fizz zone of the noncatalyzed propellant increased monotonously with pressure, whenreas the temperature gradient in the fizz zone of the catalyzed propellant increased in the super-rate region and was constant in the plateau region. It was found that the change of the temperature gradient in the fizz zone with pressure is similar to the change of the burning rate with pressure for each propellant. The temperature gradient in the fizz zone of the catalyzed propellant remains unchanged in the plateau region, which indicates that the reaction rate is constant. Therefore, the conductive heat feedback from the fizz zone to the burning surface remains unchanged throughout the plateau pressure region. However, no special trends, in the burning surface temperature and the heat release in the subsurface reaction zone were observed in the plateau burning region, when compared with the normal burning of the noncatalyzed propellant. Thus, the pressure insensitive reaction in the fizz zone is considered to be directly responsible for plateau burning.