Erosive burning mechanism of double-base propellants

Abstract

Measurements of the combustion wave structure of solid propellants with and without cross-flow conditions were conducted to elucidate the mechanism of erosive burning. The propellants tested were three types of double-base propellants containing different energy levels: a lowenergy, a reference, and a high-energy propellant. The test results indicate that the erosive burning ratio decreases with increasing energy contained in the unit mass of propellant. The threshold velocity is lower for the low-energy propellant than for the high-energy propellant. Measurements with microphotographs and microthermocouples revealed that the dark zone which separates the luminous flame and the burning surface diminishes completely under cross-flow conditions. The heat flux transferred back from the fizz zone to the burning surface increases when the cross-flow velocity exceeds the threshold velocity. Erosive burning occurs when the fizz zone parameter Φ is increased by the turbulent mixing generated by the cross-flow. The analysis presented in this study indicates that the fizz zone parameter is correlated uniquely with the friction force τ, at the surface as Φ∼τ 0.8 .