Study on the combustion behavior of metalized double-base propellants(III): Heat effects of the metals on the burning rate and flame temperature

摘要

The combustion properties of double-base propellants containing reactive metals such as aluminum (Al), magnesium (Mg), boron (B), nickel (Ni) and Mg-Al mechanical alloy (Mg/Al=3/4) are investigated by means of burning rate test, high-speed photography technique, Non-contact Wavelet-based Measurement of flame temperature distribution, Scanning Electron Microscope (SEM) and Differential Scanning Calorimetry (DSC). The research investigates how the heat effect of the metals in condensed phase and gas phase controls the burning characteristics of double-base propellants containing such reactive metals. It was indicated that the heat effect of the metals by conduction in solid phase, by change of phase consisting of both evaporation and condensation in the interphase and by radiation in gas phase are considered to provide a complete description of the heat transfer process in the combustion of metalized double-base propellants, and the combustion process of them are mainly involved with the oxidation of the metals and thermolysis of NC/NG and RDX. In combustion of aluminum, magnesium, and Mg/Al in solid propellant, there are gas phase reactions and also surface oxidation resulting in volatile and non volatile products which include oxide and suboxide species. However, there are only gas phase reactions for boron and transition metal nickel due to the higher melting point and enthalpy of vaporization. A mathematical model of heat transfer by radiation for the propellants containing reactive metals has been theoretically and experimentally established and analyzed. It was concluded that the B-MDB and Al-MDB propellants are of the higher theoretical radiation heat which in practice are converse due to their agglomeration and incomplete combustion.