Experimental and theoretically study on the combustion wave and flame propagation of metalized double-base propellants

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 high-speed photography technique, Noncontact Wavelet-based Measurement of flame temperature distribution, Scanning Electron Microscope (SEM) and Differential Scanning Calorimetry (DSC). The heat effect of metals in the condensed phase which might control the burning characteristics of the double-base propellant was systematically investigated and descriptions of the detailed combustion physical model of the metals from solid phase to liquid phase or to gas phase are also included. Moreover, the mathematical model of spray-like combustion for some reactive metals contained propellants were theoretically established and analyzed. It was indicated that the thermodynamic phase transition consisting of both evaporation and condensation of NC/NG binder, RDX, Al, Mg, B, Ni and Mg/Al, are considered to provide a complete description of the mass transfer process in the combustion of this kind of double-base propellants, and the combustion process of them were mainly involved with the oxidation of the metals and thermolysis of NC/NG binder 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. At last, a numerical calculation method for analyzing combustion wave structure of metallized propellants has been designed and the fitting functions for the temperature profiles were obtained by Origin 7.5 software. The detailed information of the combustion waves in the flame zone together with the condensed phase was obtained by using this method. It is believed that in gas phase there would be multi-stage reaction mechanism and that the reaction mechanism would be identical in condensed phase for different metallized propellants, only the heat release value was different.