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Magnesium/polytetrafluoroethylene/Viton (MTV) fuel-rich pyrolants use the atmospheric oxygen as a complementary oxidizer to sustain and alter the performance of the combustion reaction. The flame diffusion characteristics of MTV fuel-rich pyrolants in the atmospheric environment are studied by a high-speed camera (HSC). The flame temperature and combustion components are measured by using remote sensing Fourier Transform Infrared Spectrometer (FTIR). In order to obtain the combustion component distribution more accurately, an aerobic combustion model containing the oxidation reaction of the excess reactant Mg and carbonaceous species with O2 is established in this study. Eddy dissipation concept (EDC) model is applied to the numerical simulation of the three dimensional anaerobic and aerobic combustion field coupled with Realizable k-ε two-equation turbulence model. The research results show that flame temperature is mainly contributed by anaerobic combustion reaction. The flame structure obtained by the aerobic combustion model is closer to the experimental results, and the result of component distribution calculated by aerobic combustion is more consistent with characteristic spectrum. Therefore, the aerobic combustion model is more suitable for describing the actual MTV flame, and the combustion field can be divided into an anaerobic core zone and an aerobic diffusion zone. [ABSTRACT FROM AUTHOR]

• Eutectic silicon makes the combustion of Al-Si/CuO more stable than Al/CuO. • The increased solid phase products of Al-Si/CuO guarantees good ignition ability. • The eutectic silicon leads to an advanced and enhanced heat release of Al-Si alloy. • Al-Si/CuO thermites ignite Mg/Teflon/Viton (MTV) column faster than Al/CuO. The unstable energy release efficiency hinders the application of Al/CuO metastable intermixed composites (MICs) in pyrotechnic applications to some extent. To overcome this issue, systematic experiments of Aluminum-Silicon (Al-Si) alloy-thermites with different Si content (12 wt% and 20 wt%) have been investigated in the context of regulating the energy release process. Optical diagnosis methods were applied synchronously to measure the flame propagation velocity and temperature field variation. Scanning electron microscopy and differential scanning calorimetry were used to observe the morphology and analyze the thermal process. Results indicated that the introduction of silicon significantly stabilized the combustion process of Al-Si/CuO due to the fewer gas-phase products and slower reaction rate of Si with CuO, while the flame temperature changed little. Excess silicon wafer blocks observed by SEM on Al-20Si led to an enhanced transport of oxygen and fuel. This explained the abnormal reactivity of hypereutectic alloy. The total heat releases of Al-20Si and Al-12Si were respectively enhanced by 110.2% and 93.1% in comparison with that of Al under DSC tests. Infrared temperature measurement of the Mg/Teflon/Viton (MTV) column revealed that Al-12Si and Al-20Si alloy thermites ignited MTV column 569.06 and 540.48 ms faster than Al/CuO, respectively, as the energy output mainly existed in the form of high-temperature residues. These improvements are attributed to the synergistic effect of the reactivity of silicon and aluminum, as well as the phase change during reaction which provides a controllable energy release process of alloy thermite and a better ignition performance. These findings are expected to facilitate the development of the nature of Al alloys and are especially promising for the thermite technology driven by reliable energy release rates. [ABSTRACT FROM AUTHOR]

• Designed a small-scale negative pressure combustion experiment system. • Revealed the effect of pressure on flame structure and temperature. • Demonstrated the pressure sensitivity of the burning rate under 0.02–0.1 MPa. • Predicted the combustion products distribution characteristics. The present study is devoted to comprehensively evaluating the combustion performance of Mg-based (Magnesium/polytetrafluoroethylene/Viton) solid fuels in high-altitude operating environments. A small-scale sealed CO 2 laser ignition experiment system is designed to produce different negative pressure environments. A high-speed camera (HSC) and an infrared thermal imager are used to cooperatively capture the burning process. The results obtained demonstrate that the area of the flame core zone and the flame temperature increase significantly as the pressure increases. It is conducive to the heat feedback of the gas phase reaction zone to the solid phase heating zone, resulting in an increase in the burning rate. As the Mg content increases, the flame temperature is decreased and the burning rate is increased. The burning rate for the Mg-based solid fuels is found to increase monotonically with ambient pressure and to follow the Vieille's law in the pressure range of 0.02–0.1 MPa. Based on the experiment, a three-dimensional combustion-flow coupling solution model is established including the detailed aerobic combustion reaction kinetic model and the eddy dissipation concept (EDC) model. Numerical simulation results reveal that the content of incompletely reacted Mg increases as the pressure decreases. Conversely, the decreasing behavior of oxygen partial pressure at low pressure reduces the probability of reaction of Mg with O 2 , resulting in a dramatical decrease in the mass fraction of MgO. The scientific findings provide useful insight for the deep understanding of the combustion behavior of Mg-based solid fuels, and support for the increasing demands for both military and civilian applications. [ABSTRACT FROM AUTHOR]