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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]

DSC experiments were conducted on the 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-tetracyclo-[5.5.0.05,9.03,11]-dodecane (also known as HNIW or CL-20) and CL-20 containing 10 wt.% microsized aluminum (Al) powders. The kinetic parameters of CL-20 and CL-20/Al were obtained by ASTM685 and Friedman methods, respectively, indicating that Al powder decreases the activation energy of CL-20 slightly and has a catalytic effect on the thermal decomposition of CL-20. By the method of nonlinear multivariate regression, kinetic models of CL-20 and CL-20/Al were derived as fα=1−αn1+kcat⋅α, where the lgkcat of CL-20 and CL-20/Al is 1.97 and 2.12, respectively, showing that the autocatalytic ability of CL-20 had been increased by adding Al powder. From the SEM images of CL-20/Al and the XRD pattern of the decomposition residues of CL-20/Al, it can be inferred that partial combustion of Al particles happened in the microscale view and led to the release of heat. [ABSTRACT FROM AUTHOR]

As a kind of high explosives, aluminized explosive cannot release the energy maximumly, which is a key problem. Using DTA-TG equipment, the ignition performance of three kinds of aluminized explosives (RDX, HMX, and CL-20) with different mass percentages of aluminum powder (0%, 10 wt.%, 20 wt.%, and 30 wt.%) was investigated. The results showed that the energy release of the HMX/Al composite explosive with 10 wt.%, 20 wt.%, and 30 wt.% aluminum powder was only equivalent to 80%, 65%, and 36% of pure HMX, respectively. It was similar to RDX/Al and CL-20/Al composite explosives, except the CL-20/Al mixture with 10% aluminum powder. Rather than participating in the ignition and combustion, the aluminum powder does effect the complete reaction of RDX, HMX, and CL-20 in the initial stage of ignition or in the lower temperature area of the boundary. [ABSTRACT FROM AUTHOR]

• Designed a combustion experiment platform that can mimic high-altitude environment. • Revealed the effect of Mg-burning particles on combustion and infrared signatures. • Gas-solid two-phase coupling effects are treated in combustion simulation. • Developed an in-house code to solve the non-isotropic radiative transfer equation. The combustion process of Mg/PTFE/Viton-based pyrotechnics exhibits a complex multiphase flow phenomenon. However, the influence mechanism of metal particles undergoing dynamic diffusion combustion in the flow field on the infrared radiation output characteristics has not yet been elucidated. Systematic experiments and numerical simulations are performed with the combustion and infrared radiation behaviors of the pyrotechnic compositions. A small-scale sealed combustion experiment platform is specially manufactured to mimic the actual ambient pressure at different cruise altitudes. An infrared thermal imager and an infrared thermometer are adopted cooperatively to diagnose the burning process. The Euler-Langrangian method is applied to mathematically describe the gas–solid two-phase interaction in the combustion flow field, and the Eddy Dissipation Concept (EDC) combustion model is employed to simulate the coupling effect of turbulence and chemical reaction in the gas-phase reaction zone. The verified Source Six-Flux (SSF) method based in-house code solves the infrared radiative transfer equation integrating the emission, absorption and scattering effects of participating media. The comparisons with the experimental results demonstrate that the computational model involving heterogeneous reactions established in this paper better approximates the realistic situation. The results reveal that the infrared radiation output capability of dispersed combustion particles in the 2.0–5.5 μm band surpasses that of high-temperature gas molecules under different environmental pressures. The infrared radiation magnitude of both the gaseous phase and the particulate phase decrease significantly with decreasing pressure. The thermal radiation of combustion particles is mainly concentrated in the near- to mid-infrared band, while its emission in the far-infrared band is relatively weak. These scientific findings provide conducive insights for lucubrating the infrared radiation mechanism of pyrotechnics under negative pressure environments, and assist in further promoting the application of MTV pyrotechnics in the field of aerospace. [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]

Abstract: The thermal properties and combustion characteristics of KClO4/Mg–50%Al, KClO4/Mg–50%Al with additives such as nitrocellulose (NC), urotropine and guanidine nitrate (GN) were studied experimentally using differential thermal analysis (DTA) and thermogravimetry (TG) and closed bomb experiments. The results of DTA–TG analysis revealed that additives could affect thermal stability and the decomposition temperature of KClO4/Mg–50%Al alloy. The order of the ignition temperatures of mixtures (T i) is KP/Mg–50%Al/urotropine (2#, 557.7°C)>KP/Mg–50%Al/GN(3#, 553.6°C)>KP/Mg–50%Al (1#, 538.8°C)>KP/Mg–50%Al/NC (4#, 536.5°C). On the other hand, the results of the closed bomb experiments confirm that the combustion pressures were all increased with the addition of additives. The ignition delay times of these mixtures are in the order KClO4/Mg–50%Al (1#)>KClO4/Mg–50%Al/GN (3#)>KClO4/Mg50%Al/NC (4#)>KClO4/Mg–50%Al/urotropine (2#). [ABSTRACT FROM AUTHOR]