A study of Thermal Decomposition and Kinetic Evaluation of Boron blended Flash Powder Composition

Herein, the thermal characteristics of flash powders of different combinations of Potassium Nitrate, Sulphur, Aluminium and Boron are reported. From the literature, it is identified that Boron implements lack of sensitiveness to flash powder mixture, which promotes the safety during the manufacturing process. But the thermal behaviour of the Boron blended compositions remain a mystery. Hence, various combinations of flash powder compositions are prepared by keeping the % of KNO3 and % of S as constant, and gradually 23% of Aluminium is reduced (23% to 0) by increasing the quantity of Boron (0 to 23%) in 19 trials, and are subjected to TGA/DSC analysis individually. The TGA and the DSC analysis reveals that the 65.65% replacement of Aluminium with Boron mixture shows predominant characteristics which is suitable for fireworks. Also, the reaction kinetics and the critical ignition temperature are calculated for the optimum composition. The performance of the fireworks product is checked with varying quantity to meet out the optimum quality.

Effect of boron on HEM radiant ignition characteristics

The paper presents the ignition characteristics of high-energy materials (HEMs) containing ammonium perchlorate, butadiene rubber, and a mixture of Al/B nanopowders with different component ratios. Bimetallic systems based on aluminum with boron increase the reactivity and intensify the ignition of boron particles, which helps to decrease the critical ignition conditions of HEMs during heating. It is shown that the use of systems based on aluminum-boron reduces the delay time (by 17–52 %) and the ignition temperature of propellants in comparison with a HEM containing aluminum powder, and increases the activation energy of HEM during radiant heating.

Study on the Risk Assessment of Spontaneous Ignition and of Perilla Oil Cakes Associated Activation Energy

Perilla oil cakes are the residues of oil pressing processes, and used as fertilizers, feedstuff, food, etc. However, according to recent reports, perilla oil cakes often ignite spontaneously due to scorching heat, particularly in rice mills, general mills, and oil mills where large amounts of perilla oil cakes are stored. Thus, in this study, we attempted to elucidate the risk of spontaneous ignition of perilla oil cakes. For this purpose, thermogravimetry/differential thermal analysis (TG-DTA) was performed to identify thermal properties like weight reduction and heat generation, and spontaneous ignition was conducted for sample vessels of different thicknesses. The results showed that the ignition temperature of perilla oil cakes was 115 ℃ for the small (20 cm × 20 cm × 3 cm) vessel. The apparent activation energy associated with the critical ignition temperature was 60.74 kJ/mol. The ignition delay time and the time to reach maximum temperature were both found to increase with increasing vessel thickness. It was concluded that proper protection against heat must be in place because fire risk increases and spontaneous ignition can occur when large amounts of perilla oil cakes are accumulated.

The Critical Temperature of N-Nitro-Dihydroxyethylami Nitration Reaction

The nitration reaction is one kind of important reaction in many synthetic chemical reactions. The reaction with a high temperature releases a lot of heat and is easy to get out of control. The energetic materials is the main ingredients of the reaction mixture in late of nitrification of energy-containing materials, the accident about burn or rapid energy release will happen once the reaction is out of hand. There are so many thermal safety studies of energy materials, but the thermal safety research about energy material nitrification production line is not reported. Using the designed multi-scale energy material test, the thermal stability of DINA (N-Nitro-dihydroxyethylami) nitration reaction mixture was studied. The critical ignition temperature about different scale was obtained, and this temperature can be used as the base of enterprise process safety design.

Critical Ignition Conditions of Wood by Cylindrical Firebrands

This study investigated the thermal conditions preceding ignition of three dense woody fuels often found on structures by firebrands, a major cause of home ignition during wildland-urban interface (WUI) fires. Piles of smoldering cylindrical firebrands, fabricated from wooden dowels, were deposited either on a flat inert surface instrumented with temperature and heat flux sensors or on a target fuel (marine-grade plywood, oriented-strand board, or cedar shingles) to investigate critical conditions at ignition. The former provided thermal data to characterize the time before and at ignition, while the latter provided smoldering and flaming ignition times. Tests were conducted in a small-scale wind tunnel. Larger firebrand piles produced higher temperatures at the center of the pile, thought to be due to re-radiation within the pile. Ignition was found to be dependent on target fuel density; flaming ignition was additionally found to be dependent on wind speed. Higher wind speeds increased the rate of oxidation and led to higher temperatures and heat fluxes measured on the test surface. The heat flux at ignition was determined by combining results of inert and ignition tests, showing that ignition occurred while transient heating from the firebrand pile was increasing. Ultimately, critical ignition conditions from firebrand pile exposure are needed to design appropriate fire safety standards and WUI fire modeling.

Optimal Design Method for Inner-Intrinsically Safe Buck-Boost Converters Based on Ignition Capability

Intrinsically safe switching converters are the best choice for low-voltage DC power supplies in explosive environments (such as coal mine). To obtain the optimal design method of the inner-intrinsically safe buck-boost converter (IISBBC), the equivalent circuits for various switching states and operating conditions of the buck-boost converter are studied, and the most dangerous inductor-disconnected discharge (IDD) condition of the buck-boost converter is obtained. Based on this condition, the IDD behavior of the IISBBC is studied. According to the minimum ignition curves (MICs) of the resistive circuit and the simple inductive circuit, the expressions describing the IDD ignition capability of the IISBBC in terms of the critical ignition power and the critical ignition energy are derived. The IDD has the strongest ignition capability based on power when the IISBBC is working at its maximum input voltage and minimum load resistance, and it has the strongest ignition capability based on energy when the IISBBC is working at its minimum input voltage and minimum load resistance. The converter is inner-intrinsically safe only when the maximum arc power is less than the critical ignition power and the inductive energy is less than its critical value. By incorporating the proposed criterion, the optimal design method for IISBBCs that meets the demands of electric and inner-intrinsic safety performance is obtained. Based on this method, the design range of the inductance and capacitance and the optimal inductance to give the IISBBC the best inner-intrinsic safety performance are obtained. The feasibility and reliability of the proposed optimal design method are demonstrated by an explosion test.

Numerical Investigation of Mixing Characteristic for CH4/Air in Rotating Detonation Combustor

The mixing process of fuel and oxidizer is a very critical factor affecting the real operating performance of non-premixed rotating detonation combustor. In this paper, a two-dimensional numerical study is carried out to investigate the flow and mixing characteristics of CH4/air in combustor with different injection structures. On this basis, the effect of CH4/air mixing on the critical ignition energy for forming detonation is theoretically analyzed in detail. The numerical results indicate that injection strategies of CH4 and air can obviously affect the flow filed characteristic, pressure loss, mixing uniformity and local equivalence ratio in combustor, which further affect the critical ignition energy for forming detonation. In the study for three different mass flow rates (the mass flow rates of air are 12.01 kg/s,8.58 kg/s and 1.72 kg/s, respectively), when air is radially injected into combustor (fuel/air are injected perpendicular to each other), although the mixing quality of CH4 and air is improved, the total pressure loss is also increased. In addition, the comparative analysis also shows that the increase of mass flow rate of CH4/air can decrease the difference of the critical ignition energy for forming detonation at a constant total equivalence ratio. The ignition energy decreases with the decrease of the total flow rate and then increases gradually.

Combustion Microstructures and Frictional Ignition Resistance of Ti-6Al-4V Titanium Alloy

The effects of the contact pressure Pfric and the oxygen concentration c0 on the ignition resistance of Ti-6Al-4V were studied by friction in oxygen-enriched atmosphere. The relationship of Pfric-c0 was built to quantitatively describe the ignition resistance, the combustion microstructures were investigated by XRD, SEM and EDS. Further, the principle of improving the ignition resistance was proposed. It indicates that the relationship of Pfric-c0 obeys parabolic law. The c0 decreases by 4% when the Pfric increases from 0.1MPa to 0.25MPa, manifesting that the ignition resistance depends on c0 strongly (or equivalent flow pressure Peq). The ignition resistance of Ti-6Al-4V is 42.9% of that of TB12. When Peq varies from 0.1~0.5MPa, the critical ignition temperature Т* is approximate to 568~461K. Violent sparks form during frictional ignition. The low ignition resistance of Ti-6Al-4V probably results from not only the composite oxides of TiO2, Al2O3 and V2O5 generating during ignition which could not prevent the rapid interaction between Ti and O, but also the Al and V elements in the heat-affected zone which could not stop or slow the massive diffusion of O towards the alloy.