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Conventional ignition methods are proving to be ineffective for low-sensitivity energetic materials, highlighting the need to investigate alternative ignition systems, such as laser-based techniques. Over the past decade, lasers have emerged as a promising solution, providing focused energy beams for controllable, efficient, and reliable ignition in the field of energetic materials. This study presents a comparative analysis of two state-of-the-art ignition approaches: direct laser ignition and laser-driven flyer ignition. Experiments were performed using a Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser at different energy beam levels to systematically evaluate ignition onset. In the direct laser ignition test setup, the laser beam was applied directly to the energetic tested material, while laser-driven flyer ignition utilized 40 and 100 μm aluminum foils, propelled at velocities ranging from 300 to 1250 m/s. Comparative analysis with the Lawrence and Trott model substantiated the velocity data and provided insight into the ignition mechanisms. Experimental results indicate that the ignition time for the laser-driven flyer method was significantly shorter, with the pyrotechnic composition achieving complete combustion faster compared to direct laser ignition. Moreover, precise ignition thresholds were determined for both methods, providing critical parameters for optimizing ignition systems in energetic materials. This work elucidates the advantages and limitations of each technique while advancing next-generation ignition technology, enhancing the reliability and safety of propulsion systems.

Based on the characteristics of laser-induced surface ignition, energetic photosensitive films show promising potential to meet the ignition requirements of various energetic materials (EMs). In this study, DATNBI/ferric alginate (DI/FeA), DI/cobalt alginate (DI/CoA), and DI/nickel alginate (DI/NiA) films are fabricated by employing sodium alginate (SA) with a three-dimensional network structure as the film matrix, via ionic cross-linking of SA with Fe3+, Co2+, and Ni2+ ions. The study demonstrates that the ionic cross-linking enhances the hydrophobic performance of the films, with the water contact angle increasing from 82.1° to 123.5°. Concurrently, the films' near-infrared (NIR) light absorption improved. Furthermore, transition metal ions facilitate accelerated electron transfer, thereby catalyzing the thermal decomposition of DATNBI. Under 1064 nm laser irradiation, the DI/FeA film exhibits exceptional combustion performance, with an ignition delay time as low as 76 ms. It successfully acts as an NIR laser ignition medium to initiate the self-sustained combustion of CL-20. This study demonstrates the synergistic realization of enhanced hydrophobicity, improved photosensitivity, and promoted catalytic decomposition through microstructural design of the material, providing new insights for the design of additive-free EMs in laser ignition applications. •The polymer sodium alginate as a matrix enhances the structural stability of the film.•Transition metal ion loaded DATNBI films enhance hydrophobicity.•In-situ generated metal oxides accelerate the decomposition and combustion of DATNBI.•Near-infrared laser-ignitable DATNBI films exhibit stable and reliable output energy.

Nano aluminum (Al) has always been the research hotspot in the field of energetic materials because of its high energy density and combustion temperature, and has been considered to be a promising fuel to enhance the energy release of various propulsive systems. In this work, nanocomposite fibers were fabricated by electrospinning technology, in which nano Al and recrystallized cyclotrimethylene trinitramine (RDX) particle were integrated with nitrocellulose (NC) fibers. The agglomeration of nano Al particles in fibers is significantly inhibited. The morphology and chemical components of NC/Al, NC/RDX, and NC/Al/RDX composite fibers were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). The thermal analysis shows that nano NC fibers have lower thermal decomposition temperature (202.1 °C) and apparent activation energy (149.3 kJ mol−1) than raw NC (208.2 °C and 218.5 kJ mol−1), and NC/Al/RDX exhibits improved thermal decomposition properties compared with NC/RDX and NC/Al. The laser ignition experiments suggest that the uniformly dispersed nano Al particles could obviously promote the combustion and shorten ignition delay time. RDX may delay ignition due to its high decomposition temperature, but can significantly enhance the combustion properties of NC/Al/RDX fibers. The combustion propagation velocity of composite fibers is obvious higher than that of its physical mixture. The condensed combustion product is mainly spherical aluminum oxide (Al2O3) with a median diameter of about 180 nm. The reason can be attributed to the intimacy between fuel and oxidizer in composite fibers, which enhances heat and mass transfer.Graphic abstractAluminum with high enthalpy and high combustion temperature is an essential ingredient for improving combustion performance of propellants. In this work, NC based composite fibers containing nano Al were fabricated by electrospinning, which significantly improved laser ignition and combustion performance. The electrospinning technique would also be extended to other composite preparation for broader application beyond the energy materials.

In this study, effects of number of consecutive laser ignition pulses on combustion and particle emission characteristics of CH 4 /Air mixtures were investigated in a rapid compression machine (RCM) by using a passively Q-switched Nd:YAG laser ignitor. To that end, ignition kernel formation and flame evolution characteristics were analyzed with the instrumentality of a high-speed camera (Schlieren setup), while combustion and emission properties were examined by measuring pressure and particulate emissions, respectively. The variation of pressure was also recorded to calculate (with a MATLAB code) indicated work, indicated mean effective pressure and efficiency. Results of this study revealed the linear dependence of ignition possibility to the number of pulses. Ignition possibility increased with the increasing number of pulses. It was 72.72% at 1 pulse and became 92.10% at three pulses. However, number of pulses differently affected other measured or calculated parameters. Depending on the number of pulses, improvements and deteriorations were observed in performance metrics.

Powder ramjets are a kind of vehicle propulsion system with high specific impulse and efficiency. They provide significant benefits in terms of extended propulsion and thrust adjustment. The pursuit of a highly reactive fuel appropriate for powder ramjets is likely to stimulate advancements in innovative propulsion systems, which are crucial for deep space exploration and long-term space missions. This work presents experimental studies on the thermal oxidation and laser ignition performance of aluminum–magnesium–lithium powders at atmospheric pressure. TG-DSC curves of powders in three heating rates were obtained. The ignition processes and ignition delay times were recorded by a CO2 laser ignition experiment system at a laser power of 10~60 W. The results show that at a lower heating rate of 10 K/min, the powder’s thermal hysteresis is less, and the powder energy released in stage I is more concentrated. However, the degree of heat release concentration approached a similar level at heating rates of 30 K and 50 K. The ignition delay time decreased as the laser flux density increased. When the laser flux density exceeds 80 W/cm2, the effect of laser power on the ignition delay time decreases. At atmospheric pressure, the mathematical relationship between ignition delay time and laser flux density is given. Finally, the powder ignition processes at different laser powers are represented graphically.

Methanol has garnered attention as a promising alternative fuel for marine engines due to its high octane number and superior knock resistance. However, methanol-fueled engines face cold-start challenges under low-temperature conditions. Laser ignition technology, an emerging ignition approach, shows potential to replace conventional spark ignition systems. This study investigates the effects of laser ignition on combustion and emission characteristics of direct-injection methanol engines based on methanol fuel combustion mechanisms using the AVL-Fire simulation platform, focusing on optimizing key parameters, including ignition energy, longitudinal depth, and lateral position, to provide theoretical support for efficient and clean combustion in marine medium-speed methanol engines. Key findings include an ignition energy threshold (60 mJ) for methanol combustion stability, with combustion parameters (peak pressure, heat release rate) stabilizing when energy reaches ≥80 mJ, recommending 80 mJ as the optimal energy level (balancing ignition reliability and energy consumption economy). Laser longitudinal depth significantly influences flame propagation characteristics, showing a 23% increase in flame propagation speed at 15 mm depth and a reduction of unburned methanol mass fraction to 0.8% at the end of combustion.

To solve the problems associated with micron-sized aluminum (Al), including sintering, agglomeration, and slag deposition during the combustion of aluminized propellants, aluminum–lithium (Al-Li) alloy, prepared by introducing a small amount of Li (1.0 wt.%) into Al, was used in place of Al. Then, the ignition and combustion characteristics of single micron-sized Al-Li alloy particles were investigated in detail using a self-built experimental apparatus and multiple characterization methods. The ignition probability, ignition delay time, flame propagation rate, burn time, combustion temperature, flame radiation spectra, and microexplosion characteristics were obtained. The TG-DSC results demonstrated that, as compared to the counterpart Al, the Al-Li alloy had a lower ignition temperature. The emission lines of AlO revealed the gas-phase combustion of the Al-Li alloy, and thus the Al-Li alloy exhibited a mixed combustion mode, including surface combustion and gas-phase combustion. Moreover, during combustion, a microexplosion occurred, which increased the combustion rate and reduced the burn lifetime. The ambient pressure had a significant effect on the ignition and combustion characteristics of the Al-Li alloy, and the ignition delay time and burn time exponentially decreased as the ambient pressure enhanced. The combustion temperature of the Al-Li alloy at atmospheric pressure was slightly higher than those at elevated pressures. The Al-Li alloy burned in N2, but no microexplosion was observed. Finally, the ignition and combustion mechanism of the Al-Li alloy in air was demonstrated by combining SEM, EDS, and XRD analyses of the material and residues. The results suggest that the addition of Li promoted the combustion performance of Al by changing the surface structure of the oxide film and the combustion mode.

In many countries, motorcycles have become a primary and popular mode of transportation, driven by increasing demand due to their convenience. However, as fossil fuel sources deplete, there's a pressing need to enhance engine performance, efficiency, fuel economy, and reduce emissions. Improving ignition systems is crucial in achieving these goals. This study compares the performance of the Honda Future FI 125cc engine between a laser ignition system (LIS) and a conventional ignition system (CIS) using simulation. CATIA software was utilized to design the engine's intake manifold, ANSYS Fluent software for simulating and determining the optimal swirl and tumble ratio, and Matlab/Simulink for modeling and simulating engine performance with both LIS and CIS. Detailed discussions and comparisons were made on parameters such as cylinder air mass, ignition energy, engine power and torque, specific fuel consumption (SFC), and mass fraction burned (MFB) between LIS and CIS. Overall, LIS demonstrated superior engine performance compared to CIS. This finding is significant for evaluating the advantages of LIS in motorcycles, especially in the Honda Future FI 125cc engine.

To enhance the catalytic activity of copper ferrite (CuFe2O4) nanoparticle and promote its application as combustion catalyst, a low-cost silicon dioxide (SiO2) carrier was employed to construct a novel CuFe2O4/SiO2 binary composites via solvothermal method. The phase structure, morphology and catalytic activity of CuFe2O4/SiO2 composites were studied firstly, and thermal decomposition, combustion and safety performance of ammonium perchlorate (AP) and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) with it affecting were then systematically analyzed. The results show that CuFe2O4/SiO2 composite can remarkably either advance the decomposition peak temperature of AP and RDX, or reduce the apparent activation energy at their main decomposition zone. Moreover, the flame propagation rate of RDX was promoted by about 2.73 times with SiO2 content of 3 wt%, and safety property of energetic component was also improved greatly, in which depressing the electrostatic discharge sensitivity of pure RDX by about 1.89 times. In addition, the effective range of SiO2 carrier content in the binary catalyst is found to be 3 to 5 wt%. Therefore, SiO2 opens a new insight on the design of combustion catalyst carrier and will promote the application of CuFe2O4 catalyst in solid propellant.

As a method of initiating detonation in a short distance with a small amount of energy, the combination of laser ignition and shock focusing in an elliptical cavity was proposed and experimentally demonstrated with a C 2 H 4 - O 2 mixture at 100 kPa and 297 K. In the experiment, an elliptical cavity and single rectangular cavities of different heights were used, and their flow-field patterns were visualized using high-speed schlieren imaging. Detonation initiation was achieved in the case of the elliptical cavity, and based on the Mach number change of the leading shock wave, two propagation phases were verified: the deceleration and acceleration phases. The deceleration phase was driven merely by the gasdynamic effect, wherein the initial shock wave (ISW) expanded spherically, and the acceleration phase began when the ISW shifted to planar propagation. In the acceleration phase, although gradual acceleration was observed in rectangular cavities, rapid acceleration occurred in the elliptical cavity. From the schlieren images, the second acceleration was caused not only by the concave reflected shock wave’s catching up with the ISW, but also by the fast-flames that were generated along the cavity corners and engulfed the ISW in the converging section of the elliptical cavity.