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Initiation of Ignition in Ammunition
Published in Ajoy K. Bose, Military Pyrotechnics, 2021
Laser is an acronym for light amplification by stimulated emission of monochromatic radiation. Laser is used to heat a large number of materials like melting, welding, drilling or igniting materials by sending a high-intensity, coherent beam of radiation. Laser ignition is not a photochemical phenomenon but purely an optical ignition system. Laser ignition of explosive material system can be subdivided into three parts, namelyA laser firing unit (typically laser sources are Ruby, Nd: YAG, CO2, Nd: glass, argon ion, laser diodes, etc.)Fibre optics cable made from a glass or plastic core that carries light surrounded by glass cladding that (due to its lower refractive index) reflects “escaping” light back into the core, resulting in the light being guided along the fibre for transmission of energy and a sealed optic windowAn explosive (pyrotechnic, propellant or high explosive) material to receive laser energy to be ignited
Numerical simulation of combustion characteristics and emission predictions of methane-air and hydrogen-air mixtures in a constant volume combustion chamber using multi-point laser-induced spark ignition
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Prashant Mahadev Patane, Milankumar Ramakant Nandgaonkar
Laser ignition has become an alternative to replace the traditional ignition systems, and it shows many potential benefits, despite few drawbacks still exists (Phuoc 2006). The main advantage of laser-induced ignition is an electrode-less ignition system. Therefore, there is no problem like electrode erosion and quenching effects, and thus life span of the laser ignition system is longer than the spark plug ignition. It has control over ignition timing and ignition locations. The laser ignition allows the easy possibility of multi-point ignition and can ignite liquid or gaseous combustible mixtures at multiple spots either sequentially or simultaneously. It also has precise control of ignition energy deposited in ignition plasma. In laser ignition, the required breakdown energy decreases as gas pressure increases, unlike the traditional electrical discharge system (Phuoc 2006). These advantages of laser ignition show huge potential for practical implementations, and thus in the last few years, the number of studies on laser ignition has been increased.
Comparison on Laser Ignition and Combustion Characteristics of Nano- and Micron-Sized Aluminum
Published in Combustion Science and Technology, 2021
Xiao Jin, Shengji Li, Yihang Yang, Xuefeng Huang
The ignition and combustion performance of solid propellants and thermites containing micro-Al or nano-Al has been widely investigated (Koch and Friedlander 1989). However, the complexity of composites made it difficult to deeply unveil the mechanism of Al combustion and the interaction between Al particles and other components. The combustion mechanism of pure Al particles is of great significance for understanding the interaction. Therefore, the objective of this study is to compare the ignition and combustion characteristic of pure nano-Al and micro-Al. Six sizes of Al samples were used, in average diameters of 56.0 nm, 74.4 nm, 93.4 nm for nano-Al and 2.9 μm, 6.1 μm, 10.8 μm for micro-Al, respectively. The ignition and combustion experiments were conducted in self built laser ignition setup. The burning processes were recorded by high-speed camera and infrared thermal imaging camera. The differences of characteristic ignition delay time, temperature evolution, and combustion residues between nano-Al and micro-Al were analyzed and discussed. Finally, a general model was built to explain physicochemical behaviors during the ignition and combustion of nano-Al and micro-Al.
Effect of low initial pressures on ignition properties of lean and rich n-decane/air mixtures for laser-induced breakdown
Published in Combustion Science and Technology, 2019
Steve Rudz, Pietro Tadini, Fanny Berthet, Philippe Gillard
During the last 20 years, the interest on laser ignition for applications in aerospace propulsion has significantly grown, due to several advantages demonstrated by conventional electrical spark igniters (O’Briant et al., 2016). Beside the possibility to control the input energy precisely, a laser-induced spark ignition provides a more stable combustion, characterized by lower fuel consumption and a decrease in pollution products emission (Weinrotter et al., 2005a). Furthermore, lean fuel mixtures can be easily ignited, as well as ignition of high and low pressure mixtures, and multi-point laser sparks reduce the ignition delay time (O’Briant et al., 2016; Pal and Agarwal, 2015; Weinrotter et al., 2005b). In practice, these features promise the achievement of higher performance for the commonly employed aviation engines, spanning from internal combustion to turbofan motors. In particular, the former takes a great advantage from laser ignition, since it does not disturb the cylinder geometry and, more important, eliminates the quenching on flame kernel provoked by electrodes (O’Briant et al., 2016). Using a laser instead of a spark plug gives another interesting result since it can extend the lean flammability limit defined with the spark plug (Xu et al., 2014). The elimination of kernel cooling with electrode-less ignition represents a key feature for the development of hypersonic flight systems (i.e. scramjet), whose combustion occurs in a supersonic flow, hence the characteristic times of chemical reactions are required to be smaller than that of fluid dynamics. In this context, the possibility to improve the combustion stability at high Mach should lead to overcome the current limits of the flight envelope, toward a region of lower dynamic pressure (0.05–0.2 atm) (O’Briant et al., 2016; Starikovskaia, 2006). Therefore, laser ignition is a key technology for improvement and development of current and future aviation systems, also characterized by further, more practical, benefits, such as a simple maintenance and lower reparation costs (O’Briant et al., 2016).