Review: Multipoint laser ignition system and its applications to IC engines

Investigation of the effects of passive pre-chamber nozzle pattern and ignition system on engine performance and emissions

“…6,7 Potential drawbacks, however, include poor cyclic stability and elevated unburned hydrocarbons (HC) and carbon monoxide (CO) emissions. 1,8,9 A viable approach to improve cyclic stability under fuel-lean operation is to promote more repeatable ignition processes through the use of advanced ignition technologies such as laser ignition, [10][11][12][13][14] non-equilibrium plasma discharges, [15][16][17][18][19] or pre-chamber (PC) ignition systems. [20][21][22][23][24] Of the three igniter technologies listed, PCs have been found to promote the greatest extension of lean stability limits across a wide range of engine loads and speeds, with associated benefits in terms of both emissions and efficiency.…”

Robust and ultralow-energy-threshold ignition of a lean mixture by an ultrashort-pulsed laser in the filamentation regime

“…Laser ignition (LI) is a promising electrode-less alternative to electronic spark ignition of lean-fuel/air mixtures, offering high thermal efficiency with low harmful emissions 1 . One of the most widely adopted LI methods is nanosecond laser-induced spark ignition (ns-LISI) [2][3][4][5][6][7] , in which combustible mixtures undergo multiphoton ionization followed by avalanche breakdown, resulting in high-temperature and high-pressure plasma along with shockwaves. After shockwave expansion, the hot plasma consisting of many atoms and ions cools, and evolves to the flame kernel, finally developing complete combustion through chemical branching reactions.…”

“…Recent studies have revealed that fuel molecules can be activated and even fragmented by high-intensity laser filaments, producing many combustion intermediates 15 . In particular, the long filament provides the possibility of "multipoint" ignition along the filament, hereafter referred to as "line" ignition, which may improve the ignition reliability of lean mixtures 7 . In addition, inside the fs laser filament, although the initial temperature of gas molecules determined through various energy deposition pathways, such as multiphoton/tunnel ionization, dissociation, Raman excitation, and collision excitation [16][17][18][19][20][21] , is only~1400 K (ref.…”

Multi-point, pulse-train laser ignition of methane-air mixtures by a high-peak power passively Q-switched Nd:YAG/Cr4+:YAG compact laser

“…Furthermore LI is a suitable technique for igniting lean fuel mixtures, thus reducing emissions without decreasing engine power [2][3][4]. A laser beam offers also the possibility to control the ignition spatially, by simultaneous ignition in several points [5,6], as well as temporally, by using a train of laser pulses for a single ignition event. In the case of LI at several points, the combustion time is reduced and the flame can lose less heat, resulting in higher temperatures and higher pressures.…”

“…In the case of LI at several points, the combustion time is reduced and the flame can lose less heat, resulting in higher temperatures and higher pressures. All experiments conducted so far on LI at several points have used large commercial lasers, and the laser beams have been directed to and then focused in a static combustion chamber or in the engine cylinder using various optical systems [6]. In addition, there are very few reports of multi-pulse laser ignition [7].…”