Zang Hongwei, Li Helong, Zhang Wei, Fu Yao, Chen Shanming, Xu Huailiang, Li Ruxin
State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 130012, Changchun, China.
Institute of Atomic and Molecular Physics, Jilin University, 130012, Changchun, China.
Light Sci Appl. 2021 Mar 5;10(1):49. doi: 10.1038/s41377-021-00496-8.
Laser ignition (LI) allows for precise manipulation of ignition timing and location and is promising for green combustion of automobile and rocket engines and aero-turbines under lean-fuel conditions with improved emission efficiency; however, achieving completely effective and reliable ignition is still a challenge. Here, we report the realization of igniting a lean methane/air mixture with a 100% success rate by an ultrashort femtosecond laser, which has long been regarded as an unsuitable fuel ignition source. We demonstrate that the minimum ignition energy can decrease to the sub-mJ level depending on the laser filamentation formation, and reveal that the resultant early OH radical yield significantly increases as the laser energy reaches the ignition threshold, showing a clear boundary for misfire and fire cases. Potential mechanisms for robust ultrashort LI are the filamentation-induced heating effect followed by exothermal chemical reactions, in combination with the line ignition effect along the filament. Our results pave the way toward robust and efficient ignition of lean-fuel engines by ultrashort-pulsed lasers.
激光点火（LI）能够精确控制点火时间和位置，有望实现汽车、火箭发动机以及航空涡轮发动机在贫燃料条件下的绿色燃烧，并提高排放效率；然而，实现完全有效且可靠的点火仍是一项挑战。在此，我们报告了利用超短飞秒激光以100%的成功率点燃贫甲烷/空气混合物，而超短飞秒激光长期以来一直被认为是不适合燃料点火的光源。我们证明，根据激光成丝的形成情况，最小点火能量可降至亚毫焦水平，并揭示出随着激光能量达到点火阈值，产生的早期羟基自由基产率显著增加，显示出熄火和着火情况的清晰界限。超短激光点火稳健性的潜在机制是成丝诱导的热效应，随后是放热化学反应，并伴有沿细丝的线点火效应。我们的研究结果为利用超短脉冲激光实现贫燃料发动机的稳健高效点火铺平了道路。
