Laser cleaning of optical windows in internal combustion engines
Laser cleaning of optical windows in internal combustion engines
复制标题
内燃机光学窗口的激光清洗
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
F. Winter
中科院分区：
文献类型：
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作者：
Helmut Ranner;P. Tewari;H. Kofler;M. Lackner;E. Wintner;A. Agarwal;F. Winter
通过窗户进入燃烧室的光学通道对于燃烧诊断和激光点火都是理想的。从本质上讲，在透光窗的内表面会形成燃烧沉积物，从而导致故障。本文研究了Nd:YAG点火激光器能否通过烧蚀的方式处理燃烧室沉积。在一台1.8千瓦的四冲程内燃机中，安装了一个光学窗口来耦合激光。点火是由火花塞进行的。由于固有的高燃料和机油消耗，在几十分钟内就会在基材上形成沉积层。元素分析表明，碳质和无机化合物逐渐降低了透光性。当5-ns的激光循环穿过窗口时，只要能量影响约为10 mJ/mm2，穿透层基本上没有沉积。微量分析显示了这一原理的合理性。此外，即使是高通量的单次射击也足以一次清除相对较厚的沉积物层。因此，内燃机中的光学窗口原则上可以通过紧凑的固态激光器的作用来保持透射。
Optical access to combustion chambers via windows is desirable for combustion diagnostics as well as for laser ignition. By nature, combustion deposits can form on the inner surface of the light-transmitting window, leading to malfunction. We investigated whether a Nd:YAG ignition laser could cope with combustion-chamber deposits by means of ablation. In a 1.8-kW four-stroke internal combustion engine an optical window was installed to couple in the laser light. Ignition was carried out by a spark plug. Due to inherent high fuel and oil consumption, a deposit layer would form on the substrate within some tens of minutes. Elementary analysis showed carbonaceous as well as inorganic compounds gradually reducing light transmission. With cyclic 5-ns laser shots through the window, the pass-through stayed essentially free of deposits provided the energy fluence was around 10 mJ/mm2. Microanalysis showed evidence of the soundness of the principle. In addition, even single shots with a higher flux were enough to remove a relatively thick layer of deposits at once. Thus an optical window in an internal combustion engine can in principle be kept transmissive by the action of a compact solid-state laser.