中文摘要：

金属燃料降为纳米尺度,燃烧室降至微米尺度,其点火和燃烧将呈现不同的特性。选用非挥发性金属纳米铜为研究对象,分析其氧化过程和燃烧路线,并结合相变分析其燃烧过程中的分裂和微爆炸现象。在微尺度下,常温常压静止空气流中,纳米铜粉的最低点火功率为27.4 m W,最短点火延迟时间低于6 ms。点火延迟时间受点火功率、圆形度和等效粒径等综合因素的影响。纳米铜粉的典型燃烧过程包括燃烧启动、扩散燃烧、弱火焰和淬熄4个阶段。纳米铜粉受激光预热,发生氧化变为熔融铜后发生非均相着火及表面燃烧。铜氧化物部分溶于熔融铜而变成内含物,氮气等溶于熔融铜后,导致纳米铜粉分裂和微爆炸。激光功率高于最低点火功率时,纳米铜粉发生有焰燃烧,火焰面呈圆形,火焰锋面和亮度发生波动,燃烧不稳定。微尺度下,纳米铜粉的燃烧存在弱火焰形式,进而发生淬熄,淬熄后的燃烧产物保持圆形。

英文摘要：

The ignition and combustion characteristics of fuels composed of nano-metal at the micro-scale would be different from those of micron-sized metal at the macro-scale and meso-scale combustors. The oxidation of non-volatile nano copper powders was analyzed,and its combustion route was carried out. During the combustion,the split and the micro-explosion phenomena of nano copper powders were demonstrated and discussed on the basis of the binary Cu-O phase diagram. At the micro-scale,in a stagnation air flow at the atmospheric pressure,the minimum ignition power of nano copper powders is 27. 4 m W,and the shortest ignition delay time is below 6 ms. Ignition delay time is influenced by ignition power,roundness and equivalent diameter of nano copper powders.The classical combustion of nano copper powders includes four stages,i. e.,the startup of combustion,diffusive combustion,weak flame and extinction. After nano copper powders are preheated by the laser,copper powders take oxidation reaction and become molten copper,and then take heterogeneous ignition and surface combustion. A part of copper oxide dissolves in molten copper and becomes inclusion. Simultaneously,nitrogen also dissolves in molten copper,resulting in the occurrence of split and micro-explosion phenomena during the combustion. As the laser power is beyond the minimum ignition power,nano copper powders combust with bright flame,and the shape of combustion flame looks like circle. The fluctuation of the flame front and flame brightness shows instable combustion. At the micro-scale,the diffusion combustion followed by the weak flame,and the flame eventually extinguishes. The round combustion residues can be clearly observed after extinction.