柴油乳化液喷雾闪急沸腾与微爆现象的激光阴影试验研究

摘要

An experimental study was conducted to determine the changes in the droplets along the spray length for the water-in-diesel oil with different water contents in a confined space at atmospheric pressure and specified test tem-perature. These effects are studied and traced by using the droplets direct photography, and droplet size distribution. Measurements of the droplet size were achieved by using images taken with a high-resolution CCD Camera synchro-nized with Nd: YAG Laser, Shadowgraph technologies, and analyzed with Particle Sizing software. The Resuhs reveal that the pressure of water in water-in-diesel oil droplets determines the occurring possibility of both flash boiling and micro-explosion phenomena. Micro explosion is mainly due to the violent vaporization of water in the droplets of water-in-diesel oil or in another word due to the occurrence of flash boiling breakup. Water vapor molecules rupture the diesel oil shell of the droplets, leading to the subdivision of the main droplets into many smaller droplets in addition to liberation of the tiny droplets inside the main droplets. The flash boiling and the micro explosion continuously occur in the liberated tiny droplets as the ambient temperature is 130 ℃ and atmospheric pressure. Hence, micro explosion leads to the successive subdivision of big water-in-diesel oil droplets into tiny droplets and consequently replaces the large droplets with huge number of tiny droplets.%在常压定容室内,应用ND:YAG激光阴影法、高分辨率CCD照相机和粒径分析软件,对不同含水量的柴油乳化液雾油滴的闪急沸腾与微爆现象以及油滴粒径分布进行了试验测量与变参数对比分析,探讨了在130℃温度条件下,乳化油含水量对乳化油喷雾液滴闪急沸腾和微爆的影响,揭示了微爆效应在喷雾雾化和液滴碎化中的作用机理.试验结果表明,包覆于油中的水相颗粒受热闪急沸腾所形成的高压蒸气团冲破无水边界层是导致油滴发生微爆和进一步破碎分裂的首要原因;微爆现象随乳化油含水量的增高而趋强;喷雾索特平均直径(SMD)的细化率随乳化油含水量和喷雾贯穿距的增加而增大,且乳化油含水量对喷雾SMD细化率的影响程度也随喷雾贯穿距的增加更加显著.