摘要
为了深入研究闪急沸腾喷雾二次破碎即大尺度液滴的破碎机理,本课题以甲醇和乙醇两种燃料为研究对象,利用特殊设计的过热液滴发生器,通过显微阴影成像技术捕捉并分析处于闪沸状态过热液滴的宏观形态、内部空隙率及其破碎特性,研究表明:甲醇及乙醇两种燃料的过热液滴形态主要受液滴温度和过热度影响,而当过热度增加时,液滴内空隙率逐渐增加,从而显著降低了液滴的表面张力。此外,当过热度达到250C时,过热液滴内部空隙率超过50%从而发生剧烈破碎,伴随产生大量小尺度液滴,标志着闪沸喷雾二次破碎模式由传统的机械破碎模式向热力学破碎模式的转变。同时结果表明对于两种实验燃料,过热液滴破碎的临界过热度及对应的空隙率数值基本不变。
In order to reveal the secondary breakup mechanism of flash-boiling spray, a superheated droplet generator was developed for observing the droplet morphology, the bubble formation as well as the breakup process resulting from the vapor bubbles inside a superheated methanol/ethanol droplet by microscopic imaging. It was found that for both methanol and ethanol fuels, the droplet morphology is mainly influenced by droplet temperature and superheat degree, but the void fraction resulting from bubbles formation and the surface tension of superheated droplet are dominated by superheat degree. The superheat degree of 25~C is an important critical point at which the droplet breakup occurs due to the ever-increasing void fraction exceeding a value of approximately 50%, and the breakup mode shifts from aerodynamic mode to thermodynamic mode. Furthermore, the critical values of superheat degree and void fraction at which the superheated droplet breakup occurs are the same for methanol and ethanol fuels.
出处
《工程热物理学报》
EI
CAS
CSCD
北大核心
2017年第11期2485-2490,共6页
Journal of Engineering Thermophysics
基金
国家自然科学基金(No.51376120)
教育部博士点基金(No.20120073110046)
关键词
闪急沸腾
二次破碎
雾化
液滴发生器
过热液滴
flash-boiling
secondary breakup
atomization
droplet generator
superheated droplet
