超声悬浮甲醇液滴的热诱导雾化现象  

Phenomenon study on heat induced atomization of acoustic levitated methanol droplet

作　　者：魏衍举[1] 张洁[1] 邓胜才 张亚杰 杨亚晶[2] 刘圣华[1] 陈昊[3] Wei Yan-Ju;Zhang Jie;Deng Sheng-Cai;Zhang Ya-Jie;Yang Ya-Jing;Liu Sheng-Hua;Chen Hao(School of Energy and Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China;State Key Laboratory of Mechanical Strength and Vibration,School of Aerospace,Xi’an Jiaotong University,Xi’an 710049,China;School of Automobile,Chang’an University,Xi’an 710064,China)

机构地区：[1]西安交通大学能源与动力工程学院,西安710049 [2]西安交通大学航天学院,机械结构强度与振动国家重点实验室,西安710049 [3]长安大学汽车学院,西安710064

出　　处：《物理学报》2020年第18期250-257,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51576159);国家自然科学基金重大研究计划(批准号:91741110);陕西省重点研发计划(批准号:2019ZDLGY15-10,2019ZDLGY15-07)资助的课题.

摘　　要：采用外部高温气体加热的方式研究了超声悬浮甲醇液滴的声致破碎雾化现象,利用高速摄像手段记录并实验研究了不同直径液滴不同的破碎雾化特性.结果表明:超声悬浮液滴在高温气流吹扫后可发生边缘喷射雾化现象.破碎方式包含边缘溅射、液膜割裂和法向溅射三类.直径D0较小的液滴直接从赤道面开始边缘溅射直至完全雾化;等效直径D0>2.8 mm的液滴,在产生边缘溅射后,剩余液核弯曲形成液膜,其表面产生法拉第波,使得液膜割裂破碎;而D0>3.2 mm的液滴,在变形过程中逐渐形成“碗状”空腔,并在其底部的法向方向产生溅射,同时开始液膜割裂的离散化解体过程并伴随着边缘溅射,直至完全雾化.这种声致液滴雾化现象丰富了多物理场耦合作用下的流体理论,可为相关应用研究提供新思路.Atomization of droplets is ubiquitous in many natural and industrial processes,such as falling rain drops,inkjet printing,fuel injection in automotive and gas-turbine engines.Acoustic irradiation provides a very effective method of atomizing fluid.However,the acoustic atomization of acoustically levitated droplet is seldom studied.To assess the possibility of achieving ultrafine atomization,we,in this paper,systematically study the atomization of an acoustically levitated droplet placed in a hot gas of a flame.High speed camera is utilized to investigate the atomization characteristics of various droplets with diameters ranging from 0.5 mm to 3.5 mm.The experimental results show that the sound pressure of the resonance acoustic field has the ability to atomize the droplet when it is suddenly bathed in hot gas.Here the heating acts as a switch to convert the droplet surface from an acoustic isolator to conductor by heating the surface to strong evaporation.The presence of a high concentration of vapor molecules surrounding the droplet caused the acoustic field to change,thus,a much larger pressure gradient is established along the droplet surface,resulting in the atomization of droplet from the equator.Furthermore,Faraday wave stimulation and discretization on the film cause the droplet to further disintegrate when the droplet diameter is large enough.The atomization consists of three different styles,i.e.rim spray(RS),film disintegration(FD)and normal sputtering(NS).When exposed to hot gas,the droplets with equivalent diameter D0<2.8 mm are depleted with RS until the whole mass is atomization.A thin rim is extruded at the equator and then splashed in the equator plane,the spray speed is around 9.5 m/s.Larger droplets end with the sudden FD of liquid film of the residual mass after the the RS has been consumed up.When the thickness of the rim and buckled film decrease to half of wave length,Faraday wave emerges,resulting in the vertical droplet ejection and the disintegration of the thin films.And the droplets wit

关 键 词：超声悬浮 液滴 外部加热 雾化 甲醇 

分 类 号：TQ223.121[化学工程—有机化工]