Preliminary experimental study on the crushing length of centrifugal single and double injectors liquid film
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摘要: 为贴合工程实际应用，了解双喷嘴与单喷嘴的雾化特性差异，本文对相同工况下液体中心型同轴离心式纯液相单、双喷嘴液膜破碎长度开展了实验研究。采用高速摄像机对瞬态喷雾图像进行了捕捉，提取了不同工况的双喷嘴液膜破碎长度，并与单喷嘴液膜破碎长度进行了对比分析。通过图像处理获取液膜表面波，从而对单喷嘴与双喷嘴液膜破碎长度产生差异的机理进行分析。结果表明：相同工况下双喷嘴的液膜破碎长度小于单喷嘴，单喷嘴与双喷嘴的液膜破碎长度之间的差异呈现先增加后减小的趋势；文中定义的波长增长率反应了破碎前液膜的不稳定程度，单喷嘴液膜表面波的波长增长率随着液体质量流率的增大而增大，对于双喷嘴其破碎前液膜的不稳定，不仅与初始工况有关还与液膜撞击后产生扰动的作用距离有关，从而使双喷嘴液膜表面波的波长增长率随着质量流率的增加，呈现先增大后减小的趋势。Abstract: In order to fit the actual application of engineering and understand the variations of atomization characteristics of the dual injectors and the single injector, an experimental study on the liquid film breakage length of the liquid-centered coaxial centrifugal pure liquid-phase single-injector and dual-injectors under the same working conditions was carried out in this paper. A high-speed camera was used to capture the transient spray images, and the liquid film breakage lengths of the dual injectors under different working conditions were extracted and analyzed in comparison with those of the single injectors. The surface waves of the liquid film were obtained through image processing to analyze the mechanism of the variations between the liquid film breakage lengths of the single injector and dual injectors. The results show that the liquid film breakage length of the dual injectors is smaller than that of the single injector under the same working condition, and the difference between the liquid film breakage lengths of the single injector and dual injectors show a tendency of increasing and consequently decreasing. The wavelength growth rate defined in the paper reflects the degree of instability of the liquid film before breakage, and the growth rate of the wavelength of the liquid film surface wave of the single injector increases with the increase of the mass flow rate of the liquid, while that of the dual injectors shows that the instability of the liquid film before breakage is not only related to the initial working condition, but also related to the distance between the liquid film impact and the action of the perturbation, so that the wavelength growth rate of the double injectors liquid film surface wave increases first and then decreases with the increase of the mass flow rate.
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图 1 常压雾化实验系统原理图
Figure 1. Schematic diagram of atomization experimental system under atmospheric pressure
图 3 液膜破碎长度提取过程示意图
Figure 3. Schematic diagram of the extraction process of liquid film crushing length
图 5 单、双喷嘴的液膜破碎长度随液体质量流率的变化情况
Figure 5. Changes of liquid film breaking length of single and double nozzles with liquid mass flow rate
图 6 单、双喷嘴表面波发展区间
Figure 6. Development range of single and double nozzle surface waves
图 9 波长增长率与振幅
Figure 9. Growth rate and amplitude of the most unstable wave's wavelength
表 1 喷嘴尺寸参数
Table 1. Geometrical conditions of injector
参数 值 液喷嘴等直段直径Dz 4.7 mm 气喷嘴环缝内径Dg-in 8 mm 气喷嘴环缝外径Dg-out 9 mm 液喷嘴旋流室直径Ds 10.2 mm 旋流室高度Ls 10.2 mm 切向孔直径Dt 2 mm 切向孔中心轴线到液喷嘴中轴的距离Rs 4 mm 收缩角θ2 90° 扩张角θ1 10° 两喷嘴中轴线距离Lsp 20 mm 等值段长度Lz 40 mm 
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表 2 实验工况
Table 2. Experimental operating conditions
模拟液体推进剂 模拟介质 过滤水 喷注压降$\Delta $p 0.119～0.864 MPa 液体质量流率${\dot m_{\rm{l}}}$ 50～140 g/s
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