平板式预膜喷嘴初次雾化特性试验

为深入了解平板式预膜喷嘴初次雾化特性,试验研究不同进口条件对平板式预膜喷嘴初次雾化特性的影响规律。试验采用了背光照明和片状激光照明相结合的高频拍摄手段分别获得液膜俯视和侧视破碎形态,同时运用本征正交分解(POD)法和液膜边缘定位等分析方法进行光学图像结果后处理,获得表征平板式预膜喷嘴初次雾化特性三个物理量:液膜波动频率、破碎距离和横向不稳定波长。试验结果表明:①通过分析侧视和俯视破碎形态,平板式预膜喷嘴液膜破碎形态可分为三类:末端破碎、波浪脱落和表面剥离,进口韦伯数对预膜喷嘴破碎形态的影响占主导地位;②把POD法和液膜边缘定位方法等相结合方法应用到高频非接触光学喷嘴雾化图像的后处理分析中,是一种非常有效的数据后处理方法;③液膜初次雾化特性主要受到进口韦伯数和气液动量比的影响,破碎距离和横向不稳定波长都随进口韦伯数的增加而降低,液膜表面不稳定波动频率随进口韦伯数的增加而增加,所获得的经验关系式与试验数据吻合较好。所获得的进口参数对液膜破碎形态和雾化特性的影响规律为喷嘴后续优化设计提供了依据。

Experiment on primary atomization characteristics of planar prefilming nozzle

To understand the primary atomization characteristics of the planar prefilming nozzle, the atomization experiment was carried out to study the influence of different inlet conditions. The high-frequency imaging method of backlight illumination and sheet laser illumination was used to obtain the liquid film breakup morphology in top view and side view. At the same time, the optical image was processed using proper orthogonal decomposition(POD)statistical analysis and the liquid film edge position analysis method, three physical quantities of the primary atomization characteristics were obtained:the main frequency of the liquid film surface wave, the breakup length and the transversal wave length. The experiment results indicated that: (1) the three liquid film breakup morphologies in the planar prefilming nozzle primary atomization process were divided into end breaking, wave dropping and surface stripping based on the breakup morphology of side view and top view. The effect of inlet Weber number on breakup morphology of the prefilming nozzle was dominant. (2) The combination method of POD analysis and liquid film edge position analysis was applied to the post-processing analysis of the high-frequency non-contact optical image, as an effective data post-processing method. (3) The effect of inlet Weber number played an important role in liquid film breakup morphology. The primary atomization characteristics of the liquid film were mainly affected by the inlet Weber number and the gas-liquid momentum flux ratio. Both the breakup length and the transversal wave length decreased with the increase of the inlet Weber number, the frequency of the liquid film surface wave increased with the increase of the inlet Weber number and the obtained formula is in good agreement with the experiment data. The effect of the inlet parameters on the breakup morphology and atomization characteristics of the liquid film provides a basis for effectively optimizing the atomization quality of the prefilming nozzle.