注气离心喷嘴喷注过程稳定性试验

为了解管路注气对补燃循环液氧煤油发动机预燃室煤油离心喷嘴喷注过程稳定性的影响，在大气环境下开展了敞口型离心喷嘴注气时喷注过程稳定性试验。使用注气装置在离心喷嘴的上游供应管路中注入空气，通过高速相机记录管路内的两相流特征和喷嘴喷注过程的振荡特征，采用图像区域亮度分析方法定量评估喷注过程的振荡强度。研究发现：注气能显著改变敞口型离心喷嘴的喷注雾化过程及稳定性特征；注气后雾化液膜破碎距离缩短且喷雾角减小，喷注过程出现明显的振荡并伴随Klystron效应；管路内两相流的气泡尺度较大且切向孔较小时，喷注过程的振荡幅值较大；随着注气量增加，喷注过程的振荡频率降低；气泡尺度及两相流型对离心喷嘴喷注振荡过程的影响与普通气泡雾化喷嘴的显著不同，柱状流型时离心喷嘴喷注过程出现1~3 Hz流量振荡且可能间歇性断流。气泡对切向孔的间歇性堵塞作用可能是喷注过程振荡及Klystron效应的原因。

Test on spray stability of swirl injector with gas injection

To understand the stability characteristics of the kerosene swirl injector when gas injected into the feed-line in the pre-burner of staged combustion LOX/kerosene rocket engine, the stability characteristics of open-end swirl injectors with gas injection are investigated experimentally in the atmospheric environment. A gas injection apparatus is designed to inject air into the feed-line of injectors. The two-phase flow processes in the feed-line and the spray processes of the injectors are captured by a high-speed camera. The unsteadiness of the spray processes is evaluated by the image intensity analysis method. It is found that the processes and stability of sprays are significantly changed when the gas injected in the feed-line. The film breakup length and the spray angle decrease and the sprays become unsteady with the Klystron effect. The unsteadiness of the spray is large when the size of bubbles in the feed-line is large and the diameter of tangential orifices of the injectors is small. As the gas-to-liquid ratio increases, the dominant oscillating frequency reduces. The size of the bubbles and the two-phase flow pattern have a significant impact on sprays of swirl injectors different from that of common effervescent atomizers. The frequency of sprays oscillating is about 1-3 Hz when the annular flow pattern is exhibited, showing intermittent flow-stopping. The sprays oscillating and the Klystron effect may induce the periodical block of bubbles to tangential orifices.