气液同轴敞口型离心喷嘴的自激振荡特性实验

An Experimental Investigation on Self-Pulsation Characteristics of Gas/Liquid Open-End Swirl Coaxial Injector

为了研究气液同轴敞口型离心喷嘴的自激振荡特性,采用阴影法和动态测量系统开展了常温大气环境中的喷嘴雾化试验。喷嘴自激振荡时,出口附近存在明显的周期性雾化过程,上游瞬态压力形成周期性脉动,压力脉动、噪音和雾场图像频率高度一致,范围约为1583~5634 Hz。通过试验分析了喷嘴流量特性规律,在雾场稳定时和自激振荡时气相与液相相互阻塞均会造成喷前压力升高,液相流量对气相喷前压力影响较大。喷嘴自激振荡频率随气相和液相流量增长,相对液相流量较为敏感,液相流量增至一定临界值,自激振荡消失,而气相流量增长始终伴随自激振荡频率缓慢提高。喷嘴存在自激振荡产生的上下液相边界条件,自激振荡范围随着气相流量增大而变宽,气相对自激振荡起促进作用,而液相阻碍了自激振荡发展。增加内喷嘴壁面厚度时,液膜厚度增加,无量纲气核尺寸减小,自激振荡频率增大。

In order to understand the self-pulsation characteristics of the gas/liquid open-end swirl coaxial injector,the atomization test in the atmospheric environment is carried out by adopting the shadow method and the dynamic measurement system.The exit of injector nearby presents a periodic spray process significantly with upstream transient pressure responding repeatedly,while self-pulsation happens.Moreover,the frequency of former pressure,acoustic pressure and spray graphics are highly consistent,ranging from 1583 Hz to 5634 Hz.Through analyzing flow rate discipline,it s concluded that the injection pressure always presents increasing due to the interaction of gas phase and liquid phase,whether the atomization field displays stable or self-pulsation.As well,liquid flow has stronger influence on the injection pressure than gas flow.The results show that self-pulsation frequency increases with gas phase and liquid phase mass flow,and is relatively sensitive to liquid phase mass flow.As the liquid mass flow growing to critical level,the self-pulsation disappears.Then the self-pulsation frequency keeps improving slowly with gas mass flow increasing.The open-end swirl coaxial injector has the upper and lower liquid phase boundary condition generated self-pulsation,and the range widens as gas phase increases.So the gas phase promotes self-pulsation,however liquid phase hampers the development of the self-pulsation.When the liquid swirl injector s wall is thickened,the liquid film thickness increases and the dimensionless gas core shrinks.Furthermore,the self-pulsation frequency of the new coaxial injector is larger than that of the original one.