气液同轴双离心式喷嘴宏观雾化特性实验研究

Experimental Study on Macro-Spray Characteristics of Gas-Liquid Double Swirl Coaxial Injectors

为掌握燃气轮机燃烧室喷嘴的雾化规律并优化其雾化效果,本文以液态水为工质,对新型气液同轴双离心式喷嘴雾化特性展开实验研究。利用粒子图像测速法研究了改变气、液进口压力对雾化液滴速度场、雾化锥角和液膜破碎长度的影响,通过分析雾化图像对喷嘴的雾化机制进行探究。结果表明,液体进口压力不变时,气体进口压力增加可使雾化状态由空心锥状向实心锥状过渡,同时液膜破碎依次经历了表面波主导破碎、波动雾化破碎以及气动雾化破碎三种模式。液体进口压力为0.7MPa时,气体进口压力增大,雾化模式由表面波破碎向波动雾化破碎过渡,雾化液锥收缩,液膜受气动力作用向下游展开,液膜破碎长度呈先增大后减小的规律。雾化处于气动雾化破碎模式时,雾化锥角逐渐稳定。对喷嘴下游40mm处液滴速度值分析表明,随着液压增大,有/无气旋对雾化液滴速度增幅稳定在8%。

In order to grasp the atomization law of injector and optimize its spray effect in gas turbine com bustion chamber,a new gas-liquid double swirl coaxial injector was employed to investigate spray characteristics under the working medium of water.The effects of gas and liquid inlet pressure on the velocity field of spray drop lets,spray cone angle,and liquid film breakup length were studied using particle image velocimetry,and the spray mechanism of the injector was investigated by analyzing spray visualizations.The results showed that when the liquid inlet pressure kept constant,the atomization state changed from a hollow cone to a solid cone with the increase of gas inlet pressure.Meanwhile the liquid film breakup experienced three modes of surface wave domi nated breakup,fluctuating spray breakup and pneumatic spray breakup in turn.When the liquid inlet pressure was 0.7MPa,the spray breakup mode changed from surface wave breakup to fluctuating spray breakup and the spray liquid cone shrinked with the increase of gas inlet pressure.Meanwhile,the liquid film was expanded down stream by the aerodynamic effect,and its breakup length increased first and then decreased.When the atomiza tion was in the pneumatic spray breakup mode,the spray cone angle was gradually stabilized.The analysis of droplet velocity values at 40mm downstream of the injector showed that the growth rate of droplet velocity stabi lized at 8%with/without cyclone as the liquid inlet pressure increased.