气核尺寸对气液同轴离心式喷嘴自激振荡的影响

Influence of Gas Core Dimension on Self-pulsation of Gas-liquid Swirl Coaxial Injector

为了研究气核尺寸对气液同轴离心式喷嘴自激振荡的影响,采用水和空气作为模拟介质,开展了室压条件下冷态喷雾试验.通过试验分析了气核尺寸较大时气液同轴离心式喷嘴自激振荡的喷雾形态,与文献中气核尺寸较小时的喷雾形态进行对比发现气核尺寸不同时,该类喷嘴自激振荡的喷雾形态不同,气核尺寸较大时呈“圣诞树”型分布,气核尺寸较小时呈“串”型分布.气核尺寸对气液同轴离心式喷嘴自激振荡的产生机理有显著影响,由于自激振荡产生机理的不同,喷嘴缩进长度对自激振荡的影响也不同,气核尺寸较大时自激振荡频率随着喷嘴缩进长度呈复杂变化特征,气核尺寸较小时喷嘴缩进长度对自激振荡频率没有影响.气液同轴离心式喷嘴自激振荡频率为2～4 kHz,与燃烧室一阶振型接近,喷雾自激振荡可能会诱发燃烧室不稳定燃烧.

To understand the influence of gas core dimension on self-pulsation characteristics of gas-liquid swirl coaxial injector,non-reactive spray experiments are conducted with water and air at atmospheric pressure.The spray morphology of gas-liquid swirl coaxial injectors with different gas core dimensions is investigated while self-pulsation happens.Self-pulsation morphology changes with gas core dimension; the spray looks like a Christmas tree with a large gas core,and a string of pearl with small gas core.The results indicate that gas core dimension significantly affects the self-pulsation mechanism,which in turn varies the influence of recess length on self-pulsation.Self-pulsation frequency varies complicatedly with recess length when gas core dimension is large enough.But with a small gas core,the recess length can hardly change the frequency of self-pulsation.In general,self-pulsation frequency is in the range of 2-4 kHz,which corresponds to frequency range of first transrerse mode in combustion instability.Namely,self-pulsation can trigger combustion instability.