同轴离心式喷嘴火焰结构的转变和迟滞  

Transition and Hysteresis of Flame Shape in a Swirl Coaxial Injector

作　　者：杨尚荣 李娜 吴林龙 王勇 杨宝娥 连俊凯 Yang Shangrong;Li Na;Wu Linlong;Wang Yong;Yang Baoe;Lian Junkai(Science and Technology on Liquid Rocket Engine Laboratory,Xi’an Aerospace Propulsion Institute,Xi’an 710100,China)

机构地区：[1]西安航天动力研究所液体火箭发动机技术重点实验室,西安710100

出　　处：《燃烧科学与技术》2024年第3期255-264,共10页Journal of Combustion Science and Technology

基　　金：国家自然科学基金资助项目(51606138).

摘　　要：针对气体中心液体离心式同轴(GCLSC)喷嘴(简称为同轴离心式喷嘴)的燃烧动力学特性,开展富氧气/煤油蒸气同轴离心式单喷嘴实验研究.通过改变氧化剂喷射速度,分别获得了稳定和自发激励条件下的火焰结构、相互转变和迟滞过程.利用高速相机拍摄了火焰的CH^(*)自发光图像,通过离散傅里叶变换(DFT)和动力学模态分解(DMD)方法分析了燃烧流场的空间结构.研究发现:稳定燃烧时,火焰长度较长,CH^(*)自发光紧贴喷嘴出口,火焰结构受反应混合层流动不稳定控制.迟滞区域内,火焰出现抬升,CH^(*)自发光强度沿流向存在两个峰值,主导的不稳定频率较高.不稳定燃烧时,火焰长度显著缩短,且在横向扩展,沿喷嘴周向有部分火焰紧贴喷嘴出口.3种燃烧状态下,DFT和DMD方法得到的空间模态均很相近.发现了螺旋形结构的低频火焰模态,某些工况下会发生对流形式的燃烧不稳定.一阶切向不稳定的火焰模态表现为速度耦合产生的螺旋形不稳定涡结构,二阶切向不稳定的火焰模态表现为压力耦合产生的对称涡结构.An experimental study was conducted to investigate the combustion dynamics of a gas centered liquid swirl coaxial(GCLSC)injector(referred to as a swirl coaxial injector)with oxygen-rich/kerosene vapor.By changing the injection speed of oxidizer,the transition and hysteresis of flame shapes under stable combustion and spontaneous excitation conditions were obtained.The CH^(*)chemiluminescence images of flames were taken using a high-speed camera and analyzed using discrete Fourier transform(DFT)and dynamic mode decomposition(DMD)methods.It is found that during stable combustion,the flame length is long,and the CH^(*)chemiluminescence is closely attached to the injector outlet.The flame structure is controlled by hydrodynamic instability of the reaction mixing layer.In the hysteresis region,the flame lifts up,and there are two peaks of CH^(*)chemiluminescence intensity in the streamwise direction.The dominant unstable frequency is high.When unstable combustion occurs,the flame lengths are significantly shortened and expand laterally.Only partial flames are closely adhering to the injector outlet along the circumference.The spatial modes obtained by DFT and DMD methods are very similar under the three combustion states.The flame modes with a spiral structure have been discovered,which,under certain operating conditions,can lead to low frequency convective combustion instability.The flame modes corresponding to first order tangential acoustic frequency exhibit a spiral vortex structure caused by velocity coupling,while those corresponding to second order tangential acoustic frequency exhibit a symmetrical structure caused by pressure coupling.

关 键 词：同轴离心式喷嘴 燃烧稳定性 火焰结构 迟滞 模态分解 

分 类 号：V231.1[航空宇航科学与技术—航空宇航推进理论与工程]