气喷嘴和声腔对燃烧室声学特性的影响

Effects of gas nozzle and resonators on acoustic characteristics of combustion chamber

为了掌握气喷嘴和声腔对燃烧室声学特性的影响规律以及解释声学实验中出现的切向频率分化现象的内在机理,采用声学有限元方法(FEM)并在单喷嘴声学模拟实验验证的基础上,从固有频率和声压分布角度分析了气喷嘴长度、声腔长度和节流嘴直径对燃烧室声学特性的影响规律,利用声压分布成功地解释了实验中出现的频率分化现象。结果表明:当燃烧室某阶切向振型频率与喷嘴1阶纵向振型频率相等时,喷嘴由于共振将切向振型声压幅值极值点附近的能量转移到喷嘴中,改变了燃烧室原切向振型的声压分布,因此在声学实验中产生切向频率分化现象;气喷嘴长度与节流嘴直径之间存在着耦合关系,在液氧煤油补燃发动机喷嘴设计阶段可进行组合参数匹配优化。

In order to obtain the influence of gas-liquid nozzle and acoustic resonators on the acoustic characteristics of combustion chamber and explain the mechanism of tangential frequency differentiation in acoustic experiments,a model combustion chamber with cylindrical tubes was investigated by acoustic finite element method(FEM).The analysis results were verified by the experiment of a single injector chamber.On this basis,the influence rules of gas nozzle,orifice and resonators on acoustic frequency were established in terms of the frequency and sound pressure distribution.The phenomenon of frequency differentiation was explained by the sound pressure distribution results.Results showed that the energy of tangential mode transferred into the gas nozzle and changed the original mode of combustion chamber,when the frequency of first order longitudinal mode of gas nozzle or resonator was equal to that of the tangential mode of combustor,and the phenomenon of frequency differentiation in tangential modes emerged in acoustic experiments.The coupling relationship between gas nozzle length and diameter of orifice was discovered,enabling to make combinatorial parameter optimization during rocket engine design.