燃烧室的声学特性分析及声抑制装置的研究

【作者】 樊晓波；

【导师】 王敏庆；

【作者基本信息】 西北工业大学 ， 武器系统与运用工程， 2007， 硕士

【摘要】 燃烧不稳定性问题是发动机燃烧室研制过程中所遇到的难题之一，它具有极强的破坏作用。而燃烧不稳定性的非稳态运动与燃烧室固有声学阵型之间存在着惊人的相似性，因此本文从声学的角度来对不稳定燃烧的抑制问题进行研究。 本文选题于国家自然科学基金项目，以某型水下航行器的燃烧室为研究对象，采用理论分析、数值计算和实验研究相结合的方法，对燃烧室的声学特性进行了研究。研究结果对发动机的燃烧稳定性设计具有一定的参考价值。 本文首先建立了发动机燃烧室的简化模型，通过燃烧室内基本方程的推导，建立了燃烧室内的声学波动方程，求解了常温常压条件下燃烧室内的声学共振频率的理论解。与此同时，利用有限元软件ANSYS建立了燃烧室的有限元模型，获得了燃烧室内的声学共振频率的数值解；建立了燃烧室结构的有限元模型，获得了燃烧室结构的共振频率。 为了验证分析结果的合理性以及声学共振频率的特征，在常温常压下，对燃烧室的缩比模型进行了声学试验，获得了常温常压下燃烧室的声学共振频率的试验结果。并通过对上述理论解、数值解和实验结果的对比分析，获得了常温常压条件下燃烧室的声学共振频率。通过联合考虑燃烧室结构的共振频率和燃烧不稳定性的研究经验，预测了致使燃烧室发生不稳定燃烧的固有声学振型。 论文还利用有限元软件ANSYS从声学的角度研究了声抑制装置—隔板抑制燃烧不稳定的机理，并对比分析了隔板的数目和长度分别变化时对其抑制作用的影响。文中还分析了赫姆霍兹谐振器和微穿孔板结构吸声体的吸声特性，并根据马大猷先生的微穿孔板理论给出了微穿孔板结构设计的步骤。研究表明：本文中所采用的隔板形式可以使燃烧室中的切向声学振型轴向化，并且切向声学共振频率也会降低。同时，隔板长度增加时，燃烧室内的切向振型轴向化进一步加剧，但是，当隔板增长到一定程度时，会形成隔板结构与燃烧室内声场的耦合振动，致使隔板在低频时的抑制效果减弱。隔板数目增加的时候，隔板的抑制频带会进一步的加宽。采用微穿孔板结构作为声抑制装置部件具有结构小、抑制频带较宽的优点。更多还原

【Abstract】 Combustion instability, encountered in the development of researches of liquid propellant engines, is one of the significant challenges, which has tremendous destructivity. It can be characterized by an energy feedback loop between acoustic oscillations and transient combustion response.This thesis is supported by the project of National Nature Science Foundation of China (NSFC). In this paper, the combustion chamber of some underwater vehicle is taken as the object to be studied, and the study on the acoustic characteristic of the combustion chamber is performed by the theoretical analysis and numerical computation combined with the experimental measure. The result is significative as a reference for the engine designer.Firstly, the theoretical computation model of combustion chamber cavity is constructed in the paper, and the acoustic wave equation is obtained by the fundamental equations in the combustion chamber, thereby the theoretical results of the acoustic oscillation frequency are acquired.Secondly, the finite element method (FEM) models of combustion chamber cavity and combustion chamber structure are built, therefore the numerical results of acoustic oscillation frequency and the structure vibration frequency are acquired.Thirdly, in order to validate the validity of results of analysis and computation, under the circumstance of normal room temperature and pressure, the acoustic experiment for scaling model of combustion chamber is performed, thereby the experimental result of acoustic oscillation frequency is obtained.By comparing the above-mentioned theoretical results, numerical results with the experimental data and considering the experience of studying the combustion instability, the hazardous acoustic oscillation frequency is forecasted, which possibly lead to combustion instability.On the basis of the above-mentioned, the mechanisms of restraining the combustion instabilities with baffles in the marine engine combustion chamber has been studied by using FEM software ANSYS for two- and three-dimensional cases. When the length of baffles and the number of baffles are changed, the acoustic modes of the combustion chamber have been calculated, and the differences of these modes have been compared. The results show that the transverse mode shape is更多还原