Acoustic Characteristics Of The Combustion Chamber And Sound Suppression Device

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...