Analysis Of Aero-Engine Annular Combustion Chamber Flame Tube Vibration Modes And Acoustic Modes

Aero-engine combustion chamber works in the environment of high-temperature and high-noise. The sonic fatigue and thermal fatigue are easily happened, which can seriously affect the life of the combustion chamber, and even the whole aero-engine's life. Combustion instability not only affects the stability of the aero-engine work, but also caused the combustion chamber flame tube thin-walled structure acoustic-vibration coupled fatigue. And there are some connections between the acoustic mode and the combustion instability. Consequently, in order to improve the fatigue life of the combustion chamber flame tube, it is particularly important to analyze vibration and acoustic characteristics of the aero-engine annular chamber flame tubes. In this paper, by the finite element method (FEM), the vibration modes and acoustic modes were studied. Then the natural frequency and mode shapes were obtained. And the acoustic test was completed too.In this paper, based on the vibration differential equations of thin shell structure, combined with the characteristics of the shell structure, the free vibration equations of the thin shell were given, as well as the forced vibration differential equations under the random loads. At the same time, the theory of space acoustic wave equations, acoustic finite element equations and acoustic-structural coupled control equations were given. Based on the ANSYS finite element software, the vibration modes of annular combustion chamber flame tube have been calculated. Influences caused by the holes on the wall of the combustor and the temperature field in analyzing the vibration characteristics of the combustor were investigated. Acoustic modes of annular combustion chamber flame tube were calculated. Under the circumstance of normal room temperature, the acoustic characteristics under closed and open state were analyzed. And so did it under the high temperature. According to the cylinder size of the combustion chamber, a simplified model as the acoustic test model was designed. Then the results through the test were compared with the results of the finite element method. The research of aero-engine annular combustor flame tube vibration modes and acoustic modes is of great engineering application values to analyze and solve the sonic fatigue problems and then improving its structure dynamic strength.