Research On Vibration Response Analysis Of Flame Tubes Under Stochastic Acoustic Excitation

The combustion chamber is one of the core parts of aero-engines.Its life and performance are the determinations of the reliability,economy and life of the engine.The actual working conditions of the combustion chamber are very server.During the vibration process,the vibration stress and acoustic excitations will generate on the structure.In order to improve the fatigue life of the aero-engine combustor thin shell structure,it is very important to investigate the vibration characteristics of the structure under acoustic excitation.The problem of structural vibration under acoustic excitation is a kind of random vibration problem.In order to study the random vibration problem of the thin shell structure of the flame tube,the definition of white noise is introduced firstly.The dynamic model of rectangular thin plate under arbitrary boundary conditions has been derived by improved Fourier series method,and the random vibration response of rectangular thin plate under arbitrary boundary condition has been analyzed by combining pseudo excitation method.Combined with the ANSYS harmonic response analysis module,the random vibration response analysis program based on pseudo excitation method has been developed then.At the same time,the random vibration experiment with a plate has been carried out,and the response spectrum of the plate has been obtained,the experimental results agree well with the calculated results.Then the correctness of theoretical calculation model and random vibration response analysis program based on pseudo excitation method has been verified.Second,modal analysis considering the influence of acoustic-structural coupling and temperature load has been carried out on the simplified flame tube structure.It is found that the acoustic-structural coupling and temperature load have great influence on the modal of the structure.And the response of random vibration of open-hole flame-tube thin-walled structure has been analyzed under acousticstructural coupling and temperature load,the displacement response and Von Mises stress response spectrum have been obtained using the pseudo excitation method.The results show that the acousticstructural coupling and temperature load have a great influence on the response spectrum.Finally,the Von Mises stress-response power spectral density calculated above has been transformed into the amplitude probability density using the Tovo-Benasciutti model and the Drilik model,and the Miner linear cumulative damage theory has been used to estimate the acoustic fatigue life of typical point of the flame tube.The results show that the acoustic-structural coupling and temperature load have a great influence on the acoustic fatigue life of the flame tube.The studying of the random vibration of the thin wall structure of the flame tube is of great engineering significance.The fatigue life of the structure can be estimated according to the stress spectral density of different points.