Numerical Simulation And Experiment Investigation Of Thermal-acoustic-structural Coupling In Combustion Chamber

To decrease emission of NOx,lean premixed combustor is applied for gas turbine.However,this type of combustion suffers from a high sensitivity to thermal-acoustic instabilities which may occur in a combustion chamber of a gas turbine.Pressure fluctuations induced by instabilities may be very violent.This level of acoustic excitation is hazardous to the combustion chamber walls called liner.The situation is even worse when frequency between thermos-acoustic instabilities and liner vibration is approximate.Both processes enhance each other up to the moment when the pressure saturation limit is obtained including the phenomenon of thermal-acoustic-structural coupling in the combustion chamber.This behaviour reduces the life time of the gas turbine significantly.Therefore,research on the thermal-acoustic-structural coupling of the combustion chamber has the vital significance.The basic theory about thermal-acoustic-structural coupling is studied firstly in this paper.Then the numerical simulation of coupling is finished using ANSYS Workbench which is applied for establishing numerical models of combustion chamber as one of the finite element analysis software.The impact of preheating temperature and inlet velocity on the numerical simulation is contrasted and analyzed with different grids used on model.The one-way and two-way couplings with experiment are used to analyze the thermal-acoustic-structural coupling characteristics.Finally,the structural modal experiment is carried out,and the frequency and vibration mode of the intrinsic mode and coupling modal on combustion chamber structure are compared with the results of numerical simulation for contrastive analysis.The comparison of experimental data and results of numerical simulation analysis shows that thermal load has an important influence on structural distortion,but this influence from acoustic pressure load could be ignored;The natural frequency of the structure under acoustic pressure load has a greater change only at a certain frequency;The natural frequency and mode of the structure change more obviously under the thermal load,especially in the high frequency range;The preheating temperature increases the flow field temperature,and decreases the flow field pressure;With the increase of inlet velocity,the temperature and pressure of the flow field are increased as a whole,and the variation law of the maximum deformation of the structure of the inlet velocity is basically consistent with the variation law the maximum temperature of the fluid;Compared to the one-way coupling,the two-way coupling calculation results are closer to the experimental values and the results of numericalsimulation are in good agreement with the experimental results;The results of numerical simulation have some reference value for engineering application.This paper has a lot of important reference value for improving stability and design of resistance to fatigue caused by thermal-acoustic-structural coupling in combustion chamber.