Numerical Simulation of Liner Vibrations in a Laboratory Combustion Chamber

Combustion chambers are one of the main parts of the power generation systems such as gas turbines and internal combustion engines and affect their efficiency and environmental pollutions. To reduce the high amount of the pollutions e.g. NOx, lean premixed combustion was introduced to be used instead of traditional non-premixed flames, however, this method has more tendency to become unstable. In fact, the thermal and acoustics interactions in the combustion chambers can amplify the acoustic waves and thereby produce noise and increase the vibration level of the liner. The continuation of large amplitude vibrations can lead to failure due to fatigue. Therefore, the vibration modeling of the liner is very important. In the present research, the vibration of a liner in a laboratory combustion chamber is investigated. First step to model the vibration of the liner is to extract its modal parameters in the cold and hot states. Finite element (FE) model updating is utilized to modify the initial FE model of the liner based on the experimental modal parameters. Then, using the computational fluid dynamics (CFD), the flow analysis is performed to obtain the pressure and velocity fluctuations during the analysis time. These data are then used to model the flame as a monopole acoustic source. To find the structural response of the liner due to this acoustic source, the transient analysis is performed. The results show the effectiveness of the updated FE model to predict the modal parameters and the vibration amplitude of the liner with acceptable accuracy.