Exhaust stack silencer design using finite element analysis

Abstract

Classical analytical models used for prediction of the performance of reactive silencers are limited to conditions where the dimensions of the duct and resonators are small compared to the wavelength of the sound. Finite Element Analysis (FEA) does not suffer from such limitations and has therefore been used to analyze the design of a reactive silencer for the exhaust stack of a 980 MW power station. To assist in the design process, resonators of various dimensions were analyzed using FEA which has led to the derivation of expressions for the resonant frequencies of slot-type rhomboid shaped resonators as a function of the geometry. An important design issue is the influence that adjacent resonators have on the overall performance of the system. It was found that when resonators of similar resonant frequency are in close proximity, they can interact and lead to a decrease in the overall performance compared to that of a single resonator.