Acoustic Resonance and Vortex Shedding from Tube Banks of Boiler Plant

Abstract

In the present paper the attention is focused on the relation between acoustic resonance and vortex shedding from tube banks in boiler plant. We have built a similar model of actual boiler plant to clarify the characteristic of acoustic resonant phenomena and vortex shedding. The model includes tube banks with in-line arrangement with a small tube pitch ratio. The relation between the acoustic resonance of actual plant and that of the similar model was examined. We measured the sound pressure level, the mode shape of acoustic pressures, the spectrum of velocity fluctuation and the gap velocity. As a result, the resonant frequencies and the mode shapes of acoustic resonances in actual boiler plant agreed well with those of the similar model. We found many peak frequencies in the spectrum of sound pressure level when the acoustic resonances occurred. The typical Strouhal numbers at onset velocity of acoustic resonances were about 0.19, 0.26 and 0.52. The periodic velocity fluctuation caused by the vortex shedding was remarkably observed inside of tube banks without acoustic resonance. The measured Strouhal number of vortex shedding became 0.15. The acoustic resonances of higher order modes were generated in this plant.