Abstract

This paper describes experimental investigations about the noise generation and the induced vibration of exhaust gas economizers. Various experiments on actual economizers and models have been carried out, and the following results are obtained.
In the economizer a resonance phenomenon of acoustic vibration is induced by vortex streets formed behind each circular tube in the gas stream.
Noise or vibration problems in economizers may be encountered in those instances when a natural acoustic frequency of the economizer in the direction normal to both the flow direction and tube length is close to the vortex shedding frequency which is mainly determined from the Strouhal number.
Therefore in a rectangular duct such as economizers, the acoustic mode of vibration is transverse across the width of the duct, and the acoustic vibration of the lowest frequency has a wave length equal to twice the duct width.
The use of properly spaced baffles between the tube rows at pressure nodes (velocity antinodes) eliminates the vibration almost perfectly.
Experiments simulated in a water circulating tank show that the Strouhal number is strongly affected by configurations of multiple tube arrangement. Moreover, several evidences that the vortex shedding from each tube should be definitely related to those from other tubes are obtained.