Abstract
A boiler and a heat exchanger are widely used in various plants such as power plants and chemical plants. However unexpected high level sounds are generated when these plants are operated and it becomes a serious problem. This kind of problem is called the acoustic resonance and it has been considered that the resonance generates when the frequency of the vortex shedding behind the tube bank coincides the natural frequency of the duct system. However it has also been thought of self-sustained tone. In general, the self excited phenomenon arises when the exciting energy becomes greater than the dissipating energy. Then in this paper, in order to clarify the mechanism of self sustained tone experimentally, the instability region is tried to obtained by varying the number of tube row and acoustic damping. As a result, it was clarified that the self-sustained tone generates when the number of tube rows is large and the acoustic damping is small.
