On Effects of Baffle Plate Insertion on Acoustic Natural Frequency of Duct in Boiler Tube Banks

概要

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In heat exchangers such as a boiler and a gas heater, the tube bank is set up in a duct. When the frequency of Karman vortex generated behind tubes becomes close to the natural frequency of the duct, the self-sustained tone is generated. As countermeasures of self-sustained tone, the absorbent is used on the duct wall in order to give an acoustic damping and the dense tube array is adopted not to generate vortexes strongly. As another countermeasure the insertion against baffle plates is often used. The suppression mechanism of this insertion of baffle plates has been considered that the natural frequency of the duct increases and the resonance is avoided. However the natural frequency of the duct does not increase but decrease a little by inserting baffle plates. That is to say, the effect of inserting baffle plates on the natural frequency of the duct has not been clarified yet. Then, the aim of this paper is to clarify the effect of the insertion of baffle plates on the natural frequency of the duct by carrying out the experiment and the FEM analysis.
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