The FDC (Flow Dynamics Conveyer) has often been used in power plants and iron works because of its superiority in quietness compared with a roller type conveyer. Moreover, it is excellent in low noise and low power. The FDC consists of a trough and a belt, and the air is supplied from numerous holes provided on the trough. However, large vibrations occur when the flow rate reaches a certain value. This abnormal vibration is defined to be a self-excited vibration caused by leakage flow. It is well known that abnormal vibrations occur when the flow channel spreads out at the edges. The purpose of this study is to clarify the generation mechanism of the abnormal vibration. The experimental setup is made of steel. The trough is made of a thick plate and the belt is made of a thin plate with a thickness of 1.2mm. The air is supplied by a blower and the flow rate is adjusted by a ball valve. The flow rate is measured by a venturi tube and a liquid manometer. The loads are given by piling thick steels one by one with a weight of 1kg. The vibration of the belt center is measured by a laser displacement meter and the data are processed by a FFT analyzer. The experiment was carried out to examine the effects of various parameters such as the taper angle θ, the floating amount H generated by loads and flow rates on abnormal vibrations. Firstly, vibrations of the belt were obtained by changing loads and flow rates. When the flow rate is constant, the taper angle θ increases and the floating height of the belt H decreases with increasing loads. The area of abnormal vibrations could be obtained in the θ—H plane. Secondarily, the damping coefficients were obtained based on the free vibration method by changing loads and flow rates when abnormal vibrations did not occur. As a result, it was found that the damping ability decreases with an increase in the taper angle and a decrease in the floating height. Furthermore it was clarified that the abnormal vibrations occur for θ > αH (α: constant value).
Study on Generation Mechanisms of Abnormal Vibrations of Flow Dynamic Conveyers
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Ishihara, K. "Study on Generation Mechanisms of Abnormal Vibrations of Flow Dynamic Conveyers." Proceedings of the ASME 2011 Pressure Vessels and Piping Conference. Volume 4: Fluid-Structure Interaction. Baltimore, Maryland, USA. July 17–21, 2011. pp. 175-185. ASME. https://doi.org/10.1115/PVP2011-57227
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