以物理實驗探討筒倉鳴音的現象

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题名:	以物理實驗探討筒倉鳴音的現象
作者:	李庭瑋;Lee, Ting-Wei
贡献者:	機械工程學系
关键词:	顆粒材料;筒倉模態實驗;筒倉卸載實驗;筒倉鳴音;筒倉振動;筒倉動態分析;granular materials;silo model experiment;silo discharge experiment;silo honking;silo quake;dynamic characteristics
日期:	2021-08-10
上传时间:	2021-12-07 13:27:55 (UTC+8)
出版者:	國立中央大學
摘要:	本研究探討筒倉顆粒體卸載過程中筒倉鳴音的現象與成因，筒倉鳴音為具有特定頻率的低頻噪音，並在卸載過程中伴隨特徵頻率的振動，稱為筒倉振動。為了重現筒倉鳴音的現象，筒倉系統由上部的筒倉與下部的剛性支撐組成，並利用筒倉底部的出口控制質量流率，實驗用設備包含為直徑101.6mm、152.4mm與216.3mm的不鏽鋼筒倉以及直徑200mm的壓克力筒倉，且筒倉高度均為2m，出口直徑分別為40mm、60mm、80mm與120mm，顆粒體分別為內含硫酸鋇的聚氯乙烯顆粒、內含耐衝擊聚苯乙烯樹脂的聚氯乙烯顆粒以及氧化鋁顆粒，採用三軸加速度計與麥克風量測筒倉壁面上的振動加速度與筒倉附近的聲壓，並對時域訊號的結果進行頻率與相位分析，此外為了釐清筒倉鳴音與共振現象的關聯性，對筒倉系統進行實驗模態分析，研究結果顯示：(1)筒倉振動造成筒倉鳴音的現象，兩者具有一致的特徵頻率；(2)共振現象並非筒倉振動的主因，但可能放大筒倉振動的現象；(3)筒倉振動可能為顆粒體與筒倉壁面間接觸的作用力(摩擦力與徑向力的合力)所致，黏滑效應是由顆粒體與筒倉壁面間的靜動摩擦力的轉換所致；(4)筒倉軸向加速度為正弦波，而徑向加速度與聲壓均為脈衝波，應該是筒倉的徑向振動推擠空氣產生筒倉鳴音的現象； (5)控制出口直徑即可有效地改變筒倉振動的強度與持續時間；(6)在筒倉底部安裝的置入物對筒倉鳴音較無影響。;The purpose of this study is to investigate the phenomenon and causes of silo honking during silo discharging. The silo honking is a low-frequency noise with specific frequency, and it is always accompanied by vibration of characteristic frequency during silo discharging, called silo quake. In order to reproduce the phenomenon of silo honking, the experimental system is composed of an upper silo with various silo diameters and different orifices as well as a lower rigid supporting platform. The silos studied here include stainless steel silos with diameters of 101.6mm, 152.4mm, and 216.3mm, and an acrylic silo with a diameter of 200mm. These silos have a height of 2m. The orifice diameters are 40mm, 60mm, 80mm and 120mm respectively. The granular materials used in the study include two kinds of PVC particles and Al2O3 particles. The three-directional accelerations on silo walls and the sound pressure near the silo were measured using four accelerometers and one microphone, and the frequency and phase of the signals were further analyzed. In order to clarify the relation between silo honking and structural resonance, the experimental modal analysis was also performed. Key findings are highlighted below: (1) Silo quake is responsible for silo honking, both have the same characteristic frequency; (2) Structural resonance is not the main cause of silo quake, but it may amplify the phenomenon of silo quake; (3) The resultant force (friction force and radial force) which the particles exert on silo walls may be the cause of the silo quake; (4) The axial vibration is in the form of sinusoidal wave, while the radial vibration and the sound pressure exist in the form of pulse. The radial vibration of the silo leads to the sound generation, called silo honking; (5) The orifice diameter influences the intensity of silo quake and its duration. (6) The inserts installed on the silo bottom have no effect on the silo honking.
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