浮子流量計之流固耦合分析與參數化設計

Abstract

智慧化工業蓬勃發展，使現今流量計普遍整合智能感測系統，以達到快速生產與即時監控，其中浮子流量計擁有構造簡單、安裝便利、低壓力損失、價格相較其他款低廉且直管段要求低等優點，在化工、食品、能源、醫藥、水處理等產業被廣泛應用。在本研究從理論方程式出發，以因次分析的方式推導浮子流量計重要無因次參數，並利用計算流體力學軟體COMSOL，模擬浮子流量計不同浮子高度在測量管內的流場行為，分析浮子形狀對流量計靈敏度與量測範圍的影響。結果顯示，模擬值與文獻結果相比相對誤差小於5%，理論值與模擬值平均相對誤差為6.49%，且浮子形狀的改變對流量計的性能具有顯著影響，特徵角度為26.57度相比90度的浮子，阻力係數減少30-33%，使得靈敏度漸低30%，但測量範圍增加約41%，因此量測範圍與靈敏度之間的權衡(Trade-off)是設計重要的環節，並進一步得到阻力係數與浮子特徵角度關係函數。此外，提出了一種基於磁感應測量的浮子流量計設計，利用浮子內的磁鐵與外部磁感應旋轉系統，實現對浮子位置的測量，並透過流量測試實驗驗證了原型機與模擬的有效性。

The rapid development of smart industries has led to the widespread integration of intelligent sensing systems into modern flow meters to achieve quick production and real-time monitoring. Among these, the rotameter (variable area flow meter) is favored due to its simple structure, ease of installation, low pressure loss, relatively low cost, and minimal requirement for straight pipe lengths. It finds extensive application across industries. This work starts with theoretical equations and derives the dimensionless parameters of the rotameter using dimensional analysis. Computational fluid dynamics software, COMSOL, was utilized to simulate the flow field behavior within the measuring tube at different float heights. The impact of float shape on the sensitivity and measuring range of the rotameter was analyzed. The results indicate that the relative error between simulation and literature values is less than 5%, while the average relative error between theoretical and simulation values is 6.49%. The float shape significantly affects the performance of the flow meter; for instance, a float with a characteristic angle of 26.57° shows a sensitivity decrease of approximately 30% compared to one with an angle of 90°. However, the measuring range increases by about 41%. Hence, balancing the trade-off between measuring range and sensitivity is a critical design aspect. Additionally, a magnetically induced measurement design for the rotameter is proposed. This design uses magnets within the float and an external magnetic induction rotation system to measure the float position accurately. Experiments validated the effectiveness of the prototype and the simulations.