超音波懸浮泥沙溶液濃度及流速量測:以高嶺土及水庫土樣為實驗驗證之研究

Abstract

懸浮顆粒溶液系統被廣泛地使用在水文學，生物，化學，以及食品工業等。而超音波量測是一種快速、非侵入和即時線上作業的測量技術，可對大範圍的濃度及懸浮顆粒的粒徑系統達成特性描述。本篇文章提提出了一種國人自製，經由聲波訊號在液體中發射、傳遞、接收的過程，可以同時量測溶液濃度及水流速度的新式的量測系統。我們在實驗室中進行了一系列高嶺土及石門水庫庫底土樣，在大的濃度範圍 (0 ~ 300,000ppm)和不同的溫度(5~ 25˚C)下的超音波衰減特性量測。結果顯示，濃度、顆粒的粒徑和溫度為衰減的變化為主要的影響因素。根據這些實驗的校準數據資料庫，我們建立了兩種土樣的溫度、衰減和濃度的資料庫，可以提供未來量測使用。 這篇論文的目標在於全部由國人設計並製造一套能在高濃度範圍下，量測濃度及水流速度的量測系統。其中包含了設計並製造超音波發射接收的探頭以、系統電路以及資料儲存等部份，而且能符合台灣特殊的水文環境條件。最後完成了能在水下100公尺執行量測任務的攜帶浸水式系統，和能抽取不同水下深度水樣的固定式量測系統。 利用螺槳式流速計和傳統的抽取烘乾方式，分別用來驗證量測系統的準確性。經過驗證後，在濃度量測及水流流速量測功能上，個別的誤差值分別都在5%和2%之內。我們用固定式和攜帶浸水式的超音波的量測系統，在幾個颱風期間，成功的用來即時監控石門水庫庫區內水中的泥沙濃度及水流速度。

Multiphase suspension systems are extensively used in hydrology, biochemistry, and the food industry. Ultrasonic spectroscopy is a rapid, on-line, non-invasive measurement technique for suspension characterization of different particle sizes and wide-ranging concentrations. This study presents the design and fabrication of a novel experimental system to simultaneously measure the sediment concentration and flow velocity of ultrasound wave propagation in liquid at different temperatures. Experimental validation in a laboratory environment provides a series of measurement results for kaolin ultrasonic attenuation under a wide range of concentration (0 ~ 300,000ppm) and various temperatures (5 ~ 25oC). This study also investigates the ultrasonic attenuation measurement of sediment sampled from the Shihmen reservoir in Taiwan. Results show that ultrasonic attenuation variations are driven by concentration, particle size, and temperature. The established regressed functions quantitatively convert the attenuation to kaolin concentration and the Shihmen reservoir sample with given temperature which is used for system calculation. The purpose of this study is to design and manufacture a real-time monitoring system for measuring flow velocity and concentration under a wide concentration range. This includes designing and manufacturing an ultrasonic transducer, electric transmit and receive circuit, and data log which are suitable for the special environmental conditions of Taiwan. The proposed system successfully integrates these components into a portable unit which can operate under water up to 100 meters deep and a fixed chamber unit which is able to draw water from various depths. We verify the function of flowmeter via propeller type flowmeter and verify the function of concentration via extractive methods. These experiments demonstrate that the total error of full scale concentration and the error of the flowmeter are 5% and 2%, respectively. The fixed chamber type and portable type ultrasonic measurement system took successful measurements in the Shihmen reservoir during several typhoons.