水流推動物體旋轉發電之研究

Abstract

本實驗主要探討矩形流道中水流過可自由旋轉的物體時產生的動能轉換成電能的可行性。旋轉物體有對稱轉子及不對稱轉子兩種，分別是空心圓柱轉子及Savonius 轉子。當水流過不對稱通道時，會因為轉子左右兩邊不一樣的應力作用而開始旋轉並帶動發電機同步旋轉進行發電。轉子皆放置在三組測試段流道截面寬15公分及高12公分的位置，三組測試段為平行直板流道、擴張角度15度及30度流道。其中，水流速度從每秒0.2公尺到0.8公尺。實驗參數包含水流速度、轉子在流道中的位置、轉子的尺寸、流道擴張角度等。實驗中將改變以上參數去探討動能轉換成電能的效率之改變。 實驗結果顯示，空心圓柱體放置在不對稱流道中，由於水流過不對稱流道所產生的應力不足以讓空心圓柱體進行轉動，故無法產生電力。而Savonius轉子放置越接近直板壁面且擴張角度大的流道中，其發電量越好。此外，較小且較輕的Savonius轉子放置在擴張角度大的流道中，效率越好。本實驗最大效率為0.43。

In this study an experiment is conducted to explore the feasibility of extracting kinetic energy in a rectangular-channel flow of water by installing a freely rotatable object in the flow. Both axisymmetric and asymmetric objects are tested. The rotation of the object results from imbalance drags over the left and right parts of the object surface by the water flow. Here a circular cylinder and a Savonius turbine are chosen in particular. The object rotation is then used to drive a power generator. A small-scale laboratory experimental system is established to test this concept. The channel width and depth are respectively 15 cm and 12 cm and the mean water speed is varied from 0.2 to 0.8 m/s. To augment the object rotation, the cylinder and turbine are placed in a diverging section of the channel with a side wall of the channel inclined outward at angle of 15 and 30 . The experimental parameters include the water speed, location of object, rotor size, and diverging angle of the channel wall along with the turbine configuration. The measured data for the efficiency of the power generation from the hydrokinetic energy affected by the experimental parameters are examined in detail. The results show that installing a circular cylinder in the channel does not produce enough imbalance drags over the cylinder surface to cause it to rotate over the ranges of the parameters covered here. The data for the Savonius turbine, however, exhibit a better outcome. Specifically, the power output from the Savonius rotor is higher when it is installed at a location closer to the straight side wall of the channel especially in a larger inclination angle of the side wall in the test section. Besides, a lighter and smaller Savonius installed in a highly diverging test section gives a better power performance. The best power efficiency is 0.43 in this study.