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| 題 名 | 落花生終端速度之測定 |
|---|---|
| 作 者 | 盛中德; 謝廣文; | 書刊名 | 農業工程學報 |
| 卷 期 | 37:2 1991.06[民80.06] |
| 頁 次 | 頁48-58 |
| 分類號 | 434.251 |
| 關鍵詞 | 終端; 速度; 落花生; |
| 語 文 | 中文(Chinese) |
| 中文摘要 | 農產品氣體動力特性之研究,浮力法已取代自由落體法。浮力法之主要利用風洞進行試驗,量取物品與空氣的最終相對速度,即為終端速度。為進行氣體動力特性(終端速度)之量測試驗,本研究將規劃研製一垂直式風洞,所製之垂直式風洞利用變頻器控制風機之送風量0.16~0.48 m³/s,在5 m/s~15 m/s的平均風速內控制效能良好,此範圍適合一般農產品的氣體力特性研究用。利用相機重覆曝光方式攝取測試物品的水平與垂直位移,水平位移將用來檢視樣品是否在有效的均流區內,垂直位移將用來估算其速度,並計算終端速度,試驗所採用之風速略小於終端速度,如此所攝得之影像易於辦識。 以球型物品為樣品進行系統校正,所得之曳力係數介於0.452~0.461之間,與理論值0.44極為接近,由此說明此系統可用於農產品的終端速度量測上。以二仁落花生莢為樣品量測終端速度,所得之明顯曳力係數介於0.51~0.67之間,平均值為0.60,標準誤差0.065,平均值介於球形(C□=0.44)與無限長圓柱體(C□=1.2)的理論值之間,以幾何形狀判斷應為合理。 |
| 英文摘要 | The floating method has released the free body falling method for measurements of aerodynamic properties of agricultural products. The floating method utilities the wind tunnel to test the sample. The final steady relative velocity between the air and sample is the terminal velocity. For conducting the measurement of terminal velocity, a vertical wind tunnel was designed and constructed. The frequency inverter was used to control the airflow rate from the range of 0.16-0.48 m³/s. According to the applied flow rate, the air velocity was controlled very well within the range of 5-15m-s, which can be used to measure the terminal velocities for most agricultural products. The horizontal and vertical displacements of a sample in a test were recorded with a camera in a multiexposure manner. The horizontal displacement was used to check if the sample was in the uniform air velocity range or not. The vertical displacement was used to estimate the sample velocity corresponding to the ground. It can be used to calculate the terminal velocity between the sample and air inside the wind tunnel. The applied air velocity in a test was slightly less than the terminal velocity; therefore, the different images could be justified clearly and easily. Four balls with different sizes were applied to calibrate the system. The calculated apparent drag coefficients of 0.452-0.461 from the measured terminal velocities are very closed to the theoretical value of 0.44. It indicated that the constructed system could be used to determine the terminal velocities of agricultural products with experiments. The peanut pods with two kernels were selected to test. The values of apparent drag coefficient of peanuts were within the range from 0.51 to 0.67. The average value of Cdapp of peanut pods was 0.60, and the standard error was 0.065. The theoretical drag coefficient value of a infinite cylinder is 0.2. Considering the shape of peanut pod, it is reasonable that the average value of peanut pods was located between the theoretical values of drag coefficients of a sphere and an infinite cylinder. |
本系統中英文摘要資訊取自各篇刊載內容。