- 期刊
- OpenAccess
落花生及玉米氣體動力特性之研究
The Study on Aerodynamic Properties for Peanuts and Corns
摘要
本實驗利用垂直式風洞以浮力法試驗，使用變頻器控制風量(0.16～0.48m^3/s)。截取風洞中心部份均流區爲試驗區，如此樣品之水平位移，將不影響終端速度量測，利用浮力法進行試驗，當樣品在靜止飄浮狀態時，利用風速計量取的風速，即爲終端速度。在非靜止狀態時，所量取的資料包括：(1)樣品對地下墜速度V，(2)向上垂直風速V(下标 v)，而終端速度為V+V(下标 v)。 本研究除以球驗證系統外，另以玉米進行試驗，所得結果與國外已發表資料相比較，數值相接近。以兩仁落花生莢爲樣品，使用面積計與體積計(Pycnometer)量取樣品的幾何因子資料，並與實驗之氣體動力特性資料進行迴歸分析，求得玉米與落花生氣體動力特性與幾何特性間之相關性。迴歸公式將可用來預測樣品之終端速度。 以玉米與落花生爲對象，針對五種不同的幾何因子（重量、密度、兩種形狀因子、幾何平均粒徑）與終端速度及明顯曳力係數作相關性比較與分析，結果顯示以密度與H.Song所定義的形狀因子對終端速度影響較大，對C(下标 D)影響則較不明顯，但仍以密度與形狀因子較具影響性且相關性較佳。
並列摘要
The study applied the constructed vertical wind tunnel to terminal velocity measurements for agricultural products. The electrical frequency inverter was used to control air flow rate from 0.16 to 0.48m^3/s. The floating method was adopted in this study. The central core inside the tunnel, of which velocity profile was uniform, was used to be the effective testing zone. It is unnecessary to concern the horizontal displacement. If a sample is moving in the stable state, the terminal velocity is the sum of wind upward velocity and sample velocity to the ground. In other words, the terminal velocity is the relative velocity between sample and air. The data were taken by measuring air velocity, as the sample was in the stable still state. The spherical samples were used to calibrate the system. In addition, corn kernels were tested to compare with the published data in order to further validate the system and experimental procedures. The results of corn kernels were closed to the known values. Two-kernel peanut pods were tested in this work only. The areameter and pycnometer were applied to determining geometrical data of samples. The relationship between geometrical data and aerodynamic properties were analyzed in statistics. The best fitted linear mathematical model between them was computed. The derived equations can be used to estimate terminal velocity and drag coefficient from geometrical data, especially shape factor. Five geometrical parameters (weight, density, two shape factors, and geometrical mean diameter) were correlated to terminal velocities and apparent drag coefficients. The relationships among geometrical parameters and aerodynamic properties were determined for peanuts and corn kernels. The density and Song's shape factor influence terminal velocity more significantly than the others. There are less influence on drag coefficient than terminal velocity from geometrical properties. But the density and Song's shape factor are still more influential than the others.