籽棉团悬浮速度的理论算法与试验验证

针对常规悬浮速度理论值与测试值偏差大的问题，该研究以常规悬浮速度理论为基础，通过量纲分析法和力平衡原理，建立籽棉团物理属性与阻力系数之间的关系，提出一种轻软可压缩颗粒悬浮速度理论模型。在棉田测试单颗棉桃完全开裂时所含籽棉团直径，确定气力输棉管道最小直径，并通过管流雷诺数和绕流雷诺数计算确定阻力系数。用体积法测试籽棉团密度，用等密变径法制备6种不同密度、18种不同直径的球形籽棉团试样并进行悬浮速度试验测试。结果表明，单颗棉桃全开裂时直径变化范围在38～54 mm之间，此范围内管流和绕流雷诺数都大于500，阻力系数为0.44；籽棉团松散密度范围为20～90 kg/m³，半压实密度范围为90～220 kg/m³；籽棉团悬浮速度测试值从直径比(籽棉团直径与管道直径之比)大于0.6开始与常规悬浮速度理论值偏离，直径比等于1时籽棉团悬浮速度测试值不等于0。采用该研究提出的理论算法时，得到的籽棉团悬浮速度分布特征和大小与测试结果基本吻合，平均相对误差为4.6%，并通过方差分析验证了该研究提出的理论算法的有效性。这为籽棉、羊毛和驼绒等轻软可压缩物料的气力输送...

Theoretical algorithm and experimental verification of seed cotton ball suspension velocity

Abstract: In order to solve the problem of the deviation between the conventional theoretical results and the experimental results of the suspension velocity of LASC (Light And Soft Compressible) seed cotton ball, the relationship between the physical properties of LASC seed cotton ball and the resistance coefficient was established by using the DAM (Dimensional Analysis Method) and the FBP (Force Balance Principle), then the theoretical model and calculation method of LASC seed cotton ball suspension velocity was proposed based on the conventional particle suspension velocity theory. Then, the diameter of LASC seed cotton ball contained in a single cotton peach when it was completely cracked were tested in the cotton field, and the minimum diameter of pneumatic cotton conveying pipeline was determined, and the drag coefficient was determined by calculating and analyzing the Reynolds number of pipe flow and around flow. Spherical LASC seed cotton ball with different density and diameter were prepared by using EDCD (Equal Density Change Diameter) method and the suspension velocity was tested. When the LASC seed cotton balls were just in completely suspended and stable at the middle of the glass tube on the test platform, then the suspension speed of the LASC seed cotton balls were calculated according to the relationship between the frequency recorded by the frequency modulator and the inlet wind speed. When a single cotton peach is fully cracked, the value range of the diameter of the seed cotton ball were between 38 mm and 54 mm, and the loose density were between 21 kg/m3 and 35 kg/m3. Thus, the average diameter of the seed cotton ball and the minimum diameter of the cotton conveying pipe were determined to be 50 mm. Due to these minimum diameters, the pipe flow and the around flow Reynolds number were calculated, and the results shown that the both pipe flow and the around flow Reynolds number meet the conditions of 500