基于茶园防霜风机的气流扰动与温度变化研究

Research on 3Dwind field and temperature variation based on tea antifrost fan

为研究风机作用下的三维流场和温度场，利用计算动力学方法进行数值计算，分析气流扰动特性以及温度变化特征。计算结果表明：风机出口气流的角速度在xyz方向的分量比例为定值，不随角速度的增加而改变；转速增加到某个临界值时，会在三维流场空间中出现一个直径约为4～6m，单边宽度约为1．5m的近似三角形的螺旋涡，其旋涡中心的气流速度随转速的增加而增大，但旋涡中心与风机的距离并没有明显的增加；在距离地面1．2m茶树冠层处，受蒸发和辐射的影响，温度升高最大的区域与风速最大区域有一定的偏差；以平均法在温度最大区域计算选取监测点A，而当转速达到1150r／min时，监测点A温升达到最高值；通过分析空间的流线变化，计算出本风机的最佳安放角在35．5°左右。

In order to study the three dimensional flow field and temperature variation under the action of fan, numerical calculated by computational dynamics, then analyzing the characteristics of airflow disturbance and the characteristics of temperature variation. The calculation results show that fan outlet airflow velocity in the direction of the xyz component proportion is a fixed value, and remains unchanged with the increase of the angular velocity. When rotation speed increases to a certain threshold, will appear a diameter of about 4-6 and unilateral width about 1.5 m of approximate triangular spiral vortex in the three dimensional flow field space. The vortex flow is proportion to the increasing of fan＇s speed, however, the axis distance increase from the center of fan＇s rotation to the center of the vortex position isn＇t obvious. At the distance of 1.2m from the ground to tea canopy,the largest temperature zone with the maximum wind speed area has a certain deviation due to evaporation and radiation. Selecting a monitoring point A in temperature area by averaged method, when the rotating speed up to 1 150 r/min, the monitor temperature increases to peak, and the best installing angle of the fan model is 35.5° by calculation.