固定管道式常温烟雾系统雾滴沉积仿真与试验

Simulation and Test on Droplet Distribution and Deposition of Fixed-pipe Cold Fogging System in Greenhouse

为了进一步研究固定管道式常温烟雾系统的风场分布特性和雾滴沉积分布特性,基于计算流体力学(CFD)非稳态模拟,通过建立固定管道式常温烟雾系统在温室内作业的气流速度场仿真模型及雾滴沉积分布仿真模型,分析了该系统在3组作业参数(液压为0.05MPa,气压为0.2、0.3、0.4 MPa,3组作业参数分别对应的喷头出口截面平均气流速度为200、400、600 m/s)下的气流速度分布特征及在3组作业参数、4组高度水平(0、40、60、80 cm)和2个雾滴沉积区域(喷头正下方区域和喷头中间区域)下的常温烟雾系统的雾滴沉积分布特性,并对雾滴沉积分布特性进行了试验验证。研究结果表明:固定管道式常温烟雾系统作业时可在棚室内形成涡旋气流,有益于雾滴在整个棚室内的漂浮、弥散和沉积,根据仿真和试验结果得出本系统的最优作业参数为气压0.3 MPa、液压0.05 MPa。喷头正下方和喷头中间区域的雾滴最大沉积量分布在喷头喷射方向前方1 m区域(采样点5),且沿喷头喷射方向呈逐渐降低趋势。相同试验条件下,雾滴沉积量随着气流速度的增加呈降低趋势。喷头正下方的雾滴地面沉积量低于中间区域的雾滴地面沉积量,而在高度水平40、60、80 cm下,喷头正下方相应的雾滴沉积量高于中间区域。正下方区域的雾滴主要沉积分布在60~80 cm的高度区间,中间区域的雾滴主要沉积分布在高度40、80 cm区域。不同作业参数下雾滴在不同高度的仿真和实测沉积量相关系数范围为0.990~0.924。雾滴沉积量仿真值和实测值的相对误差范围为0.008~0.374,说明CFD仿真可较准确地预测模拟常温烟雾系统气流速度场与雾滴沉积分布特性,指导实际作业参数优化。

Based on CFD unsteady simulation,the airflow velocity field and droplet deposition model of the fixed-pipe cold fogging system in greenhouse were established,and the airflow velocity and droplet deposition characteristics of the fogging system under different operating parameters were analyzed.At the same time,the experimental verification of the droplet deposition characteristics was implemented.Results showed that the fogging system formed vortex flows in greenhouse,which was beneficial to the floating,dispersion and deposition of droplets.The optimal operating parameter of the system was 0.3 MPa with air pressure and 0.05 MPa with hydraulic pressure.The maximum deposition amount of droplets directly below the nozzle and between the nozzles was distributed in the area of 1m in front of the nozzle spray direction(sampling point 5),decreasing along the nozzle spray direction.The amount of ground droplets deposited directly below the nozzle was lower than that in the middle area,while at the height of 40 cm,60 cm and 80 cm,the corresponding amount of droplet deposition directly below the nozzle was higher than that in the middle area.The droplets in the area directly below were mainly deposited in the height range of 60~80 cm,and the droplets in the middle area were mainly distributed in the height area of 40 cm and 80 cm.The correlation coefficients of the simulated and measured droplet deposition amount at different heights under different operating parameters were ranged from 0.990 to 0.924.The relative error range between the simulated and measured droplet deposition amount was 0.008~0.374,indicating that the CFD simulation can accurately predict the airflow velocity field and droplet deposition characteristics of the fogging system,and guide its operating parameters optimization.