PWM变量喷雾系统动态雾滴分布均匀性实验

由于PWM变量喷雾作业过程中喷头不连续作业,喷雾的均匀性特别是喷雾机运动方向上的均匀性较难控制,为此通过高速电磁阀、不锈钢压力罐、压力传感器、气泵、调速输送带等构建了一套动态PWM变量喷雾实验平台,并对该平台动态喷雾雾滴分布特性进行实验研究。采用水敏试纸作为获取动态雾滴分布状态手段,通过图像处理技术以区域内雾滴覆盖率的变异系数作为动态雾滴分布均匀性判定指标,评估了在不同PWM控制信号频率、不同PWM控制信号占空比及不同喷雾压力下的单个喷头动态雾滴分布均匀程度。经实验表明,变异系数随控制信号占空比的增大而减小,控制信号频率对动态喷雾雾滴分布均匀性有较大影响,变异系数随控制信号频率增大而减小,喷雾压力对变异系数影响较小,喷雾压力越大变异系数越大。

Experiment on Dynamic Droplet Distribution Uniformity for PWM Variable Spray System

A dynamic PWM variable spray experiment platform was built up to solve the problems of discontinuous operation of nozzles in spray progress, and improve the homogeneity of droplets, especially homogeneity along the travel direction. This platform included high-speed solenoid valve, a stainless steel pressure tank, a pressure sensor, an air pump, a conveyor and so on. The distribution features of droplets in dynamic spray based on this platform was studied. Water sensitive paper was used to collect droplets under different frequencies and different duty cycles of PWM controlling signals, also different pressures of spray. Image processing technology was used to get the coefficient of variation (CV) value of percent area droplets coverage to evaluate the uniformity of droplets. The homogeneity of single nozzle dynamic spraying was evaluated under different experiment conditions. The research suggested that CV value decreased as the duty cycle of controlling signals increased, the frequency of controlling signals had influence on homogeneity, which was CV value decreased as the frequency increased. And what is more, when pressure became high, CV value became larger and the influence was weaker compared to the other factors.