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. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved.