为了实现背负式喷雾器的变量喷雾,该文采用频率为8 kHz、占空比可调的方波信号控制微型电动隔膜泵,通过改变隔膜泵直流电机导通和关断时间,实现了基于脉宽调制(pulse width modulation,PWM)技术的背负式喷雾器变量喷雾调节控制,并研究了此种变量控制系统的喷雾特性.结果表明:喷雾量随着占空比的增大而增大,但增大率逐渐减小,最小喷雾量为0.66 L/min,最大喷雾量为1.13 L/min.随着占空比的增大,喷雾量逐渐增大,雾量分布显著向两边区域分散,喷雾角也呈现平缓增大的趋势,最低值41.53°,最高值为61.78°.雾滴粒径随占空比的增大逐渐减小,但基本维持在100～135μm之间.雾滴速度随占空比的增大逐渐增大,喷雾速度场基本呈现由上而下逐渐减小的趋势,中间喷雾速度明显大于两边.随着占空比的变化,喷雾质量的变化仍在可采用的范围,该变量喷雾控制系统工作性能稳定可靠,可操作性好,与背负式喷雾器相兼容,能有效应用于农业生产.%In order to realize variable-rate spraying of knapsack sprayer, frequency of 8 kHz square wave and adjustable duty ratio were evaluated to control micro electric diaphragm pump. By changing the on and off time of DC Motor, the application rates of knapsack sprayer based on the PWM could be controlled, and the spray characteristics were analyzed also. Results showed that the volume of spraying increased with increasing of the duty ratio, but the rate of volume decreased gradually, and the maximum and minimum volumes of spraying were 1.13 and 0.66 L/min respectively. With the increase of duty ratio and spraying volume, spraying area spread to both sides and the spray angle increased gently, and the lowest and the highest value were 41.53° and 61.78° respectively. The diameter of spray droplets were between 100 and 135 μm, and decreased with increasing of duty ratio. The droplets velocity increased with increasing of the duty ratio, and the velocity in the middle was higher than that in both sides obviously. The variable-rate spraying control system is stable which can be effectively applied to agricultural production.
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