目前在水稻的机械追肥作业中以离心圆盘式撒肥机为主,该方式在作业幅宽方向上的撒施均匀性不稳定,且难以实现作业幅宽方向上的变量施肥。为了满足水稻变量追肥作业的需要,达到化肥减施增收的目的,设计了一种外槽轮式排肥、以空气流为肥料输送和撒播动力的稻田气力式变量施肥机。文章对该机器的关键部件进行了仿真和测试试验,研究了排肥轮转速与排肥量之间的相关关系,并对排肥管道长度对排肥出口风速与排肥滞后时间的影响、排肥管出口相对高差对排肥滞后时间的影响进行了试验。试验结果表明:排肥轮转速与排肥量之间存在极显著的线性相关关系,相关系数R2=0.998,调节排肥轮转速可以较精确的调节施肥量的大小,在变量作业时,结合施肥量的需求及施肥机具的前进速度,对排肥轮的转速进行实时调节,从而达到变量施肥的目的。当机具前进速度为1 m/s,排肥轮转速在10～40 r/min之间变化时,单凭转速调节可实现每公顷施肥量在40～200 kg范围内的变量调节,此外,各排肥口的排肥量误差小于±5%,基本上达到了施肥均匀性的要求。文章还研究了排肥管道长度及安装高差对排肥滞后时间的影响,结果表明:排肥管道长度对排肥出口风速有显著影响,排肥管长度和出口安装的高差对排肥滞后性亦有显著的影响,因此,为了尽可能减小因排肥滞后对排肥均匀性的影响,应避免排肥管过长,并尽量使排肥管出口不高于入口。该研究为进一步的样机制造和优化提供了依据。

Variable?rate fertilizer applicator is one of the most important machines of precision agriculture.Nowadays, the main machine for topdressing in rice is centrifugal disc distributor, and this machine has a better width, but has an unstable spread uniformity at the direction of working width, and most of them also cannot fertilize with a variable rate at the working width direction.In order to satisfy the needs of variable?rate fertilizer application in rice, and use less fertilizer to produce more yield, a pneumatic variable?rate fertilizer applicator for rice production, which used outer groove?fertilizer?wheel and pneumatic fertilizer spreader, was designed.Firstly, the simulation of the key components of the variable?rate fertilizer applicator was carried out to optimize the structure of the mixed joint and the air divider box under the following initial boundary conditions: the inlet gas velocity was 12 m/s, the inlet gas volumetric flow of air divider box was 0.03 m3/h, and all the testing components were under the same pressure in outlet and environment.The results indicated that the small keyhole structure not only improved the average pressure in air divider box and the uniformity of airflow dividing, but also promoted the fertilizer falling for mixed joint of air and fertilizer.Secondly, a series of testing experiments of the key components of the variable?rate fertilizer applicator were carried out to investigate the correlation between the rotating speed of fertilization wheel and the amount of fertilizer application under the following conditions: use the mixed joint with small keyhole structure, the inlet gas velocity was 12 m/s and the air divider box pressure was 110 kPa.The results showed that there was a significant linear relationship between the rotating speed of fertilization wheel and the amount of fertilization, and the correlation coefficient was up to 0.998.Adjusting the rotating speed of fertilization wheel could accurately adjust the amount of fertilization.In other words, it could achieve the purpose of variable fertilization by real?time control the rotating speed of fertilization wheel combined with the fertilization demand and the forward speed of fertilizing machine.The variable amount of fertilization could be reached in the range of 40-200 kg per hectare when the forward speed of fertilizing machine was 1 m/s and the rotating speed of fertilization wheel was in the range of 10-40 r/min.And the errors of fertilizer application amount for each fertilizer ejector′s outlet was less than ±5%, which basically reached the requirements of fertilization uniformity.Finally, the impacts of the fertilizer pipeline length and installation height difference on the fertilization outlet velocity and lag time were studied when the inlet gas velocity was 12 m/s and the air divider box pressure was 110 kPa.The results showed that the fertilizer pipeline length and installation height difference had a significant effect on the fertilizer ejector′s outlet velocity and fertilization lag time.Therefore, in order to minimize the influence of fertilization lag time on fertilization uniformity, the fertilizer pipeline length should not be too long, and it is also suggested that the fertilizer ejector′s outlet is not higher than the inlet in order to reduce the impact of installation height difference.This study provides a basis for further prototyping and optimization of the pneumatic variable?rate fertilizer applicator.

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“十二五”国家“863”计划项目(2012AA101901-3)