交错螺旋槽轮式小麦精量集排器设计与试验

    Design and experiment of the staggered helical groove wheel precision centralized wheat metering device

    • 摘要: 针对直槽轮式集排器脉动现象导致排量稳定性及排种均匀性较差的问题,该研究设计了一种交错螺旋槽轮式小麦集排器,通过交错分布结构使双螺旋槽轮供种周期相位互补,实现均匀排种。通过齿间种子受力及种群运动分析,确定螺旋角及交错角是影响排量稳定性及排种均匀性的关键参数。通过螺旋槽轮容种空间的划分及计算,确定集排器主要工作参数。以螺旋角及交错角为试验因素,运用离散元法进行双因素多水平组合仿真试验,以确定最佳性能参数组合。结果表明,螺旋角及交错角对排量稳定性及排种均匀性均有显著影响(P<0.05),排量稳定性变异系数及排种均匀性变异系数随螺旋角的增大呈先减小后增大趋势,随交错角的增大呈逐渐减小趋势。借助响应面分析,得出螺旋角为45°、交错角20°时排量稳定性及排种均匀性最优,变异系数分别为2.06%和7.29%。台架试验结果表明,集排器性能受作业速度影响较小,在作业速度8~10 km/h时,排量稳定性变异系数、排种均匀性变异系数及伤种率不高于2.23%、7.52%和0.056%,且相较于传统外槽轮式集排器,三者平均分别降低了10.14、4.5和0.093个百分点。该研究为槽轮式农业物料输送装置的作业稳定性、均匀性开发及改进提供了方法和理论依据。

       

      Abstract: Pneumatic centralized seed metering has been developing rapidly in China, due to its high precision, efficiency, and low seed damage. However, the traditional centralized wheat metering devices are often equipped with a straight groove wheel. Once the amount of the seed discharged is high, the groove wheel can rotate to the groove and low at the ridge, thus resulting in the pulsation during seeding. The discharge stability and uneven seed distribution can be caused by the pulsation of the straight groove wheel. This study aims to propose a precision centralized wheat metering device with a staggered helical groove wheel. According to the seed metering device with the outer groove wheel, the seed metering was optimized to eliminate the seed-feeding layer for the low inter-seed stress and seed damage. The helical structure was provided to enhance the uniform seeding. Two groove wheels with helical grooves were arranged in a staggered configuration. Among them, the two wheels were allowed to discharge the seeds in a complementary manner. The seed flows of the two groove wheels complemented each other, particularly for the phase complementarity of the seed supply cycle with the dual helical groove wheel. The pulsation was further reduced for the uniform seed discharge and stable seed rate. According to the seed stress between teeth and seed population motion, the helical angle and stagger angle were the key influencing parameters on the discharge stability and seeding uniformity. The working parameters of the centralized seed metering device were determined to calculate the seed-holding space of the helical groove wheels. A two-factor and multi-level simulation was conducted using the Discrete Element method (DEM), with the helical angle and stagger angle as the experimental factors, while the discharge stability and seed distribution uniformity as the evaluation indices. The optimal combination of the parameters was identified after optimization. The results showed that both the helical angle and stagger angle shared significant effects on the discharge stability and seed distribution uniformity (P <0.05). The coefficients of variation for both discharge stability and uniformity first decreased and then increased with the increasing helical angle, while they gradually decreased with the increasing stagger angle. The best performance was achieved when the helical and stagger angles were 45° and 20°, respectively, with the coefficients of variation of 2.06% and 7.29%, respectively. Bench test results showed that the performance of the centralized seed metering device was only slightly affected by the operating speed. The coefficients of variation for the discharge stability, the seed distribution uniformity, and the seed damage rate were below 2.23%, 7.52% and 0.056%, respectively, when operating at 8-10 km/h. Compared with the traditional outer groove wheel, the average coefficients of variation for the discharge stability and seed distribution uniformity, and the seed damage rate were reduced by 10.14, 4.5, and 0.093 percentage points, respectively. Furthermore, the inter-groove seed stress of the helical groove wheel was significantly lower, where the peak stress was reduced by about 50 percent. The seed stress was reduced across different groove wheels and seeding stages, leading to the low seed damage of the helical groove wheels. There was some impact of the staggered helical groove wheels on the performance of the centralized wheat metering devices. The finding can also provide the theoretical support for the operational stability and uniformity in the groove wheel-type conveying devices during agricultural production.

       

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