多子芋收获机离心回转式根土分离装置设计与试验

    Design and experiment of the centrifugal rotary root-soil separation device for a multiple taro harvester

    • 摘要: 针对芋头采挖过程中传统栅条式筛分装置存在土壤破碎质量差、根土分离效果不佳等问题,该研究结合多子芋生长特点,设计了一种离心回转式根土分离装置。构建芋头根土复合体碰撞力学模型和土块冲击破碎力学模型,明晰了影响根土分离效果的主要因素为弹齿倾角、回转筛转速和柔性拨指长径比,并确定取值范围。采用EDEM-RecurDyn耦合方法开展仿真试验,探究芋头根土复合体在筛分过程中经历平衡、失稳、土壤破碎、碰撞翻滚和土壤脱落等全过程动态变化规律,单因素试验确定柔性拨指直径14 mm,长度45 mm;以弹齿倾角、回转筛转速和土壤喂入量为影响因素。以根土分离率和芋头最大冲击力为评价指标,开展二次回归正交旋转组合试验,求解最优参数组合为弹齿倾角16.00°、回转筛转速110.00 r/min、土壤喂入量14.00 kg/s时,根土分离率最优为93.36%,芋头碰撞冲击力峰值最小为150.73N。田间试验结果表明多子芋收获机根土分离率为92.06%,破损率为4.86%,与回归模型预测结果相差1.39%,相较传统栅条式根茎类收获机根土分离率提升了8.61个百分点,满足多子芋根土分离要求。研究结果可为根土复合体破碎分离特性及根茎类作物高效低损采收装备设计提供参考。

       

      Abstract: Taro (Colocasia esculenta) is one of the perennial tuberous plants in the Araceae family. The global area of taro harvesting has reached 1.793 7 million hectares in 2022, with a total output of 12.394 5 million tons. The yield per unit area in China has been 2.75 times the world average in the world. The main production regions are situated in the Yangtze River Basin, the Pearl River Basin, and Taiwan Province. Taro can play a crucial role in the process of rural revitalization. However, manual harvesting has been predominant in recent years. It is still lacking in the specialized harvesting equipment for the mechanized production of taro. In a previous study, the bar-type screening device was employed to conduct taro harvesting experiments. The taro root system and the soil have also been adhered, wrapped, and entangled to form a "root-soil composite" structure during operation. This complex matrix can serve as the taro tubers to reinforce the fibers for the roots. Nevertheless, some challenges remain in actual production, including suboptimal soil crushing quality, ineffective root-soil separation, and elevated screening power consumption during mechanized harvesting. Furthermore, the existing bar-type screening device was unable to fulfill the requirement of taro root-soil separation requirements. In this study, the centrifugal rotary root-soil separation device was developed to fully meet the agronomic and harvesting requirements of multi-seed taro. A collision mechanics model of taro root-soil composite was developed for an impact crushing mechanics model of soil blocks. A systematic analysis revealed that the primary influencing factors on the efficacy of root-soil separation were ranked in the descending order of the spring tooth inclination angle, the rotational speed of the screen, and the aspect ratio of the flexible finger. The range of values was determined for the influencing factors after measurement. A discrete element model (DEM) of taro corm-root-soil composite was established using EDEM software, in order to analyze the process of soil fragmentation under impact collisions. The simulation experiment was conducted to couple the EDEM-Recur Dyn platform. A systematic analysis was made to determine the dynamic change of the taro root-soil composite during screening. There were the balance, instability, soil crushing, collision tumbling, and soil shedding. The single-factor test showed that the diameter and length of flexible fingers were 14, and 45 mm, respectively. A quadratic regression orthogonal test was conducted to identify the optimal combination of spring tooth inclination angle, rotary screen speed, and soil feed amount, with the root-soil separation rate and the maximum impact force of taro as the evaluation indices. The optimal combination of parameters was determined using the Design-Expert software. A high root-soil separation rate of 93.36% was achieved in the rotary screen speed of 110.00 r/min and a soil feed amount of 14.00 kg/s at an inclination angle of 16.00°. A series of field tests were conducted to validate the optimal parameters under identical operational conditions. The results indicated that the root-soil separation rate was 92.06%, which differed by 1.39% from the prediction of a regression model. At the same time, the taro damage rate was 4.86%. Five performance tests were conducted using the multiple taro harvester and the traditional bar-type rhizome harvester. The root-soil separation rate of the multiple taro harvester increased by 8.61 percentage points under identical operational conditions, while the damage rate increased by 0.99 percentage points. The centrifugal rotary device of root-soil separation fully met the requirements of root-soil separation of taro. The screening performance was better than the traditional grid-type screening device. The findings can serve as the sound foundation to design efficient and low-loss harvesting equipment in the crushing and separation of root-soil composite for root and tuber crops.

       

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