刀豆脱壳机构的设计与试验

为实现刀豆的机械化脱壳,设计了一种齿形轧辊式脱壳机构。该机构利用挤压和剪切复合产生撕搓效应的原理进行脱壳,通过调整脱壳轧辊对的轴心距,可适应不同品种、形状和尺寸荚果的加工。为确定脱壳机构的最佳工作参数,在分析其结构特点和脱壳工作原理的基础上,对研制样机进行了四因素混合水平的正交试验研究。根据因素的不同搭配对脱净率和损伤率的综合影响效果,采用综合评分法得出影响指标的主次因素排列顺序为刀豆品种、双辊间隙、双辊转速、辊面材料。试验结果表明,最佳作业参数条件:刀豆品种为矮生刀豆、双辊转速为25r/min、双辊间隙为18mm、辊面材料为橡胶。研究结果可为刀豆脱壳机的整体设计与优化提供重要依据。

Design and experiment of Canavalia shelling mechanism

Abstract: The traditional method of shelling of Canavalia pods is manually, labour intensive and tedious. To realize the mechanized shelling operation and improve the shelling efficiency in pod processing, a prototype machine of mechanical cracker was developed in this study. The shelling unit comprises a pair of shelling rollers which are gear shaped structure. The pods to be shelled fall into the shelling unit by gravity and are shelled by impact action. The shelled kernels and the broken pods drop to the conveyor to be collected. The shelling principle of the proposed mechanism is based on the ripping and rubbing effects by compressing and shearing action together. The shelling machine is easy to operate and maintain, cost-effective and environmentally friendly. With a roller clearance adjustment device, the proposed shelling machine for Canavalia pods is able to meet the wide range of shelling requirements such as different varieties, shapes and sizes. The shelling unit was presented in terms of structural features, work principle and parameter determination. Mathematic models describing the motion of pods were developed to study the equivalent force and friction angle to break whole pods in the shelling chamber. For the actual motion of the processing pod may differ from what in theory, it is essential to perform experimental verification. To determine the parametric combinations that would yield the optimum machine performance, the four-factor mixed-level orthogonal experiments for the prototype were carried out with two varieties of Canavalia, namely ensiformis and gladiate. Statistical analysis showed that the contact material of shelling roller related to the friction coefficient had highly significant effects on the shelling efficiency. It was found that the rotational speed of shelling roller did not show a significant difference for the percent damage. The comprehensive performance evaluation was used for analyzing the results to determine the effects of technical parameters on the shelling efficiency and percent damage. The results showed that the varieties of Canavalia made the strongest unique contribution to the integrative index, followed by the tip clearance between shelling rollers, rotational speed of shelling roller and contact material of shelling roller, respectively. It was found that the best operation conditions are at rotational speed of shelling roller of 25 r/min, tip clearance between shelling rollers of 18 mm with rubber as contact material of shelling roller and Canavalia ensiformis as the variety to be shelled. The research results can provide references for the overall design and optimization of Canavalia crackers to improve the product quality.