Authors

Abstract

This study established an integrated experimental–simulation framework for optimizing the green-husk dehusking process of macadamia nuts. The objective was to quantify the effects of drum speed, minimum gap, and feed rate on dehusking performance and kernel integrity. Mechanical characterization was conducted through static loading tests in three orthogonal orientations to determine the anisotropic fracture behavior of green husks. Discrete element simulations (EDEM) were calibrated using measured friction, restitution, and density parameters and validated through a repose-angle test. A Box–Behnken design with response surface methodology was applied to evaluate interactive effects among process parameters and derive an optimal operating region. The equivalent peeling force of green husks ranged from 0.30 to 2.00 kN. Drum speed was the dominant factor influencing dehusking efficiency (p < 0.01), while minimum gap and feed rate had weaker main effects. The validated model predicted a stable high-performance window at 300–400 rpm, 9–10 mm minimum gap, and 6–10 kg min⁻¹ feed rate. Under optimal conditions (400 rpm, 9.5 mm, 6.3 kg min⁻¹), the measured dehusking rate reached 95.4% with a kernel damage rate of 4.76%. These results demonstrate that the combined experimental–DEM(Discrete Element Method) approach provides a reliable basis for parameter tuning and structural design of macadamia dehusking equipment, enabling improved efficiency and reduced kernel damage.

Abstract in Chinese

本研究构建了一种用于优化夏威夷果青壳脱壳过程的试验–仿真一体化框架，旨在定量分析滚筒转速、最小间隙和给料量对脱壳性能及坚果仁完整性的影响。通过在三个正交方向上的静载试验对青壳进行力学表征，以确定其各向异性断裂行为。基于离散元软件 EDEM 的仿真,采用实测的摩擦系数、恢复系数和密度参数进行标定，并通过休止角试验完成验证。利用 Box–Behnken 试验设计结合响应面方法，评估工艺参数之间的交互作用并确定最优运行区间。结果表明，青壳等效剥离力范围0.30～2.00 kN。滚筒转速是影响脱壳效率的主导因素（p < 0.01），而最小间隙和给料量的主效应相对较弱。经验证模型预测，在转速300～400 rpm、最小间隙 9～10 mm、给料量 6～10 kg·min⁻¹ 条件下存在稳定的高性能工作窗口。在最优工况（400 rpm、9.5 mm、6.3 kg·min⁻¹）下，实测脱壳率达到95.4%，仁破损率为4.76%。 研究结果表明，试验与DEM（Discrete Element Method，离散元方法）相结合的研究方法，可为夏威夷果脱壳设备的参数整定与结构设计提供可靠依据，从而提高脱壳效率并降低仁破损率。