Parameter Optimization and Performance Validation of a Cone-Type Macadamia Nut Sheller Based on the Discrete Element...

Area of Science:

• Agricultural Engineering
• Mechanical Engineering
• Computational Mechanics

Background:

• Macadamia nut shelling presents challenges due to shell hardness and size variability.
• Improving shelling efficiency and maintaining kernel integrity are crucial for commercial processing.

Purpose of the Study:

• To investigate macadamia nut shelling characteristics using the discrete element method (DEM).
• To optimize equipment parameters for enhanced shelling rate and whole kernel rate.
• To develop and validate a DEM model for macadamia nut shelling simulations.

Main Methods:

• Macadamia nut dimensions and shelling forces were measured.
• A discrete element method (DEM) model with BondingV2 adhesive bonds was developed and validated.
• Box-Behnken experimental design was employed to optimize rotational speed, pitch, taper ratio, and thread turns.
• Simulations were validated with bench tests of a prototype sheller.

Main Results:

• Thread turns, pitch, rotational speed, and taper ratio significantly influenced whole kernel and shelling rates.
• Optimized parameters (129 r/min, 32.8 mm pitch, 0.097 taper ratio, 1.3 thread turns) yielded a predicted 79% whole kernel rate and 94.3% shelling rate.
• Prototype tests confirmed simulation accuracy with 78% whole kernel rate and 91% shelling rate.

Conclusions:

• The discrete element method (DEM) provides a reliable tool for simulating and optimizing macadamia nut shelling.
• The developed taper-ratioed rotating cylinder sheller demonstrates effective parameter control for variable macadamia nut properties.
• Optimized parameters significantly enhance shelling efficiency and whole kernel integrity compared to conventional methods.