Abstract
This work describes the development, design, and parameter identification of a lychee peeling machine. The working principle of the machine combines two rollers with a pressing belt to separate the peel from the fruits. It was designed and its operational parameters identified on the basis of experimental data on the Thieu lychee, which currently covers about 80% of the plantation area in Vietnam. To this end, the first step was to measure the physical characteristics of the fruits, such as size, shape, and density. Moreover, the coefficient of static friction between lychees and rubber rollers, and the critical peeling force, were identified, with a view to optimizing the operational parameters later on. Results showed that a minimum tangential force of 10.5 N is needed to break the peel and separate it from the pulp. Based on the balanced force principle, various optimal machine parameters such as roller rotation speed, roller diameter, roller length, gap size between the two rollers, belt velocity, and minimum pressure of the belt were calibrated. In addition, spiral grooves were created on the roller surface to facilitate the motion of the fruits. The optimal results were roller size 900 × 100 mm (length × diameter), rotation speed 159 RPM, gap size between rollers 4 mm, belt size 850 × 60 mm (length × width), belt pressure 13.5 N, and belt velocity 140 mm/s. Using the design and operational parameters mentioned above, the machine was able to perform regularly at a throughput of 100 kg/h, as demanded by the current market. Moreover, it would be easily feasible to combine multiple pairs of rollers and pressing belts in order to increase throughput. The methodology for the design of this peeling machine and identification of working parameters with respect to experimental data could be applied in many other post-harvesting configurations.
Highlights
The lychee is a tropical fruit tree, growing mainly in the northern provinces of Vietnam and in many other countries such as China, India, and South Africa [1,2,3]
Based on the peeling friction principle, the two rollers rotate in opposite directions, whereas the belt exhibits a translation movement along the axial direction of the rollers
Where q is the expected throughput of a pair of rollers, Zfruit is the average number of fruits weighing 1 kg, a is the distance between two consecutive fruits along the roller axis, d is the average diameter of lychee fruits, β is the coefficient of distance between two consecutive fruits, Vb is the velocity of the belt, and γ is the coefficient of sliding of fruits
Summary
The lychee is a tropical fruit tree, growing mainly in the northern provinces of Vietnam and in many other countries such as China, India, and South Africa [1,2,3]. Typical mechanical properties of citrus fruits, such as maximum tensile force and displacement in the separation of peel, were measured to serve as indicators in designing the machine In another attempt, Jimoh et al [23] made improvements to their previous cassava peeling tool by using the impact principle. An appropriate machine combining friction and shearing principles for the peeling of lychees was developed in the Faculty of Engineering, Vietnam National University of Agriculture This machine was able to peel the lychees with a high rate of throughput and without affecting the fruit pulp. In order to establish the relation between the Vietnamese lychee crop and the machine’s operational parameters, it has hitherto been crucial to design the machine on the basis of experimental data Such a self-developed mechanization system could help more and more Vietnamese manufacturers of lychee products to increase their yield. This investigation favors agricultural mechanization, as the move greatly increases farm productivity
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