Design and experiment of the clamping sheller for fresh water caltrop

Abstract: Water caltrop is one of the annual herbaceous aquatic vegetables in the Lower-and-Middle Section of theYangtze and Pearl River Delta region in China. There is the high nutritional and medicinal value of water caltrop. Among them, the stems and leaves can be used as the green manure or fodder, the petioles and the ripe fruits as the vegetables or starch, the fresh and tender flesh as the raw fruit, as well as the shell can be used to extract the functional ingredients, such as natural pigments. The kernel of water caltrop can also be fabricated into the popular cans, the pickled bags, and special commodities. Nevertheless, the kernel shelling can be the most difficult and the longest duration in the postharvest processing of water caltrop, including the cleaning, grading, shelling, and packaging. The current shelling of fresh water caltrop also depends mainly on the manual operation, due to the irregular shape, hard shell, and uneven surface. The manual shelling cannot fully meet the large-scale production in recent years, particularly for the high labor intensity, low efficiency, as well as the high damage rate with the perishable meat after damage, unfavorable storage and subsequent processing. It is still lacking on the automatic shelling machinery of water caltrop in China at present. More than 90% of the water caltrop products are the raw materials without shelling. A high demand can also be required for the kernel of water caltrop as the high value-added products. Therefore, it is of great significance to clarify the shelling mechanism and the mechanized production, especially with the increase of planting area and output of water caltrop industry. In this study, a clamping sheller was designed for the fresh water caltrop. The overall dimensions and mechanical performance parameters of the water caltrop were collected from the producing base in the Xishui County, Hubei Province, China. According to the configuration and working principle of the whole machine, the structural parameters of the key components were determined, such as the clamping plate, transversal cutting blade, elastic pressing, and shelling device. The working parameters of the transversal cutting blade was analyzed to simulate the motion of water caltrop in the transversal cutting device using ANSYS explicit dynamics. A transversal cutting test was performed on the prototype of the clamping sheller for the fresh water caltrop. The working parameters of the transversal cutting device were also optimized by Design Expert 12.Theresults showed that there was a significant impact of the maturity, conveying, and blade speed on the shell cutting rate, but no significant impact was found on the loss rate of water caltrop kernel. An optimal combination of parameters was achieved in the maturity value of 1.000 01, the conveying speed of 0.100 01 m/s, and the blade speed of 999.981 r/min. The average shell cutting rate and the loss rate of water caltrop kernel were 79.41%, and 9.82%, respectively. Therefore, the optimum working parameters of the shelling device were as follows: the maturity value of 1.008 9, the slow roll speed of 58.862 7 r/min, and the line speed ratio of 1.490 66. The average shelling rate was 66.52%, whereas, the average damage rate of water caltrop kernel was 12.83% in this case. This finding is expected to provide a strong reference for the shelling machinery of fresh water caltrop.