Design and application of the harvesting boat for laver (Porphyra yezoensis)

Laver (Porphyra yezoensis) is an important economic algae along the Yellow Sea coast and has become an important pillar industry in China's coastal marine aquaculture industry. However, at present, the simple harvesting equipment with foam floating raft and cutter is used for laver harvesting, which has many problems, such as high potential safety hazard, high energy consumption, and high rate of damage during harvesting, which seriously restricts the development of laver breeding industry. This research combines the plug-in aquaculture mode to design adjustable cutting length laver harvesting tools, curtain picking mechanisms, and a hydraulic drive system for the entire boat, which are integrated into high-density polyethylene catamarans to achieve efficient automation operations from mesh curtain picking to laver harvesting, promoting the efficient and healthy development of the laver aquaculture industry. Through ANSYS finite element analysis, it was demonstrated that the boat's strength meets the requirements. A mathematical model of the force on the curtain frame and cutting tool was established, and the parameter ranges of the curtain frame's water depth, cutting tool diameter, and speed were determined. Designed an integrated system for boat propulsion and hydraulic control, established a hydraulic system simulation model based on AMESim, and demonstrated the rationality of the hydraulic control system. In order to verify the applicability and reliability of the harvesting boat, the prototype was tested in two stages. In the first stage, the harvesting efficiency and cutting quality experiment of the operating boat were carried out. The factors affecting the harvesting efficiency were optimized and tested through orthogonal experiments. The optimal process parameters of the operating system were determined as follows: the angle of the curtain rack enter the water was 35°, the cutting tool speed was 450 r/min, the ship operation speed was 0.8 m/s, and the blade structure was a triple helix tool, respectively. Production comparison experiments were carried out in the second stage. Under the best working parameters, the HDPE laver harvesting boat conducted productive tests in Dalian Jiaoliu Island and Lianyungang Ganyu District respectively, and took the cutting efficiency and damage rate as evaluation indicators. The experiment results showed that in the sea area of Jiaotong Island in Dalian City, the average harvest efficiency of HDPE laver harvesting boat is about 1.63 t/h, which is about 14% higher than that of foam raft laver harvesting boat, and there was a significant difference (P<0.05). In the sea area of Lianyungang Ganyu District, the average harvest efficiency of HDPE laver harvesting boat is about 1.92 t/h, which is about 12% higher than that of foam raft laver harvesting boat, and there is a significant difference (P<0.05). In order to test the cutting accuracy of laver, the average length of laver before harvesting is about 15 cm, and the maximum length of laver after harvesting is 6 cm, the minimum length is 4 cm, which can be basically controlled within ±1 cm, and the damage rate is less than 5%, which verified that the harvesting boat had good cutting accuracy. The HDPE laver harvesting boat designed in this study is in line with the development of laver industry, and has good application value.