Performance characteristics of nodule pick-up device based on spiral flow principle for deep-sea hydraulic collection

Nodule pick-up devices are considered the most critical components in deep-sea mining robots. A proper nodule pick-up method brings many benefits, such as improved efficiency and reduced disturbance to the seafloor. In this paper, a novel hydraulic pick-up device is proposed based on the spiral flow principle. A comparative study is conducted to examine its performance characteristics. An optimal design of a spiral deflector for generating the spiral flow is achieved based on a numerical method, and the accuracy is validated by experiments. Subsequently, five types of cases are conducted, including characteristics of fixed and moving suction forces, movement features of spheres, suction flow field, and diffusion of sediment-water mixture to investigate the differences and similarities in collection performance between pick-up devices with and without spiral deflectors. The results prove that the pick-up device using spiral flow has advantages in regard to increasing the suction forces and critical bottom clearances, thus minimizing the operating flow rates. The suction force characteristics and motion behaviors for ore particles can be applied to build collection performance prediction models, to thereby achieve precise nodule collection. Thus, this study concentrates on the conceptual design and performance verification of a nodule pick-up device.