The undersea collecting vehicle is one of the three main parts in the deep-sea exploitation system. The Coandă effect-based collector picks up manganese nodules by providing an adverse pressure difference over the nodule, through the jet flowing around a curved wall. In order to overcome the drawbacks of repeated prototyping and experimenting in the traditional design procedure of the Coandă effect-based collector, the theoretical guide should be well placed to ensure correct design of the strongly related parameters of the collector. In this paper, a simplified model of curved wall jets was developed and the solution of approximate closed form was obtained to predict the lift force of the nodules. The variational tendencies of velocity, pressure and single-particle lift index perpendicular to the curved wall were investigated and the Coandă effects were found to be stronger with higher initial velocity, higher non-dimensional jet slot height and lower non-dimensional wall height. A CFD-DEM simulation of a number of particles was additionally performed to give more insight into the predictive accuracy of the simplified theory. Target lift force was found to be related to high efficiency in collection of particles, resulting in certain predictability of the theoretical model to the nodule lifting in a pre-prototype hydraulic device based on the Coandă effect.

Recently, researches on pump as turbine (PAT) have been one of the hot issues in fluid machineries. Of these hydraulic turbines, multi-stage PATs are widely used in industrial fields. However, most attentions have been paid on performance of the single-stage PATs and the turbines themselves. In this paper, a potential multi-stage PAT system with load pump was investigated numerically and experimentally. The match relations between PAT and load pump were explored by theory, and an analytical method to predict performance of PAT system was proposed in addition. Computational fluid dynamics method (CFD) was adopted to study the performance characteristics of PAT under a constant rotation or certain head. The operational rules of multi-stage PAT system were analyzed in both constant and variable speed that confirmed the prediction of system performance. The results could give guidance to choose a proper load pump and promote efficiency of PAT system.

The slurry pump, which forms the core equipment of the deep-sea mining (DSM) system, provides lifting power for the ore from the seabed to the sea level, which is crucial for the safety of coarse ore particle transportation. Velocity slip plays a significant role in revealing the migration of the pump particles. Therefore, this study analyzes the velocity slip in a slurry pump using the computational fluid dynamics–discrete element method (CFD-DEM) for the first time. The relationship between the pump head and velocity slip was proposed and verified in this study based on the velocity triangle and Euler equation of the solid-liquid two-phase flow in the impeller. The effects of different particle sizes on the velocity slip are compared in detail. According to the computational results, the head depends on the larger velocity slip of the impeller outlet and lower velocity slip at the inlet. The peak value of the velocity slip was significantly reduced, and the peak position of the velocity slip and zero-point position moved backward for particle sizes ranging between 5-15 mm. This study provides a reference for the problems of particle migration and velocity slip in slurry pumps.

This article studies the aerodynamic performance of a novel bypass shock-induced thrust vector nozzle. An arc-shaped bypass is innovatively designed to optimize nozzle performance and equips a variable shrinkage part. The nozzle performance is investigated numerically under diverse shrinkage area ratios. Computational results indicate that both geometry and friction choking have important effects on the nozzle performance. Normally, in the case of without any bypass shrinkage, the flow choking occurs at the bypass outlet. Very small bypass shrinkage is unable to change the flow choking location. The bypass geometry choking comes up at its throat as the shrinkage area ratio of the bypass reaches 0.06. According to computational results, the vectoring angle diminishes with the increasing shrinkage area ratio of the bypass, thrust force ratio, thrust efficiency, specific impulse ratio, and coefficient of discharge increase. As the NPR enlarges, the deflection angle and thrust efficiency decrease, and the thrust force ratio increases.

Slurry transport pumps, the central equipment of deep-sea mining (DSM) systems, provide the lifting power required for lifting mineral ores from the seafloor to the surface. The current technical challenges are associated with transport security and the economic aspects of coarse ore particles in pumps and pipelines. This paper focuses on the transportation characteristics of slurry pumps and uses theoretical methods, numerical calculations, and experimental methods to identify a feasible working mode. The geometric parameters of impeller channels in pump hydraulics significantly influence the migration properties of particles which in turn affects the overall security and economy of the system. The ratio of the impeller cross-sectional area F2/F1 (F1: cross-sectional area of the impeller outlet; F2: cross-sectional area of the impeller inlet) affects the particle passing capacity but negatively impacts pump efficiency. The percent of particles in the excellent passage interval of 0.2 s to 0.25 s increases from 25 to 43% when the number increases from 1.57 to 2.51. The pump behavior increases of the head by 5–10 m, and the efficiency decreases by 5–10%. So, the recommended span of F2/F1 is 1.57–2.00, and satisfying particle passing ability and efficiency can be achieved in this range. This study can provide a reference for the commercial transportation of slurry ores for deep-sea mining systems.