•A water hydraulic manipulator is designed.•The valve group of water hydraulic high speed on-off valve is designed to control the hydraulic cylinder directly.•The experiment verified that the ...high-speed on-off valve-controlled cylinder system has good application effect in water hydraulic manipulators.•The adaptive fuzzy PID with dead-area compensation is proposed and significantly improves the control accuracy of hydraulic cylinders.
In contrast to oil hydraulics, water hydraulics presents distinct advantages, such as minimal environmental pollution, reduced operational cost, and no chemical reactions. Water hydraulic manipulators are instrumental in maintaining and handling fusion reactors. The valve-controlled hydraulic cylinder system (VCHCS) is the core of the manipulator's actuator. This study focuses on the control of a water hydraulic VCHCS, where tap water serves as the medium, replacing conventional hydraulic oil. The integration of four high-speed on-off valves (HSVs) forms a valve group, supplanting the traditional servo valve and facilitating the precise control of the water cylinder's motion. Given the asymmetrical movement characteristics of the water cylinder, a control strategy employing adaptive fuzzy PID with blind-area compensation (AFBC) for HSVs within the designed VCHCS is proposed. Comparative analyses of control precision are conducted among three methods, single PID, double PID, and AFBC, through both simulations and experiments. The experimental results show that the accuracy of fixed-point position tracking is 0.5 mm. In dynamic position tracking, the accuracy of the AFBC is enhanced from 1.5–2 mm to 0.5–0.9 mm compared to the conventional PID method. The experimental findings affirm the feasibility of HSVs driving the water cylinder directly. Using water as the medium further renders the system more suitable for operations within fusion reactors.
Energy consumption in reverse osmosis has decreased substantially over the last few decades thanks to the implementation of energy recovery devices, high efficiency pumps, and improved membranes. ...However, to further increase the adoption of the technology, its energy needs must still be reduced. Batch and semi-batch reverse osmosis configurations have shown potential to be the most energy efficient reverse osmosis variants, but have remaining inefficiencies from brine mixing and high downtime. In this study, we modeled in new detail a further improved double-acting batch reverse osmosis system that uses a high-pressure tank with a reciprocating piston. A high-pressure pump is used to fill the inactive side of the high pressure tank with feed that pressurizes the reverse osmosis system during the permeate production stage; the feed is then used as the working fluid for the next cycle of the system. Additionally, to account for the dynamic behavior of the system under different operational conditions, a hydraulic simulation model was developed to accurately predict the evolution of the pressure and other important parameters over time. A specific energy consumption of 1.88 kWh/m3 was calculated for seawater with a salinity of 35 g/kg, recovery of 50%, and a permeate flux of 15 LHM, and lower values SEC were obtained for lower permeate fluxes. Moreover, the downtime was found to be below 10% of the cycle time, without significantly increase the energy consumption of the system. This design also showed the potential to reduce the start-up time compared to previously proposed batch RO configurations.
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•The proposed double-acting batch RO configuration has a reduced energy use compared to previously proposed systems.•Properly designed double-acting batch RO systems have lower downtimes and start-up times than others batch RO system.•Water hydraulic models help to accurately predict the evolution of the pressure in batch RO systems.
The 3/2 water proportional directional valve (PDV) is an important hydraulic component to ensure a precise, low impact, and safety control of hydraulic powered roof support, which has been a ...technical challenge facing to coal mining industry for many years. To address this issue, a new 3/2 water PDV is developed. The valve includes a novel three-core follow-up servo mechanism consisting of three key components: the pilot inlet valve, the pilot outlet valve, and the main inlet spool. This mechanism enables precise and reliable opening, and closing capacity of the valve. The prototype is manufactured and the performance test is conducted to improve the control performance of the new water PDV. During the test, two significant discoveries are made. First, it is determined that the control chamber of the main inlet spool must be in the predischarge state at the initial time to ensure adequate closing capacity of the new valve during the returning process. Second, it is found that the continuous small-step control mode can better cope with the friction and is more effective in achieving quick and smooth following characteristics of the three valve cores in the opening process, compared with the ramp control mode.
Open-circle sea water hydraulics, utilizing surrounding water as a working medium, has become more and more popular in submersible. Axial piston pump with port valves is used frequently in the ...open-circle water hydraulic system. Port valve is one of the important parts in this type pump. However, there are few literatures about the effect of the port valves’ materials on the noise characteristic of the water pump. In this study, the effect of materials on the noise of the pump was researched through experimental and theory simulation methods. The influences of three kinds of plastics (Polyetheretherketone (PEEK), Polytetrafluoroethylene (PTFE), Aliphatic polyamides (NYLON)) and one kind of anti-corrosion stainless steel (316L) are compared. The noise of the pump with the different materials port valve seat ranges from high to low as the order: 316L>NYLON>PEEK>PTFE. The differences would contribute to the collision between valve spool and seat, which is identified by the simulating results. The experimental results showed that the difference of noise between PEEK and PTFE is small. In addition, the lifespan and volumetric efficiency are also taken into considering. The PEEK is selected to use in the seawater pump for a large submersible.
•Port valve is one of the important parts of piston pump.•Effect of materials on the noise of the pump was studied.•Noise of the pump ranges from high to low as the order: 316L>NYLON>PEEK>PTFE.•Life span and volumetric efficiency are also taken into considering.•The PEEK is selected to use in the seawater pump for a submersible.
This paper investigates working characteristics of a spherical water pump through the experimental test and theoretical modeling. Both theoretical models of displacement and the real time delivered ...flow are established precisely based on the working principles of spherical pump, under spherical and polar coordinate systems, to investigate the effects structural parameters on flow characteristics. A test rig is established to investigate and validate the working characteristics of spherical pump. Performance such as leakage characteristics, flow characteristics, power consumption and noise radiation are tested, and the theoretical models are validated under multiple working conditions. Results indicate the proposed models are effective to characterize the working properties of spherical water pump, which also demonstrates reasonable performance on the power consumption and noise radiation characteristics. These studies provide fundamental principles for abiding in designing the high-performance spherical water pump.
•Both displacement model and delivered flow of spherical water pump are proposed.•The test rig is established to investigate the working characteristics.•Power consumption and noise characteristics are presented.•The efficiency and stable operating speed of the prototype is 1,400 rpm.
The seawater hydraulic variable ballast system (SHVBS) is critical equipment for underwater operations. Reciprocating seals play a vital role in the efficiency and safety of seawater hydraulic ...components working in SHVBS. However, the sealing performance and friction behavior of reciprocating seals remain unknown under high isostatic and water-lubricating conditions. In this work, an innovative mixed lubrication model for reciprocating water hydraulic rod seals is developed based on the elastohydrodynamic lubrication (EHL) theory. An elastic deformation method is introduced to update the film thickness rapidly. The characteristics of the reciprocating seal are studied in a full-ocean-depth pressure range. With the rod speed of 500 mm/s, for sealed pressure of 0.1 MPa and 120 MPa, the maximum friction force increases 10-fold, from about 30 N to 300 N. A test rig is designed to measure friction force under high pressure. The numerical and experimental results have the same variation pattern, and the relative error is less than 15%.
Today, there are several water–hydraulic, power-control systems already available on the market. Their components are usually made of stainless steel, which ensures satisfactory performance under ...mild, conventional operating conditions. However, for more demanding operating conditions and long-term, low-friction and low-wear performance, they do not provide the required performance. One of the possible ways to improve the performance of stainless-steel components in water–hydraulic systems is to coat them with diamond-like carbon (DLC), since this material is well known for its excellent low-friction and low-wear characteristics and also provides very good performance under water-lubrication conditions. In this study, real-scale lifetime tests with 2.3 million cycles were performed on a hydraulic test rig with a proportional 4/3 directional control water–hydraulic valve. Two types of contacts in the valve were tested: the steel-spool/steel-sleeve and the DLC-spool/steel-sleeve. The wear behaviour of the valve was evaluated with a scanning electron microscope (SEM) and internal leakage measurements. In the real-scale lifetime tests the wear and the damage on the DLC-coated spool were significantly lower than on the steel spool. Furthermore, in agreement with this, the internal leakage in the DLC-spool/steel-sleeve valve was almost constant throughout the tests, while in the steel-spool/steel-sleeve valve the leakage slowly, but steadily, increased. The steel/steel and DLC/steel contacts were also separately evaluated in pin-on-disc model tribological tests under water-lubricated conditions for a comparison and for a better understanding of the tribological mechanisms. In agreement with the real-scale tests, the DLC/steel contact showed improved friction and wear performance in comparison with the steel/steel contact.
► Lifetime performance of real-scale 4/3 water–hydraulic valve is studied. ► We compare two types of contacts in the valve: steel/steel and DLC/steel. ► DLC coating significantly reduces the leakage of the valve compared to steel valve. ► DLC coating significantly reduces the wear of the valve compared to steel valve. ► On steel counterpart low-friction amorphous transfer film is formed.
Fluidic artificial muscles are popular in robotics and function as biomimetic actuators. Their pneumatic version has been widely investigated. A novel water hydraulic artificial muscle (WHAM) with ...high strength is developed in this study. WHAMs can be applied to underwater manipulators widely used in ocean development because of their environment-friendly characteristics, high force-to-weight ratio, and good bio-imitability. Therefore, the strength of WHAMs has been improved to fit the requirements of underwater environments and the work pressure of water hydraulic components. However, understanding the mechanical behaviors of WHAMs is necessary because WHAMs use work media and pressure control that are different from those used by pneumatic artificial muscles. This paper presents the static and dynamic characteristics of the WHAM system, including the water hydraulic pressure control circuit. A test system is designed and built to analyze the drive characteristics of the developed WHAM. The theoretical relationships among the amount of contraction, pressure, and output drawing force of the WHAM are tested and verified. A linearized transfer function is proposed, and the dynamic characteristics of the WHAM are investigated through simulation and inertia load experiments. Simulation results agree with the experimental results and show that the proposed model can be applied to the control of WHAM actuators.
