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Pump-controlled actuators, or more generically, hydrostatic actuators, have the significant advantage of not relying on valves to control the cylinders. This results in much better energy usage compared to traditional valve-controlled systems. However, it is possible to further increase energy efficiency by storing load energy in motoring quadrants and subsequently releasing the stored energy back into the circuit or making it available for other applications. Much work is needed to practically study energy storage in hydrostatic actuators. In this note, we review the two basic ways hydraulic energy can be saved in circuits using accumulators, emphasizing their advantages and drawbacks. The review is followed by a brief description of the current research being carried out at the University of Manitoba in Canada. We aim to show that research in this field is promising and demonstrates that hydraulic power transmission can not only be made efficient but also be used to regenerate load energy that would otherwise go to waste. [ABSTRACT FROM AUTHOR]

Pump-controlled actuators, or more generically, hydrostatic actuators, have the significant advantage of not relying on valves to control the cylinders. This results in much better energy usage compared to traditional valve-controlled systems. However, it is possible to further increase energy efficiency by storing load energy in motoring quadrants and subsequently releasing the stored energy back into the circuit or making it available for other applications. Much work is needed to practically study energy storage in hydrostatic actuators. In this note, we review the two basic ways hydraulic energy can be saved in circuits using accumulators, emphasizing their advantages and drawbacks. The review is followed by a brief description of the current research being carried out at the University of Manitoba in Canada. We aim to show that research in this field is promising and demonstrates that hydraulic power transmission can not only be made efficient but also be used to regenerate load energy that would otherwise go to waste.

Hydraulic accumulators have long been used in hydraulic circuits. Applications vary from keeping the pressure within a circuit branch to saving load energy. Among these applications, storing and releasing energy has gained attention in recent years due to the need for efficient circuits. In this sense, accumulators are the hydraulic counterparts of batteries and capacitors in electrical circuits. From hydraulic hybrid vehicles to complex agricultural machinery, accumulators have been successfully implemented, and significant energetic gains have been reported. This article reviews typical applications where accumulators can be used to this end and discusses the challenges that still have to be overcome in each situation.

The main direction of the industrial development of Ukraine is the solving of the environmental pollution problems under the conditions of preservation of natural resources through complex use of raw materials with involvement of industrial wastes. The developed technology is intended for galvanic, accumulator, machine-building, mine and other enterprises, the wastewater from which contains ions of heavy metals. Heavy metal ions are extremely dangerous toxic substances because of a cumulative effect on aquatic organisms. In order to remove copper ions from aqueous solutions, the chemical precipitation with lime is used. The choice of reagent is associated with its cheapness. The most effective reagent precipitation of copper ions in the form of hydroxide occurs when the pH is raised to 10. In this work, the influence of sludge, which is formed as a result of water purification from copper ions, on the properties of cement was investigated. The effect was evaluated on the following properties: normal density of cement, hardening time, compressive strength at the age of 2 and 28 days and water separation coefficient. This allowed us to develop effective ways to their disposal. The developed method provides: a high degree of metal removal (up to 98-99%); simplicity of technological process; small capital and operating costs; complex technology of wastewater treatment process. Thus, the results of the study will contribute to the creation of lowwaste and non-waste technologies for waste processing and disposal. [ABSTRACT FROM AUTHOR]

Purpose: The mechanical molecular spring isolator (MMSI) presents the characteristics of high-static-low-dynamic-stiffness to isolate the low-frequency vibration of a heavy payload. Methods: An MMSI consists of a piston-cylinder container full of the liquid and some hydraulic spring accumulators. This paper focuses on a particular type of the MMSI that all hydraulic spring accumulators applying the conventional coil spring are identical. Results and conclusion: In the beginning, the MMSI stiffness model is modelled and the influences of critical parameters on the stiffness property are studied. The MMSI presents a piecewise linear stiffness property. The averaging method is applied to determine the primary resonance response, and the energy transmissibility is adopted to estimate the vibration isolation performance. A jump phenomenon is inevitable to be occurred around the resonance region. The jump avoidance is a critical design part of the MMSI isolation system. On the other hand, based on the stiffness model, it reveals that any stiffness of the coil spring or any size of the accumulator in the MMSI will be able to achieve the same desired stiffness property. The most significant difference between all solutions depends on the coil spring lateral stability. The coil spring lateral stability magnitude is defined as the ratio of the deflection to the buckling deflection to evaluate the quality of each solution. Then, the fundamental design criterion on the MMSI based on jump avoidance and the coil spring lateral stability is established. [ABSTRACT FROM AUTHOR]

Abstract This study is focused on the design of the subsea accumulators currently used to deliver a pressurized fluid whose function is to actuate safety operations on a subsea well. API 16D, whose specifications regulate the design method of a bank of accumulators, was revised, discussed, and resumed in terms of a nomogram whose engineering value is useful for designers. An additional nomogram was derived allowing to perform the verification process which is suggested by the norm, in order to verify the fulfillment of the actuations requested to the accumulators. This verification phase caught the interest of the Authors: API 16D assumes for the design that the Functional Volume Requirement (FVR) – the sum of the quantities of pressurized fluid to be delivered for different sequenced‐in‐time functions – is delivered at the Minimum Operating Pressure (MOP) requested by the last actuation. This hypothesis simplifies the design, but the result cannot fulfill the previous functions because of the pressure lack (energy content in the pressurized propelling gas) which can happen. The use of the two nomograms proposed simplifies the application of the design procedure and allow to discuss main sensitivities of the variables involved (FVRs & MOPs), evidencing which variables deserve more attention and accuracy. In particular, the use of the second nomogram permits to verify that the right volumes of fluid during the actuations are delivered above a minimum pressure level, so guaranteeing the fulfillment of the function. It is based on a thermo‐fluid‐dynamic discharge modeling of the accumulators. The paper outlines a design direction which minimizes the number of accumulators and opens the way to a different design approach, based on a fully physical discharge process description.

The accumulator is a crucial component of the hydraulic power for servomechanisms of the launch vehicle, which has a significant effect on the performance and the mass power. Traditional design methods are mostly based on empirical formulas, which do not meet the requirements of the fine design of aerospace products. The physical model, the mathematical model of the accumulator and joint simulation model of the energy and the control loop are established, and parameters satisfying the extreme flight operation profiles are obtained, including the discharge volume, charge volume and charge pressure. The flight data of third-stage servomechanisms of the Long March 3 series Launch Vehicle were analysed, which is consistent with the simulation data, indicating that the accumulator has exerted the maximum capability in the extreme flight condition, and the maximum mass power has been realised. [ABSTRACT FROM AUTHOR]

Abstract Reciprocating-switcher energy recovery device (RS-ERD) can reduce the energy consumption in membrane desalination system for its high efficiency. However, the initial one-plate structure of the RS-ERD requires a large diameter in plates to ensure its basic capacity, which not only enlarges the switching load of water hydraulic actuator, but also causes a significant fluid fluctuation of the device during the stroke switching. To solve the problem, a modified RS-ERD with the pilot valve plates was designed and experimentally investigated in a SWRO desalination system. The experimental results illustrated that compared to the previous RS-ERD, the starting-up pressure for the new RS-ERD decreased by a half to be about 0.25 MPa, and 72.16% HP brine consumption for water hydraulic actuator was reduced in stroke switching. Thanks to the significant decrease in HP brine consumption, the pressure fluctuation amplitude in HP fluids was declined by 40% under the pressure of 6.00 MPa and the flow rate of 30 m3/h. Meantime the new RS-ERD remains a competitive energy recovery efficiency of up to 98.50%. This paper provides a practical method to improve the working performance of RS-ERD. Highlights • The pilot valve plate and self energized seal are innovatively adopted in RS-ERD. • The switching load and fluid fluctuations are experimentally investigated. • The HP brine consumption for stroke switching has decreased by 72.16%. • The pressure fluctuation amplitude in HP fluids has declined by 40%. [ABSTRACT FROM AUTHOR]

Water reuse is considered one of the most efficient and optimum ways in petroleum industries to address the water scarcity problem. The effluents which are made by the petroleum operations are supposed to be one of the hazardous materials when they are discharged to the environment. The objective of this study is to measure the volume of the required water for the operational performances of the studied oil field. To do this, the necessary water and the volume of provided treated water for the waterflooding, tertiary flooding, and hydraulic fracturing procedures are appropriately measured and by the utilization of photo-Fenton/flotation are administered to remove the oil droplets. According to the observational measurements, it is clarified that hydraulic fracturing has supplied approximately 93% of its required water by the treatment of flowback water and it virtually eliminated the necessity of fresh water from local or domestic water resources. Moreover, the total freshwater that has been saved in this oil field is investigated about 80% of the total required water for their performances. Consequently, the lower need of fresh water from local resources would reduce the unnecessary expenses to provide this volume of water and would save fresh water for about 2750 inhabitants for 1 year to overcome the issue of water scarcity in the world. [ABSTRACT FROM AUTHOR]

An improved model of the active suspension system is proposed. Compared with the existing model of active suspension system, the dynamics of a hydraulic actuator in the active suspension system is fully considered in the proposed model. Based on the proposed model, a sliding-mode control method is designed to control the active suspension system. Stability proof and analysis of the closed-loop system of the active suspension is given by using Lyapunov stability theory. At last, the reliability and feasibility of the proposed sliding-mode control method are evaluated by computer simulation. Simulation research shows that the proposed sliding-mode control method can obtain good control performance for the active suspension system. [ABSTRACT FROM AUTHOR]

Two-fluid equations are widely used to simulate thermal-hydraulic phenomena in a nuclear reactor. Simulation accuracy depends on the modeling terms in the two-fluid equations. For a dispersed flow, the overall two-phase pressure drop by wall friction must be apportioned to each phase in proportion to the fraction of each phase (Kim et al., 2014). By applying this approach, the prediction of bubble phase velocity can be close to that of liquid for a fully developed flow in a horizontal pipe with a constant area. One may want to know what would happen in the area-varying channels. It is always true that the bubble density is much lower than the water density. Hence, the bubble would accelerate faster than the liquid in a nozzle in which the pressure decreases along the downstream; the bubbles would decelerate more quickly than the liquid in a diffuser in which the pressure increases along the downstream. The purpose of this study was to investigate those behaviors in an area-varying channel using the experimental data and MARS simulations. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of two phases were measured with the help of the PIV technique. The experimental result showed that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle region; in contrast, the bubble was slower than the liquid in the diffuser region. MARS code simulations were performed to assess the wall drag model. By replacing the original wall drag partition model in the MARS code with Kim’s one, the simulation results were consistent with experimental observations. [ABSTRACT FROM AUTHOR]

Within the MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) project, the Belgian Nuclear Research Centre SCK•CEN is developing and designing a flexible irradiation facility, configured as an accelerator driven system (ADS) with a MOX fueled reactor core, able to operate in both critical and sub-critical modes. The system design features a compact pool-type primary cooling system operating with molten Lead-Bismuth Eutectic (LBE). With regard to the thermal-hydraulic design and safety assessment of the installation, a major challenge is represented by the complex coolant flow field characterizing the large open regions of the primary vessel, namely the cold and hot plenum, with the presence of pronounced three-dimensional phenomena that may impact the evolution of accidental transients such as loss of flow events. In order to have a realistic representation of such effects, a coupled system thermal-hydraulic/CFD model of the MYRRHA reactor is developed and presented in this paper. The proposed multi-scale methodology, which couples the 1D system code RELAP5-3D to the CFD code FLUENT, is based on domain decomposition and a novel implicit numerical scheme is developed. The coupled reactor-scale computational model is applied in this work to the analysis of a postulated protected loss of flow (PLOF) accident, and preliminary validated against RELAP5-3D stand-alone solution data. The results of the analysis were found in agreement, demonstrating the capability of the tool to perform integral simulation taking into account 3D flows and local phenomena. [ABSTRACT FROM AUTHOR]

A novel roll-resistant hydraulically interconnected suspension with dual accumulators on each fluid circuit (DHIS) is proposed and dynamic characteristics of vehicle incorporating DHIS subsystem are studied in this paper. A 10-degrees-of-freedom (DOFs) vehicle model coupled with DHIS subsystem is established and validated. Four physical parameters of DHIS subsystems which are crucial to vehicle responses are selected with prescribed variation ranges to explore their relationships with the vehicle performance. Simulations of vehicle conducting sine-wave steering maneuvers are carried out to evaluate handling performance with roll angle and vertical tyre force for DHIS subsystem with the parameters varying, compared with the results for vehicle with the original spring-damper suspension and conventional hydraulically interconnected suspension (HIS). On the other hand, ride comfort performance indicated by total weighted root mean square accelerations at the center of gravity is studied when vehicle is excited by three different types of road pavements when the four parameters vary in the prescribed ranges. Simulation results are compared to investigate the special merits of DHIS subsystem, and the parameters that influence the handling performance and ride comfort most are identified. Overall, the DHIS subsystem can effectively enhance the vehicle handling performance compared with the original spring-damper suspension, and it can also benefit much to the ride comfort in contrast to the HIS subsystem. [ABSTRACT FROM AUTHOR]

Abstract: This study is focused on the design of the subsea accumulators currently used to deliver a pressurized fluid whose function is to actuate safety operations on a subsea well. API 16D, whose specifications regulate the design method of a bank of accumulators, was revised, discussed, and resumed in terms of a nomogram whose engineering value is useful for designers. An additional nomogram was derived allowing to perform the verification process which is suggested by the norm, in order to verify the fulfillment of the actuations requested to the accumulators. This verification phase caught the interest of the Authors: API 16D assumes for the design that the Functional Volume Requirement (FVR) – the sum of the quantities of pressurized fluid to be delivered for different sequenced‐in‐time functions – is delivered at the Minimum Operating Pressure (MOP) requested by the last actuation. This hypothesis simplifies the design, but the result cannot fulfill the previous functions because of the pressure lack (energy content in the pressurized propelling gas) which can happen. The use of the two nomograms proposed simplifies the application of the design procedure and allow to discuss main sensitivities of the variables involved (FVRs & MOPs), evidencing which variables deserve more attention and accuracy. In particular, the use of the second nomogram permits to verify that the right volumes of fluid during the actuations are delivered above a minimum pressure level, so guaranteeing the fulfillment of the function. It is based on a thermo‐fluid‐dynamic discharge modeling of the accumulators. The paper outlines a design direction which minimizes the number of accumulators and opens the way to a different design approach, based on a fully physical discharge process description. [ABSTRACT FROM AUTHOR]

An improved smoothed particle hydrodynamic (SPH) model is developed to study the complex hydrodynamic behaviour of an onshore oscillating water chamber. The improvements include adding a diffusive term to the continuity equation and incorporating the corrective smoothed particle method (CSPM). A modified boundary condition is implemented to better simulate the pressure field near the solid boundary. The SPH model is first verified by comparing the numerical results with analytical solutions and the available experimental data. The verified model is then applied to study the hydrodynamic behaviour of an onshore oscillating water chamber. The free surface elevations inside the water chamber and the total forces acting on the front wall of the water chamber are studied for different wave conditions. The turbulence energy distribution and the sloshing phenomenon in the water chamber are also investigated. [ABSTRACT FROM AUTHOR]

To reduce the energy consumption and emissions of a hydraulic excavator (HE), an electric motor (EM) is employed to replace the internal combustion engine (ICE) that powers the hydraulic pumps. Owing to the excellent control characteristics and high efficiency of the EM, a two-level idle speed control system with a hydraulic accumulator (HA) for a HE is proposed to reduce energy consumption and improve the control performance of the actuator when the idle speed control (ISC) is switched off. A mathematical model is established and key parameters are analyzed and optimized. A simulation is performed using AMESim, and a control strategy for the two-level idle speed control is developed by using a co-simulation between AMESim and Simulink. A test rig is built based on the optimized parameters and simulation results. Experimental results show that the EM speed can be automatically switched between the first idle speed, second idle speed, and normal operating speed. Although the idle speed of the EM in the novel ISC system can be reduced more than that in a conventional ISC system, the proposed ISC system can still build actuator pressure more quickly in a working mode when the ISC is switched off. Compared to a system without idle speed control, the energy saving of the proposed system is approximately 36.06%. The proposed two-level idle speed control system with a HA can achieve high energy efficiency and excellent control performance, and it can be also applied to engine-driven construction machinery. [ABSTRACT FROM AUTHOR]

YC21-1 is a gas-bearing structure found within the Yanan sag in the Qiongdongnan Basin, South China Sea. While the structure bears many geological similarities to the nearby YC13-1 gas field, it nevertheless does not contain commercially viable gas volumes. The main reservoirs of the YC21-1 structure contain high overpressures, which is greatly different from those of the YC13-1 structure. The pressure coefficients from drillstem tests, wireline formation tests and mud weights are above 2.1. Based on well-log analysis, illite content and vitrinite reflectance data of mudstones in well YC21-1-2, combining with tectonic and sedimentation characteristics, the timing and causes of overpressure generation are here interpreted. The results indicate the existence of two overpressure segments in the YC21-1 structure. The first overpressure segment resides mainly within the lower and the middle intervals of the Yinggehai Formation, and is interpreted to have been mainly caused by clay diagenesis, while disequilibrium compaction and hydrocarbon generation may also have contributed to overpressure generation. The second overpressure segment comprising the Sanya Formation (Pressure transition zone) and the Lingshui and Yacheng Formations (Hard overpressure zone) is interpreted to owe its presence to kerogen-to-gas cracking. According to petrography, homogenization temperature and salinity of fluid inclusions, two stages of oil-gas charge occurred within the main reservoirs. On the basis of overpressure causes and oil-gas charge history, combining with restored tectonic evolution and fluid inclusion characteristics, a complex accumulation and leakage process in the YC21-1 gas bearing structure has been interpreted. Collective evidence suggests that the first oil charge occurred in the Middle Miocene (circa 16.3–11.2 Ma). Small amount of oil generation and absence of caprocks led to the failure of oil accumulation. Rapid subsidence in the Pliocene and Quaternary gave rise to a sharp increase in geotemperature over a short period of time, leading to prolific gas-generation through pyrolysis and, consequently, overpressure within the main reservoirs (the second overpressure segment). During this period, the second gas charge occurred in the Pliocene and Quaternary (circa 4.5–0.4 Ma). The natural gas migrated in several phases, consisting of free and water soluble phases in a high-pressure environment. Large amounts of free gas are considered to have been consumed due to dissolution within formation water in highly pressured conditions. Water soluble gas could not accumulate in high point of structure. When the pore-fluid pressures in main reservoirs reached the fracture pressure of formation, free gas could leak via opened fractures within cracked caprocks. A repeated fracturing of caprocks may have consumed natural gas stored in formation water and have made water-soluble gas unsaturated. Therefore, the two factors including caprocks fracturing and dissolution of formation water are interpreted to be mainly responsible for the failure of natural gas accumulation in the YC21-1 structure. [ABSTRACT FROM AUTHOR]

Hydraulic pitch systems provide robust and reliable control of power and speed of modern wind turbines. During emergency stops, where the pitch of the blades has to be taken to a full stop position to avoid over speed situations, hydraulic accumulators play a crucial role. Their efficiency and capability of providing enough energy to rotate the blades is affected by thermal processes due to the compression and decompression of the gas chamber. This paper presents an in depth study of the thermodynamical processes involved in an hydraulic accumulator during operation, and how they affect the energy efficiency of the component. An initial evaluation of the popular thermal time constant model is made and compared with experimental results for a 6  L accumulator, showing that the current estimation techniques for the thermal time constant are not suited for the application studied, predicting higher heat losses in the gas and resulting in lower pressure buildup. Furthermore, it is shown that the assumption of a constant value for the thermal time constant can provide extremely accurate results, provided that the compression ratios of the process are known in advance. For varying compression ratios, dynamical effects play an important role and the accuracy of the model decreases. To study the thermal processes, a simplified axisymmetric CFD model of the accumulator is developed. The results show that the main heat transfer losses are associated with heat diffusion in the solid parts of the accumulator, making up to 20% of the total heat losses. It is also shown that the heat transfer processes and the thermal time constant are tightly connected to variations in gas mass, in rate of change of volume and compression ratios. Comparison with experimental results validate the CFD model accurately, showing high level of agreement and repeatability between the predicted pressures and temperatures and the experimental measurements. [ABSTRACT FROM AUTHOR]

Long-pulse operation of the Wendelstein 7-X (W7-X) stellarator experiment is scheduled to begin in 2020. During this operational phase the vessel will be equipped with water-cooled plasma facing components to allow for longer pulse durations. Certain simulated plasma scenarios have been shown to produce heat fluxes that could surpass the technological limits of the divertor target elements during steady-state operation. To reduce the heat load on the target elements, the addition of a “scraper element” (SE) is under investigation. The SE is composed of 24 water-cooled carbon fiber reinforced carbon composite monoblock units. Multiple full-scale prototypes have been tested in the GLADIS high heat flux test facility. Previous computational studies revealed discrepancies between the simulations and experimental measurements. In this work, single-phase thermal-hydraulics modeling was performed in ANSYS CFX to identify potential causes for such discrepancies. Possible explanations investigated were the effects of a non-uniform thermal contact resistance and a potential misalignment of the monoblock fibers. While the difference between the experimental and computational results was not resolved by a non-uniform thermal contact resistance, the computational results provided insight into the potential performance of a W7-X monoblock unit. Circumferential temperature distributions highlighted the expected boiling regions of such a unit. Furthermore, simulations revealed that modest angles of fiber misalignment in the monoblocks result in asymmetries at the unit edges and provide temperature differences similar to the experimental results. [ABSTRACT FROM AUTHOR]

In many gravel-bedded rivers, floods that fill the channel banks create just enough shear stress to move the median-sized gravel particles on the bed surface (D50). Because this observation is common and is supported by theory, the coincidence of bankfull flow and the incipient motion of D50 has become a commonly used assumption. However, not all natural gravel channels actually conform to this simple relationship; some channels maintain bankfull stresses far in excess of the critical stress required to initiate sediment transport. We use a database of >300 gravel-bedded rivers and >600 10Be-derived erosion rates from across North America to explore the hypothesis that sediment supply drives the magnitude of bankfull shear stress relative to the critical stress required to mobilize the median bed surface grain size (τbf∗/τc∗). We find that τbf∗/τc∗ is significantly higher in West Coast river reaches (2.35, n = 96) than in river reaches elsewhere on the continent (1.03, n = 245). This pattern parallels patterns in erosion rates (and hence sediment supplies). Supporting our hypothesis, we find a significant correlation between upstream erosion rate and local τbf∗/τc∗ at sites where this comparison is possible. Our analysis reveals a decrease in bed surface armoring with increasing τbf∗/τc∗, suggesting channels accommodate changes in sediment supply through adjustments in bed surface grain size, as also shown through numerical modeling. Our findings demonstrate that sediment supply is encoded in the bankfull hydraulic geometry of gravel bedded channels through its control on bed surface grain size. [ABSTRACT FROM AUTHOR]

A fully coupled hydro-mechanical model based on the discrete element method has been built up to characterize the properties of fluid driven fractures. The rock mass is represented by a set of discrete elements interacting through elastic-brittle bonds that can break to form cracks which can coalesce to form fractures. The fluid flow between the elements is computed as a function of the dual pore space deformation in the intact medium and of the cracks' aperture in the fractures through a finite volume scheme. A series of hydraulic fracturing simulations were performed on intact specimens subjected to different loading conditions. The respective contributions of the matrix permeability, fluid compressibility, injection flow rate and state of stress are investigated while the effect of the distance between the perforation clusters, the wellbore-deviation from the minimum principal stress direction and the orientation of the injection slots for multiple injection treatments along a wellbore segment. For the analysis the evolutions of the P 33 (fracture volume) and P 32 (fracture intensity) indices are followed. The results show how, for a single injection treatment, P 33 and P 32 values can be affected by the state of stress inside the medium. Also, they show that aligning the perforation slots with the maximum horizontal stress direction might be a straightforward solution to optimize the opening of the induced fractures. [ABSTRACT FROM AUTHOR]

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The design of a super-capacitor-powered shape-memory-alloy (SMA) actuated accumulator for blowout preventer (BOP) presented in this paper featured several advantages over conventional hydraulic accumulators including instant large current drive, quick system response and elimination of need for the pressure conduits. However, the mechanical design introduced two challenges, the nonlinear nature of SMA actuators and the varying voltage provided by a super capacitor, for control system design. A cerebellar model articulation controller (CMAC) feedforward plus PID controller was developed with the aim of compensation for these adverse effects. Experiments were conducted on a scaled down model and experimental results show that precision control can be achieved with the proposed configurations and algorithms. [ABSTRACT FROM AUTHOR]

Considering the disadvantage of higher throttling loss for the open-circuit hydrostatic transmission at present, a novel gravitational potential energy regeneration system (GPERS) of the boom of hydraulic excavator, namely the closed-circuit GPERS, is proposed in this paper. The closed-circuit GPERS is based on a closed-circuit hydrostatic transmission and adopts a hydraulic accumulator as main energy storage element fabricated in novel configuration to recover the entire gravitational potential energy of the boom of hydraulic excavator. The matching parameter and control system design are carried out for the proposed system, and the system is modeled based on its physical attributes. Simulation and experiments are performed to validate the employed mathematical models, and then, the velocity and the pressure performance of system are analyzed. It is observed that the closed-circuit GPERS shows better velocity control of the boom and response characteristics. After that, the average working efficiency of the closed-circuit GPERS of boom is estimated under different load conditions. The results indicate that the proposed system is highly effective and that the average working efficiency in different load conditions varied from 60% to 68.2% for the experiment platform. [ABSTRACT FROM AUTHOR]

Ultrafiltration as a pretreatment for RO feedwater with enhanced UF backwash, which combines continuous with pulse backwash, was investigated in a novel UF-RO process integration. Direct supply of RO concentrate to the UF module served for UF backwash which was further enhanced with pulse backwash generated using bladder-type hydraulic accumulators. Model analysis of the hydraulic accumulator operation, which was validated via a series of field experiments, demonstrated a capability for accumulator charging directly from the RO concentrate stream within a period of 30–40 s. Moreover, pulse backwash over a short period (~5 s) which was added to the continuous UF backwash (directly from the RO brine stream), enabled peak UF backwash flux up to a factor of 4.2–4.6 higher than the normal filtration flux. The above mode of UF operation with multiple consecutive backwash pulses was more effective than with a single pulse, while inline coagulation further increased the UF performance. Relatively long-term field operation (over eight days where) of the UF-RO system with self-adaptive triggering of UF backwash, whereby the number of consecutive pulses increased when a higher membrane fouling resistance was encountered, was highly effective in enabling stable UF operation over a wider range of water quality conditions and without the need for chemical cleaning. These encouraging results suggest that direct UF-RO integration with enhanced pulse UF backwash is an effective approach for dead-end UF filtration without sacrificing water productivity. [ABSTRACT FROM AUTHOR]

Recent demands to reduce pollutant emissions and improve energy efficiency have driven the implementation of hybrid solutions in mobile machinery. This paper presents the results of a numerical and experimental analysis conducted on a hydraulic hybrid excavator (HHE). The machinery under study is a middle size excavator, whose standard version was modified with the introduction of an energy recovery system (ERS). The proposed ERS layout was designed to recover the potential energy of the boom, using a hydraulic accumulator as a storage device. The recovered energy is utilized through the pilot pump of the machinery which operates as a motor, thus reducing the torque required from the internal combustion engine (ICE). The analysis reported in this paper validates the HHE model by comparing numerical and experimental data in terms of hydraulic and mechanical variables and fuel consumption. The mathematical model shows its capability to reproduce the realistic operating conditions of the realized prototype, tested on the field. A detailed energy analysis comparison between the standard and the hybrid excavator models was carried out to evaluate the energy flows along the system, showing advantages, weaknesses and possibilities to further improve the machinery efficiency. Finally, the fuel consumption estimated by the model and that measured during the experiments are presented to highlight the fuel saving percentages. The HHE model is an important starting point for the development of other energy saving solutions. [ABSTRACT FROM AUTHOR]

Many studies have aimed to characterize pressurized transient hydraulics. However, it remains difficult to assess the importance of dynamic effects in a robust manner, and modeling is further complicated by the tension between computational efficiency and physical accuracy. To address such challenges for incompressible flows, this article presents an adaptive modeling approach that combines a novel hybrid formulation, termed the hybrid global gradient algorithm (HGGA), with a variable time step (VTS). The HGGA combines the generalized and rigid water column global gradient algorithms, so it can adapt to inertially-dominated flows and those without such effects. Computational efficiency and physical accuracy are balanced by adjusting the formulation according to the simulated hydraulics. Three physically-based indicators are then introduced to characterize unsteady flow: these actively inform the HGGA of how to model a system. Two pipe networks are used to demonstrate the current work. The first illustrates the utility of the inertial indicators, and the second comprises an extended period simulation with the VTS scheme. Although more computationally intensive than conventional modeling, the methodology is shown to provide a better representation of dynamic hydraulics. [ABSTRACT FROM AUTHOR]

This paper presents the modeling and control of a hybrid wind-tidal turbine with hydraulic accumulator. The hybrid turbine captures the offshore wind energy and tidal current energy simultaneously and stores the excess energy in hydraulic accumulator prior to electricity generation. Two hydraulic pumps installed respectively in wind and tidal turbine nacelles are used to transform the captured mechanical energy into hydraulic energy. To extract the maximal power from wind and tidal current, standard torque controls are achieved by regulating the displacements of the hydraulic pumps. To meet the output power demand, a Proportion Integration Differentiation (PID) controller is designed to distribute the hydraulic energy between the accumulator and the Pelton turbine. A simulation case study based on combining a 5 MW offshore wind turbine and a 1 MW tidal current turbine is undertaken. Case study demonstrates that the hybrid generation system not only captures all the available wind and tidal energy and also delivers the desired generator power precisely through the accumulator damping out all the power fluctuations from the wind and tidal speed disturbances. Energy and exergy analyses show that the energy efficiency can exceed 100% as the small input speeds are considered, and the exergy efficiency has the consistent change trends with demand power. Further more parametric sensitivity study on hydraulic accumulator shows that there is an inversely proportional relationship between accumulator and hydraulic equipments including the pump and nozzle in terms of dimensions. [ABSTRACT FROM AUTHOR]

Wave power in China has an energy density that is one-tenth of that of the wave power in Europe. Therefore, Chinese developers cannot simply replicate and transplant European devices and facilities to East Asia. Instead, to exploit the conditions in East Asia, a combined-oscillating-buoy-based wave energy convertor (WEC) is proposed as an array-type WEC. Sea trials of a 10 kW pilot device confirmed the feasibility of its buoy array and hydraulic pressure system (HPS) for wave-energy conversion. Field test data indicated that the energy-converting efficiency of the direct-drive design was relatively low, suggesting the urgency of developing energy storage systems to the increase of power take-off productivity. A hydraulic accumulator system (HAS) was designed to replace the original direct-drive operating mechanism for a 100 kW final-prototype device. It was expected that the system will exhibit an improved ability to collect and store energy from smaller waves to enhance the total converting efficiency. Experimental studies were performed to investigate the hydrodynamic characteristics of the heaving buoys under the damping effects, and the operating performance of the accumulator system. A numerical wave-to-wire model based on Simulink, Matlab was set-up to study the energy output of the HPS-HAS under the wave conditions of the test site. It was shown that four buoys could charge ten accumulators in half an hour under local actual sea conditions. Furthermore, in a same running time, the output energy of the HPS-HAS is over forty times larger than that of the HPS without any energy storage device. In addition, energy discharging from three accumulators only could reach about 20 kW output power. The numbers of buoys and accumulators should be optimized to improve wave-energy storage and power generation in the future. [ABSTRACT FROM AUTHOR]

The fault diagnosis of hydraulic pumps is currently important and significant to ensure the normal operation of the entire hydraulic system. Considering the nonlinear characteristics of hydraulic-pump vibration signals and the mode mixing problem of the original Empirical Mode Decomposition (EMD) method, first, we use the Complete Ensemble EMD (CEEMD) method to decompose the signals. Second, the time-frequency analysis methods, which include the Short-Time Fourier Transform (STFT) and time-frequency entropy calculation, are applied to realize the robust feature extraction. Third, the multiclass Support Vector Machine (SVM) classifier is introduced to automatically classify the fault mode in this paper. An actual hydraulic-pump experiment demonstrates the procedure with a complete feature extraction and accurate mode classification. [ABSTRACT FROM AUTHOR]

Hydraulic accumulators are used as energy storages in a wide area of applications. In particular, in automotive hybrid drive-trains, this type of energy storage is an interesting alternative to today’s common strategies like chemical batteries or flywheels. This article deals with the mathematical modelling of a hydraulic accumulator for passenger vehicles, which comprises a carbon fibre reinforced plastic (CFRP) body and aluminium piston. The thermodynamical behaviour of the oil and gas as well as the interaction with the CFRP body is investigated in detail. Starting from a complex model, two models of reduced complexity are derived. The validation of these models with measurement data from a test drive with a prototype series hydraulic hybrid drive-train proves their high accuracy. [ABSTRACT FROM AUTHOR]

An evolution from traditional hydraulic, pneumatic and mechanic components into general electrical system in the airplane featuring an extensive usage of electro-mechanical actuator has been in the spotlight for the last decade. The widespread availability of such actuators which are commonly driven by permanent magnet synchronous motors will, on the one hand, enhance an overall operating economy, yet on the other hand, it will post a newly generated challenge for the current on-board thermal control system since a large amount of waste heat will produce accompanied with the operation of these motors. An ineffective heat rejection path will cause an overheating inside the motors which will lead to a permanent damage easily. It is intolerable for an air-oriented complexity where the reliability, longevity and robustness are the top three priorities. Based on the operating characteristics of the on-board motors, a novel phase change material based motor packaging technology exploiting its huge latent heat is proposed in this paper. Thermal experiments were conducted to analyse the superiority of the proposed strategy quantitatively compared with the conventional fin-based packaging scheme in both constant and intermittent heat generation modes. Systematic design criteria, optimization, performance prediction, etc. were attained via dimensionless studies that aims to acquire a high applicability for more extensive occasions, which is remarked by the discovery of two critical dimensionless factors. [ABSTRACT FROM AUTHOR]

In this study, the thermo-hydraulic performance of rectangular duct roughened with a new configuration of periodic rib, broken arc rib combined with staggered rib piece on one broad wall is determined for flow Reynolds number range of 2000 to 16000. The roughened wall is uniformly heated while the remaining three walls are insulated. These boundary conditions correspond closely to those found in solar air heaters. The channel aspect ratio was 12. Four broken arc rib combined with staggered rib roughened plates having relative staggered rib position of 0.2, 0.4, 0.6 and 0.8 have been tested. The other roughness parameters such as the relative gap width, arc angle, relative gap position, relative staggered rib size, relative roughness pitch and relative roughness height were fixed as 1.0, 30°, 0.65, 5.0, 10 and 0.043 respectively. The Nusselt number and friction factor is found to be more at relative staggered rib position of 0.6 than at other relative staggered rib positions. The thermo-hydraulic performance is found to be more for relative staggered rib position of 0.6. The highest value of thermo-hydraulic performance is 2.25 corresponding to Reynolds number of 12000, as compared to 1.98 for broken arc rib roughened duct. [ABSTRACT FROM AUTHOR]

For the purpose of lowering the cost of metal hydride electrode, the La of LaYNi electrode was replaced by Ce. The electrochemical performances of the CeYNi negative electrode, at a room and different temperatures, were compared with the parent alloy LaYNi. At room temperature during a long cycling, the evolution of the electrochemical capacity-the diffusivity indicator ( $$ \frac{D_{\mathrm{H}}}{a^2} $$ )-the exchange current density, and the equilibrium potential were determined. At different temperatures, the electrochemical characterization of this alloy allowed the estimation of the enthalpy, the entropy, and the activation energy of the hydride formation. The evolution of the high-rate dischargeability was also evaluated at different temperatures. Compared with the parent LaYNi alloy, CeYNi exhibits an easy activation and good reaction reversibility. This alloy also conserves a good lifetime during a long-term cycling. A lower activation energy determined for this alloy corresponds to an easy absorption of hydrogen into this new alloy. [ABSTRACT FROM AUTHOR]

This study proposes the concept of subsea production systems with a seabed storage tank to provide an alternative to conventional floating facilities and performs the reliability, maintainability and availability study for the seabed storage tank. The reliability assessment of the seabed storage tank performs a four-step procedure. A four-step procedure is to define the system boundary, collect the reliability data, construct a fault tree and estimate the reliability. The failure and repair data are obtained from the component of the lowest level of the seabed storage tank because the seabed storage tank is a new system unknown reliability data. Reliability of the seabed storage tank is estimated with a consideration of critical events. The total failure frequency of the SST is estimated approximately 2.27· 10 −4 /hour. The maintainability analysis is estimated in accordance with MIL-HDBK 472 Procedure V. The elements of repair time is obtained from the subsea JIP 2000 and RAM study of field data. Active repair time from OREDA 2009 is regarded as the repair/replace of repair time elements. The total repair time is mainly effected by the preparation time of repair time elements. The system availability for the seabed storage tank under normal operation is calculated as approximately 91.8%. [ABSTRACT FROM AUTHOR]

Two tests related to a new safety system for a pressurized water reactor were performed with the ROSA/LSTF (rig of safety assessment/large scale test facility). The tests simulated cold leg small-break loss-of-coolant accidents with 2-inch diameter break using an early steam generator (SG) secondary-side depressurization with or without release of nitrogen gas dissolved in accumulator (ACC) water. The SG depressurization was initiated by fully opening the depressurization valves in both SGs immediately after a safety injection signal. The pressure difference between the primary and SG secondary sides after the actuation of ACC system was larger in the test with the dissolved gas release than that in the test without the dissolved gas release. No core uncovery and heatup took place because of the ACC coolant injection and two-phase natural circulation. Long-term core cooling was ensured by the actuation of low-pressure injection system. The RELAP5 code predicted most of the overall trends of the major thermal-hydraulic responses after adjusting a break discharge coefficient for two-phase discharge flow under the assumption of releasing all the dissolved gas at the vessel upper plenum. [ABSTRACT FROM AUTHOR]

The newest European high performance material testing reactor, the Jules Horowitz Reactor, will support existing and future nuclear reactor designs. The reactor is under construction at CEA Cadarache research center in France and is expected to start operation at the end of this decade. This paper presents a Computational Fluid Dynamics simulation of the reactors hot fuel element. Moreover conjugate heat transfer analysis is performed for the hot channel. The main objective of this work is to improve the thermal-hydraulic knowledge of the complex hot fuel element and to present the most prominent finds. Possible improvements for the future work are suggested. [ABSTRACT FROM AUTHOR]

Run-of-the-river hydropower is a typical form of power generation in mountainous regions. This study investigates the velocity field upstream of Aberfeldie dam, a run-of-the river facility on the Bull River nearWardner, British Columbia, Canada. As is typical for these types of run-of-the river facilities, the headpond of this dam is very shallow(approximately 1mdeep) because of long term sediment deposition. Near the facility's power intakes, a large scour hole has been created because of increased velocities induced by the intakes. This study conducted field measurements and developed a computational fluid dynamic (CFD) model to investigate the velocity field under various flow conditions. The CFD solver shows in a simplistic way that flow-induced bed shear stress likely causes a fluctuating, dynamic bed form that varies by season and the distance upstream, so that a consistent velocity pattern is seen across the entire headpond. The velocity field generated by the CFD solver is used to evaluate the entrainment risk of mountain whitefish and westslope cutthroat trout based on swimming mechanics and life stage. The unique habitat conditions generated by the scour hole act as an attractant to the high risk zone, greatly increasing fish density adjacent to the intakes at this facility. [ABSTRACT FROM AUTHOR]

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Peatland drainage and peat extraction result in runoff water rich in humus, sediments, and nutrients that requires simple purification methods to prevent pollution of surface waters. Chemical treatment of drainage water has been suggested as best management practice. However, good chemical purification results require flocculators to achieve efficient particle aggregation. This study evaluated gravity-driven hydraulic flocculators using full-scale three-dimensional (3D) computational fluid dynamic (CFD) turbulence models to simulate hydraulics, combined with data obtained in jar tests to estimate optimal mixing conditions for coagulation [velocity gradient (G-values)]. The CFD model was first run for several barrier configurations. The optimal structure was then tested for different ratios of distance between barriers [or opening slot width (B)] and flocculator width (W). The relationship between distribution of G-values and the target value of 40-60 s-1 was determined for different designs. The best B/W ratio was found to be 1/4. For this ratio, the flow depth was the only variable parameter that needed to be optimized by the CFD model to achieve target G-values. [ABSTRACT FROM AUTHOR]

In this study, a thermodynamic analysis of a hydraulic braking energy recovery system used in vehicles is performed for newly developed systems. The present system is related to the field of energy efficiency in vehicles. The energy recovery system comprises a first pump, a hydraulic accumulator, and a hydraulic motor. The first pump is a variable displacement hydraulic pump (VDP). The hydraulic accumulator is connected to the first pump which operates to store hydraulic fluid under pressure. The hydraulic motor is hydraulically connected to the accumulator to receive hydraulic fluid. The motor is adapted to drive a second hydraulic pump, which is hydraulically connected to the auxiliary system, using hydraulic energy stored in the accumulator. The overall charging and discharging efficiencies, and the overall system efficiency is calculated and presented in this paper. For the purpose of the analysis, EES (engineering equation solver) is used. In addition, parametric studies are performed to observe the effects o f different substantial parameters, namely, the inlet pressure and temperature o f the accumulator, and the reference environment temperature, in order to investigate the variations in the system performance in terms of the efficiencies. Two systems are developed and it is found that the charging and discharging efficiencies for one system are 83.81% and 87.73%, while for the other system the charging and discharging efficiencies are 81.84% and 85.67%, respectively. [ABSTRACT FROM AUTHOR]

Dam Modrac is multiple arched reinforced concrete buttress dam, with nine buttresses and ten arches, which by its technical characteristics and volume of the accumulation is considered as one of the high dams. Crown level of spillway is 200.00 m a.s.l. Crest length is 205.00 m, while the maximum height is 27.50 m. To control the water level in the reservoir, under normal hydrological conditions, there are four basic discharges with maximum capacity around Q = 77 m³/s for the projected state. The paper gives an analytical expression of the spillway curve and analytical expressions of amounts of water discharge separately for each bottom outlet, which are obtained by conducted measurings. Special significance of this paper gives volume curves for hydro accumulation Lake Modrac for projected state and the period of use of the system. [ABSTRACT FROM AUTHOR]

In this work, an automated statistical analysis of vibration characteristics for the condition monitoring of hydraulic systems is proposed. Features from FFT vibration data of a micromechanical accelerometer measured at the gear pump are extracted, selected by their correlation coefficient to the target fault value, and subsequently reduced to discriminant functions which allow the classification of component conditions using multivariate statistics. The approach was successfully evaluated with an experimental hydraulic test bench simulating typical fault scenarios like valve switching degradation or gas leakage of the accumulator. It was shown that the studied fault scenarios can be selectively detected (internal pump leakage) and even quantified concerning the grade of severity in case of valve switching degradation, accumulator gas leakage, and oil aeration. Furthermore, the long-term stability of the statistical model was evaluated over several weeks. [ABSTRACT FROM AUTHOR]

One of the most widespread methods to increase the power of internal-combustion engines (ICEs) is turbocharging. But turbochargers used for 70% of engines have a number of essential disadvantages: their low service reliability as up to 30% of engine failures are caused by turbochargers; their high price; their cost-demanding reconditioning caused by high labour inputs and considerable downtime periods of machine-tractor units; losses due to long downtime periods of machine-tractor units. ICE life reducing usual for those equipped with turbochargers is due to frequent high-temperature overloads abnormal for turbochargers. To reduce the thermal factor of turbocharger elements and the running-out durability can be possible when using a hydraulic accumulator and a braking device. Thus, a test bench is manufactured for examining the turbocharger with the proposed elements. As a result, we manage to avoid semidry and dry friction to extend the turbocharger life, with the rotor slowing time being reduced on average up to 30–35% as compared with the normal (load-free) rotor slowing time. Thus, a hydraulic accumulator combined with a braking device can reduce turbocharger failures up to 10–15%. [ABSTRACT FROM AUTHOR]