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The relevance of the study is associated with the need to implement the concept of the scientific and technological development of the Russian Federation, which outlines the transition to environmentally friendly and resource-saving technologies. The paper presents the results of full-scale experiments of changes in the operating parameters of the experimental-industrial hybrid solar hot-water system with a circulating pump operating in periodic duty mode in the hydraulic circuit. The proposed hardware and software system provides switching on and switching out of the circulating pump depending on the temperature difference of the coolant in collectors and at the storage tank output. This provides the maximum thermal energy for the hot-water system at different of solar radiation intensities and the minimum power consumption by the circulating pump generated by solar panels.

As obras subterrâneas encontram-se associadas aos aproveitamentos hidroelétricos nos seus elementos principais: na barragem, contribuindo na satisfação das exigências de comportamento estrutural e hidráulico-operacional, e na central e circuito hidráulico, como elementos fundamentais do sistema hidráulico que possibilita a produção de energia. Neste artigo, são focadas obras subterrâneas realizadas, ao longo de um século, nos grandes aproveitamentos hidroelétricos de Portugal, dando-se destaque às obras consideradas mais relevantes pelo seu layout ou pelas suas características específicas. Nas obras mais recentes, é dada relevância a aspetos relacionados com análises numéricas, segurança, monitorização estrutural e ambiental, estratégias e métodos construtivos.

This paper presents the modeling and analysis of a novel priority valve controlled open-loop Cable Reeling Drum (CRD) drive of Load Haul Dump (LHD) vehicle. The LHD vehicle is basically a trackless loading machine having wide applications in underground mining operations. The CRD incorporated in the said machine performs the reeling/unreeling operation of the flexible trailing cables that supply electric power to the machine. In this respect, a novel hydraulic circuit is proposed that incorporates a priority valve for the operation of the hydro motor driving the CRD, unlike the existing LHD machines having a separate hydraulic arrangement for the CRD operation. In the present study, the flow through the bypass port of the priority flow divider (PFD) valve is utilized for driving the CRD. In analyzing the proposed hydraulic system, the detailed model is analytically solved in MATLAB/Simulink software, and the simulation results are validated experimentally. The effects of change of the critical parameters on the system's dynamic responses are analyzed using the validated simulation model. The investigations show that till the fluid flow metered to the PFD valve is higher than the priority flow demand, the machine's priority function is not affected by the operation of the CRD. However, with the actuation of the priority operation, the hydro-motor drive speed of the CRD decreases. The model proposed in this study may be considered as a basis for the re-design of the hydraulic arrangement of CRD drive incorporated in an LHD machine for its improved performance.

The presented study in this paper is concerned with the performance of an orifice meter handling water-polymer solution, water-sand mixture (two-phase flow), and water-sand mixture with polymer additives (two-phase non-Newtonian flow). An ASME recommendation orifice meter was constructed and installed in a hydraulic circuit. Sand of different grain sizes (0.063-0.125, 0.125-0.25 and 0.25-0.5 mm) with concentrations 0.25%, 0.5%, 1.0% and 1,5% by weight was tested. One type of polymers (polyacrylamid) was used with an average concentrations of 20, 30 and 40 wppm. The results show that both polymer and sand concentrations affects the coefficient of discharge of the orifice meter. The coefficient of discharge was found to be increased with increasing polymer concentration, while increasing sand concentration decreases the coefficient of discharge. The used sand grain sizes has no effect on the coefficient of discharge.

The presented study in this paper is concerned with the performance of an orifice meter handling water-polymer solution, water-sand mixture (two-phase flow), and water-sand mixture with polymer additives (two-phase non-Newtonian flow). An ASME recommendation orifice meter was constructed and installed in a hydraulic circuit. Sand of different grain sizes (0.063-0.125, 0.125-0.25 and 0.25-0.5 mm) with concentrations 0.25%, 0.5%, 1.0% and 1,5% by weight was tested. One type of polymers (polyacrylamid) was used with an average concentrations of 20, 30 and 40 wppm. The results show that both polymer and sand concentrations affects the coefficient of discharge of the orifice meter. The coefficient of discharge was found to be increased with increasing polymer concentration, while increasing sand concentration decreases the coefficient of discharge. The used sand grain sizes has no effect on the coefficient of discharge.

Leakage is one of the most important reasons for failure of hydraulic systems. The accurate positioning of leakage is of great significance to ensure the safe and reliable operation of hydraulic systems. For early stage of leakage, the pressure of the hydraulic circuit does not change obviously and therefore cannot be monitored by pressure sensors. Meanwhile, the pressure of the hydraulic circuit changes frequently due to the influence of load and state of the switch, which further reduces the accuracy of leakage localization. In the work, a novel Bayesian networks (BNs)-based data-driven early leakage localization approach for multi-valve systems is proposed. Wavelet transform is used for signal noise reduction and BNs-based leak localization model is used to identify the location of leakage. A normalization model is developed to improve the robustness of the leakage localization model. A hydraulic system with eight valves is used to demonstrate the application of the proposed early micro-leakage detection and localization approach.

The use of solar energy in isolated sites for different applications, such as water pumping, is of primary interest to people in developing countries who do not have safe access to water drinking. But photovoltaic generators have two major drawbacks that are a low yield and a high blow. In order to increase the performance of these systems. Proper adaptation between the solar generator and the load reduces the cost of installation. The choice of an energy system must obey and comply with certain rules. The selected energy system must show as a preliminary its competitiveness with respect to other systems for the same rendered service. The present study have a propose the modeling, simulation, sizing and realization of a photovoltaic pumping system operating over the sun. This system consists of a set of interacting elements; namely the photovoltaic panels, the voltage inverter, the asynchronous motor, the centrifugal pump and the hydraulic circuit.

The author aimed to develop an analytical solution to the problem of the load flow of a six-, eleven- and twelve-circuit heat network, as well as to solve the problem of optimisation of a multi-circuit heat network, including the choice of the objective function and the determination of a number of variable technical parameters. For accelerating the optimisation process, the method of decomposition of the heat network graph was used. Decomposition involves is cutting the network graph at some nodes for the transition of a multi-circuit scheme to a branched scheme in the form of a tree. Optimisation of each branched circuit was carried out by the dynamic programming method, as a result of which new values of the variable parameters were obtained at the current iteration. Next, the author returned to the multi-circuit scheme to solve the load flow problem and calculate the value of the objective function. The iterative convergence of the decomposition method was not mathematically proven. The author proposed a method for splitting the graph, which eliminates the decomposition procedure when optimising a heat network. The following methods were applied: mathematical modelling of the hydraulic circuit, graph splitting method and the analytical method for solving the algebraic equation of the fourth degree. The following results were achieved: a scheme of the minimum element of a multi-circuit heat network was determined, the possibility of series and parallel circuits of minimum elements was shown, and analytical dependencies for the problem of load flow of a heat network of these schemes were obtained. The proposed analytical solution of the load flow problem for a multi-circuit heat network allows the problem of calculating a complex network to be reduced to the calculation of several minimum elements, which significantly reduces the amount of computational work when modelling a hydraulic circuit. The provided examples show that the calculation error does not exceed 3%.

The paper presents algebraic mathematical models of centrifugal mechanisms that operate in the power boiler gas-hydraulic circuit. The models have been built by means of head-flow curve approximation. The head-flow curve depends on the centrifugal mechanism blade rotating speed and guide vane angle. The least squares method has been applied for centrifugal mechanism head-curve approximation on the basis of experimental or numerical data. Different configurations for the connections of centrifugal mechanisms in the power boiler gas-hydraulic circuit have been considered, relationships for their performance assessment obtained, and efficiency factors for various methods of their capacity control introduced. The state equation for a complex gas-hydraulic network in the problem of its efficiency analysis has been obtained with application of Kirchhoff laws. Numerical algorithms have been developed to solve group control parameter optimization problems for the considered connections of centrifugal mechanisms. Features of mathematical models for groups of series-, parallel- and complex-connected centrifugal mechanisms with different head curves in the power boiler maintenance system have been specified. An optimal group control problem for a group of centrifugal mechanisms has been formulated and solved under various power boiler modes. For the feed pumps, individual frequency control proves to be the most effective method, while for the boiler draft mechanisms group frequency regulation turns out to be the most efficient. In a typical summer month, implementation of energy-efficient centrifugal mechanism capacity regulation method in a Thermal Power Plant is shown to result in auxiliary electricity consumption reduction by 10.96 % as compared with available actual data.

Purpose. The aim of this work is to develop an effective solar hot water system, which eliminates the heat loss of the accumulated thermal energy in the storage tank due to the natural convection of the coolant in the hydraulic circuit of collectors.Design technique. A fullscale experimental study concerns the negative effect of natural convection at night in the experimental industrial hybrid solar hot water system in the developed hard and software with remote access.Results. The pilot industrial hybrid solar system with the improved hydraulic circuit and a soft and hardware system for dispatching and managing energy consumption with remote access was developed, built and tested for Northern territories.Practical implications. The hydraulic circuit of collectors equipped with a controller for switching off the coolant provides the northern conditions to increase the thermal energy in storage tanks and the solar fraction of hot water systems, reduce the fuel consumption in additional system sources and the emission of harmful substances produced by the fuel combustion.Originality/value. It is shown that the use of a solenoid valve to eliminate the natural convection increases the thermal energy storage in tanks by at least 50 % and the solar fraction of systems by at least 20 %.

The work examines the hydraulic circuit of the cooling system of power plants of various purposes on the basis of the internal combustion engines. Experimental data are provided to ensure the necessary high pressure in the high-temperature cooling system at the exit of the internal combustion engines. The results of the stand tests are analysed and some recommendations have been proposed for their use to improve the efficiency of the power plant itself by improving its operational efficiency

Domestic and industrial hydraulic drainage networks have gradually become more complicated because of the cities’ rapid expansion. In surcharged hydraulic systems, the head losses may become rather significant, and should not be neglected because could result in several problems. This work presents an investigation about major and minor head losses in a hydraulic flow circuit, simulating the water transport in a drainage network at room temperature (298.15 K) under atmospheric pressure (101,325 Pa). The losses produced by the fluid viscous effect through the one used cast-iron rectilinear pipe (RP-11) and the localized losses generated by two flow appurtenances, one fully open ball valve (BV-1) and one module of forty-four 90º elbows (90E-8) were experimentally measured. Experimental data generated head-loss curves and their well fitted to potential regressions, displaying correlation coefficients (R2) of 0.9792, 0.9924, and 0.9820 for BV-1, 90E-8, and RP-11, respectively. Head loss experimental equations and local loss coefficients through BV-1 and 90E-8 were determined successfully. The Moody’s diagram application proved to be a quite appropriate tool for an approximate estimation of Darcy-Weisbach friction factor. A good approximation between friction factor values obtained via experimental measurements and the Moody’s diagram was observed with mean absolute deviate of 0.0136.

Magnetic refrigeration systems are promising cooling solutions that employ the active magnetic regenerator refrigeration cycle to achieve practical temperature spans and environmental benefits. The hydraulic system that ensures a continuous flow of the heat transfer fluid through the system with a reciprocating flow in each regenerator bed is critical to the performance of the refrigeration cycle. Hence, we investigate the characteristics of the parallel flow circuit of a rotary active magnetic regenerator system, which consists of thirteen trapezoidshaped regenerators, each filled with 295 g of gadolinium spheres. Fluid flow is controlled via electrically actuated solenoid valves (both piloted and direct-acting) connected to the regenerator hot side. By varying the percentage of opening of the control valves, different blow fractions (or fluid flow waveforms) could be investigated. The objective of the study is twofold: (i) assess whether flow imbalances of the heat transfer fluid exist in the cold-to-hot blow (cold blow) and hot-to-cold blow (hot blow) directions, and (ii) determine whether there is an optimal value of the blow fraction both to maximize the cooling performance and realize a rapid temperature pulldown. Flow resistance measurements demonstrate a symmetric flow circuit design and resistances that are similar in the cold and hot blow directions. Moreover, for the studied temperature spans of 6 K and 16 K, the best blow fraction was found to be about 41.6 %. For instance, at a 16 K span, a utilization of 0.32, and at 1.4 Hz, increasing the fluid blow fraction from 25.0 to 41.6 % enhanced the cooling capacity and second-law efficiency from 70 to 330 W and from 2.6 to 17.4 %, respectively. In turn, lower blow fractions favored a more rapid temperature pulldown. The magnetocaloric system was about 30 % faster in establishing approximately 14 K temperature span when the blow fraction was reduced from 41.6 to 30.6 %. Hence, magnetic refrigeration systems can benefit greatly from solenoid valves, which allow the system to operate either in a time-saving mode or an energy-saving mode.

Swift vaccination is necessary as a response to disease outbreaks and pandemics, otherwise, the species under attack is at risk of a high fatality rate or even mass extinction. Statistics suggest that at least 16 billion injections are administered worldwide every year. Such a high rate of needle/syringe injection administration worldwide is alarming due to the risk of needle-stick injuries, disease spread due to cross-contamination and the reuse of needles, and the misuse of needles. In addition, there are production, handling, and disposal costs. Needle phobia is an additional issue faced by many recipients of injections with needles. In addition to a detailed literature review highlighting the need for needle-free injection systems, a compressed air-driven needle-free jet injection system with a hydro-pneumatic mechanism was designed and developed by employing an axiomatic design approach. The proposed injection system has higher flexibility, uninterrupted force generation, and provides the possibility of delivering repeated injections at different tissue depths from the dermis to the muscle (depending on the drug delivery requirements) by controlling the inlet compressed air pressure. The designed needle-free jet injector consists of two primary circuits: the pneumatic and the hydraulic circuit. The pneumatic circuit is responsible for driving, pressurizing, and repeatability. The hydraulic circuit precisely injects and contains the liquid jet, allowing us to control the volume of the liquid jet at elevated pressure by offering flexibility in the dose volume per injection. Finally, in this paper we report on the successful design and working model of an air-driven needle-free jet injector for 0.2–0.5 mL drug delivery by ex vivo experimental validation.

To improve the roadway adaptability and control accuracy of anchoring equipment, a stepping anchoring device was designed. A permanent-magnet synchronous motor control and a harmonic suppression algorithm were integrated to optimize the dynamic control system of stepping-type anchoring equipment. The results of an experimental simulation and analysis showed that when the coefficient of coal rock hardness f = 5, 6, and 7, the pulsation coefficient of the hydraulic pump outlet pressure, hydraulic motor output speed, and pump-controlled hydraulic cylinder advance speed in the hydraulic circuit of a pump-controlled motor did not exceed 3% after the equipment based on sliding mode control (SMC) entered the steady state, while the maximum pulsation coefficient was only 32.5% of the PI control. Based on the SMC, the harmonic components of the permanent magnet synchronous motor in the power system were suppressed and compensated for. This enhanced the stiffness of the hydraulic system under motor drive. When the rock stiffness factor gradually changed from f = 5 to f = 8 and increased suddenly from f = 5 to f = 6, the pressure overshoot at the outlet of the hydraulic pump of the pump-controlled motor system was reduced from 11.19% to 7.97% and from 61.19% to 52.88%, respectively, compared with that before the optimization. It was thereby proven that SMC based on harmonic suppression can effectively reduce the system pulsation caused by the multi-factor coupling of anchoring equipment and provide technical support for the optimal control of the power system of stepping-type anchoring equipment.

A alteração de rochas e juntas provoca variações nas características geotécnicas do maciço rochoso, reduzindo a sua resistência e a segurança das obras de engenharia. O processo de alteração química introduz modificações do material, alterando o comportamento geomecânico originalmente previsto no projeto. A previsão do comportamento das rochas ao longo do tempo é de grande importância para que seja elaborado o plano de manutenção ou de reforço do material rochoso. Este artigo apresenta um estudo detalhado sobre a variação do comportamento mecânico das juntas e dos maciços de rocha gnáissica que compõem o circuito hidráulico do Aproveitamento Hidrelétrico Simplício, em função da alteração natural ao longo do tempo. Foram realizados ensaios com Martelo Schmidt no campo, em rocha nos estados alterado e inalterado e em juntas alteradas, e em laboratório, em rochas e juntas nos estados alterado e inalterado. Os ensaios com Martelo Schmidt mostraram inúmeras vantagens de seu uso na prática, tais como custo reduzido, rapidez, e facilidade de execução. Além disso, o ensaio com martelo mostra versatilidade de aplicação em amostras diversas, com restrições mínimas de área, volume e qualidade da superfície. A análise de outros estudos com o mesmo material de Simplício possibilitou a proposição de relações empíricas para a previsão de comportamento do material em função do tempo de alteração, do valor de rebote do martelo e da resistência à compressão uniaxial.

Active façade systems incorporating solar thermal collectors currently offer very promising energetic solutions. From among the available systems, a simple solution is the unglazed heat collector for potential integration in low-temperature applications. However, when adopting system definitions, the modification of some design parameters and their impact has to be fully understood. In this study, the case of an unglazed collector integrated into a sandwich panel is assessed and a specific analysis is performed for a proper assessment of the influence of key design parameters. Based on that case study of the real built system, a CFD model is developed and validated and a parametric assessment is then performed, by altering the configurations of both the panel and the hydraulic circuit. In this way, the potential of each measure to harness solar energy can be evaluated and each parameter with its different level of impact can be highlighted, to identify those of higher relevance. A characterization of the real solution completes the study, by providing the efficiency curves and the total energy collected during the experimental campaign. The maximum estimate of the efficiency of a 6 m2 façade was within a range between 0.47 and 0.34 and the heat loss factor was between 4.8 and 7.5. The case study exercises reveal the real energy efficiency and solar production patterns. There was also an opportunity to consider significant improvements to increase the output of the active façade. The main conclusions concerned the different criteria that improved the definition of the system and greater comprehension of alternative designs that may be integrated in the underlying concept. The authors are grateful to the Basque Government for fundingthis research through projects IT781-13 and IT1314-19 and to allthose involved in the different stages for their guidance andinvaluable help.The authors would also like to thank all those companies andresearchers participating in the BASSE project for their stronginvolvement during that research. Results from BASSE project haveinspired present research. The BASSE project received funding fromthe European Union, RFCS Program, Research Fund for Coal and Steel project Building Active Steel Skin (BASSE, Grant Agreement noRFSR-CT-2013-00026)

In order to study the speed ratio regulation and dynamic change of hydraulic mechanical continuously variable speed tractor, it is necessary to comprehend the dynamic characteristics of the hydraulic circuit. The identification method was adopted to study the pump-motor system of transmission. Firstly, the typical identification method of combination modeling was selected to establish the model, and then the corresponding experiments were designed to determine the transfer function parameters and models of the combined modeling. Based on these, through further simplification and indirect methods, with the help of MATLAB toolbox, a fast system identification method was established by calculating the transmission ratio of the pump motor system through the output speed of the gearbox, the engine speed and the drive ratio of the front gear of the pump, as well as the transmission ratio of the gearbox. Filter was used to remove the influence of noise during the experiment. Compared with the test data, the models established by the two identification methods have higher accuracy. The positive and negative fitting rates of the fast identification method are 91.85 and 91.13, respectively, which can meet the needs of subsequent research. This study can be used as a reference for the subsequent control design of transmission and the study on the quality of the transmission.

Starting in 2010, work is being underway at NIIEFA on developing the air-cooling system for Fast Discharge Resistors (FDR). The first attempts have been unsuccessful. The free-convective cooling method taken as the basis, though being simple and appealing, could not ensure complete cooling of all modules within the required 3–4 h. The reason was that the obtained distribution of the air flow over separate resistive modules composing the parallel cooling branches was strongly nonuniform. Repeated attempts to equalize the air flows (increase in the flow-through section of supply/return air ducts, division of the single cooling circuit into groups of separate circuits) were unsuccessful: the cooling time was decreased, but the required 3–4 h were not attained. The presented work continues the previously performed analyses of the versions of the cooling system for the FDRs. This paper presents the results of the analysis of the forced cooling of the resistors by fans installed in the inlet section of the air duct. The possibilities are studied to ensure equal flow rates in parallel modules of the hydraulic circuit. The method has been developed for equalizing the flow rates in the modules and selection of relevant hydraulic characteristics of diaphragms, making it possible to attain the specified time for cooling of FDR resistive elements.

The InWave wave energy converter (WEC), which is three-tether WEC type, absorbs wave energy via moored cylindrical buoys with three ropes connected to a terrestrial power take-off (PTO) through a subsea pulley. In this study, a simulation study was conducted to select a suitable PTO when designing a three-tether WEC. The mechanical PTO transfers energy from the buoy to the generator using a gearbox, whereas the hydraulic PTO uses a hydraulic pump, an accumulator, and a hydraulic motor to convert mechanical energy into electrical energy. The hydraulic PTO has a lower energy conversion efficiency than that of the mechanical PTO owing to losses resulting from pipe friction and the individual efficiencies of the hydraulic pumps and motors. However, the efficiencies mentioned above are not the efficiency of the whole system. The efficiency of the whole system should be analyzed considering the tension of the rope and the efficiency of the generator. In this study, the energy conversion efficiencies of the InWave WEC installed the mechanical and hydraulic PTO devices are compared, and their behaviors are analyzed through numerical simulations. The mechanics of mechanical and hydraulic PTO applied to InWave are mathematically expressed, and the issues of the elements constituting the PTO are explained. Finally, factors to consider for PTO selection are presented.

The earcanal mechanical deformation induced by the temporomandibular joint movement constitutes a promising source of energy to power in-ear devices (hearing aids, communication earpieces, etc.). The large morphological variability of the human earcanal and its intrinsic dynamic characteristics - with displacement frequencies below 1.5 Hz with average volume variation of 60 mm3 - motivate the development of non-conventional dedicated energy harvesting methods. This paper demonstrates the concept and design of a modular hydraulic-piezoelectric self-actuated frequency up conversion micromachine for energy harvesting. The mechanical energy is conveyed using a liquid-filled custom fitted earplug, which can be considered as a hydraulic pump. A dedicated hydraulic circuit drives two micro-pistons (MP) while ensuring the impedance matching between the earplug available pressure and swept volume and the MP required displacement and force. These MP actuate a mechanical oscillator associated to a piezoelectric transducer allowing the low frequency mechanical excitation to be efficiently converted into electric energy through frequency up-conversion. An innovative mechanical feedback selects the actuated MP depending on the mechanical oscillator position. By doing this, each jaw motion can be harvested. A complete theoretical multiphysics model of the machine has been established for the design and evaluation of the potential of the proposed approach. Global analytical and refined FEM approaches have been combined to integrate the fluid and mechanical behaviors. Based on simulation and preliminary experimental data, the harvested energy is expected to be 8 µJ for one jaw closing, with a theoretical 40 % end-to-end conversion efficiency.

Wall Shear Stress (WSS) has been demonstrated to be a biomarker of the development of atherosclerosis. In vivo assessment of WSS is still challenging, but 4D Flow MRI represents a promising tool to provide 3D velocity data from which WSS can be calculated. In this study, a system based on Laser Doppler Velocimetry (LDV) was developed to validate new improvements of 4D Flow MRI acquisitions and derived WSS computing. A hydraulic circuit was manufactured to allow both 4D Flow MRI and LDV velocity measurements. WSS profiles were calculated with one 2D and one 3D method. Results indicated an excellent agreement between MRI and LDV velocity data, and thus the set-up enabled the evaluation of the improved performances of 3D with respect to the 2D-WSS computation method. To provide a concrete example of the efficacy of this method, the influence of the spatial resolution of MRI data on derived 3D-WSS profiles was investigated. This investigation showed that, with acquisition times compatible with standard clinical conditions, a refined MRI resolution does not improve WSS assessment, if the impact of noise is unreduced. This study represents a reliable basis to validate with LDV WSS calculation methods based on 4D Flow MRI.