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This article is particularly interested in the numerical modeling of water hammer in a hydraulic circuit, taking into account the prevailing water temperature. The study concerns the propagation velocity of the wave and the amplitude of unsteady phenomena encountered in the circuit, as well as the severity and collapse of cavitations that are also considered as major risks. To conjecture the consequences of these phenomena, we were led to simulate a single-phase and two-phase transient flows in a hydraulic copper pipe system in a temperature range of 4–95 °C. To do this, we have developed a solver for the dynamic and continuity equations’ resolution. The method of characteristics is chosen for its capacities to solve these equations. Its application shows that it is robust and adapted to the problem studied. Two cavitations’ models and column separation have been incorporated; in this case, the Discrete Vapor Cavity Model (DVCM) and the Discrete Gas Cavity Model (DGCM). Moreover, in addition to the classic models of quasi-stable friction, of which the models of unsteady friction have been included, like the one based on the instantaneous acceleration proposed by Brunone and the one proposed by Vardy & Brown based on the convolution integral. Although single-phase and two-phase water hammers do not behave in the same way, the results obtained with these models show that the temperature produces a great effect on the hammer.

A low-loss hydraulic transmission offers an efficient and lightweight means to route power from a central source to distal actuators, with example applications in legged and wearable robots. For example, one could develop a completely passive hydraulic transmission for an exoskeleton that routes power from a healthy limb to a limb weakened by neurological injury to enable self-assist or rehabilitation. In this article, we introduce and model a variable hydraulic transmission that features rolling diaphragm cylinders and a discretely variable transmission ratio. The variable transmission utilizes digital hydraulics, wherein valves switch redundantly mounted cylinders in and out of the hydraulic circuit. The article discusses the impact of configuration on the available transmission ratios and passivity. Our modeling efforts focus on the parasitic effects that arise with power losses between the driving and driven joints, compliance and energy storage in the transmission, and drift during switching. We carefully validate the model, comparing analytically predicted fine and gross behaviors to experimental observations. Experimental results demonstrate the feasibility and utility of the proposed device and the associated model which serves as an important tool for the design and control of digital hydraulic transmission systems.

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.

Francis turbines operating at part load conditions develop a cavitation precessing vortex known as a vortex rope in the draft tube cone below the runner outlet. At part load conditions, this vortex precession acts as an excitation source inducing pressure pulsations in the whole hydraulic system at the vortex precession frequency. Simultaneously, the lower pressure levels in the vortex core can lead to cavitation development, increasing the local flow compliance and reducing drastically the pressure wave speed. As a result, the eigen-frequencies of the hydraulic circuit are lowered and may match the vortex rope excitation frequency, leading to undesired resonance conditions. This paper presents a procedure to predict this type of resonance phenomenon in turbine prototypes by performing reduced scale physical turbine model measurements and eigenvalue calculations with linearized system matrices. This new procedure requires the transposition of hydroacoustic parameters from the reduced scale physical model to the prototype scale based on the swirl number and the local cavitation coefficient similarity. The procedure is validated by measurements performed on a turbine prototype featuring a peak of power swings and pressure pulsations in the predicted operating conditions. (C) 2019 Elsevier Ltd. All rights reserved.

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.

Today’s automotive industry faces challenges in reducing emissions to comply with ever tightening statutory provisions. The future is set to provide cleaner vehicles which, on the one hand, reduce the required energy consumption while on the other hand are fit to fulfill customer preferences with regard to driving performance. As a result, the design and control of automotive components in the drive train are reconsidered. This paper treats the modeling and parameter identification of a hydraulic circuit for clutch actuation in automatic transmissions (AT) or dedicated hybrid transmissions (DHT). The examined hydraulic servo-system’s function is to provide the necessary pressure and volume flow for clutch actuation without usage of a hydraulic accumulator. Physical modeling and parameter identification is executed using testbed measurements of an according prototype hardware, aiming to contribute in finding a way towards destruction free identification of hydraulic systems. The nonlinear identification for the examined system that shows switching behaviour is performed using the derivation free particle swarm optimization (PSO) method. The physical models are developed for the purpose of being employed for the design of a trajectory tracking nonlinear model-based control scheme for clutch actuation based on the concept of input-output linearization.

By simulating the operating conditions, it is possible to verify and evaluate the technical properties of motor vehicle oil filters and the functionality of the designed equipment. Contaminated engine oil from operation was used with MANN W950/26 oil filter and a CNH Industrial 2992242 oil filter in the test circuit. Before use, the level of engine oil contamination in the test circuit was determined by evaluating the physicochemical properties. The laboratory test equipment also allows monitoring the technical life of oil filters, with variously contaminated engine oil, with the possibility of extending engine oil change service intervals depending on changes in the physicochemical properties of engine oil and filter efficiency. These laboratory tests can be performed in parallel in two hydraulic circuits, which can significantly reduce the testing time of the filter capabilities of oil filters, without the risk of engine damage, provided that the tests were performed under operating conditions. The results of the evaluation of the filtration capacity of oil filters can be used in the design of new filter materials, but also with a suitably determined methodology of oil filter replacement and engine oil change interval, it is possible to extend replacement intervals, which has a significant benefit not only from an economic but also ecological point of view. The result of the measurements is the confirmation of the functionality of the device with the possibility of simulating the operating conditions, at different degrees of oil contamination, at different operating temperatures and using different oil filters.

This study proposes a practical hybrid automatic transmission model for commercial vehicles based on the first-principle modelling approach. The developed plant model consists of three base elements, i.e. hydraulic circuit, multi-plate wet clutches and planetary gear sets. In today's intelligent transmission control system development framework, plant model plays an important role. It can be used to valid the control algorithm as well as control system in an early stage of the development process, thus shortening development process and improving software quality.

The main aim of the article is to present the design of laboratory test equipment, which is appropriate for monitoring the efficiency of oil filters and the system for evaluating the technical life of engine oils in terms of possible extension of service intervals. The functionality of the designed laboratory test equipment for the filtration of motor oils was verified by a practical experiment with a verification measurement and assessment of the suitability of the hydraulic circuit elements and the designed sensing equipment. The laboratory equipment enables the testing of oil filters with different filtration capacity during simultaneous testing in two separate hydraulic circuits with differently contaminated engine oil, while it enables laboratory measurements to be performed while simulating operating conditions.

This paper employs the quantitative feedback theory (QFT) to design a robust fixed-gain linear velocity controller for a newly developed single-rod pump-controlled actuator. The actuator operates in four quadrants, with a load force becoming resistive or assistive alternatively. The controller also satisfies tracking, stability and sensitivity specifications in the presence of a wide range of system parametric uncertainties. Its performance is examined on an instrumented John Deere JD-48 backhoe. The experimental results show that the controller can maintain the actuator velocity within an acceptable response envelope, despite variation in load mass as high as 163 kg and the hydraulic circuit switching between operating quadrants.

This paper presents a new and efficient sensor for monitoring the presence of wear debris received by the storage tank in hydraulic systems. The proposed sensor plug employs a magnetic approach to attract the ferrous debris in the storage tank. A capacitive sensing scheme is employed in the same sensor plug to sense the presence of the debris accumulated on the plug. This combination of the magnetic and capacitive features in a single sensor for debris monitoring is new and it helps to realize a very sensitive sensor. The proposed sensor is designed in an ingenious way that the permanent magnet that is used to form the magnetic field in the vicinity of the sensor, to attract the debris towards the sensor, itself serves as one of the electrodes of the capacitive sensor. This approach improves the sensitivity and keeps the number of components in the sensor minimum. A prototype of the proposed sensor has been developed and tested. In the prototype, the change in capacitance of the sensor is measured using a high-resolution capacitance-to-digital converter. The sensor was tested after integrating it in a hydraulic test bed which has a controlled debris injection facility to the hydraulic circuit. The output of the sensor was found to be very sensitive to the typical ferrous debris that was introduced in the system. The proposed low-cost sensor will find applications in debris monitoring of underwater and land-based hydraulic systems.

This work aims at value addition to the response in times of train derailments and accessibility to those areas which are inaccessible via rail during emergency situations, by combining the technological up-gradation and reduction in consumption of overhead time with the general principles of hydraulics; thus, contributing to the larger social cause of faster rescue and minimum train rescheduling in times of derailment in the Indian Railways. A rail-road vehicle is a vehicle which can operate both on rail tracks and a conventional road. Conventionally propulsion is through the tires, the rail wheels being free-rolling; the rail wheels are raised and lowered as needed but the authors’ design provides drive to the rail wheels for propulsion. The heavy load breakdown crane of the Indian Railways is its most important asset in Accident Response. But, the use of the existing breakdown cranes is limited only to tracks. Thus, bringing the crane to the site of the accident means travelling it over kilometres of railway lines which, in turn, means loss of response time. The design made by the authors includes the use of a hydraulic circuit for the lowering and lifting of rail and road wheels; the complete hydraulic system installed onto a convertible rail road truck provided with a breakdown crane that enables it to be operated either on road or on railway tracks, and to carry loaded or unloaded railway cars when on rail.

The characteristics of a hydraulic directional control method for the displacement controlled system are studied. The directional control is realized by the pilot-operated check valve. The reversing operation of the pilot-operated check valve system is investigated with simulation and experiment. The relationship between the valve spool motion and the circuit pressure has been analyzed during the directional control. The pressure reversing points during the directional control can be used to determine the operation state of the pilot-operated check valve system. The results indicate that the valve spool motion can be confirmed by the pressure reversing points. The response becomes faster with a smaller diameter control piston. A smaller hydraulic chamber volume is also an effective method to improve the dynamic response. Higher circuit pressures decrease the dynamic response. The results can be applied for the optimized design of the hydraulic directional control method with the pilot-operated check valve.

Three filtration systems using the tractor hydraulic circuit were proposed and verified during the tractors operation. Using the tractor-implement hydraulic system and filter body with accessories the universally useful filtration systems were designed. The designed filtration systems are the second stage of universal oil filtration whereas the first stage is the standard tractor filter. The decrease in the content of iron reached the values 25.53 %, 32.95 % and 41.55 % and the average decrease in oil contamination characterized by average value of decrease in content of iron, copper and silicium reached values 24.3 %, 24.7 % and 35.53 % in dependence on the filtration system and an oil contamination level. The decrease in contamination level verified the ability of designed filtration systems for agricultural tractors.

Valve characteristics are an essential part of digital hydraulics. The on/off solenoid valves utilized on many of these systems can significantly affect the performance. Various factors can affect the speed of the valves causing them to experience various delays, which impact the overall performance of hydraulic systems. This work presents the development of an adaptive statistical based thresholding real-time valve delay model for digital Pump/Motors. The proposed method actively measures the valve delays in real-time and adapts the threshold of the system with the goal of improving the overall efficiency and performance of the system. This work builds on previous work by evaluating an alternative method used to detect valve delays in real-time. The method used here is a shift detection method for the pressure signals that utilizes domain knowledge and the system’s historical statistical behavior. This allows the model to be used over a large range of operating conditions, since the model can learn patterns and adapt to various operating conditions using domain knowledge and statistical behavior. A hydraulic circuit was built to measure the delay time experienced from the time the signal is sent to the valve to the time that the valve opens. Experiments were conducted on a three piston in-line digital pump/motor with 2 valves per cylinder, at low and high pressure ports, for a total of six valves. Two high frequency pressure transducers were used in this circuit to measure and analyze the differential pressure on the low and high pressure side of the on/off valves, as well as three in-cylinder pressure transducers. Data over 60 cycles was acquired to analyze the model against real time valve delays. The results show that the algorithm was successful in adapting the threshold for real time valve delays and accurately measuring the valve delays.

Online monitoring of debris in hydraulic and lubrication oil is an effective method to enable preventive maintenance of the associated machinery. The debris particles generated by the machinery due to wear and tear are carried by the working or lubrication fluids. This paper presents a new online magneto-inductive sensor plug. The new sensor plug consists of a permanent magnet (PM) and a spiral-shaped planar sensor coil. The static magnetic field of the PM is utilized to attract the ferrous wear debris particles, that reach the oil tank/reservoir, to the sensor coil. The inductance of the sensor coil placed close to the PM will change as a function of the presence of magnetic/conductive debris. The change in inductance is measured using a high-resolution inductance to digital converter. The prototype of the proposed sensor unit is tested in an experimental setup similar to an industrial hydraulic system. The sensor responses for different size and quantities of debris particles were recorded after injecting them into the hydraulic circuit. The particles that are attracted towards the sensor plug are retained in the plug itself. Hence its recirculation in the machinery is avoided.

Exoskeleton robots have been developed in various fields and are divided into electric and hydraulic exoskeletons according to the actuator type. In the case of hydraulic robots, because a unidirectional pump is applied, there are limitations to the wearer&rsquo, s walking. In addition, robot systems are complicated, because a directional control valve is required to change the direction of the actuator. To solve these problems, we designed the electro-hydraulic actuator (EHA) system which has both the hydraulic and electric advantages. The EHA system consists of a hydraulic bidirectional pump, a motor, a hydraulic cylinder, and various valves. For the development of the piston pump, we analyzed the gait cycle and considered the flow rate and pulsation rate. In order to reduce the size and weight of the EHA system, the valves were made from one manifold, and the hydraulic circuit was simplified. We verified that the developed EHA system is applicable to robots through position and force control experiments. Because the hydraulic system is nonlinear, we designed a sliding mode control (SMC) and compared it with the proportional integral derivative (PID) controller.

this paper proposes readily computable, detailed model of a micro-hydropower plant suitable for use in small-scale power system studies. The proposed plant has one upper reservoir considered as an infinite source, a surge tank and the penstocks in-between. A detailed study of the hydraulic circuit, and the Francis turbine models is presented, along with the simplified first order model of the synchronous generator. In-depth analysis is made for the design of the speed controller and simulations are performed to observe the dynamic behavior of the resulting system under different operating conditions. The results show that the presented model covers a wider range of frequencies than the classical first order model used for the representation of hydraulic turbine and penstock, and may be more suitable when it comes to analyzing the influence of external disturbances on a micro-hydropower plant.

This Paper chooses variable displacement motor as the driving unit for underwater winch. Based on that, a complete hydraulic control circuit is proposed. The oil circuit can realize the active cable picking and laying automatically. Meanwhile, the motor can be adjusted with infinitely variable speed function. In order to save energy, an automatic unloading circuit is designed. At the same time, considering the complex underwater working environment and bad working conditions, hydraulic clutch is introduced to increase the function of cable passive releasing. The hydraulic circuit has fast response and high fault tolerance, which not only ensures the underwater winch to complete various operations quickly and effectively,but also ensures the safety of all parts of the winch.

This paper focuses on the calculations of basic variables of the hydrostatic circuits in the mechatronic systems. These calculations are important for machines used for forming materials by means of great forces, e.g. hydraulic press. Due to differences in equipment design, lack of a universal method of calculation is noticeable. It is necessary to determine the coefficients required for the calculations in an experimental way.

In this study, the effects of two piezo injectors operated by different mechanisms on multi-injection and Compression ignition (CI) combustion were investigated. High-pressure injectors for CI engines are divided into two categories according to the actuator: Solenoid and piezo injectors. It is commonly known that both injectors have a hydraulic circuit for fuel injection; thus, the performance of the injector is highly dependent on not only hydraulic characteristics such as volume of internal chambers and nozzle geometry, but also the actuation mechanism. Specially, the direct needle-Driven piezo injector (DPI) is introduced in this study and compared with the indirectacting Piezo injector (PI) to investigate the injection characteristics and influences on CI combustion performance by using spray visualization, injection rate measurement, and single cylinder diesel engine experiments, as well as numerical simulation for injection rate modeling of DPI. In the spray visualization experiment, a high-speed camera was used to examine spray tip penetration length and spray speed with respect to each injector. Also, in order to investigate injection rate information, which is a significantly dominant factor in combustion characteristics, the Bosch-tube method was adapted under the condition of a back pressure of 4.5 MPa, corresponding to engine motoring pressure. Also, a single-cylinder CRDi (Common-rail direct-injection) engine experiment was carried out to determine the effects of different piezo-acting mechanisms on two-stage fuel injection and CI combustion. From the key results obtained by this study, the direct needle-driven piezo injector has a faster SOI (Start of injection) and EOI (End of injection). In addition, the overall shape of the injection rate of DPI was narrow and the injection had a higher spray speed than that of PI. Also, DPI has a higher heat release rate and peak pressure, as verified by the engine experiment. In particular, it was found that DPI showed the possibility of combustion improvement when applying a pilot injection strategy.

Injection systems represent key elements in modern diesel engines because of the fundamental role played in fuel spray formation and evolution during the combustion phase. For this reason, their design needs attention and continuous improvements in order to satisfy environmental standards and consumer demands. The present work illustrates the main phases that form the basis of an activity of hydraulic characterization of a solenoid injector for diesel engine applications. The performance of the injection system has been verified by means of injected flow-rate time histories, fuel injected quantities, leakages through the injector pilot-valve, electric driving signals and pressure transients, for different operating conditions, which refer to single and multiple injections. Furthermore, a complete numerical model of the injector and of the high-pressure hydraulic circuit of the injection apparatus has been developed with the aim of deepening the understanding of the internal dynamics of the injection system, which could not be analyzed only experimentally.

Hydraulic turbines are operating at part load conditions depending on availability of hydraulic energy or to meet the grid requirements. The turbine experiences more fatigue during the part load operating conditions due to flow phenomena such as vortex breakdown in the draft tube and flow instability in the runner. The present paper focuses on the investigation of a high head model Francis turbine operating at 50% load. Pressure measurements have been carried out experimentally on a model Francis turbine. Total six pressure sensors were mounted inside the turbine and other two pressure sensors were mounted at the turbine inlet pipe. It is observed that the turbine experiences significant pressure fluctuations at the vaneless space and the runner. Moreover, a standing wave is observed between the pressure tank outlet and the turbine inlet. Analysis of the data acquired by the pressure sensors mounted in the draft tube showed the presence of vortex breakdown co-rotating with the runner. The detailed analysis showed the rotating and plunging components of the vortex breakdown. The influence of the rotating component was observed in the entire hydraulic circuit including distributor and turbine inlet but not the plunging one.

Purpose. Search for ways to improve the technical level of the hydraulic fluid power of a hose concrete pump by analyzing the hydraulic schematic diagram and dynamic characteristics depending on the moment of resistance, moment of inertia and properties of the working fluid. Method. The construction of a mathematical model of the dynamics of a hydraulic fluid power is based on Newton's laws of mechanics, Pascal's law and the continuity equation for fluids. The dynamics study was implemented using the VisSim package. The results of studies of the influence of variable parameters on the rotor speed and pressure in the discharge line of the hydraulic motor are presented in graphical form. Results. It was found that in a volumetric hydraulic fluid power of a concrete pump with rotor rotation from a gerotor hydraulic motor, there are significant fluctuations in pressure and speed, due to the kinematics of the pump, temporary factors of the increase in the moment of resistance and supply of the working fluid to the hydraulic motor with the throttle method of its regulation. The ratio of the maximum and steady-state pressure values is 1,9 times obtained for hydraulic motors of different displacement. The possibilities of reducing the dynamic loading of the hydraulic fluid power by improving its hydraulic schematic diagram and control algorithm are shown. Conclusion. Recommendations have been developed for reducing dynamic loads in a hydraulic fluid power by modernizing the hydraulic circuit diagram by introducing electrohydroautomatics devices and changing the algorithm for starting and stopping the pump.

In the operation of the double-cylinder gantry hydraulic machine, whether the two oil cylinders as the power transmission element are synchronized is an important factor affecting the precision of the workpiece manufacturing. Because the oil cylinder directly affects the horizontal precision of the beam of the actuator during the work of the press. Therefore, the double-cylinder synchronous precision control of the hydraulic machine is one of the key technical problems that needs to be solved in the manufacturing process of the hydraulic machine. This paper proposes a design scheme for the mechanical structure of the synchronous precision control of the double-cylinder gantry hydraulic machine. On the basis of using a simple hydraulic circuit to ensure the basic synchronization of the two oil cylinders, the flexible connection of the piston rod of the oil cylinder and the beam is used to reduce the damage caused by the deflection of the beam of the hydraulic system and machinery of the hydraulic machine. At the same time, a conehead is added at the end of the piston rod, and a taper hole is added to the corresponding part of the beam. By the alignment of the cylinder rod and the taper hole of the beam, the position of the beam is corrected so as to ensure the machining precision of the workpiece.

External gear pumps are among the most popular fluid power positive displacement pumps, however they often suffer of excessive flow pulsation transmitted to the downstream circuit. To meet the increasing demand of quiet operation for modern fluid power system, a better understanding of the ripple source of gear pumps is desirable. This paper presents a novel approach for the analysis of the ripple source of gear pumps based on decomposition into a kinematic component and a pressurization component. The pump ripple can be regarded as the superposition of the displacement solution and the pressurization solution. The displacement solution is driven by the kinematic flow, and it can be derived from the kinematic flow theory; instead, the pressurization solution can be approximated by overlapping the pressurization flow for a single displacement chamber. Furthermore, in this way the changes of these two components with modification of the delivery circuit are determined in both analytical and numerical ways. The result of this analysis provides a good interpretation of the pulsation simulated by a detailed lumped-parameter simulation model, thus showing its validity. The result also indicates that the response of two ripple sources to the change of the loading in the downstream hydraulic circuit is very different. These findings reveal the limitation of the traditional experimental method for determining the pump ripple, that new experimental methods which are more physics-based can be potentially formulated based on this work.

The delivery pressure ripple has always been a critical aspect in fluid power applications, since it generates noise and stresses the hydraulic circuit components at the delivery side of the pump. In this paper a possible strategy for the reduction of the delivery pressure ripple is proposed regarding a variable displacement axial piston pump through suitable modification of the swash plate surface. For this purpose a mathematical model of the pump has been developed, focused on the fluid-dynamic aspect with particular attention on the piston kinematics. The model has been used to introduce a passive control solution in order to modify the instantaneously delivered flow rate and consequently the pressure ripple. In detail, it has been hypothesized to modify the swash plate realizing on its surface a profile with the purpose of modifying the motion law of the pistons. The simulations results have demonstrated the effectiveness of the proposed solution in reducing the amplitude of the pressure ripple.

The present work is aimed at analyzing the performance of the commercial filters used for the mechanical filtration of suspended solid particles. In particular, it is intended to evaluate the head losses due to the presence of the filter in the plant and how these losses vary depending on the circulating flow rate, the nominal porosity of the filter, and its clogging degree. Filters with interstices of different sizes, from 1 to 50 μm, were compared for the performance analysis. The polypropylene wire, in facts, wrapped around a windowed cylinder of the same material, allows the creation of meshes with the desired degree of compactness. The experiments were carried out at the Laboratory of Environmental and Maritime Hydraulics (LIDAM) in a hydraulic circuit reproducing a domestic piping system, where different water demand scenarios were analyzed. The clogging of the cartridge was made with the aid of sand particles, attached, with the help of a natural glue, to the external surface of the filter. More than 200 measurements were carried out, which showed a clear increasing trend of the head losses at the filter as the clogging degree and the circulating flow rate increase. In all cases, the trend of the pressure drop at the filter has a more than linear trend. Also, it was observed that head losses did not exhibit a marked dependence on the nominal porosity. Best performances in terms of minor head losses were obtained by the 50-μm filter.

Monitoring is an important aspect of operation and maintenance in virtually every industrial system. However, the extent and methods of monitoring vastly vary in different systems, from fully automated to fully manual. One of the challenges of automated monitoring is the tediousness of, and the extent of engineering time and effort required to develop necessary models or machine learning algorithms for the units to be monitored. Model-free monitoring, on the other hand, can save resources and efforts substantially. However, more often than not they have a very limited scope and application. Such a system is needed, for example, to monitor entire Heating, Ventilation and Air Conditioning (HVAC) systems, consisting of different types of sensors such as temperature, pressure, humidity or flow sensors. Recently, we proposed the Context-Aware Health Monitoring (CAH) system for model-free monitoring of any injective-function black-box, and it was tested successfully on an AC motor. In this paper, we evaluate the CAH system for an entirely different industrial use-case, that is, a hydraulic circuit. The results show the potential for considerable benefits in monitoring HVAC systems. Moreover, in the light of applying CAH to different use-cases which may potentially need a different setup of parameters, we performed a sensitivity analysis on the values of different parameters in the system. The results show the robustness of CAH with regard to the values of these parameters.

In this paper the main design features of an innovative combined hydraulic valve for high-pressure washing applications have been investigated by means of numerical modelling and experimental testing. This particular type of hydraulic component is obtained joining together a relief and a bypass valve. When the washing system is activated, the relief valve limits the maximum admitted working pressure while, when the washing system is switched off, the bypass valve unloads the hydraulic circuit and a direct connection with the drain ambient is quickly established. First of all, a very detailed lumped and distributed numerical model of the combined valve has been developed, with particular care devoted to the coupling between all the mechanical internal components (piston with holes, bushing and related springs) and to the valve body inner hydraulic connections. Then, the predictive capability of this lumped and distributed numerical model has been verified by means of a numerical versus experimental comparison, performed for a wide range of operating conditions (inlet pressure and volumetric flow rate) and geometrical parameters (sealing gaps, springs' stiffness and nozzle size). Finally, the previously validated numerical model has been applied in order to identify reliable design solutions for typical washing conditions, characterized by fluid pressure values spanning in the range between 50 to 280 bar and inlet volumetric flow rates comprised between 10 and 40 l/min.

Purpose – The purpose of this paper is to evaluate the performance of the semi-active fluid damper. It is recognized that the performance of such a damper depends upon the magnetic and hydraulic circuit design. These dampers are generally used to control the vibrations in various applications in machine tools and robots. The present paper deals with the design of magneto-rheological (MR) damper. A finite element model is built to analyze and understand the performance of a 2D axi-symmetric MR damper. Various configurations of damper with modified piston ends are investigated. The input current to the coil and the piston velocity are varied to evaluate the resulting change in magnetic flux density (B), magnetic field (H), field dependent yield stress and magnetic force vectors. The simulation results of the various configurations of damper show that higher magnetic force is associated with plain piston ends. The performance of filleted piston ends is superior to that of other configurations for the same magnitude of coil current and piston velocity. Design/methodology/approach – The damper design is done based on the fact that mechanical energy required for yielding of MR fluid increases with increase in applied magnetic field intensity. In the presence of magnetic field, the MR fluid follows Bingham’s plastic flow model, given by the equation τ = η γ•+τ y (H) τ > τ y . The above equation is used to design a device which works on the basis of MR fluid. The total pressure drop in the damper is evaluated by summing the viscous component and yield stress component which is approximated as ΔP = 12ηQL/g3W + CτyL/g, where the value of the parameter, C ranges from a minimum of 2 (for ΔPτ ΔPη less than approximately 1) to a maximum of 3 (for ΔPτ/ΔPη greater than approximately 100). To calculate the change in pressure on either side of the piston within the cylinder, yield stress is required which is obtained from the graph of yield stress vs magnetic field intensity provided by Lord Corporation for MR fluid −132 DG. Findings – In this work, three different finite element models of MR damper piston are analyzed. The regression equations, contour plots and surface plots are obtained for different parameters. This study can be used as a reference for selecting the parameters for meeting different requirements. It is observed from the simulation of these models that the plain ends model gave optimum magnetic force and 2D flux lines with respect to damper input current. This is due to the fact that the plain ends model has more area when compared with that of other models. It is also observed that filleted ends model gave optimum magnetic flux density and yield stress. As there is reduced pole length in the filleted ends model, the MR fluid occupies vacant area, and hence results in increased flux density and yield shear stress. The filleted ends assist the formation of dense magnetic flux lines thereby increasing the flux density and yield stress. This implies that higher load can be carried by the filleted ends damper even with a smaller size. Originality/value – This work is carried out to manufacture different capacities of the dampers. This can be applied as vibration controls.

The article offers design of a hydraulic elevator installation for cleaning up water-source wells of sand packs. It considerers the installation hydraulic circuit according to which the normal pump feeds the high-level tank water into the borehole through two parallel water lines. The water-jet line with washing nozzle for destroying the sand-pack and the supply pipe-line coupled with the operational nozzle of the hydraulic elevator containing the inlet and the supply pipelines for respectively intaking the hydromixture and removing it from the well. The paper adduces equations for fluid motion in the supply and the water-jet pipelines and offers expressions for evaluating the required heads in them. For determining water flow in the supply and the water-jet pipe lines the author proposes to employ graphical approach allowing finding the regime point in Q–H chart by means of building characteristics of the pump and the pipe-lines. For calculating the useful vertical head, supply and dimensions of the hydraulic elevator the article employs the equation of motion quantity with consistency admission of the motion quantity before and after mixing the flows in the hydraulic elevator. The suggested correlations for evaluating the hydraulic elevator efficiency determine the sand pack removal duration as function of its sizes and the ejected fluid flow rate. A hydraulic-elevator installation parameters estimation example illustrates removing a sand pack from a water-source borehole of 41 m deep and 150 mm diameter bored in the village of Uzla of Myadelsk region, of Minsk oblast. The working efficiency of a manufactured and laboratory tested engineering prototype of the hydraulic elevator installation was acknowledged in actual tests at the indicated borehole site. With application of graphical approach, the suggested for the hydraulic elevator installation parameters calculation procedure allows selecting, with given depth and the borehole diameter, the normal pump, diameters of the supply and the water-jet pipe lines. After that, calculating dimensions of the jet pump – hydraulic elevator and the supply pipe line, and performing analysis of efficiency and work out characteristics of the installation.

The thermo-hydraulic single regime operating generator is an innovative concept developed for the propulsion of road vehicles. The aim of the paper is to calculate the pressure losses in the hydraulic circuit of the single regime running thermo-hydraulic generator. The calculus is based on a modular approach proposed by. The pressure of the hydraulic liquid is determined by taking into consideration the local and the linear pressure losses in the system. These pressure losses are calculated applying classic formulas. This is important because the free piston displacement depends on the pressures acting on the side surfaces. The calculus algorithm is based on the constructive data of an experimental model.

A simulator of the human cardiovascular system intended for testing circulatory assist devices is described. The device is a hydraulic circuit that simulates the greater and lesser circulation. It consists of two artificial ventricles, four closed reservoirs, a pneumatic control system, a flow sensor, ten liquid pressure sensors, and two inductors to provide vascular resistance. The device has hydrodynamic characteristics comparable to that of the human heart. It can be used for preclinical testing of circulatory assist devices of the left ventricle, right ventricle, or both ventricles of the heart, and of the completely artificial heart.

The paper presents an original pneumo-hydraulic system that controls the speed and the position of the actuated load by using a hydraulic circuit containing a hydraulic proportional throttle. A mathematical model of the solution is developed and numerical simulations are performed. The experimental results obtained on the built model confirm the theoretical ones.

Purpose: During the start-up period, the response time of a hydraulic system increases in the winter because of the increased oil viscosity caused by the cold weather. The problems of delayed tractor starting and excessive wear of the clutch disk occur for these reasons. Therefore, this study develops an analysis model using the commercial hydraulic analysis program AMESim to examine the characteristics of delays in power shuttle starting at different oil temperatures. Methods: In the experiment, a tractor was stationary on a flat surface with the engine running at a constant speed of 1,080 rpm. The forward lever was then pressed to activate the power shuttle at three different oil temperatures, and the pressure changes were measured. The pressure on the forward clutch control valve was measured by a pressure gauge installed on the hydraulic line supplied to the transmission from the main valve. An analysis model was also developed and verified with actual tests. Results: The trend of the simulated pressures of the power shuttle is similar to that of the measured pressures, and a constant modulation period was observed in both the simulation and test results. However, the difference found between the simulation and test results was the initial pressure required to overcome the initial force of the clutch spring. Conclusions: This study also examines the characteristics of the delayed startup of the power shuttle at different oil temperatures through simulations.

The steering system of a vehicle impacts on the vehicle performance, safety and on the driver’s comfort. Moreover, in off-road vehicles using hydrostatic steering systems, the energy dissipation also becomes a critical issue. These aspects push and motivate innovation, research and analysis in the field of agricultural tractors. This paper proposes the modelling and analysis of a hydrostatic steering system for an agricultural tractor to calculate the performance of the system and determine the influence of its main design parameters. The focus here is on the driver’s steering feel, which can improve the driver’s behavior reducing unnecessary steering corrections during the working conditions. The hydrostatic steering system is quite complex and involves a hydraulic circuit and a mechanical mechanism to transmit the steering to the vehicle tires. The detailed lumped parameters model here proposed allows to simulate the dynamic behavior of the steering system and to both enhance the understanding of the system and to improve the design through parameters sensitivity analysis.

A comprehensive comparison between solenoid and indirect acting piezoelectric injectors has been carried out. The working principle of these injector typologies is illustrated, and their hydraulic performance has been analysed and discussed on the basis of experimental data collected at a hydraulic test rig. The injector characteristics, injected flow-rate profiles, nozzle opening and closure delays, injector leakages and injected volume fluctuations with the dwell time have been compared in order to evaluate the impact of the injector driving system. The solenoid and piezoelectric injectors have been installed on a Euro 5 diesel engine, which has been tested experimentally at a dynamometer cell. Optimized double and triple injection strategies have been considered at some representative key points of the New European Driving Cycle. Engine-out emissions, brake specific fuel consumption and combustion noise are presented and discussed, with the support of a three-zone, diesel combustion diagnostic model. The research has focused on the cause-and-effect relationships between the hydraulic performance of the injectors and the results of the engine tests. The primary goal has been to assess if the differences in engine performance between the solenoidal and indirect-acting piezoelectric injector setups are due to the injector driving system or to specific features that are present in the hydraulic circuit of the considered injectors and which are not closely related to the driving system. A final evaluation of the potential of the piezoelectric technology for driving indirect acting injectors is provided on the basis of real engine results.

A detailed analysis of a common rail (CR) fuel injection system, equipped with solenoid injectors for Euro 6 diesel engine applications, has been performed in the frequency domain. A lumped parameter numerical model of the high-pressure hydraulic circuit, from the pump delivery to the injector nozzle, has been realized. The model outcomes have been validated through a comparison with frequency values that were obtained by applying the peak-picking technique to the experimental pressure time histories acquired from the pipe that connects the injector to the rail. The eigenvectors associated with the different eigenfrequencies have been calculated and physically interpreted, thus providing a methodology for the modal analysis of hydraulic systems. Three main modal motions have been identified in the considered fuel injection apparatus, and the possible resonances with the external forcing terms, i.e., pump delivered flow rate, injected flow rate, and injector dynamic fuel leakage through the pilot valve, have been discussed. The investigation has shown that the rail is mainly involved in the first two vibration modes. In the first mode, the rail performs a decoupling action between the high-pressure pump and the downstream hydraulic circuit. Consequently, the oscillations generated by the pump flow rates mainly remain confined to the pipe between the pump and the rail. The second mode is centered on the rail and involves a large part of the hydraulic circuit, both upstream and downstream of the rail. Finally, the third mode principally affects the injector and its internal hydraulic circuit. It has also been observed that some geometric features of the injection apparatus can have a significant effect on the system dynamics and can induce hydraulic resonance phenomena. Furthermore, the lumped parameter model has been used to determine a simplified transfer function between rail pressure and injected flow rate. The knowledge obtained from this study can help to guide designers draw up an improved design of this kind of apparatus, because the pressure waves, which are triggered by impulsive events and are typical of injector working, can affect the performance of modern injection systems, especially when digital rate shaping strategies or closely coupled multiple injections are implemented.

This paper mainly designs a device for improving setting load of hydraulic support. The device could enhance the pressure of bottom cavity of the stand column in hydraulic support, decrease the late bearing time of stand column of hydraulic support, shore the roof of coal face effectively, prevent the roof fall caused by separating the roof of wall rock untimely from the layer, and ensure the safety production in the coal facing, with the circumstance that the structure of liquid valve bank of hydraulic support isn’t changed and that it has no influence on the normal working of liquid-inlet and rising support. The device using the techniques of hydraumatic and machinery, of which the structure is simple, safe and reliable, is convenient for the work at the underground coal mine. Through the simulated analysis for hydraulic circuit of hydraulic support and the field test, the hydraulic system of hydraulic support is stability with no larger vibration and has a better effect on pressurizing, after using the device. So, the automatic pressure control device to setting load has good popularization and application value.

In order to help beginner to learn hydraulic circuits, the analogy teaching method of hydraulic basic circuits is introduced in this paper. Firstly, Analogy of electrical and hydraulic components are introduced. Then the typical hydraulic basic circuits and their corresponding analogy electrical circuits are given respectively. Finally, a complex hydraulic circuits composed of several basic circuits and its corresponding analogy electrical circuit are given. By analogy analysis for their working principle, the complex hydraulic circuit can be better understood by beginners.

Pressure of the liquid is used as power source of hydraulic vibration exciter. Rotary directional control valve is the realization of oiling-way veversing components . The piston is reciprocated under the influence of the change of the hydraulic. The reciprocating movement of the piston is a result of fluid pressure.Working area of the piston multiplied by the pressure of the liquid is equal to the thrust of the piston.Displacement response of the vibration exciter can be simplified to the second-order vibration systems.Elastic beam is used as limit components of piston of vibration exciter,the piston vibration waveform is a sine wave .The volume of elastic beam is smaller than the volume of fluid elastic element . The hydraulic circuit is a dual pump fuel supply circuits.Pumps are used to supply rotary valve and hydraulic cylinder .Dual pumps fuel supply system is conducive to control fluid pressure and flow of the rotary valve and vibration piston.

A Hydraulic circuit is a group of components such as pumps, actuators, and control valves so arranged that they will perform a useful task. When analyzing or designing a hydraulic circuit, the following three important considerations must be taken into account.Safety of operation,Performance of desired function, Efficiency of operation.It is very important for the fluid power ( Hydraulics and Pneumatics ) designer to have a working knowledge of components and how they operate in a circuit. Hydraulic circuits are developed through the use of graphical symbols for all components. Keywords: damper,hydraulic circuit

Based on the structure of a certain type of aviation axial-piston pump’s valve plate which adopts a pre-pressurization fluid path (consisting a damping hole, a buffer chamber, and an orifice) to reduce flow ripple, a single-piston model of the aviation axial-piston pump is presented. This single-piston model comprehensively considers fluid compressibility, orifice restriction effect, fluid resistance in the capillary tube, and the leakage flow. Besides, the instantaneous discharge areas used in the single-piston model have been calculated in detail. Based on the single-piston model, a multi-piston pump model has been established according to the simple hydraulic circuit. The single- and multi-piston pump models have been realized by the S-function in Matlab/Simulink. The developed multi-piston pump model has been validated by being compared with the numerical result by computational fluid dynamic (CFD). The effects of the pre-pressurization fluid path on the flow ripple and the instantaneous pressure in the piston chamber have been studied and optimized design recommendations for the aviation axial-piston pump have been given out.

Bogie angle linked steering trucks have an excellent curving performance in circular curve sections. In order to gain even greater curving performance, a power-assisted steering system was developed for reducing wheel lateral forces in transition curve sections by generating the control force in the turning direction of the steering truck. In addition, a steering electro-hydraulic actuator was designed for reducing lateral forces in transition curve sections while preventing wrong direction steering operation which is the biggest problem with active steering systems. Finally, confirmation was obtained through running test on a test line that this steering actuator improved steering performance and maintained the fail-safe function.

Generally speaking, hydraulic control systems can be divided into two different driving concepts. The first one is the well-known valve-controlled system and the second one is the pump-controlled system. The former possesses the feature of fast dynamic response. However, the poor energy-saving performance is its major fault. On the contrary, the pump-controlled hydraulic system has the significant advantage of energy-saving which meets the current demand in modern machine design. In this paper, the simulation analysis using Matlab/Simulink and DSHplus for a newly developed energy-saving hydraulic tube bender is conducted. Instead of the conventional fixed displacement hydraulic pump, the new hydraulic tube bender utilizes an internal gear pump with AC servomotor as its driving power source. In the new energy-saving hydraulic circuit, the use of conventional pressure relief valve is no longer necessary since the demanded flow-rate and pressure output can be precisely obtained by continuously changing the speed of the AC servomotor. In addition, from the simulation results, it is shown that the energy-saving performance of load-sensing control scheme is somewhat better than that of constant pressure control scheme. Furthermore, the simulation results also show that the newly developed hydraulic tube bender can save up to 40% of energy consumption in a working cycle as compared to the conventional hydraulic tube bender.

Concept design of a scrap compactor is presented. Required data for the design of the scrap compactor, the hydraulic circuit, the compression ratio, force required for compression are collected from literature. The current practice of scarp removal and storage in a small scale industry is shown. The calculations for arriving at the force required for compaction is presented. The hydraulic circuit diagram and testing of the circuit in a pneumatic test bench are explained. Cost of the prototype and the break even period are discussed. Ergonomic principles and safety due to usage of scrap compactor are highlighted.

This paper deals with the effect of ecological energy carrier on flow characteristics of a hydraulic pump. A hydraulic oil MOL Farm UTTO Synt was used as an ecological energy carrier. After completing 900 engine hours, the flow efficiency of the hydraulic pump decreased by Δηpr = 1.197 %. Oil samples were taken from the agricultural tractor Zetor Forterra 114 41. These samples were subjected to an IR spectroscopy analysis in an accredited laboratory WearCheck, Hungary. The following oil properties were examined: kinematic viscosity at 40 °C, viscosity index, silicium and ferrum content.

The designed laboratory device will solve the issue of test methods of tractor hydraulics, monitoring the lifetime of hydraulic components, and testing of various oil types. The results of experimental measurements of forces and pressures in the three-point hydraulic hitch of tractor with plough allow implementing the design and simulation of operational loads of the dynamic system of tractor three-point hitch (TPH) under laboratory conditions. Theoretical and experimental works were focused on tractors. The design of test device is based on load characteristics obtained from the operation of tractor with plough. Research was focused on the use of results obtained from operational measurements of the tractor with plough and their simulation by a hydrostatic simulator under laboratory conditions. The laboratory device will enable the TPH life tests while loading with forces in the horizontal and vertical direction so that it corresponds to a practical loading process

As is known to all, domestic productions of injection molding machine are huge and exported to all over the world. However, the production can only occupy the low-end markets because of its high-energy consumption and low molding precision. Besides the problems of mechanical components, the main reason led to such results lie in the its too backward hydraulic system. By comparing domestic traditional hydraulic system with foreign new hydraulic servo system, this paper focuses on the analysis of the characteristics of foreign new hydraulic servo system and verify the results by experiments based on the upper two different hydraulic system. Through this paper hopefully can it provide some practical directs to the design of domestic new hydraulic system.