Hydraulic Circuit Research Articles

Air-Hydraulic Servo Booster Toward Submersible Water-Driven Robots

This letter describes a novel pneumatically controlled hydraulic booster: Air-Hydraulic Servo Booster (AHSB) applied to water-hydraulic robots. This pump-less hydraulic circuit can control middle range water pressure easily by pneumatic proportional valves, where one can use tap water as the hydraulic medium. In this letter, we explain the principle of operation and the control system integration applied to a simple submersible robot arm. Then we analyze the full dynamics of the system and derive control algorithms by which a robust pressure controller is used with sliding mode control. The proposed system is evaluated using a joint torque and position control experiment on the 0.35-m-long robot arm with a 10 kg payload, with connections via 20-m-long hydraulic hoses. The experimental results demonstrate the high potential of the proposed system for remotely operated robots that work compliantly and robustly in various fields without contamination.

Draining analyses of the primary cooling circuits of the SPIDER Beam Source

The SPIDER in-vessel actively cooled components shall be drained in case of major maintenance to limit, as much as possible, atmospheric corrosion inside the circuits, to prevent water spreading, and finally to allow the execution of vacuum leak tests of the components before re-installation of the SPIDER Beam Source (SBS) inside the Vacuum Vessel. Draining of hydraulic circuits is first foreseen by gravity after opening the end connections of hydraulic circuits and then by blowing out with nitrogen. Injection of pressurized nitrogen is simulated by means of one-dimensional and three-dimensional models to perform transient two-phases analyses in order to calculate the minimum required inlet pressure and estimate the process time.

An analytical method for solving the problem of heat network load flow

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%.

Computer simulation and full-scale measurements of the load flow in a functioning heating network

The article aims to identify patterns in the distribution of heating energy to consumers with a varying availability of regulation equipment under real conditions of a central heating network, as well as to compare the results of computer simulation with full-scale measurements. For computer simulation, well-known mathematical methods for calculating the load flow in hydraulic circuits were used. Experimental studies of the operation modes of heat supply systems were carried out using the data of the control and monitoring systems of thermal power plants using the Siemens Simatic PCS7 software, a Portaflow 300 ultrasonic flow meter, stationary electromagnetic flow transducers, verified and certified manometers and thermometers. The graphs of the actual hydrodynamic modes of the heating network under study were obtained at outdoor air temperatures from +8 to -37°C, as well as under abnormal conditions (temperature drop in the supply pipeline and pressure drop at the heating network input). It was proposed to use jointly the simulation by means of the JA_Net software and full-scale measurements of the thermohydraulic operating modes of a centralised heat supply system, whose consumers have a various degree of regulation equipment. It was shown that the proposed complex method of qualitative and quantitative assessment of the efficiency of district heating networks makes it possible to identify the features of control of their hydraulic modes when connecting new consumers with a varying degree of automation. According to the obtained characteristics of changes in the flow rate of the coolant in the consumers’ internal systems depending on the pressure drop at the tie-in point, the lack of response to emergency situations on part of the consumers whose heat supply systems are equipped with the means of qualitative and quantitative regulation of the heat load, is associated with the process of automatic adjustment of the degree of opening of flow controllers and control valves at individual points. In future work, we will develop guidelines for levelling the imbalance of the heating network under the conditions of uneven provision of facilities with automation equipment when implementing projects for the complex modernisation of heat consumers or connecting new facilities to existing heat supply networks.

Numerical-Experimental Optimization of the Common-Feeding Injection System Concept for Application to Light-Duty Commercial Vehicles

Abstract The innovative common feeding (CF) fuel injection system has been designed for a light duty commercial vehicle diesel engine in order to reduce production costs and to allow easy installation on the engine, compared with a common rail (CR) system. In the CF apparatus, an additional delivery chamber is mechanically fixed at the high-pressure pump outlet, and the rail is removed from the hydraulic circuit. Experimental tests have been carried out on a hydraulic test rig in order to compare the general performance of the prototypal CF system with those of a CR system equipped with different rail volumes. In the cases of the double injections, the fluctuations of the injected mass pertaining to the second injections have been investigated during dwell time (DT) sweeps, and design solutions have been provided to minimize such oscillations. Moreover, an injection system numerical diagnostic model has been validated, and the reduced accumulation volumes linked phenomena have been analyzed. In general, the performance of the injection systems with different hydraulic capacitances or shapes of the accumulator are similar. One difference is that the injection rate features slightly different slopes during the rising phases; furthermore, cycle-to-cycle dispersions in the injected mass increase to some extent when the hydraulic capacitance is dramatically decreased. Finally, the frequencies of the free pressure waves, due to the water hammer occurring at the end of a hydraulic injection, are different when the shape of the accumulation volume changes, whereas these frequencies are independent of the accumulation volume sizes.

Dynamics of the hydraulic fluid power of rotation of the hose concrete pump

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.

Modeling and dynamic analysis of the dynamic stabilization unit based on bond graph

This paper, respectively, considers the nonlinear contact and Coulomb friction between rollers and rails, the characteristics of a hydraulic cylinder, and the contact characteristics between sleepers and ballast. The models of hydraulic cylinders are employed to realize the characteristics of hydraulic circuits and clamping forces. And the effects of the Coulomb friction between the track roller and the rail are simulated by calling the Boolean operation in the bond graph simulation software 20-sim. Based on the above analyses, this paper explores deeply which effect the pressures in the hydraulic cylinders and the hydraulic resistances of the flow passes at the inlets and outlets of the hydraulic cylinders will have on roller–rail contacts and working effects. As a result, the increase in pressure of the hydraulic cylinder will stabilize the roller–rail contact and improve the energy transmission efficiency. The increase in the hydraulic resistance value can enhance the working effect to some extent. With regard to the friction, there are four forms of frictional contact between the roller and the rail.

Evaluation of Pressure Resonance Phenomena in DCT Actuation Circuits

The paper investigates hydraulic wave propagation phenomena through hydraulic circuits of power transmission systems by means of numerical approaches. The actuation circuit of a Dual-Clutch Transmission (DCT) power transmission system supplied by a Gerotor pump is analyzed. A steady state approach is adopted to detect resonance phenomena due to Gerotor design parameters and circuit lengths, while one-dimensional numerical models are implemented to predict the pressure oscillations through the hydraulic ducts for the whole pump operating domain. CFD-1D pipelines are adopted to address the pressure oscillation behavior through the hydraulic pipeline, while spectral maps and order tracking techniques are used to evaluate their fluctuation intensity in function of the pump speed rate. The numerical models are validated with experimental tests performed on an ad hoc test rig for power transmission systems and a good match is found between the numerical and the experimental results. Pump design parameters as well as hydraulic accumulators and resonators are numerically investigated to quantitatively evaluate their improvement on the circuits’ hydro-dynamic behavior. Furthermore, simplified numerical models are implemented to investigate the frequency response behavior of the hydraulic circuits by means of linear analysis. This approach resulted to be particularly effective for the prediction of the resonance frequencies location, and it can be adopted as an optimization tool since significant simulation time can be saved. Finally, the performance of the circuits operating with an eco-friendly fluid is evaluated numerically and the results are compared with the ones obtained with a traditional petroleum-based oil.

Performance Analysis of Hydraulic Machines Using Impellers Made from Conventional Steel and 3D Printing Co-polymer

The research on hydraulic machines in industries is appropriate for many reasons. This paper deals with the creation of 3D prototypes of impellers of hydraulic machines printed from ABS plastic and verification of operating characteristics compared to conventional steel impellers of pump and also in turbine mode. The work includes properties, composition and verification of mechanical properties of ABS for different printing methods. Practical measurements of the specific geometry of the different 3D variants of the radial one-stage centrifugal impeller from ABS compared to metal wheels in the real hydraulic circuit are described. The results of the development of experiments demonstrate that the performance characteristics of the printed impellers of all variants have very similar functional values and very identical trends of functional curves of mechanical power and overall mechanical efficiency. At the same optimal speed, the highest performance and efficiency also as the metal wheels have been produced. It is clear from the results of work that prototypes produced by 3D printing achieve optimal performance parameter values in hydraulic testing and it is possible to successfully use this advanced technology in the verification of newly developed pumps, turbines and pumps turbines.

An LDV based method to quantify the error of PC-MRI derived Wall Shear Stress measurement

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.

Quantification of the Hemodynamic Changes of Cirrhosis with Free-Breathing Self-Navigated MRI.

Non-invasive assessment of the hemodynamic changes of cirrhosis might help guide management of patients with liver disease but are currently limited. To determine whether free-breathing 4D flow MRI can be used to quantify the hemodynamic effects of cirrhosis and introduce hydraulic circuit indexes of severity. Retrospective. Forty-seven patients including 26 with cirrhosis. 3 T/free-breathing 4D flow MRI with soft gating and golden-angle view ordering. Measurements of the supra-celiac abdominal aorta, supra-renal abdominal aorta (SRA), celiac trunk (CeT), superior mesenteric artery (SMA), splenic artery (SpA), common hepatic artery (CHA), portal vein (PV), and supra-renal inferior vena cava (IVC) were made by two radiologists. Measures of hepatic vascular resistance (hepatic arterial relative resistance [HARR]; portal resistive index [PRI]) were proposed and calculated. Bland-Altman, Pearson's correlation, Tukey's multiple comparison, and Cohen's kappa. P < 0.05 was considered significant. Forty-four of 47 studies yielded adequate image quality for flow quantification (94%). Arterial structures showed high inter-reader concordance (range; ρ = 0.948-0.987) and the IVC (ρ = 0.972), with moderate concordance in the PV (ρ = 0.866). Conservation of mass analysis showed concordance between large vessels (SRA vs. IVC; ρ = 0.806), small vessels (celiac vs. CHA + SpA; ρ = 0.939), and across capillary beds (CeT + SMA vs. PV; ρ = 0.862). Splanchnic flow was increased in patients with portosystemic shunting (PSS) relative to control patients and patients with cirrhosis without PSS (P < 0.05, difference range 0.11-0.68 liter/m). HARR was elevated and PRI was decreased in patients with PSS (3.55 and 1.49, respectively) compared to both the control (2.11/3.18) and non-PSS (2.11/2.35) cohorts. 4D flow MRI with self-navigation was technically feasible, showing promise in quantifying the hemodynamic effects of cirrhosis. Proposed quantitative metrics of hepatic vascular resistance correlated with PSS. 3 TECHNICAL EFFICACY STAGE: 2.

Control of the Test Rig for Spring Stiffness Measurement with Hydraulic Integrated Actuator and Computer Vision

The paper deals with the control of the test rig for measurement of the stiffness of the spring. The test rig is equipped with integrated hydraulic actuator and multilayer control system with computer vision to automate the testing process and to increase the safety of the operating staff during the testing. The integrated hydraulic actuator allows to control the piston velocity and position and to produce the force needed for the spring compression and stiffness measurement. It has an integrated manifold with four proportional flow control valves connected as the full hydraulic resistance bridge. Each control valve is controlled separately using the input signal. That makes it possible to realize different connections and control strategies of the hydraulic cylinder using the different control algorithms. The hydraulic circuit was modelled and simulated, and the achieved simulation results are presented in the paper. The test rig is controlled using the microprocessor control system and is it equipped by different transducers – position transducer, pressure transducers and force transducer to be able to collect data important for the stiffness characteristic evaluation. The upper level of the control system is created by the vision control system. The goal of the implementation of the machine vision is to decrease the number of the manual operations done by the technician by the spring testing and to extend the automatic testing cycle of the automatic computer vision-controlled movement of the actuator at the beginning of the testing cycle and finally to increase the safety of the operating staff. The structure and functionality of the designed control system, experimentally obtained results and evaluated stiffness characteristic of the tested spring are presented in the following chapters.

Laboratory tests of the hydraulic pump operating load with monitoring of changes in the physical properties

The present article deals with the physical properties monitoring of the transmission-hydraulic fluid, and changes of those properties due the operating load of the hydraulic pump in laboratory conditions. Tests of the transmission-hydraulic fluid were performed in laboratory conditions with the simulation of the operating load, so as to simulate the real conditions under which hydraulic circuit of the agricultural tractors operates. The universal transmission-hydraulic fluid was subjected to analysis, where the samples of the fluid were taken sequentially according to the chosen methodology at intervals of 250 and 500 h. The results of the present article include the evaluation of the physical properties of the fluid and the flow efficiency change of the hydraulic pump after 250 and 500 h of operation, while simulating the operation load. Based on a laboratory test, we found that after working for 500 h, the dynamic viscosity of the examined hydraulic fluid at 40°C decreased by 2.92 mPa.s and at 100°C decreased by 0.64 mPa.s. When determining the kinematic viscosity of the hydraulic fluid after working for 500 h, we recorded its decrease, namely, at a temperature of 40°C by a value of 3.37 mm2/s and at a temperature of 100°C, its value decreased by 0.77 mm2/s. In the analysis of the test oil samples, we found that the level of water contamination of the hydraulic fluid decreases with increasing number of hours worked. Specifically, the water concentration in the hydraulic fluid decreased by 0.031%. At the same time, we recorded a slight decrease in the flow efficiency of the hydraulic pump, specifically by a value of 0.03% after 500 h worked. After working 500 h, we found that the range of abrasion particles in the transmission-hydraulic fluid is within the prescribed range, which is determined by the standard D6595-00.

Asymptotic analysis of self-excited and forced vibrations of a self-regulating pressure control valve

Pressure vibrations in hydraulic systems are a widespread problem and can be caused by external excitation or self-exciting mechanisms. Although vibrations cannot be completely avoided in most cases, at least their frequencies must be known in order to prevent resonant excitation of adjacent components. While external excitation frequencies are known in most cases, the estimation of self-excited vibration amplitudes and frequencies is often difficult. Usually, numerical studies have to be executed in order to elaborate parameter influences, which is computationally expensive. The same holds true for the prediction of forced oscillation amplitudes. This contribution proposes asymptotic approximations of forced and self-excited oscillations in a simple hydraulic circuit consisting of a pump, an ideal consumer and a pressure control valve. Two excitation mechanisms of practical interest, namely pump pulsations (forced vibrations) and valve instability (self-excited vibrations), are analyzed. The system dynamics are described by a singularly perturbed third-order differential equation. By separating slow and fast variables in the system without external excitation, a first-order approximation of the slow manifold is computed. The flow on the slow manifold is approximated by an averaging procedure, whose piecewise defined zero-order solution maps the valve’s switching property. A modification of the procedure allows for the asymptotic approximation of the system’s forced response to an external excitation. The approximate solutions are validated within a realistic parameter range by comparison with numerical solutions of the full system equations.

A Survey of Powertrain Technologies for Energy-Efficient Heavy-Duty Machinery

This article presents a comprehensive, multidisciplinary overview of the development of powertrain technologies for energy-efficient heavy-duty earthmoving machines. The heavy-duty earthmoving equipment industry has been among the biggest contributors to emissions globally. However, due to high power demand and multidisciplinary powertrain structures, improving the energy efficiency of heavy-duty mobile machines has been a pressing and challenging task in the industry. To cope with this challenge, hydraulics and power electronics (PE) have been the key driving forces. As such, the relative developments in both fields are covered in this article. For hydraulics, developments of efficient hydraulic circuits will be overviewed in detail along with the introduction of hydraulic energy recovery technologies. In addition, developments of PE architectures in hybrid and electrified machines will be introduced. Furthermore, potential medium-voltage dc mining site power distribution and the valves of wide bandgap devices will also be discussed with the hope to open up new research opportunities in PE. Moreover, emerging hybrid electrohydraulic drive technology is introduced. Based on the overview in this article, it is anticipated that electrohydraulic hybridization will be the future trend in the earthmoving machine industry. Deeper collaboration between the two areas is desirable.

Measurement of fluid flow rate using nanocomposite silicone rubber sensor

This paper describes the use of an elastic nanocomposite sensor to measure the water flow rate in open and closed hydraulic circuits. A sensor was constructed of multiwalled carbon nanotubes (MWCNTs) dispersed in silicone rubber (SR) and subsequently tested to verify its ability to measure water flow rate. The results reveal that the correlation between the fluid flow rate and the pressure variation across the sensor entails that its electrical resistance can be correlated to the flow rate. The sensor constructed of 2 and 3 wt,% of MWCNTs in SR-based nanocomposite sensors exhibited a low percolation threshold. An electron microscope (HRSEM) was used to characterize the manufactured nanocomposite sensors and confirm the conductive networks. The variation in the electrical resistance of the sensor in terms of both water pressure and flow rate is described. The elastic sensor was calibrated to measure the water flow rate in the range of 0–35 l/min. The results show that an elastic sensor fabricated from MWCNTs dispersed in silicone rubber does exhibit sensitivity to the slight strain levels produced by dynamic water pressure and, as such, can be used to measure flow rate. In addition, the sensor's response to water flow in the presence of bubbles enables pump cavitation monitoring. This paper also investigates the reduction of sensor electrical conductivity in response to water immersion. The findings reveal that the elastic nanocomposite sensor could potentially be used as a liquid sensor to detect water leakage in hydraulic circuits.

Investigation of the influence of dimensions and material of the pipes on the water hammer effect in microbial fuel cells wastewater treatment plants

Water hammer is a transient flow phenomenon generated in a pipeline, when there is a sudden change in velocity, due to the closing of valves. This is particularly important for plants based on complicated hydraulic circuits and piping, to avoid malfunctioning in the urban sewer network. In this study, the effect of a set of parameters: length, diameter and material of the pipe with and without surge tank on transient pressure is investigated by using the software HAMMER V8i. The results show that the maximum Transient Pressure is strongly influenced by an increase of 41.24% of the pipe diameter when the Surge Tank is not present. When the surge tank is inserted the transient pressure increases only of about 12.2%. So the surge tank can have a positive influence on the entire network. Moreover, the increase in the length will lead to a decrease in the Total Pressure of about 10% without Surge Tank and of 8.62% with Surge Tank. While the change in the roughness coefficient of the material used for the pipes will cause a decrease in the Total Pressure of about 42.6%, without Surge tank, and of 12.2% with Surge Tank.

Design of Laboratory Test Equipment for Automotive Oil Filters to Evaluate the Technical Life of Engine Oil

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.

Semi-refined Crambe abyssinica (Hochst. EX R.E.Fr.) oil as a biobased hydraulic fluid for agricultural applications

Vegetable oils are well known for their potential applications in green chemistry, including use as hydraulic fluids. Among oilseed crops, Crambe abyssinica Hochst. EX R.E.Fr . gained attention for its low-input requirements during cultivation and for the properties of its oil, characterised by a high erucic acid content. This long-chain mono-unsaturated fatty acid provides appreciable features that make the oil suitable for interesting green chemistry sectors, as biolubricants and cosmetics. In the present work, Crambe oil was tested as a hydraulic fluid for sustainable agricultural applications. Crambe oil was partially refined through phospholipid removal and added with a food-grade antioxidant (tert-butylhydroquinone) at two different concentrations. The fluid efficiency tests were carried out using an experimental test rig, able to simulate a real hydraulic device, performing heavy work cycles at 40-MPa pressure and at 100 °C temperature, with the aim of strongly accelerating the ageing of the tested fluid. At a lower antioxidant concentration, 0.25 g kg−1, the oil underwent a very quick degradation process. However, increasing the additive dose to 2.0 g kg−1, the fluid maintained stable performances. Indeed, all parameters, referred to oil chemical-physical stability and technical performance, were constant along the entire work cycle, up to 290 h. Finally, the present work showed how Crambe seed cultivation, oil extraction and exploitation in the hydraulic circuit of farm machinery could be developed applying green chemistry approaches aiming at small-scale biorefineries linked to the local supply.

Design simulation and test of hydraulic control system of RFID reamer while drilling

With the gradual improvement of exploration and development in deep and ultra-deep Wells, the demand for slim-hole drilling is increasing day by day. However, both the phenomenon of neck constriction and drill-jamming accident occur from time to time in the drilling process, and the annulus clearance between borehole and casing is too small, which resulting in high slurry annulus pressure loss, low displacement efficiency and poor cementing quality. Therefore, a kind of RFID reamer while drilling has come into being, the reamer blades can be controlled to open and close with the aid of RFID tag recognition technology without increasing the drilling cost, so as to complete the reaming operation while drilling. Taking the hydraulic control system as the research object, the hydraulic circuit has been designed based on AMESim software in this paper, so has its dynamic performance simulation analysis been carried out, finally, the ground test has been completed, the results show that the hydraulic control system is capable of accurately identifying the RFID tag information to drive the reamer blades to open and close, the overall pressure loss of the tool is about 1.0 MPa as the blades opened completely, which meets the requirements of field test.