Hydraulic Oil Research Articles

Research and application of ultra-high pressure control system in strength tests

Based on the requirement of physical experiments, a ultra-high pressure control system which consisted of servo valves, a booster cylinder, and a multi-channel synchro-loading control system, was designed. A multi loop control strategy was adopted in this system, and hydraulic oil was loaded on the low-pressure side of the booster cylinder. In this way, the high precision control of low pressure increasing with high flow was attained, either was ultra-high pressure increasing, maintaining and reducing with low flow. The system was applied in a landing gear strength test successfully, the pressure control accuracy was smaller than 0.5 %, and the test task was completed satisfactorily.

Design and Experimental Verification on Performance of a Novel Integrated Electro-Hydraulic Vane Pump

The integrated electric-hydraulic pump has the advantages of no leakage, compact structure, and low noise. Here, we propose a novel integrated electric-hydraulic vane pump (IEHVP) to solve the problem of low reliability of the existing ordinary axially arranged hydraulic oil source in the harsh deep-sea environments. IEVP combines an external-rotor brushless motor and a balanced vane pump. In order to obtain the external characteristic curve of the designed IEHVP, the theoretical analysis of coupling analysis between the operating characteristics of the electric motor and the vane pump is designed. The results reveal that the output flow of the proposed IEHVP increases linearly with the increase of the input voltage and decreases non-linearly as the outlet pressure increase. Finally, the proposed IEHVP is tested. The relationship between the output flow and volumetric efficiency and its outlet pressure and input voltage is obtained. The experimental results verify the characteristics of the proposed IEHVP design.

A novel system identification method for servo-hydraulic shaking table using physics-guided long short-term memory network

Effective system identification is critical to realize the high-performance control of shaking table, however, the common reduced-fidelity models can rarely capture the practical dynamics of the system over a wide frequency range. To address this issue, this study adopts the latest advances in deep learning to develop a physics-guided long short-term memory (PhyLSTM) network for system identification of the shaking table. The basic idea is to embed the physical laws describing the system into the network, which can prompt the model to converge quickly to the right solution and constrain the output to a rational solution space in the case of poor data quality. To give insight into the operating mechanism of the shaking table, a series of tests were designed to reveal the flow properties of servovalve and the compressibility of hydraulic oil. Based on the above cognition, a testing program including various signals and specimens was conducted to complete data collection. After detailed hyperparameters testing, PhyLSTM exhibited far superior performance to traditional transfer function model, which indicated that PhyLSTM is a promising approach for shaking table modeling.

Design & Development of Electro Hydraulic Control Valve for Integration of Hoist and Steering System of a Dump Truck (35t)

The intent of this paper is to propose a system to control the steering operation and hoist operation of the Dump truck through combination of electro hydraulic valves and priority valve housed in Integrated manifold block. Electro hydraulic control valve(EHCV), and Electronic controller unit (ECU) for steering and hoist operation of the dump truck. The orbitrol valve consists of load sensing line, when the Orbitrol valve sense an effort on the steering wheel by the operator, the load sensing line will give a feedback signal to the electro hydraulic valve, which will divert the pressurized hydraulic oil to the steering system for steering operation, else the hydraulic oil is available for hoist operation. The hoist operation is control through Electronic Controller Unit (ECU). If there is no signal from the controller for hoist operation the hydraulic oil will flow back to tank. The Electronic controller will energize the combination of solenoid operated valves, depending upon the input received from operator through the momentary switch (Raise Switch, Lower/Float Switch, Hold Switch) mounted inside the cabin, which will allow the flow of pressurized hydraulic oil to the hoist cylinder for body raise and lower operation through electro hydraulic control valve. The electronic controller memorizes the signal from momentary switch and energizes the solenoids as per the logic till the next input signal receive by controller.

Investigation of the Relationship between Vibration Signals Due to Oil Impurity and Cavitation Bubbles in Hydraulic Pumps

Although hydraulic pumps are frequently used in daily life, improper use due to oil analysis or oil contamination is ignored. There is no instantaneous inspection; instead, the oil is changed periodically at certain times, whether it is contaminated or not. Hydraulic systems operate based on Pascal’s law, which states that the fluid will distribute the pressure equally to every point in a closed area. The fluid oil taken from an oil reservoir is moved into the pump by engine power. During this movement, as it passes through different pressure areas and different sections, undesirable events such as viscosity change and gas formation occur in the hydraulic oil. These formations collide with the outer walls and cause cavitation with respect to unwanted oil impurities. This cavitation causes unwanted vibration signals to occur in the normal working order of the system. As a result of cavitation, the particles that affect the lubricity and fluidity of the oil in the oil are mixed into the liquid and circulate freely. At the connection points, the blockage caused by the liquid in the pump cylinder block or the valve plate and the collisions of particles is effective. As a result, it creates vibrations of different frequencies. The frequency and amplitudes of these vibrations differ according to the degree of oil contamination. A method has been developed to find the degree of contamination of the oil circulating in the pump by looking at the amplitude and frequency of these vibrations measured from the motor body. There exist standards about the pollution of hydraulic fluid. With these standards, the maximum number of particles allowed for a given pollution level is defined. This topic is discussed in the conclusion to this study. This method has also been proven experimentally. Error and vibration analysis studies on pumps using a different approach are available in the literature. In these studies, pressure variation, total energy transmission, or artificial intelligence models were used to detect anomalies in the pump. In this study, the impurity rate of the oil was set at five different levels and the operating regime of the pump at each level was investigated experimentally. Rayleigh–Plesset and Zwart–Gerber–Belamri models, which are the most common cavitation models, were used to explain the bubble formation in the moving oil and the relationship of these bubbles with vibration. Frequency components were examined by the Discrete Fast Fourier Analysis method, where the operation of the pump was affected by the increase in oil impurity.

Research, calculation and selection of hydraulic oil water cooler for JKYB hydraulic explosion-proof hoist used at Duong Huy coal company

Hydraulic drive systems are commonly used in many different industrial sections. In the underground mining industry, in addition to ensuring transmission for big equipment, hydraulic equipment also must be fire safety. During the working process, the hydraulic oil gets hot and the viscosity decreases, it make the transmission power decrease. Due to the harsh actual working conditions of hydraulic equipment such as high working intensity, high working environment temperature, the oil cooler cannot cool the hydraulic oil to the required temperature. In order to choose the right type of oil cooler for hydraulic actuators, it is necessary to calculate the working parameters of the oil cooler according to specific working conditions. Currently, the selection of hydraulic oil coolers is often based on the experience of the designer, so it can lead to errors. In order to increase the reliability of the hydraulic oil cooler, this paper has built a calculation formula based on the thermodynamic theory and the heat transfer characteristic graphs in the catalogs of the hydraulic oil cooler. At the same time, the paper made an illustrative example for the selection of the hydraulic oil cooler of the JKYB hydraulic explosion-proof hoist used at Duong Huy coal company.

Comprehensive detection method for multi-contaminants in hydraulic oil based on inductance-resistance-capacitance analysis

Oil condition monitoring technology is a practical method for mechanical fault diagnosis, because oil contamination can directly reflect the lubrication and wear state. A comprehensive detection method based on integrated sensor consisting of an inductance-resistance sensing unit and a capacitance sensing unit is introduced in this article. Inductance parameter differentiates metallic debris, and the coil-based resistance parameter can detect smaller non-ferromagnetic metallic debris. Capacitance parameter is used to measure air bubbles and moisture, and the moisture measurement is not interfered by solid impurities. The simulation analysis showed that annular channel reduces the instability of inductive-resistive detection caused by position effect. The experimental results proved that the integrated inductive-resistive-capacitive sensor detects air bubbles, moisture, ferromagnetic debris and non-ferromagnetic debris by comparing multi-parameter signals. This method expands the detection range for oil contamination, and reduces the probability of incorrect particle counting and incorrect size measurement, which provides technical support for the intelligent operation and maintenance of mechanical equipment.

An Energy-Saving Position Control Strategy for Deep-Sea Valve-Controlled Hydraulic Cylinder Systems

The valve-controlled hydraulic cylinder system (VCHCS) is commonly utilized in the underwater manipulator, which is the most important tool for subsea tasks. Hydraulic oil viscosity is very sensitive to pressure. Therefore, when working at different depths under different ambient pressures in the sea, the hydraulic oil viscosity and the pipeline pressure loss in the deep-sea VCHCS vary greatly, which seriously affects the energy efficiency of the system. In addition, the control accuracy of the deep-sea VCHCS is also influenced by changes in the hydraulic oil viscosity and the pipeline pressure loss. In order to realize energy-saving control, this research introduces a proportional relief valve and develops a variable pump pressure control strategy. At the same time, a variable gain proportional-integral-derivative (PID) algorithm is designed to achieve precise control. A co-simulation model of the deep-sea VCHCS is then established, and many simulation analyses are carried out. Compared with traditional PID control with a constant pump pressure, the proposed method presents advantages such as lower energy consumption, better control accuracy, better resistance to load impact, and accuracy consistency under different working depths. Among them, when working at 11 km depth in the sea, the proposed method is capable of saving energy by 36.5% for the multi-step movement, by 30% for the harmonic movement, and by 47% for the complex movement. The present work in this research provides a solution that can realize energy saving and precise control of the deep-sea VCHCS at the same time in the wide span of depth in the sea.

Hydraulic Tests of the PZ0 Gear Micropump and the Importance Rank of Its Design and Operating Parameters

This article presents the results of hydraulic tests performed for a prototype gear micropump of a new design. The development of modern hydraulic systems is following two directions: the integration of hydraulic and electronic engineering and a reduction in the mass and the dimensions of the system. The scope of this research involved identifying static characteristics of the prototype gear pump, i.e., its efficiency, torque and power. The tests were performed for PZ0 pumps with the following specific deliveries (which are their design parameters), 0.25 cm3/rev, 0.315 cm3/rev, 0.5 cm3/rev, 0.8 cm3/rev, and 1.0 cm3/rev—with two different types of hydraulic oils, Azolla ZS 22 and HL 68. The operating parameters included the rotational speed, the discharge pressure and the flow rate. The obtained research results suggest an application of the decision tree induction-based classification method for identifying the most important design and operating parameters and their values influencing total efficiency. In addition, the article investigates the influence of rotational speed and specific delivery on total efficiency. The total efficiency translates indirectly into the energy consumption of the solution. The criterion of energy consumption is a key parameter for ecological and economical reasons, related mainly to future operating costs.

Investigation of catastrophic failure of API grade pipes used for hydraulic oil in an integrated steel plant

This paper investigates the mechanism of failures of API-grade seamless pipes. Two failures occurred, the pipe with the first failure had a 4.7 m long longitudinal crack, which occurred catastrophically. The pipe with the second failure had a small leakage. Pressure in the pipes due to hydraulic oil remains at 30–140 bar. The occurrence of large longitudinal crack at such low pressure and 25–40 °C of ambient temperature in the seamless low carbon steel hydraulic pipe requires a very high strain rate exerting on the pipe or hydrogen-induced-cracking (HIC) etc. Chemical analysis, tensile testing, hardness, visual observations, optical and electron microscopy, and Energy dispersive spectroscopy (EDS) were used to thoroughly evaluate the root cause of this failure and its mechanism. Results showed hydraulic pipe failed by HIC due to the presence of severe Sulphide inclusions. The most probable source of hydrogen in the pipe was hydraulic oil. Some mitigation measures were also proposed to prevent such failures in the hydraulic pipes of the unit.

Effect of temperature on sedimentation stability and flow characteristics of magnetorheological fluids with damper as the performance analyser

dimentation stability and high yield stress of a magnetorheological fluid (MRFs) are essential parameters for better damping performance for any practical application. Preliminary investigations have been carried out on carbonyl iron particles to determine the morphology, particle size, crystal structure, and saturation magnetization for their feasibility of synthesizing magnetorheological fluids in-house. This study synthesizes various MRFs from various commonly used carrier oils and additives. The MRF samples were prepared for 25% volume fractions of carbonyl iron (CI) powder in either silicone oil (350cSt) or hydraulic oil (50cSt) and by using lithium and calcium-based additives or a combination of both the additives. The sedimentation stability and yield behaviour at different temperatures show a remarkable drop in sedimentation rate and yield stress for all the MR fluid samples. The characterization of the prepared MR fluids reveals that MRF-1, MRF-3, MRF-5 are more stable and have high yield stress values. MRF-1 is selected to further characterize its dynamic performance in magnetorheological damper fabricated based on geometric dimensions obtained from the response surface optimization technique. The results indicate a 164.45% and 135.48% increase in damping force at higher amplitude and higher frequencies at 0A and 1A currents. Further, similar tests have been carried out by synthesizing MRF-7 with silicone oil (50cSt) + lithium base grease as the additive. The sample's stability and yield stress with temperature are carried out, and performance analysis shows a remarkable change in damping force than MRF-1. The dynamic range obtained is practically viable in MRF-7 than MRF-1, with less variability. Finally, temperature characteristics captured from the thermocouple of the MR damper reveal that an average of 43.78% reduction in damping force when the temperature is increased by 19.5 °C with increased dynamic range.

Investigation of the influence of hydraulic oil temperature on the variable-speed pump performance

This paper describes investigation on the influence of hydraulic oil temperature on the performance of a hydraulic pump. The aim of the research is to determine changes in volumetric efficiency of the pump in the form of maps of operation at different temperatures of the hydraulic oil, in conditions of variable speed and pressure. The described tests were carried out on an experimental stand with a hydraulic fixed-displacement gear pump controlled by a servo motor. Based on the signals from the sensors processed with the LabVIEW program, maps of the hydraulic pump operation were drown in a wide range of speeds and temperatures. The paper presents the results of the research and based on this the conclusions regarding the main aim of the research and others that were observed during the measurements were presented. The most important conclusion from the study shows that the temperature-dependent characteristics provide users with a significant amount of information such as operating conditions that will ensure a high level of efficiency.

HEAT EXCHANGER STUDY AND OPTIMIZATION APPROACH FOR ENGINE EFFICIENCY IMPROVEMENT

The scenario for the off-road machines during the next years will feature vehicles with relevant changes in terms, for example, of engine operative velocity and passive braking force reduction, with a concurrent increase (some 40 %) of thermal energy exchange needs by the heat exchanger. Engine, and hydraulic oil, temperatures will vary in function of actual requested power, to reduce the NOx production. This aspect, linked to the need to have an optimized engine layout (reduction of radiator dimensions) is the base of the work presented in the paper. The heat exchanger optimization is needed to obtain smaller, lighter, but at the same time more efficient, heat exchangers; this paper shows how it is possible to apply a CFD-mathematical approach on a cross-flow radiator with the aim to obtain a more efficient heat exchanger surface and reduced global dimensions. The approach used, and described in this work, made the performance evaluation possible not only on a single radiator, but on a complete production family variable both in dimension and technical characteristics. The approach is to split the exchanger into sub-domains having homogeneous boundary conditions, both in the cold and hot side, in order to collect on the WHTC (Wall Heat Transfer Coefficient) and the pressure drop. Individual results will be used as building blocks in order to have a reliable yet flexible estimate of the exchanger performance under different environmental conditions and dimensions. The results are encouraging and show the possibility to develop a new, optimized, radiator family, using a flexible and efficient design strategy. Keywords: heat exchanger, earth moving machineries, engine efficiency, optimization approach.

Effect of hydraulic oil compressibility on the volumetric efficiency of a diaphragm compressor for hydrogen refueling stations

The low volumetric efficiency of the diaphragm compressor under hydrogen refueling process, which hereby results in poor energy efficiency and high cost of hydrogen applications, should be paid attention to. This paper presents theoretical analysis and experimental investigation of the factors affecting the volumetric efficiency of the diaphragm compressor for hydrogen refueling process, focusing on the influence of hydraulic oil compressibility. A mathematical model was established to estimate the volumetric efficiency of diaphragm compressors, in which the effects of clearance volume, superheating of suction gas and pressure loss were taken into account and the emphasis was focused on the compressibility of hydraulic oil. A test rig was built to validate the theoretical model and further experimental investigations were carried out to identify the factors influencing the oil compressibility and hereby the volumetric efficiency. The volumetric efficiency was measured and compared under varied oil compressibility conditions by varying elastic modulus, oil overflow pressure and oil volume. The results indicated that the measured volumetric efficiency agrees well with the calculated value. The compression and expansion of hydraulic oil have a dominant influence on the volumetric efficiency, resulting in a loss of 37% of volumetric efficiency as compared to 2.4%, 18% and 1%, respectively for losses associated with clearance volume, superheating of suction gas and pressure loss, for a diagram compressor under refueling conditions with suction pressure of 30 MPa and discharge pressure of 90 MPa. The volumetric efficiency reduced rapidly with the increased oil overflow pressure, at a rate of 5% decrease with every 10 MPa rise in oil overflow pressure. As the oil volume increased by 100% of the stroke volume, the volumetric efficiency droped by 5.5%. • A volumetric efficiency model with oil compressibility effects was established. • Oil compressibility had a major effect on the volumetric efficiency. • Major factors on oil influencing volumetric efficiency were quantitatively estimated. • Oil volume should be designed less than 3 times stroke volume.

A physical model-neural network coupled modelling methodology of the hydraulic damper for railway vehicles

The dynamic characteristics of the hydraulic damper are time-varying in the complex working environment. To reveal the internal influence mechanism of the boundary conditions on the dynamic performance of the hydraulic damper and take it into account in the multi-body dynamics calculation, the laboratory test of the hydraulic damper is carried out firstly, and it is confirmed that the hydraulic damper has significant frequency-dependent and amplitude-dependent and temperature-dependent characteristics. Then, combining the physical parameter model with the neural network model, an accurate hybrid neural network model of the hydraulic damper is proposed. The physical parameter model considers the damper structure, including orifice, damping valve, rubber joint and the relationship between temperature and viscosity of hydraulic oil. The neural network model describes the personality characteristics of the hydraulic damper, such as oil leakage, the internal friction force and the percentage of entrapped air in oil. Finally, the responses and the dynamic parameters of the hybrid neural network model are calculated and compared with the experimental results by considering various exciting amplitudes and frequencies. The results show that the proposed model can fully simulate the dynamic performance of the hydraulic damper under various operating conditions.

An Experimental Investigation of Static Properties of Bio-Oils and SAE40 Oil in Journal Bearing Applications.

Considerable research has been conducted in the past decade and a half regarding the bio-lubricants potential to replace mineral-based lubricants as mainstream lubricants such as engine oil, hydraulic oil, compressor oil, and metalworking oil. This study studied several bio-lubricants (rapeseed oil, palm olein, and soybean oil) and a mineral-based lubricant, SAE40. The bio-lubricants have better physiochemical, tribological characteristics and environmental friendly nature, and are promising to replace mineral-based lubricants. In this study, a journal bearing test rig (JBTR) was developed in order to investigate the effect of journal speed on the temperature of oil film with time. Additionally, the load-carrying capacity of bio-oils was tested against the mineral-based lubricant SAE40 by adding a load on the journal. For all three speeds, i.e., 1000, 1500, and 2000 rpm, the bio-lubricants recorded minimum temperature. At 1000 rpm, rapeseed oil recorded a 9.2% lower temperature than SAE40. Similarly, at 2000 rpm, rapeseed oil recorded a minimum temperature that was 2.5% lower than SAE40; in comparison, at 1500 rpm, palm olein recorded a minimum temperature that was 1.8% less than SAE40. Overall, the results of this study revealed that bio-oils recorded a lower temperature rise than mineral oil. These results are very encouraging for further research in this area.

Analysis of the influence of hydraulic fluid quality on external gear pump performance

The basis of every hydraulic system is based on energy transformations, which are realized through hydraulic working fluid. Hydraulic oils are certainly subject to changes within their structure, meaning the basic characteristics and parameters of hydraulic oil, such as density, viscosity, humidity. The oils that are exploited are exposed to the process of degradation, which largely leads to significantly poorer quality of hydraulic fluid. The paper deals with the influence of changes in the characteristics of the hydraulic fluid on the hydraulic operating parameters of the gear pump installed on the hydraulic press. The parameters refer to pressure, flow, and temperature, as well as the quality of hydraulic oil, which affects the volumetric efficiency of the pump, and the results presented in the conclusion are based on the measured values of parameters before and after corrective measures. The control of parameters aims to increase the efficiency and reliability of the hydraulic system, a way of modern detection of deviations of parameters from standard, required values.

Determination of Fatigue Life and Failure Location of Vehicle Cylindrical LPG Fuel Tanks

Abstract This study addresses the determination of the fatigue life and its failure locations of the vehicle cylindrical LPG fuel tanks using both experimental and finite element analysis (FEA) methods. The experimental investigations performed as an accelerated fatigue tests are carried out using a hydraulics test unit in which the cylinders are internally pressurized by hydraulic oil. The LPG cylinders are subjected to repeated cyclic pressure varying from zero to service pressure of the tank. The FEA modeling of these tanks are developed in three dimensional (3D) using non-uniform geometrical parameters and nonlinear material properties. These models are also subjected to zero-based high cycle fatigue pressure load considering the stress life approach. The FEA modeling process is also simulated in non-homogeneous material conditions. Therefore, the fatigue life performance and failure location of the cylindrical LPG fuel tanks are predicted and compared to the experimental results.

Working Performance of the Deep-Sea Valve-Controlled Hydraulic Cylinder System under Pressure-Dependent Viscosity Change and Hydrodynamic Effects

The valve-controlled hydraulic cylinder system (VCHCS) is commonly used for actuators such as manipulators in deep-sea equipment, whose working performance is crucial to subsea tasks. Affected by the ambient pressure introduced by the pressure compensator, the viscosity of the hydraulic oil increases significantly. On this basis, the viscosity changes further when flowing in the slender pipeline, making the pipeline pressure loss substantially increase and subsequently affecting the working performance of the deep-sea VCHCS. Aiming at this issue, a detailed nonlinear mathematical model of the deep-sea VCHCS is established, in which the viscosity-pressure characteristics of the hydraulic oil is considered to take the viscosity changes in the pipeline into account. Besides, the hydrodynamic effects are also included in the model. Then the corresponding numerical simulation model of the deep-sea VCHCS is established, and its working performance at different depths is simulated and analyzed. When the depth is 11km, the extension and retraction movements are delayed by 52.50% and 43.12% respectively. The root cause of the delay is then analyzed and discussed. Finally, the parameters that affect the working performance are studied, and suggestions to reduce or eliminate the delay phenomenon are given. The results can provide theoretical support for the performance optimization of the deep-sea VCHCS.

Influence of Hydraulic Oil Viscosity on the Energy Efficiency of Hydrostatic Drive

Abstract The article presents the influence of oil viscosity on the overall efficiency of the compared systems with proportional cylinder control. There are energy losses in the elements of the hydraulic system, which are, among other things, a function of the viscosity of the working fluid used, as well as energy losses which are practically independent of the viscosity. In order to assess the possibilities of saving energy during the operation of the hydrostatic drive system, it is necessary to understand and describe the losses occurring in the system. Determining the energy efficiency of the system can be performed simulation with the help of a computer program using an appropriate mathematical model. The efficiency determined in this way can be used in the process of designing and operating the system.