Water Hydraulic Pump Research Articles

Evaluation of tribological behavior of tribopairs in water hydraulic radial piston pumps with multiple coatings and lubrication

Evaluation of tribological behavior of tribopairs in water hydraulic radial piston pumps with multiple coatings and lubrication

Performance study of an energy harvester with multiple piezoelectric disks in parallel connection for water pressure pulsation

Water hydraulic pump is a crucial component of the water hydraulic system, and it generates periodic pressure pulsation due to its inherent characteristics. To harvest the vibration energy from the pressure pulsation, an energy harvester with multiple piezoelectric disks in parallel connection is proposed. Two prototypes are fabricated to analyze the effect of the number of piezoelectric disks on the energy harvesting characteristics under different pressures and resistances. Parameter matching is also carried out to obtain high root mean square (RMS) voltage and average power. For both prototypes, the cyclical change of deformation is caused by the pressure pulsation, leading to transient variation of voltage. Moderate thickness of piezoelectric ceramic and small thickness of copper substrate are advantageous for generating higher electrical energy output. Pressure pulsation significantly affects the harvested voltage and power, with the main influencing factor being the pulsation amplitude rather than static pressure. Additionally, transient voltage and RMS voltage increase with increasing resistance, while average power first rises and then falls. Comparing the two prototypes, both voltage and optimal resistance decrease when the number of piezoelectric disks in parallel connection increases. The average power and power density with two piezoelectric disks can reach 447 μW and 4.56 mW cm−3 under 3 MPa and at a resistance of 20 KΩ. This research provides guidance for the design, optimization and application of piezoelectric energy harvesters in water hydraulic system.

Design and experimental validation of a valve-distributed water radial piston pump

In underground coal mining, there is an urgent need for reducing the noise, hydraulic shock, and leakage of reciprocating pumps. Flow pulsation is strongly dependent on the number of pistons for single-acting reciprocating pumps. Water hydraulic radial piston pumps (RPPs) allow the pistons to be radially distributed, which makes the multi-piston design easier compared to traditional single-acting reciprocating piston pumps. In this study, a novel valve-distributed water RPP was developed in which the star wheel assembled on the camshaft is used to drive the connecting rod-crosshead-piston assembly and realize the reciprocation of the piston and suction-discharge of the pump check valves. Mathematical and numerical models representing the RPP were built using MATLAB and AMESim, respectively. Three-dimensional computational fluid dynamics analyses were performed to investigate the internal flow field of the suction and discharge circuits as well as the flow characteristics of the discharge valve opening. A prototype pump was manufactured and tested for 200 h and then disassembled to evaluate the wear condition. The tested instant flow rates were lower than those obtained from the theoretical and simulation analyses. The experimental results also revealed that the average flow rates were almost independent of the output pressure and that the volumetric efficiency decreased with increasing rotational speed when the output pressure was larger than 25 MPa. Inspecting the disassembled water RPP revealed that scuffing problems occurred in the pistons, whereas the other components remained intact. The findings of this study offer a reference for water hydraulic power units in various applications and for investigating the intensity of water hydraulics.

Characteristic Study of a Valve-Matched Flow Single-Piston Miniature Water-Hydraulic Pump

Characteristic Study of a Valve-Matched Flow Single-Piston Miniature Water-Hydraulic Pump

Design, simulation and experiment for a piezoelectric energy harvester based on fluid pressure pulsation in water hydraulic system

Water hydraulic pump is an essential component of water hydraulic system, and periodic pressure pulsation is generated during its operation. A hydraulic piezoelectric energy harvester (HPEH) with excellent sealing and insulation performance is proposed to recover the vibrational energy from pressure pulsation. The energy harvesting performance of HPEH is investigated through simulation and experiment under different parameter combinations. The results show that the transient voltage and transient pressure exhibit the same fundamental and harmonic frequencies. Higher pressure amplitude is favorable for deformation and can lead to higher electric energy generation, but the static pressure has little effect on the energy harvesting performance. Although the voltage increasing with increasing the resistance, the average power increases first and then decreases. Compared with the existing piezoelectric energy harvesters, the present HPEH has advantages in voltage and power density. The root mean square voltage, average power and power density can reach up to 9.9 V, 791.7 μW and 2.067 μW/(bar·mm3), respectively. Moreover, 42 LEDs connected in parallel are lighted to demonstrate the feasibility of using the HPEH as a power source. This study can lay a foundation for driving low-power components using piezoelectric harvesting energy from pressure pulsation in water hydraulic system.

Effect of Material Selection and Surface Texture on Tribological Properties of Key Friction Pairs in Water Hydraulic Axial Piston Pumps: A Review

A water hydraulic axial piston pump has become the preferred power component of environmentally friendly water hydraulic transmission systems, due to its advantages of a compact structure, high power density, and so on. The poor friction and wear performance in the water medium, especially under extreme conditions of high speed and high pressure, limit the engineering application of the water hydraulic axial piston pump. In this review, the research progress for key friction pair materials (such as special corrosion-resistant alloys, engineering plastics, and engineering ceramics) for water hydraulic axial piston pumps is, firstly, summarized. Secondly, inspired by nature, the processing methods, lubrication drag-reduction mechanism, and tribological properties of the biomimetic surface textures are discussed. The effects of the surface texture shape, equivalent diameter, depth, and arrangement on the pump’s tribological properties are reviewed in detail. Finally, the application status of, and problems with, surface texture technology in water hydraulic axial piston pumps are summarized. It is suggested that future studies should focus on the multi-field coupling lubrication anti-friction mechanism of the multi-type composite texture under extreme conditions and mixed lubrication; and the anti-wear performance of the texture coupled with a coating modification, to further promote the surface texture in the field of lubrication antifriction engineering applications.

Tribological behavior of tribo-pairs in water hydraulic radial piston pumps

Friction and wear tests were performed on five Cu-based materials and three polyether ether ketone (PEEK)-based composites sliding against 17-4PH and 42CrMo4 coated with tungsten carbide-reinforced Ni-based coating. Two types of pin-on-disk specimens were used to represent the slipper/eccentric drive and piston/sleeve gap seal tribo-pairs in water hydraulic radial piston pumps. The experimental results showed that the QSn8-0.3 slipper material exhibited the highest steady-state friction coefficients for sliding against both 17-4PH (0.156) and coated-42CrMo4 (0.894). Glass fiber-reinforced PEEK exhibited the highest steady-state friction coefficients for sliding against the two specimens (0.540 and 0.420). The ZCuPb15Sn8/17-4PH showed the highest wear rate for the representative slipper/eccentric drive tribo-pair (26.86 × 10−6 mm/Nm); glass fiber-reinforced PEEK/17-4PH showed the highest wear rate for the representative piston/sleeve gap seal tribo-pair (46.91 × 10−6mm/Nm). The wear mechanisms of the two types of tribo-pairs were characterized through scanning electron microscopy, profilometry, and energy-dispersive spectroscopy analyses. Furthermore, the effects of hardness, pv values, coating, and reinforcement on the tribological behavior of the two types of tribo-pairs were analyzed.

Experimental Research of the Hydrodynamic Processes of an Axial Piston Water Hydraulic Pump

Water hydraulic components and systems play pivotal roles in the development of modern hydraulics. Sustainable development and environmental protection cannot be imagined without the use of water as a working medium in modern hydraulic systems. An axial piston pump is the main component of these systems. This paper presents analytical and experimental methods for the development of an axial piston pump. The presented mathematical model is rooted in numerous research results in the literature and in our own experience. It is based on mathematical modelling of hydrodynamic processes of a water hydraulic axial piston pump which, combined with experimental research, provides a great tool to analyse the influence of different factors on the operating process and to optimise the pump parameters. The experimental equipment used in our tests simulates a real hydraulic installation, and the obtained results are very close to the actual operating parameters. This research included a modification of the swash plate in order to achieve ideal operating parameters and, thus, extend the service life of the pump. Water has a number of advantages over conventional hydraulic oils. It is a sustainable, environmentally friendly resource, more readily available than oil (lower transportation costs), cheaper to dispose of, non-flammable and non-toxic, and its high thermal conductivity aids in cooling.

Research on Seawater Hydraulic Internal Ball Gear Pump

With high demands for novel technologies in the marine mechatronic instrumentality and the limitations of the present hydraulic pumps, a novel bidirectional seawater hydraulic internal ball gear pump is proposed to accomplish the function of fluid power transmission and control. The proposed hydraulic pump can be used for hydraulic buoyancy control systems of underwater vehicles and different marine mechatronic equipment. In this paper, the model, the meshing and the flow characteristics of the internal ball gear pump are developed. The radial unbalance force of the pump, leakage, and flow pulsation are also analyzed. The new type of eccentric shaft-hole rotary sealing designed in this paper can eliminate axial leakage and is expected to improve volumetric efficiency, working pressure, and power density. Simulation and experimental results show that: (1) by using the concave/convex ball gears rather than the existing gears, the concave ball gear drives the convex ball ring to rotate, realizing energy transfer and conversion; (2) compared with the water hydraulic internal gear pump, the internal ball gear pump has excellent performance. Experimental results also show that when the speed is 1500 rpm, the maximum operating pressure can reach 7 MPa. At 2 MPa, its volumetric efficiency and flow can reach 75% and 0.189L/min, respectively. The outcomes of this study show that the proposed seawater hydraulic internal ball gear pump is effective and has a lot of potential.

Research on the Friction Pairs in Water Hydraulic Piston Pumps

Power control hydraulics (PCH) has one of the most versatile research fields and technologies that has many applications especially in the mechatronic industries. It also comes with drawbacks especially with issues concerning the use of mineral oil as a pressurized fluid in most of it applications. Furthermore, in the mechatronic field, researches in the ocean environment has become more difficult due to mineral oil incompatibility with the ocean water. One of the most accepted solution is to find alternatives to mineral oil as a PCH pressurized fluid which has led to water being the safest candidate. As a result, more researches have been carried out on water as a pressurized fluid in PCH systems. Axial hydraulic piston pump has been one of the best pumps for PCH systems. It was realized in this paper that, more options for material selection for the friction pairs were available and therefore water hydraulics can realize its main goals of providing a safe environment as well as being cost-effective. This paper seeks to review the various material friction pair selection that has been suggested by various researchers in this field and analyze their various methodologies and experimentations.

Wear failure analysis of suction valve for high pressure and large flow water hydraulic plunger pump

The failure mechanism of suction valve in high pressure and large flow water hydraulic plunger pump used in coal mine is studied. Previous studies believe that in traditional plunger pump with low pressure and small flow, the impact caused by the dynamic contact between the valve plate and the valve seat is the main reason for the performance deterioration of suction valve. However, in the practical use of high-pressure and large-flow hydraulic plunger pump, it is found that there are signs of rotating wear and material loss on the sealing surface of the suction valve plate. In order to explain the premature failure of the valve, the mathematical model of the force and movement of the valve plate during the suction process of the high-pressure and large-flow hydraulic plunger pump is established. Three-dimensional computational fluid dynamics (CFD) method and nonlinear finite element method are used to numerically analyze the operation process and dangerous conditions of the valve plate. The results show that under the action of the uneven flow field, the combination effects of low speed rotation and heavy load during closing process is the key factor causing material loss. According to the microstructure and elemental composition of the worn surface, the specific wear failure mechanism is determined, and the effectiveness of the numerical method is verified. Finally, the improved valve plate materials are proposed. The field test of high pressure and large flow pump proves that the wear of the valve plate is significantly reduced after the improvement.

Internal Leakages in a Water Hydraulic Pump with Gears From Plastic

Plastics are used more and more in hydraulic systems. The chemical properties of the plastics favour the use of working fluids alternative to mineral oil, e.g. water. The conditions in the manufacturing process, e.g. injection moulding, limit the achievement of high working pressures in the hydraulic elements. Internal leakage reduces the efficiency of the hydraulic pump with plastic gears. The article presents the results of internal leakage tests of a water-supplied hydraulic pump. Gears made of various materials (PPS+GF40 and PEEK) have been used in the research, made by two methods: injection moulding and machining. A simplified mathematical model of the dependence of leakages on pressure and rotational speed has been developed. The influence of the materials and manufacturing methods used on the pump operation is discussed.

Design of the swash-plate water hydraulic pump for environment-friendly actuator systems

This paper deals with a new development of a swash-plate hydraulic pump. It is particularly designed to aim its usage in applications where environmental impacts should be concerned. Thus, the pump is based on not mineral-based oil but simple tap water. The Electro-Hydraulic Actuator (EHA), a linear motion generator operated by an electric motor installed to the proposed pump, can be attractive and expandable to small-to-medium pressure applications. Water is clean and safe, and the size of EHA is relatively small. New design features of the pump including the no-shoe retainer, the inclination angle adjustment screw, the rotating cylinder block, and the simple assembly structure enabled EHA. The pump was designed to have its static pressure of 1.4 MPa and the volumetric flow rate of 10 × 103 mm3/s. To verify its performance, a series of experiments were constructed, and the maximum volumetric flow rate and pressure were found as 2935.87 mm3/s and 1.9 MPa, respectively. The maximum velocity of the actuator stroke was 9.35 mm/s. The EHA is controlled directly by the electric motor, and so a directional valve is not necessary. It is concluded the pump can be successfully used in small-to-medium pressure applications.

Theoretical Analysis of a Water Hydraulic Internal Ball Gear Pump

In view of current volumetric water hydraulic pumps, especially water hydraulic internal gear pumps, a scheme of an internal ball gear pump was proposed. Its working principle was expounded and the calculation methods of its performance parameters such as displacement, flow pulsation and maximum speed were studied. Compared and analysed the advantages and disadvantages of traditional displacement water hydraulic pump with ball gear pump, and its key basic technologies. The results show that (1) by engaging the concave/convex ball gears instead of the gears, it can realize the function of the pump; (2) the arrangement of multiple rows of radial staggered not only ensures the continuity and stability of the transmission, but also solves the phenomenon of water trapping; (3) displacement is proportional to the diameter of the ball (modulus) while flow pulsation is inversely proportional to the number of rows of ball gear. Also, the maximum speed is inversely proportional to the diameter of the concave ball gear and the density of the working medium, which is proportional to the inlet pressure of the ball tooth pump, etc... This study could lay a simple theoretical foundation for the development of high-performance water hydraulic internal ball gear pump.

Extrusion-occlusion dynamic failure analysis of O-ring based on floating bush of water hydraulic pump

The sealing structure of the floating bush is used to connect the cylinder barrel and the valve plate and compensate for the inconsistency of the motion, which is caused by the offset of the cylinder barrel under the external load and the dynamic pressure of the water film. In the process of compensation, the alternative change of clearance size between closing ring and piston bush and the abrupt change of fluid pressure on O-ring make the O-ring extrude and occlude continuously, leading to seal failure and reduced service life. The sealing performance and service life of the O-ring directly affect the working performance of water hydraulic pump. Failure of the O-ring will lead to lower efficiency of water hydraulic pump. In this paper, the geometric relationship of the O-ring is obtained by analyzing the force and motion of cylinder barrel in offset state. Based on Mooney-Rivlin constitutive relation of the rubber material, a two-dimensional finite element model is established. The fluid pressure load and the swing load of the piston bush are applied. The dynamic equivalent stress and contact stress are analyzed, under the limit conditions of the O-ring assembly, loading fluid pressure and swing occlusion. The failure parts and causes are determined, which provides a theoretical basis for the optimization of the sealing structure of the floating bush.

Measurement of water permeation through membranes from extremely high hydraulic pressure to atmospheric pressure

The performance of electrochemical hydrogen compressors (EHCs) with polymer electrolyte membranes which work in the presence of water is affected by the flooding; however, the water permeation through the membranes from the high-pressure side (dozens of MPa) to the low-pressure side has never measured. In this study, a method to measure the permeation from the high hydraulic pressure side (2–20 MPa) to the atmospheric pressure side is shown, using EHC cells and a water hydraulic pump. By this method, liquid-liquid permeation (LLP) and liquid-vapor permeation (LVP) were measured. The higher the hydraulic pressure was, the more the water flux was, and the increase in the permeation was large for LLP. It is considered that the electro-osmotic drag accumulates water on the cathode at low pressure during the initial stage of the electrochemical hydrogen compression and then the permeation from the cathode to the anode exceeds the electro-osmotic drag as the cathode pressure increases, which causes the decrease in the performance by flooding.

Tribological Performance of CF-PEEK Sliding against 17-4PH Stainless Steel with Various Cermet Coatings for Water Hydraulic Piston Pump Application

To improve the abrasion resistance performance of the critical tribopairs within water hydraulic piston pumps, tribological characteristics of the stainless steel 17-4PH and 17-4PH coated with Cr3C2-NiCr, WC-10Co-4Cr, Cr2O3 and Al2O3-13%TiO2 sliding against carbon fiber reinforced polyetheretherketone (CF-PEEK) composite under water-lubricated condition were experimentally studied using a pin-on-ring test bench with different working conditions. It has been demonstrated by the experimental results that the tribological behaviors of CF-PEEK/cermet coatings tribipairs were better than that of CF-PEEK/17-4PH tribopair under water lubrication. However, the Cr3C2-NiCr coating could be damaged under high rotational speed. Due to the reaction film produced by the Al2O3-13%TiO2 and water, the CF-PEEK/Al2O3-13%TiO2 material combination exhibits more excellent tribological behaviors than other tribopairs lubricated with water, and could preferentially be used in water hydraulic piston pumps.

Direct and indirect corrosion wear performance of AISI 630 steel for the slipper/swashplate pair in a water hydraulic pump

To explore feasibility of AISI 630 steel applied to slipper/swashplate pair of a water hydraulic pump. Frictional corrosion experiment simulating slipper/swashplate pair operation was systematically conducted under three different lubricating conditions, and the influence of lubricating medium and solution aging on corrosion wear of AISI 630 steel and indirect corrosion wear of its dual PEEK surface were evaluated by means of scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical corrosion test analysis. It was shown that synergistic effect of corrosion and wear played an important role on wear of AISI 630 steel and occupied up to 25% of its total wear loss. Solution aging of AISI 630 steel could help to decrease wear rate of its dual PEEK surface in freshwater, but would significantly increase friction coefficient and wear rate of AISI 630 in seawater and aggravate the wear and indirect corrosion wear of its dual PEEK surface. Therefore, for the water hydraulic slipper/swashplate pair, it is suggested that when taking service in freshwater, solution aging of AISI 630 steel can be considered to alleviate wear of its dual PEEK surface, but when taking service in seawater, solution aging is not recommended, and the original AISI 630 steel is more conducive to obtain preferable friction and wear performance.

Aqua Drive Systems and Methods of Testing Water-Hydraulic Pumps

Aqua Drive Systems and Methods of Testing Water-Hydraulic Pumps

Simulation Investigation on Application of Powder Metallurgy Damping Effect in Water Hydraulic Pump

Over the years, the hydrostatic balance slipper is often used to make the hydraulic lubrication film formed between the swash plate and the slipper. In this paper, a slipper containing the powder metallurgy (PM) composite material is proposed. The porous characteristics have an automatic damping effect, which can improve the tribological characteristics of the slipper. Based on the Reynolds equation, porous Darcy law and continuity equation, a lubrication model of PM damper is proposed to analyze the damping effect of PM in this paper. The proposed model is calculated using the finite volume method to capture the water film characteristics. Effects of length, diameter and porosity of the PM damper on the water film thickness are investigated. The results show that the water film can be formed by adopting the PM damper. In order to ensure the slipper with PM damper to form hydrostatic support, the length, diameter and porosity of PM damper is recommended to be 5 mm, 8 mm and 0.7, respectively.