Radial Piston Pump Research Articles

Design and Sensitivity Analysis of Mechanically Actuated Digital Radial Piston Pumps

One major challenge in fluid power is the improvement and optimization of the efficiency of mobile hydraulic systems. Conventional fluid power systems often exhibit relatively low overall efficiencies caused by inefficiencies in the various components, such as a prime mover, variable displacement pump, valves, fittings, hoses, and actuators. While each component contributes to the losses in the overall system, the pump converts the mechanical shaft energy from the prime mover to energy transmitted hydraulically and is one of the most crucial components impacting overall system efficiency. Using on/off technologies, new pump architectures have enabled the opportunity to increase the efficiency over conventional designs using positive sealing valves in place of conventional port plate designs. This work proposes, investigates, and assesses the development and optimization of a digital variable displacement pump using a novel cam actuation technique on radial piston pumps. The novelty of this work is the development and parameter optimization of a mechanically actuated digital radial piston pump that can achieve high efficiencies from minimum to maximum displacement compared to common conventional variable displacement pump technologies. In this study, a sensitivity analysis is conducted to study the parameters of the system to optimize the pump. The parameters assessed in this study include: the valve bore size, cam transition and compression angles, piston diameter, and dead volume in the pumping chamber. The simulation results show that after optimizing the parameters of the system, the pump in design could reach a maximum efficiency of approximately 93% and was capable of upholding efficiencies above 80% between 30–100% displacement.

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.

Design and Verification of a Flow Distribution Structure for a Water-Based Radial Piston Pump

Design and Verification of a Flow Distribution Structure for a Water-Based Radial Piston Pump

RADIAL PISTON PUMP WITH A COMPENSATING STATOR PROFILE FOR ELIMINATE FEED LOSSES DUE TO FLUID SUBSIDENCE

In this work, we consider an unregulated radial piston pump with a compensating profile of the stator surface. This design eliminates feed losses due to dynamic compression and subsidence of liquid in the working chamber under the pressure formed in the operating hydraulic system. Radial piston hydraulic machines operate at pressures of 40 – 60 mPa and higher. At a pressure of 45 mPa, i.e., the case considered in the paper, the volume of liquid subsidence in the working chamber and the connecting channel reaches almost 3 %. This results in a hydraulic shock that reduces the volumetric efficiency of the pump. The level of linear subsidence, equivalent to the reduction of the plunger stroke, equals 2.54 mm at a working chamber diameter of 25 mm, which is more than 10 %. According to the level of linear subsidence, the stator inner surface correction parameter δst is set, which increases the plunger stroke and displaced fluid volume as if the pressure in the hydraulic system were zero. The dimensions of the plunger shank are calculated, at which the suction conditions do not deteriorate while the subsidence is reduced to 2.6 % due to decreasing the volume of the connecting channel of the pump working chamber.

Digitalization of Radial Piston Pumps through Internal Mechanically Actuated Designs

Digital hydraulics is a technology gaining perceptible growth in fluid power research. The advantages of digital fluid power systems can be realized through improved system efficiencies, energy savings, increased productivity, and system performance compared to traditional fluid power systems. Conventional check valve pumps use differential pressures to deliver pressurized flow to the system. Digital fluid power pumps enable conventional check valve pumps to achieve variable displacements by enhancing the controllability of the inlet and outlet valves through digital hydraulic technologies and techniques. The benefit of this technology is the use of positive sealing check valves with lower leakage losses compared to typical variable displacement pumps, increasing the unit’s overall efficiency. The primary focus of prior digital pump/motor research has been on digital actuation using electronic solenoids to actuate or latch the valves. While these electrical systems provide a platform for digital hydraulic techniques, they come with a cost: added energy sources, advanced controls, and expensive data acquisition systems. Research has also shown that minor valve timing inconsistencies can limit the potential energy savings of digital pumps in electrically actuated systems. A system configuration that promotes the advantages of digital hydraulics while mitigating the disadvantages associated with electrical systems is mechanically actuated systems. This work discusses variable cams and their advantages/disadvantages in digital radial piston pump/motor technologies. The significance of this work is the investigation of the digitalization of radial piston pumps through mechanically actuated valving systems, which has yet to be implemented in prior research. This paper evaluates various design concepts for commercializing digital radial piston pumps using mechanically actuated cams. A two-quadrant pump and a four-quadrant pump/motor design are simulated to assess their potential efficiency across the bandwidth of their displacement. The results show that the two systems can achieve relatively high efficiencies across their displacement bandwidth but show room for further improvement by optimizing these systems. This study is the first step in designing an integrated mechanically actuated variable cam system in digital radial piston pumps.

Analysis of lubricating characteristics of high-pressure radial piston pump with thermo-elastohydrodynamic coupling

The behavior of piston-cylinder interfaces takes important influences on lubricating characteristics of the high-pressure piston pump. For the sake of revealing the lubricating characteristics of radial piston pumps, a transient thermo-elastohydrodynamic lubrication model to analyze the interface between piston and cylinder is established with considering the effects of the bushing elastic deformation, viscosity-temperature-pressure, heat conduction and piston tilting, on the basis of coupling the finite element method and finite difference method. Furthermore, the influences of design parameters (camshaft speed, inlet pressure and average clearance) on the load carrying capacity, leakage, viscous friction, and temperature rise of the friction-pair interfaces are analyzed. The results indicate that the average clearance has the most significant influence on the lubrication performance. Increasing the average clearance from 2 to 6 μm resulted in a substantial decrease in load carrying capacity by approximately 50% and friction force by approximately 65%. The temperature rise showed a significant reduction of 55%, while the leakage increased by approximately 3-fold.

Effect of Silencing Groove in Valve Plate on Efficiency of Radial Piston Pump

Effect of Silencing Groove in Valve Plate on Efficiency of Radial Piston Pump

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.

Analysis of pressure at transition zone of valve plate of radial piston pump

In present studies focuses on the characteristics of flow-pressure of piston cylinder barrel and silencing groove chambers near the transition zone of valve plate of a fixed displacement radial piston pump. The designing of silencing groove of valve plate of the pump is carried out with appropriate geometrical configuration, compute the orifice area of piston kidney over the silencing grooves and manifolds, the interaction area make a key role in fluid flow interaction. The pressure and flow of pump is analyzed in consideration the silencing groove as separate control volume from manifold, each silencing groove chamber is connected to the both end of the manifold chamber, the shape of the silencing groove is an asymmetric tetrahedron. The radial piston pump is modelled in simulation with consideration of five pump pistons barrel, analyses the pressures near at transition zone with different bridge angle. The flows interaction of pump piston cylinder barrel with silencing groove chamber and manifold chamber are also carried out. The overall pump volumetric efficiency, flow and pressure fluctuation of radial piston pump are analyzed to optimize the pump.

Reduced Flow Fluctuation of Radial Piston Pump with Silencing Groove Valve Plate

The theoretical study and numerical analysis have been carried out on the valve plate geometry of the radial piston pump to reduce the flow and pressure fluctuation. The radial piston pump is widely used in industrial applications as a hydraulic power source. The pressure and flow fluctuation of pump produce an adverse effect for the hydraulic system. The geometries of valve plate are studies for the analyses of pressure and flow fluctuation of the pump. The explicit area calculation of the piston kidney over the manifold is carried out to simulate the main flow in between piston chamber and manifold in vale plate configurations of with silencing groove, without silencing groove and with silencing groove cum damping orifice. The analyses of cross-port leakage is done at transition zone near at top dead centre (TDC) and bottom dead centre (BDC) of the valve plate, study the effects of cross-port leakage on pressure and flow fluctuation with volumetric efficiency of the pump. Studies the pump pressure and flow build up characteristic under varying load and validated with existing pump performance. The simulation results suggest that the silencing groove valve plate model is better perform than other configurations in terms of high flow rate, low pressure and flow fluctuation with less cross port leakage and more volumetric efficiency.

Pressure control of fixed displacement variable speed radial piston pump using PID controller

In the present studies attentive to control the variable pressure of fixed displacement variable speed radial piston pump by controlling the angular speed of pump-motor system with a PID controller at ramp and wavy type load. The pressure-flow simulation of pump designed in MATLAB Simulink with an appropriate silencing groove valve plate of the pump. The proposed PID controller designed in Simulink framework to control the pump-motor speed to accomplished the demand pressures at ramp and wavy type load and the load accustomed by varying the needle valve orifice area. PID controller gain value optimised by minimising the tracking error of the pump pressure responses.

Low-speed radial piston pump as an effective alternative power transmission for small hydropower plants

Low-head hydropower bears tremendous potential as a renewable energy source, especially in the context of the progressing global warming. In locations with a low head, for economic and environmental reasons, a small hydropower plant with a waterwheel and an asynchronous generator may provide the best solution for sustainable electricity production. The purpose of this study is to demonstrate a new type of low-speed radial piston pump intended to be part of the hydrostatic transmission of such a small hydropower plant. The advantage of the transmission is the possibility of stepless, automatic change of the gear ratio during operation. First, we describe a mathematical model of the proposed pump and subsequently demonstrate a test stand equipped with its prototype with three suction-pressure units. The pump flow rate characteristics calculated using the theoretical model were compared with those obtained from experiments, resulting in the determination and characterization of the pump's efficiency. Supplementary experiments with a hydraulic accumulator installed as part of the investigated system, demonstrated the possibility of flow rate pulsation dampening. The experimental results showed the validity of the developed mathematical model. In conclusion, the correct operation of the pump was corroborated, and its potential application confirmed by the efficiency results.

Design and theoretical analysis of a liquid piston hydrogen compressor

Hydrogen is widely considered to be the ultimate energy source and has received significant attention from research institutions. Compressors are widely used as the core device for increasing the volumetric energy density of hydrogen. However, conventional reciprocating compressors have problems, such as complex structure, frequent breakdown and large impact. This paper proposes a liquid piston compressor for hydrogen compression. Firstly, the structure and working principle of the compressor are introduced. The compressor adopts a five-stage compression structure, which is driven by a five-piston radial piston pump, and the corresponding hydraulic control system is designed. Secondly, to reduce the return shock of the compressor, the buffer structure is designed for each stage of compression, and theoretical analysis is performed to obtain the theoretical output flow rate of the compressor and the kinematic characteristics of the inlet and discharge processes. Finally, combined with the AMEsim software, the motion of the compressor piston and the characteristics of pressure change during the entire working process in the compressor are simulated. Results show that the novel multi-stage compressor can achieve stable and continuous hydrogen compression, and the buffer structure of each stage greatly reduces the piston impact on the compressor. Compared with the traditional liquid piston compressor, the proposed compressor solves the problems of unstable operation and reduced compression efficiency caused by leakage and reduces the impact and vibration of the piston and increases the stability and controllability of the compressor operation. The analysis results show that the solution is feasible.

Pressure control of variable displacement radial piston pump with PID controller

This paper is focused on the control of pressure of the variable displacement radial piston pump (VDRPP) using a PID controller with an appropriate valve plate. This investigation is based on MATLAB Simulink. The valve plate is the main anti-frictional component of the piston pump and the material used for this component has been selected high-quality stainless-steel alloy to reduced leakage, more strength and improved volumetric efficiency. A variable displacement radial piston pump (VDRPP) has variable flow discharge, and displacement is changed by changing eccentricity. The area of the piston port over the manifolds is designed in the form of a mathematical equation. The pressure control of the pump by using the dynamic response of the actuator is control with a solenoid spool valve. Analyses the pressure characteristics, flow characteristics and the flow fluctuation of variable displacement radial piston pump with leakage flow through the valve plate and cylinder block.

Modeling and theoretical study of relief chamfer method for reducing the flow ripple of a spool valves distribution radial piston pump

This paper presents a study of flow ripple reduction method of a spool valves distribution radial piston pump (SVDRPP). Relief chamfers are adopted to prolong and moderate the opening processes of the delivery spool valves, thus to relieve the pressure surges as well as the consequent flow ripples, vibrations and noises. The mathematical model of this method is established and multiple numerical simulations are conducted to analyze the mechanism as well as the effectiveness of this method. According to the simulation results, different relief chamfer angles have varying influences on flow ripple reduction. Remarkable reduction of flow fluctuation from 43.4% to 36% could be achieved, when the relief chamfer angle is set around 30°. Comparisons between the relief chamfer method and the time delay method indicate that the former has better compatibility to the load pressure lower than the rated value; while the latter has better compatibility to the higher load pressure.

Energy analysis of a real suction-pressure unit

Abstract The article presents an energy analysis of a real suction-pressure unit of a high-efficiency radial piston pump. This pump can be used in small hydropower plants, where, together with a variable displacement hydraulic motor, it would form a hydrostatic transmission. The main advantage of this solution is the possibility of a stepless, automatic change of gear ratio during its operation, which allows an increase of the efficiency of power generation in a hydropower plant. Mathematical models of friction and resistance of flow through self-acting and geometrical deformations of chambers and piston under stress field are presented. In addition, mass, volume, and energy balance calculations were computed for the ideal unit and pressure losses were determined. Derived indicator diagrams for each chamber of the ideal suction-pressure unit served to analyze the technical work of occurring processes. The paper also presents the formulation of total efficiency of the unit. Lastly, the experimental procedure is presented, according to which it is possible to register the most important parameters of the proposed model.

Change in Oil Pressure in Piston Chamber of a Radial Piston Pump Pre-compression Area When Considering the Compressibility of Oil

Change in Oil Pressure in Piston Chamber of a Radial Piston Pump Pre-compression Area When Considering the Compressibility of Oil

Tribological study of piston–cylinder interface of radial piston pump in high-pressure common rail system considering surface topography effect

Based on the theory of thermal fluid dynamic lubrication, the Reynolds equation and energy equation of the average flow of a piston–cylinder interface of a radial piston pump in a high-pressure common rail system are established, considering the surface topography effect. The tribological properties of the piston–cylinder interface are calculated by solving the Reynolds equation and energy equation. A surface wear model is established and the wear distribution and trend of the piston–cylinder interface are studied. The wear characteristics of the piston–cylinder interface are verified through experiment, and the wear lubrication of the piston–cylinder interface is discussed. The surface topography effect has a considerable influence on the characteristics of the piston–cylinder interface film. Different surface morphologies change the film characteristics of the piston–cylinder interface, yielding different wear behaviors on the mating surface. The wear of the piston–cylinder interface first decreases along the film outlet to the inlet and then rises. The cylinder surface mainly exhibits abrasive, cavitation, and micro-convex scratch wear, whereas the piston surface mainly shows cavitation wear. The results obtained in this study are of considerable significance as they reveal the tribological properties of the piston–cylinder interface under the surface topography effect.

Double-rotator and valve plate distribution radial piston pump

PurposeThe drive shaft and the distribution shaft of a traditional radial piston pump are in a cantilever state. To solve this problem, this paper aims to present a radial piston pump with through shaft driving and valve plate distribution.Design/methodology/approachThe working principle of the pump is discussed in detail. In this radial piston pump, valve plate distribution parts are designed to distribute oil to the piston chambers, and the distribution shaft is replaced. A bearing is installed between the stator and rotator to reduce the friction. The transmission shaft is supported by two bearings to ensure smooth operation. The support force of the transmission shaft is optimized. In addition, the flow pulsation principle is presented. To accomplish the change, the displacement of the radial piston pump, the proportional control system is designed.FindingsAfter completing the machining and assembly of the pump, an experimental study was carried out. The results show that the output flow of the pump is basically the same as the theoretical flow.Originality/valueThe friction between the slipping shoes and the stator is greatly reduced due to the function of rolling bearings. The higher stability of the driveshaft is obtained for the reason of double-sided support. The radial piston pump has a novel structural design in reducing the friction between the shoes and the stator and improving the stability of the transmission shaft.

Design and analysis of an axial flux permanent magnet motor for the direct drive radial piston pump

Direct drive motor-pumps have attracted a lot of attention from researchers because of high efficiency and compact structure. This paper presents a new type of direct drive motor-pump, which integrates the structure of the radial piston pump and axial-flux permanent-magnet machine. The rotor of the disc motor is fixedly connected to the pump rotor, and the new pump uses a new type of distribution shaft for oil distribution. This structure reduces the intermediate transmission mechanism, and the application of the disc motor further reduces the axial size, the overall volume, and heat dissipation. The efficiency of the entire system has been improved. The three-dimensional finite element method is used to dynamically analyze flow field in the flow channel, which is extracted and simplified. The flow and pressure of the pump meet the design requirements in the simulation. A disc motor was designed for the pump, and the theoretical formula of the disc motor was derived. The initial size of the motor was obtained. The response surface method and three-dimensional finite element are used to optimize the corresponding axial-flux permanent-magnet machine. Loading the torque condition of the pump to the load end of the motor, the response of the motor meets the requirements.