Balanced Vane Pump Research Articles

Effects of bubble content on the rotor behavior and characteristics of hydraulic pumps used for automatic transmissions

In automatic transmissions, hydraulic oil in the oil sump is strongly agitated by gears during operation; thus, the oil is mixed with great amounts of air. Air-mixed oil is sucked and discharged by a hydraulic pump to shift the gears. Although air bubbles mixed in the oil may affect the behavior of the rotors, driving torque, and discharge flow rate, they have hardly been measured. In this study, we measure them using a balanced vane pump and a gerotor pump used for automatic transmissions under varying air bubble contents and operating conditions. The experimental results revealed that the inclusion of air bubbles in the oil somewhat influenced the rotor behavior of both test pumps but it did not seem to increase the contact between the rotor and the surrounding stationary parts. Furthermore, as the bubble content increased, friction torque decreased to some degree, while discharge flow rate decreased to a great degree. This work proposed a new friction torque model, in which bubble content is included as a parameter, and the proposed model demonstrated relatively good agreement with the measured friction torque characteristics. The results also revealed that the rotor behavior and friction torque characteristic were mainly affected by bubble content and less so by bubble size.

Modeling and experimental validation of twin lip balanced vane pump considering micromotions, contact mechanics, and lubricating interfaces

This paper presents a model formulation for balanced twin lip vane pumps and an experimental activity to validate the model. The simulation model begins with a geometrical module that preprocesses the CAD drawings of a given unit. The model then performs a fluid dynamic analysis using a lumped-parameter formulation to solve for the pressures inside properly defined control volumes within the unit. The fluid dynamic model is solved simultaneously with a motion module that evaluates the planar motions of the vanes using Newton’s law of motion and with a lubricating interface solver based on the Reynolds equation. Contact dynamics formulations and elastohydrodynamic relations are applied at the vane locations in contact with the cam ring. The comparison with experimental results highlights a good match in volumetric and hydromechanical efficiencies. The measured outlet pressure ripple matches the simulated one for all tested speeds and pressures. The paper also shows a breakdown of the distribution of volumetric and power losses arising from various components of the machine. The proposed methodology is computationally inexpensive, so it can be used in future design and optimization studies aimed at improving the performance of such units.

Computational Fluid Dynamics Modeling of Gaseous Cavitation in Lubricating Vane Pumps: On Metering Grooves for Pressure Ripple Optimization

Abstract This paper addresses the topic of balanced vane pump simulations for pressure ripple optimization by means of metering grooves at the leading edge of delivery ports. It presents a computational fluid dynamics case study based on a transient three-dimensional model developed using an up-to-date commercial software tool. Special attention is dedicated to gaseous cavitation and the impact of the related modeling choices on predictions. The effect of groove dimensions and interaction with the precompression features of the cam ring of the pump are addressed. Experimental data obtained using a dedicated test rig are presented for comparison with numerical results in terms of delivery pressure ripple and volumetric flowrate. A validation strategy based on tuning of the dynamic cavitation model adopted for simulations is proposed. The results demonstrate the critical importance of gas release modeling for the simulation of porting details in the case of significant aeration effects.

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.

Experimental Investigation of a Double-Acting Vane Pump with Integrated Electric Drive

The article presents an innovative design solution of a balanced vane pump integrated with an electric motor that has been developed by the authors. The designed and constructed bench, which enables testing of the system: power supply, converter, ntegrated motor—pump assembly and hydraulic load at different motor speeds and different pressures in the hydraulic system, is described. The electromagnetic and hydraulic processes in the motor-pump unit are investigated, and new, previously unpublished, results of experimental studies at steady and dynamic states are presented. The results of the study showed good dynamics of the integrated motor-pump assembly and proved its suitability to control the pump flow rate, and thus, the speed of the hydraulic cylinder or the speed of the hydraulic motor.

A CFD-Based Comparison of Different Positive Displacement Pumps for Application in Future Automatic Transmission Systems

The efficiency requirements for hydraulic pumps applied in automatic transmissions in future generations of automobiles will increase continuously. In addition, the pumps must be able to cope with multiphase flows to a certain extent. Given this background, a balanced vane pump (BVP), an internal gear pump (IGP) and a three-dimensional geared tumbling multi chamber (TMC) pump are analyzed and compared by a computational fluid dynamics (CFD) approach with ANSYS CFX and TwinMesh. Furthermore, test bench measurements are conducted to obtain experimental data to validate the numerical results. The obtained numerical results show a reasonable agreement with the experimental data. In the first CFD setup, the conveying characteristics of the pumps with pure oil regarding volumetric efficiencies, cavitation onset and pressure ripple are compared. Both the IGP and the BVP show high volumetric efficiencies and low pressure ripples whereas the TMC shows a weaker performance regarding these objectives. In the second CFD setup, an oil-bubbly air multiphase flow with different inlet volume fractions (IGVF) is investigated. It can be shown that free air changes the pumping characteristics significantly by increasing pressure and mass flow ripple and diminishing the volumetric efficiency as well as the required driving torque. The compression ratios of the pumps appear to be an important parameter that determines how the multiphase flow is handled regarding pressure and mass flow ripple. Overall, the BVP and the IGP show both a similar strong performance with and without free air. In the current development state, the TMC pump shows an inferior performance because of its lower compression ratio and therefore needs further optimization.

A CFD Investigation of a 2D Balanced Vane Pump Focusing on Leakage Flows and Multiphase Flow Characteristics

Vane pumps are often applied in automatic transmission systems of vehicles. Future applications require the oil pumps to be more efficient and to be able to handle multiphase flow pumping situations to a certain extend. To fulfill these requirements, efficient development tools are needed. Therefore, a less demanding computational 2D model of a fixed-type balanced vane pump was derived and numerically analyzed with the commercial computational fluid dynamics (CFD) software ANSYS CFX. The meshing of the rotating parts was done with TwinMesh, using a moving mesh approach. At first, a mesh convergence study was performed. It was shown that the resolution of the radial clearances in particular had a significant influence on the predicted leakages and the volumetric efficiency. The leakage was further investigated concerning the dependence on rotational speed and delivery pressure. In the next step, multiphase flows were considered. In a first setup, vapor cavitation was analyzed and the influence of the alignment of the suction ports on its onset was derived. In a second setup, the influence of different inlet volume fractions of free air was evaluated. The employed multiphase modeling approach was presented and a sensitivity analysis on modeling parameters was performed. Overall, it was shown that free air in the suction ports changed the pumping characteristic of the vane pump significantly. Pressure and flow ripple increased, and the volumetric efficiency and the mean power demand decreased significantly with an increasing inlet volume fraction.

Computational Fluid Dynamics Modeling of Gaseous Cavitation in Lubricating Vane Pumps: An Approach Based on Dimensional Analysis

Abstract This paper addresses the problem of computational fluid dynamics (CFD) modeling of gaseous cavitation (GC) in lubricating positive-displacement pumps (PDPs). It is important for designers and analysts to predict the dynamic features of air release/dissolution processes which characterize this phenomenon, along with their effects on filling capability and noise-vibration-harshness behavior of the machine. The focus is on the empirical tuning of the commercial homogeneous-flow cavitation model known as dissolved gas model (DGM). Considering an automotive case study of a balanced vane pump (BVP), the effects of air modeling on numerical predictions of discharge flow/pressure ripple and volumetric efficiency have been studied. The tuning time parameters of the model have been correlated to the machine Reynolds number as part of a simplified theoretical background based on dimensional analysis. Considering experimental data at different operating conditions, the tuned model has shown a good capacity in predicting the pressure ripple and the flowrate at the discharge of the pump.

Steady-state Characteristics Study of a Power Split Hydraulic Transmission

The steady-state characteristics of a power split hydraulic transmission were carefully studied in this article. The hydraulic transmission is an alternative power split device for power split hydraulic hybrid drivetrain. It was built from a balanced vane pump, where an output shaft is added and coupled to its floating ring. The internal friction torques due to the relative motion between floating ring and vanes help to drive the output shaft. This improves the mechanical transfer efficiency from input to output shaft, making it more competitive than conventional hydrostatic transmission. The steady-state characteristics of the hydraulic transmission were investigated through both theoretical analysis and experimental studies. Mathematical models of the input and output shaft torques, and the outlet flow rate of the hydraulic transmission were developed. Studies show that the input and output shaft torques are not only dependent on outlet pressure, but also dependent on differential shaft speed. The outlet flow rate is proportional to the differential shaft speed. Finally, a hydro-mechanical transmission based on power split hydraulic transmission was introduced. The characteristics and system application of the hydro-mechanical transmission were given.

Kinematics of a balanced vane pump with circular tip vanes

This paper analyzes the kinematics of the vane-cam ring mechanism in balanced vane pumps, by considering both vanes with centered and not-centered circular tip. The motion of the vane, the position of the contact point and the evolution of the pressure angle are analytically determined in reference to a generic cam ring profile. The results of the kinematic analysis are used to obtain the constraints defining the admissibility of the vane geometry, which is described in terms of tip radius, vane thickness and tip center eccentricity. A parametric study is performed to show the capabilities of the proposed formulation and the influence of the vane design parameters on its kinematics. The analysis demonstrates that the vane kinematic motion in balanced vane pumps is mainly controlled by the tip radius and the tip center eccentricity, as long as the cam ring profile is defined. The tip radius is mainly responsible for the shape of the vane motion, while the tip center eccentricity has a major influence on its timing. Furthermore the effect of the cam ring profile is evaluated by demonstrating that shape and extension of the rise and fall phases influence on the vane geometry admissibility.

A study on flow control valve characteristics in an oil hydraulic vane pump for power steering systems

In the power steering system of an automobile, the balanced and fixed displacement type vane pump is principally applied to the main power source. It is driven by a pulley that is attached to the shaft of the vehicle's engine, and the pulley ratio is about 1:1. The vane pump continuously discharges an outlet flow rate proportional to the rotating speed of the engine. In a vane pump without the flow control valve, an increase in the discharge flow rate means a linear increase in the actuator speed. At high speed when the driver rotates the steering wheel by even a small amount, there is a high risk of an accident due to the quick rotation of the tire joined to the actuator and links. We designed a flow control valve of the fixed displacement and pressure balanced type vane pump for power steering is designed and simulated using AMESim software. Its theoretical flow characteristics with respect to the rotating speed of the engine are compared and validated with experimental data. The results show that the design parameters, such as the flow area, the underlap length, the spool clearance, the main spring stiffness and the spring initial force, largely affect the flow control characteristics.

Friction Characteristics of Vane for a Balanced Vane Pump

Friction Characteristics of Vane for a Balanced Vane Pump

Influence of leakage flow variation on delivery pressure ripple in a vane pump

This article describes the theoretical analysis and experimental verification of the influence of variations of leakage flow as well as ideal flow on delivery pressure ripple in a balanced vane pump. The analytical model for simulating the delivery pressure ripple of the pump is simplified. It is composed of only the ripple of the ideal flow based on the theoretical pump displacement determined from geometrical pump dimensions, the leakage flow variation dependent on the pump dimensions including clearances and pump-operating conditions, an oil chamber volume in the pump and the impedance of a hydraulic circuit with a throttle valve set close to a pump outlet. The purpose of this study is to predict the pump delivery pressure ripple at the design stage of the vane pump. This article reveals that the delivery pressure ripple can be theoretically predicted through the calculations of the leakage flow as well as the ideal flow. The waveform of the delivery pressure ripple calculated agrees well with the measured one. The leakage flow variation significantly affects the delivery pressure ripple and it can be also calculated accurately from the pump dimensions including the clearances and pump-operating conditions. In addition, the components of the leakage flow are clarified and their effects on the delivery pressure ripple are investigated.

Studies on several key problems of water hydraulic vane pump

PurposeThe balanced vane pump is a common transmission component in hydraulic systems. Since the physicochemical properties of water and seawater are different from that of mineral oil, some problems can occur, for instance, poor lubrication, more leakage, and more corrosion. The paper aims to demonstrate the technical feasibility for the water hydraulic vane pump.Design/methodology/approachThe material combinations were selected based on related research in literature. The volumetric efficiency and suction performance were measured in the current experiment. The relations between gap clearances and leakage flow, the contact and the friction forces between a vane tip and a cam contour were simulated based on mathematic models.FindingsThe soft‐hard material combinations in the prototype pump show preferable friction characteristics during tests. The axial clearances are the main channels of leakage flow. Pin type vane pump can reduce the contact force of the vane tip.Originality/valueThis paper outlines some key problems of the water hydraulic vane pump, such as the friction pair material,the structure, and the contact force of the vane tip by means of testing the basic performance of pump and mathematic model.

Reduction of friction torque in vane pump by smoothing cam ring surface

This work deals with the influence of surface roughness of cam contours on friction torque in a hydraulic balanced vane pump and it is verified that smoothing the surface of the cam contour can reduce friction torque. In the vane pump, the friction torque arising from the friction between a cam contour and vane tips is significant. In this article, first, the values of the coefficient of friction between the vane tip and its sliding surfaces were measured by using cylindrical test rings with various kinds of surface roughness. Then the torque characteristics of vane pumps having cam ring contours with various values of surface roughness were measured and their results compared with the results of an analysis of the coefficient of friction investigated using test rings. As a result, the friction torque caused by the friction between the cam contour and the vane tip was reduced by lessening the surface roughness of the cam contour, resulting in an improvement of the mechanical efficiency. The coefficient of friction measured by using the test rings could be applied to the actual vane pumps.

Vane Pump Theory for Mechanical Efficiency

This paper describes the theoretical analysis on the mechanical efficiency of a hydraulic-balanced vane pump and presents a design concept to decide values such as vane thickness and cam lift to improve its mechanical efficiency. In this paper, the friction torque characteristics of the balanced vane pump, especially the friction torque caused by the friction between a cam contour and vane tips are both experimentally and theoretically investigated. Although the friction force increases with vane thickness increase due to increase in the vane force, the mechanical efficiency of the vane pump does not decrease when the cam lift becomes large as the vane thickness is increased. An important parameter ∊ defined as the ratio to be obtained by dividing the cam lift by the vane thickness determines essentially the mechanical efficiency of the vane pump. The pumps with the same ∊ have the same mechanical efficiencies, even if the cam lift or the vane thickness varies. A larger value of ∊ leads the vane pump to obtain a higher mechanical efficiency although the limit of vane strength governs the upper limit for ∊. Additionally, reducing the friction coefficient of the vane tip contributes to improvement of the mechanical efficiency.

カムリングの変形を考慮したベーンポンプの内部圧力シミュレーション

This paper deals with noise reduction of a balanced vane pump which is used in power steering system based on a simulation technique.To ensure passenger car riding comfort, it is important to reduce the noise and vibration levels of the hydraulic pumps used in them. From the viewpoint of car energy consumption, a weight reduction of automobile parts and components is becoming an important issue. The weight reduction, however, leads to an insufficiency in stiffness of the parts and components and may cause a lessening of the dynamic characteristics of those parts and components.To develop a quiet hydraulic pump as an automobile part, the internal pressure fluctuation must be reduced. To solve this problem, simulation techniques are usually needed. Conventional simulation techniques, however, do not take into account the effect of the stiffness of the parts and components, and accordingly, the simulation results are not accurate enough.In this study, the effect of the cam deformation on the internal pressure of a vane pump has been investigated both theoretically and experimentally.The advanced simulation technique to predict internal pressure was developed, taking in consideration cam deformation, and noise reduction of 2-4dB could be achieved through the design application of this technique.

Power steering pump energy savings

This paper deals with energy-savings in hydraulic power steering systems, especially regarding the reduction of the driving torque of an engine-driven pump in non-steering operation. For power steering, a balanced vane pump having two displacement processes per revolution is commonly used. Now, by unloading one of the displacement processes with a communication link between the delivery and suction ports during non-steering operation, the theoretical pumping work reduces to half that of a conventional pump. Therefore, the driving torque decreases to nearly one-half. As a result, the driving torque of the pump with this mechanism decreases to about 60% of that of a conventional pump at 0.5 MPa and 1500 rpm.

Pressure Ripples of a Balanced Vane Pump.

This paper describes an experimental and theoretical investigation of the delivery pressure ripples of a balanced vane pump which is commonly used for automobile power steering (PS) hydraulic systems. A linearized model which includes torsional vibration of the pump drive shaft is proposed. The backflow into the pumping chamber resulting from fluid compressibility is not taken into consideration in the mathematical model because the delivery pressure of PS hydraulic systems is relatively low. It is found that the delivery pressure ripple levels of the test pump become lower with decreasing speed and increasing delivery pressure. The theoretical calculation shows that it derives from the fact that the phase of the pressure ripple waveform caused by the leakage flow variation lags behind that caused by the theoretical flow variation by about 180 degrees. Torsional vibration of the drive shaft has influence on the pressure ripple levels.

Characteristics of Fluidborne Noise Generated by Fluid Power Pump : 2nd Report, Pressure Pulsation in Balanced Vane Pump

This paper presents a discharge pulsating pressure (fluidborne noise) generated by a balanced vane pump. It is pointed out first that the pressure pulsation in vane pump includes three types of pressure oscillations, namely, the well known pressure ripple with a fundamental component at vane frequency together with harmonics, the low-frequency pressure oscillation with a fundamental component at rotational frequency of rotor together with harmonics, and the transient high-frequency pressure oscillation occurring with a period of vane frequency. In regard to the pressure ripple, it is pointed out that the experimental values can be explained well, up to about 8th harmonic of it, by the calculated values based on the present mathematical models for flow ripple considering fluid compressibility and pump source impedance. It can be said also that the above-mentioned low-frequency pressure oscillation is caused by the fluctuation in pump leakage flow depending on the rotational position of the pump, and that the transient high-frequency pressure oscillation is caused by the resonance of oil column in the pump discharge chamber including a port adapter.