Showing papers on "Gear pump published in 2017"

Models for Flow Rate Simulation in Gear Pumps: A Review

Abstract: Gear pumps represent the majority of the fixed displacement machines used for flow generation in fluid power systems. In this context, the paper presents a review of the different methodologies used in the last years for the simulation of the flow rates generated by gerotor, external gear and crescent pumps. As far as the lumped parameter models are concerned, different ways of selecting the control volumes into which the pump is split are analyzed and the main governing equations are presented. The principles and the applications of distributed models from 1D to 3D are reported. A specific section is dedicated to the methods for the evaluation of the necessary geometric quantities: analytic, numerical and Computer-Aided Design (CAD)-based. The more recent studies taking into account the influence on leakages of the interactions between the fluid and the mechanical parts are explained. Finally the models for the simulation of the fluid aeration are described. The review brings to evidence the increasing effort for improving the simulation models used for the design and the optimization of the gear machines.

Study of a High-Pressure External Gear Pump with a Computational Fluid Dynamic Modeling Approach

Abstract: A study on the internal fluid dynamic of a high-pressure external gear pump is described in this paper. The pump has been analyzed with both numerical and experimental techniques. Starting from a geometry of the pump, a three-dimensional computational fluid dynamics (CFD) model has been built up using the commercial code PumpLinx®. All leakages have been taken into account in order to estimate the volumetric efficiency of the pump. Then the pump has been tested on a test bench of Casappa S.p.A. Model results like the volumetric efficiency, absorbed torque, and outlet pressure ripple have been compared with the experimental data. The model has demonstrated the ability to predict with good accuracy the performance of the real pump. The CFD model has been also used to evaluate the effect on the pump performance of clearances in the meshing area. With the validated model the pressure inside the chambers of both driving and driven gears have been studied underlining cavitation in meshing fluid volume of the pump. For this reason, the model has been implemented in order to predict the cavitation phenomena. The analysis has allowed the detection of cavitating areas, especially at high rotation speeds and delivery pressure. Isosurfaces of the fluid volume have been colored as a function of the total gas fraction to underline where the cavitation occurs.

Numerical simulation of Gerotor pumps considering rotor micro-motions

Abstract: Gerotor units are widely used in low-pressure (up to 30 bar) fluid power applications, injection as well as lubrication systems, due to their compact package and low cost. Their performance in terms of volumetric efficiency, flow pulsations, internal pressure peaks or localized cavitation depends on many parameters, such as the rotors’ profiles and the manufacturing tolerances. This paper proposes a multi-domain simulation approach for the numerical analysis of the performance of Gerotor units. Characterized by simulation swiftness, the model can be used for virtual prototyping of units considering the actual geometry of the rotors, their geometrical tolerances and the properties of the working fluid. The approach is based on the coupling of different models: a numerical geometric model evaluates the instantaneous volumes and flow areas inside the unit; a lumped parameter fluid dynamic model describes the displacing process of the tooth space volumes; finally, a mechanical model evaluates the internal micro-motions of the rotors axes according to their tolerances. In this way, the model determines the actual loading of the rotors, considering also the actual location of the points of contact. After presenting the approach, the paper describes the potentials of the proposed method with reference to a particular Gerotor pump design. Specific experiments were performed within this research to permit a detailed model validation, and comparisons in terms of significant steady-state as well as transient pressure and flow features are presented. The approach used in the current paper can be considered valuable when studying the impact of real-life technological clearances on the fluid-dynamic performance of the pump.

Mixed Lubrication Effects in the Lateral Lubricating Interfaces of External Gear Machines: Modelling and Experimental Validation

Abstract: This article presents a novel mixed-thermoelastohydrodynamic (TEHD) model for the lateral lubricating interfaces which exist between floating lateral bushings and gears in external gear machines (EGMs). The proposed model integrates the influence of surface asperities along with the fluid structure and thermal interaction in the interface, especially in the regions of very low film thicknesses by following a stochastic approach in modelling the mixed lubrication regime. Furthermore, the current work includes validation of the predictions of the mixed-TEHD model against experimentally measured leakages from the lateral gap and compares the performance of this model with a previously developed full film TEHD model for the lateral gaps in EGMs.

Modeling Noise Sources and Propagation in External Gear Pumps

Abstract: As a key component in power transfer, positive displacement machines often represent the major source of noise in hydraulic systems. Thus, investigation into the sources of noise and discovering strategies to reduce noise is a key part of improving the performance of current hydraulic systems, as well as applying fluid power systems to a wider range of applications. The present work aims at developing modeling techniques on the topic of noise generation caused by external gear pumps for high pressure applications, which can be useful and effective in investigating the interaction between noise sources and radiated noise and establishing the design guide for a quiet pump. In particular, this study classifies the internal noise sources into four types of effective load functions and, in the proposed model, these load functions are applied to the corresponding areas of the pump case in a realistic way. Vibration and sound radiation can then be predicted using a combined finite element and boundary element vibro-acoustic model. The radiated sound power and sound pressure for the different operating conditions are presented as the main outcomes of the acoustic model. The noise prediction was validated through comparison with the experimentally measured sound power levels.

Magnet-Sleeve-Sealed Mini Trochoidal-Gear Pump Prototype with Polymer Composite Gear

Abstract: The trochoidal-gear technology has been growing in groundbreaking fields. Forthcoming applications are demanding to this technology a step forward in the conceiving stage of positive displacement machines. The compendium of the qualities and the inherent characteristics of trochoidal-gear technology, especially towards the gerotor pump, together with scale/size factor and magnetic-driven transmission has led to the idea of a magnet-sleeve-sealed variable flow mini trochoidal-gear pump. From its original concept, to the last phase of the design development, the proof of concept, this new product will intend to overcome problems such as noise, vibration, maintenance, materials, and dimensions. The paper aims to show the technological path followed from the concept, design, and model, to the manufacture of the first prototype, where the theoretical and numerical approaches are not always directly reflected in the prototype performance results. Early in the design process, from a standard-commercial sintered metal mini trochoidal-gear unit, fundamental characteristics and dimensional limitations have been evaluated becoming the strategic parameters that led to its configuration. The main technical challenge to confront is being sealed with non-exterior driveshaft, ensuring that the whole interior is filled and wetted with working fluid and helping the hydrodynamic film formation, the pumping effect, and the heat dissipation. Subsequently, the mini pump architecture, embodiment, methodology, materials, and manufacture are presented. The trend of applications of polymer composite materials and their benefits wanted to be examined with this new mini pump prototype, and a pure polyoxymethylene mini trochoidal-gear set has been designed and manufactured. Finally, both the sintered and the polymer trochoidal-gear units have been experimentally tested in an in-house full-instrumented mini test bench. Although the main goal of the presented work is the development of a new mini trochoidal-gear pump prototype rather than a numerical study, the results have been compared with numerical simulation. Subsequently, the prototype of the mini trochoidal-gear pump is a feasible proof of concept supported by functional indexes and the experimental results.

The influence of gear micropump body asymmetry on stress distribution

Abstract: The paper presents the results of numerical calculations of stress distributions in the gear micropump body for applications in hydraulic systems, especially in the marine sector. The scope of the study was to determine the most favorable position of bushings and pumping unit in the gear pump body in terms of stress and displacement distribution in the pump housing. Fourteen cases of gear pump bushings and pumping unit locations were analyzed: starting from the symmetrical position relative to the central axis of the pump, up to a position shifted by 2.6 mm towards the suction channel of the pump. The analysis of the obtained calculation results has shown that the most favorable conditions for pump operation are met when the bushings are shifted by 2.2 mm towards the suction channel. In this case the maximal stress was equal to 109 MPa, while the highest displacement was about 15μm. Strength and stiffness criteria in the modernized pump body were satisfied.

Improvement of Lubrication Performance in External Gear Machines through Micro-surface Wedged Gears

Abstract: This article demonstrates how a properly designed micro-surface linear wedge added to the lateral surfaces of the gear teeth can improve the lubricating ability of external gear machines (EGMs), resulting in lower power losses and chance of wear during their operation. The approach of study is based on the use of a fluid structure interaction (FSI) model for the analysis of the lateral lubricating gaps developed in the authors' research team. Such a model is used to determine the best design of the wedged gear by considering the overall axial balance problem of pressure compensated EGMs for high-pressure applications. The article shows the numerical predictions along with the experimental verifications of the advantages offered by the proposed solution in terms of torque loss reduction for a particular reference pump.

Two-speed transaxle for electric vehicle

Abstract: A two-speed transaxle for an electric vehicle has an input shaft receiving power from an electric motor, and two output shafts delivering power to drive the vehicle. At least one epicyclic gear set is used. Each epicylic gear set has only an outer gear member, each of which meshingly engage a plurality of planet gears supported on a common carrier. The two-speed transaxle produces its first forward speed ratio when a first caliper brake system and a second caliper brake system are disengaged and a one-way clutch connects the first sun gear to the transaxle casing. Second forward speed ratio results when the second hydraulic brake is engaged to fix the second sun gear. Reverse drive and regenerative operation result when the first hydraulic brake fixes the first sun gear and the direction of power flow is reversed.

Flow characteristics of accelerating pump in hydraulic-type wind power generation system under different wind speeds

Abstract: To investigate the characteristics of a cycloid gear pump which is used as the accelerating pump in the wind power, a flow mathematical model was built, the advanced modeling environment simulation (AMESim) hydraulic model of wind turbines was established, and the effectiveness of the model is verified by the experiments. Based on the AMESim model, the flow characteristics of the wind turbine under the steady and unsteady wind speeds were investigated. The results show that, at low steady speed, the pulsation rate of flow pulsation in the cycloid gear pump decreases with the increase of rotational speed; and the lower the rotating speed is, the less steady the cycloid gear pump runs. Under the unsteady wind speed, the variation trend of output flow of the cycloid gear pump is basically consistent with that of the wind speed; the fluctuation frequency of the flow is greater than that of the speed. Meanwhile, due to the flow fluctuation of the cycloid gear pump, the mechanical energy with sudden change can be converted into the soft hydraulic energy, which is more conducive to the wind power. The research also proves that the cycloid gear pump can be used as the accelerating pump in the wind power generation system.

The study of leakage of circular arc–involute–circular arc gear pump:

Abstract: In this article, the flow rate and leakage of circular arc–involute–circular arc gear pumps were investigated. Models of transverse and radial leakage patterns of the pump were also developed. The ...

Influence of setting the selected parameters of hydraulic systems on pressure pulsation of gear pumps

Abstract: The article presents results of preliminary experimental tests regarding pressure pulsation of the gear pump with external gear design, series PGP511 manufactured by Parker Hannifin. A cycle of measurements was carried out in relation to the selected parameters of system’s operation, such as: rotational speed of the pump shaft, pumping pressure and capacitance change (i.e. hydraulic capacity) of the pressure line. The obtained curves have been analyzed in terms of time and frequency.

Hydraulic type wave-energy power generation device

Abstract: The invention discloses a hydraulic type wave-energy power generation device. The hydraulic type wave-energy power generation device is mainly used for conducting power generation through ocean wave energy. The device is mainly composed of a push plate (1), pistons (2), springs (3), hydraulic cylinders (4), one-way valves (5), hydraulic gear pumps (6), transmission shafts (7), power generation units (8), an impounding reservoir (10), floating type flow guiding walls (11), funnels (14), special valves (15), retaining walls (16) and flow guiding slopes (20). According to the main working principle of the hydraulic type wave-energy power generation device, the push plate (1) is impacted by waves to move leftwards; the push plate (1) compresses the springs (3) and drives the pistons (2) to move leftwards; the pistons (2) push seawater in the hydraulic cylinders (4) to move leftwards and push the special valves (15) to be closed; the seawater moves leftwards and impacts the one-way valves (5) to be opened; the seawater in the hydraulic cylinders (4) enters the hydraulic gear pumps (6) through pipes; the seawater with pressure enters through water inlets (21) of the hydraulic gear pumps (6) and pushes each pair of gears (23) which are engaged with each other to rotate; furthermore, the gears (23) drive the transmission shafts (7) to rotate; and the transmission shafts (7) drive rotors of the power generation units (8) to rotate, so that the power generation units (8) are made to generate power.

Study on Flow Characteristic of Gear Pumps by Gear Tooth Shapes

Abstract: Oil pump models with different gear tooth shapes were established and the internal flow field simulation were conducted by utilizing Pumplinx. Then the characteristics of steady state flux and flow pulsation were analyzed. The research shows that: compared with straight gear pumps, the flow pulsation of other toothed gear pumps is much lower, although they have lower flow at low and medium speed. Especially the flow pulsation of dislocation gear pumps is much lower than straight gear pumps. It decreased by 27% at 1100 rpm and 35% at 2700 rpm, compared with straight gear pumps. Finally the straight gear pump flow is tested experimentally, and the experimental results match the simulation very well. This proves that the internal flow field models are correct and useful in technically supporting the oil pump development.

Reliability Evaluation of Key Hydraulic Components for Actuators of FAST Based on Small Sample Test

Abstract: The five-hundred meter aperture spherical radio telescope (FAST) is China’s major science and technology infrastructure project. Upon completion, this telescope will be considered the largest single-dish radio telescope in the world. As main active mechanism of FAST, 2225 hydraulic actuators are used for adjusting the reflectors. The reliability of hydraulic actuators is the most critical matter. This paper applies the reliability theory and reliability test method into large project for the first time. Firstly, a parallel energy-saving method and equipment to test the two components of the actuators for FAST are designed. Secondly, reliability model based on small sample test is used to perform the best linear unbiased estimation of the test data. Average impact lifetime of the sampled gear pump and the sampled relief valve in their working condition are calculated. Finally, the results show that the lifetime request of the sampled gear pump and the sampled relief valve for hydraulic actuator of FAST are satisfied. The research method has guiding significance to the reliability study of key hydraulic components for similar hydraulic systems.

A two-dimensional numerical analysis of a circular-arc gear pump operating at high pressures and high speeds

Abstract: This paper examines the flow field of a circular-arc gear pump operating at high pressures and high speeds by the commercial finite-volume-based code Fluent. The performance of circular-arc gear pump operating at high pressures and high speeds have been discussed. The mathematical model of the tooth profile is established. The pressures including gears mesh, outlet pressures, and outlet flow rate are studied under different rated outlet pressures and rotational speeds. There are dynamic pressures at clearance between chamber and tip circle of gear. Moreover, parts of radial leakages are prevented by dynamic pressures. The outlet pressures almost remain constant. However, there are strong pressure fluctuations in gears mesh under the high pressures and high speeds. The pressures are several times higher than the rated outlet pressure when the circular-arc gear pump operates at 10,000 r/min and 12,000 r/min. Gear meshing pressure fluctuations increase with the increase in rotational speeds. However, gear me...

Non-circular gear continuous generating machining interpolation method and experimental research

Abstract: Current non-circular gear manufacturing process all use discrete machining method, which generates a large number of small line segments, brings in approximate error, and leads to high-order discontinuity of the whole tool path curve. The tooth surface quality will be decreased significantly due to the vibration of machining tool caused by the discontinuity of machine tool motion trajectory especially in high-speed machining. In addition, the processing speed and efficiency will be limited due to the unsmooth kinematics profile. This paper proposes a non-circular gear completely continuous generating machining interpolation method. The non-circular gear machining electronic gearbox is developed to compute the real-time interpolation point data to guarantee the strict generating motion relationship between the workpiece spindle, feed shaft, and cutter spindle during the gear manufacturing process according to the derived linkage model for non-circular gear hobbing and generate continuous smooth machining trajectory. The proposed interpolation method is implemented on the self-developed CNC system based on the embedded CNC system hardware structure platform and verified experimentally on a gear hobbing machine. A pair of two-order oval non-circular gear is machined, and the roll and application experiments on a kind of gear pumps are done to illustrate the machining performance and provide a high efficiency and precision machining method for non-circular gear.

Analysis of Leakage Flow Through the Flank Contacts in Transition Zone in Involute External Toothed Gear Pump

Abstract: The leakage past the tooth flanks of the gears in transition contacts in involute external toothed gear pump is analyzed in details using CFD in Fluent®. Analytical results support the experimentally visualized flow patterns [1]. Extending the approach of an earlier investigation [2] more rigorous analyses are carried out considering actual gear data of a pump and a full cycle of contact. However, the relieve groove and cavitation are not considered. The basic purpose is to establish the flow pattern analyses using CFD in Fluent-Ansys® environment. The beginning and the end of entrapment, squeezing of fluid, pressure build up, separation and generation of gap at the active contact and instantaneous flow through the gap are estimated meticulously.Copyright © 2017 by ASME

Development of a micropump composed of three gears with Logix tooth profiles fabricated by micromilling technology

Abstract: Sustainability is a growing interest for industry to integrating and assessing social, environmental, and economic objectives. Involute gear and single-pump feed technology are difficult to satisfy the requirements of sustainability for high-homogeneous medium and low-loss situations. To improve the relative displacement and reduce the volume of the pump, an innovative three-gear micropump was designed. The gears were patterned with Logix tooth profiles which have lower undercutting tendency and are easy to design with a reduced number of teeth. The double-pump confluence technology was used to reduce the flow pulsation based on phase compensation. In this paper, the structural parameters of Logix gear were first calculated through mathematical analysis. Then, a micropump composed of three Logix gears was designed based on the selected parameters and double-pump confluence technology. The Logix gear was manufactured by micromilling experiments, and the three-gear pump was assembled. At last, a pressure fluctuation test platform was implemented to investigate the fluctuation of the three-gear pump and the transmission noise. Results showed that the displacement of the three-gear micropump was doubled compared with the conventional involute gear pump, with 50% flow pulsation reduction. The transmission noise of the Logix gear pump was also reduced. The outcome of this research will contribute to the development of simplified, safer and anti-fuel-burning gear pump systems, and environment-friendly and sustainable manufacturing of such systems.

Investigations of the micro surface shape for the gear-shaft/journal-bearing interface in water hydraulic internal gear pumps

Abstract: This article presents an approach for improving the water film’s carrying capacity in the gear-shaft/journal-bearing interface in water hydraulic internal gear pumps by applying micro shapes to the...