Gear pumps are frequently used for the transport of high‐viscosity fluids, for instance, for the extrusion of polymers. The flow rate of this extrusion process is regularly controlled by an external ...gear pump. In this work, the 2D flow of a viscous fluid through such an external gear pump is studied using the finite element method. Local mesh refinement based on the respective distance between moving boundaries is essential to capture the relatively narrow clearances in the pump. The gear pump works against the pressure driven flow, therefore its performance is strongly dependent on material and processing parameters. The flow of Newtonian and shear‐thinning fluids through the external gear pump is studied for a range of processing conditions. Pump curves are obtained that display the volumetric efficiency against the Hersey number, which is defined as viscosity times rotation speed divided by pressure difference over the pump. Analysis of the residence time of the fluid in the pump, shows that vortices are present in the inflow channel causing material to remain in the pump for longer times.
External gear pumps are used in various production systems to transport fluids. A numerical study using the finite element method shows that the efficiency of these pumps depends on material and processing parameters. The pump curve displays at which conditions the efficiency of the pump drops as a result of backflow of the fluid through the pump clearances.
This paper wants to investigate the effects of eco-friendly fluids on the thermo-fluid-dynamic performance of external gear pumps in order to provide a first response to the increasingly urgent ...demands of the green economy. A computational fluid dynamics (CFD) approach based on the overset mesh technique was developed for the simulation of the full 3D geometry of an industrial pump, including all the characteristic leakages between components. A sensibility analysis of the numerical model with respect to different fluid properties was performed on a commonly used mineral oil, showing the key role of the fluid compressibility on the prediction of the pump volumetric efficiency. Moreover, the influence of temperature internal variations on both fluid density and viscosity were included. The BIOHYDRAN TMP 46 eco-friendly industrial oil and olive oil were further considered in this work, and the results of the simulations were compared for the three fluid configurations. A slightly lower volumetric efficiency was derived for the olive oil application against the other two conditions, but suggestive improvements were produced in terms of pressure and temperature distributions. Therefore, based on the obtained results, this paper encourages research activity towards the use of eco-friendly fluids in the hydraulic field.
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.
This work concerns external gear pumps for automotive applications, which operate at high speed and low pressure. In previous works of the authors (Part I and II, 1,2), a non-linear lumped-parameter ...kineto-elastodynamic model for the prediction of the dynamic behaviour of external gear pumps was presented. It takes into account the most important phenomena involved in the operation of this kind of machine. The two main sources of noise and vibration are considered: pressure pulsation and gear meshing. The model has been used in order to foresee the influence of working conditions and design modifications on vibration generation. The model experimental validation is a difficult task. Thus, Part III proposes a novel methodology for the validation carried out by the comparison of simulations and experimental results concerning forces and moments: it deals with the external and inertial components acting on the gears, estimated by the model, and the reactions and inertial components on the pump casing and the test plate, obtained by measurements. The validation is carried out by comparing the level of the time synchronous average in the time domain and the waterfall maps in the frequency domain, with particular attention to identify system resonances. The validation results are satisfactory global, but discrepancies are still present. Moreover, the assessed model has been properly modified for the application to a new virtual pump prototype with helical gears in order to foresee gear accelerations and dynamic forces. Part IV is focused on improvements in the modelling and analysis of the phenomena bound to the pressure distribution around the gears in order to achieve results closer to the measured values. As a matter of fact, the simulation results have shown that a variable meshing stiffness has a notable contribution on the dynamic behaviour of the pump but this is not as important as the pressure phenomena. As a consequence, the original model was modified with the aim at improving the calculation of pressure forces and torques. The improved pressure formulation includes several phenomena not considered in the previous one, such as the variable pressure evolution at input and output ports, as well as an accurate description of the trapped volume and its connections with high and low pressure chambers. The importance of these improvements are highlighted by comparison with experimental results, showing satisfactory matching.
•A formulation for pressure phenomena in gear pump dynamics is proposed.•The trapped volume and its connections are accurately accounted for.•The model is a nonlinear lumped-parameter kineto-elastodynamic gear pump model.•The pressure ripple can be accurately estimated.•The model can accurately predict gear accelerations and forces/moments.
Abstract
Linear conjugate internal gear pump has low noise and a smooth flow, but the mechanism of flow pulsation, especially the experiment, is seldom studied. In this paper, the flow rate formula ...of instantaneous, flow pulsation rate and relative volume change of the trapped oil cavity are derived by means of theoretical calculation. The pressure fluctuation characteristics of the trapped oil chamber and flow pulsation characteristics of the pump outlet are studied by using the three-dimensional fluid dynamics finite element simulation analysis method. According to the international standard of ISO10767-1-2015, the pump outlet flow pulsation test was conducted. The flow pulsation rate of a certain type of linear conjugate internal gear pump with a displacement of 10mL/r is about 6.35% under the condition of the speed of 750r/min and outlet pressure of 7.5MPa, and the flow pulsation is small.
Abstract Aiming at the limitations of the existing hydraulic pumps, a new type of bidirectional water-hydraulic internal ball gear pump using concave-convex ball teeth meshing to transfer power is ...proposed. In this paper, the principle of internal gear pump is utilized to establish the model of internal ball gear pump, and its mechanical properties and dynamic meshing characteristics are numerically investigated by using the finite element method. The results show that (a) the concave-convex ball gears run smoothly without any interference, and (b) increasing the number of gear rows can effectively reduce the maximum stress and meshing impact under a given load and speed. This study provides a basis for the development of high-performance ball gear pumps.
Voluntary rehabilitation at home helps to prevent the joint contracture after medical treatment. Our previous studies concerned a low-cost portable rehabilitation device using a flexible spherical ...pneumatic actuator as a passive exercise device. However, the device requires a bulky compressor to drive it. This study results in a compact fluidic driving system that is highly flexible. The system adopts a flexible electro-hydraulic cylinder driven by an electric motor and a hydraulic gear pump. An empirical equation for the suitable pump rotation for the desired displacement of the system has been determined. As a result, the multi-position control of the system within the tracking error of 4 mm has been realized by using the on/off control scheme based on the obtained equation. In addition, a flexible, spherical electro-hydraulic actuator using two proposed drive systems is developed and tested. Control of the attitude of the tested spherical actuator is successfully realized.
The surrogate model based on Kriging has been widely used to approximate simulation problems of expensive computing. Although the accuracy of the gradient enhanced Kriging (GEK) is often higher than ...that of ordinary Kriging, designers cannot avoid more time consuming during gradient calculation of GEK. To this end, a sequential gradient-enhanced-Kriging optimal experimental design method with the Gaussian correlation function (GCF) is investigated to approximate complex black-box simulation problems by introducing gradient information of Kriging parameters. Due to the differentiable GCF, the gradient information can be simply evaluated. This characteristic make the proposed method effectively improve the modeling accuracy and efficiency of GEK. As expected, the test results from benchmark functions and the cycloid gear pump simulation show the feasibility, stability and applicability of the proposed method.
Abstract
In order to solve the problems in the structural design of the gear pump in use, three dimensional modeling software is used to complete the parts modeling of gear pump one by one, it is ...assembled as a gear pump, and the structure of gear pump is optimized by auxiliary design, further improve the performance of gear pump, Computer aided modeling design can effectively improve the design efficiency, Optimize the structure performance, reduce the design cost and improve the economic benefit.
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