Helical Gear Pumps Research Articles

Retracted: Simulation of Flow-Induced Vibration and Dynamic Performance of Circular-Arc Helical Gear Pump under Background of Machine Learning

Retracted: Simulation of Flow-Induced Vibration and Dynamic Performance of Circular-Arc Helical Gear Pump under Background of Machine Learning

Numerical Study on the Influence of Different Operating Conditions on Mixing Uniformity of the Helical Gear Pump Mixer

The uniformity of the gelatin solution and water mixing process is a critical factor in the performance of helical gear pump mixers that affects pump efficiency. In this study, we investigate the impact of water inlet velocity and rotational speed on the helical gear pump mixer. A numerical model of the helical gear pump mixer is established using Simerics MP+ 5.2.15 software. By varying the water inlet velocity from 0.159 m/s to 1.272 m/s and the rotational speed from 8 rpm to 50 rpm, we obtained volume fraction distributions of water in different sections of the helical gear pump mixer. The simulation results show that the high water inlet velocity causes the water and gelatin solution in the mixing tank to not mix fully. When the inlet speed is 0.318 m/s, the mixing uniformity of the gelatin solution and water in the mixing tank is effectively promoted, and the maximum volume fraction of water in the water-rich region is reduced by 70.24%. In poor water regions, the maximum volume fraction of water increased by 9.25 times. Furthermore, within a certain range, increasing the rotational speed of the helical gear pump promotes the faster transport of water to the back of the mixing tank, leading to reduced non-uniformity in the gelatin solution and water mixing process. These findings provide valuable insights for enhancing mixing uniformity in helical gear pump mixers.

연속 접촉 헬리컬 기어펌프의 수치해석 연구: 모델 개발 및 적용

연속 접촉 헬리컬 기어펌프의 수치해석 연구: 모델 개발 및 적용

Helical Gear Pump: A Comparison between a Lumped Parameter and a Computational Fluid Dynamics-Based Approaches

This research presents a comparison between two numerical approaches developed and later compared for studying External Gear Pumps (EGPs). Models have been developed for studying pumps with helical gears. Firstly, a three-dimensional (3D) CFD numerical model has been built using a commercial code. Then, a new tool called EgeMATor MP+, completely developed by the authors and capable of completely simulating this pump’s typologies is presented. Thanks to different subroutines developed in different interconnected environments, this tool can fully analyze those pumps, starting from the drawing. Both numerical approaches have been detailed, highlighting their strengths and weaknesses and the tweaking required to reach more accurate results. Both numerical models have been set up with the same boundary conditions to obtain a more accurate comparison. Comparisons have been performed using tests performed on a commercial pump taken as reference, focusing on steady-state volumetric performance as well as the transient features of the outlet port pressure oscillations. The comparison of the (Q,p) characteristics showed that the 3D CFD numerical model has a slightly better accuracy, but both models have errors that fall into the uncertainty range of the experimental measurements. In addition, the pressure ripples comparison verified good agreements, where also the double flank behavior of the pump is predicted. While comparing the two simulation approaches, the paper highlights the limits and strengths of each one of the two approaches. In particular, it is shown how both models can match the experimental results considering proper assumptions. The paper constitutes a unique contribution to the field of numerical simulation of EGPs and represents a useful reference to designers looking for suitable methods for simulating existing or novel design solutions.

Simulation of Flow-Induced Vibration and Dynamic Performance of Circular-Arc Helical Gear Pump under Background of Machine Learning

At present, with the continuous development and great improvement of mechanical manufacturing, processing, and assembly technology, mechanical flow-induced vibration (FIV) with a relatively concentrated frequency domain can be controlled by active and passive noise reduction methods. However, whether it is active noise reduction or passive noise reduction, they all focus on how to suppress the transmission of sound waves and cannot solve the problems of flow leakage, obvious temperature rise, and noise excitation from the root cause. Therefore, it is necessary to determine the location of the primary and secondary excitation sound sources of FIV, the identification of true and false sounds, and the characteristic relationship between flow and noise. This provides a theoretical basis and engineering application direction for the mechanism of noise reduction of FIV. The numerical calculation part of the acoustics in this paper is solved by the hybrid method, and the flow field is discretely calculated by the large eddy simulation (LES) module in the Fluent software. When the calculated flow field is stable, the velocity field of one impeller rotation period is selected to be output as the iterative value of the sound field and imported into ACTRAN for Fourier transform. Then, the sound field calculation is carried out, and the result of the spatial and temporal variation of the sound field is finally obtained. Through experiments, it was found that when the load of the gear pump is 8 MPa, the volumetric efficiency of the optimized circular-arc helical gear pump of the sliding bearing was improved by about 4%. When the rotation speed is 2100°r/min, the arc helical gear pump reduced the surface temperature rise by 2.5°C. This verified that the optimized performance of the sliding bearing in the arc helical gear pump is significantly improved. Through the theoretical model of the temperature rise of the sliding bearing, the phenomenon that the surface temperature of the prototype gear pump was not significantly increased with the loading in the low pressure region is explained.

Multi-domain simulation and dynamic analysis of the 3D loading and micromotion of continuous-contact helical gear pumps

This paper presents a multi-domain dynamic simulation model for continuous-contact helical gear pumps, which is an unconventional hydraulic pump design that is capable of canceling its kinematic flowrate variation. In this model, the fluid dynamics (in its lumped-element representation) are fully coupled in a closed feedback loop with other physical domains, including critical tribological interfaces, 3D dynamic loadings on the solid parts, dynamics, and micro-vibrations of the rotors. The model is compared to the analytical derivation and experimental measurements to prove its validity. The model can be used to provide predictive simulations for existing designs, or as a tool to optimize the design to provide better hydrostatic balancing for future iterations of hydraulic pump designs.

Analysis of axial force of double circular arc helical gear hydraulic pump and design of its balancing device

In view of the axial force produced in the working process of double arc helical gear hydraulic pump, the theory of differential equation of curve and curved surface was utilized so that the calculation formula of axial force was obtained and the relationship between the axial force and structure parameters of gears was clarified. In order to balance the axial force, the pressure oil in the high pressure area was introduced into the end face of the plunger to press the plunger against the gear shaft, and the hydrostatic bearing whose type is plunger at the end of the shaft was designed. In order to verify the balance effect of axial force, the leakage owing to end clearance and volume efficiency of gear hydraulic pump before and after the balancing process was analyzed. This paper provides a new analysis idea and balance scheme for the axial force produced in the working process of the double arc helical gear hydraulic pump, which can reduce the leakage owing to end clearance caused by the axial force and improve the volume efficiency of the gear hydraulic pump.

A comparison of helical and spur external gear machines for fluid power applications: Design and optimization

This paper addresses the problem of determining the relative performance of spur and helical external gear pumps (EGPs) for fluid power applications. Helical EGPs are commonly considered as quieter units than spur ones; however, there is no specific study reported in literature that proves such claim. Similarly, it is hard to find data indicating which design is better in terms of compactness or energy performance. To tackle this problem, a procedure is developed for virtual design optimization of both helical and spur gear EGPs. This includes addressing the two fundamental challenges of the work, parameterizing a generic EGP design and quantifying its performance. By applying this procedure, a genetic algorithm can continue improving from generation to generation, until the pareto optimal set of designs is identified for both helical and spur units. In the comparison of these, the differences between the two configurations will be identified and the fundamental question of this work can be answered; are helical gears ‘better’ than spur gears?

Analysis of continuous-contact helical gear pumps through numerical modeling and experimental validation

Abstract External gear pumps are one of the most commonly used types of positive displacement machines in high pressure hydraulic control systems, fuel-injection and fuel transport systems. Despite many merits of the traditional external gear pump design with involute teeth, the significant flow non-uniformity intrinsic of such design is considered to be a detrimental aspect, since it causes undesired noise emissions and mechanical vibrations. A disruptive concept of continuous-contact helical gear pumps (CCHGP) was proposed and successfully commercialized in the recent past. Such concept was proven to have clear advantages in terms of noise emissions. However, a clear interpretation of the displacing action and the transient features of the delivery flow was never addressed in past literature. This paper addresses this gap by first discussing the family of gear profiles suitable for implementing the CCHGP design. Subsequently, an analysis on the kinematic flow ripple is given, showing how such design concept can reduce or even eliminate the kinematic flow pulsations. The paper also presents a numerical approach for modelling the operation of CCHGPs, starting from the modeling of the geometric features necessary for a fluid dynamic analysis based on a lumped parameter approach. For model validation purposes, a commercial CCHGP was tested at the authors’ research center, and the simulation results were compared against the experiments, to show the level of accuracy of the model, as well as it potentials for future design studies.

As-Applied Estimation of Volumetric Flow Rate from a Single Sprayer Nozzle Series Using Water-Sensitive Spray Cards

<abstract> The objective of this study was to test the feasibility of using coverage measurements from water-sensitive spray cards to estimate the volumetric flow rate at an individual sprayer nozzle. TeeJet VisiFlow Even Flat Spray Tips were selected due to their uniform distribution of coverage. Spray distribution for each nozzle was validated using a spray patternator table with 2.5 cm sampling widths. A rotary test fixture translated water-sensitive spray cards through the spray dispersion (water at ambient conditions) at a constant angular velocity and a radius of 1.2 m. The test fixture measured volumetric flow and pressure at the nozzle and recorded data at a rate of 10 Hz. A helical gear pump and a piston-type pressure regulating valve were used to provide constant pressure. The first experiment fixed the test fixture speed at 3.14 rad s-1 and used varying pressures from 70 to 552 kPa (10 to 80 psi) in 70 kPa (10 psi) increments. First-order and second-order regression models were developed for the nozzle series, and validation data were collected at intermediate pressures to test the ability of the model to predict volumetric flow rates. The second experiment fixed the system pressure at 310 kPa (45 psi) and varied the speed of the test fixture at seven increments between 2.0 and 3.8 rad s-1. Spray cards were digitized using a scanner and processed for coverage using the MATLAB image processing toolbox. Results showed that the accuracy of the spray card method was within 1% full-scale of a commercial impeller flowmeter for a single series of nozzles moving at constant speed. Varying speed could be accounted for but required knowledge of the individual nozzle model.

A CFD study of an Electronic Hydraulic Power Steering Helical External Gear Pump: Model Development, Validation and Application

A CFD study of an Electronic Hydraulic Power Steering Helical External Gear Pump: Model Development, Validation and Application

A method for variable pressure load estimation in spur and helical gear pumps

A systematic procedure is proposed to determine variable excitation loads coming from pressure evolution inside tooth spaces in external gear pumps. Pressure force and torque are estimated with respect to the angular position of the gears, taking into account the phenomena that occur during the meshing course. In particular, the paper proposes a general methodology aiming at determining pressure force and torque components along the three coordinate axes and suitable to be applied on both spur and helical gear configuration. Firstly, the method to calculate pressure loads acting on a single tooth space during a complete revolution is given, then the total pressure force and torque loading each gear is obtained. Particular attention is addressed on the description of the helical gear scenario. As an example, the method is applied to a tandem gear pump, characterized by the presence of two stages, one with spur gears and one with helical gears. An experimentally assessed model to calculate the pressure ripple inside the tandem pump is described and the proposed procedure for pressure load estimation is applied. Eventually, the pressure loads estimated with the present procedure are compared with other estimation methods already described in the literature. The comparison shows that the present methodology is able to describe a wider range of phenomena involved in the meshing evolution and to determine all the pressure force and torque components applied to helical gears. The method gives suitable results to study the balancing and the dynamic behavior of gear pumps.

Design of the Tooth Profile of a Full Conjugate Helical Gear Pump

In this paper, the tooth profile of a kind of full conjugate helical gear pump was designed. The tooth profile of each of the gears is composed of three curves which are an addendum arc, an involute and a dedendum curve. The dedendum curve of one gear is the conjugate curve of the addendum arc of the other gear. The addendum arc and the dedendum curve are joined tangentially by an involute. The equations of the curves were deduced by using differential geometry. The ranges of parameters in these equations were also obtained. The meshing characteristics of the gears were analyzed. Two gears transmit continuously with a fixed ratio. Two gears engage each other point by point continuously along the entire profile and formed a continuous space meshing curve. The trapping oil phenomenon could be eliminated and the sealing property could be better than conventional involute gear pumps. The results of calculation and analysis of an application example showed the theoretical analysis and the practicability of the design were valid.

Geometric displacement optimization of external helical gear pumps

An approach to geometric displacement optimization of external helical gear pumps is presented. In addition, relations of pump flow property and its influence factors are also investigated. During that, only the pumps with transverse contact ratios of not less than one are discussed. First, using the involute property, an analytic representation for flowrates is deduced, by which displacements and fluctuation coefficients of helical gear pumps can be calculated accurately and efficiently. Then, by incorporating several design considerations, optimization problems for maximum geometric displacement are formulated and solved integrally by an optimization code, Multifunctional Optimization System Tool, with which various types of design variables including real, integer, and discrete can be simultaneously dealt with. Finally, the desired pumps with optimal displacement can be obtained. The proposed approach facilitates the design optimization of helical gear pumps. Moreover, influences of design parameters on the displacement and flow characteristics of the optimal pumps by assigning individual parameters are investigated. The result also concludes that the pump with a larger module, larger face width, or smaller tooth number has bigger displacement but may cause more severe flowrate fluctuation.

Geometric modelling for cylindrical and helical gear pumps with circular arc teeth

This paper describes a simple approach based on the envelope theory for deriving the geometric models of cylindrical and helical gear pumps with circular arc teeth. A gear pump with circular arc teeth can be easily obtained through the envelope theory for a one-parameter family of surfaces. In the process of machining a gear blank, the required rack-cutter teeth can be obtained by using the obtained cylindrical and helical gears, whose forms are easily determined by the envelope theory. Here the authors provide geometric modelling of the designed gear pump meshing when assembly errors are present. To illustrate the effectiveness of the approach, an analytical expression of cylindrical and helical gear pumps with circular arc teeth is given.

Gear pumps with new release ports suitable for various running conditions. (Theory for the release ports and some experimental results).

Earlier equations used to calculate the positions of the release ports of gear pumps were derived without considering changes in running conditions which are apt to occur in field applications. Therefore, gear pumps designed using these equations gave lower efficiencies in some, or most, running conditions. With the support of the theory, the authors found new release ports suitable for the gear pumps to be operated under various running conditions. Experiments were conducted using two helical gear pumps with conventional and new release ports. The pump with the new release ports brought about larger deliveries and also higher efficiencies. The reason for this is explained by the theoretical characteristics of the gear pumps.

Gear pumps with new release ports suitable for various running conditions. (1st Reports, Theory for the release ports and some experimental results).

Earlier equations for calculating the release ports of gear pumps were derived without considering changes in running conditions which are apt to occur in field applications. Therefore, gear pumps designed using these equations gave lower efficiencies in some or most running conditions. With the support of theory, the authors found new release ports suitable for the gear pumps to be operated under various running conditions. Experiments were conducted using two helical gear pumps with conventional and new release-ports. The pump with the new release ports brought about larger deliveries and also higher efficiencies. The reason for this is explained by the theoretical characteristics of the gear pumps.

A New Continuous Contact Low-Noise Gear Pump

Developed is a new low-noise gear pump which has no trapping and whose gears are in continuous one-point contact in the plane of rotation. First this paper studies a practical method to design the tooth profile of a spur gear for a given path of contact. A new tooth profile is obtained by giving a closed path of contact like a figure 8. Basic dimensions are determined and limites of them are obtained. Both theoretical and approximate displacements are expressed in terms of the basic dimensions. Secondly, a helical gear pump is studied. The helical gear can be discussed in the same way as the spur gear by new basic dimensions. Finally some test gear pumps are made and tested. Test prove that this gear pump has excellent performance and durability.

On the Theoretical Characteristics of Shifted Helical Gear pump

In gear pumps which have a relatively small number of gear-teeth, the shifted gears are usually used to avoid the undercutting of the tooth profile. Besides, to equalize the wear of all teeth, the number of teeth of the driving gear is ofen different from that of the driven gear. For such gear pumps the author calculates the ideal delivery, the pulsation of the delivery, the variation or the trapped space, and the relation between the position of the pressure release port and the helical angle.