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Increasing demands for high-performance screw pumps in oil and gas as well as other applications require deep understanding of the fluid flow field inside the machine. Important effects on the performance such as dynamic losses, influence of the leakage gaps and presence and extent of cavitation are difficult to observe by experiments. However, it...
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The current numerical study is conducted to present a computational analysis on the turbulent flow of air and conjugate heat transfer in a pipe of rectangular section provided with waved fins which are arranged on the bottom and top channel walls in a periodically staggered way (figure 1). To this end we solved numerically, by the finite volumes me...
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... A 3D CFD study of a twin-screw pump is performed to finally determine that the circumference deviation is not the main contributor to the backflow rate, but that it is the flank deviation [11]. There are other research works in the literature discussing simulations and modeling of this type of gear (e.g., [12,13]). Finite element analysis is frequently used in strength calculation of pumps, and the study of Cieślicki and Karpenko [14] is one example of the recent studies that used this approach. ...
The hydraulic circuit in hydraulic mechanisms may be the cause of several vibration anomalies. Flexible pipes, in particular, commonly used in test rigs, may be the source of vibration issues due to their relatively low natural frequencies altering the pump noise, vibration, and harshness (NVH) performance. The purpose of this study is to detail a methodology based on lumped parameter modeling and experiments to analyze the circuit NVH behavior. An experimental study is carried out on two pump designs to determine the outlet pressure fluctuation of various test rig configurations. Numerical simulations are also performed to simulate the actual behavior of the hydraulic system considering these different test configurations. The tests are carried out at a chosen frequency range with a hydraulic circuit configuration representing realistic layouts. In these situations, the hydraulic circuit layout can be the source of NVH anomalies. Realistic design solutions are proposed to modify the test rig NVH behavior in order to achieve a flat response throughout the desired working range.
... 20,21 At present, the numerical simulation of the flow field in twin-screw pumps has mainly focused on singlephase flow 22,23 and gas-liquid two-phase flow. [24][25][26] However, the study of solid-liquid two-phase flow in twin-screw pumps had yet to be reported. Miao conducted a numerical study on the motion characteristics of sediment particles in a bidirectional twin-screw pump using SCORG and Pumplinx. ...
The rotors of twin-screw pumps would be worn by hard particles for deep-sea oil and gas mixture transport. It led to the destruction of the seal clearance and the deterioration of pump performance. Based on the Euler–Lagrange method and dynamic grid technology, the transient numerical simulation of solid–liquid two-phase flow in a twin-screw pump was carried out and validated by experiment. The motion characteristics of particles in the tip, interlobe, flank clearance, and the causes of rotor wear were clarified. The results revealed that the severe wear at rotor tips was caused by the particles when they enter the tip clearance rather than leaving the tip clearance with the leakage jet flow. Particles passing through the flank clearance had high velocity and contributed to the wear at rotor tips. The main flow in the tooth chamber was disturbed by the interlobe and flank clearance leakage, even resulting in local high-speed reflux near the engagement. With the increase in the particle concentration and diameter, the collision frequency between particles and rotor tips increased, aggravating the risk of wear at rotor tips. The research could reveal the motion nature of particles following the liquid phase and their wear mechanism in twin-screw pumps.
... Due to the density difference between phases, the centrifugal force of the liquid with a large density is greater than that of the gas phase, leading to the liquid and gas moving towards the shroud and hub, respectively [51]. CFD simulation is one effective method and is widely used in the flow prediction of the multiphase pump, which has the advantages of short calculation time and low cost [83]. ...
Flow and phase separation in gas–liquid multiphase pumps is easy to occur, which deteriorates their performance and mixed transportability. Many research achievements have been made in the experiment, CFD simulation and performance improvement of multiphase pumps. However, there are many challenges for the test technology, accurate numerical model development and gas–liquid flow control. This paper is mainly aimed at critically reviewing various technologies for experimental observation, flow calculation and analysis, and the optimization design of gas–liquid multiphase pumps. In this regard, the experimental results including the energy performance, flow pattern and bubble movement in the multiphase pump are presented in detail. Discussions on the turbulence model, multiphase flow model and bubble balance model are carried out for the flow prediction in such pumps. Various numerical results are presented, including energy performance, bubble distribution, vorticity, phase interaction and pressure fluctuation. Moreover, the flow control and optimization strategy are briefly introduced. Having carried out an extensive literature review of flow characteristics in multiphase pumps, the deficiencies of relevant fields and suggestions for future research direction are given.
... In the analysis of the flow field, the static body-fitting mesh is used in most of the articles, and the analysis results ignore the momentum of the flow field when the rotor rotates. The dynamic bodyfitted mesh method [13,14] is also used, although the calculation is easy to converge, the error is large compared with the real results. Compared with the body-fitted mesh generation method, the Cartesian grid method has less dependence on the object surface and can be used for meshing various complex surfaces. ...
Vacuum pump is widely used in aviation, chemical, semiconductor and other fields because of its superior performance. In order to study the internal flow characteristics and pump performance, 1-D Chamber Model method and the CFD modelling method based on static grid are commonly used, such methods ignore many important three-dimensional transient flow details. However, in numerical modelling of three-dimensional transient flow field for hook and claw-type vacuum pump with cusps in the rotor profile, the generation of flow field grid is always a challenge. The body-fitted mesh method is difficult to generate effective dynamic grid for such kind of fluid domain, which usually leads to the divergence of calculation. In order to solve these problems, the cut cell Cartesian method is proposed to simulate the three-dimensional transient flow field in hook and claw-type vacuum pump. Firstly, the mathematical basis of the cut cell Cartesian method was introduced in detail, in which the immersed boundary method (IBM) was combined with the generation process of adaptive Cartesian volume mesh. Aiming at modelling the hook and claw-type vacuum pump, firstly, the profile design method of hook and claw-type vacuum pump was derived, and the geometric model of the calculation domain was established. The transient flow field characteristics of the vacuum pump with different inter-lobe clearance sizes were analyzed, and the velocity, pressure, vortices and temperature characteristics inside the vacuum pump were obtained. The influence of clearance variation on the performance of the vacuum pump was discussed. The feasibility and accuracy of the method were verified by a study case of a two-stroke reciprocating piston pump. The research provides a good reference for dynamic grid generation and precise numerical simulation of hook and claw-type vacuum pump.
... Xudong He et al. [5] by introducing the non-uniform rational B-spline curve and the theory of computational fluid dynamics into the rotor profile design of the twin-screw compressor, a unilateral asymmetric cycloid-pin tooth arc combined rotor profile is proposed, and a new rotor profile is obtained. DiYan et al. [6] through the finite volume method, instantaneous mass flow, rotor torque, local pressure field, velocity field, and other performance indicators including indicated power were investigated. Comprehensive tests of discharge pressure and rotational speed were performed, and experiments showed that the predicted results matched the measurements, the validity of the computational fluid dynamics model is verified, and it is found that the radial gap has a greater effect on the mass flow than the intermediate flow gap. ...
In order to reduce the leakage between the teeth of the twin-screw pump and improve the working performance, it is necessary to reduce the clearance between the teeth; In this paper, the end face profile equation of A-type screw rotor is derived by coordinate transformation method, the end face profile is generated based on MATLAB software, and the cusp and curve of the profile are optimized by arc transition method; The changes of pressure field and velocity field in the fluid domain of screw rotor before and after optimization are analyzed by finite element method; Taking the twin-screw pump as the research object, the fluid-structure coupling analysis and calculation of the master and slave screw rotors are carried out. The modal analysis of the screw without prestress and under the action of prestress is carried out respectively. Through the simulation calculation, the first six modal vibration shapes of the screw are taken, and the results of the two different states are compared. The results show that when the working pressure difference is 2 MPa, the maximum pressure after optimization increases by 1 % compared with that before optimization. With the continuous increase of center distance, the maximum pressure of flow field fluctuates slightly up and down; The maximum velocity after optimization is 3.5 % lower than that before optimization. The comparison results show that the frequency of the screw rotor increases with the increase of the modal order of the screw rotor without prestress. The frequencies of the second and third orders are similar, and the amplitudes of the first and fourth orders are similar. After the fluid-structure coupling force is applied, the change trends of the modal frequencies of each order are basically the same, but the magnitudes of the frequencies and amplitudes change. The amplitude of the main and driven screw rotors under the fluid-structure interaction decreases rapidly in the third-order vibration mode and is lower than the amplitude without prestress.
... Therefore, the design of the blade airfoil is the key factor affecting the hydraulic performance of the axial-flow pump. (Kim et al., 2015;Yan et al., 2016;Shi et al., 2020). The composite airfoil first appeared in the design theory of wind turbine blades. ...
Operating efficiency and reliability are major problems that restrict gas-liquid multiphase pumps, which are core pieces of equipment used in deep-sea oil and gas exploration and transportation. In this paper, a 100-20x helical axial-flow gas-liquid pump is taken as the research object. The Euler multiphase flow model and SST k-ω turbulent model are used to model the multiphase pump. By exploring the airfoil composite position and the maximum thickness composite scheme, a mathematical model for the head coefficient and efficiency of the multiphase pump with respect to the relative thickness is established, and the external and internal flow characteristics of the modified multiphase pump are analyzed. We explore the influence of the composite position and the maximum thickness variation law of the composite airfoil on the performance of the mixed pump and determine the final airfoil composite scheme. We found that a change in the maximum thickness of the composite airfoil gives the external curve of the multiphase pump a “hump"-like characteristic, which shows that the head coefficient and efficiency increase first and then decrease with the increase in the maximum thickness of the composite airfoil. When the composite position is in the middle of the airfoil, the airfoil maximum thickness is 1.25 mm and the gas-phase volume fraction is 70%. Moreover, the head coefficient and efficiency of the multiphase pump reach their maximum values; the head coefficient and efficiency increase by 2.4% and 1.16%, respectively, compared with the basic model.
... Due to the action of hydrodynamic loads, which most often arise from periodic approach of the bit to the bumpy bottom of a well [3], the friction forces of the infiltrate against the walls of the pore channels decrease and, accordingly, its intensity and depth of penetration into the PFZ increase. The difference between penetration intensities of washing fluid infiltrate into PFZ is clearly shown in Fig. 1 [5][6][7]. Fig. 1 shows that the pattern of infiltration into the formation due to static pressure drop and turbulence of the fluid flow to the bottomhole (quasi-static infiltration) cannot explain the infiltration depth observed in the fields (by the volumes of fluid collected by the reservoir testers) -up to several meters in relatively low-permeability (up to 0.02...0.10 μm 2 ) reservoirs. Such infiltration is satisfactorily explained only by the hydrodynamics of the "string-well-well bore zone" system. ...
... In a particular case, for flat waves, the solution of equation (2), taking into account the analysis of hydrodynamic waves given in work [5], is characterized by the depth of penetration of the washing fluid infiltrate into the PFZ during drilling and the RTO shown in Fig. 2 and Fig. 3. But in low-permeability reservoirs with pore channel diameters up to 10...20 μm [8,9], due to friction forces of their formation fluids against the walls, due to the static pressure drop in the "formation-well" system, it is difficult to restore the natural permeability of PFZ at an infiltrate penetration depth of more than 1...2 m. ...
The paper considers the influence of crank radius change on pumping unit kinematics during the dynamic fluid level control between tubing and casing in order to reduce the string fault rate. To improve the quality of prediction of these factors, the calculation of the movement of the polished rod over time is carried out using the Fourier variable separation method: the product of the balance bar head of a pumping unit defined as the movement of the slider of the pumping mechanism (in a straight line – like the chords of a circle), and the difference of such a chord with the length of the circle section equivalent to the movement of the articulated joint of the balance bar with the connecting rod. As a result, the accuracy of calculations is improved and the solution of the problem is simplified.
... Using a twin-screw pump as the object of study, the contact line equations for the screw tooth profile and spiral surface were derived and the flow, pressure, and velocity fields were simulated numerically [1,2]. Moreover, the flow characteristics of the fluid in the pump and the process of cavitation formation were investigated under different speeds and discharge pressures [3,4]. The temperature and pressure distribution at multiple points of the progressive cavity pump was obtained experimentally and the effect of screw deformation on the leakage and volumetric efficiency of the progressive cavity pump was analyzed [5,6]. ...
... For investigating the complex turbulent flow field in the triple screw pump, a two-squared -epsilon ( -) turbulence model was used for the calculations and a semi-implicit method of pressure connection equations (SIMPLE) was used for the numerical simulation of the triple screw pump with a convergence accuracy of 10 -4 . The flow field boundary conditions were set for the inlet and outlet pressures (3)(4)(5). Based on the actual operating conditions of the triple screw pump, hydraulic oil No. 46 was used as the delivery medium. ...
To accommodate special applications where installation space is limited and noise and vibration requirements are high, a new triple screw pump structure was proposed, which was integrated into a servo motor. The design optimizes the profile of the master and slave screws of the embedded triple screw pump. The temperature and pressure fields of the embedded triple screw pump, as well as the heat transfer and pressure distribution between the fluid in the pump and the screw, were investigated through a thermal-fluid-structure approach. The deformation and stresses of the screw were compared for three operating conditions: temperature loading, pressure loading, and thermal-fluid-structure coupling. The results show that the deformation and stresses in the screw tended to increase with increasing pressure and temperature and the pressure load caused more significant deformation and stresses in the screw than the temperature load. The screw deformation caused by pressure loading was found to be the main factor affecting the thermal-fluid-structure coupling. The screw deformation after coupling was smaller than the sum of the screw deformation caused by individual temperature and pressure loads, and the stress values were the same. The results indicate that the coupling action weakens the deformation and stresses in the master and slave screws.
... A flow meter and a throttle valve are installed in the pipeline. The real-time flow rate and outlet pressure can be measured in this hydraulic system [15]. pump calculated by static grid at different rotation angle positions is shown in Figure 7. From the calculation results, it can be seen that the instantaneous leakage of the screw pump changes with the change of the screw rotation angle, and it also shows periodicity. ...
Three-dimensional CFD numerical simulation is the most powerful tool for performance analysis of screw machines. This paper compares and analyzes two CFD numerical calculation methods based on moving and static grid, and proposes a static grid calculation method based on momentum compensation, which takes into account the wall velocity and fluid momentum on the rotor surface when the screw rotor rotates. That is, while the static grid is used, the rotation characteristics of the fluid domain between the rotors are considered. Compared with the commonly used static grid method, this method greatly improves the accuracy of the calculation, the calculation error of mass flow rate is reduced from 2.32% to 1.14%. At the same time, it is simple and easy to implement. It is also suitable for modelling screw machines with special-shaped rotors, which are still challenge for moving grids. The accuracy and reliability of the method are verified by comparison with the calculation results of the moving grid and the experiments.
... They are responsible for bringing gas in and out of the working chamber of the pump. Yan et al. (2016) [19] in the research of numerical modeling of twin-screw pumps mentioned that the port geometry has little effect on the mass flow rate but has significant effect on power. Also, it was noted that the port shape has possible effect on pressure distribution and shaft power. ...
... They are responsible for bringing gas in and out of the working chamber of the pump. Yan et al. (2016) [19] in the research of numerical modeling of twin-screw pumps mentioned that the port geometry has little effect on the mass flow rate but has significant effect on power. Also, it was noted that the port shape has possible effect on pressure distribution and shaft power. ...
Due to the sharp discontinuities in the profile of hook and claw pumps which make it difficult to produce a good quality body fitted mesh, their CFD simulations are challenging. However, the cut-cell Cartesian meshing method is capable to handle the very complex moving geometries and is easy to setup. However it may lead to conservativeness issues. The aim of this paper is to investigate the influence of discharge port geometry of the hook and claw pump on its performance by using commercial software ANSYS Forte, which utilizes automatic mesh generation using the cut-cell Cartesian method. Firstly, five discharge ports with different geometries were designed. Secondly, the pumps with these different port configurations were set up and ran in the ANSYS Forte. Finally, the power and volume flow rate were compared. It was noticed that the geometry with the extended discharge port tip and the preliminary discharge port opening result in performance and reliability improvements. The simulation results can be used to further optimize the discharge port during the design of these machines.
