CFD Analysis of Impeller Internal Flow Field in Multistage Pump with Inducer

Injecting oilfield waste into suitable receiving formations is an effective and environmentally acceptable method to dispose of drilling and production waste including cuttings, drilling fluids, produced water, emulsions and other produced waste. Traditionally, solid waste is degraded to less than 300 microns and suspended as water-based slurry containing 20% solid matter. Rheological properties are controlled so that the slurry can be injected, typically using triplex pumps, under high pressure (1000 to 5000 psi) through a casing annulus or tubular into hydraulic fractures. At locations, where injection pressures are within limits and the disposal well and domain may cope, or be benefitted with higher rates of injection, increases in the rate of disposal is beneficial to operations due to the increased efficiency allowing faster ROP's or faster evacuation of waste storage devices. This paper discusses the suitability and application of multistage centrifugal pumps for drilling waste injection and provides some data obtained during real time waste injection operations using multistage centrifugal pumps in parallel installation with traditionally used triplex pumps. Wear data in conjunction with engineering economic evaluation will be discussed. Slurry viscosity and particle size data will be presented to show the effect of pump shear on slurry properties and the implications for waste injection. A multistage centrifugal pump proved capable of pumping waste slurry continuously at relatively high rates for a limited trial period of time. A multistage centrifugal pump provides a continuous flow without the pulsation normally associated with using a reciprocating plunger-style pump and the need to have such pulsation dampened. Laboratory testing and realtime subsurface injection data at an offshore installation indicates that multistage horizontal centrifugal pumps may offer some benefits compared to traditional reciprocating triplex plunger pumps. Some operations requiring relatively high flow rates with flow media containing solids may benefit from implementation of this style pump providing the net power requirement and equivalent downhole pressure requirement are within the pump design range, and there is available footprint at the location. Oilfield waste can be disposed of in an environmentally responsible manner under zero-discharge conditions with the performance of the pump ensuring operational reliability and injection assurance. Operations on a global scale may benefit from this new application for multistage pumps. Decreased downtime together with slurry stability and controlled injection assures operational performance and cost effectiveness, enabling oilfield waste to be disposed in a safe, controlled and environmentally responsible manner.

Radiated noise is unavoidable in the operation of multistage centrifugal pumps. In order to study the characteristics of radiated noise of multistage centrifugal pump, radiated noise test system of multistage centrifugal pump was built. Radiated noise experiments were carried out for a medium specific speed multistage centrifugal pump and its modification, which was devised with a new hydraulic design method in the field of sound optimization. The experiment validation on the sound field was performed in a semi-anechoic room and the acoustic parameters of the multistage pump at the different flow rates were gathered with the LMS system(a complete set of solutions for vibration and noise test). The results show that: As the speed is lower than the rated speed, the sound pressure level (SPL) of the radiated noise of centrifugal pump increases with the increase of rotating speed. And the radiated noise of multistage pump rises linearly with the increase of rotating speed. The maximum value of sound pressure level appears around the first stage and the minimum value appears around the middle stage at different flow rates. As the flow rate increases, SPL measured around vane diffuser increases and then decreases. In addition, discrete noise occupies the dominant position in the form of noise for both pumps at large flow rate. Compared with the prototype pump, the intensity of radiated noise of the modified pump weakens in varying degrees in the range of the whole variable speed. Furthermore, the radiated noise exhibits a dipole characteristic at low rotating speed.

In the depths of the ocean, where minerals lie buried beneath layers of sediment, multi-stage pumps serve as the workhorses of deep-sea mining, lifting extracted materials through immense vertical distances. To ensure their efficiency and reliability, a comprehensive hydrodynamic analysis is required, focusing on vortex-induced vibrations and fluid–structure interactions. In this study, numerical simulations were conducted using computational fluid dynamics to investigate the internal flow characteristics of a multi-stage deep-sea pump. The distribution and formation mechanisms of vortices were analyzed using the omega vorticity identification method, which allowed for the capture of vortex structures and the evaluation of entropy production in the impeller and guide vanes across varying flow rates. The results revealed that at low flow rates, complex vortex structures, including flow separation and reflux vortices, were predominant at the impeller inlet. As the flow rate increased, these vortices gradually dissipated, leading to a more stable wake at the impeller outlet, while separation and reflux vortices became more pronounced at the guide vanes' inlet and outlet. A reduction in the blade passage vortex structure was also observed with increasing flow rates. Further analysis demonstrated that the stretching and twisting term played a crucial role in the formation, evolution, and dissipation of vortex structures at the guide vanes' inlet. Meanwhile, the Coriolis force was identified as a key factor in vortex generation at the impeller inlet and within the blade passage. These findings provide valuable insights into the vortex dynamics governing deep-sea pump hydraulics, offering a foundation for optimizing their design to enhance operational performance and ensure more efficient deep-sea resource extraction.

The axial force balancing capacity of a balance drum is a key factor affecting the life of multi-stage centrifugal pumps. In this paper, a double shell segmental multistage pump is taken as the research object. The hydraulic performance and axial force performance are set as the optimization objectives, and the performance data are obtained by numerical simulation with FLUENT software. The BP neural network is used to establish the prediction model of structural parameters of the balance system, hydraulic performance and residual axial force performance, and it is used as the adaptive value evaluation model of genetic algorithm to solve the optimal value in the sample space. The results show that the radial clearance of the balance drum and the balance tube orifice flowmeter, the axial width of the balance cavity are the significant factors affecting the hydraulic performance and axial force performance of the multistage pump. When the radial clearance of the balance drum is 0.1mm, the clearance of the orifice flowmeter is 1.95mm, and the axial width of the balance cavity is 55mm, the multi-stage pump has the best hydraulic performance and the smallest residual axial force. The vortex band in the balance cavity can increase the amount of the fluid spin and enhance the axial force balancing capacity of the balance drum. The greater the area occupied by the negative high-rotation fluid in the balance cavity, the stronger the ability of the balance drum to balance the axial force. The test results show that compared with the prototype multistage pump, at nominal flow rate, the head and efficiency of the optimized model are increased by 0.71% and 1.63% respectively, and the bearing temperature and vibration speed of the multi-stage pump are significantly reduced.

When predicting the performances of a centrifugal pump by eddy-resolving computational fluid dynamics (CFD) methods such as Large-Eddy Simulation (LES), it is important that the phenomenon of interest and associated flow eddies are accurately computed. Despite recent performance improvement of high-end computers, it is still a challenge to compute a whole multi-stage pump with leakage parts by applying fully-resolved LES and to directly compute active eddies in the turbulent boundary layers, due to grid size requirements. As a part of the analysis of the flows in a multi-stage centrifugal pump by LES, present research focuses on the flow in the pump inter-stage bush. It aims at determining the flow regime, the associated eddies in the bush, and a better understanding of the flow in a grooved inter-stage bush to allow future design optimisations. To assess the existence of the turbulent boundary layer for different Reynolds numbers, focus was placed on the appearance of streamwise vortices which are the smallest active eddies in the turbulent boundary layer. It was observed that these vortices start to develop from Reω=1800 although the velocity profile looks of a laminar boundary layer. Finally, based on CFD results, the effectiveness of the stage bush in terms of minimizing the leakage flow is investigated for the different Reynolds numbers. It is found that the current design shows the maximum effectiveness for Reω=900, and its effectiveness decreases at a higher Reynolds number.

In centrifugal pumps, axial thrust bearings are required to compensate for the axial loading on the pump impeller(s). These forces are mainly the result of unequal distributions of pressure on projected areas at both sides of the impeller(s). Axial loading tends to be highest in multistage pumps in which all impellers face the same direction. Balancing devices are often used to reduce the loading of the axial bearings. Common types of balancing devices are the balance drum and the balance disc. Both of them have their advantages and disadvantages. A stepped balance drum is a new concept for a balancing device that can be used in any type of turbomachinery. It combines the benefits of the balance drum and the balance disk without the drawbacks of both. In this paper, the new concept is presented along with a semi-empirical model of its performance. A CFD analysis is also presented which serves to verify the analytical model. An optimization procedure of a stepped balance drum is given using a multistage centrifugal pump as an example.

The multi-stage centrifugal pump run instability at the original design point, and the running operating point deviated far from the design point during the run. In order to better meet the multi-stage centrifugal pump operational requirements, through hydraulic model modification, changing the multi-stage pump design point, while the performance curve before and after the modification can be interchangeable in the flow of 150m3/h~320m3/h. The original program used 3 blades impeller. Taking into account the matching problem with pressurized water chamber, modification plan used 5 blades impeller. Analysis on the internal flow field before and after the modification was made. Through comparison the internal and external characteristics of the two plans, the analysis found that in the double volute pressurized water chamber, the flow field symmetry of 5 blades is better than the 3 blades’. The flow field symmetry can be well balanced radial force, and help to improve the instability phenomenon in operation.

In a centrifugal pump the interaction between the rotating impeller pressure field and the stationary diffuser pressure field yields pressure fluctuations as the result of a modulation process. These fluctuations may induce hydroacoustic pressure fluctuations in the exit chamber of the pump and could cause unacceptable vibrations. This paper presents a methodology for the prediction of hydroacoustic pressure fluctuations resulting from rotor-stator interaction in a multistage centrifugal pump. The method consists in the one-way coupling of incompressible CFD and hydroacoustic simulations. In a first step the rotorstator pressure fluctuations are calculated using a commercial 3D-RANS CFD-code (CFX 10) for different flow rates. The acoustic simulations are performed in two consecutive steps. Initially a free oscillation analysis using white noise pressure fluctuations is performed, which provides hydroacoustic eigen frequencies and mode shapes of the outlet casing. In a second step the spatially distributed pressure fluctuations from the CFD simulation are used to perform a forced oscillation analysis. This approach allows the prediction of possible standing waves in the hydraulic collection elements in the last stage of multistage pumps.

CFD simulation of an agitated gas-fluidized bed: Effects of particle–particle restitution coefficient on the hydrodynamics

This study aims to investigate the icing behavior of unmanned aerial vehicles (UAVs) propellers under different operating conditions. Unlike previous work, a systematic analysis of droplet impingement, heat transfer characteristics, and ice accretion distribution on the blade surface is conducted, revealing the spatial distribution characteristics of propeller icing from multiple perspectives. The propeller flow field is solved using the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the Multiple Reference Frame (MRF) model, the droplet motion and collection are predicted by an Eulerian multiphase approach, and the icing process is modeled using the shear-stress transport-based shallow water film method (SWIM). The results show that higher rotational speeds and larger droplet diameters significantly increase ice accumulation, with more complex ice shapes forming particularly at the blade tip. In contrast, higher temperatures reduce the overall icing amount but alter the spatial distribution of ice. The blade tip region exhibits stronger transport capacity for unfrozen water, leading to faster ice accretion. These findings provide useful guidance for designing more effective anti-icing strategies for UAV propellers.

Aeroacoustic noise produced by high speed face milling cutters is a serious environmental concern. This paper develops a modeling approach to investigate the aeroacoustic noise generation and propagation by the idling face milling cutters. The approach consists of two parts: (1) an aerodynamic model for evaluating the flow fields based on the Navier–Stokes (N–S) equation and (2) an aeroacoustic model for predicting the acoustic noise by using the Ffowcs Williams and Hawkings (FW–H) equation. Both the steady mode with the multiple reference frames (MRF) model and the unsteady mode with the sliding mesh technique by introducing steady flow variables as its initial fields are simulated. The cutter gullet regions and the insert rake face regions are found to be the primary contributors in noise generation through spectral analysis of noise sources. The acoustic noise in face milling is significantly affected by the cutter diameter and the number of cutter teeth. The noise directivity is found in vertical plane, and the irregular tooth spacing can spread the maximum sound power at the rotating frequency to higher frequencies. In addition, experiments are conducted to measure the acoustic noise from two high speed milling cutters. It is found that the experimental results are generally in good agreement with the simulations.

Taking the AU5-50 propeller as an example, the detailed process of propeller modeling with atlas method and PropCad is compared. By comparing the auxiliary profiles used for modeling, it is pointed out that the blade model established by PropCad has more complete features and is not restricted by the propeller type. Besides, to verify the credibility of the PropCad modeling method, simulation analysis is carried out. First, the hybrid mesh and boundary layer mesh are divide for the flow field by integrated computer engineering and manufacturing (ICEM). Second, grid independence is verified utilizing a multiple reference frame (MRF) model. In the verifying process, three widely used turbulence models are analyzed and compared under advance ratio 0.7, and the results show that the hydrodynamic coefficient error calculated by the shear stress transport (SST) k-ω model is the smallest. Third, the computational fluid dynamics (CFD) calculation model is determined. The hydrodynamic performance of the propeller at different advance ratios is analyzed, and the CFD calculation results are in good agreement with the open water test data. Finally, the fluid-solid coupling analysis of the propeller is performed, and it is verified that the stress field of the propeller meets the material strength requirement. Therefore, it is proved to be feasible to conduct propeller modeling with PropCad.

Computational Fluid Dynamics analysis has been used to solve the unsteady three-dimensional viscous flow in the entire impeller and volute casing of a centrifugal pump. The results of the calculations are used to predict the impeller/volute interaction and to obtain the unsteady pressure distribution in the impeller and volute casing. The calculated unsteady pressure distribution is used to determine the unsteady blade loading. The calculations at the design point and at two off-design points are carried out with a multiple frame of reference and a sliding mesh technique is applied to consider the impeller/volute interaction. The results obtained show that the flow in the impeller and volute casing is periodically unsteady and confirm the circumferential distortion of the pressure distribution at the impeller outlet and in the volute casing. Due to the interaction between impeller blades and the tongue of the volute casing the flow is characterized by pressure fluctuations, which are strong at the impeller outlet and in the vicinity of the tongue. These pressure fluctuations are died away in the casing as the advancement angle increases. These reduced pressure fluctuations are spread to the discharge nozzle; the pressure fluctuations are also reflected to the impeller inlet and they affect the mass flow rate through the blade passages.

A multi-stage combined heat pump and microwave vacuum drying of green peas

In this work, three-dimensional, unsteady Reynolds-Averaged Navier?Stokes (RANS) equations with standard k-ε turbulence models are solved by employing sliding mesh technique within an entire stage of a multistage diffuser pump to investigate transient flow field and pressure fluctuations due to the interaction between impeller and diffuser vanes. Sliding mesh calculation is carried out as the impeller zones slide (i.e., rotate) relative to diffuser zone along the grid interface in discrete time steps. The complicated time-periodic and spatial-periodic characteristics as well as rotor?stator interaction phenomena inside the pump stage are simulated and analysed to understand dynamic variation of the interior flow field and interference and finally to aim at optimal design.