Flow Field Of Pump Research Articles

Impact of Impeller Speed Adjustment Interval on Hemolysis Performance of an Intravascular Micro-Axial Blood Pump.

In recent years, intravascular micro-axial blood pumps have been increasingly used in the treatment of patients with cardiogenic shock. The flow rate of such blood pumps requires adjustment based on the patient's physiological condition. Compared to a stable flow state with fixed rotation speed, adjusting the speed of blood pump impeller to alter flow rate may lead to additional hemolysis. This study aimed at elucidating the relationship between adjusting interval of a blood pump's impeller speed and the hemolysis index. By comparing simulation results with P-Q characteristic curves of the blood pump measured by experiments, the accuracy of the blood pump flow field simulation model was confirmed. In this study, a drainage tube was employed as the device analogous to an intravascular micro-axial blood pump for achieving similar shear stress levels and residence times. The hemolysis finite element prediction method based on a power-law model was validated through hemolysis testing of porcine blood flow through the drainage tube. The validated models were subsequently utilized to investigate the impact of impeller speed adjusting intervals on hemolysis in the blood pump. Compared to steady flow, the results demonstrate that the hemolysis index increased to 6.3% when changing the blood pump flow rate from 2 L/min to 2.5 L/min by adjusting the impeller speed within 0.072 s. An adjustment time of impeller speed longer than 0.072 s can avoid extra hemolysis when adjusting the intravascular micro-axial blood pump flow rate from 2 L/min to 2.5 L/min.

Research on Multi-Objective Optimization of Low Pulsation Unloading Damping Groove of Axial Piston Pump

The high- and low-pressure switching of the axial piston pump is realized by the structure of the valve plate, and the buffer-groove structure on the valve plate is very important to reduce the pressure shock and flow fluctuation. In order to optimize the structural parameters of the buffer tank of the piston pump, the influence of the triangular-groove structure on the outlet pressure–flow characteristics was analyzed, and the low-pulsation buffer-groove structure was designed. First, the relationship between the structure of the triangular buffer tank and the output pressure and flow characteristics of the pump was analyzed theoretically. The Computational Fluid Dynamics (CFD) method was used to calculate the pressure and flow characteristics of the whole pump flow field of the triangular-groove structure, and the influence of the buffer-groove structure parameters on the outlet flow pulsation characteristics was studied. The multi-objective optimization algorithm was used to optimize the structure parameters of the buffer tank, and the optimized structure significantly reduced the outlet pressure–flow pulsation of the piston pump. The results show that, after optimization, the width angle of the front and rear triangular groove is 82.3°, the depth angle is 12.7°, the optimized pressure pulsation rate is 0.3%, and the optimized flow pulsation rate is 13.7%.

The Impact of Rotor Axial Displacement Variation on Simulation Accuracy of Fully Magnetic Levitation Centrifugal Blood Pump.

The rotor axial displacement of the full magnetic levitation blood pump varies with the operating conditions. The effect of rotor axial displacement on simulation results is unclear. This study aimed to evaluate the effect of rotor axial displacement on the predicted blood pump flow field, hydraulic performance, and hemocompatibility through simulation. This study used the CentriMag blood pump as a model, and conducted computational fluid dynamics simulations to assess the impact of rotor displacement. Considering rotor axial displacement leads to opposite results regarding predicted residence time and thrombotic risk compared with not considering rotor axial displacement. Not considering rotor axial displacement leads to deviations in the predicted values, where the effects on the flow field within the blood pump, ratio of secondary flow, and amount of shear stress >150 Pa are significant. The variation in the back clearance of the blood pump caused by the ideal and actual rotor displacements is the main cause of the above phenomena. Given that the rotor axial displacement significantly impacts the simulation accuracy, the effect of rotor axial displacement must be considered in the simulation.

Numerical investigation of particle effect on wear characteristic of centrifugal slurry pump based on CFD-DEM coupling

PurposeIn the process of conveying the solid–liquid two-phase medium of the centrifugal slurry pump, the wear of the flow-passing parts is an important problem affecting its life and safe operation. Therefore, a numerical investigation on the wear characteristics of the centrifugal slurry pump under different particle conditions was conducted.Design/methodology/approachA solid-liquid two-phase model based on CFD-DEM coupling is established and used to analyze the flow field and the wear characteristics of the flow-passing parts with different particle densities, volume fractions and sizes.FindingsParticle conditions will affect the pump flow field. To analyze the pump wear characteristics, the wear distribution, wear value and cumulative force laws of flow-passing parts under different particle conditions are obtained. In each flow-passing part, with the increase of particle density, volume fraction and size, the wear area is concentrated and the wear depth increases. Under different particle conditions, the wear is mainly on the volute chamber and the blade pressure surface, and the tangential cumulative force of flow-passing parts is much larger than the normal cumulative force.Originality/valueAn accurate model and a coupled simulation method for predicting the wear of the slurry pump are obtained, and the wear characteristic law can provide a reference for the design of the slurry pump to reduce friction.

Numerical Analysis of a Novel Rotating Piston Blood Pump Based on CFD

Currently, centrifugal and roller pumps are primarily used as ECMO blood pumps, but their high pressure or high shear force may lead to complications such as hemolysis and platelet activation. Thus, a new blood pump structure was designed by improving the rotating piston pump and applying it to the blood pump. The blood pump flow field was simulated using CFD simulation software to ensure that this pump can produce pulsatile blood flow and guarantee good distribution of flow velocity, pressure, and shear stress in the blood pump. The hemolysis value of the pump was calculated using the Lagrangian particle tracking method. The research results demonstrate that this pump has excellent hemodynamic performance and that most of the shear stresses are less than 100 Pa, as well as a small hemolysis index. Furthermore, the pump combines the advantages of pulsatile and non-pulsatile pumps. This newly developed pump is expected to provide a new direction for ECMO blood pump development and provides important evidence for further optimization and performance evaluation of rotating piston blood pumps.

Development of a Numerical Approach for the CFD Simulation of a Gear Pump under Actual Operating Conditions

The geometric complexity and high-pressure gradients that characterize the design of the flow field of gear pumps make it very difficult to obtain an accurate CFD simulation of the component. Usually, assumptions are made both in terms of geometrical features and physics being included in the analysis. The contact between the teeth, which is a key factor for the correct functioning of these pumps, represents a critical challenge in 3D CFD simulations, mainly due to the intrinsic limits of the dynamic meshing techniques that can hardly effectively manage a zero or close to zero gap point forming during gear rotation. The geometric complexity and high-pressure gradients that characterize the gear pump flow field make a CFD analysis quite difficult, and the contact between the gear teeth is usually avoided, thus being an extremely important feature. In this paper, a gear pump composed of inlet and outlet pipes was considered, and the contact between the gear’s teeth was modeled in two different ways, one where it is effectively implemented and one where it is avoided using distancing and a proper casing modification. Herein, a new methodology is proposed for the application of the dynamic mesh method in the Simcenter STAR-CCM+ environment using an adaptive remeshing technique. The proposed methodology is compared with the alternative overset meshing method available in the software. The new meshing method is implemented using a user-routing that reproduces the real geometry of the gears while rotating during the pump operation, with teeth contact included. The routine is optimized in order to limit the additional computation and time needed for the remeshing process. The results that can be obtained using the two meshing approaches for the gear pump are compared in terms of computational effort and the accuracy of the results. The two methods showed opposite results in almost all the reported results, with the overset being more precise in the radial pressure evaluation and the dynamic being more reliable in the cavitation/aeration extension cloud.

Numerical Analysis and Experimental Study of Unsteady Flow Characteristics in an Ultra-Low Specific Speed Centrifugal Pump

Low specific speed centrifugal pumps are widely used in urban water supply, agricultural irrigation, petrochemical and other fields due to their small flow rate and high head. Therefore, the study of unsteady flow characteristics plays a vital role in its safe and stable operation. In this paper, numerical simulation and experimental methods are used to explore the unsteady performance of the pump. The results show that the fluctuations of the external characteristic such as head, shaft power and energy loss are due to the periodic disturbance of the flow field of pump. But the transient performance of shaft power and head shows different changing trends due to different influencing factors. In this paper, the transient process of hydraulic performance is divided into three stages according to the causes and characteristics of hydraulic fluctuations. Most of the hydraulic losses occur inside the impeller, so the impeller flow field determines the level of time average hydraulic performance. Although the hydraulic loss of the spiral case is small, it is greatly affected by the rotor-stator interaction, which affects the strength of the hydraulic fluctuation. This study is of great significance to the mechanism of rotor-stator interaction and the stable operation of low specific speed centrifugal pumps.

Unsteady flow characteristics of an AFP based on energy loss and vortex identification under rotating stall condition

Rotating stall, as a typical unsteady flow phenomenon in the axial flow pump (AFP), might easily result in a sharp decline in the performance of the AFP, thereby affecting the safe and stable operation of the pump. To better understand the loss mechanism of flow in the AFP, this paper numerically computes the unsteady flow of an AFP with guide vanes under a variety of working conditions. Unstable flow characteristics such as flow separation, typical vortex structure and flow loss of the pump under varied working conditions are analyzed using energy loss and vortex identification methods. The analysis of boundary vorticity flow (BVF) of the pump flow field shows that unstable flow can be observed in the BVF positive peak area on the blade surface, affecting the work of the impeller. Meanwhile, there is also unsteady flow from the trailing edge of the blade to the pressure surface of the adjacent blade near the impeller hub. It is gradually enlarged to block the impeller channel as the stall aggravates, causing the formation of a ‘saddle zone’ in the AFP. The guide vane and the impeller are core areas of energy loss within the AFP. On this basis, large numbers of vortex inside the impeller and the impact of unstable flow on the blades are the main contributors to the energy loss of the impeller.

Numerical and Experimental Study on the Flow-Induced Noise Characteristics of High-Speed Centrifugal Pumps

The development of low-noise pumps is essential to design quiet fluid delivery systems. Due to the complicated internal flow, the flow-induced noise characteristics of high-speed centrifugal pumps have not been well understood. Taking engine cooling pumps as an example model, experimental measurements are performed in a semi-anechoic room and a CFD/CFA calculation method is proposed to study the fluid-borne noise and radiated noise characteristics. In the speed range of 5000–6750 r/min, both the pump head and the dimensionless radiated noise characteristics conform to similar laws, and the highest efficiency point pump presents the lowest noise level. Consistent with the experimental results, the predicted radiated noise of the model pump presents dipole characteristics at the required flow rate condition. Moreover, the spectrum of fluid borne noise at pump outlet shows broadband characteristics but with obvious discrete peaks, which are not only related to the fluid pressure pulsation characteristics (6f0 and the multiple) at the low-frequency region, but also to the frequency of the structural mode (3000–6000 Hz region). Rotor-stator interaction of the pump flow field between the impeller and volute is the main reason of flow-induced noise; unstable flow also contributes to the broadband components in the noise spectrum.

Cavitation performance of multistage slurry pump in deep-sea mining

Liquid–gas and liquid–solid phase relationships are established in this study using the theories of cavitation nucleation and solid–liquid two-phase flow, respectively. The relationship between gas and solid phases is then derived, and the effect of solid phase parameter characteristics on the cavitation characteristics of the slurry-conveying slurry in the pump is analyzed. The influence law of particle concentration and speed on the airing performance of two-stage slurry pumps is studied on the basis of computational fluid mechanics. Results show that the cavitation phenomenon reduces the overall pressure of the flow field of deep-sea mining slurry pump. The lowest pressure area is the area of airing development at the entrance of the first-stage impeller blade. The cavitation of the mineral pulp pump becomes evident, and air bubbles rapidly spread over the outlet as the solid phrase particle grows in size. Moreover, solid phase concentration heightens the cavitation of the slurry pump. The cavitation in the pump gradually intensifies as the speed of the slurry pump increases, and a large area of air bubbles sharply forms and disturbs the flow field of the pump when the speed reaches 2000 r/min. In addition, the vortex increases, and the jet phenomenon becomes serious. A comprehensive analysis of the cavitation characteristics of the slurry pump is obtained at the following speed, solid phase volume concentration, and solid phase particle size: n = 1450 r/min, C = 5.3% and d = 20 mm, respectively.

Transient characteristics of a centrifugal pump at rapid startup

Experimental and CFD studies were carried out on transient behaviors of a centrifugal pump during rapid startup. Relationship between the transient characteristics and a flow field in the centrifugal pump was investigated during the transient period of the centrifugal pump. Instantaneous pressure and flow rate were measured at suction and discharge ports with rotational speed during the transient operations. The pump suction and delivery pressures were measured using strain gauge type pressure transducers. And unsteady flow rate was calculated from pressure difference between two pressure measurement points in the straight pipe of the pump suction and discharge lines using the difference of inertia force. Transient characteristics during transient period were related to the time-dependent flow field, which was investigated using CFD, in the pump. As a result of the present study, it was shown that the transient characteristics in experiments were larger than a quasi-steady change at early transient stage, and then that characteristics gradually approaches to the quasi-steady change. And from CFD results, it was shown that the flow field in pump at this early transient stage did not develop enough compared with that at the quasi-steady change. Moreover, from the experimental and CFD results, the deviation of dynamic operation loci from the quasi-steady change during pump startup period occurs at a large flow rate acceleration. The reason is thought to be due to that the flow field at large flow rate change cannot develop compared with that at the quasi-steady change.

Analysis on the effect of variable guide vane numbers on the performance of pump as turbine

To study the effects of different guide vane numbers on the unsteady performance of pump as turbine based on the Navier–Stokes equation and standard k-epsilon turbulence model, computation fluid dynamics technology was used to simulate the flow field in pump as turbine. The turbulent kinetic energy, unsteady radial forces, and power losses were also clarified. The results show that for turbines with a guide vane, the distribution of turbulent kinetic energy is more uniform than before, and the radial force vector distribution is more symmetrical within four quadrants. The time-domain distribution of radial force is more periodic, the number of fluctuation periods is equal to the guide vane numbers, and the dominant frequency of the radial force is equal to the blade frequency. For different guide vane numbers, the effects on the unsteady performance of pump as turbine are different. When the guide vane number is equal to 9, the distribution of turbulence kinetic energy is optimal. In addition, at an optimal flow rate, both the time domains of the radial force and the power losses of the impeller are minimal, so to the geometric parameters of the hydraulic turbine are definite, the optimal guide vane number exists.

Numerical computation of the flow noise for the centrifugal pump with considering the impeller outlet width

In order to study the effects of the impeller outlet width on the flow noise of the centrifugal pump, a centrifugal pump is applied in the paper as the research object. Geometric parameters of the pump and impeller are constant, and BEM (Boundary Element Method) and experimental method are adopted to analyze noises when the impeller outlet width is 8 mm, 10 mm, 12 mm and 14 mm, respectively. Firstly, Large-eddy simulation method is applied to compute the transient flow field of the centrifugal pump. Larger pressures and flow velocity of the centrifugal pump mainly are at the edge of the impeller. When the fluid flows from the centrifugal pump, there are two obvious separation vortexes at the outlet of the centrifugal pump. The flow velocity distribution of the centrifugal pump in the horizontal plane is basically symmetric. Based on modal analysis and the transient flow field of the pump, BEM is adopted to compute the noise in the centrifugal pump caused by the unsteady flow, and experiments are also conducted for verification. Based on the above analysis, the noise in the interior and exterior field of the centrifugal pump is computed, and the effects of the impeller outlet width on the noise of the centrifugal pump are then studied. As shown from the result, the radiation sound power at the characteristic frequency increases with the increase of the impeller outlet width. With a reasonable range, the impeller outlet width makes the sound pressure level (SPL) in the interior and external field of various flow conditions be smaller. Considering the energy performance and flow field noises of the centrifugal pump, the pump has the optimal comprehensive performance at the impeller outlet width of 10 mm. The research results can be applied to provide a reference for the optimization design of the centrifugal pump with low vibration and noise.

Analysis of Flow Field and Pumping Performance for a Valveless Piezoelectric Pump with a Hemisphere-segment Group

The pumping and mixing performance of a valveless piezoelectric pump were proposed and studied. A hemisphere-segment group that was fixed in the pump played the role of a valve. Based on the theoretical analysis of the pumping performance, the changes of the fluid velocity field, pressure difference, the coefficient of resistance and flow rate were simulated with FLUENT. Simulation results revealed the relationships among the pressure field, flow rates, row and column numbers, and row and column intervals of the hemisphere-segment group. The simulation results indicated that increasing row and column numbers, increasing row intervals, and decreasing column intervals could all increase the flow resistance difference in pump flow field and thus increased the flow rate. It was also found that the pumping effect was significantly improved by increasing row number than increasing column number; the increasing of row and column intervals could increase the size and strength of the vortex, and then improve the mixing and stirring performance of this pump. Finally, simulation results were tested and verified through pump flow-rate experiments.

Lattice Boltzmann Simulation of the Flow Field in Pump Intakes—A New Approach

In recent years, lattice Boltzmann methods (LBMs) have become popular for solving fluid flow problems of engineering interest. Reasons for this popularity are due to the advantages of this method, which are, for example, the simplicity to handle complex geometries and the high efficiency in calculating transient flows. For the operational reliability and efficiency of pumps and pump systems, the incoming flow conditions are crucial. Since the efficiency and reliability requirements of pumps are rising and must be guaranteed by the pump and plant manufacturer, the flow conditions in pump intakes need to be evaluated during plant design. Recent trends show that pump intakes are built more and more compact, what makes the flow in the intake even more complex and holds a higher risk for unacceptable pump inflow conditions. In this contribution, a numerical scheme for the simulation of pump intake flows based on a lattice Boltzmann-large eddy simulation (LES) approach is presented and the ability of the method to capture the flow phenomena in intake flows is analyzed. Special attention is turned to the potential of the numerical scheme to reproduce the transient vortex behavior of intake flows, which results in a very complex flow structure and is challenging to model numerically.

Numerical Simulation of the Influence of Gear Rotation Speed on the Gear Pump Flow Field

Gear pump has simple structure, long service life, strong self-priming capacity, high working reliability and other characteristics, which is widely used in various kinds of mechanical equipment. In order to study the influence of gear rotational speed on the internal fluid flow field change rule, the computational fluid dynamics software Fluent was used to simulate the gear pump flow field, while dynamic grid technique was carried on the numerical simulation of the gear pump under different rotation speed, and flow field characteristics were analysed. The results showed that with the increase of gear rotation speed, the area of pump fluid velocity mutation decreased, the area of pressure mutation reduced, and the larger volume of fluid closed to balance.

CFD Numerical Simulation of the Complex Turbulent Flow Field in an Axial-Flow Water Pump

Further optimal design of an axial-flow water pump calls for a thorough recognition of the characteristics of the complex turbulent flow field in the pump, which is however extremely difficult to be measured using the up-to-date experimental techniques. In this study, a numerical simulation procedure based on computational fluid dynamics (CFD) was elaborated in order to obtain the fully three-dimensional unsteady turbulent flow field in an axial-flow water pump. The shear stress transport (SST) k-ω model was employed in the CFD calculation to study the unsteady internal flow of the axial-flow pump. Upon the numerical simulation results, the characteristics of the velocity field and pressure field inside the impeller region were discussed in detail. The established model procedure in this study may provide guidance to the numerical simulations of turbomachines during the design phase or the investigation of flow and pressure field characteristics and performance. The presented information can be of reference value in further optimal design of the axial-flow pump.

Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Flow Field Analysis

For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, the iteration convergence problem caused by complex internal structure and high rotational speed of pump is always a problem for numeral simulation researchers. To solve this problem, the combination of three measures of dynamic underrelaxation factor adjustment, step method, and rotational velocity control means according to residual curves trends of operating parameters was used to improve the numerical convergence. Numeral simulation of 3D turbulent flow in a low specific speed solid-liquid centrifugal pump was performed, and the results showed that the improved solution strategy is greatly helpful to the numerical convergence. Moreover, the 3D turbulent flow fields in pumps have been simulated for the bottom ash-particles with the volume fraction of 10%, 20%, and 30% at the same particle diameter of 0.1 mm. The two-phase calculation results are compared with those of single-phase clean water flow. The calculated results gave the main region of the abrasion of the impeller and volute casing and improve the hydraulic design of the impeller in order to decrease the abrasion and increase the service life of the pump.

Suppression of secondary flows in a double suction centrifugal pump with different loading distributions

Secondary flow is one of the main reasons for low efficiency in double suction centrifugal pump. In a 3-D inverse design method, the pump blade could be designed by a specified loading distribution to control the flow field in pump. In order to study the influence of loading distribution on secondary flow of a double suction centrifugal pump, the external characteristics and the internal flow field of the pump with three kinds of loading distributions are analysed by using CFD approach. According to the simulation results, it is found that the form of fore-loading distribution at shroud and aft-loading distribution at hub could improve the optimal efficiency and broaden the high efficiency area of the pump. Furthermore, the secondary flow in impeller exit region and volute could be significantly suppressed if the slope of loading distribution curve of shroud is set to be −0.7.

The simulation of multiphase flow field in implantable blood pump and analysis of hemolytic capability

The numerical simulation of the axial flow impeller blood pump NIVADIII is carried out by using a CFD multiphase flow model. The hydrodynamic performance of the pump and the flow field in the pump are analyzed, and the shear stress distribution is obtained. A hemolytic prediction model based on the shear stress is built based on the calculation results, and it can be used for qua- ntitative predictions of the hemolytic behavior of a blood pump. Hemolysis tests in vitro were performed 6 times with fresh bovine blood. At each time, the flow of the pump NIVADIII is 5 L/min and the outflow tract pressure is 100 mmHg. According to the tests, the plasma free hemoglobin (FHB) content and the hematocrit (HCT) are measured after 0 s, 0.5 s, 1 s, 1.5 s, …4 s. At the end of each experiment Normal Index of Hemolysis (NIH) of NIVADIII is calculated. The average of NIH is 0.0055 g/100L, almost identical with that obtained from the hemolytic prediction model. This method can be applied in the selection stage of a blood pump.