Ling Zhou

Numerical and Experimental Study of Axial Force and Hydraulic Performance in a Deep-Well Centrifugal Pump With Different Impeller Rear Shroud Radius

A multistage deep-well centrifugal pump (DCP) with different impeller rear shroud radius have been investigated both numerically and experimentally under multiconditons, which aims at studying the influence of impeller rear shroud radius to the axial force and pump hydraulic performance. During this study, a two-stage DCP equipped with three different impellers was simulated employing the commercial computational fluid dynamics (CFD) software ANYSY-Fluent to solve the Navier-Stokes equations for three-dimensional steady flow. High-quality structured grids were meshed on the whole computational domain. Test results were acquired by prototype experiments, and then compared with the predicted pump performance and axial force. The static pressure distribution in the pump passage obtained by numerical simulation was analyzed. The results indicated that the appropriate impeller rear shroud radius could improve the pump performance and lower the axial force significantly.

Numerical Prediction and Performance Experiment in a Deep-well Centrifugal Pump with Different Impeller Outlet Width

The existing research of the deep-well centrifugal pump mainly focuses on reduce the manufacturing cost and improve the pump performance, and how to combine above two aspects together is the most difficult and important topic. In this study, the performances of the deep-well centrifugal pump with four different impeller outlet widths are studied by the numerical, theoretical and experimental methods in this paper. Two stages deep-well centrifugal pump equipped with different impellers are simulated employing the commercial CFD software to solve the Navier-Stokes equations for three-dimensional incompressible steady flow. The sensitivity analyses of the grid size and turbulence model have been performed to improve numerical accuracy. The flow field distributions are acquired and compared under the design operating conditions, including the static pressure, turbulence kinetic energy and velocity. The prototype is manufactured and tested to certify the numerical predicted performance. The numerical results of pump performance are higher than the test results, but their change trends have an acceptable agreement with each other. The performance results indicted that the oversize impeller outlet width leads to poor pump performances and increasing shaft power. Changing the performance of deep-well centrifugal pump by alter impeller outlet width is practicable and convenient, which is worth popularizing in the engineering application. The proposed research enhances the theoretical basis of pump design to improve the performance and reduce the manufacturing cost of deep-well centrifugal pump.

Numerical Prediction and Performance Experiment in an Engine Cooling Water Pump with Different Blade Outlet Widths

Changing the blade outlet width is an important method to adjust the performance curves of centrifugal pumps. In this study, three impellers with different blade outlet widths in an engine cooling water pump (ECWP) were numerically simulated based on ANSYS-CFX software. Numerical calculation reliability was validated based on the comparison between simulation results and experimental datum. As the blade outlet width increases, from the performance curves, the investigated ECWP head increases gradually; and the best efficiency point (BEP) offsets to larger flow rate; and the high efficiency region (HER) is becoming larger; and the critical cavitation pressure of the investigated ECWP at BEP increases, which indicates that the cavitation performance at BEP became worse. Compared with the internal flow field, we find vortex appears mainly in the blade passage near the tongue and volute outlet, and the region of the low static pressure is located in the blade inlet suction surface, and impeller inlet and outlet are the regions of high turbulence kinetic energy. Meanwhile, at the same flow rate, with the increase of blade outlet width, the areas of vortex and low static pressure become obvious and bigger.

Numerical simulation and performance analysis of a four-stage centrifugal pump

In this article, performance analysis of a four-stage centrifugal pump is presented and discussed by means of numerical simulation and experimental test methods. Calculation domain in simulation was created based on a four-stage real pump model and meshed with the high density of structured grids according to the grid independence analysis. The numerical simulations under multi-conditions were performed based on standard k-e turbulence and standard wall function. Pump performance curves acquired by numerical simulation and the test are basically coincident; the total head, total power, and efficiency values are similar and changing trend is consistent under the different flow conditions. Flow in first stage is dramatically different compared with other stages. The results present that the four-stage simulation could reflect the real flow more precisely than the two-stage simulation, but also have higher requirements about the computer configuration. To balance the time consuming and numerical accuracy, two-stage simulation is a better choice to predict the pump performance. The results of this study provide the basis and reference for the further improvement of multistage centrifugal pump performance.

Research and Development on the Hydraulic Design System of the Guide Vanes of Multistage Centrifugal Pumps

To improve accuracy and efficiency of the hydraulic design of the guide vanes of the multistage centrifugal pumps, four different-structured guide vanes are investigated, and the design processes of those systems are established. The secondary development platforms of the ObjectArx2000 and the UG/NX OPEN are utilized to develop the hydraulic design systems of the guide vanes. The error triangle method is adopted to calculate the coordinates of the vanes, the profiles of the vanes are constructed by Bezier curves, and then the curves of the flow areas along the flow-path are calculated. Two-dimensional and three-dimensional hydraulic models can be developed by this system.

Effect of a Nonuniform Radial/Axial Tip Clearance on the Flow Field in a Mixed-Flow Pump

The effect of a nonuniform radial/axial tip clearance on the flow field in a mixed-flow pump was studied by numerical simulation of the unsteady flow in the pump with two tip clearance shapes using the standard Reynolds average Navier–Stokes turbulence model, and the equations were solved with the SIMPLEC computational algorithm. The external characteristics, distribution of static pressure, streamline flow of the tip clearance, and vorticity in the impeller are analyzed. The accuracy of numerical simulation was assessed by comparing experimental data with computational results. Although a nonuniform tip clearance leads to a decline in the pump head, which is more pronounced under part-load conditions, the configuration with a nonuniform tip clearance (c = 0.5–1 mm) provides the more uniform velocity and pressure distribution both in the circumferential and axial directions, as the leakage vortex intensity is weakened and its shedding is suppressed. The research results pointed the way for improving the unsteady flow in the mixed-flow pump.

Vibration of Shaft System in the Mixed-Flow Pump Induced by the Rotor-Stator Interaction under Partial Load Conditions

In order to reveal the relationship between rotor-stator interaction-induced unsteady flow and the shaft vibration of the mixed-flow pump, PIV (particle image velocimetry) and axis orbit experiments were carried out synchronously in a mixed-flow pump under designed flow rate (1.0Qdes) and the partial load conditions (0.4Qdes and 0.2Qdes). The distribution of the relative velocity and the vorticity in the rotor-stator interaction region at a certain position of the mixed-flow pump impeller was captured; the axis orbit diagram and the time-domain diagram of shaft system were acquired as well. Besides, the waterfall diagrams of the frequency spectrum under different flow rate conditions were compared. The results show that the backflow and the flow separation phenomenon appear in the rotor-stator interaction flow field under the partial load condition, indicating the flow instability. The medium-frequency exciting force and high-frequency exciting force induced by these unstable flows resulting from the rotor-stator interaction are the main factors to intensify the shaft vibration at the power frequency. The rotor-stator interaction under partial load condition is the main reason for the deterioration of shaft system vibration. The 2X frequency also affects the axis orbit in a low level, while other frequencies have less influence on the shaft vibration. The research results can provide the reference and theory instruction for revealing the operating characteristic of mixed-flow pump when it operates under partial load conditions and to reduce or to prevent the deterioration of vibration of shaft system.

Numerical and experimental investigations of pressure fluctuations in single-channel pumps

To elucidate the characteristics and generation mechanism of pressure fluctuations in single-channel pumps, the unsteady flow in three single-channel pumps with the same impeller equipped with a spiral volute (model 1), a circular volute (model 2), and a torus (model 3) were analyzed by computational fluid dynamics. Experiments on global performance characteristics in the volute of model 1 were performed, and fast response pressure sensors were installed in the spiral volute to measure pressure fluctuations. The results indicate that the numerical results are in good agreement with the experimental results. This study shows that a phase delay exists between different volute monitoring points and the pressure fluctuations in the volute are mainly caused by the potential interactions between the impeller blade and volute wall. Comparison of the pressure fluctuations amplitude of the impeller outlet shows that pressure fluctuation amplitude of model 3 is one order of magnitude lower than those of the others and the wake at the impeller outlet played an important role in pressure fluctuations. The standard deviation of pressure was introduced to describe the pressure fluctuations strength. It shows that the pressure fluctuation strength of the pressure surface is apparently higher than that of the suction surface, and the maximum pressure fluctuation strength in the blade is consistent with the flow separation area, indicating that flow separation is also an important factor for pressure fluctuations in single-channel pumps.

PIV validation of different turbulence models used for numerical simulation of a centrifugal pump diffuser

Purpose Pump is one of the most energy consuming devices widely used as general machinery in industrial applications. Computational Fluid Dynamics (CFD) have been became the main method to study the pump inner flow patterns. It is important to understand the differences and features of the different turbulence models using in turbomachinery. Design/methodology/approach The velocity flow fields in a compact return diffuser under different flow conditions are studied and compared between CFD and PIV measurements. Three turbulence models are used to solve the steady flow filed using high-quality fine structured grids, which are including SST k-w model, Detached-eddy simulation (DES) model and SST k-w model with low-Re corrections. Findings SST k-w model with low-Re correction give a better results comparing to DES and SST k-w model, especially have a good predication about the vortex core position under strong part-loading conditions. Originality/value A special test rig is designed to carry out the 2D Parti...

Computational fluid dynamics and experimental study of inter-stage seal clearance on submersible well pump

In this article, a typical submersible well pump was investigated to study the effects of inter-stage leakage on the inner flow field and external characteristics. The whole flow field of the model pump with different seal clearances was simulated by computational fluid dynamics software. The inter-stage clearance leakage calculated by numerical simulation was compared with the values obtained by the empirical formula. The pressure values were recorded with the arrangement of monitor points in the inter-stage clearance, inlet region, and outlet region, which aimed to study the effects of the change of inter-stage clearance pressure on the pump performance. Meanwhile, a comparative analysis of numerical simulation and performance test of the pump was conducted further. The results showed that the leakage at the small clearance is close to the value calculated using empirical formula. But when the clearance is large, the discrepancy between the simulation result and empirical value inclines. Comparing the numerical results of three kinds of clearance leakage, we found that the clearance leakage could not be ignored in the simulation since it has a large effect on the prediction of pump efficiency and head.