Hydraulic Performance Of Centrifugal Pump Research Articles

Automatic optimization of centrifugal pump based on adaptive single-objective algorithm and computational fluid dynamics

It is important to reduce carbon emissions caused by the energy consumption of pumps. This study used a centrifugal pump with a specific speed of 89.6 as the research object to improve pump efficiency. The adaptive single-objective method was adopted as the automatic optimization tool with computational fluid dynamics, which includes optimal space-filling experimental design, Kriging response surface, and mixed-integer sequential quadratic programming. Eight geometric parameters from the meridian section and the plan of the impeller and diffuser were chosen as the design variables. The maximum efficiency under the design flow conditions was set as the optimization target. The Spearman correlation coefficient analysis results show that the sensitivity of each variable to efficiency and head. Compared with the original scheme, the optimal scheme showed a 2.75% increase in efficiency and a 1.17 m increase in head under the design flowrate. The internal flow field after optimization was also improved. An external characteristic experiment of the original and optimized pumps was performed to validate the numerical results. This automatic optimization method presents great potential to improve the hydraulic performance of centrifugal pumps at a lower cost.

Effect of Vibration and Noise Measuring Points Distribution on the Sensitivity of Pump Cavitation Diagnosis

Cavitation is an essential factor in the deterioration of the hydraulic performance of centrifugal pumps. The study of cavitation fault diagnosis can help avoid or reduce the damage it causes. The vibration and noise analysis method can predict the incipient cavitation more accurately. In order to improve the accuracy of cavitation fault diagnosis, this paper studies the distribution of vibration and noise measuring points for centrifugal pump cavitation diagnosis. The research object is a centrifugal pump with an inducer and splitter blades. Vibration acceleration sensors and hydrophones were used to collect structural vibration and liquid-borne noise signals at different positions of the pump unit. Root-mean-square (RMS) and fast Fourier transform (FFT) methods were used to construct spectrums of vibration and noise signals with different NPSH and compare the sensitivity of different measuring points to the inception and development of cavitation. In addition, the SST k-ω turbulence model and Zwart cavitation model were used to study the cavitation volume distribution in the pump under different cavitation stages. By setting monitoring points at the impeller outlet, the frequency domain signal distribution of pressure pulsation was studied. The results show that the vibration acceleration measuring points at the pump inlet flange and pump axial position, and liquid-borne noise measuring point at the inlet position, are more sensitive to the diagnosis of cavitation fault. Motor current is also the basis for judging the inception of cavitation. Moreover, as the cavitation intensifies, the dominant frequency signal of the pressure pulsation in the pump is partially shifted.

On the cavitation-induced collapse erosion of a turbofan fuel pump

Cavitation is a challenging flow phenomenon that can adversely affect the hydraulic performance of centrifugal pumps. In this study, numerical investigations were carried out incorporating the Zwart cavitation model derived from Rayleigh–Plesset equation with the Navier–Stokes equations to study a damaged turbofan pump. Pressure fluctuation was analyzed with fast Fourier transform (FFT) in both non-cavitation and cavitation flow fields. The entropy production theory was used to further analyze the positions of vortex cores and energy-loss behaviors inside the pump. The results demonstrate that the numerically predicted positions of vortex cores in high-pressure regions agree well with the erosion positions determined under real working conditions. Herein, through combined analysis of the pressure contours and the vortex-core locations, we demonstrate that the erosion failure of the surface is caused by fatigue failure due to the collapse of cavities at vortex cores. The percentages of different kinds of entropy production rates under different mass flow rates in the whole calculation domain were calculated, and it was found that the impeller suffered the most energy loss. The results of the entropy production analysis can provide guidance for subsequent optimization of turbofan pumps.

Effect of impeller shroud trimming on the hydraulic performance of centrifugal pumps with low and medium specific speeds

The effect of pump impeller modification by a new approach, pump impeller shroud trimming (PIST), on the flow field and pump performance is examined both numerically and experimentally. The primary purpose of this study is to investigate the hydraulic performance of single-phase centrifugal pumps, which are refined by the PIST method, with low and medium specific speeds. In this type of shroud trimming, different trimming sizes are applied only to the shroud plate of the closed impeller, while the geometries (diameters) of the hub and blades remain unchanged. This modification, which increases the clearance between the impeller and casing from the shroud side, causes desirable conditions for pumping fluid containing undissolved gas. Computational fluid dynamics software (ANSYS-CFX) is used to predict the hydraulic performance of centrifugal pumps. Two well-known turbulence models, the renormalization group (RNG) k-ϵ developed model and shear stress transport (SST) k-ω, are used to predict the flow patterns. The computational results are verified through the comparison of experimental and unsteady numerical simulations with steady numerical data. After ensuring the accuracy of the flow-field simulation approach, further numerical analysis is performed for both pumps by changing the impeller shroud diameter. The effects of the geometric changes on the performance curves, efficiency, flow field, pressure distribution inside the pump components and the radial force acting on both pump types are investigated comprehensively. The results show that the shroud trimming reduces the produced head and efficiency at the design points. Examination of the radial force, which is applied on the rotating parts, shows that shroud-trimmed impellers experience higher radial forces than closed impellers in both pump types owing to the lack of a uniform pressure distribution around the impeller outlet. Accordingly, the relevant information obtained is used to modify the existing coefficients to predict the radial forces.

Cavitation control using passive flow control techniques

Passive flow control techniques, and particularly vortex generators have been used successfully in a broad range of aero- and hydrodynamics applications to alter the characteristics of boundary layer separation. This study aims to review how such techniques can mitigate the extent and impact of cavitation in incompressible flows. This review focuses first on vortex generators to characterize key physical principles. It then considers the complete range of passive flow control technologies, including surface conditioning and roughness, geometry modification, grooves, discharge, injection, obstacles, vortex generators, and bubble generators. The passive flow control techniques reviewed typically delay and suppress boundary layer separation by decreasing the pressure gradient at the separation point. The literature also identifies streamwise vortices that result in the transfer of momentum from the free stream to near-wall low energy flow regions. The area of interest concerns hydraulic machinery, whose performance and life span are particularly susceptible to cavitation. The impact on performance includes a reduction in efficiency and fluctuations in discharge pressure and flow, while cavitation can greatly increase wear of bearings, wearing rings, seals, and impeller surfaces due to excessive vibration and surface erosion. In that context, few studies have also shown the positive effects that passive controls can have on the hydraulic performance of centrifugal pumps, such as total head and efficiency. It is conceivable that a new generation of design in hydraulic systems may be possible if simple design features can be conceived to maximize power transfer and minimize losses and cavitation. There are still, however, significant research gaps in understanding a range of impact factors such as manufacturing processes, lifetime, and durability, and essentially how a static design can be optimized to deliver improved performance over a realistic range of operating conditions.

Effect of vaned diffuser clocking position on hydraulic performance and pressure pulsation of centrifugal pump

The clocking position of the vaned diffuser, the circumferential position of the vaned diffuser relative to the volute, has a certain effect on the performance of the centrifugal pump. Therefore, this paper studies the guide vane centrifugal pump from the aspects of pressure pulsation, hydraulic performance, and energy loss. The maximum difference in efficiency is 3.4% under the design flow rate, and the maximum difference in the head coefficient is 4.7%. The hydraulic performance and pressure pulsation present different trends with the increase of the vaned diffuser clock angle. When the hydraulic performance and pressure pulsation are relatively good, the circumferential distance between the tongue and the upstream vaned diffuser blade is 3/4 of the diffuser flow path. In addition, the recommended vaned diffuser installation location may also be suitable for centrifugal pumps of similar construction. The energy loss was visualized using the theory of entropy production. The distributions of energy loss and flow field indicate that the energy loss of impeller and vaned diffuser changes little. The change of the vortex in the tongue and outlet area will cause a significant change in the energy loss of the volute, which is the main reason that the hydraulic performance of the centrifugal pump is affected by the clocking position of the vaned diffuser.

Performance improvement of mixed-flow centrifugal pumps with new impeller shrouds: Numerical and experimental investigations

A new impeller configuration with innovatively-designed shrouds is introduced, and its impact on the pressure head and efficiency of the semi-open centrifugal pump is explored using experimental and numerical approaches. The proposed design includes attaching specific plates called bladelets to a semi-open impeller to limit the secondary flows over the blades resulting in an increase in the pump head and efficiency. Hydraulic performance of a centrifugal pump with three different bladelets at angles of 30°, 60°, and 90° is investigated experimentally, and the results are compared to semi-open and closed impellers. The values of pressure head and efficiency of the proposed centrifugal pump are determined through numerical analysis and then compared to the experimental data in which an acceptable agreement between the results is observed. Both numerical and experimental results show the proposed impeller design promisingly improves the pressure head and efficiency of semi-open centrifugal pumps. Additionally, the flow analysis demonstrates that the impellers with 90° bladelets enhance the hydraulic performance of a semi-open centrifugal pump nearly to a closed impeller configuration. The loss reduction due to the secondary flow and the eddy generation leads to an improvement in the hydraulic performance of the proposed design.

Hydraulic Performance Optimization of Pump Impeller Based on a Joint of Particle Swarm Algorithm and Least-Squares Support Vector Regression

The hydraulic performance of centrifugal pumps is considerably affected by the impeller, and an effective optimization method for centrifugal pump impeller has been developed in the current study. A combination of the least-squares support vector regression machine (LSSVR) and particle swarm optimization algorithm (PSO) is proposed to redesign the impeller and improve the hydraulic performance. In the case study, four key geometric parameters of the impeller, namely, inlet angle, outlet angle, wrap angle and number of blades are selected for optimization. Maximum efficiency and constant head are selected as the optimization targets. During the optimization design, the required database for the LSSVR agent model is designed according to design of experiments. The optimal solution is then found in the established agent model space by the particle swarm algorithm and then verified by computational fluid dynamics. Ultimately, an improved impeller structure with an improved efficiency is provided. Numerical results show that the optimized impeller's efficiency is increased by 1.29% under the condition that the head is essentially unchanged. Then, the reason for the improvement of impeller hydraulic efficiency is explained by the entropy production method. The conclusions show that the PSO-LSSVR method can be used to optimize the pump impeller and achieve higher pump performance.

The influence of blade outlet angle on the performance of centrifugal pump with high specific speed

The blade outlet angle β2 is one of the key design parameters of the centrifugal pump, which has an important influence on the internal flow field and performance of centrifugal pump. In this paper, five impeller models with different blade outlet angles (23°, 25°, 27°, 29° and 31°) were built by Solidworks and CFturbo under the premise of other impeller parameters unchanged, and numerical simulation of high specific speed (ns = 192) pump was carried out in the commercial code ANSYS-CFX. Then the experiment was performed to test the hydraulic performance of centrifugal pump. The results show that the change trend of numerical simulation and experiment is similar, and when the flow rate increases gradually, the hydraulic loss of impeller becomes larger with the increase of blade outlet angle, and the blade outlet angle has obvious influence on the efficiency of centrifugal pump at high flow rate. Besides that, it has small influence on the head, which changes relatively larger at low flow rate than that at high flow rate. And all the research results could provide appropriate reference for designers to select reasonable outlet angle.

Experimental and numerical investigation on the influence of the clocking position on hydraulic performance of a centrifugal pump with guide vane

The investigation of the clocking effect mainly concentrates on turbines and compressors, but seldom in centrifugal pumps. In this paper, using numerical simulation and experiment, the influence of the clocking effect on the hydraulic performance of centrifugal pump with guide vane is studied. Numerical simulations with SST k-w turbulence model were applied to obtain the inner flow field of the test pump. The numerical simulations coincide with the test result, which indicates the accurate of the utilized numerical approach. The results show the clocking positions have an important effect on hydraulic performance of the centrifugal pump with guide vane. The pump demonstrates the higher efficiency and head as the tongue locate between two guide vanes. The hydraulic performance of the volute is a major factor impacting the performance of the centrifugal pump with different clocking positions. However, the clocking position has almost no effect on the performances of the impeller and diffuser. When the guide vane is close to the volute tongue, flow field of volute is more non-uniform, and the energy loss in volute appears to be larger. The results and the method of this paper can provide theoretical reference for the design and installation of guide vane in centrifugal pump.

Numerical optimization for radiated noises of centrifugal pumps in the near-field and far-field based on a novel MLGA-PSO algorithm

As the flow structure in the centrifugal pump is complicated, it always causes serious noises, which has become an important problem in environmental protections. Some works have been completed for optimizing and reducing radiated noises of centrifugal pumps, but optimized algorithms are traditional and easily fall into local extreme values, so that final results are not always the optimal. For overcoming disadvantages of traditional algorithms, this paper proposed a novel MLGA-PSO (Multi-layer Genetic Algorithm-Particle Swarm Optimization) algorithm to make an optimization for noises and hydraulic performance of centrifugal pumps. This algorithm starts from the organizational structure of individuals and separates the global search from the local search, which can not only accelerate the convergence speed, but also avoid reducing the global search ability. The algorithm could effectively overcome the contradiction between global search ability and convergence speed. Inlet diameter, impeller blade outlet width, blade outlet angle and amount of blades are as designed variables. In order to verify advantages of the proposed MLGA-PSO algorithm in global search ability, optimizing speed and stability, GA (Genetic Algorithm), PSO (Particle Swarm Optimization) and GA-PSO (Genetic Algorithm-Particle Swarm Optimization) algorithms are chosen to carry out the compared experiment. Results show that the proposed MLGA-PSO algorithm has higher efficiency and accuracy. Finally, total noises of the optimized noise in the near-field and far-field using MLGA-PSO algorithm are 181 dB and 74 dB, respectively. Total noises in the near-field are reduced by 4.7 %, while those in the far-field are reduced by 16.9 %. It is clearly that the optimized centrifugal pump presents an obvious noise reduction effect.

Design and analysis of a radial diffuser in a single-stage centrifugal pump

ABSTRACTRadial diffusers can improve the flow uniformity in pumps and affect the hydraulic performance of centrifugal pumps directly. The diffusion coefficient d is an important parameter in fluid machinery but it has seldom been used in the diffuser design of single-stage centrifugal pumps. To improve the design method of radial diffuser use in centrifugal pumps, the diffusion coefficient was introduced into the design of radial diffusers based on a single-arc hydraulic design method and it was found that the vane outlet angle, vane outlet thickness and vane number have a significant impact on the design results. A single-stage centrifugal pump with a radial diffuser was selected as the research model. The inner flow was simulated using the commercial computational fluid dynamics (CFD) program CFX and verified by experiment. The results indicate that the head and efficiency of the pump are best when the vane outlet angle is 6°. The flow area decreases and the flow velocity at radial diffuser outlet increase when the outlet thickness is greater than 2 mm. The hydraulic loss is minimum and the head and efficiency are better when the vane number is 8 at different flow rates. So, the optimal range of the diffusion coefficient for the model pump is around 1.6 to 2. The study indicates that it is feasible to design radial diffusers according to the diffusion coefficient.

Mechanism for Onset of Sudden-Rising Head Effect in Centrifugal Pump When Handling Viscous Oils

The “sudden-rising head effect” may be prevalent in the head curve when a centrifugal pump transports highly viscous liquids, but it is not well understood presently. To clarify this effect the hydraulic performance of centrifugal pump when handling water and viscous oils was evaluated numerically by using a CFD code. The “sudden-rising head effect” is confirmed to exist at a higher viscosity and a certain large surface roughness. The viscosity and roughness, which make a transition of boundary layer flow pattern in both the impeller and volute to the hydraulically smooth regime from the fully rough one, are responsible for the effect.

Influence of blade wrap angle on centrifugal pump performance by numerical and experimental study

The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump.

Hydraulic design and performance analysis of low specific speed centrifugal pump

Since low specific speed centrifugal pump with long narrow flow divergent channels has positive slope of head-capacity characteristic curve, low flow rate instability and high flow rate power overload, special events about its hydraulic design are still under study. This paper demonstrates a method for hydraulic design of low specific speed centrifugal pump complex impeller (with splitter blades) which is based on 2D flow theory. In this method, obtain the basic geometry parameters by empirical correlation, adjust impeller profile according to given flow cross section area distribution and wrapping angles distribution, relate the position of splitter blades to slip factor. Based on this method, low specific speed centrifugal pump impellers have been designed using the same design parameters (Head, Capacity, Rotation Speed, etc) with different factors. And 3D turbulent flow fields in design pumps have been solved by using RANS equations with RNG k-epsilon turbulence model. The investigation to the effects of different splitter blades on velocity distributions and pressure distributions along the flow channels and hydraulic performance of centrifugal pumps are presented. The result shows that properly placed splitter blades by choosing suitable design factors will improve the flow in the pump and enhance the hydraulic performance of it.

Hydraulic design and pre-whirl regulation law of inlet guide vane for centrifugal pump

A new hydraulic design method of three-dimensional guide vane for centrifugal pump is proposed on the assumption that the fluid at the outlet of guide vane satisfies the uniform velocity moment condition. The geometry of blade is controlled by the distributed rule of blade angles along the meridional streamline which is described by a fourth-order polynomial. Experiment results demonstrate that the designed guide vane can overcome the drawback of two-dimensional guide vane, enlarge the high efficiency scope and improve the hydraulic performance of centrifugal pump on the off-design operation conditions. In comparison with the performance of the centrifugal pump without inlet guide vane, the peak value of efficiency can be enhanced by 2.13% after the three-dimensional guide vane was being installed. The three-dimensional entire flow field of the centrifugal pump with inlet guide vane is simulated, and the basic principle and mechanism of inlet guide vane pre-whirl regulation are analyzed. The validity of design method has been proved.