Radial Flow Pump Research Articles

Behaviour of cavitation characteristics for various vane leading edge shapes of radial flow pump impeller

Abstract Cavitation is a dynamic phenomenon that degrades hydraulic machines performance. In a pump, the lowest static pressure occurs near the leading edge of the vane, which causes cavitation when it falls below the vapour pressure of the fluid at that prevailing temperature. For the cavitation studies, three different leading-edge profiles of the vane of a low specific speed pump are chosen. Plain, ellipse with semi-minor axis along vane course, and circular are the three leading edge profiles. The radial flow pump impeller was designed through point by point method to obtain the vane course from leading to trailing edge instead of single arc and double arc methods. In this method, smooth transitions of relative and meridional velocities were insisted from inlet to outlet radius. The leading edges of vanes as well as the vane course are cross verified through the coordinate measuring machine for its accuracy. Cavitation tests were performed at various constant flow rates and constant speeds by lowering the water level in the sump (which as 10 m deep from pump centre line) so that the pump transitioned from a non-cavitating to a cavitating state. Cavitation studies revealed that the leading edge has a significant impact on pump performance because the incidence flow angle is disturbed at the inlet. Although the leading-edge profile had little effect on overall performance, but it had a significant effect on cavitation. Detailed cavitation characteristics were arrived for different flow rates, speeds, and the leading edge profiles. It is reconfirmed that affinity law will not hold good for a pump with cavitation. Development of cavitation in impeller channel from the inception were visualised and compared for different leading edge profiles with reference net positive suction head. For all tested flow rates, the pump with a circular leading-edge impeller has a lower Net Positive Suction Head requirement than the pump with an ellipse or plain leading-edge impeller.

Machine Learning-Based Prediction of NPSH, Noise, and Vibration Levels in Radial Pumps Under Cavitation Conditions

Cavitation, a physical phenomenon that detrimentally affects pump performance and reduces pump life, can cause wear on pump elements. Various engineering methods have been developed to identify the initiation and full development of the cavitation process. One such method is the determination of the net positive suction head (NPSH) through a 3% decrease in total head (Hm) at a constant flow rate. In radial pumps, commonly used in agricultural irrigation and industry, cavitation conditions result in a sudden drop in the Hm-Q curve, making it challenging to detect the 3% Hm value drop. This study differs from others in the literature by modelling NPSH, noise, and vibration levels using three machine learning models, specifically artificial neural networks (ANN), support vector machines (SVM), and decision tree regression (DTR). The best-performing model predicts NPSH, noise, and vibration levels corresponding to a 3% decrease in Hm level. The present study determined the NPSH values of a horizontal shaft centrifugal pump at different flow rates and constant operating speed, and the vibration and noise levels were measured for these NPSH values. For each of the NPSH, noise, and vibration levels, ANN, SVM and DTR models were created. The performances of these models were evaluated using criteria such as root mean squared error (RMSE), Mean Absolute Error (MAE) and mean absolute percentage error (MAPE). In addition, Taylor and error box diagrams were created. The ANN model and DTR yielded high accuracy predictions for NPSH values (R2 = 0.86 and R2 = 0.8, respectively). The ANN model provided the best prediction performance for noise and vibration levels. By entering the level of 3% drop in the Hm value of the pump as external data input to the ANN model, NPSH3, noise, and vibration levels were determined. The ANN models can be effectively employed to determine NPSH3, noise, and vibration levels, particularly in radial flow pumps, where detecting 3% reductions in manometric height value is challenging.

A numerical study of clogging analysis in submersible drainage pump

Erosion of material surface due to collisions with solid particles has become a challenge to several engineering fields. Therefore, it is necessary to effectively design radial flow pumps that mitigate the sediment particles’ clogging effect from the system performance. This study aims to analyse and identify the clogging development of a newly designed submersible pump using computational fluid dynamics (CFD) techniques. The particle trajectory was accounted Tabakoff–Grant erosion model for predicting the clogging impact. The experimental pump performance results obtained by this study were used to validate the numerical results of the submersible pump. Pump results revealed a good agreement between the two marks, especially the head of the pump was obtained at a flow rate of 0.165 m3/min. When considering the motor power factor of 0.78, the pump efficiency was found to be 46%, and the test result was well-matched. Also, for combined cavitation-erosion, the performance characteristics of erosion rate density increase linearly. At a flow rate of 0.16 m3/min, the erosion rate density of the original model was more significant than the revised model. Furthermore, compared to the original model significantly reduced the adverse clogging effects on the impeller blades of the revised model.

State of the Art on Two-Phase Non-Miscible Liquid/Gas Flow Transport Analysis in Radial Centrifugal Pumps-Part A: General Considerations on Two-Phase Liquid/Gas Flows in Centrifugal Pumps

Gas–liquid mixtures are present in numerous industrial applications, such as in the process industry, oil production and transport with natural gas, deep-sea extraction, and irrigation. Any pump may have to carry multiphase flows. However, the present document is related to non-miscible liquid/gas flow transport analysis in centrifugal pumps because which topic can be a more challenging task compared with axial and mixed flow machines due to specific body force and buoyancy actions and large density differences between the phases. The present document first introduces the main usual gas–liquid two-phase definitions and simplifications. A dimensional analysis introduces the main flow variables and parameters that are used for pumps. Basic physical aspects of flow motion in an impeller channel are explained, and a rapid description of two-phase flow patterns in radial flow pumps is described. Finally, a review of simplified empirical and semi-empirical analytical models is proposed with their limitations.

Characteristic Curve Prediction of a Commercial Centrifugal Pump Operating as a Turbine Through Numerical Simulations

In this work, we seek to predict the characteristic curve of a commercial centrifugal radial flow pump operating as a turbine, applying a novel methodology based on the state of the art. Initially, the characteristic curve in pump mode is validated through numerical simulations. The results obtained are approximate to the points awarded by the manufacturer, with an error of less than 7% at the best efficiency point. Subsequently, the characteristic curve is generated in turbine mode, obtaining an error of less than 10% respect to mathematical model. Then, velocity and pressure contours are evaluated to validate the fluid dynamic behavior. Finally, the site operating conditions for electricity generation are obtained. With this, it is proposing a methodology for the selection of these turbomachines, applying an economic technology for zones that do not have access to the electrical energy, since it was not found a method that is being applied for its correct election in the hydroelectric generation at low scale.

Investigation of the Matching Relation Between Impeller and Flow Channel of Regenerative Flow Pumps

Abstract As a specific radial flow pump, the regenerative flow pump (RFP) usually has a low efficiency. In this study, in order to explore the matching mechanism, three cases with various matching relations were investigated by the methods of theoretical calculation, computational fluids dynamics (CFD) simulation, and experiment test. The results illustrate that the theoretical prediction, numerical simulation, and experimental data are in good agreement. Furthermore, when the matching relation expressed by a ratio of the channel's and blade's radial length is equal to 1, the geometrical profiles of RFP can well guide the circulation flow into the channel at large radii and into the impeller at small radii, forming intense longitudinal vortex. The steady, strong exchange flow is characterized by the inflow and outflow regions approximately half of the isosurface. The axial vortex motion without apparent flow separation and irregular flow is observed in the impeller, a low velocity annulus exists in the medium radii of the impeller without other distinct velocity clouds, and a low velocity strip and a high velocity annulus in the channel are, respectively, performed along the blade's pressure surface and the channel's outer radii. All of this corresponds to the best pump's performance and the largest efficiency of the impeller and channel. This work promotes a systematical understanding of the matching mechanism between impeller and flow channel in the RFP and could provide some reference for the design and performance optimization for RFP.

Multistage radial flow pump - turbine for compressed air energy storage: experimental analysis and modeling

The increasing development of storage systems connected to electrical networks is stimulated by network management issues related to recent energetic landscape evolutions such as the increasing integration of renewable production sources. Hydro-pneumatic systems seem to offer a clean and cheap energy storage solution among the set of existing storage techniques. The present study analyses an air–water direct contact accumulation system, in closed cycle, using a rotodynamic reversible pump/turbine. The use of a unique energy conversion machine and easy-to-recycle materials could lead to cost-effective, environmentally friendly storage technique with long service life. The paper is focused on the experimental implementation and analysis of the system in a Lab environment, and the modeling of its multi-physic dynamic behavior. To deal with the variable operating conditions of the system, two different real time control strategies of the hydraulic machine were successfully tested. Finally, the global system efficiency is discussed. The efficiency control strategy was achieved with a 31% round trip efficiency and the power control strategy lead to 5% and 23% precision on exchanged power in charge and discharge modes respectively. The multi-physic dynamic model led to a 4% error of turbine mode acceleration prediction showing the interest of such a modeling method for such transient systems.

Overall Performance of a Centrifugal Vaned Diffuser Pump for Different Flow Rates, Experimental and Numerical Comparisons

The article presents the analysis of the interactions between the impeller and the vaned diffuser of a radial flow pump. The tests were carried out on the so-called SHF impeller, coupled with a vaned diffuser, and working with air. The particularity of this machine is that the diffuser design flow rate corresponds to 80% of the impeller one. All experimental works were performed at the Fluid Mechanics Laboratory in ENSAM, Lille, France. Investigations have been made for five different flow rates. Global performances of the machine are evaluated thanks to pressure measurements and averaged velocities obtain with a three hole probe, at nine angular positions at diffuser inlet and outlet just as five radial positions in a middle section of a blade-to-blade passage. A post-processing procedure, based on statistical tools, was applied to the experimental results in order to reach a better understanding of the phenomena. In another approach, a numerical simulation of the flow inside the pump, for eight different relative angular positions of the diffuser relative to the impeller (Frozen rotor) was performed by the STAR-CCM+ software. The experimental results were compared to numerical data obtained with the help of STAR-CCM+ computer code.

A combined numerical/experimental analysis of the flow in the channel of the vaned diffuser of a radial flow pump

The realization and the validation of a simulation in fluid mechanics require an in-depth expertise of the modelling process. However, how could the results be guaranteed if they were not accompanied by experimental measurements? On the other hand experimental measurements show some limitations. For example, PIV measurements are limited to certain viewing planes and rarely near the walls. Moreover, this type of results rarely represents instantaneous results but rather a temporal average of the flows over the measurement time. The use of measurement probes is an intrusive method that can modify the flow and which, as the previous method leads to a mean time result. The purpose of this paper is to analyse the experimental results of the SHF pump which have already been the subject of numerous publications by using the results of the CFD which were made with the computing code star CCM +. This paper includes the comparisons between calculations and measurements inside the diffuser which makes possible to comment on the usefulness and the validity of the stationary measurements despite the unsteady nature of the flow. The analysis highlights the influence of leak rates at the entrance of the diffuser and shows a significant influence of these leak rates on the creation of recirculation swirls that disturb the flow at the entrance of some diffuser channels.

Design and optimization of mixed flow pump impeller blades by varying semi-cone angle

The mixed flow pump is a cross between the axial and radial flow pump. These pumps are used in a large number of applications in modern fields. For the designing of these mixed flow pump impeller blades, a lot number of design parameters are needed to be considered which makes this a tedious task for which fundamentals of turbo-machinery and fluid mechanics are always prerequisites. The semi-cone angle of mixed flow pump impeller blade has a specified range of variations generally between 45o to 60o. From the literature review done related to this topic researchers have considered only a particular semi-cone angle and all the calculations are based on this very same semi-cone angle. By varying this semi-cone angle in the specified range, it can be verified if that affects the designing of the impeller blades for a mixed flow pump. Although a lot of methods are available for designing of mixed flow pump impeller blades like inverse time marching method, the pseudo-stream function method, Fourier expansion singularity method, free vortex method, mean stream line theory method etc. still the optimized design of the mixed flow pump impeller blade has been a cumbersome work. As stated above since all the available research works suggest or propose the blade designs with constant semi-cone angle, here the authors have designed the impeller blades by varying the semi-cone angle in a particular range with regular intervals for a Mixed-Flow pump. Henceforth several relevant impeller blade designs are obtained and optimization is carried out to obtain the optimized design (blade with optimal geometry) of impeller blade.

A study of rotating stall in a vaneless diffuser of radial flow pump

ABSTRACTRotating stall in a vaneless diffuser of radial flow pump is studied. The measurements consist of: (i) unsteady pressure measurements delivered by two microphones; and (ii) nine steady pressure taps mounted in one radial line to measure the pressure recovery in the vaneless diffuser. Spectrum analysis was used to identify and characterize rotating stall. An assumption was made to estimate the losses in the vaneless diffuser to evaluate the effect of the instability development on its performance. The result has shown that the arising of rotating stall has a positive effect on the diffuser performance. Two possible reasons are proposed: (1) a blockage in the diffuser due to the unstable cells which shortens the streamlines and decreased the friction losses along the vaneless diffuser; (2) the topology of rotating stall cells results in the convection of fluid coming from outside part of the pump model to the vaneless diffuser.

Experimental Determination of Cavitation Characteristics of Low Specific Speed Pump using Noise and Vibration

An experimental investigation of the cavitation behaviour of a radial flow pump of metric specific speed 23.62 rpm having different leading edge profiles of the vane is presented. The pump was operated for flow rates from 80 to 120% of the best efficiency point. The measurement included noise and vibration signals apart from the hydraulic parameters. The results exhibited the trends of noise and vibration with respect to percentage of head drops for all operating conditions. It was concluded that the trends were totally different for various flow rates. Hence it is suggested that the criteria to be used for detecting the early cavitation in pump based on noise and vibration signals should be a function of the flow rate. Further, it was found that the range of frequency band for noise and vibration was within 5 kHz with reference to the magnitude of fluctuation. The repeatable predominant frequency of vibration for prediction of cavitation behaviour of this particular pump was established as 0.992 kHz.

Design and Optimization of Mixed Flow Pump Impeller Blades with Hydrostatic Loading and Varying Semi-Cone Angle

Mixed Flow pumps are a combination of both axial and radial flow pumps. In present days they are having a wide range of applications. The impeller blade designing of mixed flow pump has always been a difficult task, the reason being it requires a lot of designing parameter to be considered for successful designing. When compared with radial and axial flow turbo-machines the mixed flow type of turbo-machines always get less importance for these complexities in their designing process. This complexity arises because of the complicated blade and geometry of fluid flow passage. Impeller is considered as one of the most important components in a mixed flow pump for the flow passage. The main motive behind the study of impeller blade design is to cite the reasons for the low hydraulic performance of the pump originally taken into consideration. When the pump is in functioning or operating condition, the rotation of the impeller provides with a geometric shape and the passage of flow gets distorted. It has been observed that all the available designs of the mixed flow pump, impeller blades are designed with a constant semi-cone angle, where as various data books for pump model test signify the fact that the semi-cone angle for these impeller blades can vary a specified range. So it is always an option to verify the fact that if variation of semi-cone angle in this specified range affects the designing parameters or not. From the literature survey it is found that various design methods such as Fourier expansion singularity method, free vortex method, mean stream line theory method, inverse time marching method, the pseudo-stream function method etc., adapted by various researchers, but the design methodology is always a tedious task.Here the authors have proposed the blade designs with a variation of semi-cone at hub.The concepts of Fluid Mechanics and Hydraulic Machines play a vital role in this designing process. Further taking the Hydraulic loading into consideration analysis is done to obtain the possible designs for the impeller blades. Finally optimization is carried out and the optimized design (blade with optimal geometry) is obtained with a varying semi-cone angle taking Hydraulic Loading into consideration.

Prediction of Cavitation Performance of Radial Flow Pumps

Cavitation is a major problem in pump design and operation because this phenomenon may lead to various types of instabilities, including hydraulic performance loss and catastrophic damage to the pump material caused by bubble collapse. Therefore, it is critical to predict the cavitation performance of the pump in the design phase itself. The motivation of this study is to develop a systematic methodology to calculate the cavitation performance of radial flow pumps. In the first step of the present work, a cavitating nozzle flow case for which the bubble dynamic behavior is accurately resolved in literature is studied numerically. Subsequently, the capabilities of three cavitation models, implemented in the commercial code Fluent, are evaluated for three radial flow pumps designed at specific speeds ns = 10.4, 22.4, and 34.4. The numerical results are validated with global quantities based on net positive suction head (NPSH) measurements. The results led to the determination of reasonably accurate NPSH values for the defined range of specific speeds.

Investigations inside a vaned diffuser of a centrifugal pump at low flowrates.

This paper focuses on the unsteady flow behaviour inside the vaned diffuser of a radial flow pump model, operating at partial flowrates (0.387Qi, 0.584Qi and 0.766Qi where Qi is the impeller design flowrate).The effects of the leakage flows are taken into account in the analysis. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation, for several flowrates and different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-holes probe in the same experimental conditions. The unsteady numerical simulations were carried out with Star CCM+ 10.02 code with and without leakage flow. The PIV measurements showed a high unsteadiness at very low flowrate which was confirmed by the numerical calculations. In previous studies it has been shown that the global performances, as the efficiencies are in good agreement between calculations and measurements. In this paper, a joint analysis of measurements and numerical calculations is proposed to improve the understanding of the flow behaviour in a vaned diffuser.

Experimental Study and Theoretical Analysis of the Rotating Stall in a Vaneless Diffuser of Radial Flow Pump

This paper reports an experimental and theoretical study of rotating stall in a vaneless diffuser which is coupled with a radial impeller. The experiments were conducted at 22 flow rates for two rotating speed: 1200rpm and 1800rpm. The measurements have consisted of: i/ unsteady pressure measurements delivered by two microphones flush mounted on the vaneless diffuser, ii/ 9 steady pressure taps mounted in one radial line on the diffuser to measure the pressure recovery in the vaneless diffuser. The stability of each stall mode was also studied by a 2D linear analysis; and the theoretical prediction was compared to experimental observations. The capabilities and limits of such an approach to predict the development of rotating stall have been evaluated. A non-dimensional analysis of the pressure losses at outlet was conducted to evaluate the effect of the instability development on the performance of the diffuser. It has shown that the arising of rotating stall has a positive effect on the diffuser performance.

Model based analysis of the time scales associated to pump start-ups

The paper refers to a non dimensional analysis of the behaviour of a hydraulic system during pump fast start-ups. The system is composed of a radial flow pump and its suction and delivery pipes. It is modelled using the bond graph methodology. The prediction of the model is validated by comparison to experimental results. An analysis of the time evolution of the terms acting on the total pump pressure is proposed. It allows for a decomposition of the start-up into three consecutive periods. The time scales associated with these periods are estimated. The effects of parameters (angular acceleration, final rotation speed, pipe length and resistance) affecting the start-up rapidity are then explored.

Comparisons RANS and URANS numerical results with experiments in a vaned diffuser of a centrifugal pump

The paper presents the analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV (particles image velocimetry) technique, pressure probe traverses and numerical simulations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given rotational speed and various flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. Probe traverses have also been performed using a 3 holes pressure probe from hub to shroud diffuser width at different radial locations in between the two diffuser geometrical throats. The numerical simulations were realized with the two commercial codes: i-Star CCM+ 8.02.011 (RANS (Reynolds Averaged Navier Stokes) turbulence model, frozen rotor and unsteady calculations), ii-CFX 10.0 (turbulence modelled with DES model (Detached Eddy Simulation) combining RANS with LES (Large Eddy Simulation), unsteady calculations). Comparisons between numerical (fully unsteady calculations) and experimental results are presented and discussed for two flow rates. In this respect, the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model are analysed and discussed.

On the Problem of Theoretical Pressure of a Radial-Flow Pump Unit

On the Problem of Theoretical Pressure of a Radial-Flow Pump Unit

Comparisons between numerical calculations and measurements in vaned diffuser of SHF impeller

The paper presents analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV (Particle Image Velocimetry) and pressure probe traverses. PIV measurements have already been performed at middle height inside one diffuser channel passage for a given speed of rotation and various mass flow rates. These results have been already presented in several previous communications. New experiments have been performed using a three-hole pressure probe traverses from hub to shroud diffuser width at different radial locations between the two diffuser geometrical throats. Numerical simulations are also realized with the commercial codes Star CCM+ 7.02.011 and CFX. Frozen rotor and fully unsteady calculations of the whole pump have been performed. Comparisons between numerical results, previous experimental PIV results and new probe traverses one's are presented and discussed for one mass flow rate. In this respect, a first attempt to take into account fluid leakages between the rotating and fixed part of the pump has been checked since it may affect the real flow structure inside the diffuser.