Double-suction Centrifugal Pump Research Articles

Influence of Splitter Blades on the Cavitation Performance of a Double Suction Centrifugal Pump

In order to study the influence of splitter blades on double suction centrifugal pumps two impellers with and without splitter blades were investigated numerically and experimentally. Three-dimensional turbulence simulations with and without full cavitation model were applied to simulate the flow in the two pumps with different impellers. The simulation results agreed with the experiment results and the internal flows were analyzed. Both the numerical and experimental results show that by adding splitter blades the hydraulic performance and the cavitation performance of the pump are improved. The pump efficiency is increased especially at high flow rate condition. The pump high efficiency area is extended dramatically. At the same time since the splitter blades share some part of the blade loading, the pump critical NPSH value is decreased. Obvious pressure increase and velocity decrease at blade suction surface near leading edge were observed in the pump impeller with splitter blades. And the pump cavitation performance was improved consequently.

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.

Investigation on impeller radial force for double-suction centrifugal pump with staggered blade arrangement

In order to find the effects of blade arrangement on impeller radial force, a double-suction centrifugal pump with two impeller configurations is investigated by using CFD approach. The two impeller have same geometry, same blade number, and different blade arrangement. One is staggered impeller in which the blades are arranged with half of blade phase angle staggered in circular direction, another is traditional symmetrical impeller with symmetrical blade arrangement. Results show that the radial force vector diagram for symmetrical impeller is a hexagonal, while it is nearly a circle for staggered impeller. The staggered impeller results no radial force saltation which exists in symmetrical impeller. The blade passing frequency dominates the radial force fluctuation in symmetrical impeller, while this frequency is almost not existed in staggered impeller. The results indicate that staggered blade arrangement can significantly reduce radial force fluctuation in double-suction centrifugal pump.

Numerical investigation of sediment erosion to the impeller in a double-suction centrifugal pump

Based on Euler-Lagrange multiphase flow model and Finnie ductile material erosion model, using phase coupled SIMPLE algorithm, k-e RNG turbulence model and Reynolds Averaged Navier-Stokes (RANS) equation, the solid-liquid two-phase flows in a double-suction centrifugal pump is simulated. The erosion rate and solid mass concentration distribution on the pressure and suction surfaces of blades were obtained in different situations, which include different solid mass concentration (2.17kg/m3, 8.66kg/m3 and 14kg/m3) and different sediment diameter (0.019mm, 0.036mm, and 0.076mm). By comparisons of the test and numerical simulation values, the reliability of numerical calculation method has been verified. The numerical simulation result obtained show that the Finnie ductile material erosion model can accurately predict the erosion rate and erosion areas on the impeller. The erosion rate is increases with solid sediment diameter or solid mass concentration increasing. The main erosion areas on the pressure surface of blades near the blade inlet and outlet and close to the hub, and on the suction surface of blades near the blade inlet and close to the hub. For different sediment diameter or solid mass concentration, the erosion rate on the pressure surface of blades is always greater than that on its suction surface.

Influence of dynamic seals on silt abrasion of the impeller ring in a centrifugal pump

The water flow and movement of silt in a prototype double suction centrifugal pump was simulated using an Euler–Lagrange multiphase flow model. Back-blade and J-groove configurations were adopted to protect the impeller ring from silt abrasion. Four back-blades and four J-grooves were considered. The results show that the relative velocity of water around the impeller ring is too low to move silt out of the spacing between the impeller and the casing, which results in a high silt concentration around the impeller ring. The high silt concentration around the impeller ring is the major contributor to silt abrasion of the ring. Back-blade and J-groove configurations are effective in reducing the silt concentration around the ring but extra friction loss is also introduced and the pump efficiency is decreased. Optimization of the length, position and number of back-blades, and the shape and number of J-grooves, decreases losses in pump efficiency and effectively protects the impeller ring. Case 4 for the back-blade and Case 8 for the J-groove were the most effective configurations in this study.

Evaluation of Flow-Induced Dynamic Stress and Vibration of Volute Casing for a Large-Scale Double-Suction Centrifugal Pump

The transient analysis was carried out to investigate the dynamic stress and vibration of volute casing for a large double-suction centrifugal pump by using the transient fluid-structure interaction theory. The flow pulsations at flow rate ranging from 60% to 100% of the nominal flow rate (Qd) were taken as the boundary conditions for FEM analysis of the pump volute casing structure. The results revealed that, for all operating conditions, the maximum stress located at the volute tongue region, whereas the maximum vibration displacement happened close to the shaft hole region. It was also found that the blade passing frequency and its harmonics were dominant in the variations of dynamic stress and vibration displacement. The amplitude of the dominant frequency for the maximum stress detected at 0.6Qdwas 1.14 times that atQd, lower than the related difference observed for pressure fluctuations (3.23 times). This study provides an effective method to quantify the flow-induced structural dynamic characteristics for a large-scale double-suction pump. It can be used to direct the hydraulic and structural design and stable operation, as well as fatigue life prediction for large-scale pumps.

Cavitation simulation and NPSH prediction of a double suction centrifugal pump

This paper illustrates the flow field numerical analysis of the double-suction centrifugal pump. For the study of the cavitation flow inside the double-suction centrifugal pump, the professional pump/motor simulation software PumpLinx and its Full Cavitation Model has been employed. According to the PumpLinx calculation result and the Cavitation damage index, the cavitation position, level and the cavitation characteristics of the double-suction centrifugal pump has been predicted. For the further objective, the simulation of the flow field in the double-suction centrifugal pump under different inlet conditions has been carried out. By the result analysis, NPSHr has been predicted; the reliability of the results has been verified by comparing with the experimental data. At the same time, this practice can provide guidance for the optimal design of double-suction pump.

Internal flow numerical simulation of double-suction centrifugal pump using DES model

It is a challenging task for the flow simulation for a double-suction centrifugal pump, because the wall effects are strong in this type of pumps. Detached-eddy simulation (DES), referred as a hybrid RANS-LES approach, has emerged recently as a potential compromise between RANS based turbulence models and Large Eddy Simulation. In this approach, the unsteady RANS model is employed in the boundary layer, while the LES treatment is applied to the separated region. In this paper, S-A DES method and SST k−ω DES method are applied to the numerical simulation for the 3D flow in whole passage of a double-suction centrifugal pump. The unsteady flow field including velocity and pressure distributions is obtained. The head and efficiency of the pump are predicted and compared with experimental results. According to the calculated results, S-A DES model is easy to control the partition of the simulation when using near wall grid with 30 < y+<300 control approach. It also has better performance on efficiency and accuracy than SST k − ω DES method. S-A DES method is more suitable for solving the unsteady flow in double-suction centrifugal pump. S-A DES method can capture more flow phenomenon than SST k − ω DES method. In addition, it can accurately predict the power performance under different flow conditions, and can reflect pressure fluctuation characteristics.

Experimental investigation of pressure instabilities affected by cavitation for a double-suction centrifugal pump

Cavitation is a common fault which has a close relationship with pressure instabilities in centrifugal pumps. In order to investigate the hydroacoustic response to cavitation phenomena, a pressure fluctuation experimental is carried out on a double-suction centrifugal pump. Frequency spectrum analysis and time-frequency joint analysis of pressure fluctuations in semi-spiral suction chamber and volute casing are presented based on fast Fourier transform (FFT) and adaptive optimal-kernel time-frequency representation (AOK TFR) methods. The results show that in semi-spiral suction chamber, as the available NPSH value continuously decreases, the frequencies affected by cavitation transfer to a lower frequency range and become relative higher concentrate in time-frequency representation. In volute casing, blade passage frequency (BPF), specific frequency at 1/2 of blade passage frequency (147 Hz) and some frequency bands are well captured. The amplitudes of BPF and BPF/2 are shown to have a reasonable dependence on available NPSH value, though the measuring location relative to volute tongue should be taken into account. Strong pulsation characteristics are observed on relative low available NPSH value conditions. Pressure fluctuation at impeller rotating frequency is shown to be sensitive with cavitation process, of which the amplitude sharply increases at first and then decreases.

Performance Optimization Based on Genetic Algorithm of Double Suction Centrifugal Pump

The object is based on 150S-50 double suction centrifugal pump. At first establish the objective function which is based on the smallest hydraulic losses using the loss extremum method, and build constraint relationship between the parameters of impeller using geometry relationship. In order to get the geometric parameters, it is important to go for optimal calculation for the function using the software called matlab which is based on genetic algorithm. At last modeling, solving the internal flow field and comparing with the previous performance. The result shows that the pump hydraulic efficiency has increased by 0.7% under the normal conditions.

Efficiency and Pressure Pulsation Analysis of a Double Suction Centrifugal Pump with Different Arrangement Impellers

Double suction centrifugal pumps are widely employed in large water supply projects. In the present study, a double suction centrifugal pump with the staggered arrangement impeller in a domestic water supply project has been mapping and modeling, and then the symmetrical arrangement impeller of a double suction centrifugal pump has been designed for comparison. The commercial code was used to investigate the pump efficiency and the time variation of pressure at the zone of volute tongue. This unsteady flow feature was investigated by the large eddy simulation (LES) method with the sliding mesh technology. The analysis indicated that the pump efficiency of the double suction centrifugal pump with staggered arrangement impeller is lower than that with the symmetrical one. The frequency of pressure pulsation at the volute tongue is consistent with the blade passing frequency. The staggered arrangement impeller can reduce the levels of pressure pulsation significantly.

Experimental Investigation of Time-Frequency Characteristics of Pressure Fluctuations in a Double-Suction Centrifugal Pump

Pressure fluctuation is the primary reason for unstable operations of double-suction centrifugal pumps. By using flush mounted pressure transducers in the semispiral suction chamber and the volute casing of a double-suction pump, the pressure fluctuation signals were obtained and recorded at various operating conditions. Spectral analyses were performed on the pressure fluctuation signals in both frequency domain and time-frequency domain based on fast Fourier transform (FFT) and an adaptive optimal-kernel time-frequency representation (AOK TFR). The results show that pressure fluctuations at the impeller rotating frequency and some lower frequencies dominated in the semispiral suction chamber. Pressure fluctuations at the blade passing frequency, the impeller rotating frequency, and their harmonic frequencies were identified in the volute casing. The amplitude of pressure fluctuation at the blade passing frequency significantly increased when the flow rate deviated from the design flow rate. At 107% of the design flow rate, the amplitude increased more than 254% than that at the design flow rate. The time-frequency characteristics of these pressure fluctuations were affected greatly by both operating conditions and measurement locations. At partial flow rates the pulsation had a great irregularity and the amplitudes at the investigated frequencies were much larger than ones at the design flow rate. An asymmetrical pressure fluctuation structure in the volute casing was observed at all flow rates. The pulsation behavior at the blade passing frequency was the most prominent near the volute tongue zone, and the pressure waves propagated in both the radial and circumferential directions.

Effects of Impeller Type on Pressure Fluctuations in Double-suction Centrifugal Pump

The pressure fluctuations in double-suction centrifugal pumps caused by internal flow are the primary sources of operation instability.In order to investigate the effects of impeller types on pressure fluctuations for double-suction centrifugal pumps,five impeller configurations are tested with the same experimental facilities.By arranging pressure transducers on the walls of suction chamber and spiral casing,fluctuating pressure signals are collected at various test flows.The signals in time domain are analyzed by using the FFT method and the frequencies are obtained.Results show that blade passing frequency,rotating frequency and some lower frequencies always exist in double-suction centrifugal pumps.Compared with the traditional impeller,the double suction impeller with bilateral blades staggered can reduce the level of pressure fluctuation.By adjusting the blade outlet shape and increasing the warp angle of the blade near the back shroud side,the amplitude of the pressure fluctuation at blade passing frequency becomes small.The impeller with splitter blades optimizes the flow state,lessens the pressure fluctuation in suction chamber region and improves the characteristic of pressure fluctuations in the spiral casing under small flow rate condition.

Decomposition of Deterministic Unsteadiness in a Centrifugal Turbomachine: Nonlinear Interactions Between the Impeller Flow and Volute for a Double Suction Pump

Modern designs for centrifugal pumps consider flow unsteadiness as a main concern. The averaged impact of blade to blade structures and impeller-tongue or impeller-diffuser interactions is considered relevant to accurately address the machine performance. In this framework, the search for a comprehensive way to explain unsteady patterns would be particularly desirable. In the present paper, an analysis of the deterministic interaction between the impeller flow and both the inlet and outlet volute tongues in a double suction centrifugal pump is carried out. The zero velocity condition imposed in both tongues gives rise to an interaction that, up to the authors’ knowledge, has not yet been studied for this type of pumps. A well-tested numerical model, developed by the authors for previous studies with the same pump, has been exploited to predict deterministic correlations in the interaction region. Therefore, the main goal of this paper becomes the evaluation of the nonuniformities induced by both the inlet and the outlet tongues over the blade to blade distributions within the impeller. As a consequence, fluctuation levels in the blade loadings, derived from deterministic nonuniformities of the inlet tongue, can be provided in the relative frame of reference. The collected data using the numerical model can be further employed to establish modeling issues for deterministic stresses. Since more and more often, it becomes a widespread practice for pump manufacturers to include the analysis of the unsteady flow patterns in the design process, the availability of methodological tools to characterize pure unsteady terms in the early stages may be extremely useful for designers. Comparison of deterministic fluctuations with unresolved turbulence intensities is also available in this study, showing the importance of unsteady mechanisms in the modeling of pumping turbomachines.

The Use of Steady Multi-Phase Position and Unsteady Computational Methods in the Numerical Simulation of Double-Suction Centrifugal Pump

In order to compare the steady multi-phase and unsteady calculation in double-suction centrifugal pump application, this article simulates the internal turbulent flow of the 150S-50 double suction centrifugal pump. Numerical simulation uses realizable turbulence model, simulating with two methods of steady multi-phase and unsteady in 7 cases. Based on the numerical simulation, the head, shaft power, efficiency were calculated, the simulated performance curves of a double suction centrifugal pump is processed. The results show that: The results of unsteady simulation are closer with the experimental data.

양흡입 원심펌프에 있어서 유량변화의 영향에 관한 수치해석적 연구

A numerical simulation is carried out to investigate the effect of flow rate variation and performance characteristics of double-suction centrifugal pump. Two types of pump which have different impeller inlet breadth and curvature of the shroud line consist of six blades impeller and shroud ring. Finite-volume method with structured mesh and k-ω Shear Stress Transport turbulence model was used to guaranty more accurate prediction of turbulent flow in the pump impeller. Total head, power and overall efficiency were calculated to obtain performance characteristics of two types of pump according to the variation of flow rate. From the results, impeller having smooth curve along the shroud line obtained good performance. The lower flow rate, the more circulation region, flow unsteadiness and complicate flow pattern are observed. Complicated internal flow phenomena through impellers such as flow separation, pressure loss, flow unsteadiness and performance are investigated and discussed.

Unsteady Flow Patterns for a Double Suction Centrifugal Pump

The flow in a double suction centrifugal pump is presented in this paper. The static performance of the machine has been obtained in a proper test rig, and the results have been compared with equivalent numerical results from an Unsteady Reynolds Averaged Navier–Stokes Equations (URANS) calculation. In a second step, the numerical results have been exploited to get detailed information about the flow inside the turbomachine. The main goal of the study is, on one hand, the validation of the numerical procedure proposed and, on the other hand, the detailed flow-field analysis for the machine, which points out the possibilities and drawbacks of the pump design. For a double suction machine, the inlet flow is characterized by the existence of a particular geometry that tries to force a uniform flow, at least for the nominal flow rate. On the contrary, at off-design conditions the lack of uniformity produces an unsteady incidence that gives rise to strong hydraulic loading variations. Instantaneous and average pressure fields have been analyzed in this paper to study the evolution of such inlet flow unsteadiness throughout the impeller and the volute. The analysis of both static and dynamic effects on the pump shaft has been carried out from the numerical calculation of the radial forces. The results have shown that the performance of the double suction centrifugal pump is suitable for typical design conditions. The best operation point or nominal flow rate is found to be at φ=0.274, which turns out to produce a specific speed ωS=1.25, well in the range for centrifugal impellers. This operating point is also found to be the one with better efficiency and with better flow characteristics, regarding the axisymmetry of the flow pattern and the fluid forces obtained. However, some particular features produce also interesting results for off-design operating points.

The effect of change in flow rate on the vibration of double-suction centrifugal pumps

This investigation identifies changes in the character of vibration measured on a pump bearing housing resulting from flow below the best efficiency point for industrial double-suction single-stage units with different wear conditions. The paper develops a set of vibration features that will assist in identifying low flow conditions in double-suction pumps.

AN IMPROVED ROTOR MODEL WITH EQUIVALENT DYNAMIC EFFECTS OF THE SUPPORT STRUCTURE

Dynamic effects of the support structure are important in vibration analyses of a rotor. It may well happen in real machines such as centrifugal pumps or turbines operating on a flexible structure. This paper suggests an improved rotor model for including the support effects efficiently into the rotor-bearing system. The support FRFs are used to extract the spring–mass models which have the same dynamic characteristics of the support structure. These regenerated models are directly inserted into the rotor. On the other hand, the impedance coupling method, which is often used in structural vibration problems, is presented to verify the suggested modelling technique. It is based on the FRFs of each substructure and the constraint conditions of interface co-ordinates. To demonstrate the applicability and validity of the analytical procedures, they are applied to the rotor of a double suction centrifugal pump. As a result, they show a good agreement with each other.

Application of spectral analysis techniques to cavitation in centrifugal pumps

ABSTRACT An experimental investigation has been performed to study the inception of cavitation and the effect of entrained air on cavitation in a double suction centrifugal pump. Experiments have been organized to cover off-design flow rates and reduced suction pressures independently so that has been possible to study both the effect of flow rate and suction pressure. Air of known amounts has been entrained from the suction pipe to investigate its effect on the intensity of cavitation and the performance of the pump. Pressure transducers and a FM tape recorder have been used to record the pressure signals acquired from three locations on the set-up. Consequently the data has been digitized and processed by spectral analysis techniques. The power spectra and the RMS values of the pressure signals have been investigated to reveal the inception and extend of cavitation as well as the effect of entrained air. As a result of the study carried out, it has been possible to conclude that spectral analysis techniques are useful tools for the detection of the inception and extend of cavitation and that although having some cushioning effect at the suction side of the pump air entrainment is not an effective method in reducing cavitation damage.