Double-suction Centrifugal Pump Research Articles

Performance improvement of a double-suction centrifugal pump for water supply system based on energy loss analysis and cavitation behaviour prediction

ABSTRACT To gain a comprehensive understanding of the energy dissipation of a double-suction pump, analysing the energy loss of its various components is necessary. However, the liquid temperature in the double-suction pump remains almost constant, using the entropy production or dissipation method to evaluate energy loss is difficult. The traditional analysis method based on pressure drop cannot quantify the internal energy changes in each component. To solve this problem, a pressure energy loss evaluation approach is developed on the basis of the pressure drop theoretical analysis and numerical prediction, and the effects of cavitation on the energy loss are investigated. The structure of the volute casing is improved to enhance the performance based on energy loss analysis and cavitation behaviour prediction. The results show that the energy loss efficiencies for the suction casing, impeller, and volute casing are 0.55, 4.6, and 5%, respectively, at the design flow rate. The proportion of energy loss in the impeller and volute casing increased with a decrease in NPSHa. The RNG k–ε and k–ω turbulence models are chosen for the numerical simulation, and the numerically predicted results are verified experimentally.

Numerical investigation of vortex structure and unsteady evolution in multi-stage double-suction centrifugal pump

Multi-stage double-suction centrifugal pump is constructed to handle situations with large flow rates and high head. However, due to the complex internal flow structure, the pump can experience hydraulic excitation caused by the presence of numerous vortical structures. Such excitation can lead to unstable pump operation and increased energy losses. In this study, we aim to analyze the multi-stage double-suction centrifugal pump by combining numerical simulation using detached eddy simulation (DES) and experiments to accurately capture the vortical structure and elucidate the mechanism of the rotor-stator interaction (RSI) formation. The results indicate that the omega vortex identification method can accurately capture the vortex structure in the pump, irrespective of the threshold value and without the influence of wall shear layers. Additionally, based on this identification method, we have analyzed the unsteady evolution characteristics of the vortex structure in the pump. Specifically, we have focused on the shedding of wake vortices and their collision with the tongue. The findings suggest that the rotor-stator interaction primarily arises from the periodic shedding of wake vortices near the impeller outlet. In summary, this study provides valuable insights into the flow dynamics of multi-stage turbomachines.

Visual experimental study on cavitation performance of double-suction centrifugal pump

In this paper, the cavitation test results of double-suction centrifugal pump are further “visualized” and verified by using high-speed photography technology to photograph the development process and flow field of impeller inlet cavitation. By optimizing the impeller inlet parameters, the key geometric factors affecting the cavitation performance of the double suction pump were determined. The experimental results show that by optimizing the inlet parameters of the double-suction pump and combining the visualization test verification of cavitation, on the basis of ensuring the wide and efficient efficiency of the double-suction centrifugal pump, the optimization scheme of the experimental design greatly improves its cavitation performance, and provides a new design idea and reference for guiding the development and design of products with high cavitation performance.

The influence of ring clearance on the performance of a double-suction centrifugal pump

Due to the complex structure of a double-suction pump's suction chamber, the flow in the pump's cavity is often ignored in numerical simulations because of difficulties in structured hexahedral meshing. However, the wear ring clearance interlinking the pump chamber leads the fluid at the impeller inlet directly to the impeller area. This significantly impacts the pump's internal flow field, so the influence of the clearance on the internal flow of a double-suction pump cannot be ignored. This paper develops four three-dimensional double-suction pump models with different wear ring clearances to investigate their influence on pump performance, and structured hexahedral meshes were used for all the computational domains. The clearances varied from 0.2 to 0.5 mm in 0.1 mm increments. The influences of the clearance on the energy loss, external characteristics, and internal flow field distribution of the pump were simulated via a verified computational fluid dynamics method. The results show that the wear ring leakage decreases with the flow rate and increases with wear ring clearance. The increase in backflow leads to an internal flow disorder inside the impeller, resulting in a decreased head and efficiency. Energy loss is mainly caused by increasing the turbulence entropy production with an increasing wear ring clearance. Also, the low-pressure region in the pump cavity expands to the volute with increasing clearance, and the impeller outlet pressure decreases. This study's research on wear ring clearance provides a reference for the design and application of double-suction centrifugal pumps.

Implementation of a Reduced Order Model for rotating seal annular leakage flow inside a centrifugal pump

Sustainability and net zero emissions targets drive the importance of turbomachinery design, optimisation, and efficient operation in modern geoenergy systems. To further enable integration of advanced large-scale technologies, accurate and resource-efficient simulations of complex equipment and systems need to be completed readily. An approach to simulate internal leakage flows of centrifugal pumps is presented, an important factor that influences equipment operation efficiency.One significant challenge when internal leakage flow is investigated is achieving sufficient simulation detail in the flow regions separating rotating and stationary components where close-running clearances are present. Computational fluid dynamics (CFD) meshes typically require excessively fine resolutions of node points in these situations for accuracy. For example, the typical annular suction wear ring clearance ranges between 0.1–0.5 mm, whilst impeller diameters and other geometric properties have length scales from 600–1200 mm or even larger.A reduced order model (ROM) of an annular seal configuration was developed that allows for analytical calculation of the leakage flow by implementing user scripting in the CFD solver setup. The ROM implementation has a low symbol count and does not require any type of logic and/or recursive and iterative functionality. Thus, fine and resource-intensive meshing can be robustly eliminated and replaced by a sufficiently detailed ROM that contributes leakage flow effects to the overall simulation.Leakage flow through the suction wear ring of a high differential head (ΔH), high flow rate, double suction centrifugal pump with water as working fluid was used as a case study for ROM development. The calibrated model was verified against a commercial fluid dynamics software package and achieved a level of precision of 2.4% with σ=0.0118 in a wide operating range of 10m⩽ΔH⩽350m and fluid temperature (T) of 283.15K⩽T⩽353.15K.The leakage flow calculated by the ROM was proven to be accurate and therefore capable of accounting for a range of pressure heads, incorporating surface roughness effects and temperature variations, and adaptable for various fluids. Guidance for the implementation of the ROM in the Ansys CFX solver environment is also provided to aid future work.

Investigation on energy dissipation mechanism in a double-suction centrifugal pump based on Rortex and enstrophy

Since double-suction centrifugal pumps consume quantities of energy, revealing critical factors for energy dissipation is helpful for energy-saving design. This study aims to investigate the relationship between energy dissipation and vortex based on Rortex method in a double-suction centrifugal pump. Detached eddy simulation was applied to obtain the flow field. Enstrophy was used to present the strength of the local rigid vortex and shear. The results indicate that the local shear dominates energy dissipation in the pump. Owing to jet flows, the energy loss on blade leading edges (LE) and trailing edges (TE) were 102-103 times that of the middle region at 0.4Qd and ten times at 1.4Qd. The energy dissipation on pressure sides (PS) was ten times greater than that on suction sides (SS) at the TE, while flow separation at the middle of SS caused by wake flow increased energy dissipation to nearly ten times that of PS. Jet-wake flow near volute inlet was the dominant factor for energy dissipation at part-load, while separation flows in volute discharge was more significant at overload. The induced high local shear strength was responsible for energy dissipation. Therefore, reducing local shear is a potential energy-saving approach in pumps.

Investigation of energy dissipation mechanism and the influence of vortical structures in a high-power double-suction centrifugal pump

The extensive applications of double-suction centrifugal pumps consume a considerable amount of energy. It is urgent to reveal the detailed energy dissipation generation and find the critical factor for pump performance enhancement. In this investigation, the internal flow field of a double-suction centrifugal pump was obtained by solving the Reynolds averaged Navier–Stokes equations. The entropy production method was utilized to calculate and visualize irreversible energy dissipation. The Omega vortex method was utilized to identify vortical structures and determine the temporal and spatial relationship between entropy production and vortices. The results indicate that the entropy production in the main flow regions was critical in hydraulic loss, accounting for 54%–71% of the loss, and turbulent dissipation in the main flow regions of the impeller and volute casing dominated the variation of pump efficiency. The near-wall entropy production in the impeller positively correlated with the flow rate, but the impact was insignificant in volute casing. Although the suction chamber contributed minimally to the hydraulic loss, the backflows at the impeller inlet were relieved near the ribs, and the dissipation at the impeller inlet was reduced when the blade leading edges passed the ribs. By adopting Omega vortex identification, wake vortices, separation vortices, and their interactions were determined to correlate strongly with hydraulic loss in volute channels and near cutwaters. Furthermore, these vortices were influenced by the back flows from the impeller sidewall gaps. Additionally, this study can also provide the foundational principles for the optimal design of this type of pump.

Improvement Design of a Two-Stage Double-Suction Centrifugal Pump for Wide-Range Efficiency Enhancement

Two-stage double-suction centrifugal pumps have both a large flow and high head. However, due to the complexity of their flow passage components, efficiency has always been a major problem, and the corresponding head is also prone to insufficiency. In this study, an improved design for a two-stage double-suction centrifugal pump unit with a specific speed of 25.9 was developed with the help of a computer. The computational fluid dynamics (CFD) method was used to evaluate the performance and loss of the unit in the process of improvement. The unit’s inlet division section, two semi-spiral suction chambers, two impellers for the first stage, two inter-stage channels, a double-suction impeller for the second stage, and the volute were able to be improved. Through a total of 39 improvements, the efficiency under multiple working conditions was comprehensively improved, and the head had a reasonable margin in meeting the requirements. After the improvements, the flow pattern in the inter-stage channel and volume were significantly improved through the check of the streamline. This research successfully improved the performance of a two-stage double-suction centrifugal pump unit, and it has significant engineering value.

Analysis of Inner Flow in a Multi-Stage Double-Suction Centrifugal Pump Using the Detached Eddy Simulation Method

In order to analyze the inner flow in a multi-stage double-suction centrifugal pump, which is regarded as a common way of knowing the current characteristics of the pump and as the basis of optimization for better performance, a numerical simulation considering the velocity field distribution characteristics and pressure fluctuation propagation law using the detached eddy simulation method was conducted. Additionally, the principle of entropy generation was put to use to quantify and compare the energy loss of different components. The results reveal that the existence of unstable flow structures in the first-stage impeller and a large number of vortical structures in the back-channel result in reduced operational efficiency of the pump. Furthermore, the pressure fluctuation intensity reaches its maximum with 0.15 at the blade trailing edge, which propagates to the tongue region of the forward flow channel and the double-volute under the low rates condition. Additionally, the main frequency of the monitoring points in the inter-stage flow channel and volute is basically located at a frequency of 198.667 Hz, which is twice the blade frequency. Consequently, the wall entropy production accounting for nearly 25% cannot be ignored and that the loss mainly occurs in the double-volute and the inter-stage flow channel due to the occurrence of irregular flow in the above components with more than 50%. The outcomes of this research present a valuable point of reference for the optimization of structural design in multistage turbomachines with various applications.

Energy efficiency analysis of double suction centrifugal pumps with new impeller geometry

The development of energy saving determines the importance of improving the efficiency of equipment that uses most of the energy consumed. Pumping equipment is one of the most significant consumers of electrical energy. Thus, the drive of pumps (mainly centrifugal pumps) at some CHPPs consumes up to 10 % of the total energy produced at the plant [1]. In general, the total share of consumption of pumping equipment operated in industry, according to various estimates, is from 15 to 25 % of all generated electricity. In this paper, a new impeller configuration (with variable blade curvature) for double suction centrifugal pumps with higher efficiency was proposed. The head and efficiency of centrifugal pump with different vane grids were compared. The main conclusions are that the static pressure and relative velocity have increased in the modernised impeller, leading to an increase in hydraulic and overall efficiency, the kinetic energy of turbulence has less pulsation. the operating point of the pump has shifted. In spite of the fact that the average integral efficiency has increased in the modified pump, the operating point of the pump is shifted to the side of decreasing flow by 1.5%. The theory of the variable curvature vane system was verified by computational methods.

Energy Characteristics and Dissipation Mechanism in a High-Power Circulation Double-Suction Centrifugal Pump

Energy Characteristics and Dissipation Mechanism in a High-Power Circulation Double-Suction Centrifugal Pump

Unsteady Study on the Influence of the Angle of Attack of the Blade on the Stall of the Impeller of the Double-Suction Centrifugal Pump

In order to clearly show the influence on the rotating stall of the impeller of a double-suction centrifugal pump, this paper, using the numerical simulation method of Shear Stress Transform (SST), analyzes the effects of different inlet angles of the blade on hydraulic performance, internal flow field and pressure pulsation in the impeller. The results show that the small angle of attack of the blade inlet scheme can effectively suppress the impeller rotation stall and that the design point head and efficiency are increased by 6.4% and 5.7% respectively. This paper, using turbulence intensity to determine the generation of rotating stall, proposed that the average of turbulence intensity exceeding 2% is a necessary condition for the generation of rotating stall and discovered that the standard deviation of the big angle of attack of the scheme is always greater than that of the small angle being analyzed by the impeller pressure pulsation. The basic critical frequencies of blade inlet pressure pulsation with components of a low frequency is dominated by the impeller rotating frequency F0 and its harmonic frequencies 2F0, and 3F0, but the basic critical frequencies of blade outlet pressure pulsation is governed by Blade Passing Frequency (BPF). The research results can provide some theoretical support for stall research and hydraulic performance optimization of a double-suction pump.

Investigation on Pressure Fluctuation of the Impellers of a Double-Entry Two-Stage Double Suction Centrifugal Pump

Double-entry two-stage double-suction centrifugal pumps with high flow rates and high heads are used in some large water supply applications. The pressure fluctuation of the impeller is a key factor influencing the vibration in centrifugal pumps. In this paper, the pump is simulated and verified by experiments, and the pressure fluctuation distribution of two stage impellers is obtained. The study on the time domain and frequency domain of the two-stage impellers demonstrates that the pressure fluctuation of the first-stage single-suction impeller is affected by the twin volute. At 1.0 Q, the dominant frequency on the blade suction side and pressure side is twice the rotation frequency. The main frequency of pressure fluctuations at the outlet side of the blade at a low flow rate is higher than that at the design flow rate. Pressure fluctuations in the second-stage impeller are influenced by the inter-stage passage. The dominant frequency amplitudes grow incrementally along the streamlined direction. In the second-stage double-suction impeller, the dominant frequency amplitude at 0.6 Q is approximately twice that of 1.0 Q. Research in this paper can guide the design and operation of a two-stage pump.

Comparative studies on air borne noise and flow induced noise of a double suction centrifugal pump

The Flow Induced Noise (FIN) of a centrifugal pump directly affects the Air Borne Noise (ABN) of the same. But, the information regarding focus on ABN of a pump in relation to its FIN is very scarce. This paper presents the comparative study performed on the ABN and FIN of a double suction centrifugal pump. Experiments were conducted on a double suction pump of specific speed (ns) 19 to measure ABN. Free field noise measurements for ABN, aligning with the industrial standards were conducted using FFT analyzer for 3 speeds such as 990 rpm, 1200 rpm, and 1450 rpm. For each speed, the normalized flow ratio (QQn) covered were 0.4, 0.6, 0.8, 1 and 1.2 for measurements. For FIN prediction, transient numerical simulations were conducted for the same pump at 990 & 1450 rpm. Detached Eddy Simulation (DES) and Fast Fourier Transform (FFT) were used to understand the noise generation at the blade passing frequency (BPF) and the variation of discharge flow recirculation in impeller outlet at different speeds. Moreover, for FIN, a generalized quadratic equation with parabolic form is derived for a speed of 1450 rpm. Also, the derived equation at 1450 rpm has been used to develop a relation to predict the FIN at other speeds. Further, the derived FIN relations are used to predict the ABN at different speeds by expressing ABN in terms of FIN for particular speed. Overall, the developed FIN function is useful in predicting the FIN in dB at BPF of a double suction pump for impeller Reynolds number and specific speeds in ranges 2.7∗106≤Re≤8.2∗106 and 19≤ns≤52 respectively with error ranging from +7.5 % to −7.5 %. Empirical correlation is also developed to predict the FIN with error ranging from +6 % to −6%, where FIN was the function of structural (geometrical) parameters and hydraulic (fluid and flow) parameters of the pump. Also, the methodology is used to predict ABN at BPF from the calculated FIN for that particular speed with error ranging from −2.5 % to +2.5 %.

Intelligent Diagnosis on Flexible Material Windings in a Double-Suction Centrifugal Pump With Boosting Capsule Network (BCN)

The double-suction centrifugal pumps (DCPs) are important hydraulic machinery for agricultural, industrial, and urban life. However, they are suffering a high risk of flexible winding material due to the increasing pollution of rivers. Unfortunately, this serious problem has not yet received the attention of researchers. To solve this foreseen issue, a novel deep-learning (DL) model, namely the boosting capsule network (BCN), is proposed to solve the weaknesses of the convolutional neural network (CNN) and capsule network (CN). The boosting part fully refines the kernel thought of CNNs to achieve an optimal tradeoff between time-consuming and accuracy of diagnostic tasks. The computational burden and generality of BCN are dramatically reduced and improved from the traditional CN. Experimental studies, including different flow rates under different rotational speeds, are conducted to analyze the diagnostic accuracy, time consumption, and layer visualization. The results show that BCN achieves the best generalized diagnostic results for different operational conditions and data types than the compared models.

Energy-saving oriented optimization design of the impeller and volute of a multi-stage double-suction centrifugal pump using artificial neural network

To broaden the efficient operating zone and increase the energy efficiency of a multi-stage double-suction centrifugal pump, a multi-component and multi-condition optimization design method involving high-precision performance predictions, a flow loss visualization technique based on entropy production theory, and machine learning is proposed. First, the accuracy of the baseline pump numerical methodology is verified via a grid convergence analysis and experiments. Thereafter, nine design parameters of the impeller and double volute are selected as design variables. Subsequently, 150 designs are created according to the Latin hypercube sampling method (LHS) and numerically simulated using an automatic simulation program. A backpropagation neural network (BPNN) and a multi-objective genetic algorithm (MOGA) are adopted to maximize the efficiency at 0.6Q d, 1.0Q d, and 1.2Q d. Finally, the optimal results are verified via numerical calculations and analyzed. The results indicate that the efficiency of the optimized pump is increased by 2.05%, 3.56%, and 5.36% at 0.6Q d, 1.0Q d, and 1.2Q d, respectively. The comparative analysis of the energy characteristics reveals that the improved performance of the optimized pump can be attributed to the improved matching between the rotor and stator. This research further demonstrates the accuracy and reliability of the optimization method using an artificial neural network (ANN).

Study of rotor–stator interaction phenomenon in a double-suction centrifugal pump with impeller vane trailing edge as a design parameter

Various geometrical parameters, such as cut-water clearance, volute tongue location, tongue radius, vane trailing edge profile, and flow parameters like speed and operating point, affect the rotor–stator interaction in a centrifugal pump. In the present investigation, vane trailing edge is selected as a design parameter for profile modifications to study and reduce the rotor–stator interaction intensity and hence the pressure pulsations. A double-suction centrifugal pump with tangential discharge volute (M1) and specific speed (ns) 19 has been selected for the numerical experiments. Transient analysis using detached eddy simulation is used for predicting flow parameter behavior at impeller periphery (primary source) and volute tongue locations (secondary source). The impeller periphery probes in the rotor–stator interaction zone are used to identify the intensity of the jet-wake flow phenomenon and its interaction with the volute tongue. Similar strategy has been applied by modifying the trailing-edge profile of the original geometry with vane underfiling (M2) and the M2 vane geometry with novel trailing-edge profile (M3). The pressure pulsation behavior along the impeller periphery (primary source) shows the strong reduction of pressure amplitude near volute tongue by 42% in M3 compared to M1 aligning with the reduction of jet-wake flow intensity. The pressure fluctuation (rms) near volute tongue (secondary source) shows an average reduction of 11% in modified trailing edge (M3) relative to M1. The intensified rotor–stator interaction due to vortex shedding in M2 causes relatively higher pressure fluctuations (rms) near volute tongue compared to M1 and M3.

Introducing Non-Hierarchical RSM and MIGA for Performance Prediction and Optimization of a Centrifugal Pump under the Nominal Condition

In order to improve the operation performance of the multi-stage double-suction centrifugal pump and reduce the internal energy loss of the pump, this paper proposes a single-objective optimization design method based on the non-hierarchical response surface methodology (RSM) and the multi-island genetic algorithm (MIGA). Nine parameters, such as the blade outlet width and blade wrap angle, were used as design variables, and the optimization objective was efficiency under design conditions. In total, 149 sets of valid data were obtained under the Latin hypercube sampling method (LHS), the corresponding thresholds were set for efficiency and head, and 99 sets of valid data were obtained. A cross-validation analysis of the sieved data was carried out based on non-hierarchical RSM, global optimization of the efficiency was carried out using MIGA, and numerical verification was carried out via CFD. The research results show that compared with hierarchical RSM, non-hierarchical RSM can approximate the nonlinear relationship between the objective function and the design variables with higher accuracy, and the model fitting R2 value was 0.919. The efficiency was improved by 3.717% after optimization. The overall prewhirl of the impeller inlet after optimization decreased, the internal speed of the volute significantly improved, the large-area vortex at the volute and the outlet pipe was eliminated, the impact loss at the volute separating tongue disappeared, and the overall hydraulic performance of the pump was improved. The total entropy output value of the optimized pump was reduced by 4.79 (W/K), mainly concentrated on the reduction in the entropy output value of the double volute, and the overall energy dissipation of the pump was reduced.

Mechanisms of performance degradation in a double-suction centrifugal pump under inflow distortions

Inlet pipes of the centrifugal pump are generally bent to fit in the limited installation space, which can cause inflow distortions for two sides of the double-suction impeller. This study aimed to understand the effect of primary geometric parameters of inlet pipes, including corner angle, straight pipe length downstream of elbow, and turning radius, on pump performance and pressure fluctuations. The pump head, efficiency, and pressure fluctuations were measured for six kinds of inlet pipes in the experiment. Unsteady numerical simulations were performed to understand the flow mechanisms. Results indicate that the bending of inlet pipes is a significant reason for the loss of pump head and efficiency. The penalty on pump performance is augmented by the increase in corner angle, decrease in turning radius, and installation of a short straight pipe downstream of the elbow. Pump efficiency could be maximally reduced by 6.58% with a large corner angle and a small turning radius. The bending of inlet pipes induces pressure imbalance for the two sides of the impeller and increases low-frequency disturbance in the suction chamber, which are responsible for the performance loss. Numerical results reveal that the low-frequency disturbance is caused by the vortex formed in the suction chamber, and the accompanying secondary vortex aggravates the pressure fluctuation synchronously. Parametric studies conclude that the corner angle should be minimized to reduce the penalty on pump performance and pressure fluctuations, and a long straight pipe downstream of the elbow can be installed to decrease vibration for the pump with bent inlet pipes.

Erosion wear in a double-suction centrifugal pump using an improved erosion model

Prediction of erosion wear in double-suction centrifugal pumps is studied numerically using an improved erosion model (EM). Experiments are also performed to verify the improved EM’s prediction ability. In the experiments, painted layers of five colors are applied to the blade surfaces using spray guns to show the erosion wear distribution, where the colors and the order are selected based on the simulated results. In simulations based on the Oka model, the small-angle scratching effect is specifically added to the improved erosion model (called the Qian EM here). For the chosen double-suction centrifugal pump, the Oka EM and the Qian EM are used to predict erosion wear, including the wear area and intensity. Both EMs effectively predict the erosion areas of the leading edge, the suction side inlet part and the pressure side outlet part of the blade, but the Qian EM shows better ability to predict the erosion area of the outlet part on the suction side. Additionally, the erosion intensity seems more reasonable with the Qian EM. Inclusion of all different particle sizes in the numerical simulations is found to be necessary to predict erosion wear accurately because each single particle size may provide important information.