Multistage Centrifugal Pump Research Articles

Fracture analysis and improvement of charging pump shaft in nuclear power plant

The charging pump of a nuclear power plant is a multi-stage double shell centrifugal pump. From the installation period, the pump shaft broke after 25 times of start-up and shutdown and 2913 hours of cumulative operation. As the charging pump is one of the core equipment in the normal operation and accident of the nuclear power plant, the root cause of the pump shaft fracture must be found and corrective measures must be taken, otherwise there will be major safety hazards. Through the analysis of the material, design structure and mechanical properties of the pump shaft, it is found that the root cause is that there is a deviation in the processing of the structural dimension of the stress relief groove of the pump shaft, which leads to the insufficient fatigue strength margin and the occurrence of abnormal operation conditions during the superposition commissioning, which leads to the fracture of the pump shaft. By optimizing the structural design of the stress relief groove and controlling the reasonable operation, no fracture occurred again. The causes and treatment of this typical event can provide certain theoretical support for the design, operation and maintenance of similar equipment.

Effect of axial offset of rotor on thrust characteristics of a centrifugal pump

To ensure the reliability of multi-stage centrifugal pumps, the prediction of axial thrust is an important issue for the design of balancing device and selection of thrust bearing. However, it is known that the fluid forces acting on rotor could be sensitively affected by the geometrical relations between rotor and stator especially at the low flow rate. Among them, the effect of axial offset of rotor has not been studied sufficiently though the axial offset is easily caused by accumulation of manufacturing tolerances and assembling errors. In this study, experimental/numerical investigations on the effect of axial rotor offset in a final stage model of a three-stage centrifugal pump are carried out. The axial offset is intentionally given to shaft system to the both of discharge/suction side. As a result, the axial thrust is significantly affected by the axial offset in the flow rate range below 50% of the design. It is shown by CFD analysis that this effect of axial offset is caused by the interaction between the back flow from the diffuser and the main flow.

Effect of an Inducer-Type Guide Vane on Hydraulic Losses at the Inter-Stage Flow Passage of a Multistage Centrifugal Pump

A multistage centrifugal pump was developed for high head and high flow rate applications. A double-suction impeller and a twin-volute were installed at the first stage followed by an impeller, diffuser and return vanes for the next four stages. An initial design feasibility study was conducted using three-dimensional computational fluid dynamics tools to study the performance and the hydraulic losses associated with the design. Substantial losses in head and efficiency were observed at the interface between the first stage volute and the second stage impeller. An inducer-type guide vane (ITGV) was installed at this location to mitigate the losses by reducing the circumferential velocity of the fluid exiting the volute. The ITGV regulated the pre-swirl of the fluid entering the second stage impeller. The pump with and without ITGV is compared at the design flow rate. The pump with ITGV increased the stage head by 63.28% and stage efficiency by 47.17% at the second stage. As a result, the overall performance of the pump increased by 5.78% and 3.94% in head and efficiency, respectively, at the design point. The ITGV has a significant impact on decreasing losses at both design and off-design conditions. An in-depth flow dynamic analysis at the inducer-impeller interface is also presented.

Investigation of Booster Multi-Stage Centrifugal Pump’s Characteristics When Pumping-Out of Water-Gas Mixtures

The investigation of multistage centrifugal booster pump performance when delivering water-gas mixtures in configuration water jet gas pump at excess pressure intake chamber. As a dispersing device for a water-gas mixture used WJGP of various designs flow path with diaphragm nozzles having rectangular edges were used. When gas supplies at excess pressures from 0.2 to 0.37 MPa into intake chamber of water jet gas pump, it promotes the formation of a finely dispersed water-gas mixture, which leads to reduce the effect of free gas on the performance of the booster pump’s. When intake pressure of pump rises, the stability of the water-gas mixture also increases. When an increase in pressure at the inlet of the booster pump, the curves of the shaft rotation frequency - the input gas content acquire a flatter form.

Multi-Objective Optimization of Multistage Pump Balance Drum System Based on BP Neural Network and Genetic Algorithm

The axial force balancing capacity of a balance drum is a key factor affecting the life of multi-stage centrifugal pumps. In this paper, a double shell segmental multistage pump is taken as the research object. The hydraulic performance and axial force performance are set as the optimization objectives, and the performance data are obtained by numerical simulation with FLUENT software. The BP neural network is used to establish the prediction model of structural parameters of the balance system, hydraulic performance and residual axial force performance, and it is used as the adaptive value evaluation model of genetic algorithm to solve the optimal value in the sample space. The results show that the radial clearance of the balance drum and the balance tube orifice flowmeter, the axial width of the balance cavity are the significant factors affecting the hydraulic performance and axial force performance of the multistage pump. When the radial clearance of the balance drum is 0.1mm, the clearance of the orifice flowmeter is 1.95mm, and the axial width of the balance cavity is 55mm, the multi-stage pump has the best hydraulic performance and the smallest residual axial force. The vortex band in the balance cavity can increase the amount of the fluid spin and enhance the axial force balancing capacity of the balance drum. The greater the area occupied by the negative high-rotation fluid in the balance cavity, the stronger the ability of the balance drum to balance the axial force. The test results show that compared with the prototype multistage pump, at nominal flow rate, the head and efficiency of the optimized model are increased by 0.71% and 1.63% respectively, and the bearing temperature and vibration speed of the multi-stage pump are significantly reduced.

Research Progress and Prospects of Multi-Stage Centrifugal Pump Capability for Handling Gas–Liquid Multiphase Flow: Comparison and Empirical Model Validation

The working capability of multi-stage pumps, such as electrical submersible pumps (ESPs) handling multiphase flow, has always been a big challenge for petroleum industries. The major problem is associated with the agglomeration of gas bubbles inside ESP-impellers, causing pump performance degradation ranging from mild to severe deterioration (surging/gas pockets). Previous literature showed that the two-phase performance of ESPs is greatly affected by gas involvement, rotational speed, bubble size, and fluid viscosity. Thus, it is necessary to understand which parameter is actually accountable for performance degradation and different flow patterns in ESP, and how it can be controlled. The present study is mainly focused on (1) the main parameters that impede two-phase performance of different ESPs; (2) comparison of existing empirical models (established for two-phase performance prediction and surging initiation) with our single-stage centrifugal pump results to determine their validity and working-range; (3) gas-handling techniques applied to enhance the multiphase performance of ESPs. Firstly, it aims at understanding the internal flow mechanism in different ESP designs, followed by test studies based on empirical models, visualization techniques, bubble-size measurements, and viscosity analysis. The CFD-based (computational fluid dynamics) numerical analysis concerning multiphase flow is described as well. Furthermore, gas-handling design methods are discussed that are helpful in developing the petroleum industry by enhancing the multiphase performance of ESPs.

Flow Field Analysis and Feasibility Study of a Multistage Centrifugal Pump Designed for Low-Viscous Fluids

A multistage centrifugal pump is designed for pumping low-viscosity, highly volatile and flammable chemicals, including hydrocarbons, for high head requirements. The five-stage centrifugal pump consists of a double-suction impeller at the first stage followed by a twin volute. The impellers for stages two through five are single-suction impellers followed by diffuser vanes and return channel vanes. The analytical performance is calculated initially in the design stage by applying similarity laws to an existing scaled-down pump model designed for low flow rate applications. The proposed pump design is investigated using computational fluid dynamics tools to study its performance in design and off-design conditions for water as the base fluid. The design feasibility of the centrifugal pump is tested for other fluids, such as water at a high temperature and pressure, diesel and debutanized diesel. The pump design is found to be suitable for a variety of fluids and operating ranges. The losses in the pump are analyzed in each stage at the best efficiency point. The losses in efficiency and head are observed to be higher in the second stage than in other stages. The detailed flow behavior at the second stage is studied to identify the root cause of the losses. Design modifications are recommended to diminish the losses and improve the overall performance of the pump.

Introducing machine learning and hybrid algorithm for prediction and optimization of multistage centrifugal pump in an ORC system

The isentropic efficiency of the working fluid pump has a significant impact on the overall performance of the organic Rankine cycle (ORC) system. Based on machine learning, this paper proposes an experimental data-driven isentropic efficiency prediction model. Meanwhile, S-fold cross validation algorithm and smoothing factor circulation screening technology are used to improve the predictive ability of the model. The prediction accuracy of the optimized model and the unoptimized model are compared with each other. The influence of several operating parameters on isentropic efficiency are analyzed. In addition, with intelligent algorithm, the boundary values of operating parameters are determined. The genetic algorithm (GA) and particle swarm optimization (PSO) are combined into a GA-PSO hybrid algorithm. Subsequently, the hybrid algorithm is integrated with the machine learning model to predict and optimize the isentropic efficiency under full operating conditions. The highest isentropic efficiency reaches up to 58.73%. The prediction and optimization of the isentropic efficiency of multistage centrifugal pump under full operating conditions provides not only a useful guidance on assuming pump efficiencies in theoretical analysis, but also a meaningful reference for obtaining the optimum overall operating performance of the ORC system.

Ways to reduce hydraulic losses in multistage centrifugal pumping equipment for mining and oil-producing industries

Purpose. To study hydraulic losses in pumping units during pumping and transportation of liquids, to develop the design and technology solutions to improve the energy efficiency of centrifugal pumps in the mining and oil-producing industries. Methodology. In the theoretical and experimental analysis of hydraulic losses during the transportation of liquids, the hydraulics and experimental analysis methods were used. Findings. As a result of the research carried out, a new design scheme of a multistage centrifugal pump has been developed, providing a coaxial arrangement of impellers, which allows reducing hydraulic losses in pump elements and increasing the energy efficiency of pumping units. Originality. Based on the analysis of existing designs of multistage blowers of axial and centrifugal types, the distribution of hydraulic losses in the elements of a centrifugal blower with coaxial impellers is considered. Experimental dependences on the establishment of pressure flow and power characteristics are presented. Based on the accounting of hydraulic losses, the energy efficiency of the design of the pumping unit with the coaxial arrangement of the impellers was assessed. Practical value. The new design of a centrifugal pump with coaxial impellers reduces hydraulic losses by more than 23% compared to traditional designs of centrifugal pumps. The results of the work can be used by design, research, and industrial organizations engaged in the design and operation of pumping equipment.

Optimization for First Stage of Multistage Pump Based on Response Surface Methodology

To improve the efficiency of a multistage centrifugal pump at design point, the response surface methodology was applied to construct an approximation function between the design-point efficiency of the first stage in multistage centrifugal pump and the design variables of the impeller. First, important geometric parameters are selected as factors of a one-factor experimental design. Four parameters that had greater influence on the hydraulic efficiency were screened out from the simulation results using parameter sensitivity analysis. The optimal design points for each level of the parameters were then determined by central composite design and the response surface analysis method. The efficiencies of the impeller schemes generated in the Design-Expert software was executed with CFD. The effects of the single parameters were analysed, and the approximation model solved to find the optimal parameter combination that improve the efficiency by 3.62% at design point. And the inner flow was improved in high flow rate condition.

Influence of operational changes of clearances in pump channels on the work of the automatic balancing device

Automatic balancing devices are used to balance the axial force in many multistage centrifugal pump designs. Despite the obvious advantages of these devices their failure is one of the main reasons for the complete failure of the pump unit. The axial force acting on the pump rotor can be changed under pump operation in a sufficiently large range and up to several tens of tons. Usually the calculation of automatic balancing device is made under pump's operating parameters. At the same time it is possible the changing of value of the axial force generated by the automatic balancing device on the calculated parameters due to the interdependence of hydrodynamic processes in clearances of the flow part of the pump and in the clearances of the balancing device. The analysis of possible causes of the axial force value changes as a result of unbalanced pressure forces acting on pump impellers and counterbalancing of axial forces arising in face gap balancing device is presented. An improved methodology for calculating the estimation of the axial force arising in the balancing device using the example of industrial multistage centrifugal pump is proposed.

Axial forces in multistage back-to-back pumps

Since the pressure of the pumps for the oil and gas industry and feed water pumps for the thermal and nuclear power plants are increasing and at the same time the production costs need to be reduced, the demands for development of the modern multistage centrifugal pumps are increased. An enlargement of stage numbers results in an increase in the distance between the bearings and as a result the shaft deflection increases. Also, a large number of stages leads to occurrence of a significant axial force acting on the pump rotor. These issues are solved by applying a back-to-back design with a throttling bush between the groups of stages. An arrangement with such throttling bush results in an additional axial force due to the different directions of leakage in the channels (side wall gaps) between the main disks of the last impellers of both stage groups and stator elements. Therefore, the design of a throttling bush with special balancing holes was proposed. This paper examines the processes occurring in the throttling bush and compares the operating parameters for two design options-with special balancing holes, and without them.

Research of Influence of the Inlet Elements Design on a Hydraulic Efficiency of an Intermediate Stage in the BB3-Type Multi-Stage Centrifugal Pumps

This article presents the results of computational studies for different options of inlet design in an intermediate stage of a BB3 type multi-stage pump intended for transportation of crude oil and other similar liquids. Hydraulic losses in the flow part elements are compared for three different options of the inlet blades in the return channels of an intermediate stage.

Action Research on Virtual-Reality-Assisted Product and Process Design

Virtual reality (VR) technology improves engineering activities, enabling a better understanding of products and processes. A complete conversion from the existing CAx software to a VR environment could improve product and process design activities, leading to new practices. This article aims to provide key insights, technical evidences, and related impacts on the engineering activities of industrial companies while integrating the existing systems with VR as a supporting tool for product and process design. The results indicate improved design and limited negative impacts related to errors during the manufacturing phase. An action research study involving Oil&Gas manufacturing companies was conducted to explore the following four CAx-VR scenarios: CAD–VR for ergonomics/reachability, CAE(CFD)–VR and CAE(FEM)–VR for abstract data visualization, and CAM–VR for packaging. For each scenario, applicative cases focusing on Oil&Gas products, such as multistage centrifugal pumps and ball valves, have been investigated. Furthermore, a detailed discussion of the involved chain of software applications and impacts on the engineering activities for each scenario establishes the reliability of the integrated environment for CAD, CAE, and CAM data immersive visualization.

Research on the Pump Shaft Stability Analysis of Multistage Centrifugal Pump During Closed-Valve Start-Up Process

In order to analyze the pump shaft stability of multistage centrifugal pump during the closed-valve start-up process, the transient internal fluid field and structural field during the closed-valve start-up process of the TDM 35-140×13 segmental multistage centrifugal pump are solved by transient fluid-solid coupling. The transient deformation and vibration velocity of the pump shaft are analyzed. It is found that the maximum deformation amount of the third stage impeller and the pump shaft cylindrical contact surface (N=7 node area) during the whole closed-valve transition start-up process is the largest. The maximum deformation in the region where the nodes 1≤N≤10 are significantly greater than that in other regions. In the 11≤N≤19 node, with the node position coordinate value N increasing, the maximum deformation amount is continuously decreasing. During the entire closed-valve transition start-up process, the vibration speed of the pump shaft fluctuates drastically. In the node of 1≤N≤19, with the node position coordinate value N increasing, the maximum vibration velocity first increases and then decreases. The maximum vibration speed at N=11 nodes is higher than that of all other nodes.

Research on the Transient Hydraulic Characteristics of Multistage Centrifugal Pump During Start-Up Process

Compared with the periodic unsteady flow induced by single-stage centrifugal pump, the internal flow state of multistage centrifugal pump is more complicated and the flow is more disordered. In this paper, the start-up process is divided into two stages: the closed-valve transition and the open-valve transition. The transient operation process is simulated numerically, and the pump characteristics and the evolution characteristics of the internal flow field are analyzed. It is found that when the impeller does the same work, compared with the steady state at the same speed, the mechanical energy in the internal flow field is converted into more kinetic energy and less pressure, which is a typical performance of the transient effect during the start-up process of the closed-valve transition. Compared with the steady state at the same flow rate, in the initial stage of the open-valve start-up phase, the stall group in the impeller flow channel is larger and the number of stall groups is more during the transient process, which exacerbates the rotational stall of the internal flow of the impeller, and the flow is more disordered. As a result, the amplitude of the hump fluctuation is greater than that under the same flow steady state.

Hydrodynamic modeling of cavitation in a multistage centrifugal pump during its operation in the constant feed mode with a change in the rotor speed of the pump

Hydrodynamic modeling of cavitation for a multi-section high-speed centrifugal pump operating at a constant supply is carried out. The cavitation characteristics of the pump for various pump operating modes are determined taking into account changes in the rotor speed. The operation parameters of the mobile pumping system for these modes are calculated. It has been established that improving the cavitation qualities of a pump by reducing the speed of the pump rotor with a constant flow rate is not a productive method.

Расчет критических частот ротора многоступенчатого насоса с учетом эффекта Ломакина в переднем уплотнении рабочего колеса

Studies of dynamic frequencies are an important stage in designing multistage vane pumps. This research aimed to confirm the rigidity and vibrational reliability of the pump rotor. Based on the recommendations of J.F. Gülich, the nominal rotational speed of the rotor shaft should differ from the cutoff speed by no less than 25 %. The Lomakin effect supposes taking into consideration the hydrodynamic forces acting in the gap seals and having a damping effect on the pump rotor. This research solved the problem of developing and verifying a numerical method of calculating hydrodynamic forces, which arise in seals of vane pumps at critical speeds. The studies were conducted on a ‘dry’ model of the rotor using ANSYS Mechanical software package. During computational modeling of bearings and seals, the COMBIT214 ele¬ment was used where the stiffness coefficient values were set. These values were determined by calculating the flow parameters in the gap seal using ANSYS CFX. The proposed method was verified using the experimental data obtained. The seal rigidity was calculated for different operating modes of the pump. It was shown that the hydrodynamic forces which arose in the gap seals had a significant influence on the rotor’s critical speed. Accounting for these forces increased the main own frequency of the rotor by approximately 44 %. This fact had a significant qualitative and quantitative impact on the vibrational characteristics of the pump. This study showed that the value of the hydrodynamic force was influenced by several factors: shaft deflection, differential pressure and geometry of the gap seal. The proposed method is recommended for use for multistage centrifugal pumps.

Optimal Pipe Sizing and Operation of Multistage Centrifugal Pumps for Water Supply

AbstractThe operation of multistage pumps transporting water from the source to the delivery point requires balancing of the pressure at the junction of the pump and pipeline according to their cha...

Method of computer-aided profiling of components of flow passages of centrifugal pumps for fuel and energy complex

Today, the fuel and energy complex (FEC) is the basis of Russian economy. It includes the most dynamically developing industries, such as petrochemical, oil refining, etc., associated with the production, transportation and processing of various fuels, as well as industries engaged in the production and distribution of electricity: thermal engineering, hydropower engineering and nuclear power engineering. The nomenclature of FEC centrifugal pumps includes a wide list of names: singleand multistage centrifugal pumps of low, medium and high pressure for clean water, water with impurities and various aggressive media [1, 2], pumps for oil production and transportation (trunk, booster, electric centrifugal production pumps, pumps for pumping leaks, etc.) and special pumps used in oil refining (cracking, cantilever chemical, etc.) [3]. The development of technical solutions aimed at improving energy efficiency as well as reliability and durability is one of the trends in the development of centrifugal pumps FEC that are most widely covered in engineering literature [4.9]. Along with this, reducing the complexity and cost of production of these pumps due to the automation of the design process remain just as important. In the given article, questions of development of a method of automated profiling of components of flow passage of centrifugal pumps for needs of FEC are considered. The description of the proposed method and the results of its approbation on the example of profiling of the flow passage of the impeller of the centrifugal cantilever chemical pump AH 12.5/50 are presented. Comparison with other known methods is carried out. The estimation of time costs for design works is carried out. It has been found that the automated profiling of the flow passage of the impeller according to the presented method took 720 times less time than manual profiling using conventional methods.