Pump Impeller Research Articles

Prediction of stress-fatigue life on the impeller of the reactor coolant pump based on fluid-thermal-structure interaction method

The reactor coolant pump (RCP) is the core part of the first loop in nuclear power plant. It plays a crucial role on the stability and security of the nuclear reactor operation. As the only rotating equipment in the RCP, the impeller needs to run tens of thousands of cycles in the high-temperature and high-pressure coolant, which significantly affects the physical properties and reduces the fatigue life. This paper mainly studies the law of the dynamic stress on impeller of the RCP based on the fluid-thermal-structure interaction method, further predicting the stress-fatigue life of the impeller based on the Palmgren-Miner theory. The results show that the impeller is subjected to periodic alternating stress during rotation. The stress value gradually increases with the increase of the flow. The location and value of the maximum stress on the impeller at each moment are inconsistent. The highest negative correlation between the stress amplitude and the fatigue life is found, and the correlation is more than 19%. Fatigue failure first occurs at the junction between the inlet edge of the blade and the hub, and the fatigue life on the impeller is calculated to be 146.6 years. The fatigue life of the impeller is greater than the designed life, thus characterizing the impeller safe for use in nuclear power plant.

Pressure drop reduction of the impeller spiral static mixer design enabled by additive manufacturing

A new spiral static mixer (SSM) design, also known as helical or twisted tape mixers, called the Impeller SSM, inspired by centrifugal pump impeller blades and fabricated by additive manufacturing (AM), is presented. The pressure drop and mixing efficiency of an Impeller SSM are compared to the standard SSM. Both the pressure drop and mixing characteristics are measured experimentally and validated by computational fluid dynamics (CFD) analyses. Five Impeller SSM designs of different taper, release, and attack angles were studied. Compared to a standard SSM of the same size, the Impeller SSM demonstrated a pressure drop (and power) reduction up to 18.2%. Such reductions could lead to significant energy saving and size reduction in static mixer industrial applications. Experimental results also show the ability of AM to fabricate the custom Impeller SSM without using costly machining and joining techniques.

CFD Simulation of Pressure, Temperature and Rotational Speed Influence on the Cavitation in Centrifugal Pump Impeller

The impeller is a critical rotating part of a centrifugal pump where the energy transfer to the fluid takes place. The complex nature of the fluid flow inside the impeller can give rise to cavitation which is highly undesirable. Design and operating conditions in the impeller influence the extent of cavitation. The effect of the outlet pressure, temperature and rotational speed of the impeller was studied using ANSYS CFX Computation Fluid Dynamics (CFD) software. The impeller geometry was meshed with high-quality hexahedral meshes and the y + values around the blade surface are less than 2. The k - omega turbulence model was used along with the ZGB model of cavitation. The effects of the variable parameters on the cavitation volume and the head developed were extensively studied. The numerical trends are similar to those presented in the literature. By carefully controlling the outlet pressure, the effects of increased temperature can be mitigated. Thus, it is possible to operate a centrifugal pump at higher working fluid temperatures by operating the pressure above 275 kPa.

Application of rapid prototyping technology in pump engineering

The article presents the results of the use of rapid prototyping technology when modifying the impeller of a centrifugal pump in order to increase efficiency. As a result of the implementation of the technology, the influence of parameters such as the printing speed of the main layers, the printing speed of the current layers, the thickness of the layers on the geometric accuracy of printed products was studied. According to the results of experiments, it was revealed the effect of the feed rate on the OZ axis, an increase in speed will lead to lower surface quality, higher roughness. The distance between the layers is 0,15 mm/s, getting a roughness of Ra 6,3 microns, and in the right case we used a distance of 0,05 mm/s between the layers, getting a roughness of Ra1,6 microns. The article presents the results of the analysis of the effect of exposure time and exposure time in the UV chamber on the hardness of printed products. The article presents a method for determining and compensating the geometry of prototypes based on reverse engineering technology based on the use of an optical scanner. The tests of a centrifugal pump with a prototype of a modified wheel confirm the need for such innovations as rapid prototyping to shorten the design cycle of new products, as well as reduce the cost of their development.

Automatic optimization of centrifugal pump for energy conservation and efficiency enhancement based on response surface methodology and computational fluid dynamics

Centrifugal pumps are widely used in various fields and have enormous energy-saving potential. In order to predict efficiency quickly and accurately, firstly, by establishing a hydraulic loss model for centrifugal pump impellers, the functional relationship between impeller hydraulic loss and hydraulic efficiency is constructed to establish the objective function. Secondly, calculate the main dimensions of the impeller using the velocity coefficient method and establish the objective function variables of the number of blades Z and outlet placement angle β2. And the velocity coefficient k0. Then, the method of mathematical statistics, namely response surface analysis, is used to solve the relationship between hydraulic efficiency and dependent variables within the range of variables, which plays the role of predicting hydraulic efficiency. Finally, the accuracy of the predictions is verified by numerical simulation. The results show that the hydraulic efficiency of a high specific speed centrifugal pump reaches its maximum at 1000m3/h operating conditions with a blade number of 3, a speed coefficient of 3.9 and an outlet angle of 30°. The study provides a new direction for the hydraulic design of high specific speed centrifugal pumps to achieve more accurate predictions of high specific speed centrifugal pump efficiency.

Effect of non-uniform inflow on the internal flow and hydrodynamic characteristics of a small modular reactor coolant pump

Small reactors have broad application prospects due to their advantages of safety, economy, and portability. In the first circuit of a small reactor nuclear power plant, the steam generator is directly connected to a reactor coolant pump, and there is a non-uniform flow situation, which has not been studied. Taking the small modular reactor coolant pump as the research object, the influence of non-uniform inflow on the internal flow and hydrodynamic characteristics of the small modular reactor coolant pump was investigated using CFD numerical simulation methods, and was verified by experiment. Firstly, the basic structural parameters of key hydraulic components are determined based on the design input parameters, and the initial model of the impeller and diffuser of the small modular reactor coolant pump is modeled. The channel-head, impeller, diffuser, and casing are modeled using three-dimensional software; Secondly, the hydrodynamic performance of the small modular reactor coolant pump was experimented, and the experimental results verified the reliability of the numerical simulation; After comparing the external characteristics of the straight-pipe small modular reactor coolant pump coupling model and channel-head small modular reactor coolant pump coupling model, it was found that the head and efficiency of the straight-pipe model were better than channel-head model, indicating that non-uniform inflow had a certain impact on the performance of the small modular reactor coolant pump. Finally, the internal flow states of the straight-pipe model and the channel-head model were compared and analyzed from the perspectives of pump internal flow field, pump internal velocity and pressure distribution. The results showed that the sudden contraction of the direct connection between the channel-head and the small modular reactor coolant pump and the short length of the direct connection caused the inlet flow of the pump to be non-uniform, which adversely affected the hydrodynamic and internal flow characteristics of the pump. This study provides a certain idea for the research on the suppression of non-uniform inflow from small modular reactor coolant pumps and the improvement of non-uniform inflow from small modular reactor coolant pumps.

Blending in unbaffled and baffled mechanically agitated vessels – Effect of Reynolds number and liquid height

The standard vessel for mixing in the process industry is a baffled tank. This design is very common especially for low viscosity fluids. Nonetheless, unbaffled vessels are found in industry and the laboratory. The reasons given for using unbaffled vessels are primarily concerns around cleaning the vessel between batches and the possibility of stagnation zones in high viscosity fluids particularly when properties change over the processing time. In this paper we will examine the effect of baffles on the blend time using one vessel: with and without baffles. The blend time was measured using the iodine color change method using a range of viscosities and Reynolds Numbers. The depth of the vortex was also measured. The same axial flow-down pumping impeller is used. In this work we observed that the flow patterns are dramatically different between unbaffled and baffled tanks. At high Reynolds Numbers with the baffled configuration, we see the familiar turbulent diffusion throughout the vessel. Without the baffles the fluid segregates into two zones: a swirling inner zone near the shaft and a more turbulent outer zone. The overall blend time is longer in the baffled tank at the same rotational speed compared to the baffled tank. This difference decreases with increasing Reynolds Number. We identified two blend times in using unbaffled tanks, a short blend time for the outer zone and a much longer time for the inner vortex centered zone which defines the overall blend time for the vessel. At low Reynolds Numbers the baffled blending is in the transitional flow regime between turbulent and laminar with a combination of eddies and striations. The last region of the tank to become completely mixed is located behind the baffles. Unbaffled blend times are shorter and as the Reynolds Number decreases the difference increases. The vortex is also reduced with decreasing Reynolds number. We consider this work just a beginning step in a long study and hope this work will be picked up by other researchers as happened so many times with Professor Nienow’s work.

Defect Recognition in High-Pressure Die-Casting Parts Using Neural Networks and Transfer Learning

The quality control of discretely manufactured parts typically involves defect recognition activities, which are time-consuming, repetitive tasks that must be performed by highly trained and/or experienced personnel. However, in the context of the fourth industrial revolution, the pertinent goal is to automate such procedures in order to improve their accuracy and consistency, while at the same time enabling their application in near real-time. In this light, the present paper examines the applicability of popular deep neural network types, which are widely employed for object detection tasks, in recognizing surface defects of parts that are produced through a die-casting process. The data used to train the networks belong to two different datasets consisting of images that contain various types of surface defects and for two different types of parts. The first dataset is freely available and concerns pump impellers, while the second dataset has been created during the present study and concerns an automotive part. For the first dataset, Faster R-CNN and YOLOv5 detection networks were employed yielding satisfactory detection of the various surface defects, with mean average precision (mAP) equal to 0.77 and 0.65, respectively. Subsequently, using transfer learning, two additional detection networks of the same type were trained for application on the second dataset, which included considerably fewer images, achieving sufficient detection capabilities. Specifically, Faster R-CNN achieved mAP equal to 0.70, outperforming the corresponding mAP of YOLOv5 that equalled 0.60. At the same time, experiments were carried out on four different computational resources so as to investigate their performance in terms of inference times and consumed power and draw conclusions regarding the feasibility of making predictions in real time. The results show that total inference time varied from 0.82 to 6.61 s per image, depending on the computational resource used, indicating that this methodology can be integrated in a real-life industrial manufacturing system.

Experimental study of the flow of viscous Newtonian fluids in a centrifugal pump

This paper analyzes the influence of viscosity and impeller rotation speed in the calculation of the flow and in the theoretical prediction of the performance of a centrifugal pump impeller. The evaluation of the viscous effects allows the prediction of the frictional losses of the impeller and a more correct evaluation of the operating characteristics than can be obtained with a perfect fluid. The viscosity modifies the values of the velocity distribution in the channels of the impeller and the deviation of the flow at the exit of the blade. The experiments were carried out with mineral oils of different viscosities varying between 96.10-3 Pa.s and 520.10-3 Pa.s and which are represented by a perfectly newtonian behavior.

Generation mechanism and control methods of secondary flows in the impeller of axial flow pumps

The secondary flow in the impeller of an axial flow pump is an important factor affecting the safe and stable operation of the unit. However, there is still a lack of systematic research on the generation mechanism of secondary flow and corresponding control strategies in axial flow pumps. To better understand the secondary flow characteristics in the axial flow pump, based on the momentum equation of relative motion, the basic distribution characteristics of the potential rothalpy gradient (PRG, or the reduced static pressure gradient) in the impeller of an axial flow pump were systematically analyzed. Two typical secondary flows were found, namely, trailing-edge hub-shroud type secondary flow at the blade outlet hub side and leading-edge hub-shroud type secondary flow at the blade inlet shroud side. The generation of these secondary flows is directly related to the effect of natural adverse PRG. A new blade design method is proposed. The essential idea of this method is to give the blade loading strategy based on grasping the macro-flow characteristics and control PRG characteristics by adjusting the real blade loading δp (i.e., the static pressure difference between the blade pressure and suction surfaces) and, thereby, control the above-mentioned secondary flows. The application of an axial flow pump showed that the blades designed based on this method can effectively control these secondary flows and reduce pressure fluctuations. The average decrease in pressure fluctuation on the blade inlet shroud side and the outlet hub side is 17.79% and 20.03%, respectively.

P10: CFD Simulation Of Thrombosis In A Catheter Pump Inside The Left Ventricle

Study: Catheter pumps are small axial flow assist devices indicated for temporary use for a variety of indications. Uniquely positioned within the circulation, the pump impeller and motor are situated in the ascending aorta, and blood is pumped from the left ventricle (LV) via a long angled inlet cannula. The interplay of pulsatile LV blood dynamics with hemocompatibility performance of a catheter pump is not well characterized. The purpose of this study is to conduct computational fluid dynamics (CFD) simulation that includes multifactorial and synergistic models of blood damage to a catheter pump within a virtual in-vivo environment to analyze its hemodynamics. Methods: A generic catheter pump whose shape is inspired by the Impella 5.0 is situated within a static geometry consisting of a semi-realistic LV and aorta. We apply bloodDamageFoam, an OpenFOAM-based CFD code, to predict the hemodynamic flow and blood damage generated by the pump operating at 20 kRPM. The thrombosis model includes seven biochemical and biophysical agonists and accounts for the effects of high shear stress induced activation of von Willebrand factor. Results: CFD predicted 4.43 LPM blood flow rate from the LV delivered into the aorta. Moderate levels of hemolysis were predicted. The thrombosis model showed moderate degrees of platelet deposition on the cage of the inlet cannula and within the catheter pump chamber. Because the LV in this simulation was not beating, unrealistically large regions of flow stagnation and high platelet activation were observed in the LV. To address this, realistic pulsatility of a dilated LV is currently being modeled. Our latest progress will be presented at the meeting.

P42: Effect of impeller number and design variation on the hemolysis performance of magnetically levitated centrifugal pumps

Background: Hemolysis is linked to an increase in the length of exposure to high shear stress in addition to the degree of shear stress. Turbulence is also a significant cause of blood injury. In the maglev ventricular assist device blood is only in contact with the pump housing and impeller. So, it is vital that decreasing NPSS, reducing exposure time, and the suppression of disturbed flow are incorporated into the optimization design for blood pump. The blood pump must also deliver enough pressure head and flow rate to sustain clinical circulation. The purpose of this study is to analyze the effects of different number of blades, number of splitters, blade length, blade angle and its distribution on pressure head, hemolysis and platelet activation. Firstly, computational fluid dynamics was used to analyze the effects of the above characteristics on scalar shear force, velocity distribution, hemolysis, and then the validity of the numerical analysis was verified by combining with in vitro hemolysis experiments, and finally the best impeller design was selected. Methods: In this study, three rotors with different number of vanes were developed. Compared to the CentriMag with curved vanes, all three variants have straight vanes to improve the pump efficiency and the passability in the pump. The inlet and outlet edges of the vanes are chamfered to reduce the shear stress area. In order to avoid excessive axial force makes the whole rotor in the rotation process floating, in the back cover plate position designed to raise the structure, in order to increase the surface area, reduce the axial force to stabilize the leaf top clearance, the three new design of the rotor back cover plate raised degree is also different. In order to balance the number of blades and the impeller’s hydraulic performance, the outer diameter of the impeller is also designed. 6-blade rotor consists of 3 blades and 3 spliters, the outer diameter of the impeller is 43.5mm; 8-blade rotor consists of 4 blades and 4 spliters, the outer diameter of the impeller is 43mm; 9-blade rotor consists of 3 blades and 6 spliters, the outer diameter of the impeller is 43mm. The 9-blade rotor consists of 3 blades and 6 splitters, with a minimum impeller outside diameter of 42.5mm. Results: By CFD simulation, the 9-blade maglev impeller outperformed several other impellers in terms of shear force, shear area, and passability, and the NIH in in vitro experiments was <0.0016g/100L Conclusion: The 9-vane magnetically levitated rotor developed in this study improves pump passability and reduces the occurrence of hemolysis in the pump by reducing the vane shear forceFigure 1. Independently developed magnetic levitation hemolysis platformFigure 2. Newly designed 3-bell bladeFigure 3. Computational fluid dynamics analysis of different impellers

Integration of multiple failure mechanisms in a life assessment method for centrifugal pump impellers

Methods in predictive maintenance are frequently confronted with limited applicability to realistic scenarios. The available approaches are often used for a single design, requiring an entirely new analysis for a slightly different case. A solution for this issue could be using a physical model. However, physical models focus on one unique failure mechanism, while, in a practical application, several mechanisms are typically active at the same instant. This work proposes and demonstrates a new methodology that combines different failure mechanism into an integrated life prediction model. Failure Modes and Effects Analysis is used to identify the different failure mechanisms that occur in a component simultaneously. Physical and empirical models are then analyzed and modified to be implemented in a realistic case of a centrifugal pump impeller applied in a maritime environment. As erosion, cavitation, and corrosion are the main failure mechanisms of an impeller, the combination of them quantifies the degradation increment during different types of pump operation. The proposed methodology is compared with traditional failure rate models and an established cavitation model that uses an aging factor to cover other failure mechanisms. In conclusion, it is demonstrated that the proposed methodology is more sensitive and reliable in describing the degradation process for a wide range of operating conditions, since all the mechanisms are considered.

Usage of 3D printing technology in centrifugal pumps and material selection

The fused deposition modeling (FDM) technique which is one of the 3D printing technologies was used to produce a centrifugal pump impeller. The fabrication and investigation of the impeller were preferred because of its complex geometry and the difficulties encountered in its production. The most commonly used ABS, HIPS, PLA, and carbon fiber filaments were preferred to compare and determine the most suitable material for the production of the impellers. Firstly, mechanical test specimens from four different materials were printed in the 3D printer according to standards. Then the tensile tests and quasi-static punch shear tests (QS-PST) were applied to determine the mechanical properties of the 3D printed parts. Also, the mechanical tests were repeated to some specimen with the different fillings to define the optimum fill rates. Secondly, the impellers were fabricated from four materials by using the 3D printer in determined fill rates. Then, these impellers were mounted in the actual pump system, and pump performance tests were performed. In the pump performance tests, the head, pump efficiency, and electric power parameters were measured against the flow rate for each impeller. Finally, the mechanical properties and pump performance of the impellers compared with the GG25 cast iron impeller which is produced by traditional technique. As a result, PLA was selected as the most appropriate material for the production of the impellers. Furthermore, PLA showed superior performance compared to others when price, production time, and product weight parameters were considered.

Numerical analysis of random vibration fatigue for a typical airborne equipment

In this paper, the fuel pump impeller was selected as a typical airborne equipment for the investigation of random vibration fatigue. First, based on the platform of ANSYS WORKBENCH, the reasonable calculation of FSI for the impeller was carried out. Then, the stress was transferred to modal analysis, and the prestress-structure modal was extracted. Through random vibration response analysis, the stress of the impeller was obtained. The Palmgren and Miner rule and Dirlik fatigue calculation method was used to calculate fatigue life, and the result was consistent with practice. The work in this paper provided a method about how to obtain random vibration fatigue life with prestress-structure, which was critical references for aviation technologists.

Power consumption and oxygen transfer optimization for C5 sugar acid production in a gas-liquid stirred tank bioreactor using CFD-Taguchi method

Power consumption and oxygen transfer are considered the two most important direct indexes, affecting the effective and cost-efficient C5 sugar acid fermentation from C5 sugar. In this work, an effective optimization approach combining computational fluid dynamics (CFD) modeling and the Taguchi method, was presented to evaluate C5 sugar acid fermentation in a gas-liquid stirred tank bioreactor. Three most critical control factors of impeller type (Rushton turbine (RT), concaved blade disc turbine (CBDT), and four wide-blade hydrofoil impeller pumping down (WHd)), agitation speed and aeration rate involved three levels, were quantitatively studied by numerical simulation based on a validated CFD model. Results indicated that, the WHd impeller gave the best energy-saving performance, the CBDT impeller gave the best oxygen transfer performance, while the RT impeller was the most balanced one. The agitation speed contributed most to both the power consumption and oxygen transfer, while exerting minor impact on compromise indexes. The aeration rate had little contribution to power consumption and oxygen transfer, while deserving more attention when energy efficiency and trade-off optimization are considered. These findings can be used as guidelines to achieve efficient and economical C5 sugar acid production.

INVESTIGATION OF IMPELLER BLADES DESIGN FOR AXIAL FLOW PUMP USING COMPUTATIONAL FLUID DYNAMICS

The investigation of the impeller blade design for axial flow pumps used in power transformers is discussed in this paper. Due to the symmetry of the blade type, axial pumps typically have efficiency levels that are significantly lower than those of classical pumps. In this study, the geometry of the blades is modified to achieve a high efficiency in an axial pump by concentrating on a pump impeller. CF Turbo is the proprietary program used in this simulation. The computational Fluid Dynamics results for hydraulic efficiency, head torque, and pump torque were compared. To identify the key effects and their ideal design factors, Orthogonal Array, Analysis of variance and optimization techniques are used. The best ideal solution for satisfying the pump torque and head limitations is discovered when an effective design variable in impeller blades is taken into account.

Analysis Of The Causes Of Cavitation In Centrifugal Pumps On Board KM. TLIX

Inside the ship's engine room there is one component part, the Centrifugal Pump. At centrifugal pumps often experience a decrease in the performance of a decrease in the capacity of centrifugal pumps which results in mechanical damage to the centrifugal pump impeller and the onset of vibrations all occur due to cavitation on centrifugal pumps. Cavitation is the occurrence of vapor bubbles forming in a liquid that is flowing because the liquid pressure decreases to below the saturated vapor pressure of the liquid at the pump operating temperature. This research was conducted with the aim to find out the cause of the declining performance of centrifugal pump capacity which results in cavitation. Through this applied scientific work can find the cause of the decrease in the capacity of the ship's centrifugal pump and the results will be used as a reference or reference for fellow machinists so that the centrifugal pump on the ship can operate optimally.

Ensuring vibration characteristics of reactor plant centrifugal pumping equipment

Requirements of low vibration and low noise level are imposed on reactor plant centrifugal pumping equipment. Computational research of vibration characteristics of centrifugal pumping is required in order to choose the optimal design alternate. Representativeness and adequacy of computational research are ensured by using verified methods of mathematical modeling. The paper presents the results of comparative analysis of various options of centrifugal pump wet end with the hydraulics master data. Hydrodynamic flow analysis was made and pump impeller loads were determined to calculate the pump rotor rotational dynamics. The computational analysis considers the rotor residual unbalance. According to the calculations carried out the pump vibration characteristics were analyzed and compared to those of the prototype pump with low vibration characteristics.

A comprehensive review on synergistic and individual effects of erosion–corrosion in ferrous piping materials

Abstract The degradation of materials due to erosion–corrosion occurs on the components that handle particle-laden corrosive slurry. The combined attack of mechanical erosion and corrosion shows increased material loss than the individual action of erosion and corrosion. The synergy accelerates material removal by eroding the corroded surface layer and corroding the surface due to the elimination of the passivating oxide layer by erosion. The synergism of erosion–corrosion is found to be more complex. Further, the coupled effect of mechanical erosion and electrochemical corrosion and the factors influencing erosion–corrosion still needs to be fully investigated. This review aims to provide a general and detailed summary of the interaction between erosion and corrosion of materials for the applications of pump impellers, pipelines for desalination, and oil and gas transportation. Importance is also given to the factors influencing erosion–corrosion, such as erodent particle properties (hardness, size, and shape), slurry properties (particle concentration, pH value, temperature), and flow characteristics (impingement angle, velocity). The various erosion models and the most used apparatus have also been reviewed.