Centrifugal Impeller Research Articles

Multi-objective optimization design of a centrifugal impeller by positioning splitters using GMDH, NSGA-III and entropy weight-TOPSIS

Multi-objective optimization design of a centrifugal impeller by positioning splitters using GMDH, NSGA-III and entropy weight-TOPSIS

Sensitivity analysis and optimization of a CO2 centrifugal compressor impeller with a vaneless diffuser

Sensitivity analysis and optimization of a CO2 centrifugal compressor impeller with a vaneless diffuser

Multi-objective optimization of the centrifugal compressor impeller in 130 kW PEMFC through coupling SVM with NSGA -III algorithms

ABSTRACT Centrifugal compressor is a typical air compressor, which is an important subcomponent of the air supply system in fuel cell system. Optimizing the designing structure of centrifugal compressor plays significant influence on the output performance of fuel cell systems. However, existing experimental and numerical methods suffer from much economic and time cost and are inadequate for designing optimized centrifugal compressor. Thus, we develop a novel artificial intelligence (AI) framework integrated the data-driven surrogate model and stochastic optimization algorithm to achieve multi-objective optimization of the centrifugal compressor impeller. With the database obtained from the constructed three-dimensional (3D) steady-state centrifugal compressor model, the data-driven surrogate model based on Support Vector Machine (SVM) is trained. Then, the surrogate model coupled with a non-dominated sorting Genetic Algorithm (NSGA-III) is used to obtain the optimal solution of structural parameters. Compared with the original compressor design based on the established 3D model, the optimized compressor is comprehensively verified. Within the working range of the centrifugal compressor, the pressure ratio and isentropic efficiency of the optimized compressor have been significantly improved. The proposed optimized method is effective for the performance improved in fuel cell centrifugal compressor.

Thermal-electromagnetic coupling simulation study of high efficiency and energy saving application of induction motor for offshore oil platform

The load of the offshore oil platform is mostly pump unit, Asynchronous motor with cage rotor has simple structure, reliable operation, and inexpensive. But it has a huge shortcoming of its low efficiency. When the output power is constant, improving efficiency is to decrease loss of the motor. This paper discusses some methods of energy saving and low consumption of the pump unit to improve the efficiency. Direct drive pump can completely eliminate transmission loss, eliminate bearing of centrifugal pump impeller pump, reduce friction, and thus reduce mechanical loss. The rotor copper loss and stator copper loss will be reduced by using copper squirrel cage and multi-wound motor, so the efficiency of the motor will be improved. If all the pump unit of the offshore oil platform is turned into this low consumption motor, it will save a lot of energy and greatly improve the efficiency of the load. Today, motors are widely found in various devices and their analysis involves the coupling of multiple physical fields. One of the most serious problems for some large motors is the heating problem, which generates various losses during motor operation, and these losses are eventually converted into thermal energy and emitted in the form of heat. The operating temperature of the motor has a great influence on the insulating material of the motor. Afterwards, a method of thermal-electromagnetic coupling simulation of the motor is carried out with a pump unit in the offshore oil platform as an example, and the magnetic line distribution, magnetic field density distribution cloud diagram and water pump temperature distribution of the motor are obtained, which are the basis of the electromagnetic design of the water pump and the design of the heat dissipation system.

Effect of Rotation Speed and Flow Rate on Slip Factor in a Centrifugal Pump

This work analyzes the causes of the slip phenomenon in the impeller on the basis of the internal flow mechanism. Detailed optical measurements of the flow inside the rotation passages of a five-bladed centrifugal pump impeller are obtained through particle image velocimetry (PIV). On the basis of experimental data, the deviation coefficient of slip velocity is proposed and then revised according to the slip factor calculation formula of Stechkin. Results show that, at the same rotation speed, the slip factor increases with the flow rate and reaches the maximum value at 1.0 QBEP flow rate. At different rotation speeds, the slip factor increases with the rotation speed and shows a relatively large variation range. Moreover, a revised slip factor formula is proposed. The modified model is suitable for the correction of slip factor at part-load flow rates and serves as a guide for the hydraulic performance design and prediction of centrifugal pumps.

Effects of Near-Wall Vortices on Wall Shear Stress in a Centrifugal Pump Impeller

Boundary layer separation and vortex formation cause unappealing deterioration of pump pressure head. The purpose of this research paper is to correlate formation of vortices with near-wall shear stresses resulting in a loss of pump pressure head. This phenomenon is observed at the centrifugal pump impeller tip at various flow rates and impeller rotational velocities through CFD (Computational Fluid Dynamic) analysis. This research paper investigates internal flow in a shrouded centrifugal impeller that is modelled under design flow rate conditions using ANSYS Fluent as its simulation bases solving built-in Navier-Stokes equation, and 𝑘 − 𝜔 SST turbulence model under steady conditions. Numerical results revealed an increase in wall shear stresses with increasing flow rate ranging from 314.2 Pa to 595.60 Pa at increments that pulsate per flow rate. Flow characteristics, such as evolution of vortices and flow turbulence enhance wall shear stresses increasing the wall skin-friction remarkably leading towards a loss in pressure head. This paper analyzes the vortices and turbulence in flow structures with regards to their influence upon the impeller performance.

Performance Analysis of Hydraulic Machines Using Impellers Made from Conventional Steel and 3D Printing Co-polymer

The research on hydraulic machines in industries is appropriate for many reasons. This paper deals with the creation of 3D prototypes of impellers of hydraulic machines printed from ABS plastic and verification of operating characteristics compared to conventional steel impellers of pump and also in turbine mode. The work includes properties, composition and verification of mechanical properties of ABS for different printing methods. Practical measurements of the specific geometry of the different 3D variants of the radial one-stage centrifugal impeller from ABS compared to metal wheels in the real hydraulic circuit are described. The results of the development of experiments demonstrate that the performance characteristics of the printed impellers of all variants have very similar functional values and very identical trends of functional curves of mechanical power and overall mechanical efficiency. At the same optimal speed, the highest performance and efficiency also as the metal wheels have been produced. It is clear from the results of work that prototypes produced by 3D printing achieve optimal performance parameter values in hydraulic testing and it is possible to successfully use this advanced technology in the verification of newly developed pumps, turbines and pumps turbines.

Analysis and Optimization of the Performances of the Centrifugal Compressor Using the CFD

Centrifugal compressors have been used in many areas of the machinery. The centrifugal compressor design is very complex, and a unique design system needs to be developed. A centrifugal compressor design system should be easy to use in interface and also flexible for inputs and outputs. The design tool also needs to be able to predicate the compressor performance in a fairly accurate level. In this study, we have developed a general analyses and optimization approach in the design and performance analysis of centrifugal turbomachines. This approach is based on different methods starting from a 1D approach up to the 3D study of the internal flow. It presents itself as a robust procedure for predicting and understanding the phenomena associated with the operation of turbomachines, but also for predicting performance. Current design system includes initial parameter studies, throughflow calculation, impeller design. The main improvements of the design system are adding the interface to allow users easy to use, adding the input and output capabilities and modifying few correlations. Current design system can predict the blade loading and compressor performance better compared with original design system. To check the aerodynamic appearance of the centrifugal compressor impeller blades, we must change the impeller dimensions and focus on changing axial length, but when changing the blade numbers, the model that improved efficiency and power at the same time introduced a design with a 0.274% and 10.735% improvement in each respectively in comparison to the initial impeller at the design point.

Development of a method for geometric modeling of centrifugal compressor impellers

The practice of designing centrifugal compressors in which impellers are the main components shows that there are reserves for their further improvement. One of the main reserves consists in improving flow conditions for the compressed medium in the compressor setting and, above all, in the impeller. A method of geometric modeling settings of the impellers of centrifugal compressors was proposed which involves the construction of meridional boundaries of impellers and the blade profile on an involute of the cylindrical surface of the outer radius of the impeller. The blade is represented by ruled surfaces. The outer boundary of the impeller is described by a curve in natural parameterization using cubic dependence of curvature on the arc length. Dependences and length of the arc are determined in the process of modeling the boundary based on the set source data. The problem is solved by minimizing deviations of intermediate curves from the boundary endpoint. The inner boundary is obtained as an envelope of circles inscribed in the meridional channel of the impeller. Radii of the circles are determined taking into account the flow areas of the channel. The midline of the blade profile on an involute of the cylindrical surface of the outer radius of the impeller is modeled using a curve that is presented in natural parameterization with quadratic law of curvature distribution. A computer code was developed in the Fortran Power Station programming environment that visualizes the obtained numerical results graphically on a computer display in addition to digital information on the modeled boundaries and the blade profile. Graphical results were presented. They confirmed the efficiency of the proposed method of modeling the settings of centrifugal compressor impellers. The method can be useful to offices involved in the design of centrifugal compressors

Large Eddy Simulation of Periodic Transient Pressure Fluctuation in a Centrifugal Pump Impeller at Low Flow Rate

This paper presents a large eddy simulation of a centrifugal pump impeller during a transient condition. The flow rate is sinusoidal and oscillates between 0.25Qd (Qd indicates design load) and 0.75Qd when the rotating speed is maintained. Research shows that in one period, the inlet flow rate will twice reach 0.5Qd, and among the impeller of one moment is a stall state, but the other is a non-stall state. In the process of flow development, the evolution of low-frequency pressure fluctuation shows an obviously sinusoidal form, whose frequency is insensitive to the monitoring position and equals to that of the flow rate. However, inside the impeller, the phase and amplitude in the stall passages lag behind more and are stronger than that in the non-stall passages. Meanwhile, the strongest region of the high-frequency pressure fluctuation appears in the stall passages at the transient rising stage. The second dominant frequency in stall passages is 2.5 times to that in non-stall passages. In addition, similar to the pressure fluctuation, the evolution of the low-frequency head shows a sinusoidal form, whose phase is lagging behind that by one-third of a period in the inlet flow rate.

Effect of hub inclination angle on internal and external characteristics of centrifugal pump impellers

The flow characteristics at a centrifugal pump impeller are significantly affected by the hub inclination angle (HIA). The large eddy simulation turbulence model is employed to simulate the centrifugal pump impeller internal flow at two HIA values under design (1.0 Qd) and off-design (0.55 Qd) conditions. The reliability of the simulation results is verified by comparing the results at a 0° impeller HIA and experimental data. The results show that an increase in HIA has a positive effect on the head of the centrifugal pump impeller, which exhibited a 5% relative deviation between HIA values of 0° and 40°. Under design conditions, there is a good and similar impeller internal flow at the two HIA values. Under off-design conditions, the relative velocity of the 40° impeller HIA channel inlet is 11.7% higher than that of the 0° impeller HIA, which reduces the flow attack angle and effectively suppresses stall. Moreover, for the 0° impeller HIA, fluctuation caused by the stall cells on the blade suction surface is observed, whereas such a phenomenon is not observed for the 40° impeller HIA.

A case study on 3D scanning, digital reparation and rapid metal additive manufacturing of a centrifugal impeller

This paper demonstrates a comprehensive method for digital restoration and rapid manufacturing of a fully functional mechanical component. A damaged centrifugal impeller of an automotive engine was reverse-engineered via a 3D laser scanner, with which the 3D model of the investigated object was digitally captured. Utilizing advanced design software and surface modelling, the missing fragments were restored and the impeller’s 3D digital model was reconstructed. Metal additive manufacturing technology and more specifically the Selective Laser Melting (SLM) technique was employed to construct a functional metal impeller. Stainless steel 17-4 PH powder was used as the printed material. To ensure the exploited powder was appropriate for the part to be manufactured, we applied characterization of the feedstock material was conducted through two different characterization methods, i.e. granulometry and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). Furthermore, Surface Distance Maps (SDM) were calculated to correlate the geometrical deviations between the physical 3D printed part and the digital model in order to examine the accuracy of the applied method.

Influence of Impeller Gap Drainage Width on the Performance of Low Specific Speed Centrifugal Pump

The centrifugal pump is one of the most important pieces of energy-consuming equipment in various hydraulic engineering applications. This paper takes a low specific speed centrifugal pump as the research object. Based on the research method combining numerical calculation and experimental verification, the influence of the gap drainage structure on the performance of the low specific speed centrifugal pump and its internal flow field distribution were investigated. The flow field inside the low specific speed centrifugal pump impeller under different gap widths was studied. The comparison between the numerical calculation results and the experimental results confirms that the numerical calculations in this paper have high accuracy. It was found that the gap drainage will reduce the head of the low specific speed centrifugal pump, but increase its hydraulic efficiency. Using a smaller gap width could greatly improve the performance of the low specific speed centrifugal pump on the basis of a slight reduction in the head. The high-pressure leakage flow at the gap flows from the blade pressure surface to the suction surface can effectively suppress the low-pressure area at the impeller inlet. The flow rate of the high-pressure leakage flow increases with the gap width. Excessive gap width may cause a low-pressure zone at the inlet of the previous flow passage. These results could serve as a reference for the subsequent gap design to further improve the operating stability of the low specific speed centrifugal pump.

Transient simulation of electrochemical machining processes for manufacturing of surface structures in high‐strength materials

AbstractElectrochemical machining (ECM) is a method for removing metal by anodic dissolution. At the interface between the workpiece surface and an electrically conductive fluid (electrolyte), the material is dissolved locally without direct physical contact to the cathodic tool. Due to the force‐free nature of the process, ECM is used for machining high‐strength or hard materials, such as titanium aluminides, Inconel, Waspaloy, and high nickel, cobalt, and rhenium alloys. However, determining suitable process parameters remains challenging due to their interacting effects on working distances during the machining process. Therefore a simulation‐based approach to process design substantially reduces resource and time investment to achieve the desired geometry of the finished part. This methodology requires data about the materials electrochemical properties, such as removal velocity and current efficiency, which have to be obtained experimentally. In this study, a methodology for acquiring and processing this data as well as the development of multiphysics simulation models is presented exemplarily for manufacturing a centrifugal impeller with a diameter of 14 mm consisting of the nickel alloy Inconel 713C for use in turbomachinery.

Advances in Centrifugal Compressors

In the case where flow passes through a straight pipe to enter a centrifugal compressor the flow is straight, uniform and has no vorticity, ie swirling motion, so the swirl angle α1 = 0° as illustrated. As the flow passes through the centrifugal impeller, the impeller forces the flow to spin faster as it gets further from the rotational axis. According to a form of Euler's fluid dynamics equation, known as the pump and turbine equation, the energy input to the fluid is proportional to the flow's local spinning velocity multiplied by the local impeller tangential velocity. In many cases, the flow leaving the centrifugal impeller is travelling near the speed of sound. It then flows through a stationary compressor causing it to decelerate. The stationary compressor is ducting with increasing flow-area where energy transformation takes place. If the flow has to be turned in a rearward direction to enter the next part of the machine, e.g. another impeller or a combustor, flow losses can be reduced by directing the flow with stationary turning vanes or individual turning pipes (pipe diffusers). As described in Bernoulli's principle, the reduction in velocity causes the pressure to rise.

A New Approach to Modeling Slip and Work Input for Centrifugal Compressors

Abstract A new method of modeling slip factor and work input for centrifugal compressor impellers is presented. Rather than using geometry to predict the behavior of the flow at the impeller exit, the new method leverages governing relationships to predict the work input delivered by the impeller with dimensionless design parameters. The approach incorporates both impeller geometry and flow conditions and, therefore, is inherently able to predict the slip factor both at design and off-design conditions. Five impeller cases are used to demonstrate the efficacy of the method, four of which are well documented in the open literature. Multiple implementations of the model are introduced to enable users to customize the model to specific applications. Significant improvement in the accuracy of the prediction of slip factor and work input is obtained at both design and off-design conditions relative to Wiesner's slip model. While Wiesner's model predicts the slip factor of 52% of the data within ±0.05 absolute error, the most accurate implementation of the new model predicts 99% of the data within the same error band. The effects of external losses on the model are considered, and the new model is fairly insensitive to the effects of external losses. Finally, detailed procedures to incorporate the new model into a meanline analysis tool are provided in the appendices.

Design for New Type Centrifugal Fan and Passageway of the Air Conditioner Indoor Unit

This paper introduces a design flow for the low-speed high-efficient centrifugal impeller applicable to the new type indoor hanging unit, with the matching inlet collector and non-uniform outlet diffusion passageway being also designed. Under the influence of the inlet collector, the attack angle deviation and air intake distortion occur to the centrifugal impeller. While the unsteady pressure fluctuation generated by the non-uniform diffusion passageway can also affect the flow in the passage of the upstream blades. The preliminary design and optimization of the above three parts are described in this paper based on the needs of overall design, the outlet flow rate is also increased by adjusting the static pressure distribution in the inside centrifugal impeller, consequently the flow separation generated by the guide blade in the diffusion passage is improved and the outlet uniformity of the diffuser is enhanced. Finally, the feasibility analysis for the overall design is performed in this paper, to ensure the design requirements can be met.

The friction torque loss for flows in narrow gap between a rotating disk and a stationary disk in a centrifugal impeller

The friction torque loss for flows in narrow gap between a rotating disk and a stationary disk in a centrifugal impeller

Investigation of the operating process of a high-pressure centrifugal pump with taking into account of improvement the process of fluid flowing in its flowing part

Centrifugal pumps are used in most industries. In particular, they are effectively used in the technological processes of oil production to create reservoir pressure at oil fields. Due to increasing demand for petroleum products, there is a need to improve such pumps to increase reservoir pressure by increasing their pressure. The research considered the possibility of improving the centrifugal pump impeller design by changing its blade system. It is theoretically possible to increase the pump head by changing the blade outlet angle at the impeller outlet β2 to 75°. The design of additional wedge-shaped blades of the second tier of the impeller was developed to reduce some additional hydraulic losses zones. They made it possible to stabilize the fluid flow in the impeller intervane channels, to reduce additional hydraulic losses. In the research, the impeller head was increased up to 26.7% for the proposed design impeller compared to the standard one. The research was performed with a comprehensive analysis of the pump installation life cycle cost. Thus, the development of new ones and the upgrading of pumping installations rooted in the industry with the aim of increasing the head is possible while achieving the minimum pump installation life cycle cost.

Conversion from Free-Form Surface to Ruled Surface of Centrifugal Compressor Impellers

At present, there are several conversion methods exist, which are based on cutter fixing at a point on the blade surface to swing around the blade surface, searching for a position where the error between the cutter and the free-form surface is the smallest. They rarely take into account the benefit from searching cutter position along the blade’s tangential direction, and ignore the possible optimal cutter position from such search. In this paper, we propose a new cutter search method that allows this tangential swing in additional to meridional plane swing of the cutter in searching for the optimal position of the cutter. The mathematics of the method is described, and two different centrifugal compressor impellers with free-form blade surfaces are employed as test cases. The results show that this method can well convert the free-form surfaces of the impeller blades into ruled surfaces.