have established a theory of boundary vorticity dynamics and successfully applied this theory to the aerodynamic diagnosis and optimization of airfoil profile . After leading edges change, the meridional flow should be recalculated. Fig. The fittest ones will have the most changes to exist in the next generation or become the parents of the next generation. (See Flow Direction below for more information about flow.) These regions are unfavorable to transfer the energy to fluid, especially the region near trailing edges, since the product of negative and the square of r (the radial position) contributes to generate positive moment. Three impeller designs: (l to r) open, semi-closed, and enclosed (shrouded). This link contains an excellent mixing impeller calculator as well as raw formulas for many of the parameters listed above. Impeller types can be radial, mixed flow, axial and peripheral and are selected on the basis of the pump design and the application. Vortex impeller Impellers may be manufactured, tested, and used based on various industry standards. As it also can be seen from these distribution figures, separation points in the blade surfaces of these impellers where flow separations occur are nearly at the same position on the blades, where low values exist. They convey pumped media in the direction along the revolving axis of the impeller. Iterations are needed to insure that the wrapping angles on each streamline after leading edges changing are really equal to the required ones. After the impeller media enters the eye and makes its way through the vanes it is drawn into a nozzle and expelled. Radial impellers — which typically have rectangular vanes — are used when the tank media is excessively viscous or consists of two immiscible materials. Applying Bernoulli equations along each streamline on the blade surfaces. ACCESS
Because centrifugal pumps are also classified in this manner, the impeller selection depends upon matching the pump's flow characteristic to that of the impeller. Impeller design with suppressed secondary flows. Axial flow impellers are used at high speeds to promote rapid dispersion and are used at low speeds for keeping solids in suspension. Impellers can be broadly classified into two different designs: open and closed. Notify me about educational white papers. Because the impeller is closed it is more difficult to access for routine maintenance, however; because closed impellers actually require more maintenance due to the need to periodically replace wear rings, they carry higher maintenance costs but are slightly cheaper to run over time regardless of this fact. Pump need not be disassembled for adjustment or maintenance. Through this, the comparisons between different design parameters can be more efficiently and accurately conducted. Secondary flows in a centrifugal impeller are well acknowledged to drive the high loss fluids in the viscous layer toward the shroud/suction surface corner region. Search manufacturer catalogs by these specifications: Axial flow impellers move media parallel to the impeller. A properly designed impeller optimizes flow while minimizing turbulence and maximizing efficiency.. This will reduce the flow area which may bring about more losses because of the rising flow velocity and will also cause energy losses due to viscosity of flow medium. But the negative region is a little small which will result in insufficient moment transfer. Another 5 impellers with the same parameters were also designed by using single arc, double arcs, triple arcs, logarithmic spiral, and linear-variable angle spiral … For BVF diagnosis, it is sufficient to focus only on. The rotation of the impeller is in the anticlockwise direction. Let’s start our investigation of centrifugal pump efficiency with the impeller. For study of the hydraulic performance of these 6 impellers, the governing equations of these flow fields in impellers are solved by commercial CFD code FLUENT to predict three-dimensional turbulent fluid flow. (While the casing may also increase in size due to ambient heat, it is often manufactured using different materials than the impeller and therefore may expand at different or unpredictable rates.) – efficiency can be maintained through frequent vane adjustment. Genetic algorithm is first presented by John Holland in the early 1970s and it is currently the most popular design optimization algorithm. Industrial Computers and Embedded Systems, Material Handling and Packaging Equipment, Electrical and Electronic Contract Manufacturing. Given the relationship between blade wrapping angle and length of meridional streamline, camber lines can be obtained by solving the integral of wrapping angle function according to a given relative velocity distribution along the streamline: Since the leading edges are concerned with cavitation and instabilities of head-capacity characteristic curve of the pump, during the design process more attention should be paid to them. The discretization of the calculation domain is done keeping the balance between calculation time and the accuracy order of the simulation of the flow structure. The impeller of a centrifugal pump can be of three basic types:. In recent years, many modern pump design methods have been developed and with the help of some software such as TURBOdesign, CFTurbo, and Pcad, pump design and optimal processes become simpler. And compared to other impellers, the distribution of on optimal impeller blade surface is more uniform, which can reflect that the GA optimal design method is available and can be used to solve the desired object function optimization problem and the estimated calculation is feasible. Power number is a value specific to mixing impellers which describes the impeller's power consumption. Firstly, averaged fields are studied in order to evaluate the overall treads. FREE
This study focuses on the p ressure distribution of the centrifugal pump impeller by var ying the rotation speed at Open impeller. Please try again in a few minutes. Z. Zhang, L. Chen, X. Zhou et al., “Hydraulic design, numerical simulation and BVF diagnosis of high efficiency centrifugal pump,”, S. Kaewnai, M. Chamaoot, and S. Wongwises, “Predicting performance of radial flow type impeller of centrifugal pump using CFD,”, M. Nataraj and R. Ragoth Singh, “Analyzing pump impeller for performance evaluation using RSM and CFD,”, Z. Wang, J. Zheng, L. Li, and S. Luo, “Research on three-dimensional unsteady turbulent flow in multistage centrifugal pump and performance prediction based on CFD,”, Y. Zhang, X. Zhou, Z. Ji, and C. Jiang, “Numerical design and performance prediction of low specific speed centrifugal pump impeller,”, X. Zhou, Y. X. Zhang, Z. L. Ji, and L. Chen, “Hydraulic design and performance analysis of low specific speed centrifugal pump,”. The design requirements called for improving the efficiency of lift fan while meeting the set design criteria for the output fluid power delivered by the impeller. It can be concluded that the blade profile formed with more arcs will have less angle changing rate and may have better performance. A. Goto, M. Nohmi, T. Sakurai, and Y. Sogawa, “Hydrodynamic design system for pumps based on 3-D CAD, CFD, and inverse design method,”, V. A. Grapsas and S. John, “Anagnostopoulos, Dimitrios E. Papantonis. At each point on the blade surface, the tangent vector of streamline , the tangent vector of cross-section line , normal vector direction from an orthogonal curve coordinate, and the value of can be calculated using the following expression: The media becomes even more pressurized as it is discharged from the impeller and out of the pump orifice. In addition, no simple mathematic model can be established to well predict the performance of impellers at present and by using numerical procedures it is possible to predict the performance curve of impellers with enough accuracy. For logarithmic spiral (Model 4), . The table below describes other advantages and disadvantages of open impeller designs. I cut the curved vanes out of a solid block of maple on the bandsaw. Therefore, many studies have sought to find optimal designs of slurry pumps that are efficient and have less wear. Impellers are frequently used in agitation tanks as a means to mix fluids and slurries. The geometric design of With the consideration of reducing the BVF peak values on the blade surfaces, the mathematical model is used as follows. The pressure-velocity coupling is calculated through the SIMPLEC algorithm and the pressure correction under-relaxation factor is set to 1.0. They are the most popular impeller for large pumps transferring clean liquid as they are prone to clogging when in contact with solids. The Optimal Hydraulic Design of Centrifugal Impeller Using Genetic Algorithm with BVF, College of Mechanical and Transportation Engineering, China University of Petroleum, Beijing 102249, China. The estimated performance of 6 impellers at design point. WORLD'S
The operation condition of impeller (flow rate) can be changed through modifying the axis velocity magnitude at inlet boundary. Flow direction of three different pumps/impellers. Through this method, the free geometric parameters of leading edges of blades can be reduced and connection between the position of leading edge and trailing edge by wrapping angle is obtained, which brings a more convenient way to design the leading edge. For these two, blade angle will fulfill the following expression at any points on profile line: In this method, the estimated boundary vorticity flux values on blade surface are used in the evaluation function of genetic algorithm. where the right-hand side integral can be approximated by a summation over the radial flow rates at all grid cells facing the inlet or outlet of the impeller. Axial flow pitched blade impellers have one or more paddles. Xin Zhou, Yongxue Zhang, Zhongli Ji, Hucan Hou, "The Optimal Hydraulic Design of Centrifugal Impeller Using Genetic Algorithm with BVF", International Journal of Rotating Machinery, vol. TO THE
The flow procedure of GA hydraulic design is shown in Figure 1. Since is a direct consequence of no-slip wall condition, it is only in viscous flow that is available; however, when the Reynolds numbers are large enough (it usually happens in the flow of impeller passages), can be well estimated from an inviscid flow solution. Impellers are integral components in centrifugal pumps and vacuum pumps, among other pumping devices. The meaning and its bounds of each variable are listed in Table 1, and their bounds are used to design an impeller with 200 m3/h capacity and 20 m head. Its job is to take the flow from the impeller and direct the slurry into the pump discharge. With the purpose of using efficient and simple inviscid flow model, some assistance from boundary vorticity dynamics is introduced and boundary vorticity flux (BVF) is used to diagnose the flow in impeller channels. Radial flow impeller types include: Axial impellers are suitable for homogenization and mixing which requires bulk motion. Reverse engineering using 3D scan data is the most efficient way to generate a CAD model from a physical object that has any kind of complex or ... Impeller. FLUENT software is adopted to solve the fully 3D incompressible Navier-Stokes equations to simulate the inner flow field by assuming that the fluid is steady, viscous, and incompressible. Genetic algorithm (GA) is a global search technique that mimics Darwin’s theory of biological evolution used in computing to find exact or approximate solutions to optimization and search problems, which is inspired by evolutionary biology such as inheritance, selection, crossover, and mutation. The secondary flow phenomena have important effects on the efficiency and stability of the impeller. Open design allows for ease of cleaning and clearing of clogs. In Table 4, it is observed how the head coefficient and hydraulic efficiency reach an asymptotic value as the number of cells increases. Open — While slightly less efficient, open impellers work well for slurry that contains a combination of fluids, solids, and gases. There are several advantages and disadvantages associated with them, of which the most important points are efficiency and thrust balancing. For these reasons computational fluid dynamics analysis is currently being used in hydrodynamic design for centrifugal impellers [13–15]. Backward inclined or backward curved blades are single thickness with 9 to 16 blades curved or inclined away from the direction of rotation. Unlike classical methods, it is not affected by local optima. A properly designed impeller optimizes flow while minimizing turbulence and maximizing efficiency.. And after that the meridional section profile of impeller can be generated with curves. Comparison of closed vs. open impellers. In order to design an efficient centrifugal impeller, researchers have studied the flow law of gas in the impeller from various angles, and sought the best impeller design method. When fluid or gas media enters an impeller pump, it becomes trapped between the impeller vanes and the pump wall and increases in velocity as it moves from the impeller eye (center) toward the outside diameter of the impeller. An agitation tank with a central radial impeller. A wealth of experience of centrifugal pump impeller hydraulic design is accumulated and the efficiency of centrifugal pump has reached a considerable level [1, 2]. Mutation, crossover, and inversion operators will be used to generate new chromosomes in the next generation. Chou Memorial Lecture,” in, Y. The table below lists advantages and disadvantages of enclosed impellers. Z. Wu and J. M. Wu, “Boundary vorticity dynamics since Lighthill's 1963 article: review and development,”, Z. J. Wu, L. R. Roach, F. C. Lo et al., “Aerodynamic diagnostics and design based on boundary vorticity dynamics,” in, Y. Zhang, X. Luo, H. Ding, X. Wang, and H. Xu, “Design optimization of the impeller for a high specific-speed pump based on BVF diagnosis,”, J. These distributions are obtained by calculating the expression , after CFD simulation. I agree to receive commercial messages from GlobalSpec including product announcements and event invitations,
Comparisons of flow fields in these impellers and prediction of their hydraulic performance are also presented. Compared to other impellers, the pressure increasing along the flow channel is more preferable and the pressure distribution around the exit of impeller is shown to be more uniform, which will cause less loss. as well as subscriptions and other promotional notifications. An evaluation function is used to calculate the “goodness” of each chromosome and a fitness function is defined over the representations and measures the quality of these solutions. Conducting these processes in which extremely advanced measuring techniques or even visualization techniques should be employed is often time and resources consuming. An impeller as a component of a centrifugal pump. Any changes in the location and magnitude of BVF distribution can be accounted as redistribution of pressure on surfaces. Given design parameters, the desired optimal centrifugal impeller can be obtained after several iterations by this method. For outlet, the outflow is given as boundary condition. While open impellers may be manufactured using soft materials to prevent sparks, these materials are typically unsuitable for the abrasive media pumped in oil and gas applications. These ranges are approximate, without clear-cut demarcations between them. Therefore, a typical centrifugal heat transfer pump operating at 600° F would experience a shaft diameter increase large enough to force the impeller vanes to make contact with the casing, causing sparks and damage to the impeller. And if the following notation is used, Special care should be taken in the regions near the blades. The counterweight to the increased computing requirements will be used as an efficient evaluation model. Zhang et al. (For larger image, click on Pump-Zone link below.). When the procedure of blade drawing has been finished, the value of function , where is the streamline length along the flow direction and the suffix means th streamline on the blade, at which point on the blade profile can be gained (define as the wrapping angle calculated at each streamline on the blade). Using Reynolds averaged N-S equations with a RNG k-ε two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the flow channel between blades of 6 designed impellers by CFD code FLUENT, the investigation on velocity distributions, pressure distributions, boundary vorticity flux distributions on blade surfaces, and hydraulic performance of impellers was presented and the comparisons of impellers by different design methods were demonstrated. The affinity laws tell us quite a bit about the inner workings of an impeller. The modeled boundary conditions are those considered most physically meaningful for flow simulations and those that give a flow solution restricted by them. By fitting the vane ends very close to the pump casing, the open impeller is able to prevent large amounts of fluid or gas from recirculating back through the eye. As shown in the graph below, closed impellers (dark blue line) are more efficient than open designs (light blue line) and are much more suitable for explosive environments. Mixing impellers typically employ an open design and are fitted to a central shaft which is placed in the center of the tank. This study used Eulerian-Eulerian mixture model to simulate the solid-liquid two-phase flow of quartz sand and water in a slurry pump. The flows in these 6 designed impellers passages with the same volute have been simulated at the design point ( m3/h). This equation represents one-dimensional flow theory design at the condition , two-dimensional flow theory design with at the condition , and two-dimensional flow theory design with at the condition . Derived from idea of combining the advantages of two-dimensional hydraulic design theory, genetic algorithm, and boundary vorticity flux diagnosis, an optimal hydraulic design method of centrifugal pump impeller was developed. Companies affiliated with GlobalSpec can contact me when I express interest in their product or service. Image credit: Engineer's World. It can be clearly seen that there is an axial vortex in impeller channel near suction surface of blade of Model 1, Model 2, and Model 5, respectively, which means that flow separation happens on this region. Propellers commonly refer to devices which move an attached object. Z. Wu and J. M. Wu, “Vorticity dynamics on boundaries,”, J. In this paper, an optimal hydraulic design method of centrifugal pump impeller which combines the advantages of two-dimensional hydraulic design theory, genetic algorithm, and boundary vorticity flux diagnosis is presented. The low pressure regions may be mainly caused by incidence loss due to mismatch of hub and the position of leading edge. Another 5 impellers with the same parameters were also designed by using single arc, double arcs, triple arcs, logarithmic spiral, and linear-variable angle spiral as blade profiles to make comparisons. More specific details of these procedures can be found in paper [16, 17]. For linear-variable angle spiral (Model 5), International Journal of Rotating Machinery, Angle between meridional streamline and vertical line, Angle between quasiorthogonal line and axis. fully used the advantage of BVF to detect the area during blade design and modified the blade profile under the guidance of flow theory of impeller . © Copyright 2020 GlobalSpec - All rights reserved. The development of CFD that compute the flow field inside the impeller has been a breakthrough in the field of design, but it do not automatically realize an optimal design by itself. While all impellers consist of similar design elements as described above, they may perform slightly different operations depending upon their intended application. Since inviscid flow calculation is enough to obtain BVF information that is needed to check the performance of the designed blade, time consuming 3D CFD simulations are not inevitable and localized key regions will be more easily recognized as shown in Figure 5 (it shows that BVF peaks exist around trailing edge of blade). We are committed to sharing findings related to COVID-19 as quickly as possible. Centrifugal Most centrifugal motorized impellers use backward curved (BC) blades because they generate significant static pressure, operate silently, and provide the highest efficiency of all centrifugal fan designs. This adjustment must be done at operating temperature, which may be hazardous.