Front View of Pressure Distribution at 1, Fig. Centrifugal Fan Design A typical input for a detailed simulation analysis is a watertight (wet) surface model in form of STL surface. Yu-Tai Lee, Vineet Ahuja, Ashvin Hosangadi, Michael E. Slipper, Lawrence P. Mulvihill, Roger Birkbeck, Roderick M. Coleman, "Impeller Design of a Centrifugal Fan with Blade Optimization", International Journal of Rotating Machinery, vol. The lift-side static and total pressures, along with their efficiencies are also tabulated. The optimization calculation was to minimize this objective function. The predicted ShaftPWR for each impeller is lower than the targeted ShaftPWR (or PWRref). Oxford: Elsevier (2006). However, when the flow rate is very high, single-suction will not be enough. The 2D blade cross-section design described in the previous section was performed in a relatively conservative manner due to an “unknown” coupling effect from the downstream volute. It can also be observed that the efficiency of the impeller increases as the rotation speed increases. There existed a sudden pressure drop in all three fans at the point the fans went into stall conditions. There are two other parameters related to the lift-side performance. The uncertainty of the measured pressure was estimated to be within 0.25% [8] at design conditions. In addition, the fan total-to-total efficiency is calculated in Table 2 using (8) and (9). Table 1and Figure 3show the main specifications and forms of the two optimized design impellers (OPT1 and OPT2), and a baseeline impeller, respectively. In addition, the period of the design phase was limited. Conversely, for a fixed impeller width, altering the blade geometry can play an important role in lowering shaft power and increasing impeller efficiency. These simulations of centrifugal pumps are strongly related to cavitation flow phenomena, which may occur in either the rotating runner-impeller or the stationary parts of the centrifugal pumps. However, the reliabilities of the individual components, when placed in the overall configuration, may not remain the same as when the components are considered separately. The matching volute design plays an important role in determining fan efficiency, which is improved by 1.2% for the new fan over the baseline fan. Although the gap flow alleviates the shroud flow separation, it affects the blade trailing-edge flow, particularly at the volute tongue locations. In this paper, a systematic numerical study was carried out of the aerodynamic characteristics of the existing impellers. for determining performance of a centrifugal … The grouping of control points was implemented in the spanwise direction to ensure that the integrity of the 2D shape was maintained. Figure 3 depicts the blade (left figure) and shroud (right figure) arrangements for the 14-bladed B#1 impeller in black and the 12-bladed B#2 impeller in gray. Blade trailing-edge shape control (or blade steering) effectively modifies the impeller exit flow and reduces power (from 0.945 to 0.896 PWR. 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 … Fig. Both existing impeller's blades were primarily 2D blades, that is, the leading and trailing edges at hub and shroud started at the same radii. The study revealed that although the existing impellers were high performing to start with, there was some margin for improvement. Comparisons shown in Figure 21 include the original design required pressure rise, model test data, and CFD predictions for the full-scale (FS) and model-scale (MS) fans. The grids were then passed to CRUNCH CFD and the performance of the altered designs was evaluated. The result shows that a grid density of 250,000 cells or more for each impeller blade passage is adequate for a predicted power with an error of 0.5% (mostly dependent on the grid topology rather than the grid density) or less. (ii) The shroud gap between the bellmouth and the shroud carries less than 1% of the inflow back from the volute to the impeller for the current fans. Probabilistic design is done by explicitly accounting for the uncertainties in the different variables and their influence on structural performance. The performance test set-up was constructed using the American National Standards Institute (ANSI)/Air Movement and Control Association (AMCA) standards [8] as a reference. The NEW impeller has the smallest performance variation in almost all the parameters predicted, particularly for the volute losses as pointed out previously. GRIDGEN was used to generate the initial CFD grid for the original blade shape and subsequent grids were automatically generated with shape deformation propagating through the grids. and all of the simulation results were converged within the range. This reduction in power agrees with the 8.7% reduction obtained from the CFD predictions. This results in the following nondimensional parameters: Liftflowcoefficient=lift1/42=0.2014,(1)Liftstaticpressurecoefficient=lift2=0.3175,(2)Powercoefficient=ShaftPWR1/423=0.1892,(3) Due to the time constraint during the design phase, a total of 48 designs were analyzed during the design iterations. Design variables, such as blade number and blade angles defining the pump impeller blade shape were selected and a threelevel full factorial design approach was used for effic- iency enhancement. At the design point, 57% of the fan air flows through the lift diffuser to maintain the required lift pressure. The continuity and Navier-Stokes equations with the k-e turbulence model and the standard wall functions were, Join ResearchGate to discover and stay up-to-date with the latest research from leading experts in, Access scientific knowledge from anywhere. Although all three investigations [5–7] found that their prediction results agree with the measurements, Karanth and Sharma [7] revealed the presence of an optimum radial gap (or the interacting region) which could provide lower interaction losses. A total drop of five to six percentage points in the impeller efficiency with the volute feedback is considered. The measured lift-side static pressure coefficient versus the lift-side flow coefficient is plotted in Figure 21 for the three impellers. The current measurements were limited to a maximum impeller speed of 5212 rpm. The double-discharge volute casing is a structural constraint and is maintained for its shape. Rao provides a thorough grounding of the mathematical principles for setting up finite element solutions in civil, mechanical, and aerospace engineering applications. (iv) The comparisons between the CFD predictions and measurements confirm that the existing fan was overpowered at design, which enabled a new impeller design with a lower power requirement. Note that the current volute inlet has a sudden expansion (shown in Figure 3) from the impeller exit versus Kim’s volute which has a smooth connection between the volute and the impeller. A schematic of the design optimization framework is shown in Figure 10. The optimization process, including the comparison of the surrogate models, can provide reference for the optimization design of other pumps. and compared among the three impellers. The optimization improves the impeller efficiency from 92.6% to 93.7%. Some small modifications were made to the 2D blade through a steering process followed by the construction of a 3D blade by sweeping the 2D sections. The widths for the two existing impellers shown in Figure 2 are 0.1207 D and 0.1350 D, respectively. Variables that represent deformation of the blade shape by moving the control points were passed by the GA to SCULPTOR where the shape modifications and grid alterations were performed. Even though the steer blade-1 required much lower shaft power, it unfortunately delivered much less head and output power. Using the developed design strategy, the following results are identified. Keyword: CFD, Design, Impeller, Pump, Radial Flow, Vane. For example, Kaupert and Staubli [2] recorded strong blade loading fluctuations as the blade passed the volute tongues on a double spiral volute, particularly at below design flow rates. Performance of the impellers was compared based on inlet and outlet power, impeller efficiency, pressure distribution, and static head pressure produced. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Isometric View of Inlet Boundary Condition, Fig. As a result, the performance of the impeller increases as the efficiency increases. Impeller design is the most significant factor for determining performance of a centrifugal pump. the Design of Radial Flow Pump Impeller through CFD Analysis. The B#2 and NEW impellers suffer about 0.5% reduction in fan efficiency due to the gap-affected impeller exit flow [17] into the volute which induces impeller blade trailing-edge flow recirculation, as shown in Figure 19. Design considerations for high pressure ratio centrifugal compressor have been systematically studied by many researchers for decades. This suggests that conventional design methods such as a streamline curvature or an inviscid calculation method would be inadequate in addressing any aerodynamic improvements to the existing impellers. The new 3D blade generated high head of 1.548 ref versus 1.471 ref with a higher efficiency of 95.08% versus 93.66% at the expense of a higher shaft power of 0.968 PWRref versus 0.936 PWRref. Centrifugal pump usage has increased over the past year due to its importance and efficiency. 5. The measured power reduction for the new impeller is 8.8% lower than the baseline. For model Reynolds number (Re) to be similar to the full-scale value, the model test would ideally be run at 5-times the full-scale speed of 1692 rpm. (i)The impeller-only calculations for the baseline B#1 impeller and the reference B#2 impeller indicate that the total efficiencies of both existing impellers are high (above 92%). Given the high performance of the baseline impeller, the redesign adopted a high-fidelity CFD-based computational approach capable of accounting for all aerodynamic losses. This approach has been used to develop a set of load and resistance factors instead of just a single safety factor to address all the uncertainties. The LNG centrifugal compressors typically use a combination of 2D and 3D impellers. The redesign effort was geared towards meeting the design volute exit pressure while reducing the power required to operate the fan. (iii) The test data of the lift-side pressure rise for the existing and new impellers agrees well with the CFD predictions based on the model Reynolds number. Impeller design is the most significant factor for determining performance of a centrifugal pump. The prediction results for all these later modifications are also plotted in Figures 12 and 13 as “Non-GA” points. Graph of Pressure vs Impeller Rotation Speed, Impeller Power and Efficiency Calculation, Table 4 below shows the power at the inlet and outlet of the impellers, and the, with 24.67m of static head. Front View of Pressure Distribution at 1750, Fig. 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 . The simulation on vane profile was solved by Navier-Stokes equations with modified K-turbulence model in the impeller. Its function is to transport liquid from one place to another using energy applied to the pump. After the final 3D modification, the fitness and efficiency are further improved from those obtained for the 2D blade design by GA. The optimization improves the impeller efficiency from 92.6% to 93.7%. These results led to the decision to choose the 11-bladed 0.0476 shroud profile impeller configuration. The impeller design package includes a geometry modelli procedure, aerodynamic analysis, stress analysis, and the direct generation of data for … where lift, ()lift, , , and are defined as the lift flow rate, fan lift discharge static pressure, fan tip diameter, fan tip speed, and air density, respectively. In other words, the NEW impeller generates less total head with the same width as the B#1 impeller; however, with increased width, the NEW impeller is able to produce the same total head as the B#1 impeller. The process is accomplished by convergence of key quantities such as the total pressures and mass flow rates at the impeller inlet, interface, and volute outlets. The amplitudes of the pressure fluctuation at the inlet and outlet were lower than that of the impeller-volute coupling interface, and the high-frequency components at the inlet and outlet were fewer than that of the impeller-volute coupling interface. The convergence of the solution is determined by the variation of the calculated impeller torque and the mass-averaged total and static pressure variations at the inlet and outlet planes. Compared with the simulated efficiency of the original pump, the optimization increased efficiency by 8.34% under the design point. (iv)Blade trailing-edge shape control (or blade steering) effectively modifies the impeller exit flow and reduces power (from 0.945 to 0.896 PWRref or a 31.3 kW reduction) while maintaining efficiency. Park, K. Ahn, and J. Baek, “Improvement of the performance of a centrifugal compressor by modifying the volute inlet,”, Y. T. Lee, “Impact of fan gap flow on the centrifugal impeller aerodynamics,”, A. Hildebrandt and M. Genrup, “Numerical investigation of the effect of different back sweep angle and exducer width on the impeller outlet flow pattern of a centrifugal compressor with vaneless diffuser,”. Given design parameters, the desired optimal centrifugal impeller can be obtained after several iterations by this method. © 2008-2020 ResearchGate GmbH. Therefore, this paper proposes that the reliability of the structure be explicitly satisfied at the component level as well as at the system level during design. A centrifugal pump is common in process plants, usually in large numbers. fluid dynamics (CFD) has been used. Finite Element Analysis is an analytical engineering tool originated by the Aerospace and nuclear power industries to find usable, approximate solutions to problems with many complex variables. Since the volute outer casing configuration is a structural constraint, it stays the same for all fans, the volute flow field and its feedback to the impeller are modified for changes in the impeller exit conditions and the volute-side’s bellmouth and shroud shapes. (RANS) equations with standard SST (Shear Stress Transport) turbulence models. This simplification is referred to as the frozen impeller approach. Model-fan measured data was used to validate CFD predictions and impeller design goals. Isometric View of Fixed Boundary Condition. DESIGN AND CONSTRUCTION OF CENTRIFUGAL PUMPS Basic Pump Components A typical Centrifugal Pump is shown in Figure 1. The new edition includes examples using modern computer tools such as Matlab, Ansys, Nastran, and Abaqus. The developed redesign procedures established based on the findings from the assessment of the existing impellers are herewith provided below. The two main components of a centrifugal blower are the impeller and the casing. The calculated shaft power, total head, and efficiency are 0.870 PWRref, 1.376 ref, and 93.87% for the steer blade-1; 0.896 PWRref, 1.414 ref, and 93.8% for the steer blade. The use of streamline curvature or potential-flow/Euler codes would not accomplish the goals for the current redesign effort. The RSF model predicted the highest efficiency, while the RBNN had the highest prediction accuracy. The profile labelled with 0.0263 (local radius of curvature/D) corresponds to the B#2 impeller. It mainly consists of (i) inlet casing with the converging nozzle (ii) the impeller (iii) the diffuser and (iv Each impeller blade row has backward-swept blades mounted between a common back plate and shrouds. Park, “A study of impeller-diffuser-volute interaction in centrifugal fan,”, A. Atif, S. Benmansour, and G. Bois, “Numerical investigation of velocity flow field inside an impeller air model of a centrifugal pump with vaned diffuser interactions and comparison with PIV measurements,”, K. V. Karanth and N. Y. Sharma, “CFD analysis on the effect of radial gap on impeller-diffuser flow interaction as well as on the flow characteristics of a centrifugal fan,”, M. E. Slipper, P. J. McGinnis, G. Choi et al., “Design and evaluation of high performance lift fan models for the landing craft, air cushion (LCAC),”, A. Hosangadi, R. A. Lee, B. J. York, N. Sinha, and S. M. Dash, “Upwind unstructured scheme for three-dimensiona combusting flows,”, A. Hosangadi, R. A. Lee, P. A. Cavallo, N. Sinha, and B. J. York, “Hybrid, viscous, unstructured mesh solver for propulsive applications,” in. The unstructured cells help to reduce the overall size of the grid thereby reducing turnaround time for the calculations. Due to the geometrical symmetry, the CFD calculations only cover one single blade passage for the gridding system used, as shown in Figure 5. The shaft power values for the B#1 impeller and the design power threshold of 4.7% and goal of 10% reduction are also marked in each plot. Impeller is designed for the head (H) 24 m; discharge (Q) 1.583 L/sec; and speed (N) 2880 rpm. The CFD calculations for evaluating the fan performance were performed using a frozen impeller approach to compute the steady flows throughout the impeller and the volute. [6], and Karanth and Sharma [7] used both CFD and particle-image-velocity (PIV) measurement to study centrifugal fan impeller interactions with a vaned diffuser and a single discharge volute, and found that their steady numerical simulations were able to predict the flow characteristics, particularly the flow separation, which existed between the impeller and the diffuser. The impeller is a double-width, double-inlet (DWDI) centrifugal type with two nonstaggered blade rows. (v)The width of the impeller is almost linearly related to the impeller total head generated. However, the impeller efficiency remains nearly constant while the width changes. Given the impeller diameter and the flow rate, this parameter controls the maximum achievable flow velocity. The width for the NEW impeller was chosen to be 0.1213 D. In order to evaluate the fan performance, it is necessary to include the volute with each impeller. Figure 8 shows similar flow traces for impeller B#2’s surfaces. The computational resources from the Naval Oceanographic Office Major Shared Resource Center (NAVOCEANO MSRC) were provided through the DoD High Performance Computing Modernization Program (HPCMP). Before the diffused fluid started separating at the hub while the impeller width was increased, Kim et al. Energy consumption by pump is reduced by employing appropriate blade height. The design of the lift fan system is subject to meet payload, machinery spacing, and ruggedness requirements [1]. Volute feedback to the impeller reduces impeller efficiency by five to six percentage points from the original range of 93–95%. Similar exit pressures were applied for all other impeller calculations to obtain the lift flowrates shown in Tables 2 and 3. It is usually made of cast iron, steel, […] 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. The performance data shown in Figure 9(b) suggests that the shroud labelled with 0.0476 provides the largest gain in efficiency. 3-D numerical CFD tool is used for simulation of the flow field characteristics inside the turbo machinery. It also reduces fan efficiency by 0.5%. (ii)The flow turning area from the axial to the radial direction in front of the blade leading edge is required to be adequately designed to avoid the shroud flow separation. The steering process and 3D blade construction is discussed in the following sections. This paper presents the use of state-of-the-art reliability techniques to develop efficient structural design guidelines for civil engineering structures in a manner that includes overall structural system effects. AIAA-95-0221, 1995. The increased loading of the blade near midchord resulted in flow acceleration especially near the shroud where the original blades were prone to a large area of flow separation. Numerical Study on the Effect of Impeller Geometry on Pump Performance, Application of different surrogate models on the optimization of centrifugal pump. The blower design is a single stage forward- curved centrifugal blower used in (40) tons Rice Mill in Pyay, Bago west region. For the impeller-flow calculation, all boundary conditions used for the CFD design calculations were maintained except for eliminating the periodic boundary condition and controlling the exit back pressure through the interface information exchange.

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