Three-Dimensional Flow Analysis and Improvement of Slip Factor Model for Forward-Curved Blades Centrifugal Fan

2003 ◽  
Author(s):  
En-Min Guo ◽  
Kwang-Yong Kim
Keyword(s):  
Factor Model ◽  
Pressure Coefficient ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Correction Method ◽  
Factor Models ◽  
Centrifugal Impeller ◽  
Centrifugal Fan ◽  
Slip Factor ◽  
Cfd Analyses

The objective of this work is to develop improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan by investigating the validity of various slip factor models. Both steady and unsteady three-dimensional CFD analyses were performed with a commercial code to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the presented model takes into account the effect of blade curvature. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient.

Validations of Some Slip Factor Models for Mixed-Flow Impellers

2008 ◽  
Author(s):  
Shengqin Huang ◽  
Zhenxia Liu ◽  
Yaguo Lu ◽  
Yan Yan ◽  
Xiaochun Lian
Keyword(s):  
Inclination Angle ◽  
Factor Model ◽  
Critical Value ◽  
Factor Models ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Correct Prediction ◽  
Mixed Flow ◽  
Blade Number ◽  
Slip Factor

Accurate modeling of the slip factor is essential for correct prediction of the mixed-flow impeller performance, but the slip factor model well-known for mixed-flow impeller is relatively rare. Two ways for calculating mixed-flow impeller slip factor are present in this paper: (1) Using impeller exit inclination angle correction to transform the slip factor for centrifugal impeller to mixed-flow machine. (2) Setting up model that can be used to mixed-flow machine directly. Based on these two ways, there are six slip factor models chosen for mixed-flow impeller, including models of Wiesner, Stodola, Staniz, Paeng, Backstrom and Qiu. And they are need to be validated by experiments data to find a proper method for mixed-flow machine. The test data are reproduced from Wiesner’s work and nine mixed-flow impellers are included. Experiment and simulation (including six slip factors) have been conducted and the results show that: (1) slip factor models of centrifugal impeller can be used to mixed-flow impeller while no proper mixed-flow slip factor models exist. If the impeller discharge inclination angle is greater than 45 degree, then these models can be used for mixed-flow impellers directly without transformation. (2) Equivalent blade number exists in mixed-flow impeller and it may have critical value. There are only little differences between results calculated by various slip factor models in the condition of equivalent blade number beyond the critical value. Otherwise it has to choose proper slip factor models as different situations while the equivalent blade number is less than the critical value. (3) Blade number, impeller exit inclination angle and exit blade angle of mixed-flow impeller are dominated over slip factor, but blade turning rate and flow coefficient have to be taken into account for more exact solution.

Numerical investigations on the effect of volute casing treatment for performance augmentation in a centrifugal fan

2021 ◽  
pp. 095440622110341
Author(s):  
Manjunath L Nilugal ◽  
K Vasudeva Karanth ◽  
Madhwesh N
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Centrifugal Fan ◽  
Casing Treatment ◽  
Sliding Mesh ◽  
Optimum Configuration

This article presents the effect of volute chamfering on the performance of a forward swept centrifugal fan. The numerical analysis is performed to obtain the performance parameters such as static pressure rise coefficient and total pressure coefficient for various flow coefficients. The chamfer ratio for the volute is optimized parametrically by providing a chamfer on either side of the volute. The influence of the chamfer ratio on the three dimensional flow domain was investigated numerically. The simulation is carried out using Re-Normalisation Group (RNG) k-[Formula: see text] turbulence model. The transient simulation of the fan system is done using standard sliding mesh method available in Fluent. It is found from the analysis that, configuration with chamfer ratio of 4.4 is found be the optimum configuration in terms of better performance characteristics. On an average, this optimum configuration provides improvement of about 6.3% in static pressure rise coefficient when compared to the base model. This optimized chamfer configuration also gives a higher total pressure coefficient of about 3% validating the augmentation in static pressure rise coefficient with respect to the base model. Hence, this numerical study establishes the effectiveness of optimally providing volute chamfer on the overall performance improvement of forward bladed centrifugal fan.

Blade Loading and Numerical Slip Factor of Centrifugal Compressor Impellers

1999 ◽  
Author(s):  
JongSik Oh
Keyword(s):  
State Of The Art ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Blade Design ◽  
Direct Relation ◽  
Blade Profile ◽  
Blade Loading ◽  
Slip Factor ◽  
Compressible Turbulent Flow ◽  
Good Agreement

Abstract Through the state-of-the-art CFD approach, the Eckardt radial bladed and backswept impellers were analyzed to investigate the effect of blade loadings from blade design shape on the slip factor variation for the change of the flow rate. In addition, a new design of the blade profile was arbitrarily attempted to generate a center-loading pattern in the Eckardt backswept impeller. Three dimensional compressible turbulent flow analysis was applied, with the Baldwin-Lomax turbulence model adopted, to get the numerical slip factor, using the mass-averaged concept, at the discharge plane of each impeller. The numerical slip factors are in good agreement with the experimental ones, and the Wiesner’s slip factors are found to deviate further from the numerical and experimental ones, especially in the two backswept impellers. The deviation angles and the blade loadings in the meridional channel are found in no direct relation with the trend of change of the slip factors. Blade-to-blade loadings in midspan location are, however, found in direct relation, especially at the sections where maximum loadings are to be expected. That information can be utilized in establishing an improved expression for slip factor in the future.

scholarly journals Numerical Investigations of Unsteady Flow in a Centrifugal Pump with a Vaned Diffuser

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Olivier Petit ◽  
Håkan Nilsson
Keyword(s):  
Centrifugal Pump ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Centrifugal Impeller ◽  
Test Case ◽  
Vaned Diffuser ◽  
Pump Test ◽  
Steady Simulation ◽  
Turbulent Models ◽  
Cfd Analyses

Computational fluid dynamics (CFD) analyses were made to study the unsteady three-dimensional turbulence in the ERCOFTAC centrifugal pump test case. The simulations were carried out using the OpenFOAM Open Source CFD software. The test case consists of an unshrouded centrifugal impeller with seven blades and a radial vaned diffuser with 12 vanes. A large number of measurements are available in the radial gap between the impeller and the diffuse, making this case ideal for validating numerical methods. Results of steady and unsteady calculations of the flow in the pump are compared with the experimental ones, and four different turbulent models are analyzed. The steady simulation uses the frozen rotor concept, while the unsteady simulation uses a fully resolved sliding grid approach. The comparisons show that the unsteady numerical results accurately predict the unsteadiness of the flow, demonstrating the validity and applicability of that methodology for unsteady incompressible turbomachinery flow computations. The steady approach is less accurate, with an unphysical advection of the impeller wakes, but accurate enough for a crude approximation. The different turbulence models predict the flow at the same level of accuracy, with slightly different results.

A Simulation of the Unsteady Interaction of a Centrifugal Impeller With its Vaned Diffuser: Flows Analysis

1994 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
High Loss ◽  
Swirl Angle ◽  
Unsteady Interaction ◽  
Unsteady Effects

The aim of this paper is to help advance our understanding of the complex, three-dimensional, unsteady flow associated with the interaction of a splattered centrifugal impeller and its vaned diffuser. A time-resolved simulation is presented of the Krain stage performed using a time-accurate, 3D, unstructured mesh, solution-adaptive Navier-Stokes solver. The predicted flowfield, compared with experiment where available, displays a complex, unsteady interaction especially in the neighbourhood of the diffuser entry zone which experiences large periodic flow unsteadiness. Downstream of the throat, although the magnitude of this unsteadiness diminishes rapidly, the flow has a highly distorted three-dimensional character. The loss levels in the diffuser are then investigated to try and determine how time-mean loss levels compare with the levels expected from “equivalent” steady flow analysis performed by using the circumferentially averaged exit flow from the impeller as inlet to the diffuser. It is concluded that little loss could be attributed directly to unsteady effects but rather that the principle cause of the rather high loss levels observed in the diffuser is the strong spanwise distortion in swirl angle at inlet which initiates a strong hub/comer stall.

Blade Thickness Effect on Impeller Slip Factor

2010 ◽  
Author(s):  
Donghui Zhang ◽  
Jean-Luc Di Liberti ◽  
Michael Cave
Keyword(s):  
Factor Model ◽  
Numerical Study ◽  
Flow Direction ◽  
Leading Edge ◽  
Thickness Effect ◽  
Centrifugal Impeller ◽  
Trailing Edge ◽  
Slip Factor ◽  
Blade Thickness ◽  
Blockage Factor

A numerical study of the effect of the blade thickness on centrifugal impeller slip factor is presented in this paper. The CFD results show that generally the slip factor decreases as the blade thickness increases. Changing the thickness at different locations has different effects on the slip factor. The shroud side blade thickness has more effect on the impeller slip factor than the hub side blade thickness. In the flow direction, the blade thickness at 50% meridional distance is the major factor affecting the slip factor. The leading edge thickness has little effect on slip factor. There is an optimum thickness at the trailing edge for the maximum slip factor. For this impeller, the hub side thickness ratio of 0.5 between the trailing edge and the middle of the impeller gives the highest value of the slip factor, while the ratio of 0.25 at shroud side gives the highest value of the slip factor. A blockage factor is added into the slip factor model to include the aerodynamic blockage effect on the slip factor. The model explains the phenomena observed in the CFD results and the test data very well.

The Impact of Forward Swept Rotors on Tip Clearance Flows in Subsonic Axial Compressors

2004 ◽  
Vol 126 (4) ◽  
pp. 445-454 ◽  
Author(s):  
G. Scott McNulty ◽  
John J. Decker ◽  
Brent F. Beacher ◽  
S. Arif Khalid
Keyword(s):  
Pressure Coefficient ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Flow Measurements ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Axial Compressors ◽  
Flow Mechanisms ◽  
Cfd Analyses ◽  
The Impact

This paper presents an experimental and analytical study of the impact of forward swept rotors on tip-limited, low-speed, multistage axial compressors. Two different configurations were examined, one with strong tip-clearance flows and the other with more moderate levels. Evaluations were done at multiple rotor tip clearances to assess differences in clearance sensitivity. Compared to conventionally stacked radial rotors, the forward swept blades demonstrated improvements in stall margin, efficiency and clearance sensitivity. The benefits were more pronounced for the configuration with stronger tip-clearance flows. Detailed flow measurements and three-dimensional viscous CFD analyses were used to investigate the responsible flow mechanisms. Forward sweep causes a spanwise redistribution of flow toward the blade tip and reduces the tip loading in terms of static pressure coefficient. This results in reduced tip-clearance flow blockage, a shallower (more axial) vortex trajectory and a smaller region of reversed flow in the clearance gap.

scholarly journals A Rapid Aerodynamic Loading Procedure for Centrifugal Impeller Design

1994 ◽  
Author(s):  
J. H. G. Howard ◽  
Colin Osborne ◽  
David Japikse
Keyword(s):  
Industrial Design ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Design Procedure ◽  
Inviscid Flow ◽  
Centrifugal Impeller ◽  
Zone Model ◽  
Geometry Design ◽  
Loading Method ◽  
Rapid Loading

A crucial aspect of the design process for centrifugal impellers is the establishment of specific blade shapes. A rapid inviscid flow analysis procedure was developed for incorporation within a geometry manipulation code. Using a single streamtube model, a single-pass computation technique was generated. A two-zone model ensures that key features of the passage flow physics are incorporated. Several examples of industrial design problems are employed to demonstrate the capabilities of the rapid loading method and its use in a geometry design procedure (used by some 20 industrial design groups worldwide). Comparisons with a quasi-three-dimensional method are included. The rapid loading method is most accurate when the meridional stream paths have similar shapes to those for the hub and shroud contours. The technique is useful within a geometry generation program since rapid aerodynamic screening of candidate configurations is allowed with sufficient accuracy to avoid the need for quasi-three-dimensional approaches. If required, the final design may be analyzed using three-dimensional viscous flow calculation methods.

Parametric Study on Aerodynamic Performance of a Centrifugal Fan With Additionally Installed Splitter Blades

2013 ◽  
Author(s):  
Man-Woong Heo ◽  
Jin-Hyuk Kim ◽  
Kyung-Hun Cha ◽  
Kwang-Yong Kim
Keyword(s):  
Flow Separation ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Height Ratio ◽  
Navier Stokes Equations ◽  
Fan Performance

Aerodynamic Performance of a centrifugal fan with additionally installed splitter blades in the impeller has been investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model and hexahedral grids system were used to analyze the flow in the centrifugal fan. From results of the flow analysis, considerable energy loss by flow separation was observed in the blade passages. Splitter blades were applied between the main blades to reduce the loss and enhance fan performance. The chord length ratio of splitter to main blade, the angle between splitter and main blade, and the height ratio of outlet and inlet of impeller were selected as the geometric parameters, and their effects on the aerodynamic performance of the centrifugal fan have been investigated. The performance of the centrifugal fan with added splitter blades was improved conspicuously compared to the centrifugal fan without splitter blades. It was found that the installation of splitter blades in the impeller is effective to improve the aerodynamic performance of a centrifugal fan by reducing the flow separation generated between main blades in the impeller.

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