Forward Blade Sweep Applied to Low-Speed Axial Fan Rotors of Controlled Vortex Design: An Overview

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
János Vad
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Suction Side ◽  
Loss Reduction ◽  
Axial Fan ◽  
Flow Paths ◽  
Free Vortex ◽  
Low Speed ◽  
Cvd Method ◽  
Circulation Distribution

An overview is given on the research maintained by the author about the design aspects of three-dimensional blade passage flow in low-speed axial flow industrial fan rotors, affected by spanwise changing design blade circulation due to controlled vortex design (CVD), blade forward sweep (FSW), and their combination. It was pointed out that, comparing the CVD method to the free vortex design, the fluid in the blade suction side boundary layer has an increased inclination to migrate radially outward, increasing the near-tip blockage and loss. It was concluded that the benefit of FSW, in terms of moderating loss near the tip, can be better utilized for the rotors of the CVD, in comparison to the free vortex design. Compared to the free vortex design, the FSW applied to the blades of the CVD was found to also be especially beneficial in loss reduction away from the endwalls, via shortening the flow paths on the suction side—in any case being elongated by the radially outward flow due to CVD—and thus, reducing the effect of wall skin friction. The necessity of correcting the swept blades was pointed out for matching with the prescribed CVD circulation distribution.

Forward Blade Sweep Applied to Low-Speed Axial Fan Rotors of Controlled Vortex Design: An Overview

2012 ◽  
Author(s):  
János Vad
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Suction Side ◽  
Loss Reduction ◽  
Axial Fan ◽  
Flow Paths ◽  
Free Vortex ◽  
Low Speed ◽  
Cvd Method ◽  
Circulation Distribution

An overview is given on the research maintained by the author about design aspects of three-dimensional blade passage flow in low-speed axial flow industrial fan rotors, affected by spanwise changing design blade circulation due to controlled vortex design (CVD), blade forward sweep (FSW), and their combination. It was pointed out that, comparing the CVD method to free vortex design, the fluid in the blade suction side boundary layer has increased inclination to migrate radially outward, increasing near-tip blockage and loss. It was concluded that the benefit of FSW, in terms of moderating loss near the tip, can be better utilized for rotors of CVD, in comparison to free vortex design. Compared to free vortex design, FSW applied to blades of CVD was found especially beneficial in loss reduction also away from the endwalls, via shortening the flow paths on the suction side — being anyway elongated by the radially outward flow due to CVD —, and thus, reducing the effect of wall skin friction. The necessity of correcting the swept blades was pointed out for matching with the prescribed CVD circulation distribution.

On the Role of Leading-Edge Bumps in the Control of Stall Onset in Axial Fan Blades

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Alessandro Corsini ◽  
Giovanni Delibra ◽  
Anthony G. Sheard
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Axial Fan ◽  
Early Recovery ◽  
Viscosity Models ◽  
Flow Mechanisms ◽  
The Impact

Taking a lead from the humpback whale flukes, characterized by a series of bumps that result in a sinusoidal-like leading edge, this paper reports on a three-dimensional numerical study of sinusoidal leading edges on cambered airfoil profiles. The turbulent flow around the cambered airfoil with the sinusoidal leading edge was computed at different angles of attack with the open source solver OpenFOAM, using two different eddy viscosity models integrated to the wall. The reported research focused on the effects of the modified leading edge in terms of lift-to-drag performance and the influence of camber on such parameters. For these reasons a comparison with a symmetric airfoil is provided. The research was primarily concerned with the elucidation of the fluid flow mechanisms induced by the bumps and the impact of those mechanisms on airfoil performance, on both symmetric and cambered profiles. The bumps on the leading edge influenced the aerodynamic performance of the airfoil, and the lift curves were found to feature an early recovery in post-stall for the symmetric profile with an additional gain in lift for the cambered profile. The bumps drove the fluid dynamic on the suction side of the airfoil, which in turn resulted in the capability to control the separation at the trailing edge in coincidence with the peak of the sinusoid at the leading edge.

An Investigation Into Performance Characteristics of an Axial Flow Fan Using CFD for Electronic Devices

2015 ◽  
Author(s):  
Hafiz M. Hashim ◽  
Baris Dogruoz ◽  
Mehmet Arik ◽  
Murat Parlak
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Volumetric Flow Rate ◽  
Critical Issue ◽  
Data Sets ◽  
Axial Fan ◽  
Flow Rates ◽  
Cad Models ◽  
And Control ◽  
Control Association

Rotating fans are widely utilized in thermal management applications and their accurate characterization has recently become even a more critical issue for thermofluids engineers. The present study investigates the characterization of an axial fan computationally and experimentally. Using the three-dimensional CAD models of the fan, a series of computational fluid dynamics (CFD) simulations were performed to determine the flow and pressure fields produced by the axial mover over a range of flow rates. In order to validate the computational model findings, experiments were conducted to obtain the pressure drop values at different flow rates in an AMCA (Air Movement and Control Association) standard 210-99, 1999 wind tunnel. These data sets were also compared with the fan vendor’s published testing data. A reasonably good agreement was obtained among the data from these three separate sources. Furthermore, an attempt was made to understand the overall fan efficiency as a function of the volumetric flow rate. It was determined that the maximum overall fan efficiency was less than 27% correlating well with the computational results.

The Role of Forward Sweep in Subsonic Axial Fan Rotor Aerodynamics at Design and Off-Design Operating Conditions

2003 ◽  
Author(s):  
A. Corsini ◽  
F. Rispoli
Keyword(s):  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Design Parameters ◽  
Axial Fan ◽  
Suction Surface ◽  
Free Vortex ◽  
Application Range ◽  
Rotor Aerodynamics ◽  
Work Distribution

The role that forward sweep plays in the aerodynamics of subsonic axial fan rotor is herein discussed, with emphasis on the combined effects of non-uniform three-dimensional work distribution and modified stacking lines. To study blade forward sweep effects numerical investigations have been undertaken on highly loaded fans of non-free vortex design, with ideal total head rise coefficient typical of industrial application range. The results of two rotors with identical overall design parameters and, respectively, with 35-deg forward swept blades and unswept blades have been compared. The investigation has been carried-out using an accurate in-house developed multi-level parallel finite element RANS solver, with the adoption of a non-isotropic two-equation turbulence closure. The pay-off derived from the sweep technology has been assessed with respect to the operating range improvement. To this end the flow structure developing through the blade passages and downstream of the rotors as well as loss distributions have been analysed at three different operating conditions. The studies showed that the forward swept blade operates more efficiently in particular at low volume flows, with a delayed onset of stall. The analyses of three-dimensional flow structures showed that, sweeping forward the blade, the flow centrifugation on blade suction surface is reduced and non-free vortex spanwise secondary flows is attenuated. Moreover, reduced fluid mechanical losses have been also pointed out in rotor with swept blades.

Computation of Three-Dimensional Turbulent Turbomachinery Flows Using a Coupled Parabolic-Marching Method

1988 ◽  
Vol 110 (4) ◽  
pp. 549-556 ◽  
Author(s):  
K. R. Kirtley ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layers ◽  
Three Dimensional ◽  
Axial Flow ◽  
Suction Side ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Navier Stokes Equation ◽  
Pressure Losses ◽  
Compressor Rotor ◽  
Marching Method

A new coupled parabolic-marching method was developed to compute the three-dimensional turbulent flow in a turbine endwall cascade, a compressor cascade wake, and an axial flow compressor rotor passage. The method solves the partially parabolized incompressible Navier–Stokes equation and continuity in a coupled fashion. The continuity equation was manipulated using pseudocompressibility theory to give a convergent algorithm for complex geometries. The computed end-wall boundary layers and secondary flow compared well with the experimental data for the turbine cascade as did the wake profiles for the compressor cascade using a k–ε turbulence model. Suction side boundary layers, pressure distributions, and exit stagnation pressure losses compared reasonably well with the data for the compressor rotor.

Experimental study on aerodynamic loss and heat transfer for various squealer tips

2021 ◽  
pp. 1-31
Author(s):  
Jin-sol Jung ◽  
Inkyom Kim ◽  
Jin Sung Joo ◽  
Sang-woo Lee
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Load ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Side ◽  
Loss Reduction ◽  
Turbine Cascade ◽  
Low Speed ◽  
Aerodynamic Loss

Abstract This paper presents aerodynamic loss data for five squealer configurations of a full squealer (FS), a pressure-side squealer (PS), a suction-side squealer (SS), a camberline squealer (CS), and a full-camberline squealer (FCS) in a low speed turbine cascade. In addition, tip thermal load data are also reported for the FS, PS, and SS tips. The results show that when h/s (tip clearance-to-span ratio) ≥ 0.96%, the mass-averaged loss for the FS tip decreases, has a minimum value, and then increases, as the squealer height (hst) increases. For h/s = 0.48%, however, the loss changes with hst/s is found to be minute. For the FS tip, the loss tends to increase, as the squealer thickness increases. Adding a camberline squealer to the FS tip is not beneficial in the loss reduction. When hst/s < 3.82% for h/s = 0.96%, the FS tip has the lowest mass-averaged loss, the SS tip has the second lowest loss, the PS tip has higher loss compared to the SS tip, and the CS tip loss is highest, regardless of hst/s. For h/s = 0.96%, the average tip thermal load for the FS tip is lower than the PS tip one but is higher than the SS tip one. Thus, the SS tip delivers the lowest average thermal load, irrespective of hst/s.

A Computational Study of Tip Desensitization in Axial Flow Turbines: Part 2 — Turbine Rotor Simulations With Modified Tip Shapes

2004 ◽  
Author(s):  
James A. Tallman
Keyword(s):  
Mass Flow ◽  
Computational Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Numerical Procedure ◽  
Suction Side ◽  
Turbine Rotor ◽  
Leakage Flow ◽  
Side Edge ◽  
Blade Tip

This study used Computational Fluid Dynamics (CFD) to investigate modified turbine blade tip shapes as a means of reducing the leakage flow and vortex. The subject of this study was the single-stage experimental turbine facility at Penn State University, with scaled three-dimensional geometry representative of a modern high-pressure stage. To validate the numerical procedure, the rotor flowfield was first computed with no modification to the tip, and the results compared with measurements of the flowfield. The flow was then predicted for a variety of different tip shapes: first with coarse grids for screening purposes and then with more refined grids for final verification of preferred tip geometries. Part 2 of this two-part paper focuses on flow-field predictions with modified blade tip geometries, and the corresponding comparisons with the baseline, flat-tip solutions presented in Part 1. Fifteen different tip shapes were computed using the ADPAC CFD Solver and moderately sized grids (720,000 nodes). These modified tip shapes incorporated different combinations of blade tip edge rounding and squealer cavities, both square and rounded, as means of reducing the leakage flow and vortex. Rounding of the suction side edge of the blade tip resulted in a considerable reduction in the size and strength of the leakage vortex, while rounding of the pressure side edge of the blade tip significantly increased the mass flow rate through the gap. Rounded squealer cavities acted to reduce the mass flow through the gap and proved advantageous over traditional, square squealer cavities. The presence of a square squealer cavity without edge rounding showed no aerodynamic advantage over a flat tip. Final computations of two preferred tip shapes were then carried out using more refined grids (7.2 million nodes). The final, refined grid computations reconfirmed a reduction in the leakage flow and vortex, as well as their associated losses.

Investigation on Improved Blade Tip Concept for Axial Flow Fan

2006 ◽  
Author(s):  
Alessandro Corsini ◽  
Bruno Perugini ◽  
Franco Rispoli ◽  
A. G. Sheard ◽  
Iain R. Kinghorn
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Axial Flow ◽  
Vortical Flow ◽  
Aerodynamic Noise ◽  
Flow Paths ◽  
Flow Mechanisms ◽  
Axial Fans ◽  
Parallel Finite Element ◽  
Blade Tip

The three dimensional structures of the blade tip vortical flow field is discussed for a family of axial fans in fully-ducted configuration, to investigate an improved blade tip concept. This concept is based on geometrical modification of datum blade by means of profiled end-plates at the tip. The investigation has been carried-out using an accurate in-house developed multi-level parallel finite element RANS solver, with the adoption of a non-isotropic two-equation turbulence closure. Due to the fully-ducted configuration, the fans have a complex vortical flow field near the rotor tip. The nature of the flow mechanisms in the fan tip region is correlated to the specific blade design features that promote reduced aerodynamic noise. It was found that the tip geometrical modification markedly affects the multiple vortex leakage flow behaviour, by reducing the pressure difference within the tip gap and by altering the near-wall fluid flow paths on the blade surfaces. The rotor loss behaviour, in the blade tip region, was also discussed in order to assess the effect of blade tip geometry onto the rotor efficiency.

A Numerical Study of Secondary Flows in a 1.5 Stage Axial Turbine Guiding the Design of a Non-Axisymmetric Hub

2017 ◽  
Author(s):  
Hayder M. B. Obaida ◽  
Hakim T. K. Kadhim ◽  
Aldo Rona ◽  
Katrin Leschke ◽  
J. Paul Gostelow
Keyword(s):  
Secondary Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Suction Side ◽  
Side Branch ◽  
Secondary Flows ◽  
Design Work ◽  
Axial Turbine ◽  
Turbine Performance

The performance of axial flow turbines is affected by losses from secondary flows that result in entropy generation. Reducing these secondary flow losses improves the turbine performance. This paper investigates the effect of applying a non-axisymmetric contour to the hub of a representative one-and-half stage axial turbine on the turbine performance. An analytical end-wall hub surface definition with a guide groove is used to direct the pressure side branch of the horseshoe vortex away from the blade suction side, so to retard its interaction with the suction side secondary flow and thus decrease the losses. This groove design is a development of the concept outlined in Obaida et al. (2016). A baseline three-dimensional steady RANS k-ω SST model, with axisymmetric walls, is validated against reference experimental measurements from a one-and-half stage turbine at the Institute of Jet Propulsion and Turbomachinery at RWTH Aachen, Germany. The CFD predictions of the non-axisymmetric hub with the guide groove show a decrease in the total pressure loss coefficient. The design work-flow is generated using the Alstom Process and Optimisation Workbench (APOW), which sensibly reduced the designer workload. The implementation of the guide groove has excellent portability to the turbomachinery industry and this makes this method promising for delivering the UK energy agenda through more efficient power turbines.

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