scholarly journals Establishment of a Beamforming Dataset on Basic Models of Low-Speed Axial Fan Blade Sections

2017 ◽  
Vol 61 (2) ◽  
pp. 122 ◽  
Author(s):  
Esztella Balla ◽  
János Vad
Keyword(s):  
Phased Array ◽  
Reynolds Numbers ◽  
Strength Level ◽  
Source Strength ◽  
Axial Fan ◽  
Frequency Bands ◽  
Low Speed ◽  
Noise Characteristics ◽  
Wide Range ◽  
Fan Blade

The paper presents wind tunnel experiments, supplemented with phased array microphone measurements, on 2D basic models of low-speed axial fan blade sections: a flat plate, a cambered plate, and a RAF6-E airfoil. It aims at documenting the establishment of an acoustic beamforming dataset for the three profiles. The phased array microphone measurements offer spatially resolved information on the generated noise. The measurement setup enables the correlation of the streamwise evolution of the blade boundary layer with the associated noise characteristics. The dataset incorporates a wide range of incidence and Reynolds-numbers investigated. The present paper is confined to reporting on experimental results for arbitrarily selected representative incidences, Reynolds numbers, frequency bands, and profiles. The paper outlines a methodology for the evaluation and representation of the beamforming data in the following forms: source strength level based third-octave spectra obtained using background noise subtraction; maps presenting the loci of source strength level maxima; noise source maps for frequency bands of anticipated vortex shedding noise.

scholarly journals Lift and drag force measurements on basic models of low-speed axial fan blade sections

2018 ◽  
Vol 233 (2) ◽  
pp. 165-175 ◽  
Author(s):  
Esztella Balla ◽  
János Vad
Keyword(s):  
Drag Force ◽  
Aerodynamic Force ◽  
Measurement Data ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Force Measurements ◽  
Axial Fan ◽  
Low Speed ◽  
Fan Blade ◽  
Lift And Drag

This paper presents comparative data on the aerodynamic lift and drag of basic model representations of low-speed axial fan blade sections. Three main types of blades are investigated: flat plate, cambered plate and RAF6-E profiled airfoil. Lift and drag force are measured at three different Reynolds numbers (0.6 × 105, 105 and 1.4 × 105) around the threshold value of 105. The measurement data are compared to literature data. The aerodynamic force measurements reveal that, for Reynolds numbers below 105, cambered plate blade sections can be superior to airfoil profiles in terms of aerodynamic efficiency, especially in the high-load range. The effect of leading edge bluntness is also investigated. Leaving the leading edge of cambered plates blunt, tends to be uncritical for low Reynolds numbers at angles of attack between 4° and 10° but is critical at angles between 0° and 4°.

Fan Blade Design Methods: Cascade Versus Isolated Airfoil Approach — Experimental and Numerical Comparison

2016 ◽  
Author(s):  
Stefano Castegnaro
Keyword(s):  
Reynolds Numbers ◽  
Medium Size ◽  
Numerical Comparison ◽  
Blade Design ◽  
Axial Fan ◽  
Local Flow ◽  
Flow Features ◽  
Fan Blade ◽  
Mixed Approach ◽  
Cfd Analyses

Both cascade and isolated airfoil methods are considered valid in axial fan blade design, for high (σ≳1) and low (σ≲0.7) solidities respectively. For bladings that feature intermediate solidities the modified isolated approach is commonly employed. This method uses isolated airfoil data, with proper adjustments to take into account multiplane interference effects. Contrarily, the literature does not refer about modifications of the cascade approach to design medium solidity fans. Such method would use cascade data, properly adjusted for the blade sections at lower solidities. Thus, with the aim of comparing these two opposite design approaches (modified cascade versus modified isolated) for medium solidity blades, two free-vortex blading were designed for a 315 mm rotor-only axial fan and experimentally tested. CFD analyses were performed as well to obtain the local flow features. NACA-65 series airfoils were employed, as both cascade and isolated data are available for chord Reynolds numbers typical of axial fans applications. Results highlight the differences between the two approaches. Finally, a mixed approach that employs both isolated and cascade data is suggested as the most accurate one. Moreover, results also show the detrimental effects of the low chord Reynolds numbers on the performance of the blades. This effect should be taken into account in blade design for small-to-medium size machines.

Combined Aerodynamic and Phased Array Microphone Studies on Basic Models of Low-Speed Axial Fan Blade Sections

2018 ◽  
Author(s):  
Esztella Balla ◽  
János Vad
Keyword(s):  
Reynolds Number ◽  
Phased Array ◽  
High Efficiency ◽  
Low Reynolds Number ◽  
Low Noise ◽  
Axial Fan ◽  
Noise Sources ◽  
Low Speed ◽  
Axial Fans ◽  
Low Reynolds

The paper presents comparative aerodynamic and aeroacoustic studies on basic models of blade sections of low-speed, low-Reynolds-number axial fans. The wind tunnel experiments incorporated representative cambered plate and airfoil blade profiles. The aerodynamic measurements revealed that, for low Reynolds numbers, cambered plate blade sections may perform aerodynamically better than airfoil sections. A phased array microphone system, combined with a dipole beamforming and spatial filtering technique, offered a potential for localizing the noise sources in both streamwise and transversal direction. The acoustic studies focused on the profile vortex shedding noise. The results were qualitatively evaluated and compared with the semi-empirical noise prediction model developed by Brooks, Pope, and Marcolini. The measurements are considered as preparation of a dataset contributing to the background for designing high-efficiency, low-noise axial fans operating at low Reynolds number.

scholarly journals Numerical Analysis of Erosion Caused by Biomimetic Axial Fan Blade

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Jun-Qiu Zhang ◽  
Zhi-Wu Han ◽  
Hui-Na Cao ◽  
Wei Yin ◽  
Shi-Chao Niu ◽  
...  
Keyword(s):  
Numerical Study ◽  
Axial Flow ◽  
Erosive Wear ◽  
Impact Angle ◽  
Continuous Phase ◽  
Solid Particles ◽  
Discrete Phase Model ◽  
Axial Fan ◽  
Wide Range ◽  
Fan Blade

Damage caused by erosion has been reported in several industries for a wide range of situations. In the present work, a new method is presented to improve the erosion resistance of machine components by biomimetic method. A numerical investigation of solid particle erosion in the standard and biomimetic configuration blade of axial fan is presented. The analysis consists in the application of the discrete phase model, for modeling the solid particles flow, and the Eulerian conservation equations to the continuous phase. The numerical study employs computational fluid dynamics (CFD) software, based on a finite volume method. User-defined function was used to define wear equation. Gas/solid flow axial fan was simulated to calculate the erosion rate of the particles on the fan blades and comparatively analyzed the erosive wear of the smooth surface, the groove-shaped, and convex hull-shaped biomimetic surface axial flow fan blade. The results show that the groove-shaped biomimetic blade antierosion ability is better than that of the other two fan blades. Thoroughly analyze of antierosion mechanism of the biomimetic blade from many factors including the flow velocity contours and flow path lines, impact velocity, impact angle, particle trajectories, and the number of collisions.

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

scholarly journals Focusing of Particles in a Microchannel with Laser Engraved Groove Arrays

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 263
Author(s):  
Tianlong Zhang ◽  
Yigang Shen ◽  
Ryota Kiya ◽  
Dian Anggraini ◽  
Tao Tang ◽  
...  
Keyword(s):  
Open Space ◽  
Lateral Displacement ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Particle Sedimentation ◽  
Nanoparticle Separation ◽  
Wide Range ◽  
Fs Laser ◽  
Channel Bottom ◽  
Myoblast Cells

Continuous microfluidic focusing of particles, both synthetic and biological, is significant for a wide range of applications in industry, biology and biomedicine. In this study, we demonstrate the focusing of particles in a microchannel embedded with glass grooves engraved by femtosecond pulse (fs) laser. Results showed that the laser-engraved microstructures were capable of directing polystyrene particles and mouse myoblast cells (C2C12) towards the center of the microchannel at low Reynolds numbers (Re < 1). Numerical simulation revealed that localized side-to-center secondary flows induced by grooves at the channel bottom play an essential role in particle lateral displacement. Additionally, the focusing performance proved to be dependent on the angle of grooves and the middle open space between the grooves based on both experiments and simulation. Particle sedimentation rate was found to critically influence the focusing of particles of different sizes. Taking advantage of the size-dependent particle lateral displacement, selective focusing of micrometer particles was demonstrated. This study systematically investigated continuous particle focusing in a groove-embedded microchannel. We expect that this device will be used for further applications, such as cell sensing and nanoparticle separation in biological and biomedical areas.

scholarly journals Assessment of Steady and Unsteady Full Annulus Simulations Predictivity for a Low-Speed Axial Fan at Load-Controlled Windmill

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Aurélie Ortolan ◽  
Suk-Kee Courty-Audren ◽  
Nicolas Binder ◽  
Xavier Carbonneau ◽  
Yannick Bousquet ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Velocity Field ◽  
Detailed Analysis ◽  
Added Value ◽  
Classical Approach ◽  
Axial Fan ◽  
Low Speed ◽  
Unsteady Simulation ◽  
Temporal Periodicity

A steady mixing plane approach is compared with the time-averaged solution of an unsteady full annulus calculation for a conventional fan operating at load-controlled windmill. The objective is to assess the added value of a complete unsteady calculation compared with a more classical approach, especially concerning the effect of the spatial and temporal periodicity release in such an unusual operation as windmill. Experiment with global steady measurements and rotor radial characterizations was conducted. Numerical analysis demonstrates that windmilling global performances obtained with the time-averaged solution of the unsteady simulation are not far different from the steady case, especially in the rotor. Some differences arise in the stator, particularly regarding the velocity field. Temporal periodicity release in this row has clearly a significant effect on the flow unsteady response. A detailed analysis highlights that generic patterns of windmilling flows recorded on a steady approach are also reported on the unsteady case.

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