Axial Fan Blade Tone Cancellation Using Optimally Tuned Quarter Wavelength Resonators

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Lee Gorny ◽  
Gary H. Koopmann
Keyword(s):  
Sound Field ◽  
Test Facility ◽  
Secondary Source ◽  
Axial Fan ◽  
Ducted Fan ◽  
Quarter Wavelength ◽  
Centrifugal Fans ◽  
Line Theory ◽  
Axial Fans ◽  
Fan Blade

Fan noise challenges noise control engineers in developing products ranging in scale from small ventilation systems to large turbomachines. The dominant noise source in many axial fans is the tonal noise due to rotor/stator interactions at the fundamental blade passing frequency. Flow-excited resonators have been used in the past for minimizing blade tone sound pressure levels (SPLs) generated by centrifugal fans through means of secondary source cancellation. The focus of this research is to extend that cancellation method to axial fans by attaching flow-driven quarter wavelength resonators fitted with optimal mouth perforations around the perimeter of the fan’s shroud. A ducted-fan test facility was developed to measure upstream and downstream noise radiated from a test fan. Resonators were mounted at specific locations around the fan’s shroud to obtain reductions in blade tone SPLs in both flow directions. They were driven into resonance via the unsteady pressure from the passing blades. An analytical model using transmission line theory was developed and validated experimentally to characterize the resonator’s behavior under various flow conditions and mouth geometries. This model was used to predict the resonator’s potential for reducing in-duct blade tones for specific flows and mouth perforation patterns. In a series of experiments to obtain the optimal resonator mouth perforations, it was observed that upstream and downstream SPL attenuations require different placement of the resonator mouth relative to the blade of the fan. With a single tuned resonator it was demonstrated that the fundamental blade tone SPLs can be reduced by as much as 20 dB in either the upstream or the downstream duct but not in both directions simultaneously. This behavior results when combining the resonator’s monopolelike sound field with the dipolelike sound field of the fan’s blades. Further studies are underway to extend the above method to higher pressure fans operating at speeds that generate higher order duct modes.

Accurate Calculation of the Slip Factor of Axial Cascades and Impellers for Arbitrary Blade Shapes

2011 ◽  
Author(s):  
Henrik Smith ◽  
Matthias Semel ◽  
Philipp Epple ◽  
Mihai Miclea-Bleiziffer ◽  
Antonio Delgado
Keyword(s):  
Design Process ◽  
Accurate Calculation ◽  
Axial Fan ◽  
One Dimensional ◽  
Slip Factor ◽  
Angle Correction ◽  
Line Theory ◽  
Axial Fans ◽  
The One ◽  
Real Flow

Nowadays, design, redraft and optimisation strategies of axial fans often still rely on the one dimensional mean line theory. However, as it is well known, it is based on a number of assumptions that do not apply to real flow behaviour so that various deviations can be observed. In the present paper, the plane potential theory is used to examine and calculate these deviations. The behaviour of axial cascades is analysed in general and a slip factor is computed. On this basis a quasi-3D calculation method is developed. It is applied to an exemplary impeller and the results are compared with 3D CFD computations. The main characteristic figures are presented and different angle correction and angle exaggeration methods are investigated and compared. Finally, the applicability of the presented method to a precise axial fan design process is illustrated.

A Ring Silencer Design for Reducing Noise of Axial Fan

2003 ◽  
Vol 03 (03) ◽  
pp. L259-L264
Author(s):  
Jian-Da Wu ◽  
Mingsian R. Bai
Keyword(s):  
Helmholtz Resonator ◽  
Boundary Region ◽  
Acoustic Analogy ◽  
Axial Fan ◽  
Noise Sources ◽  
Fan Noise ◽  
Fluctuating Pressure ◽  
Axial Fans ◽  
Fan Blade ◽  
Broadband Frequency

In this paper, a ring silencer design for reducing the noise of axial fans is presented. The noise sources on axial fans are usually caused by the fluctuating pressure distribution on the surface of fan blade. Most of the sources are near the trailing edge of blades or boundary region of blades. The ideation of proposed design is based on the principle of Helmholtz resonator for reducing the noise around the fan. The electro-acoustic analogy of this design is presented and simply discussed. Experimental measurement is carried out to evaluate the proposed design for reducing the axial fan noise. The result of experiment indicated that the ring silencer achieved 17 dB in blade passing frequency and 10 dB in other broadband frequency of power spectrum level.

scholarly journals Strength Analysis of a Ducted Axial Fan Blade

2018 ◽  
Vol 9 (4) ◽  
pp. 85-100
Author(s):  
Marek ROŚKOWICZ ◽  
Ryszard CHACHURSKI ◽  
Sławomir TKACZUK ◽  
Piotr LESZCZYŃSKI ◽  
Maciej MAJCHER ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Numerical Calculations ◽  
Strength Analysis ◽  
Axial Fan ◽  
Optical Scanner ◽  
Geometrical Features ◽  
Simplifying Assumptions ◽  
Axial Fans ◽  
Fan Blade ◽  
And Performance

This paper presents a numerical strength analysis of a ducted axial fan blade. Ducted axial fans are a large group of fluid-flow machines. The analysis was designed to determine the causes of cyclic failures of a ventilation unit. The paper presents a reverse engineering approach to the mapping of the fan blade’s geometrical features. The geometrical features were mapped by triangulation from the scanning images produced by a 3D optical scanner. These were followed by simplifying assumptions on which the numerical calculations were based. The numerical calculations were carried out at the operating rotational speeds of the ducted axial fan’s rotor. The course of the numerical calculations is described, and their results are also presented herein. The results are represented on colour maps of stress distribution for selected structural elements of the fan blade. The stress distribution at a blade cross-section was compared to CT scans of the fractures of failed rotor blade airfoils. Final conclusions were developed which show that the design engineering process of fans should feature optimisation of the fan’s efficiency, including the strength and performance parameters, which should include the service life of the fan.

Numerical Study on the Passive Control of the Aeroelastic Response in Large Axial Fans

2016 ◽  
Author(s):  
A. Castorrini ◽  
A. Corsini ◽  
A. G. Sheard ◽  
F. Rispoli
Keyword(s):  
Passive Control ◽  
Numerical Study ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Axial Fan ◽  
Strongly Coupled ◽  
Dimensional Approximation ◽  
Axial Fans ◽  
Fan Blade ◽  
And Performance

The morphing geometry concept finds interesting applications in load reduction and performance increasing for wings and rotor blades in off-design conditions. Here we report a numerical study on the effect that a passive morphing system (made by an elastic-low stiffness surface) has on the sectional load and flowfield, when it is applied to the trailing edge of an axial fan. We obtain the results extracting the section of the fan blade and test it in the 2D cascade, with and without the elastic device, in different operating conditions. Keeping in mind the two-dimensional approximation, it will be possible to observe how the tested device could reduce the load in off-design and high angle of attack conditions, while the same solution could introduce vibrations in design conditions. All the simulations imply the solution of the fluid-structure interaction between the incompressible, turbulent flow and the elastic structure. This solution is obtained using a finite element based, strongly coupled solver, applied to the periodic 2D domain of the section in the cascade.

Morphing of Reversible Axial Fan Blade: A FSI-FEM Study

2021 ◽  
Author(s):  
Valerio F. Barnabei ◽  
Alessio Castorrini ◽  
Alessandro Corsini ◽  
Franco Rispoli
Keyword(s):  
Research Effort ◽  
Elastic Solid ◽  
Navier Stokes ◽  
Design Solution ◽  
Axial Fan ◽  
Navier Stokes Equation ◽  
Linear Elastic ◽  
Axial Fans ◽  
Fan Blade ◽  
Dynamics Simulations

Abstract Reversible axial fans are widely used in industrial and tunnel ventilation systems, and a lot of research effort is spent in the design process of the blades shape and blades profile. The target is to achieve reasonable performances in both flow directions, but those are still below the levels of the corresponding non-reversible geometries. In this paper, an alternative design solution for reversible axial fan is presented by adopting flexible blades instead of the rigid ones. Such design, inspired by the boat sails, could allow the blade to change its shape by passively adapting to the flow field, from a symmetrical blade profile to a not symmetric one, and thus adapting the curvature to the flow condition. In the paper, a series of alternative materials and material distributions are analysed and compared. The analysis is conducted by performing Fluid-Structure Interaction simulations using stabilized Finite Elements formulations for both the fluid and the structure dynamics. Simulations are performed using the in-house built software FEMpar, which implements the Residual Based Variational MultiScale to model the Navier-Stokes equation, the Total Lagrangian formulation for the non-linear elastic solid and the Solid Extension Moving Mesh Technique to move the fluid mesh.

Surface Coating Effect on Protection of Icing for Axial Fan Blade

2011 ◽  
Author(s):  
Takeshi Murooka ◽  
Shinichirou Shishido ◽  
Riho Hiramoto ◽  
Takakazu Minoya
Keyword(s):  
Surface Coating ◽  
Axial Fan ◽  
Fan Blade

scholarly journals Introduction of an Universal Scale-Up Method for the Efficiency of Axial and Centrifugal Fans

2014 ◽  
Author(s):  
Peter F. Pelz ◽  
Stefan S. Stonjek
Keyword(s):  
Test Data ◽  
Scale Up ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Total Efficiency ◽  
Scaling Method ◽  
Centrifugal Fans ◽  
Axial Fans ◽  
Definition Of ◽  
Acceptance Tests

Acceptance tests on large fans to prove the performance (efficiency and total pressure rise) to the customer are expensive and sometimes even impossible to perform. Hence there is a need for the manufacturer to reliably predict the performance of fans from measurements on down-scaled test fans. The commonly used scale-up formulas give satisfactorily results only near the design point, where inertia losses are small in comparison to frictional losses. At part- and overload the inertia losses are dominant and the scale-up formulas used so far fail. In 2013 Pelz and Stonjek introduced a new scaling method which fullfills the demands ( [1], [2]). This method considers the influence of surface roughness and geometric variations on the performance. It consists basically of two steps: Initially, the efficiency is scaled. Efficiency scaling is derived analytically from the definition of the total efficiency. With the total derivative it can be shown that the change of friction coefficient is inversely proportional to the change of efficiency of a fan. The second step is shifting the performance characteristic to a higher value of flow coefficient. It is the task of this work to improve the scaling method which was previously introduced by Pelz and Stonjek by treating the rotor/impeller and volute/stator separately. The validation of the improved scale-up method is performed with test data from two axial fans with a diameter of 1000 mm/250mm and three centrifugal fans with 2240mm/896mm/224mm diameter. The predicted performance characteristics show a good agreement to test data.

scholarly journals Control of Fan Blade Vibrations Using Piezoelectrics and Bi-Directional Telemetry

2011 ◽  
Author(s):  
Andrew J. Provenza ◽  
Carlos R. Morrison
Keyword(s):  
Low Voltage ◽  
Radio Telemetry ◽  
Magnetic Bearing ◽  
Test Facility ◽  
Test Results ◽  
Novel Device ◽  
Ac Power ◽  
Dynamic Spin ◽  
Wireless Device ◽  
Fan Blade

A novel wireless device which transfers supply power through induction to rotating operational amplifiers and transmits low voltage AC signals to and from a rotating body by way of radio telemetry has been successfully demonstrated in the NASA Glenn Research Center (GRC) Dynamic Spin Test Facility. In the demonstration described herein, a rotating operational amplifier provides controllable AC power to a piezoelectric patch epoxied to the surface of a rotating Ti plate. The amplitude and phase of the sinusoidal voltage command signal, transmitted wirelessly to the amplifier, was tuned to completely suppress the 3rd bending resonant vibration of the plate. The plate’s 3rd bending resonance was excited using rotating magnetic bearing excitation while it spun at slow speed in a vacuum chamber. A second patch on the opposite side of the plate was used as a sensor. This paper discusses the characteristics of this novel device, the details of a spin test, results from a preliminary demonstration, and future plans.

Aeroacoustic Optimization of a Pressure-Side Strut Configuration for Subsonic Axial Fans Using Statistical-Empirical Modelling

2018 ◽  
Author(s):  
Igor Neifach ◽  
Gi-Don Na ◽  
Frank Kameier ◽  
Nils Springer ◽  
Marco Wichers
Keyword(s):  
Residential Buildings ◽  
Statistical Design ◽  
Axial Fan ◽  
Noise Emission ◽  
Public Places ◽  
Empirical Modelling ◽  
Passive Construction ◽  
Cooling Fan ◽  
Rotor Stator Interaction ◽  
Axial Fans

This paper deals with the reduction of aerodynamically generated noise in passenger car Cooling-Fan-Modules (CFM), caused by the interaction between the impeller and the downstream-located strut configuration of the axial fan. Even after the car engine is switched off, the fan remains active, as long as cooling is required for certain vehicle components. Especially after a car has been parked in closed parking areas, in close proximity to residential buildings or public places, the noise emission can be a problem. This issue is addressed by dampening the rotor-stator-interaction through passive construction measures. In order to ensure optimal noise reduction, 8 critical design features of the struts are identified and investigated using statistical design of experiment methods (DoE). Based on the results, dedicated insights about the effects of concrete strut features on significant regions of the acoustic fan spectrum are obtained. Furthermore, an optimized strut configuration is derived and metrologically validated using a polyoptimization method. Compared to a current serial baseline configuration, a reduction of the overall sound pressure level by 2.6 dB(A), as well as a reduction of the blade passage frequency tone by 17.6 dB(A) is achieved.

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