scholarly journals Experiment-Based Preliminary Design Guidelines for Consideration of Profile Vortex Shedding From Low-Speed Axial Fan Blades

2020 ◽  
Author(s):  
Gábor Daku ◽  
János Vad
Keyword(s):  
Vortex Shedding ◽  
Design Guidelines ◽  
Preliminary Design ◽  
Axial Fan ◽  
Noise Emission ◽  
Blade Vibration ◽  
Low Speed ◽  
Blunt Trailing Edge ◽  
Axial Fans ◽  
Semi Empirical

Abstract The paper presents hot wire measurements in a wind tunnel, close downstream of basic models of blade sections being representative for low-speed, low-Reynolds-number axial fans, in order to explore the signatures of vortex shedding (VS) from the blade profiles. Using the Rankine-type vortex approach, an analytical model was developed on the velocity fluctuation represented by the vortex streets, as an aid in evaluating the experimental data. The signatures of profile VS were distinguished from blunt-trailing-edge VS based on Strouhal numbers obtained from the measurements in a case-specific manner. Utilizing the experimental results, the semi-empirical model available in the literature for predicting the frequency of profile VS was extended to low-speed axial fan applications. On this basis, quantitative guidelines were developed for consideration of profile VS in preliminary design of axial fans in moderation of VS-induced blade vibration and noise emission.

scholarly journals Experiment-Based Preliminary Design Guidelines for Consideration of Profile Vortex Shedding From Low-Speed Axial Fan Blades

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Gábor Daku ◽  
János Vad
Keyword(s):  
Vortex Shedding ◽  
Design Guidelines ◽  
Preliminary Design ◽  
Axial Fan ◽  
Noise Emission ◽  
Blade Vibration ◽  
Low Speed ◽  
Blunt Trailing Edge ◽  
Axial Fans ◽  
Semi Empirical

Abstract This paper presents hot-wire measurements in a wind tunnel, close downstream of basic models of blade sections being representative for low-speed, low-Reynolds number axial fans, in order to explore the signatures of vortex shedding (VS) from the blade profiles. Using the Rankine-type vortex approach, an analytical model was developed on the velocity fluctuation represented by the vortex streets, as an aid in evaluating the experimental data. The signatures of profile VS were distinguished from blunt trailing-edge VS based on Strouhal numbers obtained from the measurements in a case-specific manner. Utilizing the experimental results, the semi-empirical model available in the literature for predicting the frequency of profile VS was extended to low-speed axial fan applications. On this basis, quantitative guidelines were developed for the consideration of profile VS in preliminary design of axial fans in the moderation of VS-induced blade vibration and noise emission.

scholarly journals Preliminary Design Guidelines for Considering the Vibration and Noise of Low-Speed Axial Fans Due to Profile Vortex Shedding

2022 ◽  
Vol 7 (1) ◽  
pp. 2
Author(s):  
Gábor Daku ◽  
János Vad
Keyword(s):  
Vortex Shedding ◽  
Design Method ◽  
Axial Flow ◽  
Design Guidelines ◽  
Worst Case ◽  
Low Speed ◽  
Increased Risk ◽  
Axial Fans ◽  
Fan Blade ◽  
Set Up

This paper presents a critical overview on worst-case design scenarios for which low-speed axial flow fans may exhibit an increased risk of blade resonance due to profile vortex shedding. To set up a design example, a circular-arc-cambered plate of 8% relative curvature is investigated in twofold approaches of blade mechanics and aerodynamics. For these purposes, the frequency of the first bending mode of a plate of arbitrary circular camber is expressed by modeling the fan blade as a cantilever beam. Furthermore, an iterative blade design method is developed for checking the risky scenarios for which spanwise and spatially coherent shed vortices, stimulating pronounced vibration and noise, may occur. Coupling these two approaches, cases for vortex-induced blade resonance are set up. Opposing this basis, design guidelines are elaborated upon for avoiding such resonance. Based on the approach presented herein, guidelines are also developed for moderating the annoyance due to the vortex shedding noise.

scholarly journals Profile vortex shedding from low-speed axial fan rotor blades: a modelling overview

2021 ◽  
pp. 095765092110268
Author(s):  
Gábor Daku ◽  
János Vad
Keyword(s):  
Vortex Shedding ◽  
Empirical Model ◽  
Rotor Blades ◽  
Evaluation Methodology ◽  
Future Research ◽  
Axial Fan ◽  
Low Speed ◽  
Simplifying Assumptions ◽  
Set Up ◽  
Semi Empirical

This paper presents an overview of the characteristics potentially influencing the profile vortex shedding (PVS) phenomenon being relevant in noise and vibration of low-speed axial fan rotor blades. Dimensional analysis has been applied to explore the essential dimensionless quantities in a systematic and comprehensive manner. On this basis, limitations have been established, and simplifying assumptions have been set up in terms of PVS investigation. Groups of dimensionless characteristics playing a role in the semi-empirical model for predicting the PVS frequency were identified. The available semi-empirical model and its unique features related to the measurement evaluation methodology and Reynolds number dependence have been outlined. The presented comprehensive analysis provides guidelines from the perspective of transferability of the literature data on PVS from steady, isolated blade profile models to low-speed axial fan rotors. It also results in the formulation of objectives of future research related to PVS.

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.

Derivative Design of Axial Fan Range: From Academia to Industry

2016 ◽  
Author(s):  
Tommaso Bonanni ◽  
Lucio Cardillo ◽  
Alessandro Corsini ◽  
Giovanni Delibra ◽  
Anthony G. Sheard ◽  
...  
Keyword(s):  
Performance Prediction ◽  
Good Accuracy ◽  
Design Method ◽  
Three Dimensional ◽  
Correct Prediction ◽  
Preliminary Design ◽  
Axial Fan ◽  
Data Set ◽  
Axial Fans ◽  
Relative Errors

The work presented in this paper concerns a useful method for axial fans preliminary design based on the “Derivative Design” concept. The emphasis is, on one side, on education and, on the other, on the practical help that such method can provide in the early preliminary design process. A complete data set of an axial fan measured with ISO 5801 standards is the start point for the investigation and the prediction of the multiple possible performance that different fan configurations can provide, in terms of dimensionless duty coefficients. In particular, configurations with different number of blades, and hence of solidity, are studied. The typical options of derivative design are explored and relations for performance prediction are presented. A detailed description of the derivative design methodology is followed by tests and validation. The tools employed are a fully three dimensional code, the Advanceded Actuator Disk Mode (AADM), and two other in-house codes, the Meanline Axisymmetric Calculation (MAC) and Axisymmetric Laboratory (AXLAB). Results of the derivative design method are reported, showing a good accuracy against the AADM data. The MAC and AXLAB ensure still acceptable results when increasing the solidity of the machine. On the contrary, a decrease of solidity leads to higher relative errors in the prediction of the load coefficient. In conclusion, an exploration of the possible fields of operation of a blade profile can be carried out by a correct prediction of the stage diffusion factor.

An Analysis of the Loss Mechanisms in Low-Speed Axial Fans Using Scaling Arguments and Their Effects on a Proposed New Definition of Efficiency

2006 ◽  
Author(s):  
Douglas R. Neal
Keyword(s):  
Energy Equation ◽  
Pressure Rise ◽  
Axial Fan ◽  
Low Speed ◽  
Static Efficiency ◽  
Axial Fans ◽  
Integral Energy ◽  
Definition Of ◽  
Scaling Arguments ◽  
Ventilation Fan

Low-speed axial fans are used extensively for ventilation purposes in industrial and commercial buildings. In agricultural applications, such as a greenhouse, the ventilation is critical, since entire crops can be damaged or destroyed if a clean air supply is not maintained. The cost-marginal nature of these businesses demand that operating costs be kept to a minimum, hence there is a strong motivation to develop higher efficiency ventilation fans. An analysis of a low-speed axial fan has been developed using a control volume-based energy balance. The specific fan is an axial ventilation fan that is commonly found on agricultural facilities such as green-houses or livestock buildings. These fans induce an airflow from a large building into the open atmosphere at very low (or often effectively zero) system restriction or pressure rise. The definition for static efficiency, which is commonly used by the axial fan community, is examined and its implications are discussed. Since static efficiency yields a zero-percent efficient fan at a zero pressure rise operating condition, the ventilation fan industry has developed an alternate definition of efficiency. This alternate definition of efficiency, along with other proposed definitions, are described and their limitations are discussed. A new definition of efficiency is introduced and its basis in the integral energy equation is identified. The primary loss mechanisms of low-speed axial turbomachinery are discussed and scaling arguments are developed and used in the integral energy equation analysis. The results of this analysis yield an expanded expression of efficiency in which the loss mechanism terms can be empirically determined. When analyzed with values for a particular fan system, these results can further be used as the basis for an optimization study of that fan system.

Preliminary Design of Axial Fans at Off-Design Working Points

2014 ◽  
Author(s):  
Matthias Semel ◽  
Julien Grilliat ◽  
Antonio Delgado
Keyword(s):  
Best Practice ◽  
Preliminary Design ◽  
Hydraulic Efficiency ◽  
Axial Fan ◽  
Free Vortex ◽  
Best Practice Guidelines ◽  
Work Distribution ◽  
Theoretical Predictions ◽  
Axial Fans ◽  
Straight Lines

An analytical formulation for axial fan performances at and off design point is proposed for an arbitrary work distribution. It is shown that the total pressure, total-to-static pressure and hydraulic efficiency characteristics can be described by means of hyperbola, straight lines and parabola. This formulation is applied to axial fans with free vortex work distributions, allowing a theoretical study onto the influence of the hub-to-tip ratio. Theoretical predictions are compared with numerical simulations. Good qualitative agreements are found. Conclusions onto the best practice guidelines for the design of axial fan according to a free vortex work distributions are presented.

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