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Final Year Project Presentation On

Numerical Study of Aeroacoustic Fan Blade Designs for Ventilation and Cooling Solutions

By:

Md Sakil Islam Choudhury (BT17ME005)

Gudisa Sumanth (BT17ME013)

Harsh Upadhyay (BT17ME020)

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Department of Mechanical Engineering

National Institute of Technology, Mizoram

(Academic Session 2017 - 2021)

Under the Guidance of:

Dr. Bachu Deb

Asst. Professor

NIT Mizoram

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Contents

  • Introduction
  • Literature Review
  • Literature Gap
  • Objective
  • Work Done
  • Design and Modelling
  • Geometry
  • Mesh Generation
  • Boundary Conditions
  • Calculation
  • Results
  • Applications
  • Conclusion
  • References

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Introduction

Broadband Noise :

Noise whose sound energy is distributed over a wide section of the audible range as opposed to narrowband noise

Measured in decibels (dB)

  • 0 dB X 10 ~ 10 dB
  • 0 dB X 100 ~ 20 dB
  • 0 bB X 1000 ~ 30 dB

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Fig (1) : Types of Signals

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Self noise

Noise generated by a component wholly by itself without considering any external factor or force

Trailing edge

The rear edge of a moving aerodynamic body

Leading Edge

The front edge of a moving aerodynamic body

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Fig (2) : Airfoil Geometry

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Bird’s (Owl) Wings :

  • Wing design
  • Biomimicry
  • Silent flight
  • Distributed turbulent sections
  • Lower noise

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Fig (3) : Owl’s Wings

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Pressure based fans :

Fans which are designed for higher static / total pressure to be able to pull / push air through a fin stack or filter - used for cooling and ventilation systems

  • Pressure > CFM
  • Higher blade count

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Fig (4) : Pressure Centric Fans

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Use Case scenarios

  • Any aerodynamic Body
  • Wing tips
  • Fan blade tips
  • Trailing edge design
  • Home appliances like Ventilation systems
  • Cooling solutions in electronic equipments and radiators

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Fig (5) : Chevrons

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Material used

Acrylonitrile butadiene styrene (ABS Plastic)

  • Low Melting Point ~ 200°C
  • Impact, chemical and abrasion resistance
  • Easily machined and thermoformed
  • Printable
  • Life Span
  • Commonly Used

​

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Fig (6) : ABS Plastic Structure

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Acoustic Power Level

  • Acoustic power is the rate at which sound energy is emitted, reflected, transmitted or received, per unit time

Total Pressure

  • Sum of the static pressure, the dynamic pressure, and the gravitational potential energy per unit volume
  • Static Pressure - pressure of fluid on body, when fluid is at rest
  • Dynamic pressure - pressure of fluid, due to its motion
  • Negative Pressure - Lower pressure than surroundings
  • Positive Pressure - Higher pressure than surrounding

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Turbulence Intensity

  • Ratio of standard deviation of fluctuating wind velocity to the mean wind speed

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S.No.

Name of the Author

Name of Article

Key Findings

1.

Alexandro Vathylakis

On the aeroacoustic and flow structures developed on a flat

Plate with a sawtooth trailing edge

Sawtooth Edges may

Reduce noise throughout frequency range

2.

Auris Juknevicius

On the leading edge noise and aerodynamics of thin aerofoil

subjected to the straight and curved serrations

Lower turbulence wakes - lower noise profile

3.

Benshuai Lyu

Rapid noise prediction models for serrated leading and trailing edges

Serrated Leading and Trailing Edges on large sized airfoils

Literature Review

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S.No.

Name of the Author

Name of Article

Key Findings

4.

Yanling Chen

Experimental study on bird-wing-shaped suppression device for vortex-induced vibration of deep water risers

Bird wing shape supreses large wakes

5.

Alex Siu Hong Lau

The control of aerodynamic sound due to boundary layer

pressure gust scattering

Scattering of turbulence can decrease aerodynamic sound

6.

Alexandro Vathylakis

Aeroacoustic study of a wavy stator leading edge in a OGV stage

Wavy stator leading edges for intakes

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S.No.

Name of the Author

Name of the Article

Key Findings

7.

Zhenbo Lu

Quieter propeller with serrated trailing edge

Possible quieter aircraft propellers with serrations

8.

Fan Tong

On the study of wavy leading-edge vanes to achieve low fan interaction noise

Serrated leading edges for lower noise profile

9.

Min-Jun Park

Journal of Sound and Vibration

Broadband noise reduction from geometry-wake reduction

10.

Seung Heo

Development of low-noise centrifugal fans for a refrigerator

S-shaped trailing edge noise reduction

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  • Small fan
  • Trailing edges wave forms
  • Leading edge wave forms
  • Compatible in real life usage

Consumer grade usage

  • Feasibility
  • Difference in performance

Results

  • Numerical calculation and simulation of a small consumer friendly design
  • Analysis of results of the simulation
  • Turbulence intensity & Surface Acoustics

Simulation and Analysis

Literature Gap

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Objectives :

  • Reduce broadband noise
  • Maintain optimum total pressure
  • Distribute / minimise large turbulent wakes
  • consumer friendly design
  • Trailing Edge Serration effects
  • Leading Edge Serration effects
  • Comparison of designs

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  • Design of high pressure fan with curved edges / serrated edges
  • Meshing of the new designs
  • Simulation of the new designs in a given scenario
  • Analysis of the results of the new simulations
  • Comparison of the newly obtained results to an ordinary design

Work done

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  • Design of a standard 7 blade high static pressure fan with blade edge fillet - Solidworks
  • Improvement in design for lower broadband noise, turbulence intensity, higher efficiency
  • Meshing and Boundary Conditions - Ansys Fluent
  • Calculation via Simulation - Ansys Fluent
  • Result + plotting - Ansys Fluent

Design and Modelling

Fig (6) : Softwares Used

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  • Hub Diameter : 33 mm
  • Total Diameter : 135 mm
  • Fillet : 0.4 mm & 2 mm
  • Blade angle : 25, 30, 40, 45 degrees
  • Height : 15 mm

Geometry :

Fig (10) : Hub Diameter

Fig (7) : Blade Diameter

Fig (9) : Leading Edge Angles

Fig (8) : Trailing edge Angles

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  • Same as standard in all main dimensions
  • Trailing edge serrations using spline feature along the edge w.r.t. equidistant sections
  • Leading edge serrations using spline feature along the edge w.r.t. equidistant sections
  • Fillet : 0.4 mm on the trailing and leading edges
  • Depth of cut : 5 mm

Fig (11) : Trailing edge Wavy Cut

Fig (12) : Leading Edge Wavy Cut

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Fig (13) : Standard High Pressure Fan

Fig (14) : Wavy Trailing Edge design High Pressure Fan

Fig (15) : Wavy Leading Edge design High Pressure Fan

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  • Method : Tetrahedrons
  • Size : 0.5 mm
  • Growth : 1.2
  • Metric : Orthogonal Quality & Skewness
  • Elements : 889767
  • Smoothing : Medium
  • Method : Tetrahedrons
  • Size : 0.5 mm
  • Growth : 1.2
  • Metric : Orthogonal Quality & Skewness
  • Elements : 978023
  • Smoothing : Medium
  • Method : Tetrahedrons
  • Size : 0.5 mm
  • Growth : 1.2
  • Metric : Orthogonal Quality & Skewness
  • Elements : 953938
  • Smoothing : Medium

Mesh Generation

Fig (16) : Mesh on Standard Model

Fig (17) : Mesh on Trailing Edge Model

Fig (18) : Mesh on Leading Edge Model

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  • Dimensions (Walls - Box) :
  • Length + X : 250 mm
  • Length + Y : 250 mm
  • Length + Z : 250 mm
  • Length - X : 250 mm
  • Length - Y : 750 mm
  • Length - Z : 250 mm
  • Inlet : Pressure
  • Outlet : Pressure
  • Walls : Other 4 sides
  • Dimensions (Rotating Enclosure - Cylinder) :
  • Cushion Radius : 2.5 mm
  • Cushion +ve Direction : 25 mm
  • Cushion -ve Direction : 25 mm

Boundary Conditions

Fig (19) : Outer Walls with Inlet & Outlet

Fig (20) : Rotating Enclosure with Cushion

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  • Type : Pressure Based
  • Velocity : Absolute
  • Time : Transient
  • Viscous Model : k-epsilon (2 eq)�Two variables : turbulent kinetic energy (k) & rate of dissipation of turbulent kinetic energy (ε)

Calculation

U(i) - velocity component

E(ij) - component of rate of deformation

µ (t) - Eddy Viscosity

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  • Model : Resizable
  • Near wall treatment : Scalable wall functions
  • Fluid : Air
  • Solid : Plastic - ABS
  • RPM : 2000 RPM - Clockwise

�Second Order : Three data points instead of just two for better accuracy of results�Second Order Upwind : Pressure and density based solving�

  • Pressure : Second Order
  • Momentum : Second Order Upwind
  • Turbulent Kinetic Energy : Second Order Upwind
  • Turbulent Dissipation Rate : Second Order Upwind
  • Transient Formulation : Second Order Implicit
  • Hybrid Initialization - Prediction work by software
  • Time Step Size : 0.3 (Rate of progression in time)
  • Time-steps : 25
  • Iteration/time-step : 20
  • Number of Time steps : 500

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Results

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Acoustic Power Level (dB) - Front view

Max (dB) : 44.27774

Max (dB) : 41.78651

Fig (21) : Contour Plot on Standard Model

Fig (22) : Contour Plot on Wavy Trailing Edge Model

Fig (23) : Contour Plot on Wavy Leading Edge Model

Max (dB) : 35.82212

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Acoustic Power Level (dB) - Rear view

Fig (24) : Contour Plot on Standard Model

Fig (25) : Contour Plot on Wavy Trailing Edge Model

Fig (26) : Contour Plot on Wavy Leading Edge Model

Max (dB) : 44.27774

Max (dB) : 41.78651

Max (dB) : 35.82212

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Total Pressure - Front view

Min (pascal) : - 94.11116

Max (pascal) : 132.377

Min (pascal) : - 68.97321

Max (pascal) : 185.9766

Fig (27) : Contour Plot on Standard Model

Fig (28) : Contour Plot on Wavy Trailing Edge Model

Fig (29) : Contour Plot on Wavy Leading Edge Model

Min (pascal) : - 119.0295

Max (pascal) : 84.99216

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Total Pressure - Rear view

Fig (30) : Contour Plot on Standard Model

Fig (31) : Contour Plot on Wavy Trailing Edge Model

Fig (32) : Contour Plot on Wavy Leading Edge Model

Min (pascal) : - 94.11116

Max (pascal) : 132.377

Min (pascal) : - 68.97321

Max (pascal) : 185.9766

Min (pascal) : - 119.0295

Max (pascal) : 84.99216

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Turbulence Intensity - Front view

Min (%) : 0.04928653

Max (%) : 290.2234

Min (%) : 0.04890646

Max (%) : 332.7478

Fig (33) : Contour Plot on Standard Model

Fig (34) : Contour Plot on Wavy Trailing Edge Model

Fig (35) : Contour Plot on Wavy Leading Edge Model

Min (%) : 0.04780451

Max (%) : 222.4287

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Turbulence Intensity - Rear view

Fig (36) : Contour Plot on Standard Model

Fig (37) : Contour Plot on Wavy Trailing Edge Model

Fig (38) : Contour Plot on Wavy Leading Edge Model

Min (%) : 0.04928653

Max (%) : 290.2234

Min (%) : 0.04890646

Max (%) : 332.7478

Min (%) : 0.04780451

Max (%) : 222.4287

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Surface Acoustics Power Level (dB) - Front view

Max (dB) : 48.26274

Max (dB) : 46.05598

Fig (39) : Contour Plot on Standard Model

Fig (40) : Contour Plot on Wavy Trailing Edge Model

Fig (41) : Contour Plot on Wavy Leading Edge Model

Max (dB) : 44.9222

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Surface Acoustics Power Level (dB) - Rear view

Fig (42) : Contour Plot on Standard Model

Fig (43) : Contour Plot on Wavy Trailing Edge Model

Fig (44) : Contour Plot on Wavy Leading Edge Model

Max (dB) : 48.26274

Max (dB) : 46.05598

Max (dB) : 44.9222

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Applications

  • Radiators
  • Processor / Electronic Component Coolers
  • Household Exhaust Systems
  • Air Conditioning Systems

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Fig (46) : Radiator Fans

Fig (47) : Household Exhaust Systems

Fig (48) : Electronic Cooler Components

Fig (45) : Air Conditioning systems

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  • Trailing and Leading serrated edges can reduce the noise generated by a significant amount
  • Better total pressure, negative pressure and Turbulence Intensities
  • Useful in ventilation & cooling solutions where air needs to be sucked through a fin stack / filtering mesh
  • Ex : Kitchen ventilation systems, radiators, air conditioning systems.
  • Noise floor reduction in noisy offices, server stations
  • User friendly design
  • Easy tweaking and manufacturing of parts

Conclusion

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References

  1. On the aeroacoustic and flow structures developed on a flat plate with a serrated sawtooth trailing edge; Tze PeiChong n, Alexandros Vathylakis; College of Engineering, Designand Physical Sciences, Brunel University London, Uxbridge UB83PH, United Kingdom
  2. Experimental study on bird-wing-shaped suppression device for vortex-induced vibration of deep water risers; Zifeng Li *, Guangming Song , Yanling Chen; Petroleum Engineering Institute, Qinhuangdao, Yanshan University, China
  3. The control of aerodynamic sound due to boundary layer pressure gust scattering by trailing edge serrations; Alex Siu Hong Lau a, Xun Huangb,a,*; a Department of Mechanical and Aerospace Engineering, School of Engineering, The Hong Kong University of Science and Technology, Hong Kong, China; b State Key Laboratory of Turbulence and Complex Systems, Department of Aeronautics and Astronautics, College of Engineering, Peking University, Beijing, China
  4. Aeroacoustic study of a wavy stator leading edge in a realistic fan/OGV stage; Damiano Casalino, Francesco Avallone, Ignacio Gonzalez-Martino, Daniele Ragni
  5. On the leading edge noise and aerodynamics of thin aerofoil subjected to the straight and curved serrations; Auris Juknevicius, Tze Pei Chong*; Department of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge, UB8 3PH, United Kingdom

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  1. Rapid noise prediction models for serrated leading and trailing edges; Benshuai Lyu, Lorna J. Ayton
  2. Quieter propeller with serrated trailing edge; Hsiao Mun Lee a,b, Zhenbo Lu c, Kian Meng Lim b, Jinlong Xie d,⇑, Heow Pueh Lee b; a Center for Research on Leading Technology of Special Equipment, School of Mechanical and Electric Engineering, Guangzhou University, 230 Wai Huan Xi Road, Guangzhou; 510006, PR China; b Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore; c Temasek Laboratories, National University of Singapore, Singapore 117411, Singapore; d School of Mechanical and Electric Engineering, Guangzhou University, 230 Wai Huan Xi Road, Guangzhou 510006, PR China
  3. On the study of wavy leading-edge vanes to achieve low fan; interaction noise; Fan Tong a, *, Weiyang Qiao a, b, Kunbo Xu a, Liangfeng Wang a, Weijie Chen a,; Xunnian Wang c; a School of Power and Energy, Northwestern Polytechnical University, Xi'an, Shaanxi, 710129, China; b Key Laboratory of Aerodynamic Noise Control, China Aerodynamics Research and Development Center, Mianyang, Sichuan, 621000,; China; c State Key Laboratory of Aerodynamics, China Aerodynamics Research and Development Center, Mianyang, Sichuan, 621000, China
  4. Development of low-noise centrifugal fans for a refrigerator using inclined S-shaped trailing edge Développement de ventilateurs centrifuges peu sonores pour un réfrigérateur à l’aide de la bordure de traînée inclinée en forme de S; Author links open overlay panel Seung Heoa Cheolung Cheonga Tae-Hoon Kimb

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Thank You

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