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Purdue University Purdue University
Purdue e-Pubs Purdue e-Pubs
Publications of the Ray W. Herrick Laboratories School of Mechanical Engineering
7-2019
Influence of Geometric Parameters on Aerodynamic and Acoustic Influence of Geometric Parameters on Aerodynamic and Acoustic
Performances of Bladeless Fans Performances of Bladeless Fans
Ang Li Purdue University
Jun Chen Purdue University
Yangfan Liu Purdue University
J Stuart Bolton Purdue University, [email protected]
Patricia Davies Purdue University
Follow this and additional works at: https://docs.lib.purdue.edu/herrick
Li, Ang; Chen, Jun; Liu, Yangfan; Bolton, J Stuart; and Davies, Patricia, "Influence of Geometric Parameters on Aerodynamic and Acoustic Performances of Bladeless Fans" (2019). Publications of the Ray W. Herrick Laboratories. Paper 213. https://docs.lib.purdue.edu/herrick/213
This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information.
AJKFLUIDS 2019-5220 07.28-08.01 San Francisco, CA, USA
Influence of Geometric Parameters on Aerodynamic
and Aeroacoustic Performance of Bladeless Fans
August 1st, 2019
Ang Li, Jun Chen, Yangfan Liu,
Stuart Bolton, Patricia Davies
Ray W. Herrick Laboratories
Purdue University
West Lafayette, 47907, USA
207.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
OUTLINE
⚫ Background & Motivation
⚫ Methodology
➢ Experiments
➢ Numerical Simulations
⚫ Results
⚫ Conclusions
307.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
BACKGROUND: FANS IN INDUSTRY
Vehicle Engine
HVAC
CPU Radiator Fan
Cooling Fan
Applications
– Cooling system
– Ventilation
– Thermal comfort
Features
– High flow rate
– Low noise level
407.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
BLADELESS FAN
• Bladeless fans launched by Dyson©
Working mechanism of the bladeless fan
Advantages
– The produced wind is softer and more uniform.
– Flow rate at downstream is larger.
– No visible rotating blade is safer for children.
Jafari et al. (2015)
507.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
AN EXAMPLE OF THE BLADELESS FAN
– UK, Dyson. “Dyson Cool Fans - Air Multiplier Technology Explained - Official Video.” YouTube, YouTube, 5 Mar. 2014,www.youtube.com/watch?v=bUJ-X1rsKV4.
607.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
PREVIOUS WORK
Li et al. (2016)
Curve 1
Curve 2
Prototype
Curve 3
Curve 4
Curve 5
Pressure (Pa)
Flow field structure outside the bladeless fan over the center plane
Pressure distribution near the slit with different Coandasurface curvatures
Li et al. (2014)
Effect of the outlet thickness and outlet angle on volume flow rate at downstream
Streamlines outside the bladeless fan over the center plane
Sound power contour
Jafari et al. (2015) Jafari et al. (2016) Jafari et al. (2016)
707.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
OBJECTIVE & RESEARCH STRATEGY
▪ Characterize the aerodynamic and aeroacoustic performances of the
bladeless fan by a combined 3D numerical and experimental study
▪ Investigate the influence of geometric parameters of the wind channel
on bladeless fan’s performance
Bladeless fan Prototype
Experiments Numerical Simulations
c
H
Influence of the geometric parameters of the wind channel
x0
807.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
METHODOLOGY: VELOCITY MEASUREMENT AT FAR FIELD
3D ultrasonicanemometer 0.8m
X velocity contour
@x = 1.5m
– Measurement position: 837
– Measurement duration at each position: 30s
– Sampling rate: 1s
– Accuracy: ±(2%+0.03m/s of indicated values)
yz
x
x = 1.5m
Measurement in Herrick PBE Lab
907.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
METHODOLOGY: SOUND PRESSURE MEASUREMENT AT RECEIVERS
B&K intensity probeMeasurement in Herrick
anechoic chamber
x = 1.5m
Receiver 1
z = 0.8m
z
x
x = 0.1m
Receiver 2
Sound pressure level@ two receivers
1007.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
PROTOTYPE OF THE BLADELESS FAN
Blocks at slit
10cm
Cross-section of the wind channel
Wind channel
Simulation Set-up
– The number of grids: 6,320,000
– Steady RANS: 𝒌 − 𝜺 model
– LES: Smagorinsky-Lilly model
– Time step: 𝟏 × 𝟏𝟎−𝟒s
– Flow solver: SIMPLE
Computational domain
Temperature: 25℃~ 30℃
Reynolds number at the intake and the slit: 𝐑𝐞𝐢𝐧𝐭𝐚𝐤𝐞 = 𝟔𝟕𝟐𝟑,𝐑𝐞𝐬𝐥𝐢𝐭 = 𝟑𝟎𝟎𝟎~𝟒𝟏𝟎𝟎
c
H
d=2mm, H=3cm, c=12cm, x0/c=10%
x0
Qinlet
= 0.11kg/s
1107.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
MESH GENERATION OF THE BLADELESS FAN
centerline
x = 1.5m
z
x
z
y
– Mesh independency test
• Mesh for the computational domain • Mesh for the cross-section of the wind channel
𝒚+ = 𝟎.𝟖𝟓
1207.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
METHODOLOGY: DATA POSTPROCESSING
Power spectral density of sound
pressure
Sound pressure
level
Acoustics Analysis
(Solver: Matlab)
Aeroacoustic
results
Unsteady Flow
Simulation+ BC & IC
(Solver: OpenFoam)
'( , )p tx
(FW-H analogy)
Aeroadynamicresults
1307.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
⚫ X velocity over Z planes
⚫ LES, t = 5s to 15s
RESULTS: INSTANTANEOUS FLOW FIELD
z = 0.3mz = 0.55m
z = 0.8m
1407.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
AERODYNAMIC CHARACTERISTICS: MEAN FLOW
@ z = 0.8m
@ the center plane of the bladeless fan
LES, time-averaged
(t = 4s to 15s)
Exp.
@ X=1.5 m
RANS
centerline
x = 1.5m
z
x
z
y
1507.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
⚫ Pressure over Z planes
⚫ LES, averaged from t=4s to 15s
AERODYNAMIC CHARACTERISTICS: MEAN PRESSURE
z = 0.3mz = 0.55m
z = 0.8m
Pressure (Pa)
1607.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
EFFECT OF THE SLIT WIDTH
LES, time averaged for t = 4s to 15s, @ x =1.5 m
d/c = 1.25% d/c = 2.08% d/c = 2.50%d/c = 1.67% (baseline)
@ z = 0.8m
Slit Width
c = 12cm
1707.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
EFFECT OF THE CROSS-SECTION HEIGHT
H = 2cm
H = 3cm
H = 4cm
H = 5cm
c = 12cm
H/c = 16.7% H/c = 33.3% H/c = 41.7%H/c = 25.0% (baseline)
LES, time averaged for t = 4s to 15s, @ x =1.5 m
@ z = 0.8m
1807.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
EFFECT OF THE SLIT LOCATION
𝒙𝟎/c = 5% 𝒙𝟎/c = 15% 𝒙𝟎/c = 20%𝒙𝟎/c = 10% (baseline)
c = 12cm
x0 = 0.6cm
x0 = 1.2cm
x0 = 1.8cm
x0 = 2.4cm
LES, time averaged for t = 4s to 15s, @ x =1.5 m
@ z = 0.8m
1907.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
EFFECT OF THE PROFILE OF CROSS-SECTION
NACA0015 EPPLER 478 BaselineCLARK YM-15
NACA 0015
CLARK YM-15
EPPLER 478
Baseline
LES, time averaged for t = 4s to 15s, @ x =1.5 m
@ z = 0.8m
2007.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
RATIO OF MASS FLOW RATE
𝑀1 =𝑄𝑡𝑜𝑡𝑎𝑙𝑄𝑖𝑛𝑙𝑒𝑡
𝑀2 =𝑄𝑏𝑎𝑐𝑘𝑄𝑖𝑛𝑙𝑒𝑡
Effect of slit width Effect of cross-section height
Effect of slit location Effect of profile of the cross-section
2107.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
AEROACOUSTIC CHARACTERISTICS
@ x = 1.5m
@ x = 0.1m
– Acoustic model: FW – H model
– Density: 𝟏. 𝟐𝟐𝟓𝐤𝐠/𝐦𝟑
– Sound speed: 𝟑𝟒𝟎𝐦/𝐬
– Reference acoustic pressure: 𝟐𝟎𝛍𝐏𝐚
– Noise source: Bladeless fan
Sound pressure level
x = 1.5m
Receiver 1
z = 0.8m
z
x
x = 0.1m
Receiver 2
2207.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
EFFECT OF THE GEOMETRIC PARAMETERS ON AEROACOUSTIC PERFORMANCE
Effect of slit width Effect of cross-section height
Effect of slit location Effect of profile of the cross-sectionx = 1.5m
Receiver
z = 0.8m
z
x
c
H
d=2mm, H=3cm, c=12cm, x0/c=10%
x0
2307.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
CONCLUSIONS
— When the wind produced by the bladeless fan becomes more
powerful, the aerodynamic noise is louder.
— With the decrease of the slit width, the wind strength becomes
more powerful. The generated noise increases at the same time.
— The bladeless fan with the cross-section of 4cm has the best
aerodynamic performance, but the generated noise is the
loudest.
— With the slit moves away from the leading edge, both wind
strength and noise level increase.
— The profile of the cross-section affect the shape of the influence
zone, but has insignificant effect on outflow mass flow rate and
the generated noise.
2407.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
ONGOING EFFORT
— Investigate the performance of the bladeless fan prototype with
the impeller in the base
— Identify the main noise source
— Analyze the noise directivity of the bladeless fan
— Come up with a general criteria to evaluate the aerodynamic
performance of the bladeless fan (i.e. strength, uniformity and
steadiness of the wind)
— Propose a criteria to evaluate the compromise between the
aerodynamic and aeroacoustic performance
— Apply the results to optimize the design of the new-generation
bladeless fan.
2507.28 - 08.01, 2019, San Francisco, CA, USA AJKFLUIDS 2019-5220
ACKNOWLEDGEMENT
• Thanks to the financial support and professional feedback
provided by Midea Global Innovation Center