27 vac hvac duct sensitivity study · 2021. 4. 29. · virtual.lab insertion loss. ... frequency...
TRANSCRIPT
Vibro-Acoustics Consortium
HVAC Duct Aspect Ratio Sensitivity Study
Caoyang LiUniversity of Kentucky
March 18, 2021
Vibro-Acoustics Consortium 2
Overview
• Simulation Approach in Siemens Simcenter
• Aspect Ratio Sensitivity Study
• Improving the Attenuation with Large Aspect Ratios
Vibro-Acoustics Consortium 3
𝐼𝐿 𝐿 , 𝐿 ,
Source
Source
𝐿 ,
𝐿 ,
Insertion Loss
Vibro-Acoustics Consortium 4
ASTM E477 Test setup
20 Monopoles Rigid Ductwork Structure FEM
Poroelastic FEM
Automatically Matched Layer Automatically Matched Layer
Test Setup
Vibro-Acoustics Consortium 5
20 Monopoles Duct Air FEM
Structure FEM
Poroelastic FEM
Automatically Matched Layer
Automatically Matched Layer
Siemens Simcenter FEM Model10 ft test section (total length 20 ft). Duct wall thickness is 0.034 in (21 gage). Sound absorption is fiber with flow resistivity of 17,700 Rayls/m.
Vibro-Acoustics Consortium 6
Poroelastic MeshStructural Mesh (with beam brace support)
Cross-section view of mesh (left) and schematic (right).
Siemens Simcenter FEM ModelStep 1 Insertion Loss
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Structural FEM
Automatically Matched Layer
Acoustic FEM
Acoustic FEMAutomatically Matched Layer
Structural FEM
Siemens Simcenter FEM ModelStep 2 Breakout Transmission Loss
Vibro-Acoustics Consortium 8
‐10
0
10
20
30
40
50
60
70
50 100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
16 in x 48 in Duct of 20 ft long with 10 ft lining (2 in glass fiber at all sides)
Simcenter
Virtual.Lab
Insertion Loss
Vibro-Acoustics Consortium 9
Breakout Transmission Loss
0
10
20
30
40
50
60
70
50 100 200 400 800 1600 3200
Breakout Transmission Loss (d
B)
Frequency (Hz)
16 in x 48 in Duct with 10 ft lining (2 in thick glass fiber)
Simcenter
Virtual.Lab
Vibro-Acoustics Consortium 10
Overview
• Simulation Approach in Siemens Simcenter
• Aspect Ratio Sensitivity Study
• Improving the Attenuation with Large Aspect Ratios
Vibro-Acoustics Consortium 11
18”
48”
22”
48”
48”16”
48” 48”
Sensitivity Study Constant Height
ℎ𝑤 3 ℎ
𝑤 2.67ℎ𝑤 2.18
𝑡 2"
ℎ𝑤 1
2𝑡𝑤
14
2𝑡𝑤
29
2𝑡𝑤
211
2𝑡𝑤
212
Vibro-Acoustics Consortium 12
‐10
0
10
20
30
40
50
60
70
80
90
50 100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
16in x 48in
18in x 48in
22in x 48in
48in x 48in
Insertion Loss Constant Height
Vibro-Acoustics Consortium 13
18”
48”
Note: 2 inch fiber on sides.
𝑡 2"
18”
24”
18”
30”
18”
36”
18”
42”
ℎ𝑤 1.33
ℎ𝑤 1.67
ℎ𝑤 2
ℎ𝑤 2.33
ℎ𝑤 2.67
2𝑡𝑤
29
2𝑡𝑤
29
2𝑡𝑤
29
2𝑡𝑤
29
2𝑡𝑤
29
Sensitivity Study Constant Width
Vibro-Acoustics Consortium 14
‐10
0
10
20
30
40
50
60
70
80
90
50 100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
18in x 24in18in x 30in18in x 36in18in x 42in18in x 48in18in x 54in
Insertion Loss Constant Width
Vibro-Acoustics Consortium 15
Overview
• Simulation Approach in Siemens Simcenter
• Aspect Ratio Sensitivity Study
• Improving the Attenuation with Large Aspect Ratios
Vibro-Acoustics Consortium 16
2 in lining on all sides
Improvements Increase Absorption
16”
48”
𝑡 2"
4 in lining on top / bottom
16”
48”
𝑡 4"
Vibro-Acoustics Consortium 17
‐10
0
10
20
30
40
50
60
50 100 200 400 800 1600
Insertion Loss (dB
)
Frequency (Hz)
2 in on All Sides
4 in Top / Bottom
Insertion Loss Thicker Absorption
Vibro-Acoustics Consortium 18
2”4” 6”
8”18”
48”
2” on all sides 4” on top / bottom 6” on top / bottom 8” on top / bottom
2” 2” 2”2”
Improvements Increase Absorption
Vibro-Acoustics Consortium 19
‐10
0
10
20
30
40
50
60
70
50 100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
2in at all sides
4in at short sides
6in at short sides
8in at short sides
Insertion Loss Thicker Absorption
Vibro-Acoustics Consortium 20
‐10
0
10
20
30
40
50
60
70
50 100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
2in at all sides
8in at short sides
10in at short sides
12in at short sides
Insertion Loss Thicker Absorption
Vibro-Acoustics Consortium 21
10 ft
20 ft
Improvements Add Length
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0
20
40
60
80
100
100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
10ft 2in at all sides
20ft 2in at all sides
0
20
40
60
80
100
100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
10ft 4in at short sides
20ft 4in at short sides
0
20
40
60
80
100
100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
10ft 6in at short sides
20ft 6in at short sides
0
20
40
60
80
100
100 200 400 800 1600 3200
Insertion Loss (dB
)
Frequency (Hz)
10ft 12in at short sides20ft 12in at short sides
Insertion Loss Add Length
Vibro-Acoustics Consortium 23
Summary
• FEM Simcenter was used successfully to predict the insertion loss and breakout transmission loss.
• The smallest cross-sectional dimension drives the insertion loss performance.
• Performance can be improved by increasing the sound absorption thickness at the top / bottom of the duct assuming the height is the longest dimension.