Background
Noise Reduction of Fans and
Auxiliary Systems
Anders Frid, Bombardier
Mats Åbom, The Marcus Wallenberg laboratory, KTH
Pascal Bouvet, Vibratec
Silence seminar “reducing noise in urban areas”, Brussels,
21 June 2006
Application example DMU
• Trend for low floor trains → more equipment on the roof
Traction motor intake 2
Brake resistor 2
Cooler 2
HVAC 3
Converter 2
Exhaust gas 2
• Cooling fans and auxiliary equipment
are important noise sources for trains
at platforms and when accelerating
• Example systems:
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Traction motor cooling system
Diesel engine cooling system
Converter cooling system
Brake resistor cooling system
Transformer cooling system
Compressors
Pumps
HVAC (heat ventilation air conditioning
unit)
– Machine room ventilation
Application example DMU
Diesel engine cooling fans
Diesel engine cooling system
is normally the most noisy
cooling system on DMUs
HVAC 2
Fresh air intake
Exhaust gas 1
Converter 1
HVAC 1
Cooler 1
Brake resistor 1
Traction motor intake 1
Diesel engine
Microphone array
measurement at
standstill
Roof-mounted cooling system
Underfloor-mounted cooling system
Typical converter cooling system
• Typical roof-mounted
diesel engine cooling
installation
Internal air
circulation
Internal fan
Coolin
g unit
Air flow indicated
Water
hoses/pipes
Noise reduction options
• Minimise cooling power need
• Improve heat exchanger efficiency
• Secure undisturbed inflow conditions to
the cooling fan
• Acoustically optimise how the cooling
fan is integrated
– Tip clearance
– Absorption
– Flow resistance
• Design a low noise cooling fan
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Type (axial, mixed-flow, radial, …)
Blade shape
Diameter
Number of blades
…
Micro-perforated plates
MWL test rig “Hartmut”
• Used in near field (close to rotor) to
absorb pressure fluctuations while
directing the flow
• Issue of investigation: high velocities
adversely affect performance of
microperforated plates
Micro-perforated plate
with slits
Micro-perforated plate
with circular holes
Simulations
• Application case: ”AGC Bi-mode”
• Measurements at standstill for
different fan and engine rpm
Mic at 7.5m
SPL vs. motor rpm
90
80
dB(A)
70
60
engine
cooling
ventilation
SUM
50
Preliminary results:
Noise map of the rotor/stator
interaction for the 3rd harmonic
40
00
50
20
21
50
50
19
50
17
18
50
15
16
50
50
50
13
14
50
50
50
12
11
10
95
0
30
95
0
Two approaches:
1. Equivalent dipole
model based on
airfoil theory
assuming known
inflow conditions
2. Hybrid method with
source term
extracted from CFDcalculations
Source ranking
motor rpm
WP E4 objectives
Conclusion:
Engine cooling fan is
the dominant noise
source when operated
at speeds > 1800 rpm
Baseline tests in lab
Sound power
110
100
LwA
• Benchmark existing solutions
• Tune calculation models for fan noise
prediction
• Investigate performance of new design
elements (micro-perforated plates, …)
• Find new low noise designs for an engine
cooler
• Build a demonstrator of a low noise engine
cooler
120
90
80
Measurement
Linear fit (exp 5.75)
70
60
100
1000
rpm
10000
FRF
Conceptual ideas
Existing design
Reversed flow
Thanks for your attention!
Radial fan and/or double layer (low+high temp) radiator