Tailpipe Acoustics and Backpressure Predictions of Exhaust Systems
with Active and Passive Valves Technologies Utilizing GT-POWER
November 6th 2017
Plymouth, Michigan, USA
Gabriel Ostromecki
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GT-POWER – Valves backpressure and tailpipe noise simulations
Agenda
• Valve usage in exhaust systems
– Active Electric Valves - usage examples
– Passive Spring Valves – usage examples
• Spring valves – GT-POWER simulation techniques
• Duct acoustics – Why do valves reduce tailpipe noise acoustics?
• GT-POWER spring valve simulation acoustic correlation
• Summary
Passive Spring In-Flow valve
Active Electric Valve
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GT-POWER – Valves backpressure and tailpipe noise simulations
Active Electric Valve usage example
• Electric Valves for Tailpipe noise Acoustics
– Dual mode mufflers Controllable vehicle loudness and system backpressure
Tailpipe Sound
Quality Valve
Cylinder
Deactivation
Valve
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GT-POWER – Valves backpressure and tailpipe noise simulations
Passive Spring Valves usage examples
• Spring Valves – Passive valves for increased attenuation with Backpressure hit
– Good attenuation on low engine flow rates (low RPM)
– Lower exhaust backpressure on high engine flow rates (high RPM)
Valve Closed Path Valve Open Path
1. Spring-Loaded Flapper Valve
2. In-Flow
Spring-Loaded Valve
Closed at low flow
Open at High flow
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GT-POWER – Valves backpressure and tailpipe noise simulations
Passive Spring Valves usage examples
• 1. Flapper spring valve restriction mechanical model
– Dual flow muffler w/ restriction path when valve closed
Valve Closed Path Valve Open Path
1. Spring-Loaded Flapper Valve
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GT-POWER – Valves backpressure and tailpipe noise simulations
Passive Spring Valves usage examples
• 1. Flapper spring valve restriction mechanical model
• GT-POWER template tuned for flow measured results
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 50 100 150 200 250 300 350 400 450 500
Rel
ativ
e B
ackp
ress
ure
(inH
g)
Mass Flow Rate (SCFM)
Valve Cold Flow @ Room Temperature
Bench Data GT-Power
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GT-POWER – Valves backpressure and tailpipe noise simulations
Spring Valves backpressure results example
• 2. In-Flow spring valve as variable restriction in exhaust system
– High restriction in low flow velocities
– Low restriction in high flow velocities
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2. In-Flow
Spring-Loaded Valve
Closed at low flow
Open at High flow
Idle, POT WOT high RPM
WOT low RPM
Lugging
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GT-POWER – Valves backpressure and tailpipe noise simulations
Spring In-flow Valves modeling correlation
• 2. In-Flow spring valve modeled as orifice connection
with valve equivalent open area
– GT-POWER model tuned to match measured pressure drop
Valve element
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GT-POWER – Valves backpressure and tailpipe noise simulations
Spring In-flow Valves modeling correlation
• Why in-flow spring, or electric valves works?
– Valve closed measured Acoustic Transmission Loss
– No effect of restriction measured without flow
Equivalent valve closed orifice
In flow spring valves or orifice in closed
electric valve are invisible for
transmission loss measurement w/o flow
50.8 Dia HP Valve
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2
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8
9
10
0 500 1000 1500 2000 2500 3000
Frequency (Hz)
Tra
ns
mis
sio
n L
os
s (d
B)
HP Valve Open
HP Valve Closed
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GT-POWER – Valves backpressure and tailpipe noise simulations
Spring In-flow Valves modeling correlation
• Valve modeled as orifice connection with closed valve equivalent area
– GT-POWER Transmission Loss simulation as in measurements shows
no significant effect of valve restriction
Valve element
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• Duct acoustics - sound pressure vs. particle velocity
– Insertion loss from engine results with flow
shows great benefits of valves restriction
50.8 Dia HP Passive Valve in Outlet Pipe of Muffler
Insertion Loss - I-4 Engine
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2
4
6
8
10
12
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40 50 60 70 80 90 100
Frequency (Hz)
Ins
ert
ion
Lo
ss
(d
B)
2.0 IL
TL - Valve Closed
GT-POWER – Valves backpressure and tailpipe noise simulations
Spring In-flow Valves modeling correlation
sound pressure pattern in pipe
velocity antinodepressure node
velocity nodepressure antinode
velocity antinodepressure node
1st resonant frequency
Insertion Loss
Valve Open – Valve Closed
Engine measurement dominant order
Transmission LossPressure difference reduce pipe resonance
in high particle velocity patterns
Equivalent valve closed orifice
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GT-POWER – Valves backpressure and tailpipe noise simulations
Spring In-flow Valves modeling correlation
• Measurements vs. GT-POWER acoustic tailpipe noise correlation
Valve location
1st resonant frequency – 120Hz
sound pressure pattern in pipe
Valve open
Minor effect on pipe resonance
Valve Closed
~8dB improvement on pipe resonance
Valve Closed
~8dB improvement on pipe resonance
120Hz
120Hz
120Hz
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GT-POWER Valves Backpressure and Acoustic simulations
• Summary
– GT-POWER is appropriate tool to simulate both Backpressure and Acoustic Tailpipe noise of vehicle
exhaust systems with electric and spring valves
– Both electric valves and spring valves can be easily modeled by orifice connection with tuned pressure
loss and represent appropriate acoustic loss as well
– Mechanical representation of spring flap valves can bring very good correlation and allows to further
tune Valve geometry
Electric Valve In-Flow Valve Spring Flap Valve14
Q & A
Tailpipe Acoustics and Backpressure predictions of Exhaust Systems with Active and Passive Valves technologies utilizing GT-POWER
Gabriel Ostromecki
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