Tailpipe Acoustics and Backpressure Predictions of Exhaust ......Tailpipe Acoustics and Backpressure...
Transcript of Tailpipe Acoustics and Backpressure Predictions of Exhaust ......Tailpipe Acoustics and Backpressure...
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
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Rel
ativ
e B
ackp
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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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Frequency (Hz)
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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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Frequency (Hz)
Ins
ert
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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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