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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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Active Electric Valve usage example

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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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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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• 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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• 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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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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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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• 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

0

1

2

3

4

5

6

7

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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• 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

0

2

4

6

8

10

12

14

16

18

20

40 50 60 70 80 90 100

Frequency (Hz)

Ins

ert

ion

Lo

ss

(d

B)

2.0 IL

TL - Valve Closed



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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• 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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