Tailpipe Acoustics and Backpressure Predictions of Exhaust ......Tailpipe Acoustics and Backpressure Predictions of Exhaust Systems with Active and Passive Valves Technologies Utilizing

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

4


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

15

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Documents

Tailpipe Acoustics and Backpressure Predictions of Exhaust ......Tailpipe Acoustics and Backpressure Predictions of Exhaust Systems with Active and Passive Valves Technologies Utilizing