AVL List GmbH (Headquarters)

Public

Analysis of risk situations for

TWC breakdown in normal

engine and vehicle tests

Ernst Winklhofer, Alois Hirsch, Peter Hollerer

| | 27 Juni 2018 | 2Public

The TWC – three way catalyst at risk

The topic:

• Temperature• Thermoshock • „wormholes“ mechanical impact

Risk assessment in • test configurations and• in normal drive situations

content

| | 27 Juni 2018 | 3Public

TWC issues

Front face: Sintering / glassificationwash coat was exposed to high temperature

Temperature readings were neverabove 950 °C

motivation

| | 27 Juni 2018 | 4Public

TWC issues

Front face: correct

motivation

| | 27 Juni 2018 | 5Public

Inside brick: thermal distruction, thencollapse

TWC issues

Temperature readings were neverabove 950 °C

motivation

| | 27 Juni 2018 | 6Public

Front face: pitting, „wormholes“Inside brick: correct

TWC issuesmotivation

| | 27 Juni 2018 | 7Public

Risk assessment – the questions

„Wormholes“ Sintering Brick damage

Why such damages ?• None of these events showed exceptionally high temperatures.• What is causing such front end damage

content

| | 27 Juni 2018 | 8Public

TWC test instrumentation

1 Lambda

2 TC – thermocouple

3 Endoscope

4 IR - temperature

1

2

3

4

In vehicle or on engine test bed

| | 27 Juni 2018 | 9Public

Wormholes

| | 27 Juni 2018 | 10Public

The wormholes

TWC issues: what we can see

Movie 1

Droplet impact normal

Tem

p[°

C]

Cylpr. [

bar]

DT [

°C/m

s]

IR signal traces with and withoutdroplet presence

Occasional view withendoscope and high speed camera

Continuous signalrecording with IR fibersensors

And then ?

| | 27 Juni 2018 | 11Public

TWC issues: what we can do

Droplet impact normal

Tem

p[°

C]

Cylpr. [

bar]

DT [

°C/m

s]

IR signal traces with and withoutdroplet presence

And then ?

• Cam phasing: precise adjustment to temperature conditions.• IR sensor: shows immediate response to calibration effect• TWC: stays free of wormhole damages

| | 27 Juni 2018 | 12Public

Sintering

The conflict:• Exhaust gas temperature sensor confirms

maximum temperature to never exceed 950 °C

• Washcoat: temperature is far above 1000 °C

| | 27 Juni 2018 | 13Public

What is the real TWC temperature ?

TWC brick

IR sensor responds tothermal radiation ofTWC surface

TC sensor withthermal inertia

| | 27 Juni 2018 | 14Public

The gear shift engine interrupt

See the real TWC response:

• From thermal imaging movies• With a simple fiber optic IR

sensor

What is the real TWC temperature ?

Thermal radiationpeak is up to 1200 °C

Thermocouple

| | 27 Juni 2018 | 15Public

Internal brick damage

maximum temperature never exceeds 950 °C

| | 27 Juni 2018 | 16Public

TWC front and center sensors

| | 27 Juni 2018 | 17Public

TWC front and center sensors

IR fiber opticsensor head

Sensor adapter flange

IR sensors: thermal radiation of cat surface areasTC sensors: to calibrate radiation signal at stationary operation

| | 27 Juni 2018 | 18Public

TWC signals in HEV operation

rpm

IMEP

T

Tgrad

front center

Combustion engine sequence:

➢ Start➢ High load….3000 rpm / 12 bar ➢ Shut off and re-start➢ High load….3000 rpm / 12 bar

High load 1

Re-startHigh load 2

| | 27 Juni 2018 | 19Public

A 710°

B 790°A: front

B: center

A

B

Temp

Temp. gradient

High load 1

TWC temperaturesare as expected.

Small T gradients in response to exhaustgas pulses.

| | 27 Juni 2018 | 20Public

A 450°

B 725°

What is this ?

Re-start

| | 27 Juni 2018 | 21Public

A 740°

B 790°

High load 2

Then again:

TWC temperaturesare as expected.

Small T gradients in response to exhaustgas pulses.

| | 27 Juni 2018 | 22Public

A 450°

B 725°

Re-start after short shut off

What is this ?

➢ TWC front: 450° andrising with everycombustion cycles.

➢ TWC center: 725°and falling – risingwith strong temperatureoscillations

| | 27 Juni 2018 | 23Public

Exhaust gas puls cyl 1

TWC front response

TWC center response

Puls sequence details

| | 27 Juni 2018 | 24Public

Exhaust gas puls cyl 1

TWC front response

TWC center response

Puls sequence details

| | 27 Juni 2018 | 25Public

Exhaust gas puls cyl 1

TWC front response

TWC center response

And a resonant gas oscillationfollowing each exhaust puls

Puls sequence details

| | 27 Juni 2018 | 26Public

A 450°

B 725°

What is this ?

➢ TWC front: 450° andrising with everycombustion cycles.

➢ TWC center: 725°and falling – risingwith strong temperatureoscillations

Re-start after short shut off

| | 27 Juni 2018 | 27Public

What we do in engineering

The temperaturegradient targets

must avoidriskfulsafe

Achieve such targets• with a workaround in calibration• or upfront with non resonant

tubing design

| | 27 Juni 2018 | 28Public

Do we only see it in hybrid operation ?

| | 27 Juni 2018 | 29Public

20

16

12

8

4

0

DT [

°C/m

s]

low load

high load

Experimental misfire events

low load

high

medium

6000 rpm 2000 rpm

0% 0%

Resonant T - gradients in normal engines

must avoid

riskfulsafe

| | 27 Juni 2018 | 30Public

Summary

„Wormholes“ Sintering Brick damage

You can avoid post mortem analysis….

Summary - conclusion

| | 27 Juni 2018 | 31Public

Conclusion: …in vivo evaluation is the better choice

Shaft encoder, timeIndicatingThermocoupleEtc.

Fiber optic cable

Test bed or vehicle Signal recorder andreal time analyser

Test data and evaluationreport

Summary - conclusion

AVL List GmbH (Headquarters)

Public

Analysis of risk situations for

TWC breakdown in normal

engine and vehicle tests

Ernst Winklhofer, Alois Hirsch, Peter Hollerer