Development of a SCR System for a Dual Line Exhaust by ...€¦ · Development of a SCR System for a ... • Only final validation on engine test bench ... • Optimized outlet cone

International Symposium on Modelling of exhaust-gas after-treatment

Bernd Amon, Herbert Albert, Faurecia

Johann Wurzenberger, Moritz Frobenius, AVL

Development of a SCR System for a

Dual Line Exhaust by Using Two-

Phase Flow CFD Calculations

2MODEGAT, 15. September 2009

� Motivation

� Analysis of the Basic Design of the Exhaust System

� Applied CFD Methods

� Test bed Verification

� Conclusions

CONTENT


� Motivation

� Analysis of the Basic Design of Exhaust System



� Conclusions

CONTENT


Additional DeNOx• LP-EGR• NOx Storage Catalysts• SCR

Europe

NOx[g/km]

USA

0.2 0.3 0.4 0.50.1

JP 2005

JP 2002

JP 2009

PM [g/km]

0.02

0.03

0.04

0.01

0.05

NOx[g/km] 0.4 0.3 0.2 0.10.5

Japan

Tier 2 / Phase In (2004)

Tier II Bin 8 (2004)

Tier II Bin 5 (2009)

EU 3 (2000)

EU 4 (2005)EU 5(2009)

EU 6(2014)

PM [g/km]

0.04

0.03

0.02

0.05

0.01

EMISSION LIMITS – LDV DIESEL


NH3-SCR

NSC +Tier2 Bin5

Tier2 Bin8/ Euro 6

Euro 5

DeNOx efficiency

NSC

LP-EGR

Vehicle weight

MercedesE320 BT1

MercedesE320 BT2

VW Jetta US Mercedes R/ML/GL320

BMW335d

BMW330d

RenaultEspace 2l

BMW X5

Audi Q7Audi A4

VW Passat

announced

In series

• Primarily heavy vehicleswith big engines will useSCR technology

APPLICATION DeNOx - Technologies


Diesel

EDC

DPFDOC

SCRcatalyst

SCR SystemDosing system Tank

NOx/NH3Sensor

NOxSensor

Reducing agent

„AdBlue“(NH2) 2CO

Hydrolysiscatalyst

NH3-slipcatalyst

SCR mixer

Slow4 NH3 + 2 NO2 + O2 ⇒ 3 N2 + 6H2O

Fast2 NH3 + NO + NO2 ⇒ 2 N2 + 3 H2O

Standard4 NH3 + 4 NO + O2 ⇒⇒⇒⇒ 4 N2 + 6 H2O

AmmoniakAdBlue (urea/water)NH22HN

O

CNH3 + HO C N

Isocyanic acid

Thermolysis

+ H2ONH3 + CO2

Hydrolysis

SCR SYSTEM


NH3NOxNOx NH3

• To receive a high reduction rate on NOx by the SCR catalyst a very good distribution of the reducing agent on the catalyst surface is necessary

UNIFORM DISTRIBUTION OF “AD BLUE”

NOx NOx NH3NH3

• complete NOx-reduction (theor.)

• no NH3-slip

• NH3-slip

• lower NOx-reduction

or


Starting Design• Dual pipe• 2 SCR catalysts• Flex pipe in front of catalyst• No location for injection

DevelopmentConcept• Lean – use simulation/

prediction• Only final validation on

engine test bench

Optimized Packaging• Location for injection optimized• 1 SCR catalyst with optimized

geometry• Optimized outlet cone

Basic design

Find concept to use only oneAdBlue injection

SCR FOR V-ENGINES4 ltr - turbocharged


� Motivation




� Conclusions

CONTENT


AdBlue injection in one pipe (basic 1)

AdBlue

• With one AdBlue injection valve the ammonia distribution on the catalystsurface is not sufficient (left)

• With one AdBlue injection valve the ammonia distribution on the catalyst surface is notsufficient (left)

• With two AdBlue injection valves the CFD calculation shows a better uniformity of ammonia (right), but at higher costs

AdBlue injection in two pipes (basic 2)

AdBlue

AdB

lue

ANALYSIS OF “BEST vs. WORST CASE”CFD Simulation - Results


Swirl Cone Design CFD-calculations (single-phase, steady state)

Distribution of passive scalar

Basic Swirl

DESIGN OPTIMIZATION AND VALIDATION


� Motivation




� Conclusions

CONTENT


CFD-SCR-SIMULATIONFluid Properties and Multi-component evaporation and thermoysis

-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

0 20 40 60 80 100T (°C)

log

( ηη ηη /

cP)

Urea (Jaeger, 1965)

Water (Jaeger, 1965)

Urea (correlation)

Water (FIRE 8.x)

Temperature and composition dependentmodelling of

� liquid density, viscosity, specific heat

� solution vapour pressure

Properties for gaseous urea

� vapour heat capacity

� vapour dynamic viscosity

Spray / gas phase

� multi-component evaporation

� thermolysis

� hydrolysisH 0 (l)2

H 0 (g)2

H 02

(NH ) CO2 2

(NH ) CO (s or l)2 2

(NH ) CO (g)2 2

NH (g) + HNCO (g)3

(NH ) CO (s or l)2 2

(NH ) CO (g)2 2


CFD-SCR-SIMULATIONSpray and Wallfilm modelling

Advanced Spray-Wall Modells

� Multicomponent wallfilm evaporationand thermolysis

� Modelling of heat transfer betweendroplets and wall (Wruck-Meingast)

� Wall temperatur dependent splashingmodel (Kuhnke with BirkholdExtension)

� Accounting for heat conduction in solid walls via lateral heat conduction

4/12/1

4/54/3)(

dd

ddd uDK

µσρ=

Sat

Wall

T

TT =*

0 10050 150

0.8

0.9

1.0

1.1

1.2

1.3

1.4

Thermal breakup

Deposition Splash

Rebound

200

D. Kuhnke. Spray Wall Interaction Modelling by Dimensionless Data Analysis. PhD thesis, TU Darmstadt 2004.

N. W. Wruck. Transientes Sieden von Tropfen beim Wandaufprall. PhD thesis, RWTH Aachen, 1998.


CFD-SCR-SIMULATIONModel validation

Schwarzenberg, M. Untersuchung von Spraykonzepten zur Dosierung von Harnstoff-Wasser-Lösung beim Einsatz eines SCR-Verfahrens. Diplomarbeit, RWTH Aachen, 2005

F. Birkhold, U. Meingast, P. Wassermann, O. Deutschmann. Modeling and simulation of the injection of urea-water-solution for automotive SCR DeNOx-systems. Applied Catalyst B 70 (2007), 119-127

Lichtschnittvisualisierung Simulation


Heat conductivitySingle wall tube s/λ = 6·10-5 (m²K)/W

Decoupling element s/λ = 7.5·10-2 (m²K)/W

Flange s/λ = 5·10-2 (m²K)/W

Converter cover s/λ = 3.55·10-2 (m²K)/W

Cones s/λ = 8·10-5 (m²K)/W

Heat transfer outside αa = 10 W/(m²K)

Radiation

Emission coeff ε = 0.5 @ 30 °C

Simulation

Thermo camera

CFD-SCR-SIMULATIONEnergy


2mm wall

EKE

catalyst

1.5mm wall

Wall boundary conditions withheat transfer

Inlet right branch

Inlet leftbranch

Outlet

Spray

block-structured hex-mesh with 600491 cells

SCR-Cat:A=0.0188m²V=0.0045m³400cpsi/4.5milwashcoat 56µm

CFD-SCR-SIMULATIONMeshing


Basic Design Swirl DesignOP B

CFD-SCR-SIMULATIONResults


� Motivation




� Conclusions

CONTENT


Swirl

Basis

Engine: Diesel V8, 4.2 ltr, turbochargedMax. power: 240 kW @ 3750 rpmMax torque: 760 Nm @ 1800...2500 rpm

Operating Points:

390160 [Nm]Load

700136[kg/h]Mass Intake Air

300

1700

A

450[°C]T before SCR

3200[rpm]Speed

BOperating point (OP)

ENGINE TEST BENCH INVESTIGATIONS

Dosing strategy

250 ms

108.3 ms

3.3 msOP A

OP B


Temp

Temp

TempTemp

Gas Pre

Gas Pre

GasPost

FTIRGas divider

Temp

AdBluevalve

AdBluevalve

ENGINE TEST BENCH SET-UP


Gas divider

cn

ccn

ii

21 1∑

=

−−=γ

Mapping: 48 NOx + NH3 sampling points

NOx (ppm)

550-600500-550450-500400-450350-400300-350250-300200-250150-200100-15050-1000-50

NOx DISTRIBUTION MEASUREMENTS


Basis Swirl

NOx (ppm)

80-9070-8060-7050-6040-5030-4020-3010-200-10O

P A

NOx (ppm)

550-600500-550450-500400-450350-400300-350250-300200-250150-200100-15050-1000-50

0.760.76

γγγγNOx = 0.69γγγγNOx = 0.69

NOx (ppm)

40-5030-4020-3010-200-10

NOx (ppm)

270-300240-270210-240180-210150-180120-15090-12060-9030-600-30

0.960.96

0.950.95

AdBlue

NOx (ppm)

50-6040-5030-4020-3010-200-10

NOx (ppm)

300-350250-300200-250150-200100-15050-1000-50

Basis 2

OP

B

0.840.84

0.850.85

AdBlue

AdB

lue

AdBlue

NOx DISTRIBUTION MEASUREMENTSResults


Simulation Measurement

0-75

75-150

150-225

225-300

300-375

375-450

450-525

525-600

NOx [ppm]

7

7x

8

CFD-SCR-SIMULATIONResults basic design– comparison with engine bench


Simulation

0-37.5

37.5-75

75-112.5

112.5-150

150-187.5

187.5-225

225-262.5

262.5-300

NOx [ppm]

Measurement

7

7x

8

CFD-SCR-SIMULATIONResults swirl design– comparison with engine bench


� Motivation




� Conclusions

CONTENT


� Advanced CFD models for ad-blue sprays and spray-wall interaction

have been applied � accurate prediction of NH3-uniformity in good

correlation with test bed results

� Successful development of a high performance SCR system for a dual

line exhaust system (V8-engine) � Swirl cone design allows a high

performance of the SCR catalytic converter

� In such exhaust system only one AdBlue injection is necessary to

achieve a sufficient ammonia distribution on the SCR catalyst �

Reduction of system costs and complexity of SCR control

� The application of accurate simulation-tools enables a fast and cost-

effective virtual system development

CONCLUSIONS

International Symposium on Modelingof exhaust-gas after-treatment

Development of a SCR System for a

Dual Line Exhaust by Using Two-

Phase Flow CFD Calculations

Bernd Amon, Herbert Albert, Faurecia

Johann Wurzenberger, Moritz Frobenius, AVL

Documents

Development of a SCR System for a Dual Line Exhaust by ...€¦ · Development of a SCR System for a ... • Only final validation on engine test bench ... • Optimized outlet cone