NOx Adsorbers for Heavy Duty Truck Engines – Testing and Simulation

N. Hakim, J. Hoelzer, Y. Liu Detroit Diesel Corporation - DaimlerChrysler Powersystems

This feasibility study of NOx adsorbers in heavy-duty diesel engines examined three configurations (dual-leg, single-leg and single-leg-bypass) in an integrated experimental setup, composed of a Detroit Diesel Class-8 truck engine, a catalyzed diesel particulate filter and the NOx absorber system. The setup also employed a reductant injection concept, sensors and advanced control strategies. The study included the development of thermal and empirical NOx absorber characteristic models. These models were further applied to the development of regeneration strategies and were used for a comparative performance analysis of the three NOx adsorber configurations. The reported steady-state experimental and simulation results show relatively high NOx conversion efficiencies, with various levels of fuel economy deterioration. Further, the findings confirm that the development of acceptable regeneration and desulfation control logics are a major technical challenge for practical NOx absorber system applications. These logics are further complicated by factors such as engine transient operation, drivability and durability.

NOx Adsorbers for Heavy Duty Truck Engines – Testing and Simulation

N. Hakim, J. Hoelzer, Y. Liu

2

Presentation Outline

• Experimental Plan

• Simulation

• Experimental Results

• Conclusions

3

Presentation Outline

• Experimental Plan– Single Leg – Dual Leg– Single Leg with Bypass

• Simulation

• Experimental Results

• Conclusions

4

Test Setup

5

Test Setup Schematic

S60, 14L Engine

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A.T. System Configurations and Catalysts

300 cpsi, 11.25” * 12” (2*6”)

100 cpsi, 11.25” * 14”

YesNoYesPost-Engine Injector

9.8 L 9.8 L9.8 LDOC

19.5 L19.5 L39 LNOx Adsorber

22.8 L22.8 L45.6 LDPF

Single Leg bypass

Single LegDual LegConfiguration

Catalyst &In-Pipe injector

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Engine Baseline Test Configuration

S60, 14L Engine

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Single Leg Configuration

S60, 14L Engine

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Dual Leg Configuration

S60, 14L Engine

(Top Leg Regenerating)

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Single Leg with Bypass Configuration (Regeneration)

S60, 14L Engine

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Presentation Outline

• Experimental Plan

• Simulation

• Experimental Results

• Conclusions

12

NOx Adsorber Efficiency

0

20

40

60

80

100

150 250 350 450 550

Exhaust temperature deg C

NO

x c

on

ve

rsio

n

eff

icie

nc

y %

High NOx reduction efficiency within the catalyst temperature range

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One-D Empirical Model

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NOx In, Out Level and Adsorption inside LNT (Steady State)

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Presentation Outline

• Experimental Plan

• Simulation

• Experimental Results– Single Leg – Dual Leg– Single Leg with Bypass

• Conclusions

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Single Leg Control Strategy

• Target: Lambda < 1 and Torque smoothness.

• Approach- Turbo vane position used to force maximum EGR

mass into intake, reducing inlet air mass. This will reduce BTRQ.

- Advanced BOI to compensate for the BTRQ drop.

- More FPC to increase richness of exhaust.

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Single Leg Results*

1.2

77 (Rich time fixed)

5/145

B25

2.05

88 (Target: lowest NOx out level)

5/80

B75

1.0

72(Rich time fixed)

3/69

A50

1.2FEP %

78(Target:Lowest NOx out level)

NOx conv. %

7/53Rich/Lean,(sec)

B100ESCMode

* Fresh Catalyst

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Single Leg Data

0

100

200

300

400

500

600

700

800

1820 1840 1860 1880 1900Time (sec)

NO

X p

pm

-4

-3

-2

-1

0

1

2

3

4

Lam

bda

Lambda

NOx In

NOx Out

B75

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Presentation Outline

• Experimental Plan

• Simulation

• Experimental Results– Single Leg

– Dual Leg– Single Leg with Bypass

• Conclusions

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Dual Leg Results*

330(2.28)480(2.62)440(2.67)210(2.36)NOx, ppm (g/hphr)

ValveSetting(sec)

2.31.93.25.9FEP, %

382427353319Temp in, C

90949692.4Conv Eff, %

OpenOpenOpenOpen

545458585252585883318842415576038520

B50A75A50A25

3 sec3 sec3 sec3 secInj duration 9258936061964280SSV(1/hr)

CloseClose

CloseClose

EURO III ESC ModeConditions

*Fresh Catalyst - Half System Operation

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Presentation Outline

• Experimental Plan

• Simulation

• Experimental Results– Single Leg – Dual Leg

– Single Leg with Bypass

• Conclusions

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Single Leg with Bypass Results *

92.5 91.0 92.5 92.0Conv. Eff, %, Across LNT

ValveSetting(sec)

1.33.01.54.0FEP, %

392 343 427 319 Temp in, C

80.482.080.483.0Conv. Eff, %, Overall

OpenOpenOpenOpen

10015140151001514015

B75B25A75A25

3 sec3 sec3 sec3 secInj duration

CloseCloseCloseClose

EURO III ESC ModeConditions

* Fresh Catalyst

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Test Results - Single Leg with Bypass*

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Presentation Outline

• Experimental Plan

• Simulation

• Experimental Results

• Conclusions

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Conclusions-Single Leg

• The simplest A.T. configuration, but engine management and performance is challenging.

• Issues:- The “Ideal” Lambda curve shape when rich.- Driveability (Torque Variation)- Durability(Liner Temperature, cylinder

pressure, turbocharger, …)- Transient control (Closed loop control on

Torque and Lambda)- Desulfation

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Conclusions- Dual Leg

• The most complex A.T. configuration, but least core engine management modification involved.

• Issues:- Valve mechanism and mechanical durability.- Space claim.- Secondary fuel injection system.- Multiple catalyst reliability. - Transient Control.- Desulfation.

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Conclusions- Single Leg with Bypass

• A compromise between the single-leg and dual-leg systems.

• Has some common features and challenges of each.

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Concluding Remarks

• A steady state NOx adsorber regeneration cycle can be designed using a NOx sensor and a Lambda sensor.

• Development of transient regeneration control logic is an order of magnitude more difficult, especially for the single leg system.

• Based on simulation, FTP NOx conversion will be only ~ 50% for the single leg system.

• Thermal stress on the cylinder kit and turbocharger during regeneration cycling must be addressed.