1. System Simulation for Aftertreatment University Perspective
Christopher J. Rutland
Engine Research Center
University of Wisconsin - Madison
UW ERC – CLEERS April 21, 2010

2. Aftertreatment System Modeling
Study device-to-device interactions
Study transients: load, speed
Use integrated system model
GT-Power Engine and Exhaust Model
PM and NOx Models
Tail Pipe Emissions
DOC
DPF
LNT
SCR
Engine Feedback and Controls
SCR - DPF
Matlab Simulink
UW ERC – CLEERS April 21, 2010

3. System Integration Development
Collect device models
Develop some in house
Obtain others from partners (primarily GM)
Use appropriate level of model fidelity
Individually tested and calibrated
Emphasis on integrating models
Device interaction
Transient simulation
Simple controls for operating system
UW ERC – CLEERS April 21, 2010

4. Funding University Research
Government
Supports longer term, more basic research
National priorities to support research communities
Does not expect immediate payoff
High risk research is OK
May solicit industry input (e.g. DOE)
Good match for university objectives and time scales
Industry
Provides real world problems: Relevance
Different priorities than universities
UW ERC – CLEERS April 21, 2010

5. University Industry Train students Focus on basics
Long term funding
Pursue interesting phenomenon
Explore to understand
Creativity comes from exploration
Make a profit
Emphasis on near term
Short term
Must solve problems
Once solved, move on
Explore to solve problems
Creativity comes from need
UW ERC – CLEERS April 21, 2010

6. Industry – University: Cautions
Students need long term commitment
Mission critical projects may not match university capabilities
IP ownership and proprietary information can be problematic
Increases closer to production
UW ERC – CLEERS April 21, 2010

7. GM – UW ERC Cooperative Research Lab
Success story
Continuous existence for over 10 years
Project topics are developed in close collaboration
Active participation of GM researchers in ERC projects
GM commitment to students and program
UW ERC – CLEERS April 21, 2010

8. Education Primary goal of universities Training process
Partially trained people working on projects
Experience levels are low
May not always find the most appropriate student for a project
Commitment to helping students achieve their educational goals
UW ERC – CLEERS April 21, 2010

9. Examples Using system simulations to explore aftertreatment issues
1. DPF loading vs. regeneration frequency
Impact on fuel economy
2. Using DPF thermal inertia
Both projects supported by UW-GM CRL
UW ERC – CLEERS April 21, 2010

10. DPF Regeneration Study
Exhaust Temperatures for 537 C DPF Regeneration
Exhaust Temperatures for 566 C DPF Regeneration
UW ERC – CLEERS April 21, 2010

11. Impact of Regeneration Temperature
Mass of PM in DPF for 537 C DPF Regeneration
Mass of PM for 566 C DPF Regeneration
UW ERC – CLEERS April 21, 2010

12. Pressure Drop Pressure Drop 537 C DPF Regeneration
Reduction in PM loading of DPF
Exhaust gas cools
Increase volumetric flow rate + DPF inlet temp
UW ERC – CLEERS April 21, 2010

13. Impact on Fuel Economy
Brake Specific Fuel Consumption 537 C DPF Regeneration
Brake Specific Fuel Consumption 566 C DPF Regeneration
Engine + DOC fuel injection
Engine + DOC fuel injection
Engine only
Engine only
UW ERC – CLEERS April 21, 2010

14. DPF Regeneration Strategy Study
Mass of PM Trapped in the DPF
566 C DPF Regeneration
UW ERC – CLEERS April 21, 2010

15. Regeneration Impact on Fuel Economy
10-loading
6 loading
4 loading
2 loading
1 loading
1.5 2
2.5 3
3.5 4
4.5 5
5.5 1
% Fuel penalty due to back pressure 6
Maximum amount of loading in DPF, g/l
% Regeneration fuel penalty
Trade off
point
Regeneration fuel penalty
Regeneration Fuel Penalty
Trade off Point
Engine Fuel Penalty
Back pressure fuel penalty
UW ERC – CLEERS April 21, 2010

16. Oxidation Rate and Thermal Inertia
800
1600 10 20 30 40
Time [s]
Soot oxidation rate [mg/s]
Mass of soot [g]/
0.5 1
1.5 2
x 10 -4
Exhaust fuel rate [kg/s]
Trapped soot
Soot oxidation rate
Minimum soot target
Fuel rate
Thermal inertia
Soot continues to be consumed after fuel injection stops
Opportunities for optimization
Oxidation rate decreases
Constant temperature
Decreasing amount of soot
UW ERC – CLEERS April 21, 2010

17. Summary University system simulation
Training students
Should focus on basics
Can greatly benefit from industry ties when done correctly
Integrated system useful for studying device interactions and transients
UW ERC – CLEERS April 21, 2010