This paper analyses the operation of the SCR aftertreatment system when using conventional diesel and biodiesel, to explore the characteristics of the NOx sensor and to analyze its behavior of NOx detection in real applications with the engine using biodiesel.

1. Impacts On The Emissions Monitoring
System
(OBD) Due To The Use Of Biodiesel And
Higher Nox
Emissions
Leonardo de Oliveira Costa
IAV do Brasil
Rodrigo Silva Santos
IAV do Brasil
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2. - INTRODUCTION TO OBD
• To achieve the new emission standards (PROCONVE P7 2012), it will be needed
to control and monitoring (OBD) of exhaust gas emissions (NOx and PM);
• For engines with SCR as exhaust gas treatment technology, it will be mandatory
monitoring of exhaust gas emissions using a NOx sensor in the exhaust pipe;
• When above OBD emissions tolerances for NOx emissions, the ECU must actuate
in the engine and advise the driver;
- RENEWABLE FUELS
• The automotive industry is always looking for renewable fuels to reduce the
dependency on petroleum. Nowadays the biodiesel is the renewable fuel to replace
the diesel;
• The biodiesel has benefits about reduction of major components on the emissions
gases, ONLY increase on the NOx emissions;
• The brazilian government has a plan to increase the amount of biodiesel in the
common diesel in some years;
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5. - OBJECTIVE OF THE PROJECT
• Analysis the increase of NOx emissions when the engine is fueled by biodiesel
(B100) to study the influence on OBD thresholds and diagnosis.
- Tested Engine
7 liters, 6 Cylinder in Line, 4 Valves, 300HP @ 2400rpm, common-rail, EURO V
with SCR
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9. Diesel
Global Value = 1,97g/kWh
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10. B100
Global Value = 2,6g/kWh (Increase of 32%)
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11. Maximum increase of 80,8%
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12. • SCR System Overview
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14. System Design 1
• Diesel
• 1 NOx Sensor Downstream + Sensor Model Upstream
•Open Loop Dosing Control η= 60% > 30%
Ok!
1000 ppm 400 ppm
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15. System Design 1
• B100
• 1 NOx Sensor Downstream + Sensor Model Upstream
•Open Loop Dosing Control η= 28% < 30%
Not Ok!
1000 ppm
720 ppm
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16. System Design 2
• Diesel
• 1 NOx Sensor Downstream + 1 NOx Sensor Upstream
η= 60% > 30%
Ok!
1000 ppm 400 ppm
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17. System Design 2
• B100
• 1 NOx Sensor Downstream + 1 NOx Sensor Upstream
η= 60% > 30%
Ok!
1800 ppm 720 ppm
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18. System Design 3
• Diesel
• 1 NOx Sensor Downstream + Sensor Model Upstream
•Close Loop Dosing Control η= 60% > 30%
Ok!
1000 ppm 400 ppm
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19. System Design 3
• B100
• 1 NOx Sensor Downstream + Sensor Model Upstream
•Close Loop Dosing Control η= 28% < 30%
Not Ok!
1000 ppm
720 ppm
400 ppm
η= 60% > 30%
Ok!
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20. - Conclusion
• Biodiesel has a direct impact on NOx emissions value;
• and also on OBD threshold values and detection;
• on SCR System Design with only one NOx sensor, at least a close loop control
should be consider and also a low efficiency during normal Diesel operation to
make possible a efficiency increase during Biodiesel operation;
• Also a NOx sensor upstream the catalyst can be used to avoid wrong efficiency
detection and also to detect the use of Biodiesel
• Further research should be done with SCR System Design and also Biodiesel
Sensor.
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21. Thank you!
Leonardo de Oliveira Costa
leonardo.costa@iav.de
Rodrigo Silva Santos
rodrigo.silvasantos@iav.de
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