Onboard Emissions Monitoring on a HD Truck with an SCR System Using Nox Sensors

Lothar Hofmann; Klaus Rusch; Stefan Fischer; Bertrand Lemire

doi:10.4271/2004-01-1290

2004-03-08

Onboard Emissions Monitoring on a HD Truck with an SCR System Using Nox Sensors 2004-01-1290

SCR technology has proven its ability to significantly reduce NO_x emissions. Hence it has become an outstanding solution to be used to meet future emission limits in Europe, Japan and North America. To add even more confidence towards the introduction of SCR technology, the implementation of NO_x sensors will become mandatory for on-board emission control systems.

To demonstrate the usefulness of NOx sensors, a typical North American On-Highway Truck was chosen as a demonstration vehicle. It was equipped with vertically mounted, extruded SCR catalysts, a urea dosing system, and NO_x-sensors.

In order to achieve EURO 5 or even lower emission limits in NO_x and PM, attempts were made to equip the system with oxidation catalysts upstream of the SCR catalyst as well as upstream of the turbine. Some changes had to be made to the model year 2000 engine calibration to reduce PM emissions to EURO 4 and 5 levels.

The system was calibrated and then tested according to different HD test procedures on a transient test bench. NO_x emissions were determined by CLD and NDIR analyzers and by state of the art NO_x sensors.

After completion of the test bench work, the catalyst system was transferred to the test truck and the final system calibration was copied from the test bench ECU to the vehicle ECU. On-road NO_x measurements were gathered by using NDIR-analyzers and NO_x sensors.

Based on our previous experience with HD trucks, it can be stated that the introduction of NO_x sensors is an appropriate method to monitor NO_x conversion performance of SCR systems and also to adapt the system to compensate for various disturbances.

Ongoing evaluation of the test truck in the future will include NO_x sensor performance, implementation of the NO_x signal into the dosing control algorithms, as well as on-road durability testing.

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Onboard Emissions Monitoring on a HD Truck with an SCR System Using Nox Sensors 2004-01-1290

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