Automated Model Fit Tool for SCR Control and OBD Development 2009-01-1285
Reaching EUROVI Heavy Duty emission limits will result in more testing time for developing control and OBD algorithms than to reach EUROV emissions. It is likely that these algorithms have to be adapted for a WHTC (World Heavy Duty Transient Cycle) for EUROVI. This cycle when started cold can only be performed a limited times a day on the engine testbench, because of the cooling down time.
The development time and cost increases to reach EUROVI emission levels.
Accurate simulation tools can reduce the time and costs by reducing the amount of tests required on the testbench. In order to use simulation tools to develop pre calibrations, the models must be fitted and validated.
This paper will focus on the fit process of an SCR (Selective Catalytic Reduction) model. A unique test procedure has been developed to characterize an SCR catalyst using an engine testbench in ±2 days. This data is used in an automatic SCR fit tool to obtain the model parameters in a few days. The result is a model that predicts the NO, NO2 and NH3 SCR out concentration accurately. The fitted SCR model can predict tailpipe NOx emissions for a wide range of test cycles within 10 % (see Table 5). The validated model is used to develop and calibrate SCR control and OBD algorithms.