Modeling of NOx formation in heavy duty engines

Sammanfattning: In order to apply combustion feedback control in diesel engines to control pollution formation, good models are needed to estimate the states. One of those would be NOx levels which are regulated by European law. There are conventional sensors on the market that can measure NOx but these are too slow for in-cycle feedback control. The purpose of this thesis was to derive a model to estimate NOx where the engine very well could have a built in EGR function. The model seems promising, however additional tuning and modification is needed for it to be fully useful in practice. The model presented in this thesis is a zero-dimensional two-zone model. The NOx model assumes that combustion locally occurs at stoichiometric conditions. Model validation is done against single-cylinder engine NOx output data received from the Royal Institute of Technology (KTH). Least-squares fitting methods are also used to simplify calculations considerably. The results indicate that the model is applicable in practice.