SCR modelling for road transport applications: realization, validation and implementation on light-duty vehicle

Vehicle modelling is a standard procedure employed today by all the major OEMs in order to comply with the market requirements as well as with the several industrial norms, aiming at reducing the number of modifications during the design phase. For these reasons, its implementation on tools such as Simulink® is of fundamental relevance and constitutes the so-called virtual prototyping process. The aim of this thesis is to examine the longitudinal behaviour and optimize the emissions treatment of a vehicle already present on the market, a 2014 remarkable van. In particular, the attention was shifted on the NOx emissions, being the most relevant emission, together with the particulate matter, in Diesel engines such as the one employed on this van. The whole vehicle layout was implemented on a specific Simulink® tool, commercially known as Simscape™ and able to create an apparatus based on physical relationships, where each single block performs the functions of a specific element of the real van. Particular attention was put on the engine mock-up, realised through the GT-Power® software and governed by a BMEP-target principle, according to the required engine speed and accelerator pedal position. Successively, the engine interface was coupled to the Simulink net through a dedicated interface, ensuring the management of the entire system directly on Simulink®. After the selection of a Selective Catalyst Reduction (SCR) suitable to the engine characteristics, the trivial chance to customize a component ex novo was exploited. This constitutes a new methodology practicable through a thorough understanding of the source codes and of the mathematical principles governing the components. Finally, a validation procedure was conducted on the SCR thermal evolution according to the experimental data provided. The complete simulation, performed on the current standard homologation cycle, the Worldwide harmonized Light-duty vehicles Test Cycle (WLTC), has demonstrated the ability of the model to correctly replicate the vehicle dynamics. This was achieved according to a continuous reference and model speed matching principle that brought the margin of error below 1 km/h for more than 80% of the time. Moreover, the BMEP target-based approach was tested on a 0-100 km/h launch, where the computed time error, related to the empirical data, was found to be less than 2%. In addition, the investigation has revealed that the conversion efficiency of the selected 12 litres catalyst achieves values higher than 90% in general, when the residence time and SCR Temperature are high enough. These results confirms the pivotality of the adoption of the methodology to reasonably simulate the vehicle behaviour in advance. Consequently, the best possible NOx emission level can be reached, according to the current State of Art. Overall, the procedure leads to a higher level of detail while still maintaining the design costs low. In this analysis, the focus was limited to the mechanical and thermal behaviour of the main elements of a van. Nevertheless, this approach can be extended to characterize all the properties of any device installed onboard, opening infinite scenarios in the future vehicle modelling.