Development and validation of NG-H2 engine numerical model embedding detailed chemistry in Converge

This thesis project is a combustion modelling study and development of a natural gas engine by means the support of a CFD (Computational Fluid Dynamics) software called CONVERGE. The sophisticated software used introduced a new concept of an automatically mesh generation, useful to save time, with a complex code which can also refine the grid locally basing on particular rules. The project supports an European research, named Gas-on, with the specific aim to reduce the engine emissions trough the usage of alternative fuels, such as methane (CH4) and methane with the addition of percentages of hydrogen (H2), in order to reduce the carbon pollutant generated by engines. The thesis project, with the consequential model validation, has been carried out at the CFD company Convergent Science GmbH in Austria and all the experimental data has been provided by the Politecnico di Torino university, especially from the DENERG laboratory of the university itself. The project itself is a model validation of the FIAT FIRE 1.4 16V Turbo CNG engine focusing on the SAGE Detailed Chemistry combustion model by means the usage of specific reactions mechanism that fit perfectly the reactions accomplished by the oxidation of the methane, or methane with the addition of percentage of hydrogen, in air. The thesis can be subdivided in two main parts according with the topic that is being discussed. The first part is a review of all the fluid governing equations, with which the software computes the results of each simulation, and a brief description of how the software and the automatic mesh generation work in order to give some technical information regarding the base concepts on which the software is based on and the user-friendly usage of the CONVERGE interface. In the second part all the results obtained will be shown and described in details with a particular focus on the modifications carried out in order to obtain the model validation. This second part can be also split in two parts where the former is a model validation of two specific engine operating points with the usage of the NG fuel and the latter is a model validation of one of these two operating points with the addition of a 15% of hydrogen in the fuel composition.