CFD Analysis of the pre-mixed combustion of a Hydrogen and Methane mixture in a Rapid Compression Expansion Machine

Nowadays the use of fossil fuels for environmentally purpose is being limited. This is especially true for what concern the transportation field: indeed, the necessity for another energy source or carrier arises. One possible solution it’s related with the use of Hydrogen. This can be used both for in-situ electricity generation by means of fuel cells and for mechanical power generation by means of Internal Combustion Engines (ICEs). Hydrogen can be quite interesting for Combustion in ICEs due to its Lower Heating Value (LHV) to stoichiometric Air to Fuel ratio which is higher than that of other fuels like Gasoline or Diesel, and this could lead to an efficiency in combustion processes. Moreover, it will be possible to use for focused applications the already existing and highly developed technology of ICEs. In addition, with Hydrogen, it will be possible to develop combustion processes particularly “Lean” in terms of fuel usage, this thanks to its larger flammability limits and higher burning velocity, compared with other traditional fuels. However, the use of pure Hydrogen in ICEs it’s still held by some drawbacks like the higher Temperature and Pressure obtained if compared with combustion of traditional fuels, the relevant amount of NOx products during the process, and the risk of unwanted ignitions. A possible approach for trying to limit those negative aspect could be the use of Hydrogen blended with another fuel which is more “stable” like Methane. Therefore, the combustion of Hydrogen blended with Methane in different proportions it’s studied using a Rapid Compression/Expansion Machine (RCEM), then some set of experimental results for stoichiometric and lean combustions are obtained. Using the experimental results, it will be developed a Computational Fluid Dynamic Model of the combustion in the combustion chamber of the RCEM. This will be done by using AVL Fire M and AVL Fire Workflow Manager. Two different approaches will be developed: one using the Extended Coherent Flame Model (ECFM) and another one based on the study of the chemical reactions which develop during the combustion process. Special care will be given to the creation of combustion chamber’s mesh and setting of initial conditions (I.C.) and boundary conditions (B.C.). This will be fundamental for a good accuracy of the results. At the end the numerical results obtained with CFD will be analyzed and compared with experimental results obtained from RCEM.