Combustion processes are reacting flows characterised by a complex interplay of flow, chemical reaction and molecular transport. They can be modelled numerically by solving the underlying conservation equations for mass, momentum, energy and species masses (system of partial differential equations). The modelling of technical combustion systems is hampered by the fact that the typical time, length and velocity scales differ by several orders of magnitude (time scales of chemical reactions in the nanosecond to the second range, thickness of flame fronts less than 1 mm, system dimensions can be several metres, etc). Direct numerical simulations of technical systems while resolving the smallest scales are, therefore, impossible even with the fastest mainframe computers available. That is why hierarchical modelling approaches are used, in which the results of the simulation of detailed systems (e.g. of vortices that interact with flame fronts) are used purposefully to develop models for the simulation of technical systems. ITT’s projects encompass, therefore, the entire range of numerical simulation, from detailed simulations to the modelling of technical combustion systems.