Flow decomposition methods applied to the flow in an IC engine manifold

Large Eddy Simulation (LES) of the flow and mixing in an engine manifold of a six cylinder Diesel engine is carried out. Proper Orthogonal Decomposition (POD) and Dynamical Mode Decomposition (DMD) are applied to sets of LES data from these computations. The engine manifold under consideration includes a pipe-junction used for Exhaust Gas Recirculation (EGR). The methods of analysis, POD and DMD, are applied to the velocity field and the exhaust concentration field. It is found that POD facilitates the analysis of the pulsating, complex and turbulent flow field as compared to instantaneous fields. The flow field is dominated by the EGR pulses and their interaction with other pulses originating from the cylinder valves. The maldistribution of EGR concentration among the first cylinder ports can clearly be linked to the EGR pulsations. DMD is able to extract flow structures at certain frequencies. Using these properties of DMD, the motion of the EGR pulses can be extracted and visualized. The combination of LES and flow decomposition is found to give a rational for the interpretation of the flow phenomena, which might facilitate the optimization of engine manifolds in terms of EGR non-uniformity.