Large-eddy simulation of in-cylinder flow in a DISI engine with charge motion control valve: Proper orthogonal decomposition analysis and cyclic variation

The application of the charge motion control valve is an effective and flexible way to reduce cycle-to-cycle variations (CCV) and improve engine performance. The objective of this research is to investigate the influence of the tumble flap (i.e., a specific type of charge motion control valve) placed in the intake port on the in-cylinder aerodynamics and CCV inside a non-reacting, direct injection spark ignition (DISI) engine by means of multi-cycle large-eddy simulation (LES) and proper orthogonal decomposition (POD). Extensive POD analyses involving the phase-dependent POD and phase-invariant POD were carried out. Furthermore, the POD quadrapole decomposition method was employed to gain more insight into the stochastic nature of in-cylinder flow. Results indicate that the tumble flap greatly affects the in-cylinder flow field and the first three subfields, but its effect on turbulent part is insignificant. With the closed tumble flap, more intense tumble motion, improved volumetric efficiency, increased energy portion of the mean part, decreased rate of energy decay, and reduced CCV could be achieved compared with the open tumble flap. It is also found that the phase-invariant POD is a useful tool to assess the effect of the tumble flap on the evolution characteristics.