Large Eddy Simulations of Jet / Tumble Interaction in a GDI Model Engine Flow

Fluid dynamics are essential mechanisms in the performance of internal combustion engines. This work proposes a study of the interaction between a direct injection jet and surrounding tumbling motion in a model Gasoline Direct Injection (GDI) engine chamber using single phase Large Eddy Simulation (LES). Simulations have been performed with the AVBP code which has a “cell-vertex” discretization associated with a Two-step Taylor Galerkin (TTGC) scheme and a Wall Adapting Local Eddy viscosity model. In order to explore the suitability of the 3D LES to simulate the internal flow, the calculation is performed for an idealistic tumbling flow at constant volume. An experimental set up has been designed and measurements are used to initiate and to validate calculations. A gaseous jet representative of the momentum of the real multiphase GDI engine is directly injected in a square chamber. Several initial conditions using Proper Orthogonal Decomposition (POD) analysis are used in order to estimate cycle to cycle variability and two injection strategies are discussed: firstly, a straight jet that competes with tumble; secondly, an inclined jet that adds momentum to the tumbling motion. Satisfactory evolution of the numerical results compared with experiments is found. 3D calculations show that the injection strongly modifies the initial rotating structure. The vorticity tube of this initial tumbling flow is deformed in the injection direction. LES results are compared to PIV measurements. This provides a deeper understanding of the 3D flow transition. Cycle-to-cycle variations are demonstrated to be of primary importance.