Comparison and Application of Dynamic Mesh Techniques in Nozzle-Flow Simulation

The present work involves the technical background of the field of Diesel injection systems of combustion engines and compares the effects of two kinds of remedies (Re-meshing Technique and Linear Interpolation Technique) on mesh deformation. Mathematical formulation of moving grids has been proposed to guide the change of cell volume before. In this study, CFD (Computational Fluid Dynamics) analysis was conducted to study the behaviors of the internal nozzle flow and the characteristics of the spray. An external library concept was introduced to couple the internal nozzle injection process with the spray formation. In addition, all dynamic simulations were performed under a double-axis system. A comparison between simulation and experimental results shows that the integration of the traditional mesh deformation technique with the re-meshing or the linear interpolation technique can repair mesh deformation and further contribute to better simulation results. In particular, the introduction of the linear interpolation technique produces better effects when the needle moves from an opened state. Moreover, this study solved the technically locked simulation problem, namely that needle opens from the closed state in nozzle-flow simulation, by applying the re-meshing technique. As a result, a more complete numerical model can be suggested and some important flow characteristics have been observed during the opening and closing processes of the needle.