Abstract:
This document outlines the development and progress of the KIVA-4 computational fluid dynamics (CFD) code, a tool used for simulating in-cylinder processes in high-efficiency engines. The research focuses on several key areas to enhance the code's applicability and performance, particularly in relation to complex hydrodynamic processes. A major effort was the parallelization of KIVA-4 to handle realistic engine geometries, like a 4-valve pentroof and a 3-valve engine, with increased efficiency. The report notes that while speed-up was achieved, the performance plateaus with a higher number of processors due to the mesh size and partitioning challenges when cells become deactivated as the piston moves. To address this, a repartitioning capability was developed. The work also includes the creation of a collocated version of KIVA-4, which is more suitable for unstructured meshes containing tetrahedra and prisms, a mesh strategy expected to be used in future simulations. This collocated version also enabled the use of a grid overset method, which is a significant hydrodynamic advancement. This method allows for the use of two different meshes simultaneously, one specifically for the fine-resolution modeling of the liquid fuel spray and another for the broader engine geometry. This reduces the spray dependence on the grid and improves the accuracy of the spray dynamics. The researchers also implemented advanced combustion and spray models from the University of Wisconsin and interfaced with Reaction Design's chemistry package. To make the code more accessible, they developed converters for established mesh generation software like TrueGrid and ICEM. The ultimate goal of this work is to make KIVA-4 a more robust and widely adopted tool for advanced combustion engine research by providing enhanced capabilities for simulating complex in-cylinder fluid dynamics.
