Search Results

Computational fluid dynamic (CFD) analysis of in-cylinder events in the automotive industry is heavily dependent on spray simulations for almost all advanced engine concepts. As the upper bound of efficiency in these engines is pursued, the accurate prediction of sprays is critical, since the mixture preparation and ignition, whether by spark or auto-ignition, needs to be precisely controlled. While most of the spray literature closely examines various drop processes, especially breakup, comparatively less attention has been focused on the momentum coupling between the liquid and the gas phases, in particular the numerical aspects. In fact, adjusting models for the evolution of drop size has been one of the dominant means of controlling predictions of spray shape and liquid penetration.

Results of three-dimensional steady flow calculations are compared with existing pressure and velocity-measurements of two manifold-type junctions. The junctions consist of a main duct and a side branch, both with the same rectangular cross section, with the side branch joining the main duct at an angle of either 90 or 45 degrees. Both combining and dividing flow configurations are considered for different total mass flow rates and different side-branch-to-main-duct mass flow ratios. One objective of this investigation was to assess the effects of numerical differencing scheme and mesh refinement on solution accuracy, and both parameters showed strong influences on the computed results. It is shown that calculations should be made with the highest possible level of numerical accuracy and grid resolution in regions of flow recirculation. Comparisons of computed and measured velocities, static pressures, and flow loss coefficients are presented in this paper.

Results of three-dimensional coupled intake port and in-cylinder flow calculations, including moving valves, are reported. These computations have been performed using a recently developed unstructured-mesh flow code; moving valves are accommodated via a new algorithm for arbitrary three-dimensional mesh deformation in response to moving boundaries. The geometry is intended to simulate a generic four-valve head with two intake ports. Computations are started at intake valve opening and are carried through top-dead-center of compression. A standard k - ϵ model is used to represent turbulent transport of momentum. Of principal interest is the evolution of and interaction between the large-scale induction-generated mean flow structure and turbulence. In particular, we seek to understand the role of swirl and tumble in generating near top-dead-center turbulence.