Intake and in-cylinder flowfield modelling of a four-valve diesel engine

Abstract

A three-dimensional unsteady turbulent compressible Navier-Stokes solver, KIVA3V, was utilized in the present study to investigate the intake and in-cylinder flowfield of a four-valve direct injection compression ignition engine. Successful modelling of internal combustion engine configurations is highly dependent upon the generation of a quality grid with the correct boundary conditions. The preprocessor of the KIVA3V computer code, K3PREP, was improved, and a complete grid for a four-valve/cylinder single-cylinder caterpillar diesel test engine, CAT3401, was generated. The complete grid consisted of four moving valves, two intake ports, two exhaust ports, and the port runners. Predicted global in-cylinder flow quantities were compared against experimental data. It was found that the intake process was well modelled by KIVA3V with this complete grid. It was also found that important complex flow structures are developed during the intake stroke. While many of these structures decay during the compression stroke, swirl and tumble can survive. The effect of increased swirl ratio at the end of the compression stroke for the CAT3401 engine with a piston bowl is clearly observed in this study. This is important for aiding in good fuel spray atomization. The formation, development, and break-up of tumble flow are seen, contributing to an increase in turbulent kinetic energy at the end of the compression stroke. Other researchers have substantiated this phenomenon for this type of engine flow. The complete engine flowfield, i.e. the inlet jet, pressure variation in the intake runner and ports, and formation of swirl in the intake ports, is also clearly shown in the prediction. The homogeneity of the in-cylinder flow characteristics and temperature field is also studied. Results of these simulations aid in the improved understanding of the intake process and its influence on direct injection compression ignition engine flowfields.