Numerical analysis of gas flows during intake stroke in the cylinders of reciprocating engines

SUMMARY Numerical Analysis of Gas Flows During Intake Stroke in the Cylinders of Reciprocating Engines The nature of the various events in reciprocating internal combustion engines are very complicated. Many physical processes occur and act on each other in their complex geometries. Among these processes, the flow in the cylinders play an important role on generation of turbulence, fuel-air mixing and combustion, thus exerts great influence on engine performance through these processes. At the present time, engine designers try to improve the thermal efficiency and to reduce the undesirable exhaust emissions using sophisticated devices for the flow control. These design efforts require the prediction of flow in multi dimensions, but experimental techniques based on trial and error methods are time consuming and expensive to perform, and moreover information obtained from them is very limited. Therefore, the designers have began to set greater hopes on numerical methods to predict what happens in the engine cylinder, especially at the early stage of design. So, recently there has been an increasing trend to apply multidimensional models for computing fluid motion in internal combustion engines. However, so far, few detailed comparisons of the predictions with the experiments have been done. The objective of this study is to perform a two-dimensional numerical analysis of the flow during intake stroke in the cylinders of a reciprocating engines. For this reason, a computer code developed which employs fc-e turbulence model and the "law of the wall" boundary conditions. Numerical solution method of the governing equations is based on the SIMPLE technique of Patankar with the "finite control volume" approach. Comparisons of the velocity and turbulent intensity field have been made with that prediction by Gosman et al. and measurements by Morse. The results of computations were generally encouraging. However, discrepancies were observed which are attributed to either or both unknown boundary conditions or shortcomings in the k-z model used. Key Words: Flow in the rciprocating engines, k~e turbulence model, Finite control volume method, Hybrid (central/upwind) discretisation scheme. vn