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An advanced multi-domain CFD analysis approach is proposed to calculate the scavenging flow process in motored two-stroke engines. An implicit and conservative treatment at the domain interface is developed which offers significant speedup in convergence. An arbitrary Lagrangian-Eulerian approach for moving grid and a grid remeshing technique for grid sliding at engine cylinder/transfer ports interfaces are used for efficiency and accuracy. A three-dimensional simulation of the Mercury Marine research two-stroke engine is carried out to demonstrate the approach. Six computational domains are used which naturally represent the geometries of the cylinder, engine dome, exhaust and transfer ports. The influence of boost port inclination angle on the scavenging process of the two-stroke engine is also studied numerically. The computation is supplemented with a standard two-equation turbulence model with compressibility correction.

The paper presents three-dimensional simulations of the in-cylinder processes in Direct Injection (DI) Diesel Engines. First, mathematical formulation is described with emphasis on physical models used for turbulence, interphase friction, evaporation and chemical reaction. Then, the results of 3D transient calculations of the two-phase fuel-air mixing and evaporation processes are presented. Four test cases have been considered to demonstrate the effects of changes in: a) fuel injector, b) computational grid, and c) initial air swirl velocity. Computed results show that each of these parameters has significant effect on the spread and evaporation of liquid fuel spray. The results of low and high air swirl cases are in qualitative agreement with published experimental observations. Finally, a test calculation of 3D, two-phase flow with evaporation and combustion is presented for demonstration purposes.