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The purpose of this paper is to investigate the mixture formation and optimize the operating conditions under cold start in a stoichiometric (λ=1) GDI engine with wall-guided piston using a 3D commercial code, STAR-CD [8]. For GDI engine under cold start, it can be difficult to carry out the optimization of operating conditions by engine test alone without the understanding of mixture formation inside the combustion chamber. In this study, three cold start conditions of the catalyst heating mode with split injection, the cranking under freezing temperature and acceleration before engine warm-up which causes oil dilution were calculated. In particular, injection strategy for each cold start condition were optimized and compared to the engine test data. The previously validated spray models [6] were applied to the analysis of the spray formation and mixing process inside the combustion chamber.

A new numerical method is developed to predict the movement of a valve induced by the flow-induced force and pressure field around a valve. It solves the governing equations of fluid dynamics coupled with the motion equation of the valve. We apply this method to predict the motion of a spool valve in a valve body of an automatic transmission. In addition, the effectiveness of design parameters is found to achieve the design goal that reduce the discharge flow rate and flow-induced force. Finally, the optimized design of valve with better performance is suggested.

Development of TDOS (Torque converter Design Optimization System), an integrated design process, is presented. The main functional groups of TDOS are torque converter geometry designer, 3D CFD analysis module, and design optimizer. For the geometry design, an in-house code BPG (Blade Profile Generator), is employed to create the 2D torus and 3D blade coordinates with given design constraints. To obtain an accurate performance results, an automated CFD analysis module is created which includes 3D geometry modeling, mesh generation, solving and result analysis. All CFD parameters that affect the accuracy of solution such as mesh size, simulation scheme and boundary conditions are predefined for the automated CFD analysis. The optimal parameters for CFD analysis are determined from the previous study of mass-produced torque converters. Having automated the geometry design and CFD analysis process, an optimization procedure of torque converter geometry is developed.