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Flow and flame structure visualization and modeling were performed to clarify the characteristics of bulk flow, turbulence and mixing in a four-valve engine to adopt the lean combustion concept named “Barrel-Stratification” to the larger displacement center-spark four-valve engine. It was found that the partitions provided in the intake port and the tumble-control piston with a curved-top configuration were effective to enhance the lean combustion of such an engine. By these methods, the fuel distribution in the intake port and the in-cylinder bulk flow structure are optimized, so that the relatively rich mixture zone is arranged around the spark plug. The tumble-control piston also contributes to optimize the flow field structure after the distortion of tumble and to enable stable lean combustion.

To support sustained manned activities in an enclosed environment in space vehicles such as the Space Station (SS), a respirable air supply system is essential and optimization should be aimed at in the design of such a system. For cabin air revitalization, it is indispensable to remove carbon dioxide (CO2) and other gaseous contaminants generated from crew and/or non-metalic materials to prevent them from accumulating. In addition to the above functions, oxygen (O2) recovery function using trapped CO2 is indispensable for the Air Revitalization System (ARS) because a reduction of resupply materials from ground is strictly required. This paper presents and an outline of a feasibility study of the ARS in which system optimization is made.