To straighten a fluid which flows into a passage from a turbulent condition into a laminar flow condition, promote separation of the fluid in the vicinity of a wall surface, reduce frictional resistance and Reynolds stress, and improve a filling efficiency and an exhaust efficiency by forming a rough surface on a wall surface of an intake passage or an exhaust passage in an internal combustion engine.
In an engine 1, a laminar condition combustion is carried out at the time of a compression lean operating mode so as to improve a fuel consumption ratio. Namely, fuel is injected from a fuel injection valve 9 toward an ignition plug 10 at the time of a compression stroke, rich mixture is generated in the vicinity of the ignition plug 10, lean mixture is generated around the rich mixture, and then laminar mixture is generated. Inner walls of an intake port 5 and an exhaust port 6 in parts arranged adjacent to a combustion chamber 2 formed on a rough surface 13 by regularly arranging, for example, a recessed/projection part (a riblet). Accordingly, it is promoted that a fluid made of intake and exhaust which flows into each port 5, 6 is separated from the wall surface, and thereby, a frictional resistance is reduced. Also, it is promoted that the fluid which flows into each port 5, 6 is laminated.
FUKUSHIMA DAIGOROU
ARITA AKIRA
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