Abstract: A straight port and a swirl port supply low-oxygen-concentration gas and high-oxygen-concentration gas into a combustion chamber of an engine such that high-level-oxygen-concentration gas and low-level-oxygen-concentration gas are formed from the high-oxygen-concentration gas and the low-oxygen-concentration gas in an adjacent region of the combustion chamber, which is adjacent to a fuel mist injected from an injection hole of a fuel injection valve. The high-level-oxygen-concentration gas is located in a corresponding area of the adjacent region, which is generally opposite from the fuel injection hole, and the low-level-oxygen-concentration gas is located in a remaining area of the adjacent region, which is other than the corresponding area of the adjacent region.

Abstract: A straight port and a swirl port supply low-oxygen-concentration gas and high-oxygen-concentration gas into a combustion chamber of an engine such that high-level-oxygen-concentration gas and low-level-oxygen-concentration gas are formed from the high-oxygen-concentration gas and the low-oxygen-concentration gas in an adjacent region of the combustion chamber, which is adjacent to a fuel mist injected from an injection hole of a fuel injection valve. The high-level-oxygen-concentration gas is located in a corresponding area of the adjacent region, which is generally opposite from the fuel injection hole, and the low-level-oxygen-concentration gas is located in a remaining area of the adjacent region, which is other than the corresponding area of the adjacent region.

Abstract: A combustion system of an internal combustion engine has a fuel injector injecting a fuel directly into a combustion chamber and a water injector injecting a water (non-combustible fluid) into the combustion chamber. The water collides with a fuel spray which the fuel injector injects. A penetrating force of the fuel spray is decreased and the fuel spray hardly reaches a cylinder wall surface. The injected fuel is combusted at a position away from the cylinder wall surface, so that the combustion heat transferred to the cylinder wall surface is reduced and the heat loss of the combustion can be decreased.