| Summary: | Intake port structure directly affects the flow characteristics and combustion process of diesel engine, and then affects the comprehensive performance of diesel engine. To the intake ports of a four-valve direct injection diesel engine, the flow characteristics are analyzed on the four combined intake ports : (1) helical (left) and tangential (right), (2) tangential (left) and helical (right); (3) helical (left) and helical (right); and (4) tangential (left) and tangential (right).And the influence of air flow in four combined intake ports to in-cylinder gas flow is also analyzed. Results show that the helical and tangential combination intake ports flow velocity increases with the valve lift increases, and small turbulence arises at the valve guide lug, and the intake flow velocity of the minimum cross-section of the junction of the guiding section and the helical section is the maximum. The air flow in- cylinder moves from top cylinder head bottom to the cylinder bottom, the air flow is enlarged gradually by the small-scale irregular swirl, which eventually converges to a single swirl. The turbulence kinetic energy is very big when the air is just entering the cylinder, the flow space expands rapidly, and the dissipation of turbulent kinetic energy is very significant with the gas moves to the bottom of the cylinder.
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