Effects of Combination and Orientation of Intake Ports on Swirl Motion in Four-Valve DI Diesel Engines

Two identical helical ports and two identical directed ports were arranged into four different kinds of port combinations: helical and helical, helical and directed, directed and directed, directed and helical. Each port can rotate freely around its valve axis. The swirl ratio and the flow coefficient for each combination of intake ports were tested on a steady flow rig when both ports were positioned in different orientations around its valve axis. Two parameters, the loss rate of mean flow coefficient and the loss rate of angular momentum, were defined to describe the degree of interference between the flows discharging from the two adjacent intake valves. Velocity distribution in the vicinity and circumference of the intake valves was measured using Hot Wire Anemometer to further study the intake flow interference for different port combinations. Experimental results show that when the directed intake port is positioned upstream, the flow jetting from the directed port interferes greatly to the intake flow discharging from the front port. The magnitude of swirl ratio and the degree of the flow interference depend intensively on the orientation of the directed port. As the directed port is situated in the tangential position toward the cylinder axis, swirl ratio becomes higher and the intake flow interference becomes less. When the helical intake port is positioned upstream, the swirl ratio has a smaller sensitivity to the orientation of the helical port and the degree of intake flow interaction between two valves becomes less. Higher swirl ratio can be obtained when the two ports are positioned in roughly perpendicular direction to each other.