The effect of intake valve alignment on swirl generation in a DI diesel engine

Abstract Two different geometries of the intake valves on the cylinder head of a four-valve large-bore diesel engine were compared in terms of their swirl generation mechanisms in the cylinder during the intake process. The swirl generation level and flow resistance were measured using a swirl meter on a steady flow rig and the detailed intake flow structure was studied using LDV measurements of the in-cylinder bulk flow velocity and turbulence intensity. The effects of changes in the maximum valve lift were also studied for each type of valve arrangement. Methods for calculating the swirl moment from the LDV data are presented and discussed by comparing with the swirl meter results. It was found that the aligned valve port arrangement (valves located at equal distances from the symmetry axis) generates higher swirl due to its eccentricity with respect to the intake port. In an inclined valve port engine (valves at different distances from the symmetry axis), increasing the maximum valve lift was found to improve the swirl generation capability significantly, even though it generated less swirl overall due to swirl cancellation at low valve lifts.

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