Effects of porting arrangements on intake swirl and scavenging performance were investigated numerically.A three-dimensional transient numerical model was established for the in-cylinder processes.Intake swirl was introduced by changing port tangential inclinations and scavenging performance was evaluated by normalized carbon dioxide mass fraction.The intake swirl intensity and scavenging performance with different porting arrangements were compared.The results show: (1) Rotation flow including swirl can be generated by port tangential inclination arrangements

and the swirl approximates to solid-body swirl approaching the top dead center.(2) Intake swirl results in short-circuiting during the scavenge processes and a concentrated carbon dioxide central core.(3) The short-circuiting can be reduced by increasing the axial inclination of inlet ports or extending the distance between inlet and exhaust ports in the flow direction.Swirl intensity can be decreased by reducing scavenge port tangential inclinations

leading to increase of short-circuiting.