The simulation model of porous media for rotary filter of diesel particulate filter was built and the velocity field and its influencing factors of gasparticulate twophase flow inside filter were analyzed. The influences of exhaust velocity, diameter ratio and divergence angle on internal flow uniformity and turbulent flow loss were analyzed and the optimized criterion was put forward. The research results indicate that the uniformity of internal flow field improves and its structure still keeps unchanged when the inlet velocity of filter increases from 20 m/s to 90 m/s. When the diameter ratio increases from 4 to 6, the surface flow uniformity of filter gets worse and its utilization rate becomes lower. The distribution of internal flow keeps the same when the diameter ratio is beyond a certain value. When the divergence angle increases from 60 degree to 120 degree, the vortex is easier to produce inside the divergent tube and first happens in the relative axial position of 0.8. The vortex intensity and range increase with the increase of divergence angle. In order to reduce backflow and enhance uniformity of flow field, the divergence angle should decrease.
