Numerical Optimization of Flow Uniformity inside Diesel Particular Filters

A uniform flow inside a Diesel Particular Filter (DPF) is very critical to ensure the desired performance and durability of the filter system. In current paper, a systematically study was performed to investigate the geometrical effects on flow uniformity in the front of diesel particular filter by using Computational Fluid Dynamics (CFD) tool. The studies were focused on the effects of spiral rib inside inlet tube; inlet and outlet cones, length and angle of inlet cone. In all the numerical simulations, mesh sizes were carefully controlled to yield accurate and consistent results. No improvement on flow uniformity index was observed by adding a signal spiral rib in the inlet tube in front of diffuser (inlet cone), and even worse in the case with a single deeper rib. On the contrary, pressure loss increases rapidly. Increasing the number of ribs, flow uniformity index could be improved and pressure loss is still higher than that of without spiral ribs, but much lower comparing with single rib geometry. Evidence shows experimental results could over predict flow uniformity index by as much as 7%. Comparing with outlet cone, inlet cone was found to have much larger effect on flow uniformity index. For a longer inlet cone, 0 degree cone angle (straight cone) was shown the best flow uniformity index and the flow uniformity index is reduced from 0.93 to 0.91 as inlet cone angle increases from 0 to 60 degrees. As the length of inlet cone reduced, the optimal inlet cone angle for the best uniformity index will increase. With a combination of inlet cone (with certain angle of attack and outlet cone (with certain angle of attack and orientation) the maximum flow uniformity index can be achieved.