Simulation of diesel particulate filters in large exhaust systems

The transmission loss of silencer systems that incorporate diesel particulate filters (DPF) was predicted using numerical simulation. The model developed by Allam and Åbom, which assumes plane wave propagation, was used to describe the DPF. However, three-dimensional wave propagation was permitted in the airspace upstream and downstream to the DPF. The modeling approach was validated experimentally for a case in which the plane wave cutoff frequency was exceeded in the airspaces upstream and downstream with good agreement. The assumption of plane wave behavior in the DPF was confirmed by modeling 81-cells of a DPF using an acoustic finite element model. The finite element analysis demonstrated that plane wave propagation could be assumed in the DPF regardless of the diameter of the DPF provided that the cross-sectional dimension of a cell is much smaller than an acoustic wavelength.