A 1D Unsteady Thermo-Fluid Dynamic Approach for the Simulation of the Hydrodynamics of Diesel Particulate Filters

摘要

A new approach for the fluid-dynamic simulation of the Diesel Particulate Filters (DPF) has been developed. A mathematical model has been formulated as a system of nonlinear partial differential equations describing the conservation of mass, momentum and energy for unsteady, compressible and reacting flows, in order to predict the hydrodynamic characteristics of the DPF and to study the soot deposition mechanism. In particular, the mass conservation equations have been solved for each chemical component considered, and the advection of information concerning the chemical composition of the gas has been figured out for each computational mesh. A sub-model for the prediction of the soot cake formation has been developed and predictions of soot deposition profiles have been calculated for different loading conditions. The results of the simulations, namely the calculated pressure drop, have been compared with the experimental data. At first, a validation with the experiments under steady state flow conditions for clean filters, as well as for loaded filters, has been performed and the calculated velocity profiles of the gas inside the filter channels have been compared to those calculated by a CFD model. Finally, a comparison with the experiments on a 1.9L JTD Fiat turbocharged diesel engine equipped with a DPF has been considered: simulations of the engine coupled with the whole exhaust system have been carried out, in order to investigate on the capability of the developed code to give good predictions even under unsteady flow conditions.