“International Multidimensional Engine Modeling User’s Group Meeting 2010” The Detroit Downtown Courtyard by Marriott Hotel, Detroit, MI (USA), April 11 th , 2010 Multidimensional parallel simulation of diesel exhaust aftertreatment systems G. Montenegro, F. Piscaglia, A. Montorfano, A. Onorati Dipartimento di Energia, Politecnico di Milano, via Lambruschini 4, 20156 Milano (Italy) A comprehensive methodology for efficient full-scale simulation of diesel exhaust aftertreatment systems is presented in this work. Specific algorithms and new numerical solvers were developed to favor easy and efficient mesh generation of DPFs, in order to reduce the computational time without affecting the quality of the results. A new multidimensional parallel FV solver for compressible and reacting flows through thin porous medium layers has been developed in the OpenFOAM R ⃝ technology for the full scale simulation of the hydrodynamics, of the transport and deposition of the soot during the filter loading phase. The proposed techniques were implemented into the Lib-ICE code, which is a set of applications and libraries for multi-dimensional engine modeling based on the OpenFOAM R ⃝ technology. In addition the code has been enhanced to be applied to the simulation of catalytic devices. In particular, the developed libraries have been used to model a NOx abatement system based on the SCR technology, which is usually composed by a urea injector, an hydrolysis + SCR catalyst and an oxidation catalyst. The model considers surface chemistry applied to a fluid region treated with particular flow resistance and mass transport properties. The code validation was performed resorting to experimental data available in the literature. INTRODUCTION In the field of internal combustion engines for automo- tive applications, a particular challenging task is the de- sign of aftertreatment devices, since they must guarantee high conversion efficiency and reliability for the whole en- gine operating range, without affecting the overall vehicle performances due to the energy losses that necessarily oc- cur. The use of detailed physical and chemical models has become a fundamental pre-requisite for a realistic simu- lation of the design of aftertreatment devices; they must guarantee high conversion efficiency and reliability in the whole engine operating range, with limited reduction of engine performance due to the energy losses that neces- sarily occur. Exhaust aftertreatment system operation is determined by complex hydrodynamics: in particular, flow conditions at the inlet section of the devices should be as uniform as possible, in order to avoid high temperature gradients that may lead to the crack in ceramic substrate in DPFs or to low conversion efficiencies in SCRs. Ad- vanced numerical solvers able to work with reduced grid dependency are required to describe the transition of com- pressible flows from the turbulent to the laminar regime, as well as to predict the flow field in devices where porous media may be present. Detailed full scale models are very demanding in terms of computational time. Fine grids are required to predict the complex hydrodynamics, the use of detailed chemistry involves ODE stiff solvers to integrate the species and energy equations in each computational cell to obtain the chemical source terms. Also the mesh gen- eration and the case setup are very complex. A set of ap- plications, solvers and utilities for the simulation of diesel exhaust aftertreatment devices were embedded by the au- thors into Lib-ICE [1], a set of libraries for ICE simula- tion developed in the OpenFOAM R ⃝ technology. Lib-ICE also includes models for silencer simulation, for coupling of the OpenFOAM R ⃝ CFD code with one-dimensional codes for engine simulation, spray and combustion models for diesel engines and supports moving meshes with topologi- cal changes [2]. In this work, a short overview of the appli- cations, tools and libraries for engine aftertreatment sim- ulation available in the Lib-ICE is given. DIESEL PARTICULATE FILTERS The purpose of CFD modeling of Diesel Particulate Fil- ters is to simulate the gas flow field into the filter and into the inlet and outlet cones, for the prediction of the loading and regeneration phase. Full scale simulation of particulate traps by CFD software is a challenging problem, because it involves the simulation of compressible flows through porous media in complex domains. If non-simplified ap- proach are used, computational costs are very high. A pop- ular solution to perform full-scale DPF simulations consists of model axial flow fields in the inlet and outlet channels by anisotropic porosity (defined over the cell volume) in- cluded in additional momentum sources that must be cor- rectly set. The local pressure differential across the wall, which drives the wall filtration mass flux, is determined by the pressure difference between corresponding finite vol- ume cells in the inlet and outlet sub-domains. The use of volume sink term to define anisotropic porosity represents a very common approach for the macroscopic simulation of flows through porous media [3; 4]; on the other hand, as shown in [5], this approach may fail to converge when very low porosity of the medium is set, as often in Diesel Particulate Filter simulation occurs. In this section, a solver for compressible reacting flows