Shape Optimization of Automotive Exhaust Systems with Continuous Adjoint Flow Solvers

for Picof 2012 "Shape optimization in industry" Ecole Polytechnique, Paris, France, April 2-4, 2012 SHAPE OPTIMIZATION OF AUTOMOTIVE EXHAUST SYSTEMS WITH CONTINUOUS ADJOINT FLOW SOLVERS C. Hinterberger, M. Olesen Faurecia Emissions Control Technologies, Germany GmbH [email protected] [email protected] ABSTRACT Meeting backpressure and flow uniformity requirements within severe packaging constraints presents a particular challenge in the layout of catalyst inlet cones. A continuous adjoint geometry optimization tool (CAGO), has been developed at Faurecia Emissions Control Technologies [1, 2], which finds suitable shapes for catalyst inlet cones directly from the package space. The tool is based on the continuous adjoint formulation derived and implemented by C. Othmer et al. [3, 4] and it is implemented within the open source CFD toolbox OpenFOAM®.Meeting backpressure and flow uniformity requirements within severe packaging constraints presents a particular challenge in the layout of catalyst inlet cones. A continuous adjoint geometry optimization tool (CAGO), has been developed at Faurecia Emissions Control Technologies [1, 2], which finds suitable shapes for catalyst inlet cones directly from the package space. The tool is based on the continuous adjoint formulation derived and implemented by C. Othmer et al. [3, 4] and it is implemented within the open source CFD toolbox OpenFOAM®. Figure 1: Workflow of design and optimization process As shown in figure 1, CAGO starts from the provided package space and produces a design proposal, which is used as a reference surface (imported as IGES) in the CAD process. Subsequently, the CAD design is validated in a fully compressible flow analysis, where the catalysts are modelled as anisotropic porosities. For further optimization of flow uniformity and pressure drop, surface sensitivities are computed by solving the adjoint flow fields with a frozen density and frozen viscosity assumption. For systems equipped with a fuel vaporizer, which injects some additional fuel into the exhaust system for DPF (diesel particulate filter) regeneration, surface sensitivities for the uniformity of the fuel vapour distribution in front of a DOC (diesel oxidation catalyst) can be also calculated. The resulting surface sensitivities can be used to define manufacturing tolerances or assess the effect of geometry modifications. In the current optimization workflow, these modifications are either applied manually in the CAD model or the CFD surface mesh can be morphed directly. The CFD optimization workflow will be presented together with various optimization examples. C. Hinterberger, M. Olesen 2 Figure 2: Overview of continuous adjoint geometry optimization tool CAGO