The increasing use of passenger vehicles over the past decades has caused an increase in harmful ... more The increasing use of passenger vehicles over the past decades has caused an increase in harmful exhaust gas emissions which give rise to environmental and health problems. This problematic has led governments to establish very stringent emission limits. The emission restrictions require more performing after-treatment systems. Among many other solutions, analysing and optimising the flow impact on the conversion efficiency is an important step towards the solution of the complex engineering problem. Detailed velocity, temperature and concentration distributions are very difficult to measure experimentally. Numerical simulations can provide additional information to understand the interaction of flow distribution and conversion efficiency. The simulation of these systems is computationally very expensive due to complex physical and chemical phenomena occurring simultaneously throughout the system. To overcome this cost, one can resort to some simplified physical and chemical models ...
Industrial & Engineering Chemistry Research, 2019
This work reports an exploratory study in terms of monoliths preparation for application in NO x ... more This work reports an exploratory study in terms of monoliths preparation for application in NO x CH 4-SCR, a promising route for treating the exhaust gas emissions from natural gas vehicles. By using washcoating method and a zeolite precursor, the effects of milling time (1, 2 or 16 h) and zeolite concentration in the slurry (15, 20 or 30 wt.%) on the coating characteristics were evaluated. Then, the optimized washcoating conditions were used in order to obtain two PdCe-HMOR zeolitecoated monoliths with different number of CPSI (400 or 600). Tests were carried out under representative conditions of real exhaust gases from a heavy duty vehicle's engine. Results showed that the differences in the performances of both materials could not be attributed to hydrodynamic factors being thus proposed an explanation related to the catalyst surface area in contact the inlet feed gas, significantly higher for the most active monolith.
This paper aims at finding optimal adaptive mesh refinement strategies to capture vortical struct... more This paper aims at finding optimal adaptive mesh refinement strategies to capture vortical structures. Due to their efficiency, we focus on a-posteriori mesh refinement methods. In particular, we derive a Hessian error estimator for the h-refinement scheme and a residual-based error estimator for finite volume methods and octree grids. The methods are validated for a classical test for the solution of the advection-diffusion-reaction equation and tested against three different test cases where vortical structures are present. In particular we test the temporal evolution of the Lamb-Oseen vortex, the linear growth-rate of small perturbations in a shear viscous layer and the energy evolution in the isotropic turbulence case. The performance of the proposed estimators and the choice of the optimal quantity of interest is discussed for different test cases.
L'utilisation croissante de vehicules au cours des dernieres decennies a cause une augmentati... more L'utilisation croissante de vehicules au cours des dernieres decennies a cause une augmentation dans les emissions de gaz d'echappement nocifs provoquant des problemes de sante et d'environnement. Cette problematique a conduit les gouvernements a mettre en place des limites d'emissions plus strictes. Afin de respecter ces limites, il est necessaire de developper des systemes de post-traitement plus performants. Parmi plusieurs solutions possibles, l'analyse et l'optimisation de l'impact de l'ecoulement sur les reactions chimiques est une approche importante pour resoudre ce probleme complexe. Au point de vue experimental, il est tres difficile de mesurer le champ de vitesse detaille et la distribution de la temperature et de la concentration. Les simulations numeriques peuvent fournir des informations supplementaires pour comprendre l'interaction entre la distribution de l'ecoulement et l'efficacite des reactions. La simulation numerique d...
The flow distribution within the automotive catalytic converter is an important controlling facto... more The flow distribution within the automotive catalytic converter is an important controlling factor on theoverall conversion efficiency. Capturing the flow features minimizing the computational cost is the first important step towards the solution of the complex full engineering problem. In this work we present a novel approach that combines physical and numerical multi-resolution techniques in order to correctly capture the flow features inside an automotive catalytic converter. While Adaptive Mesh Refinement techniques are optimized in order to minimize the computational effort in the divergent region, a novel subgrid model is developed to describe the flow inside the catalytic substrate placed between the convergent and divergent regions. The proposed Adaptive Mesh Refinement methods are tested for two test cases representative of the flow features found in the divergent region of a catalytic converter. The performance of the new subgrid model is validated against the non-uniformi...
The increasing use of passenger vehicles over the past decades has caused an increase in harmful ... more The increasing use of passenger vehicles over the past decades has caused an increase in harmful exhaust gas emissions which give rise to environmental and health problems. This problematic has led governments to establish very stringent emission limits. The emission restrictions require more performing after-treatment systems. Among many other solutions, analysing and optimising the flow impact on the conversion efficiency is an important step towards the solution of the complex engineering problem. Detailed velocity, temperature and concentration distributions are very difficult to measure experimentally. Numerical simulations can provide additional information to understand the interaction of flow distribution and conversion efficiency. The simulation of these systems is computationally very expensive due to complex physical and chemical phenomena occurring simultaneously throughout the system. To overcome this cost, one can resort to some simplified physical and chemical models ...
Industrial & Engineering Chemistry Research, 2019
This work reports an exploratory study in terms of monoliths preparation for application in NO x ... more This work reports an exploratory study in terms of monoliths preparation for application in NO x CH 4-SCR, a promising route for treating the exhaust gas emissions from natural gas vehicles. By using washcoating method and a zeolite precursor, the effects of milling time (1, 2 or 16 h) and zeolite concentration in the slurry (15, 20 or 30 wt.%) on the coating characteristics were evaluated. Then, the optimized washcoating conditions were used in order to obtain two PdCe-HMOR zeolitecoated monoliths with different number of CPSI (400 or 600). Tests were carried out under representative conditions of real exhaust gases from a heavy duty vehicle's engine. Results showed that the differences in the performances of both materials could not be attributed to hydrodynamic factors being thus proposed an explanation related to the catalyst surface area in contact the inlet feed gas, significantly higher for the most active monolith.
This paper aims at finding optimal adaptive mesh refinement strategies to capture vortical struct... more This paper aims at finding optimal adaptive mesh refinement strategies to capture vortical structures. Due to their efficiency, we focus on a-posteriori mesh refinement methods. In particular, we derive a Hessian error estimator for the h-refinement scheme and a residual-based error estimator for finite volume methods and octree grids. The methods are validated for a classical test for the solution of the advection-diffusion-reaction equation and tested against three different test cases where vortical structures are present. In particular we test the temporal evolution of the Lamb-Oseen vortex, the linear growth-rate of small perturbations in a shear viscous layer and the energy evolution in the isotropic turbulence case. The performance of the proposed estimators and the choice of the optimal quantity of interest is discussed for different test cases.
L'utilisation croissante de vehicules au cours des dernieres decennies a cause une augmentati... more L'utilisation croissante de vehicules au cours des dernieres decennies a cause une augmentation dans les emissions de gaz d'echappement nocifs provoquant des problemes de sante et d'environnement. Cette problematique a conduit les gouvernements a mettre en place des limites d'emissions plus strictes. Afin de respecter ces limites, il est necessaire de developper des systemes de post-traitement plus performants. Parmi plusieurs solutions possibles, l'analyse et l'optimisation de l'impact de l'ecoulement sur les reactions chimiques est une approche importante pour resoudre ce probleme complexe. Au point de vue experimental, il est tres difficile de mesurer le champ de vitesse detaille et la distribution de la temperature et de la concentration. Les simulations numeriques peuvent fournir des informations supplementaires pour comprendre l'interaction entre la distribution de l'ecoulement et l'efficacite des reactions. La simulation numerique d...
The flow distribution within the automotive catalytic converter is an important controlling facto... more The flow distribution within the automotive catalytic converter is an important controlling factor on theoverall conversion efficiency. Capturing the flow features minimizing the computational cost is the first important step towards the solution of the complex full engineering problem. In this work we present a novel approach that combines physical and numerical multi-resolution techniques in order to correctly capture the flow features inside an automotive catalytic converter. While Adaptive Mesh Refinement techniques are optimized in order to minimize the computational effort in the divergent region, a novel subgrid model is developed to describe the flow inside the catalytic substrate placed between the convergent and divergent regions. The proposed Adaptive Mesh Refinement methods are tested for two test cases representative of the flow features found in the divergent region of a catalytic converter. The performance of the new subgrid model is validated against the non-uniformi...
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