A physico-chemical model of a Cu-zeolite SCR/DPF-system involving NH\u2083 storage and SCR reactions as well as soot oxidation reactions with NO\u2082 has been developed and validated based on fundamental experimental investigations on synthetic gas test bench. The goal of the work was the quantitative modeling of NO x and NH\u2083 tailpipe emissions in transient test cycles in order to use the model for concept design analysis and the development of control strategies. Another focus was put on the impact of soot on SCR/DPF systems. In temperature-programm
ed desorption experiments, soot-loaded SCR/DPF filters showed a higher NH\u2083 storage capacity compared to soot-free samples. The measured effect was small, but could affect the NH\u2083 slip in vehicle applications. A bimodal desorption characteristic was measured for different adsorption temperatures and heating rates. Therefore, a multiple-site NH\u2083 adsorption and desorption model was implemented which proved to be in good agreement with the experimental findings. In steady-state NO x conversion experiments for NO\u2082/NO x ratios up to 50%, the SCR reactivity was unaffected by the soot loading under the applied test conditions reaching full conversion for a large temperature range. For even higher NO\u2082/NO x ratios, an increase in NO x conversion efficiency was detected for temperatures up to 250°C for soot-loaded filters. An extended SCR reaction mechanism involving reactions on two active sites, NH\u2084NO\u2083 formation and the inhibition by surface nitrate species was calibrated. The model was validated with NEDC data showing high model quality for both, NO x and NH\u2083 slip prediction. The same parameter set, derived from synthetic gas experiments, was used and an additional water adsorption model was calibrated. The transferability of the kinetics to real exhaust conditions was confirmed by supplementary simulations of FTP75 and US06 data. The promoting soot effect on NO x conversion was further investigated by modeling, resolving the local reaction of NO\u2082 in the soot layer and the change in the SCR stoichiometry.
A physico-chemical model of a Cu-zeolite SCR/DPF-system involving NH\u2083 storage and SCR reactions as well as soot oxidation reactions with NO\u2082 has been developed and validated based on fundamental experimental investigations on synthetic gas test bench. The goal of the work was the quantitative modeling of NO x and NH\u2083 tailpipe emissions in transient test cycles in order to use the model for concept design analysis and the development of control strategies. Another focus was put on the impact of soot on SCR/DPF systems. In temperature-programmed desorption experiments, soot-loaded SCR/DPF filters showed a higher NH\u2083 storage capacity compared to soot-free samples. The measured effect was small, but could affect the NH\u2083 slip in vehicle applications. A bimodal desorption characteristic was measured for different adsorption temperatures and heating rates. Therefore, a multiple-site NH\u2083 adsorption and desorption model was implemented which proved to be in good agreement with the experimental findings. In steady-state NO x conversion experiments for NO\u2082/NO x ratios up to 50%, the SCR reactivity was unaffected by the soot loading under the applied test conditions reaching full conversion for a large temperature range. For even higher NO\u2082/NO x ratios, an increase in NO x conversion efficiency was detected for temperatures up to 250°C for soot-loaded filters. An extended SCR reaction mechanism involving reactions on two active sites, NH\u2084NO\u2083 formation and the inhibition by surface nitrate species was calibrated. The model was validated with NEDC data showing high model quality for both, NO x and NH\u2083 slip prediction. The same parameter set, derived from synthetic gas experiments, was used and an additional water adsorption model was calibrated. The transferability of the kinetics to real exhaust conditions was confirmed by supplementary simulations of FTP75 and US06 data. The promoting soot effect on NO x conversion was further investigated by modeling, resolving the local reaction of NO\u2082 in the soot layer and the change in the SCR stoichiometry.
