Global kinetic model for predicting HC slip from Diesel Oxidation Catalysts during active regeneration of soot
Rama Krishna Dadi, Cummins Inc
We developed a global kinetic model for predicting HC slip from DOCs during active regeneration. Kumar et al. [1] deployed an in-house diesel fuel injection capability to get light-off curves for diesel fuel oxidation. They showed that diesel fuel oxidation is characteristically different from the oxidation of commonly used surrogate species for diesel fuel. The key differences are light-off behavior, self -inhibition of diesel fuel and NO inhibition. In the light of these differences, there is a need to develop kinetic models for diesel fuel oxidation to explain the DOC light-off performance under active regeneration conditions. A global kinetic model, which can explain the important characteristics of diesel fuel oxidation, is presented for different PGM loadings and hydrothermal aging conditions. Langmuir-Hinshelwood kinetics is used to describe the oxidation of diesel fuel. NO inhibition of diesel fuel oxidation is described by a simple inhibition term in the denominator of the rate expression. The differences in the light-off behavior that arise due to different hydrothermal aging conditions and different PGM loadings are described by tuning the reaction pre-exponential factor. This work also investigates the main differences in the kinetic model for diesel fuel oxidation and dodecane oxidation. One of the striking differences is the activation energies for diesel fuel oxidation and dodecane oxidation. Since diesel fuel has different kinds of HCs and each of them ignite at different temperatures, rate of oxidation of diesel fuel gradually increases with temperature resulting in a lower activation energy for diesel fuel oxidation compared to dodecane oxidation. An aging model that can describe PGM performance for different hydrothermal aging conditions is presented. The developed kinetic model of diesel fuel oxidation in conjunction with the aging model for PGM can determine DOC performance at any specific aging condition during active regeneration.
References:
- Kumar, A., Zokoe, R., Joshi, S., Kamasamudram, K. et al., “Reactor System with Diesel Injection Capability for DOC Evaluations,”SAE Technical Paper 2018-01-0647, 2018, doi:10.4271/2018-01-0647
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