Parameter Estimation of a DOC from Engine Rig Experiments with a Discretized Catalyst Washcoat Model

Abstract

Parameter tuning was performed against data from a full scale engine rig with a Diesel Oxidation Catalysts (DOC). Several different catalyst configurations were used with varying Pt loading, washcoat thickness and volume. To illustrate the interplay between kinetics and mass transport, engine operating points were chosen with a wide variation in variables (inlet conditions) and both transient and stationary operation was used. A catalyst model was developed where the catalyst washcoat was discretized as tanks in series both radially and axially. Three different model configurations were used for parameter tuning, evaluating three different approaches to modeling of internal transport resistance. It was concluded that for a catalyst model with internal transport resistance the best fit could be achieved if some parameters affecting the internal mass transport were tuned in addition to the kinetic parameters. However it was also shown that a model with negligible internal transport resistance still could obtain a good fit since kinetic parameters could compensate for transport limitations. This highlighted the inherent difficulties using kinetic models with high parameter correlation and also showed the importance of using a kinetic model with a structure that is capable of describing exclusively intrinsic kinetics.

Model-based experimental screening for DOC parameter estimation

“…A thorough description of the experimental set-up, measurements and engine operation design is given in the preceding study (Lundberg et al, 2014).…”

“…The heat transfer parameters including thermal mass (s heat ), environmental temperature (T ∞ ), and a lumped heat transfer coefficient (˛t ot ) were earlier tuned to a satisfactory fit in (Lundberg et al, 2014) for the system at hand and will therefore not be retuned in the current study.…”

“…Previously (Lundberg et al, 2014), the effective diffusivities were evaluated as a method of tuning the transport resistance with the aim of reducing the correlation between mass transport and kinetic parameters. The species were divided into two groups, where the first group contained O 2 , NO, NO 2 , and CO and the second group contained HC.…”

“…In our previous study (Lundberg et al, 2014), an experimental plan that included several different DOC catalyst configurations, was applied to a full scale engine rig system and used for parameter tuning. The best model fit was achieved with a model that included internal transport resistance with the effective diffusivities of the species being tuned in addition to the kinetic parameters.…”

Kinetic Modeling of C3H6 Inhibition on NO Oxidation over Pt Catalyst

“…With a full DOC feed mixture, a number of global kinetic models are present in the literature based on the common Voltz model [13] obtained from lab tests [14,15] to the full-scale engine rig test [16]. Recently, Khosravi et al [14,15] reported a global kinetic model for the NO oxidation reaction in the presence of C3H6 over Pt and bimetallic Pt:Pd catalysts which includes C3H6-SCR, NO oxidation, C3H6 oxidation and N2O formation.…”