SIMCAT is a series of diesel aftertreatment catalyst models developed by TNO’s Business Unit Automotive. In order to ensure good compatibility of results between the real catalysts and the models, the models are fitted using engine testbench data with a dedicated tool that minimises the time required to fit and validate the models. The accurate simulation models reduce the amount of real testing for developing, calibrating and testing the aftertreatment system and its control strategy. SIMCAT provides the automotive industry with a cost-effective solution for designing cleaner diesel emission systems, complying with new and stringent emission standards for diesel-fuelled cars and heavy-duty vehicles.

SIMCATDesigning emission solutions for a cleaner planet

SCR systems use urea as a reducing agent to

effectively eliminate nitrogen oxides (NOx)

from diesel exhaust gases. Optimising the

SCR is a complex task, as is the development

of a DPF regeneration strategy. SIMCAT is a

library of a DOC (Diesel Oxidation Catalyst),

DPF (Diesel Particulate Filter), SCR (Selective

Catalytic Reduction) and SCO (Selective

Catalytic Oxidation) catalyst models (see

figure SIMCAT catalyst model library).

SIMCAT eases the process of developing

(integrated) exhaust aftertreatment systems

by providing realistic simulations of the cata-

lysts steady state and dynamic behaviour.

SIMCAT model, technical details• SCR catalyst model

The SCR is a phenomenological model. It

describes the different physical and chemical

processes that take place inside the catalyst

rather than using catalyst performance

maps. The one-dimensional channel

representation of the catalyst is discretised

over the catalyst length. Gas concentrations,

temperature and ammonia coverage

distributions over the catalyst length can be

analysed. The model can be used for OBD and

control developments for SCR as well as for

dimensioning the catalyst.

TNO_SIMCAT leaflet.indd 2 07-04-2009 15:36:03

TNO Science and IndustryBusiness Unit AutomotivePowertrainsPostbus 7565700 AT HelmondThe Netherlands

Edwin van den EijndenT +31 15 269 73 29F +31 40 265 26 01edwin.vandeneijnden@tno.nl

tno.nl

Contact

• DOC and SCO models

The DOC and SCO models are also phenome-

nological, one-dimensional models.

The DOC model describes the process of NO

and HC oxidation. The SCO model represents

a Pt-based slipcat that converts possible NH3

slip from an SCR catalyst. The DOC model can

be used for optimising passive and active

regeneration strategies of the DPF. The effect

of DOC and SCO on the SCR catalyst efficiency

can also be studied.

• DPF model

The DPF model represents a wall-flow filter

and calculates the soot quantity, flow,

pressure and temperature distributions over

the (discretised) filter length during loading

and regeneration. The “filtration” part of the

model represents both the deep-bed and

the cake filtering phases. A version of the

DPF model with a catalytic Pt coating is also

available. These DPF models can be used

to develop regeneration strategies as well

as perform dimensioning and optimisation

studies.

Integrated aftertreatment simulationThe SIMCAT models can be used in the

ADVANCE modelling and simulation environ-

ment and can be connected to the DYNAMO

mean-value engine model. ADVANCE is a

MATLAB/Simulink® environment developed

by TNO’s Business Unit Automotive.

It provides an open, intuitive environment

for modelling and control development.

Model fit toolsEach of the models is validated based on

testbench results obtained from engine and

aftertreatment systems. In order to have a

good model representation of the catalyst,

the model parameters must be fitted accor-

ding to a specific coating/substrate/ageing

stage of the catalyst. For this purpose a test

sequence has been developed to characterise

the steady state and transient behaviour of

the catalysts. For DOC, DPF, SCR and SCO

dedicated fit tools have been developed.

A figure of the SCR fit tool is shown on this

page. These fit tools reduce the time to fit

the models to engine testbench data to

around two days for each catalyst.

SIMCAT simulation applications

• Feasibility emission targets for a certain

cycle

• Study of required catalyst configuration:

particulate Filter/Oxicat/SCR/clean-up

catalyst

• Dimensioning catalyst

• Control development (open and closed

loop)

• Reduce calibration effort on test bench

SIMCAT real-time applications

• Hardware In the Loop

• State estimator: NH3 storage, NOx and

NH3 SCR out (controller)

• Advanced control algorithms

SIMCAT catalyst model library

Fit tool user-interface

DOCmodel

DPFmodel

SCRmodel

SCOmodel

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