Emissions Control Models

Contributed by Oak Ridge National Laboratory

Emissions control has steadily risen in level of importance both from a regulatory standpoint and from a consumer perspective.  As the result of a collaborative effort between NREL and ORNL, two new emissions control models have been developed.  The two models are for a diesel oxydation catalyst with and without an integrated diesel particulate filter.  Previous emissions models determined the tailpipe out emissions based on constituent conversion efficiencies.  The conversion efficiency for each constituent was defined as a function of catalyst temperature.  The catalyst temperature was determined based on the physical properties of the exhaust system, the exhaust flow rate, and the exhaust temperature.  The new models add several new dimensions to the conversion efficiency calculation.  The efficiencies are now a function of catalyst temperature, exhaust temperature, space velocity (i.e. combination of catalyst geometry and exhaust flow rate), oxygen concentration, and critieria emissions concetrations.  Based on test data collected at ORNL, regression coefficients have been derived to the data with respect to these input parameters to provide the conversion efficiency values.  Currently, the diesel oxydation catalyst model is only available for use with the FC_CI67_emis and the FC_CI60_emis engine data files.  In future versions of ADVISOR we expect to include emission models for an NOx adsorber.

Figure 1 below shows how the model has been integrated into ADVISOR using a boolean switch, if ex_ornl_bool is set to 1 the emission control models developed at ORNL will be used.  If set to 0 the standard ADVISOR relationships will be active.  Figure 2 summarizes the inputs and outputs included in the calculation of the specific constituent removal efficiencies.  Within each of the *Conversion blocks there is a functional relatioship defined correlating the removal efficiency to the set of input parameters.  The format of the functional relationship and the coefficients of the relationship have been derived based on experimental data.  It is recommended that you do not modify the relationships or the coefficients at this time.

Figure 1: Selection of Emissions Control Models

Figure 2: Calculation of Emissions Removal Efficiencies in ORNL oxydation catalyst model

We expect that there will be significant development in this section of the model in future versions of ADVISOR so please do forward any comments or recommendations you might have to advisor@nrel.gov.

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Last revised:  [08/20/01] tm
Created: [08/20/01] tm