CFD Assessment of an After-Treatment System Equipped with Electrical Heating for the Reduction of the Catalyst Light-Off Time

Abstract

<div class="section abstract"><div class="htmlview paragraph">The reduction of the catalyst light-off time at the engine cold start represents a key factor for the pollutant emissions control from vehicles tested on homologation cycles and real drive conditions. The adoption of heating strategies to increase the temperature of the catalytic substrate in the early phase of the engine start is regarded as a promising solution. The present study focuses on the application of electrical heated catalyst (EHC) in an after-treatment line for a spark-ignition gasoline engine. The analysis is carried out by means of an advanced CFD framework, which includes the modeling of catalytic reactions in the substrates and accounts for the thermal evolution of all the components included in the after-treatment system. In this work the model has been extended with: a) the solution of the electrical circuit of the EHC to provide an accurate description of the non-uniform temperature distribution of the coils heated by Joule effect and b) a specific model for the radiative heat transfer from the porous EHC, which plays a significant role in the thermal balance of the device. The simulation model is validated considering an experimental test configuration, suitably instrumented to provide temperature measurements at different locations under different operating conditions. Then, a complete exhaust line has been simulated, analyzing the thermal transient of the catalytic substrate during the different phases of the EHC activation. The reaction light-off in the catalyst is monitored, assessing the benefits in terms of reduction of the overall emissions with respect to the base case.</div></div>