Diesel oxidation catalyst and particulate filter modeling in active – Flow configurations Ming Zheng * , Siddhartha Banerjee Mechanical, Automotive and Materials Engineering, University of Windsor, 401 Sunset Ave, Windsor, Ontario, Canada N9B 3P4 article info Article history: Received 22 April 2008 Accepted 1 April 2009 Available online 12 April 2009 Keywords: Diesel oxidation catalyst Diesel particulate filter Active flow-control abstract A one-dimensional transient model is developed in order to carry out theoretical investigations on the active flow diesel aftertreatment configurations. Simulations are carried out to predict the thermal response of particulate filters during active flow regeneration operations. Results indicate that the active flow-control strategies can achieve higher energy efficiency in aftertreatment operations. The energy effi- ciency analysis is carried out using various active-flow configurations. The theoretical model is validated using the experimental results. Further empirical investigation is carried out in order to study energy effi- ciency of supplemental fuel in the active-flow configurations. Different engine operating modes are also investigated with the active-flow configurations. It is observed that diesel aftertreatment with active flow can significantly improve in the supplemental energy efficiency. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction In order to meet the stringent automotive emission regulations, increasing number of diesel vehicles around the world use catalytic converters. Diesel exhaust aftertreatment applications include Die- sel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) and NOx absorber. In order to enable aftertreatment operations, diesel engines commonly require supplemental energy to raise the other- wise relatively low exhaust temperature [1]. The appropriate after- treatment operation is largely dependent on the sufficient temperature level of the substrate. In order to improve the overall energy efficiency and keeping the most reactive conditions of the converters of the aftertreatment operation systems, measures are being adopted such as the supplemental fuel delivery, the heating of the exhaust gas and the active flow-control strategies that in- clude the periodic alternating exhaust flow paths through the aftertreatment device [1–4]. Depending on the vehicle application an effective and efficient active flow control scheme can be devel- oped with an objective to maintain conditions favorable to after- treatment operations. The supplemental energy input can be efficiently applied in the exhaust stream by combining various active flow-control strate- gies such as parallel alternating flow, flow stagnation and periodic flow reversal to reduce the overall energy penalty drastically. Dif- ferent active flow schemes are shown in Fig. 1. It is important to develop a suitable theoretical model that can simulate aftertreat- ment operations under these active flow control configurations. Several researchers have developed DOC and DPF models that can cater various flow control aftertreatment operation conditions [2,3]. The objective of the research presented in this paper is to de- velop a one-dimensional DOC–DPF model that can simulate after- treatment operations and behaviors under extreme conditions of exhaust mass flow rates, oxygen concentrations and temperatures. In order to identify operating window for safe, effective and energy efficient regeneration, both numerical and experimental studies are carried out. Further experiments are carried out in order to per- form an energy efficiency analysis of various active aftertreatment operations at low exhaust flow conditions. The present study focuses on the evaluation of the energy effi- ciency on active-flow configurations of diesel aftertreatment sys- tems. The active flow schemes include partial flow control of the exhaust gas through the parallel or reversal flow aftertreatment system with the addition of supplemental energy at the upstream of the aftertreatment system, operating at various flow rates and exhaust gas temperatures. The theoretical and empirical results of aftertreatment behaviors under these conditions are presented here. A parallel flow system with DOC–DPF units operates in alternat- ing cycles of filtration and regeneration with various space veloci- ties. An active regeneration with external supplemental energy is relatively energy efficient with reduced space velocities, when the exhaust temperature is below the threshold limit for the after- treatment operations. By sharing the operating cycle with other parallel devices, the partial flow restriction (PFR) operation can effectively reduce the supplemental energy consumption to suc- cessfully carry out active regeneration. For energy efficient opera- tions, the PFR switches between different modes as shown in Table 1359-4311/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.applthermaleng.2009.04.017 * Corresponding author. Tel.: +1 519 253 3000x2636; fax: +1 519 973 7007. E-mail address: mzheng@uwindsor.ca (M. Zheng). Applied Thermal Engineering 29 (2009) 3021–3035 Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng