| Popis: |
Engines for A/B/C class vehicles place high emphasis on economic viability. Thus, many innovations focus on optimum system integration of cost effective technologies, which are individually optimized and controlled within the interrelations of engine, exhaust gas aftertreatment system and vehicle. The European project REWARD conducted such a comprehensive approach with a 1.6 liter diesel engine for a small SUV class vehicle. The core of this development is a new combustion concept which is combined with a specifically tailored aftertreatment system. The goal is the demonstration of an increased fuel economy and a reduction of emissions significantly below the Euro 6 limits under real driving conditions. These targets are demonstrated with a vehicle emphasizing that the improvements refer exclusively to the new engine and aftertreatment system development. The approach focuses on conventional combustion parameters such as the optimum design matching of new combustion bowls with advanced fuel injectors, injection characteristics and a reduced in-cylinder charge motion (swirl). Outside of these core features further parameters refer to high-pressure/ low-pressure EGR and the charging system. The target is to minimize engine-out emissions and to provide specific exhaust characteristics which are optimum matched to particular aftertreatment system concepts. Various aftertreatment concepts have been systematically evaluated in view of their performance, reliability and economy. Initially, NOx reduction with a single NOx Storage Catalyst (NSC) was considered. However, even if combined with the low engine-out NOx solution, this initial approach requires excessive NSC purging at elevated exhaust temperatures, which severely deteriorates the fuel economy. Thus, NSC has been completely omitted and replaced by Selective Catalytic Reduction (SCR) with economically “active” urea dosing. Due to a sophisticated temperature management system low temperature operation can be bridged by a diesel Cold Start Concept (dCSCTM) catalyst. The paper describes the comprehensive approach and presents some projected results. |
