Smart Engine Control Strategy for the Fuel Efficiency Improvement via Understanding the Unique Behavior of TWC
To be published on March 25, 2019 by SAE International in United States
Annotation of this paper is available
The worldwide fuel economy compliance level has been tightening, at the same time, LEV-III/Euro-6d/China-6/BS-6 regulations for NMOG and NOx emissions are being introduced or already effective. Therefore, intensive research effort has been conducted in order to improve the fuel efficiency of passenger cars and reduce exhaust emission. In response to these demands, turbocharged gasoline direct injection (TGDI) engine is being introduced for gasoline vehicles in consideration of fuel efficiency improvement, high output and driving performance compared to naturally aspirated (NA) engine. However, due to its larger thermal mass from the turbo hardware in the exhaust, it suffers from the cold-start emission. The main hazardous gases emitted from gasoline vehicles are CO, HC and NOx, and a three-way catalyst (TWC) is installed for the purification of these harmful emissions. But vehicle-mounted TWC converters gradually reduce the ability to purify hazardous emissions as vehicle mileage increases. Here, the degradation of TWC is caused by chemical poisoning and thermal sintering. The performance index of TWC is generally closely related to Oxygen Storage Capacity (OSC), and OSC also decreases as the TWC performance decreases. In this study, we investigated the change of tailpipe emissions according to the degradation of the TWC performance used in the 1.4 TGDI Elantra. For example, during transient conditions such as cold-start, fuel-cut, and O2 purge events, the tailpipe emission performance significantly depends on TWC properties such as the dispersion of active metals and OSC. Moreover, overall aftertreatment performance of TWC is determined by the exhaust composition (lambda) as well as its temperature controlled by the engine controls. We will propose smart engine control strategies to improve the fuel efficiency by understanding the relationship between the emission control performance and the properties of TWC.