Turbo Compressor for Efficient High-Pressure Air Supply in Catalyst Heaters

The expected requirements of future emission legislations for internal combustion engines (ICE), like EU7, require a very short start-up time of the emission reduction systems in the exhaust after treatment and an effective operation of these systems in all driving conditions. The critical aspect for effective operation of the exhaust after treatment system is to run the catalyst above the so-called light-off temperature. It is therefore necessary to reduce the time to reach light-off temperature during engine start-up. For periodically activated systems, especially in hybrid powertrains where the catalyst cools down during electrical drive modes, it is also necessary to maintain light-off temperature. To overcome these challenges, the potential of in-cylinder exhaust thermal management approaches is limited and external measures like secondary air injection (SAI), electrically heated catalysts (EHC) or fossil fuel burners (Burner) are required. These different external solutions have unique advantages and requirements for the air supply system. The air supply units are faced with challenging requirements concerning mass flow, pressure ratio, and installation space. The three systems SAI, EHC, and fossil burner are compared in this paper and the requirements for the necessary air supply are derived. Possible solutions for the corresponding air supply units are investigated and compared.