Overview of boosting options for future downsized engines

Driven by a demand for better fuel economy and increasingly stringent emissions regulations over a wide range of customers and applications, engine manufacturers have turned towards engine downsizing as the most potent enabler to meet these requirements. With boosting systems becoming ever more numerous as the technical solutions to complex boosting requirements of the internal combustion engine increase, it is time for an overview of available and under development boosting technologies and systems and for a discussion of their relevance to downsizing efforts. The presented analysis shows that there are no standard solutions for all the different applications as the trends indicate a rising complexity to meet with the extreme boosting requirements predicted for the remainder of the decade. These trends include variable geometry, a shift from single to two (or more) stages, extensive actuation for bypassing exhaust flows, exhaust flow regulation and pulsating exhaust energy recovery, severe electrification and an extensive effort downstream from the turbine to capture waste heat after the principal turbocharger/supercharger system.