For diesel engines to meet current and future emissions levels, the amount of EGR required to reach these levels has increased dramatically. This increased EGR has posed big challenges for conventional turbocharger technology to meet the higher emissions requirements while maintaining or improving other vehicle attributes, to the extent that some OEMs resort to multiple turbocharger configurations. These configurations can include parallel, series sequential, or parallel - series turbocharger systems, which would inevitably run into other issues, such as cost, packaging, and thermal loss, etc.
This study, as part of a U.S. Department of Energy (USDoE) sponsored research program, is focused on the experimental evaluation of the emission and performance of a modern diesel engine with an advanced single stage turbocharger.
A production IHI (Ishikawajima Harima Heavy Industries) turbocharger was selected as the base architecture for the turbocharger design with optimizations focused on compressor impeller and turbine wheel designs.
An advanced impeller design was used on the compressor side to improve the efficiency and surge margin at low mass flow areas of the compressor map, allowing greater EGR flow while extending the flow capacity by using an active casing treatment on the compressor cover.
Mixed flow turbine technology was used on the turbine side, due to its performance characteristics; particularly high efficiency at low speed ratios relative to the base conventional radial flow turbine. This characteristic is relevant to increased EGR operation required for future diesel applications.
Both steady state and transient engine dynamometer testing of FTP transient cycles at Tier II Bin 5 emission levels show that the advanced turbocharger technology enables around 3% fuel economy improvement on the engine while meeting the same emissions level.
