Abstract
Turbocharged diesel engines suffer from poor drivability, mostly at low loads and speeds, leading also to overshoot in exhaust emissions (primarily PM/soot and NOx) during the transient operation after a speed or load increase. The main cause for this problematic behavior is located in the turbocharger in the form of high moment of inertia and unfavorable aerodynamic-type compressor flow characteristics. In the present work, various alternative turbocharging configurations are reviewed that have proven successful in improving the dynamic diesel engine operation. The configurations studied are: combined supercharging, variable geometry turbine, electrically assisted turbocharging, two stage series and sequential turbocharging, as well as lower turbine moment of inertia. It is shown that significant improvement in the engine’s transient response can be realized through reduction in the turbocharger mass moment of inertia (using lighter materials and/or more than one units). Increasing the available turbine torque (e.g. through elevated turbine back pressure in a variable-geometry turbine) is another successful option, as well as enhancement of the compressor boost pressure (e.g. through the use of a positive displacement compressor upstream of the turbocharger). Finally, the use of external energy (e.g. in the form of electrical assistance on the turbocharger shaft during the critical turbocharger lag phase) is another recently developed and highly promising measure to mitigate the drawbacks of the poor transient performance of turbocharged diesel-engined vehicles and limit their exhaust emissions.
Highlights
The diesel engine has assumed for many decades a leading role in both the medium and medium-large transport sector
Since concerns over greenhouse gas emissions are reflected in the automotive engines legislation too (EU Directives 443/2009 EC for passenger cars and 510/2011/EC for light-duty vans), it is not surprising that the production of turbocharged vehicles is constantly increasing
The latter is responsible for an unfavorable engine behavior during transients through a well-established phenomenon known as turbocharger lag; turbo lag leads, on the one hand, to problematic torque build-up and poor vehicle drivability, and on the other, to a considerable increase in engine-out particulate matter (PM), gaseous, and even noise emissions (Watson and Janota, 1982; Winterbone, 1986; Rakopoulos et al, 2010a)
Summary
Turbocharged diesel engines suffer from worse transient performance than their naturally aspirated counterparts, mostly at low loads and speeds. This leads to overshoot in engine-out exhaust emissions (primarily particulate matter/soot and NOx) after a speed or load increase, as well as poor drivability. Various alternative turbocharging configurations are reviewed that have proven successful in improving the dynamic diesel engine operation. These configurations are combined supercharging, variable-geometry turbine, electrically assisted turbocharging, two-stage series and sequential turbocharging, and lower turbine moment of inertia.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
