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Extending Stratified Operation Range in Load Map of DISI Engines by Boosting
Technical Paper
2006-05-0353
Sector:
Language:
English
Abstract
Spark ignition engines with direct injection, especially those
with spray-guided combustion strategy, have a high potential
regarding fuel efficiency and therewith CO2 emissions at part
load operation. This benefit mainly results from the lean operation
which is realized with a highly stratified mixture at part load.
Consequently thermal efficiency and charge cycle efficiency
increase significantly. Due to the limited air intake mass of
natural-aspirated engines, the highly efficient stratified
operation is applicable to low loads only. Boosting enables to
increase the air intake mass and therewith the air-fuel ratio, so
that stratified operation can be extended to higher loads. Hence
low fuel consumption can be achieved in a larger area of the engine
map. Further in the conventional stratified operation points the
fuel consumption can be decreased with increasing the air-fuel
ratio by boosting.
This paper presents investigation results which have been
carried out on a single-cylinder DI engine with spray-guided
combustion strategy. The engine was equipped with a compressor. A
strategy is shown which enables the extension of the stratified
charge engine map. The air-fuel ratio was increased
significantly.
The measurement results show that a significant reduction of the
fuel consumption in the stratified charge operation was achieved
with this boosting strategy. By thermodynamic analyses of the
engine process, the effects of boosting on charge cycle efficiency
and thermal efficiency was evaluated.