Spray-guided Gasoline Direct Injection
• Assess the scope and limitations of spray-guided Gasoline Direct Injection combustion system concepts
• Investigate the aspects of different suitable fuel injectors
Establish design criteria for the geometry and operational parameters of such systems.
• Investigate the potential to reduce cold start emissions by utilizing stratified charge combustion
A stable, misfire free lean operating spray-guided Gasoline Direct Injection combustion system have
an estimated fuel consumption reduction potential of about 20% in the new European driving cycle
(NEDC) which means 20% reduction in CO2 emissions. In fact for typical highway driving (low load)
the fuel consumption reduction in (lean) mode can be up to 40% higher than the same engine operating
in homogeneous mode.
Cold start emissions is a well known problem in the automotive industry. However, by utilizing stratified
cold starts the engine out emissions of unburned fuel prior to catalyst light-off can be dramatically
reduced. Stratified cold starts give us a bonus thanks to the improved vaporization rate; it also enables
cold starts on alternative fuels such as alcohols. This is good since alcohol fuels need much more
energy to vaporize than gasoline.
Why does this combustion system give a fuel The challenge:
consumption reduction? Why is it difficult to design a spray-guided stratified
The fuel consumption reduction is obtained in stratified combustion system which runs stable and without
(late injection combustion mode) and is due to: misfires? The challenge lies in how to create a suitable
stratified fuel cloud which must meet the following
• Much lower heat losses requirements:
• No pump losses
• Higher thermodynamic efficiency due to: • Good stratification
• Higher compression ratio • Fuel/air ratio within ignitibility limits at spark
• Lean burn (lambda > 1) • Not too small and not too steep fuel gradients
• Higher volumetric efficiency • Good mixing ability
• Fast burn • Low cycle-to-cycle variations
• Low sensibility to in-cylinder motion
• Low sensibility to back pressure
• Not too high cross-flow velocities at the spark
• Not too low and not to high turbulence levels at the
• Not too sensitive to flash-boiling
Fuel distribution with laser spectroscopy
(LIF) in optical engine. Spray formation from a fuel injector.
Photograph from a spray chamber.