A High Dilution Stoichiometric Combustion Concept Using a Wide Variable Spark Gap and In-Cylinder Air Injection in Order to Meet Future CO
Requirements and World Wide Emission Regulations
Continuously Variable Cam Phasers (CVCP) controlling both the exhaust and intake camshaft phasing in combination with air assist direct fuel injection and a wide variable spark gap is utilized to reduce the fuel consumption for a 4-valve Turbo Charged (TC) Spark Ignition (SI) engine.
The spark plug and the air-assisted direct fuel injector are integrated into one unit in order to facilitate packaging in a modern 4-valve combustion chamber. This integrated component is referred to as the Spark Plug Injector (SPI).
CVCP's are used to reduce pumping work by diluting the charge with large amounts of residual exhaust gas. This strategy, along with stoichiometric homogeneous operation enables the use of a Three Way Catalyst (TWC), considered to be a prerequisite to meet the emission standards of Ultra Low Emission Vehicles (ULEV) II and beyond.
The ignition quality deteriorates with increasing levels of residual exhaust gas dilution. This is solved by applying a high energy ignition coil and a variable spark gap. The spark gap can be varied between 1 to 4 mm.
In order to achieve an acceptable overall burning angle a small amount of air, at 750 kPa absolute pressure, is injected into the combustion chamber via the SPI in the middle of the compression stroke.
Results show that part load Brake Specific Fuel Consumption (BSFC) is decreased by approximately 10%. Engine out Nitric Oxides (NOx) and Carbon monOxides (CO) emissions decrease, whereas unburned HydroCarbons (uHC) increase.
Citation: Olofsson, E., Alvestig, P., Bergsten, L., Ekenberg, M. et al., "A High Dilution Stoichiometric Combustion Concept Using a Wide Variable Spark Gap and In-Cylinder Air Injection in Order to Meet Future CO2 Requirements and World Wide Emission Regulations," SAE Technical Paper 2001-01-0246, 2001, https://doi.org/10.4271/2001-01-0246. Download Citation
Eric Olofsson, Per Alvestig, Lars Bergsten, Martin Ekenberg, Anders Gawell, Anders Larsén, Raymond Reinmann
Saab Automobile AB
SAE 2001 World Congress
Emission Control and Fuel Economy for Port and Direct Injected SI Engines-PT-91, Variable Valve Actuation 2001-SP-1599, SAE 2001 Transactions Journal of Engines-V110-3