Cold start for high-octane fuels in a diesel engine architecture

A method of operating a compression ignition engine, the compression ignition engine including an engine cylinder having an inner surface, a head surface, a piston disposed and configured to move in the engine cylinder, an intake valve, an exhaust valve, and an ignition-assist device, the inner surface of the engine cylinder, the piston, the head surface, the intake valve, and the exhaust valve defining a combustion chamber, the piston and the head surface defining a bowl region of the combustion chamber, the method comprising the steps of:

• opening the intake valve to draw a volume of air into the combustion chamber, the volume of air having a mass-average temperature of less than about 150° C. at the moment the volume of air passes through the intake valve;
• moving the piston from a bottom-dead-center (BDC) position to a top-dead-center (TDC) position in the combustion chamber at a compression ratio of between about 15 and about 25;
• injecting a volume of fuel at an engine crank angle between 0 and 360 degrees, the fuel having a cetane number of less than about 30, the volume of fuel and the volume of air forming an air-fuel mix;
• closing the intake valve;
• and
• combusting substantially all of the volume of fuel.

A method of operating a compression ignition engine during cold-start, the compression ignition engine including an engine cylinder having an inner surface, a head surface, a piston disposed and configured to move in the engine cylinder, an intake valve, an exhaust valve, and an ignition-assist device, the inner surface of the engine cylinder, the piston, the head surface, the intake valve, and the exhaust valve defining a combustion chamber, the compression ignition engine further comprising a turbocharger, a supercharger and/or a turbo-compounding device, the method comprising the steps of:

• passing a volume of air through the turbocharger, the supercharger and/or the turbo-compounding device;
• opening the intake valve to draw the volume of air into the combustion chamber;
• moving the piston from a bottom-dead-center (BDC) position to a top-dead-center (TDC) position in the combustion chamber at a compression ratio of between about 15 and about 25;
• injecting no more than about 25% of a volume of fuel into the combustion chamber while the intake valve is open, the fuel having a cetane number of less than about 30;
• closing the intake valve;
• injecting at least about 75% of the volume of fuel into the combustion chamber at an injection pressure of at least about 1,000 bar while the intake valve is closed, the volume of fuel and the volume of air forming a fuel-air mix;
• igniting a portion of the volume of fuel;
• and
• combusting substantially all of the volume of fuel.

A method of operating a compression ignition engine, the compression ignition engine including an engine cylinder having an inner surface, a head surface, a piston disposed and configured to move in the engine cylinder, an intake valve, an exhaust valve, and an ignition-assist device, the inner surface of the engine cylinder, the piston, the head surface, the intake valve, and the exhaust valve defining a combustion chamber, the method comprising the steps of:

• opening the intake valve during a first time period to draw a volume of air into the combustion chamber, the volume of air having a mass-average temperature of less than about 150° C. at the moment the volume of air passes through the intake valve;
• moving the piston from a bottom-dead-center (BDC) position to a top-dead-center (TDC) position in the combustion chamber at a compression ratio of between about 15 and about 25;
• injecting a volume of fuel into the combustion chamber, the fuel having a cetane number of less than about 20, the volume of fuel and the volume of air forming an air-fuel mix;
• closing the intake valve;
• and
• combusting substantially all of the volume of fuel,
• wherein at least about 20% of the volume of fuel is pre-mixed with the volume of air immediately prior to ignition.