Low emission diesel combustion system with low charge-air oxygen concentration levels and high fuel injection pressures

A method of operating an internal combustion diesel engine comprising:

• taking into a combustion chamber of an internal combustion diesel engine a mixture of air and recirculated exhaust gas, wherein the oxygen concentration of said mixture of air and recirculated exhaust gas is between 11% and 14%;
• injecting fuel into said combustion chamber at a fuel injection pressure exceeding 2000 bar;
• and
• combusting said fuel in said combustion chamber with said mixture of air and recirculated exhaust gas, thereby producing useful work and a new quantity of exhaust gas, said new quantity of gas including a level of nitrogen oxides (NOx) equal to or less than 0.2 grams per horsepower-hour of work performed by the engine and a smoke content at or below a Bosch Smoke Number of 3.

An internal combustion engine system comprising:

• one or more cylinders, each cylinder providing a combustion chamber;
• one or more fuel injectors in communication with said cylinder(s), capable of injecting fuel into each said combustion chamber at fuel injection pressures exceeding 1800 bar;
• an air intake line operatively connected to the cylinder(s), to provide air to the combustion chamber(s);
• an exhaust line also operatively connected to the cylinder(s), to receive exhaust gas from the combustion chamber(s), and including means for recirculation of a portion of said exhaust gas to said air intake line;
• means for combining recirculated exhaust gas with ambient air in said air intake line;
• an EGR control valve operated so as to control the oxygen concentration of the combined recirculated exhaust gas and ambient air to a value below 16%;
• one or more compressors operatively connected to the air intake line, to pressurize said recirculated exhaust gas and/or ambient air before their entry into said combustion chamber(s);
• and
• a controller programmed to control the quantity of fuel injected in relation to the extent of pressurization of said recirculated exhaust gas or ambient air taken into the combustion chamber so as to maintain the level of nitrogen oxides (NOx) in the exhaust gas equal to or below 1.0 gram per horsepower-hour.

An internal combustion engine system comprising:

• one or more cylinders, each cylinder providing a combustion chamber;
• one or more fuel injectors in communication with said cylinder(s), capable of injecting fuel into each said combustion chamber at fuel injection pressures exceeding 2000 bar;
• an air intake line operatively connected to the cylinder(s), to provide air to the combustion chamber(s);
• an exhaust line also operatively connected to the cylinder(s), to receive exhaust gas from the combustion chamber(s), and including means for recirculation of a portion of said exhaust gas to said air intake line;
• means for combining recirculated exhaust gas with ambient air in said air intake line;
• an EGR control valve operated so as to control the oxygen concentration of the combined recirculated exhaust gas and ambient air to a value between 11% and 14%;
• one or more compressors operatively connected to the air intake line, to pressurize said recirculated exhaust gas and/or ambient air before their entry into said combustion chamber(s);
• and
• a controller programmed to control the quantity of fuel injected in relation to the extent of pressurization of said recirculated exhaust gas or ambient air taken into the combustion chamber so as to maintain the level of nitrogen oxides (NOx) in the exhaust gas equal to or below 0.2 grams per horsepower-hour.