Ducted fuel injection systems and methods implementing pilot injection

A method for injecting fuel into a combustion chamber of an internal combustion engine, comprising:

• determining, using control circuitry, whether in-cylinder temperature of the combustion chamber is within a predetermined temperature range, the predetermined temperature range being a non-zero and non-startup temperature values;
• outputting, under control of the control circuitry, to the combustion chamber of the internal combustion engine via a fuel injection system and at least one duct inside the combustion chamber of the internal combustion engine, a plurality of pilot injections of fuel in a predetermined range before top dead center (BTDC) for a combustion cycle of the internal combustion engine;
• and
• outputting, under control of the control circuitry, to the combustion chamber via the fuel injection system and the at least one duct, a main injection of fuel for the combustion cycle of the internal combustion engine after said outputting the plurality of pilot injections,
• wherein the main injection of fuel passes through the at least one duct and the plurality of pilot injections of fuel pass through the at least one duct,
• wherein an amount of fuel of the plurality of pilot injections is less than an amount of fuel of the main injection,
• wherein the plurality of pilot injections of fuel per combustion cycle is from two to six pilot injections,
• wherein the predetermined range before top dead center (BTDC) of the plurality of pilot injections of fuel is from 85 to 50 degrees BTDC,
• wherein said outputting the main injection is such that the main injection begins before top dead center (TDC) and ends after top dead center (TDC), and
• wherein said outputting the plurality of pilot injections of fuel is performed only in a case where the in-cylinder temperature of the combustion chamber is determined to be within the predetermined temperature range.