Engine combustion control at low loads via fuel reactivity stratification

A compression ignition combustion method for an internal combustion engine having a combustion chamber situated between:

• A. an intake system adjustable between a fully-open state providing maximum airflow to the combustion chamber and a restricted state having lesser airflow to the combustion chamber, and
• B. an exhaust system adjustable between a fully-open state providing maximum exhaust flow from the combustion chamber and a restricted state having lesser exhaust flow from the combustion chamber,
• the method including the steps of:
• i. supplying an initial fuel charge into the combustion chamber;
• ii. thereafter supplying a subsequent fuel charge into the combustion chamber, the subsequent fuel charge having a different reactivity than the first fuel charge,
• during each of several successive combustion cycles wherein:
• a. the engine is operating at a load of less than 4 bar Indicated Mean Effective Pressure (IMEP), and
• b. at least one of:
• (1) the intake system is in the restricted state during at least a portion of the intake stroke, and
• (2) the exhaust system is in the restricted state during at least a portion of the exhaust stroke.

The method of 13 wherein:

• a. the engine includes:
• (1) a first supply containing a fuel having a first reactivity, and
• (2) a second supply containing a material having a second reactivity;
• b. at start-up of the engine, all fuel charges supplied into the combustion chamber during each of the successive combustion cycles include the fuel and exclude the material;
• and
• c. subsequently, at least some of the fuel charges supplied into the combustion chamber during successive combustion cycles include both the fuel and the material.

A compression ignition combustion method for an internal combustion engine having:

• A. a combustion chamber situated between:
• I. an intake system adjustable between a fully-open state providing maximum airflow to the combustion chamber and a restricted state having lesser airflow to the combustion chamber, and
• II. an exhaust system adjustable between a fully-open state providing maximum exhaust flow from the combustion chamber and a restricted state having lesser exhaust flow from the combustion chamber,
• B. a first supply containing a fuel having a first reactivity;
• C. a second supply containing a material having a second reactivity;
• the method including the steps of:
• a. providing fuel charges to the engine upon start-up of the engine, each fuel charge including the fuel and excluding the material;
• b. during post-start-up operation of the engine, providing fuel charges to the engine which include both the fuel and the material.