Reactivity controlled compression ignition engine with exhaust gas recirculation

A method of operating an internal combustion engine configured to utilize fuels having two different reactivities, the method comprising:

• mixing via an exhaust gas recirculation (EGR) system a portion of exhaust gasses with intake air to provide an intake air/exhaust gas mixture;
• introducing in a combustion chamber the intake air/exhaust gas mixture;
• introducing into the combustion chamber a first fuel charge of a first reactivity at a first introduction time during a intake-compression cycle;
• subsequently introducing into the combustion chamber a second fuel charge of a second reactivity at a second introduction time during the intake-compression cycle;
• combusting the first and second fuel charges in the combustion chamber in response to the second introducing step;
• monitoring at least one engine operating parameter reflective of the combusting of the first and second fuel charges;
• and
• selecting from and adjusting in a correlated manner the EGR system and the second introducing step.

A method of adjusting combustion in an internal combustion engine comprising:

• mixing intake air with exhaust gasses via an exhaust gas recirculation (EGR) system to produce an intake air/exhaust gas mixture at a mixing ratio;
• introducing the intake air/exhaust gas mixture into a combustion chamber during an intake stroke as a piston moves a cylinder of the combustion chamber from a top dead center (TDC) position to a bottom dead center (BDC) position;
• introducing an first fuel charge having a first reactivity into a combustion chamber at a first introduction time so that the first fuel charge generally uniformly disperses within the combustion chamber;
• subsequently introducing a second fuel charge having a second reactivity into the combustion chamber at a second introduction time so that the second fuel charge forms a stratified region within the combustion chamber;
• initiating auto-ignition of the stratified region of the second fuel charge at an ignition time during a compression stroke as the piston moves from the BDC position to the TDC position;
• combusting the first fuel charge and the intake air/exhaust gas mixture in the combustion chamber;
• determining the ignition time by use of a sensor;
• and
• selecting from and adjusting in a correlated manner the mixing ratio and the second introduction time based in part on the determining step.