Dual fuel engine combustion control strategy optimizing pilot shot quantities

An engine system comprising:

• an engine having a cylinder formed therein, and a piston movable in the cylinder;
• a direct fuel injector arranged to directly inject shots of a pilot fuel into the cylinder in a first engine cycle and a subsequent engine cycle;
• a primary fuel admission valve for admitting a primary fuel for combustion in the cylinder based on autoignition of the pilot fuel in the first engine cycle and the subsequent engine cycle;
• a fuel control system including a sensor structured to produce data indicative of a heat release in the cylinder, and a fueling control unit;
• the fueling control unit being structured to:
• compare the data to phasing error criteria for an earlier shot of the pilot fuel and to different phasing error criteria for a later shot of the pilot fuel, in a the first engine cycle;
• and
• vary a quantity of an earlier shot of the pilot fuel in the subsequent engine cycle, based on the comparing the data to the phasing error criteria, and vary a quantify of a later shot of the pilot fuel in the subsequent engine cycle, based on the comparing the data to the different phasing error criteria.

A dual fuel control system comprising:

• a fueling control unit structured to receive data indicative of a heat release in a cylinder produced in a first engine cycle by combustion of a fuel charge including a primary fuel and a plurality of shots of an autoignited pilot fuel:
• the fueling control unit being further structured to compare the data to different phasing error criteria for each respective one of the plurality of autoignited shots of the directly injected pilot fuel;
• the fueling control unit being further structured to produce a at least one combustion phasing error signal based on the comparison of the data to the different phasing error criteria;
• the fueling control unit being further structured to output a first pilot fuel injection command and a second pilot fuel injection command to form a fuel charge of the primary fuel and the pilot fuel in a subsequent engine cycle;
• and
• the fueling control unit being further structured via the first pilot fuel injection command to vary a quantity of an earlier shot of the pilot fuel in the subsequent engine cycle, based on the at least one combustion phasing error signal, and via the second pilot fuel injection command to vary a quantity of a later shot of the pilot fuel, based on the at least one combustion phasing error signal.