Combustion control system and method for switching between spark and pilot-ignited operating modes in dual fuel engine

A combustion control system for a dual fuel engine comprising:

• a combustion sensor structured to produce a phasing signal indicative of a phasing of combustion of gaseous fuel in a cylinder in the dual fuel engine system operated in a gaseous fuel spark-ignited mode;
• a combustion control unit coupled to the combustion sensor, the combustion control unit being structured to adjust a phasing control parameter, based on the phasing signal;
• the combustion control unit being further structured to switch the cylinder from operating in the gaseous fuel spark-ignited mode to operating in a dual fuel liquid pilot-ignited mode based on the adjustment to the phasing control parameter at least in part by:
• commanding direct injection of an early pilot shot of liquid fuel into the cylinder and production of a spark to ignite gaseous fuel in the cylinder in a first engine cycle;
• and
• commanding direct injection of an early pilot shot and a second pilot shot of liquid fuel into the cylinder to ignite gaseous fuel in the cylinder in a second engine cycle occurring after the first engine cycle.

A method of operating a dual fuel engine system comprising:

• operating a cylinder in the dual fuel engine system in a gaseous fuel spark-ignited mode to ignite gaseous fuel in the cylinder in response to production of a spark;
• operating the cylinder in the dual fuel engine system in a dual fuel liquid pilot-ignited mode to ignite gaseous fuel in the cylinder in response to combustion of an early pilot shot and a second pilot shot of directly injected liquid fuel without production of a spark;
• limiting an error in a phasing of combustion in the cylinder in the gaseous fuel spark-ignited mode by adjusting a phasing control parameter;
• triggering switching the cylinder from the gaseous fuel spark-ignited mode to the dual fuel liquid pilot-ignited mode based on the adjustment to the phasing control parameter;
• and
• igniting gaseous fuel in the cylinder in response to combustion of a directly injected early pilot shot of liquid fuel and production of a spark during the switching of the cylinder from the gaseous fuel spark-ignited mode to the dual fuel liquid pilot-ignited mode.