Method and apparatus for controlling combustion quality of a gaseous-fuelled internal combustion engine

A method of operating a gaseous-fuelled internal combustion engine, said method comprising:

• (a) determining a target heat release rate (HRR) for a current cycle of said internal combustion engine;
• (b) comparing characteristics of said target HRR to selected characteristics of a trace indicative of an actual HRR for said cycle determined from a previous cycle of said internal combustion engine;
• (c) during said cycle of said internal combustion engine:
• (i) directing an intake charge into said combustion chamber defined in said engine;
• (ii) compressing said intake charge within said combustion chamber;
• (iii) introducing at least one gaseous fuel into said combustion chamber;
• (iv) introducing a quantity of a pilot fuel into said combustion chamber at a pilot fuel timing, said pilot fuel capable of auto-igniting at a first crank angle when a piston is near or at top dead center within said combustion chamber near completion of a compression stroke during said cycle, said combustion chamber partially defined by said piston;
• (v) actuating an HRR control lever to reduce differences between said characteristics of said trace and said characteristics of said target HRR, said HRR control lever comprising at least one of said pilot fuel timing and said quantity of said pilot fuel;
• (vi) burning said gaseous fuel and said pilot fuel, said gaseous fuel ignited as a result of combustion of said pilot fuel.