Patent ID: 7302939

Claim:
A method of operating a gaseous-fuelled internal combustion engine, said method comprising: during a cycle of said engine: (a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine, (b) compressing said intake charge within said combustion chamber, (c) injecting a directly injected gaseous fuel into said compressed intake charge within said combustion chamber at a pressure above 12 MPa, (d) igniting said directly injected gaseous fuel, (e) burning said directly injected gaseous fuel, (f) directing exhaust gas produced during burning of said directly injected gaseous fuel from said combustion chamber into an exhaust line, wherein a quantity of said exhaust gas from said exhaust line is directed through an EGR line to said intake line and, during a subsequent cycle of said engine, a subsequent intake charge comprises said quantity of said exhaust gas; and wherein said quantity of said exhaust gas is dependent on at least one of: (1) a target NOx concentration resulting from burning said directly injected gaseous fuel, and (2) said pressure.