Gas turbine combustor with nozzle pressure ratio control

A gas turbine combustor for a gas turbine power plant comprising:

• a combustion liner operatively connected to a turbine, said combustion liner being provided with a main fuel nozzle assembly and a sub-fuel nozzle assembly having nozzle holes for injecting fuel to an inside of the combustion liner through said nozzle holes;
• a base fuel supply line having one end connected to a fuel source;
• a main fuel line extending from said base fuel supply line for supplying a fuel from the base fuel line to the main fuel nozzle assembly and injecting the fuel through the nozzle hole of the main fuel nozzle assembly into a premixing assembly where the fuel is premixed with air and supplied to said combustion liner for permitting a lean-burning in the combustion liner;
• a plurality of sub-fuel lines extending from said base fuel supply line for supplying the fuel from the base fuel supply line to the sub-fuel nozzle assembly for mixing the fuel with a combustion air in said combustion liner so as to permit a diffusion burning in the combustion liner, wherein said main and sub-fuel lines branch from the base fuel supply line;
• distributing valve means provided in the main fuel line and at least one of the sub-fuel lines for distributing the fuel into the main and sub-fuel lines;
• and
• a control unit for controlling an opening amount of the distributing valve means so as to control a fuel flow through said distributing valve means and thereby control a fuel distribution ratio to the main and sub-fuel lines;
• wherein a fixed orifice is provided in an other one of said sub-fuel lines which maintains a fuel flow through said other one of the sub-fuel lines.