Gas turbine combustor of the completely premixed combustion type

A gas turbine combustor of the completely premixed combustion type comprising a combustion chamber;

• a plurality of spaced main nozzles provided in an end wall of said combustion chamber and defining an upstream side of said combustion chamber;
• an annular auxiliary nozzle formed around each of said main nozzles, the main nozzles being grouped into at least first, second and third groups;
• first means for supplying to the main nozzles of each of the groups of main nozzles a pre-mixed fuel-air gas mixture having a mixing ratio of the fuel and the air wherein the proportion of air is larger than a stoichiometric air requirement for combustion of the fuel in the mixture;
• second means for supplying to said auxiliary nozzles a pre-mixed fuel-air gas mixture having a mixing ratio of the fuel and the air wherein the proportion of air is smaller than that supplied by said first means for supplying;
• and
• control means for controlling said first means for supplying for progressively increasing the number of said groups of main nozzles to which a pre-mixed fuel-air gas mixture is supplied with an increase of load on the gas turbine combustor, wherein said control means controls said first means for supplying such that initially a first air stoichiometric ratio of the pre-mixed fuel-air gas mixture is supplied to the first group of said main nozzles and when the ratio is approximately 1.25 said control means starts operation of the second group of the main nozzles by causing said first means for supplying to supply a pre-mixed fuel-air gas mixture to the main nozzles of the second group.