1.  Field of the Invention
The present invention relates to a gas turbine combustor and an operating method thereof. 
2.  Description of Prior Art
The present invention specifically relates to a low NOx type gas turbine combustor which emits low levels of nitrogen oxides.  The prior art has been disclosed in Japanese Application Patent Laid-Open Publication No.  Hei 05-172331. 
In a gas turbine combustor, since the turndown ratio from startup to the rated load condition is large, a diffusion combustion system which directly injects fuel into a combustion chamber has been widely employed so as to ensure combustion stability in a wide area.  Also, a premixed combustion system has been made available. 
In said prior art technology, a diffusion combustion system has a problem of high level NOx.  A premixed combustion system also has problems of combustion stability, such as flash back, and flame stabilization during the startup operation and partial loading operation.  In actual operation, it is preferable to simultaneously solve those problems. 
The main purpose of the present invention is to provide a gas turbine combustor having low level NOx emission and good combustion stability and an operating method thereof. 
The present invention provides a gas turbine combustor having a combustion chamber into which fuel and air are supplied, wherein the fuel and the air are supplied into said combustion chamber as a plurality of coaxial jets. 
Further, a method of operating a gas turbine combustor according to the present invention is the method of operating a gas turbine combustor having a combustion chamber into which fuel and air are supplied, wherein the fuel and the air are supplied into said combustion chamber as a plurality of coaxial jets.