Gas turbine combustor

Abstract

A gas turbine combustor is improved to enhance a cooling effect and a flame holding ability to thereby reduce NOx generation. A combustor 13 comprises a double structure of an inner cylindrical member 13 a and an enlarged outer cylindrical member 13 b to thereby enlarge a diameter of a combustion zone. A pre-mixing nozzle 11 comprises an outer sleeve 23 of which front end is projected beyond a base plate 17 and a pre-mixing nozzle portion 21 of the inner side. Air flows between the outer sleeve 23 and the pre-mixing nozzle portion 21 for enhancing the cooling effect of the pre-mixing nozzle 11. High temperature gas inner and outer circulating flows 15, 16 are formed in the combustion zone to enhance the flame holding ability. Pilot fuel quantity, as so far necessitated for flame holding, is reduced and NOx quantity generated of the pilot fuel is reduced. The base plate 17 exposed to the high temperature gas is prevented from being overheated by the projected front portion of the pre-mixing nozzle 11.

What is claimed is:  
     
         1 . A gas turbine combustor comprising a pilot nozzle arranged on a central axis of said combustor and a plurality of pre-mixing nozzles arranged around said pilot nozzle, wherein a diameter of a combustion zone of said combustor is set such that, where an area is taken on a radial directional plane of said combustor, the area inside of said combustion zone and outside of a pitch circle that is defined as a circle on which all central axes of said plurality of pre-mixing nozzles are arranged, less the area taken by said plurality of pre-mixing nozzles outside of said pitch circle, is a half or more of the area of all of said plurality of pre-mixing nozzles.  
     
     
         2 . A gas turbine combustor as claimed in  claim 1 , wherein each of said plurality of pre-mixing nozzles has its front end projected beyond a base plate that supports said pre-mixing nozzle and a projecting distance of such projected front end is set to one third or more of an outer diameter of said pre-mixing nozzle.  
     
     
         3 . A gas turbine combustor as claimed in  claim 1 , wherein each of said plurality of pre-mixing nozzles has its front portion made in a double structure having inner and outer members with a predetermined gap being maintained between said inner and outer members and air is flowable in said gap.  
     
     
         4 . A gas turbine combustor as claimed in  claim 1 , wherein a combustor body as an outer casing of said combustor comprises therein an inner cylindrical member and an outer cylindrical member, said inner cylindrical member is arranged surrounding said plurality of pre-mixing nozzles and said outer cylindrical member has its inner diameter made larger than an outer diameter of said inner cylindrical member and is arranged surrounding a front end portion of said inner cylindrical member and extending downstream of said inner cylindrical member so as to cover said combustion zone to thereby enable to enlarge the diameter of said combustion zone beyond an inner diameter of said inner cylindrical member.