Injector for Liquid Fuel, and Staged Premix Burner Having This Injector

Abstract

An injector ( 4 ) for liquid fuel ( 6 a ) and a premix burner, in particular for combustion chambers of gas turbines which burner includes an injector ( 4 ) of this type, includes a swirl nozzle ( 14 ) which is surrounded by a shielding-air passage ( 11 ) and has an enlarged cross section of flow in the region of a nozzle-internal swirl generator ( 12 ) for the liquid fuel ( 6 a ), with this enlarged cross section of flow being reduced again toward an exit opening of the swirl nozzle ( 14 ). The injector allows the premix burner to operate with a reduced admission pressure and a high atomization quality.

1 . An injector for liquid fuel, comprising: 
 a swirl nozzle configured and arranged for injecting liquid fuel, the swirl nozzle including an internal swirl generator and being surrounded by a shielding-air passage for shielding air and having an enlarged cross section of flow in the region of said internal swirl generator for liquid fuel, the enlarged cross section of flow including a reduced portion toward an exit opening of the swirl nozzle.    
   
   
       2 . The injector as claimed in  claim 1 , wherein the internal swirl generator comprises a swirl grate.  
   
   
       3 . The injector as claimed in  claim 2 , further comprising: 
 a central swirl body; and    wherein the swirl grate extends around the central swirl body.    
   
   
       4 . The injector as claimed in  claim 1 , wherein the internal swirl generator is a first internal swirl generator, and further comprising: 
 a second internal swirl generator arranged in the shielding-air passage.    
   
   
       5 . The injector as claimed in  claim 4 , wherein the second internal swirl generator and the first internal swirl generator are configured and arranged to generate oppositely directed swirls.  
   
   
       6 . The injector as claimed in  claim 1 , wherein the injector is configured and arranged so that the liquid fuel and the shielding air emerge from the injector with approximately parallel directions of flow.  
   
   
       7 . The injector as claimed in  claim 6 , further comprising: 
 an exit;    boundary walls defining said shielding-air passage;    wherein the swirl nozzle comprises boundary walls; and    wherein the swirl nozzle boundary walls and the shielding-air passage boundary walls run approximately parallel at the injector exit.    
   
   
       8 . The injector as claimed in  claim 1 , further comprising: 
 an exit;    wherein the shielding-air passage is configured and arranged at the injector exit so that the shielding air emerges at an angle with respect to the direction in which the liquid fuel emerges, to exert shearing forces on the liquid fuel.    
   
   
       9 . The injector as claimed in  claim 1 , further comprising: 
 an outer casing, the swirl nozzle and the outer casing in combination forming the shielding-air passage, the swirl nozzle and the outer casing configured and arranged to be axially displaceable with respect to one another.    
   
   
       10 . A staged premix burner comprising: 
 a swirl generator for a combustion air stream;    fuel exit openings with feeds oriented for the staged introduction of gaseous fuel into the combustion air stream; and    a central carrier including an injector with a swirl nozzle for the injection of liquid fuel and a shielding-air passage for shielding air, the swirl nozzle including an exit and an internal swirl generator and being surrounded by the shielding-air passage and having an enlarged cross section of flow in the region of the internal swirl generator for liquid fuel, the enlarged cross section of flow including a reduced portion toward the swirl nozzle exit.    
   
   
       11 . The premix burner as claimed in  claim 10 , wherein some of the fuel exit openings for introducing gaseous fuel into the combustion air stream are formed in a part of the central carrier upstream of the injector.  
   
   
       12 . The premix burner as claimed in  claim 10 , wherein the internal swirl generator comprises a plurality of part-shells which surround a premix space in the shape of a cone envelope and between which air entry slots are formed.  
   
   
       13 . The premix burner as claimed in  claim 12 , wherein at least some of the fuel exit openings for introducing gaseous fuel into the combustion air stream are arranged in the region of the air entry slots.  
   
   
       14 . The premix burner as claimed in  claim 10 , wherein the internal swirl generator comprises a swirl grate.  
   
   
       15 . The premix burner as claimed in  claim 14 , further comprising: 
 a central swirl body; and    wherein the swirl grate extends around the central swirl body.    
   
   
       16 . The premix burner as claimed in  claim 10 , wherein the internal swirl generator is a first internal swirl generator, and further comprising: 
 a second internal swirl generator arranged in the shielding-air passage.    
   
   
       17 . The premix burner as claimed in  claim 16 , wherein the second internal swirl generator and the first internal swirl generator are configured and arranged to generate oppositely directed swirls.  
   
   
       18 . The premix burner as claimed in  claim 10 , wherein the injector is configured and arranged so that liquid fuel and shielding air emerge from the injector with approximately parallel directions of flow in the axial direction of the carrier.  
   
   
       19 . The premix burner as claimed in  claim 18 , further comprising: 
 an injector exit;    boundary walls defining said shielding-air passage;    wherein the swirl nozzle comprises boundary walls; and    wherein the shielding-air passage boundary walls and the swirl nozzle boundary walls run approximately coaxially at the injector exit.    
   
   
       20 . The premix burner as claimed in  claim 10 , wherein the injector comprises an exit; and 
 wherein the shielding-air passage is configured and arranged at an exit of the injector so that the shielding air emerges at an angle with respect to the direction in which liquid fuel emerges, to exert shearing forces on the liquid fuel.    
   
   
       21 . The premix burner as claimed in  claim 10 , further comprising: 
 an outer casing;    wherein the swirl nozzle and the outer casing in combination form the shielding-air passage, the swirl nozzle and the outer casing arranged to be axially displaceable with respect to one another.    
   
   
       22 . A gas turbine comprising a staged premix burner as claimed in  claim 1.