Combustors with improved dynamics

Abstract

A combustor comprises an outer combustor casing defining a plurality of circumferentially adjoining combustion chambers. Each combustion chamber comprises a dome at an upstream end and an outlet at a downstream end. A plurality of pre-mixers are joined to the combustor dome of each respective combustion chamber. The pre-mixers comprise a duct having an inlet at one end for receiving compressed air, an outlet at an opposite end disposed in flow communication with the combustion chamber and a swirler disposed in the duct adjacent the duct inlet for swirling air channeled therethrough. A fuel injector is provided for injecting fuel into the pre-mixer ducts and for mixing with the air in the ducts for flow into the combustion chamber to generate a combustion flame at the duct outlets. A portion of the pre-mixers comprise an altered flameholding capability so as to distribute the resulting combustion flames from the respective portion of the pre-mixers axially downstream with respect to the non-altered pre-mixers so as to reduce the dynamic pressure amplitude of the combustion flames.

What is claimed is:  
     
         1 . A combustor comprising: 
 an outer combustor casing defining a plurality of circumferentially adjoining combustion chambers, each combustion chamber comprising a dome at an upstream end and an outlet at a downstream end;    a plurality of pre-mixers joined to said combustor dome of each respective combustion chamber, said pre-mixers comprising a duct having an inlet at one end for receiving compressed air, an outlet at an opposite end disposed in flow communication with said combustion chamber and a swirler disposed in said duct adjacent said duct inlet for swirling air channeled therethrough; and    a fuel injector for injecting fuel into said pre-mixer ducts and for mixing with said air in said ducts for flow into said combustion chamber to generate a combustion flame at said duct outlets;    wherein a portion of said pre-mixers comprise an altered flameholding capability so as to distribute said resulting combustion flames from said respective portion of said pre-mixers axially downstream with respect to said non-altered pre-mixers to reduce the dynamic pressure amplitude of said combustion flames.    
     
     
         2 . A combustor, in accordance with    claim 1   , wherein said pre-mixers comprising an altered flameholding capability comprise at least one orifice for directing high velocity air to impinge upon said combustion flames so as to lift said respective combustion flames from said dome end and shift said combustion flames axially downstream.  
     
     
         3 . A combustor, in accordance with    claim 2   , wherein the velocity of said high velocity air is great enough to overcome the flame propagation speed.  
     
     
         4 . A combustor, in accordance with    claim 2   , wherein said high velocity air is supplied directly to said respective orifices from a high-pressure air source.  
     
     
         5 . A combustor, in accordance with    claim 2   , wherein said high velocity air is supplied passively into said respective orifices by providing fluid communication between said respective orifices and a high-pressure region of a turbine engine.  
     
     
         6 . A combustor, in accordance with    claim 2   , wherein said combustion flames are shifted axially downstream so as to be axially positioned proximate a pressure node source to minimize Rayleigh's Criteria.  
     
     
         7 . A combustor, in accordance with    claim 4   , wherein said high velocity air supplied from said high-pressure air source is manipulated so as to tune said combustion chamber for minimum combustion instability.  
     
     
         8 . A combustor, in accordance with    claim 1   , wherein said pre-mixers comprising altered flameholding capability comprise swirlers with a manipulated angle profile of said swirler blades so as to support longer narrower flames when compared to said non-altered pre-mixers to de-couple said combustion flames from maximum pressures located at said dome end.  
     
     
         9 . A combustor, in accordance with    claim 8   , wherein the swirl angle of said swirl blades is in the range between about 15% to about 50% smaller than the swirl angle of a non-manipulated swirler.  
     
     
         10 . A combustor comprising: 
 an outer combustor casing defining a plurality of circumferentially adjoining combustion chambers, each combustion chamber comprising a dome at an upstream end and an outlet at a downstream end;    a plurality of pre-mixers joined to said combustor dome of each respective combustion chamber, said pre-mixers comprising a duct having an inlet at one end for receiving compressed air, an outlet at an opposite end disposed in flow communication with said combustion chamber and a swirler disposed in said duct adjacent said duct inlet for swirling air channeled therethrough; and    a fuel injector for injecting fuel into said pre-mixer ducts and for mixing with said air in said ducts for flow into said combustion chamber to generate a combustion flame at said duct outlets; and    a plurality of flameholders positioned axially downstream from said dome and proximate a pressure node so as to minimize Rayleigh's criteria.    
     
     
         11 . A combustor, in accordance with    claim 8   , wherein said flameholders are selected from the group consisting of gutters, v-gutters, rounded-nose gutters and jet curtain flameholders.  
     
     
         12 . A combustor, in accordance with    claim 10   , wherein said pre-mixers include at least one orifice for directing high velocity air so as to impinge upon said combustion flames to lift said respective combustion flames from said dome end and shift said combustion flames axially downstream.  
     
     
         13 . A combustor, in accordance with    claim 10   , wherein said combustor is configured such that the reaction zone is concentrated at a toroidal shape centered about a nodal circle so as to minimize a fundamental transverse radial standing wave resonance  
     
     
         14 . An industrial gas turbine including a combustor comprising: 
 an outer combustor casing defining a plurality of circumferentially adjoining combustion chambers, each combustion chamber comprising a dome at an upstream end and an outlet at a downstream end;    a plurality of pre-mixers joined to said combustor dome of each respective combustion chamber, said pre-mixers comprising a duct having an inlet at one end for receiving compressed air, an outlet at an opposite end disposed in flow communication with said combustion chamber and a swirler disposed in said duct adjacent said duct inlet for swirling air channeled therethrough; and    a fuel injector for injecting fuel into said pre-mixer ducts and for mixing with said air in said ducts for flow into said combustion chamber to generate a combustion flame at said duct outlets;    wherein a portion of said pre-mixers comprise an altered flameholding capability so as to distribute said resulting combustion flames from said respective portion of said pre-mixers axially downstream with respect to said non-altered pre-mixers to reduce the dynamic pressure amplitude of said combustion flames.    
     
     
         15 . An industrial gas turbine, in accordance with    claim 14   , wherein said pre-mixers comprising an altered flameholding capability comprise at least one orifice for directing high velocity air to impinge upon said combustion flames so as to lift said respective combustion flames from said dome end and shift said combustion flames axially downstream.  
     
     
         16 . An industrial gas turbine, in accordance with    claim 15   , wherein said combustion flames are shifted axially downstream so as to be axially positioned proximate a pressure node source to minimize Rayleigh's Criteria.  
     
     
         17 . An industrial gas turbine, in accordance with    claim 2   , wherein said high velocity air supplied from said high-pressure air source is manipulated so as to tune said combustion chamber for minimum combustion instability.  
     
     
         18 . An industrial gas turbine, in accordance with    claim 14   , wherein said pre-mixers comprising altered flameholding capability comprise swirlers with a manipulated angle profile of said swirler blades so as to support longer narrower flames when compared to said non-altered pre-mixers to de-couple said combustion flames from maximum pressures located at said dome end.  
     
     
         19 . An industrial gas turbine, in accordance with    claim 18   , wherein the swirl angle of said swirl blades is in the range between about 15% to about 50% smaller than the swirl angle of a non-manipulated swirler.  
     
     
         20 . An industrial gas turbine having a combustor comprising: 
 an outer combustor casing defining a plurality of circumferentially adjoining combustion chambers, each combustion chamber comprising a dome at an upstream end and an outlet at a downstream end;    a plurality of pre-mixers joined to said combustor dome of each respective combustion chamber, said pre-mixers comprising a duct having an inlet at one end for receiving compressed air, an outlet at an opposite end disposed in flow communication with said combustion chamber and a swirler disposed in said duct adjacent said duct inlet for swirling air channeled therethrough; and    a fuel injector for injecting fuel into said pre-mixer ducts and for mixing with said air in said ducts for flow into said combustion chamber to generate a combustion flame at said duct outlets; and    a plurality of flameholders positioned axially downstream from said dome and proximate a pressure node so as to minimize Rayleigh's criteria.    
     
     
         21 . An industrial gas turbine, in accordance with    claim 20   , wherein said pre-mixers comprise at least one orifice for directing high velocity air to impinge upon said combustion flames so as to lift said respective combustion flames from said dome end and shift said combustion flames axially downstream.  
     
     
         22 . An industrial gas turbine, in accordance with    claim 20   , wherein said combustor is configured such that the reaction zone is concentrated at a toroidal shape centered about a nodal circle so as to minimize a fundamental transverse radial standing wave resonance