Method for combusting a fuel, and combustion appliance

Abstract

A method for combusting a fuel includes, providing an oxidizer mass flow, providing a first oxidizer partial mass flow, combusting a fuel in the first oxidizer partial mass flow thus providing a mass flow of combustion products, providing the mass flow of combustion products to a duct, and ducting the mass flow of combustion products through the duct in a flow direction. A flow of a first supplementary fluid which is essentially aligned with the flow of combustion products is selectively provided as one of an oxidizer and a premixed fuel/oxidizer mixture. A further mass flow is discharged laterally offset with respect to a discharged mass flow of first supplementary fluid and across the flow cross section of the duct, to provide mass flows of supplementary fluids as laterally stratified layers of the respective supplementary fluids.

1 . A method for combusting a fuel, the method comprising:
 providing an oxidizer mass flow;   providing a first oxidizer partial mass flow;   combusting a fuel in the first oxidizer partial mass flow thus providing a mass flow of combustion products;   providing the mass flow of combustion products to a duct, and ducting the mass flow of combustion products through said duct in a flow direction, discharging a mass flow of a first supplementary fluid into said duct; and   discharging the mass flow of the first supplementary fluid in a discharge direction essentially aligned with the flow direction such as to provide a flow of the first supplementary fluid essentially aligned with the flow of combustion products, wherein the first supplementary fluid is selectively provided as one of an oxidizer and a premixed fuel/oxidizer mixture.   
     
     
         2 . The method according to  claim 1 , comprising:
 discharging at least one further mass flow of a further supplementary fluid into the duct, wherein the further supplementary fluid is selectively provided as one of an oxidizer and a premixed fuel/oxidizer mixtureg;   discharging the at least one further mass flow essentially aligned with the flow direction; and   wherein the at least one further mass flow is discharged laterally offset with respect to the discharged mass flow of first supplementary fluid and across a flow cross section of the duct, such as to provide the mass flows of supplementary fluids as laterally stratified layers of the respective supplementary fluids.   
     
     
         3 . The method according to the  claim 2 , comprising:
 discharging at least two further mass flows of further supplementary fluids, wherein each further mass flow is discharged with a different lateral offset with respect to the flow of the first supplementary fluid and across the flow cross section of the duct, such as to provide the mass flows of supplementary fluids as laterally stratified layers of the respective supplementary fluid.   
     
     
         4 . The method according to  claim 3 , comprising:
 providing each layer of further supplementary fluid laterally adjacent at least one other layer of supplementary fluid.   
     
     
         5 . The method according  claim 1 , wherein the discharge of at least one further mass flow of a further supplementary fluid comprises:
 discharging each mass flow of supplementary fluid at a different location along the flow direction.   
     
     
         6 . The method according to  claim 1 , performed in a combustion appliance and comprising:
 operating the combustion appliance at different thermal loads;   providing each mass flow of a supplementary fluid as a mass flow of oxidizer when the combustion appliance is operated at or below a first threshold value of a thermal load parameter; and   providing the mass flow of at least one supplementary fluid as a premixed fuel/oxidizer mass flow when the combustion appliance is operated above the first threshold value of the thermal load parameter.   
     
     
         7 . The method according to  claim 1 , comprising:
 providing a supplementary fluid as oxidant when the combustion appliance is operated at or below a respective threshold value of a load parameter; and   providing the supplementary fluid as a premixed fuel/oxidizer mixture when the combustion appliance is operated above a respective threshold value of the load parameter, such that a number of supplementary fluids which are provided as a premixed fuel/oxidizer mixture increases stepwise with increasing thermal load at which the combustion appliance is operated and decreases with a decreasing thermal load at which the appliance is operated.   
     
     
         8 . The method according to  claim 1 , comprising:
 choosing a respective threshold value of the load parameter higher the further downstream of the flow of combustion products the respective supplementary fluid is discharged.   
     
     
         9 . The method according to  claim 1 , performed as a combustion of fuel in a gas turbine engine, the method being comprising:
 operating the gas turbine engine at different loads of the gas turbine engine;   providing each of the mass flows of a supplementary fluid as a mass flow of oxidizer when the gas turbine engine is operated at or below a first threshold value of a load parameter of the gas turbine engine; and   providing the mass flow of at least one supplementary fluid as a premixed fuel/oxidizer mass flow when the gas turbine engine is operated above the first threshold value of the load parameter of the gas turbine engine.   
     
     
         10 . The method according to  claim 9 , comprising:
 providing a supplementary fluid as oxidant when the gas turbine engine is operated at or below a respective threshold value of a load parameter of the gas turbine engine; and   providing the supplementary fluid as a premixed fuel/oxidizer mixture when the gas turbine engine is operated above the respective threshold value of the load parameter of the gas turbine engine, such that a number of supplementary fluids which are provided as a premixed fuel/oxidizer mixture increases stepwise with increasing load of the gas turbine engine and decreases with a decreasing load of the gas turbine engine.   
     
     
         11 . The method according to  claim 1 , comprising:
 choosing a respective threshold value of the load parameter of the gas turbine engine higher the further downstream of the flow of combustion products the respective supplementary fluid is discharged.   
     
     
         12 . A combustion appliance, comprising:
 a first combustion stage;   a duct provided to receive combustion products from the first combustion stage; and   a fuel/oxidizer premix device, the fuel/oxidizer premix device, at a discharge end thereof, being in fluid communication with a discharge appliance provided in the duct, wherein the discharge appliance is arranged and configured to discharge a fluid received from the fuel/oxidizer premix device into a flow of combustion products in the duct and essentially aligned with a flow direction of the flow of combustion products.   
     
     
         13 . The combustion appliance according to  claim 12 , comprising:
 at least one further fuel/oxidizer premix device, wherein the further fuel/oxidizer premix device, at a discharge end thereof, is in fluid communication with a further discharge appliance provided in the duct, wherein the further discharge appliance is arranged and configured to discharge a fluid received from the further fuel/oxidizer premix device into a flow of combustion products in the duct and essentially aligned with a flow direction of the flow of combustion products, wherein each discharge appliance is disposed and configured to discharge the respective fluid laterally offset with respect to the fluid discharged from each other discharge appliance in a throughflow cross section of the duct, such that discharge flows from the discharge appliances will be provided without an overlap in a throughflow cross section of the duct.   
     
     
         14 . The combustion appliance according to  claim 13 , wherein the discharge appliances which are in fluid communication with different fuel/oxidizer premix devices are provided in the duct with a mutual offset in a throughflow direction of the duct. 
     
     
         15 . A gas turbine engine comprising:
 at least one combustion appliance as claimed in  claim 12 , wherein the at least one fluid discharge device is provided adjacent and upstream an expansion turbine inlet.