Burner with high flame stability

Abstract

The invention relates to a premix burner with high flame stability for use in a heat producer, preferably in the combustion chamber of a gas turbine. Modern lean operated premix burners make possible very low pollutant emissions, but sometimes operate very close to the extinction limit. To increase the stability of the lean premix combustion by increasing the distance between the flame temperature and the extinction limit temperature, it is proposed according to the invention to arrange a downstream combustion gas mixing section ( 300 ) for the burner, which mixing section ( 300 ) projects at least partially into the combustion chamber ( 50 ) and enables combustion gases from the combustion chamber ( 50 ) access to the fuel/air mixture ( 144 ) by means of combustion gas inlet openings ( 311 ). The added combustion gases ( 145 ) are mixed with the fuel/air mixture ( 144 ), and in this manner increase its temperature. This increase in temperature results in a significant increase in the flame speed, as a consequence of which the extent of the flame front ( 123 ) and the extinction limit temperature of the burner decrease.

What is claimed is:  
     
         1 . Process for the combustion of gaseous and/or liquid fuels in lean premix burners, wherein the fuel/air mixture is preheated before ignition.  
     
     
         2 . Process according to  claim 1 , wherein the fuel/air mixture is mixed with an amount of combustion gas before ignition.  
     
     
         3 . Process according to  claim 2 , wherein an amount of combustion gas in a mass fraction of 5% to 60% is admixed to the fuel/air mixture.  
     
     
         4 . Process according to  claim 2 , wherein an amount of combustion gas directly out of the combustion chamber is admixed to the fuel/air mixture.  
     
     
         5 . Process according to  claim 4 , wherein the flowing fuel/air mixture sucks in an amount of combustion gas directly out of the combustion chamber.  
     
     
         6 . Process according to  claim 5 , wherein the fuel/air mixture flows in a swirl flow through a mixing section projecting into a combustion chamber, and sucks in combustion gases from the combustion chamber up-stream of the mouth of this mixing section.  
     
     
         7 . Process according to  claim 6 , wherein the combustion gases are sucked in by means of inlet apertures in the housing jacket of the mixing section.  
     
     
         8 . Process according to  claim 1 , wherein it is applied to the operation of lean premixed burners of a gas turbine plant.