Mixer

Abstract

A mixer having a housing, a duct within the housing, a first and a second injector arranged to inject a fluid at a centre zone of the duct, a third and a fourth injector arranged to inject the fluid at a wall zone of the duct. The first/third injectors are at a distance D1=v/2f1 or odd integer multiples of it from the second/fourth injectors in the absence of an acoustic node between them, or at a distance D1=λconv=v/f1 or full wave length integer multiples of it in the presence of an acoustic node between them. Advantageously f1 is greater than f2.

1 . A mixer comprising:
 a housing;   a duct within the housing;   a first injector and a second injector arranged to inject a fluid at a centre zone of the duct;   a third injector and a fourth injector arranged to inject the fluid at a wall zone of the duct, wherein:   the first injector is at a distance D 1 =v/2f 1  or odd integer multiples of it from the second injector in an absence of an acoustic node between the second injector and the first injector, or at a distance D 1 =λ conv =v/f 1  or full wave length integer multiples of it in a presence of an acoustic node between the second injector and the first injector; and   the third injector is at a distance D 2 =v/2f 2  or odd integer multiples of it from the fourth injector in an absence of an acoustic node between the third injector and the first injector, or at a distance D 2 =v/f 2  from the first injector in a presence of an acoustic node between the third injector and the first injector;   wherein:   f 1  is an oscillating frequency to be damped at the wall zone of the duct;   f 2  is an oscillating frequency to be damped at the centre zone of the duct; and   v is a fluid flow speed through the duct, wherein f 1  is greater than f 2 .   
     
     
         2 . The mixer of  claim 1 , wherein both f 1  and f 2  are lower than 150 Hz. 
     
     
         3 . The mixer of  claim 1 , wherein the first injector and/or the second injector and/or the third injector and/or the fourth injector comprise:
 a plurality of rows of nozzles close to one another.   
     
     
         4 . The mixer of  claim 2 , wherein nozzles of different rows of nozzles of a same injector have different penetration. 
     
     
         5 . The mixer of  claim 2 , wherein the nozzles of a same row of nozzles have different penetration. 
     
     
         6 . A gas turbine comprising:
 a compressor;   a first combustion chamber;   a second combustion chamber arranged to be fed with a fluid coming from the first combustion chamber; and   a turbine, wherein between the first combustion chamber and the second combustion chamber a mixer is provided, which mixer includes:   a housing;   a duct within the housing;   a first injector and a second injector arranged to inject a fluid at a centre zone of the duct;   a third injector and a fourth injector arranged to inject the fluid at a wall zone of the duct, wherein:   the first injector is at a distance D 1 =v/2f 1  or odd integer multiples of it from the second injector in an absence of an acoustic node between the second injector and the first injector, or at a distance D 1 =λ conv =v/f 1  or full wave length integer multiples of it in a presence of an acoustic node between the second injector and the first injector; and   the third injector is at a distance D 2 =v/2f 2  or odd integer multiples of it from the fourth injector in an absence of an acoustic node between the third injector and the first injector, or at a distance D 2 =v/f 2  from the first injector in a presence of an acoustic node between the third injector and the first injector;   wherein:   f 1  is an oscillating frequency to be damped at the wall zone of the duct;   f 2  is an oscillating frequency to be damped at the centre zone of the duct; and   v is a fluid flow speed through the duct, wherein f 1  is greater than f 2 .