Air injection systems for combustion chambers

Abstract

A combustion system comprises a combustion chamber and a flue gas duct located downstream of the combustion chamber to receive combustion products from the combustion chamber, the combustion chamber has a base and an enclosing wall connecting the base to the flue gas duct. The combustion chamber is provided with a plurality of combustion devices, the combustion devices being configured to deliver fuel and gas and/or air into the combustion chamber so as to generate a fireball within a combustion zone in the combustion chamber, the combustion devices further being configured such that the generated fireball rotates about an axis extending between the base and the flue duct. A secondary gas and/or air nozzle is provided in the base of the combustion chamber, at a location upstream of the combustion zone, the nozzle being for delivering gas and/or air into the combustion zone in a direction towards the flue duct.

1 . A combustion system comprising a combustion chamber and a flue gas duct located downstream of the combustion chamber to receive combustion products from the combustion chamber,
 the combustion chamber having a base and an enclosing wall connecting the base to the flue gas duct,   the combustion chamber being provided with a plurality of combustion devices, the combustion devices being configured to deliver fuel and gas and/or air into the combustion chamber so as to generate a fireball within a combustion zone in the combustion chamber, the combustion devices further being configured such that the generated fireball rotates about an axis extending between the base and the flue duct,   wherein the system further comprises a secondary gas and/or air nozzle at a location upstream of the combustion zone, the nozzle being for delivering gas and/or air into the combustion zone in a direction towards the flue duct.   
     
     
         2 . A combustion system according to  claim 1 , wherein the base of the combustion chamber comprises two panels that are inclined towards each other in a direction away from the flue gas duct. 
     
     
         3 . A combustion system according to  claim 2 , wherein the secondary gas nozzle is provided in one of the two panels, and a further secondary gas nozzle is provided in the other of the two panels, the gas nozzle and the further gas nozzle preferably being located in opposing positions. 
     
     
         4 . A combustion system according to  claim 2 , wherein the distance between the nozzle and the upstream extremity of the base is less than 3 metres. 
     
     
         5 . A combustion system according to  claim 1 , wherein the system is arranged to supply gas to the combustion devices and the secondary gas nozzle from the same source. 
     
     
         6 . A combustion system according to  claim 5 , wherein the gas supplied to the combustion devices and the secondary gas nozzle is pressurised by the same fan. 
     
     
         7 . A combustion system according to  claim 1 , wherein the secondary gas nozzle is configured to allow gas to be directed through the centre of the fireball, along its axis of rotation. 
     
     
         8 . A method of operating a combustion system according to  claim 1 , the method comprising the step of delivering fuel and gas into the combustion chamber by means of the combustion devices to generate a fireball having a stoichiometry less than 0.9. 
     
     
         9 . A method of operating a combustion system according to  claim 1 , comprising the step of delivering gas into the combustion chamber via the secondary gas nozzle at a velocity of 40-70 m/s. 
     
     
         10 . A combustion system comprising a combustion chamber and a flue gas duct located downstream of the combustion chamber to receive combustion products from the combustion chamber,
 the combustion chamber having a base and an enclosing wall connecting the base to the flue gas duct,   the combustion chamber being provided with a plurality of combustion devices, the combustion devices being configured to deliver fuel and gas into the combustion chamber so as to generate a fireball within a combustion zone in the combustion chamber, the combustion devices further being configured such that the generated fireball rotates about an axis extending between the base and the flue duct,   wherein a plurality of secondary gas nozzles is provided at a location upstream of the combustion zone, the plurality of secondary gas nozzles being configured to deliver gas into the combustion chamber so as to create a gas stream that rotates about the axis extending between the base and the duct.   
     
     
         11 . A combustion system according to  claim 10 , wherein the plurality of secondary gas nozzles are located 0.5-3 metres away from the combustion devices, measured along the axis extending between the base and the flue duct. 
     
     
         12 . A combustion system according to  claim 10 , the system being arranged to supply gas to the combustion devices and the plurality of secondary gas nozzles from the same source. 
     
     
         13 . A combustion system according to  claim 12 , wherein the gas supplied to the combustion devices and the plurality of secondary gas nozzles is pressurised by the same fan. 
     
     
         14 . A method of operating a combustion system according to  claim 10 , comprising the step of delivering fuel and gas into the combustion chamber by means of the combustion devices to generate a fireball having a stoichiometry less than 0.9. 
     
     
         15 . A method of operating a combustion system according to  claim 10 , comprising the step of delivering gas into the combustion chamber via the plurality of secondary gas nozzles at a velocity of 40-70 m/s.