Dual fuel can combustor with automatic liquid fuel purge

Abstract

A lean, low NOx gas-fired can combustor having liquid fuel operation capability includes a housing, a combustor liner disposed within the housing and defining a combustion zone for combusting fuel with air, and a head assembly for joining the longitudinal housing and liner ends and for supporting swirler vanes that admit about 45-55% of a total combustor air flow to the combustion zone. The head assembly includes multiple gaseous fuel injection ports upstream of the swirler vanes, and a single liquid fuel injector positioned along the liner axis for directing atomized liquid fuel into the combustion zone. The head assembly further includes a heat shield disposed between the injector and the combustion zone, and the head assembly is configured to provide a flow of air for cooling the heat shield during all operations of the can combustor. The can combustor may also include apparatus for automatically purging the liquid fuel injector with compressed air, such as cooled compressed air from a gas turbine engine compressor stage. The apparatus includes a shuttle valve controller including a shuttle member biased by a first pressure towards a first position interconnecting the liquid fuel input to the liquid fuel injector inlet, while blocking compressed purging air flow, and biased by a second pressure towards a second position interconnecting the compressed purging air input to the liquid fuel injector inlet, while blocking liquid fuel flow.

1 - 15 . (canceled) 
     
     
         16 . Apparatus for purging a liquid fuel injector in a can combustor, the can combustor being supplied liquid fuel from a liquid fuel source for combustion in the can combustor, the apparatus comprising:
 a source of compressed air for purging;   a liquid fuel controller having a liquid fuel inlet connectable to the fuel source, a compressed air inlet connectable to the compressed purging air source, and an outlet connectable to the injector,   wherein the controller further comprises a shuttle valve including a shuttle member biased by a first pressure towards a first position interconnecting the liquid fuel input to the controller outlet, and biased by a second pressure towards a second position interconnecting the compressed air input to the controller outlet, and   wherein the first and second pressures are set to automatically move the shuttle member to the first position when the can combustor is being operated with liquid fuel, and automatically move the shuttle member to the second position when purging of the injector with compressed air from the compressed air source is required.   
     
     
         17 . The purging apparatus as in  claim 16 , wherein the can combustor has a head assembly in which the injector is mounted, and wherein the shuttle valve is configured as part of the head assembly. 
     
     
         18 . The purge apparatus as in  claim 16 , wherein the can combustor is part of a gas turbine engine, the engine having an air compressor, and wherein the apparatus includes a conduit from the air compressor to the shuttle valve compressed purging air inlet. 
     
     
         19 . The purge apparatus as in  claim 18 , further including a pressure vessel operatively connected to the conduit for being pressurized with compressed air from the air compressor, and for supplying compressed air to the shuttle valve compressed purging air inlet during engine shut down. 
     
     
         20 . The purge apparatus as in  claim 18 , further including means for cooling the compressed air before it is provided to the shuttle valve compressed purging air inlet.