Gas turbine engine system and method for controlling a temperature of a conduit in a gas turbine engine system

According to one aspect of the invention, an engine system includes one or more fuel circuits (102) configured to provide gaseous fuel from a fuel source for combustion. The system further comprises a conduit (110) in fluid communication with the one or more fuel circuits (102), wherein the conduit (110) is configured to receive a first gaseous fuel flow (117) and an oxidant flow (150) for a reaction within the conduit (110), wherein a temperature of the conduit (110) is controlled by a second gaseous fuel flow (118) along an outer wall of the conduit (110).