A system and method are disclosed for high temperature protection of combustor and other components by controlling the temperature of combustor gases in a hybrid fuel cell system combustor using a nozzle or plurality of nozzles to inject water or water vapor, downstream or directly into the combustor. A variable speed pump, actuated valve or other flow metering device regulates the supply of water to the nozzles and a steam generator. Flow regulation is effected by a control algorithm that reacts to combustor temperature, changes in the power production of the fuel cell system and/or other related system parameters.