Method of operating a combustor from a liquid fuel to a gas fuel operation

A method of operating a gas turbine having a combustor, the combustor having a central nozzle and a plurality of outer nozzles surrounding the central nozzle, comprising;

• providing a liquid fuel to only the plurality of outer nozzles at a specified total energy input to the gas turbine;
• and
• transitioning from liquid fuel operation of the combustor to gas fuel operation, the transition comprising:
• decreasing the liquid fuel to the plurality of outer nozzles while simultaneously increasing a gas fuel to the central nozzle and the plurality of outer nozzles to substantially maintain the specified total energy input to the gas turbine;
• supplying a fuel-air ratio of the gas fuel to the central nozzle that exceeds a threshold value such that a central nozzle flame is anchored;
• supplying the fuel-air ratio of the gas fuel to the plurality of outer nozzles that is less than the threshold value such that a plurality of outer nozzle flames are lifted;
• ceasing a supply of the liquid fuel to the plurality of outer nozzles while substantially maintaining the specified total energy input to the gas turbine;
• supplying a purge flow to the plurality of outer nozzles;
• and
• supplying the fuel-air ratio of the gas fuel to the plurality of outer nozzles that exceeds the threshold value such that at least one of the plurality of outer nozzle flames are anchored as the purge flow is supplied to the plurality of outer nozzles.