Combustor head end assembly with dual pressure premixing nozzles

A combustor for a gas turbine (GT) system, the combustor comprising:

• a combustor liner defining a combustion region including a primary combustion zone and a secondary combustion zone downstream from the primary combustion zone;
• a flow sleeve surrounding at least part of the combustor liner, the flow sleeve including a plurality of cooling openings therein to:
• direct a flow of first air at a first pressure from a first air source to cool an outer surface of the combustor liner, and create a flow of second air at a second, lower pressure than the first pressure in an annulus between the combustor liner and the flow sleeve;
• a first fuel nozzle positioned at the primary combustion zone;
• a second fuel nozzle positioned at the secondary combustion zone;
• and
• a fuel source configured to deliver a first fuel to each of the first and second fuel nozzles,
• wherein the first and second fuel nozzles produce a premixture of the first air flow and the first fuel, and produce a mixture of the premixture and the second air flow, prior to introducing the mixture to a respective primary or secondary combustion zone.