SYSTEM AND METHOD HAVING MULTI-FLUID INJECTORS FOR ISOTHERMAL EXPANSION IN TURBINE STAGE OF GAS TURBINE ENGINE

A system includes a gas turbine having a turbine stage disposed in a combustion gas path, wherein the turbine stage includes turbine vanes disposed upstream from turbine blades. The system includes an isothermal expansion system coupled to the turbine stage. The isothermal expansion system includes multi-fluid injectors configured to vary axial positions of combustion within a turbine stage expansion of the turbine stage to reduce temperature variations over the turbine stage expansion, wherein at least one of the multi-fluid injectors is coupled to each of the turbine vanes. Each of the multi-fluid injectors includes a fuel port configured to inject a fuel, an oxidant port configured to inject an oxidant, and a barrier fluid port configured to inject a barrier fluid between the fuel and the oxidant, wherein the barrier fluid is configured to delay mixing between the fuel and the oxidant.