A mixture of air and fuel is received into a reaction chamber of a gas turbine system. The fuel is oxidized in the reaction chamber, and a maximum temperature of the mixture in the reaction chamber is controlled to be substantially at or below an inlet temperature of a turbine of the gas turbine system. The oxidation of the fuel is initiated by raising the temperature of the mixture to or above an auto-ignition temperature of the fuel. In some cases, the reaction chamber may be provided without a fuel oxidation catalyst material.