Abstract: A gas turbine apparatus that can be operated selectively in a simple cycle or in a combined steam turbine cycle increases the efficiency of the installation and provides easy switch-over from the simple cycle to the combined cycle, and at the same time provides for cooling the cooling air for the gas turbine. The gas turbine and waste-heat boiler are connected by a transition piece. A heat exchanger for cooling the cooling air is disposed in a duct connected to the transition piece for introducing a gaseous medium for mixing with the gas turbine exhaust. The gaseous medium cools the cooling air and is accordingly heated. The heated gaseous medium is mixed with the exhaust gas of the turbine, and the mixture directed to the waste heat boiler to generate steam for the steam turbine for operating in the combined cycle. A simply operated duct selectively directs the flow of the mixture.

Abstract: A method for operating a gas turbine selectively in a simple cycle or in a combined steam turbine cycle increases the efficiency of the installation and provides easy switch-over from the simple cycle to the combined cycle, and at the same time providing for cooling the cooling air for the gas turbine. The method in accordance with the invention includes the steps of using the exhaust gas from the gas turbine to generate steam in a waste heat boiler for the steam cycle. A heat exchanger for cooling the cooling air is disposed in a duct for introducing a gaseous medium for mixing with the gas turbine exhaust. The gaseous medium cools the cooling air and is accordingly heated. The heated gaseous medium is mixed with the exhaust gas of the turbine, and the mixture directed to the waste heat boiler to generate steam for the steam turbine for operating in the combined cycle. In the simple cycle, the mixture is released to the atmosphere. A simply operated duct selectively directs the flow of the mixture.