3. Steam turbines

The steam turbines used in combined-cycle plants are no different from those used in other power generation facilities. They are adapted to the power level required for the plant, but their technology remains identical, i.e. it is possible to find machines with action or reaction stages. Either technology is specific to each manufacturer's know-how. Turbine speed depends on the power to be discharged. High-power machines can handle high steam flow rates, which requires a large cross-sectional area for the steam flow, and therefore large-diameter blades. Speed constraints are such that it has been necessary to design "half-speed" turbines, i.e. 1,500 rpm instead of the 3,000 rpm required for smaller machines. Turbine inlets can also be divided into two families: those with total injection and those with partial injection. Finally, a distinction can also be made between condensing and back-pressure...