page_title: Steam turbine
section_title: Two-flow rotors
hierarchical_section_title: Steam turbine / Types / Two-flow rotors
caption_attribution_description: English: This is a low pressure steam turbine from the nuclear power plant Philippsburg/Germany. It has a weight of 190 t, is 11.47 m long and has a maximum diameter of 5.62 m. Input is 480 kg per second of steam with an entry pressure of 10.54 bar, output pressure of 0.0456 bar. The shaft rotated at 25 turns per second and the entire plant had a power of 1400 MW.
context_page_description: A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884.
  The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator—about 85% of all electricity generation in the United States in the year 2014 was by use of steam turbines.
context_section_description: The moving steam imparts both a tangential and axial thrust on the turbine shaft, but the axial thrust in a simple turbine is unopposed. To maintain the correct rotor position and balancing, this force must be counteracted by an opposing force. Thrust bearings can be used for the shaft bearings, the rotor can use dummy pistons, it can be double flow- the steam enters in the middle of the shaft and exits at both ends, or a combination of any of these. In a double flow rotor, the blades in each half face opposite ways, so that the axial forces negate each other but the tangential forces act together. This design of rotor is also called two-flow, double-axial-flow, or double-exhaust. This arrangement is common in low-pressure casings of a compound turbine.
caption: A two-flow turbine rotor. The steam enters in the middle of the shaft, and exits at each end, balancing the axial force.
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