Turbines, steam rotors

The superheated steam generated in the superheater section is coHected in a header pipe that leads to the plant s high pressure steam turbine. The steam turbine s rotor consists of consecutive sets of large, curved, steel aHoy disks, each of which anchors a row of precision-cast turbine blades, also caHed buckets, which protmde tangentiaHy from the shaft and impart rotation to the shaft when impacted by jets of high pressure steam. Rows of stationary blades are anchored to the steam turbine s outer sheH and are located between the rows of moving rotor blades. 

All turbines are variable-speed drivers and operate near or above one of the rotor s critical speeds. Narrowbands should be established that track each of the critical speeds defined for the turbine s rotor. In most applications, steam turbines operate above the first critical speed and in some cases above the second. A movable narrowband window should be established to track the fundamental (1 x), second (2x), and third (3x) harmonics of actual shaft speed. The best method is to use orders analysis and a tachometer to adjust the window location. 

Reaction turbine design also makes use of steam jets (which are produced by steam flowing across static vanes), although the turbine has rotor discs that incorporate movable blades rather than buckets. The design utilizes the reactive force produced by steam accelerating through a nozzle (created by the combination of a stationary vane and a moving blade) to rotate the shaft. 

The steam turbine is a comparatively simple type of prime mover. It has only one major moving part, the rotor that carries the buckets or blades. These, with the stationary nozzles or blades, form the steam path through the turbine. The rotor is... 

Speidel M O, Denk J and Scarlin B 1991 Stress Corrosion Craoking and Corrosion Fatigue of Steam-Turbine Rotor and Blade Materials (Luxembourg Commission of the European Communities)... 

Maintenanee expenses are estimated at 3% for the required equipment. Spare wearing parts are allowed for the steam turbine. Every three years spare wearing parts and a rotor should be expensed for the power reeovery eases. Expensing a rotor every three years is eonsidered eonservative espeeially for the two-stage alternative. 

Most modem CCGT plants use open air cooling in the front part of the gas turbine. An exception is the GE MS9001H plant which utilises the existence of the lower steam plant to introduce steam cooling of the gas turbine. This reduces the difference between the combustion temperature T ot and the rotor inlet temperature The effect of this on the overall combined plant efficiency is discussed in Ref. [1] where it is suggested that any advantage is small. 

For a steam turbine to work efficiently, it is neces-saity that the velocity of the tips of the turbine blades be proportional to the velocity of the input steam jet. If the velocity of the input steam jet is high, it is nec-essaity to increase the radius of the blades so that their tip velocity becomes correspondingly high. These long rotor blades subject the entire assembly to unmanageable mechanical stresses at high speed. 

Steam turbines, which generate more than 80 percent of the world s electric power, differ from steam engines m that steam drives blades and not pistons. Steam turbines expand pressurized steam through nozzles that accelerate the steam at the expense of heat energy and pressure. Work is created by transferring a portion of steam velocity to blades, buckets, or nozzles affixed to a rotor to move at high speeds. Steam turbines are relatively compact in relation to steam... 

Gas and steam turbines rigid turbo-generator rotors rotors turbo-compressors machine-tool drives small electrical armatures turbine-driven pumps. 

Impulse turbine design employs a stationary, circular diaphragm onto which a large number of fixed-position, tear-shaped nozzle blades (vanes) are mounted. High-velocity steam moves across the vanes and produces steam jets that are directed into waterwheel-type buckets, mounted onto discs around the turbine rotor. The pressure of the steam in the buckets forces the shaft to rotate. The kinetic energy of the jets is translated into mechanical work as the shaft turns. 

If silica (in the form of volatile silicic acid) is present in steam at concentrations greater than 0.02 ppm Si02, turbine deposit problems result. In some cases, volatile silica appears not to significantly affect superheaters but certainly will always form deposits in turbines. Silica appears in different forms, depending on the steam pressure, and affects all turbine surfaces, It is most noticeable on the blades, which eventually results in rotor unbalancing. 

A turbine design where the expansion of steam occurs entirely in fixed nozzles. The steam jets from the nozzles are directed into disc-mounted buckets on the rotor forcing the shaft to rotate. 

A design of turbine in which a partial reduction in steam pressure takes place in fixed nozzles (vanes) and a further steam pressure reduction takes place in nozzles created by moving rotor blades. A reactive force is generated that results in the rotation of the turbine shaft. 

Rotor bodies, in steam turbines, 23 231 Rotor electrostatic separators, 16 643-644 Rotor rotating converter, 16 151 Rotors, molecular, 17 59-61 Rotor spinning cotton yarn, 3 17 Rotor-stator devices, 10 127 Rotor-stator disperser, 3 701 Rotor-stator mills, 13 65 Rotor-stator mixers, 16 674-675 Rotosil process, 22 412 Roughages, as ruminant feeds, 10 863 Roughing, in mineral separation, 16 604 Roughing services, magnetic drums used in, 15 446... 

For one thing, steam produced from hot-lime-softened water will have some amount of silicates. These silicates tend to deposit on the rotor blades of turbines, which use the motive steam as a source of energy. The silicate fouling of the turbine blades reduces the turbine s efficiency. But, more importantly, from an operator s point of view, the silicate deposits eventually break off of the blades. This unbalances the rotor. An unbalanced rotor is the fundamental cause of vibration, Vibrations lead to damage of the shaft bearings and seals. Eventually, vibrations will destroy the turbine s internal components. 

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