| Theory of operation Turbines impulse | | | | more delicate than their metallic counterparts, and |
| A working fluid contains potential energy (force head) | | | | carry a greater risk of catastrophic blade failure. This |
| and kinetic energy (speed head). The fluid may be | | | | has tended to limit their use in jet engines and gas |
| compressible or incompressible. Several physical | | | | turbines, to the stator (stationary) blades. |
| principles are working by turbines to collect this energy. | | | | * Shrouded turbine. Many turbine rotor blades have |
| Impulse turbines | | | | shrouding at the top, which interlocks with that of |
| These turbines change the direction of flow of a high | | | | adjacent blades, to increase damping and thereby |
| velocity fluid or gas jet. The resulting impulse spins the | | | | reduce blade flutter. In large land-based electricity |
| turbine and grass the fluid flow with diminished kinetic | | | | generation steam turbines, the shrouding is often |
| energy. There is no pressure change of the fluid or | | | | complemented, especially in the long blades of a |
| gas in the turbine rotor blades as in the case of a | | | | low-pressure turbine, with lacing wires. These are |
| steam or gas turbine, all the pressure drop takes place | | | | wires which pass through holes drilled in the blades at |
| in the motionless blades.created by the nozzle prior to | | | | suitable distances from the blade root and the wires |
| reaching the blading on the rotor. Newton's second la | | | | are usually brazed to the blades at the point where |
| Before reaching the turbine, the fluid's pressure head is | | | | they pass through. The lacing wires are designed to |
| changed to velocity head by accelerating the fluid with | | | | reduce blade flutter in the central part of the blades. |
| a nozzle. Pelt-on wheels and de Laval turbines use this | | | | The introduction of lacing wires significantly reduces |
| process entirely. Impulse turbines do not require a | | | | the instances of blade failure in large or low-pressure |
| pressure casement around the rotor since the fluid jet | | | | turbines. |
| is w describes the transfer of energy for impulse | | | | * Shroud less turbine. Currently observe is, wherever |
| turbines. | | | | possible, to eliminate the rotor shrouding, thus reducing |
| Types of turbines | | | | the centrifugal load on the blade and the cooling |
| * Steam turbines. are used for the production of | | | | requirements. |
| electricity in thermal power plants, such as plants using | | | | * Bladeless turbine. Uses the boundary layer effect |
| coal or fuel oil or nuclear power. They were once | | | | and not a fluid impinging upon the blades as in a |
| used to directly drive mechanical devices such as | | | | conventional turbine. |
| ships' propellers but mainly such applications now use | | | | * Water turbines |
| decrease gears or a transitional electrical step, where | | | | - Pelt-on turbine, a type of impulse water turbine. |
| the turbine is used to generate electricity, which then | | | | - Francis turbine, a type of widely used water turbine. |
| powers an electric motor connected to the mechanical | | | | - Kaplan turbine, a variation of the Francis Turbine. |
| load. Turbo electric ship machinery was particularly | | | | * Wind turbine. These normally operate as a single |
| popular in the period immediately before and during | | | | stage without nozzle and inter stage guide vanes. An |
| WWII, primarily due to a lack of sufficient gear-cutting | | | | exception is the Elaine Belle, which has a stator and a |
| facilities in shipyards. | | | | rotor, thus being a true turbine. |
| * Gas turbines. are sometimes referred to as turbine | | | | Uses of turbines |
| engines. Such engines usually quality an inlet, fan, | | | | - Nearly all electrical power on Earth is produced with |
| compressor, combustor and nozzle (possibly other | | | | a turbine of some type. Very high efficiency steam |
| assemblies) in addition to one or more turbines. | | | | turbines control about 40% of the thermal energy, with |
| * Transonic turbine. The gas flow in most turbines | | | | the rest exhausted as waste heat. |
| employed in gas turbine engines remains subsonic all | | | | - Most jet engines rely on turbines to supply |
| through the development process. In a transonic turbine | | | | mechanical work from their working fluid and fuel as |
| the gas-flow becomes supersonic as it exits the | | | | do all nuclear ships and power plants. |
| nozzle guide vanes, while the downstream velocities | | | | - Turbines are regularly part of a larger machine. A |
| normally become subsonic. Transonic turbines operate | | | | gas turbine, for example, may refer to an internal |
| at a higher pressure ratio than normal but are usually | | | | combustion machine that contains a turbine, ducts, |
| less efficient and singular. | | | | compressor, combustor, heat-exchanger, fan and (in |
| * Contra-rotating turbines. With axial turbines, some | | | | the case of one designed to produce electricity) an |
| efficiency improvement can be obtained if a | | | | alternator. However, it must be noted that the |
| downstream turbine rotates in the opposite direction to | | | | collective machine referred to as the turbine in these |
| an upstream unit. However, the complication can be | | | | cases is designed to transfer energy from a fuel to |
| counter-productive. A contra-rotating steam turbine, | | | | the fluid passing through such an internal combustion |
| usually known as the Ljungström turbine, was | | | | device as a means of propulsion, and not to transfer |
| originally made-up by Swedish Engineer Fredrik | | | | energy from the fluid passing through the turbine to the |
| Ljungström (1875-1964), in Stockholm and in | | | | turbine as is the case in turbines used for electricity |
| partnership with his brother Birger Ljungström he | | | | provision etc. |
| obtained a copyright in 1894. The design is essentially a | | | | - Reciprocating piston engines such as aircraft engines |
| multi-stage radial turbine (or pair of 'nested' turbine | | | | can use a turbine powered by their exhaust to drive |
| rotors) and met with some success, particularly in | | | | an intake-air compressor, a configuration known as a |
| marine applications, where its compact size and low | | | | turbocharger (turbine supercharger) or colloquially, a |
| weight lend itself well to turbo-electric applications. In | | | | "turbo". |
| this radial arrangement, the overall efficiency is typically | | | | - Turbines can have very high power density (ie the |
| less than that of Parsons or de Laval turbines. | | | | ratio of power to weight, or power to volume). This is |
| * Stator less turbine. Multi-stage turbines have a set of | | | | because of their ability to operate at very high speeds. |
| static (meaning stationary) inlet guide vanes that direct | | | | The Space Shuttle's main engines use turbo pumps |
| the gas-flow onto the rotating rotor blades. In a | | | | (machines consisting of a pump driven by a turbine |
| stator-less turbine the gas-flow exiting an upstream | | | | engine) to feed the propellants (liquid oxygen and liquid |
| rotor impinge onto a downstream rotor without an | | | | hydrogen) into the engine's combustion chamber. The |
| intermediate set of stator vanes individual encountered. | | | | liquid hydrogen turbo pump is slightly larger than an |
| * Ceramic turbine. Conventional high-pressure turbine | | | | automobile engine (weighing approximately 700 lb) and |
| blades (and vanes) are made from nickel based alloys | | | | produces nearly 70,000 hp (52.2 MW). |
| and often utilize complicated internal air-cooling | | | | - Turbo expanders are widely used as sources of |
| passages to prevent the metal from overheating. In | | | | refrigeration in industrial processes. |
| recent years, experimental ceramic blades have been | | | | - Turbines could also be used as powering system for |
| manufactured and tested in gas turbines, with a view | | | | a remote controlled plane that creates thrust and lifts |
| to increasing Rotor Inlet Temperatures along with | | | | the plane of the ground. |
| possibly, eliminating air-cooling. Ceramic blades are | | | | |