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35-410: Unlike the other seven reactors of this program, it did not use a steam turbine, but instead used a nitrogen coolant at 315 pounds per square inch (2,170 kPa) to drive a closed-cycle gas turbine . It was designed to produce 3.3 MW thermal of heat and 400 kW of shaft horsepower with an outlet temperature of 1,200 °F (649 °C). Though the concept of a nitrogen closed cycle gas turbine

70-480: A turbine map or characteristic. The number of blades in the rotor and the number of vanes in the stator are often two different prime numbers in order to reduce the harmonics and maximize the blade-passing frequency. A large proportion of the world's electrical power is generated by turbo generators . Turbines are used in gas turbine engines on land, sea and air. Turbochargers are used on piston engines. Gas turbines have very high power densities (i.e.

105-632: A calandria-based water-tube fission heat source unproven in the "real world", using nine atmospheres of pressure at the compressor inlet that saved space but required a custom-built turbine rather than one designed for atmospheric pressures, placing insulating foil within the gas piping to improve efficiency (the foil later broke off and contaminated the closed loop with its flecks, causing deflaking problems for engineers), and using custom-built, first-of-a-kind components instead of using commercially proven aircraft or power generation derived turbines. Closed-cycle gas turbine A closed-cycle gas turbine

140-440: A designer to change from impulse at the base, to a high reaction-style tip. Classical turbine design methods were developed in the mid 19th century. Vector analysis related the fluid flow with turbine shape and rotation. Graphical calculation methods were used at first. Formulae for the basic dimensions of turbine parts are well documented and a highly efficient machine can be reliably designed for any fluid flow condition . Some of

175-443: A peak output of 66% of the specified electrical output), but it had numerous major issues along the route to working. Rapid shutdowns were commonplace, often due to spurious sensor readings, while real mechanical problems - with the non-nuclear components of the system - often were undetected until a degree of damage occurred. Fairly or unfairly, it became regarded to a certain extent as a "lemon" by top Army brass, and budget cuts due to

210-476: A period of 10 years would be about ten times that of a comparable diesel plant at normal fuel costs. The basic concept of a closed-cycle gas turbine using nitrogen, a relatively inert gas, in a closed loop with a fission heat source interposed between the compressor and turbine stages of a gas turbine was and remains very strong. As such, the Atomic Energy Commission saw that such a reactor might meet

245-417: A pressure casement around the rotor since the fluid jet is created by the nozzle prior to reaching the blades on the rotor. Newton's second law describes the transfer of energy for impulse turbines. Impulse turbines are most efficient for use in cases where the flow is low and the inlet pressure is high. Reaction turbines develop torque by reacting to the gas or fluid's pressure or mass. The pressure of

280-402: A reaction lift from the moving fluid and impart it to the rotor. Wind turbines also gain some energy from the impulse of the wind, by deflecting it at an angle. Turbines with multiple stages may use either reaction or impulse blading at high pressure. Steam turbines were traditionally more impulse but continue to move towards reaction designs similar to those used in gas turbines. At low pressure

315-989: Is a turbine that uses a gas (e.g. air, nitrogen , helium , argon , etc.) for the working fluid as part of a closed thermodynamic system . Heat is supplied from an external source. Such recirculating turbines follow the Brayton cycle . The initial patent for a closed-cycle gas turbine (CCGT) was issued in 1935 and they were first used commercially in 1939. Seven CCGT units were built in Switzerland and Germany by 1978. Historically, CCGTs found most use as external combustion engines "with fuels such as bituminous coal , brown coal and blast furnace gas " but were superseded by open cycle gas turbines using cleaner-burning fuels (e.g. " gas or light oil "), especially in highly efficient combined cycle systems. Air-based CCGT systems have demonstrated very high availability and reliability. The most notable helium-based system thus far

350-419: Is derived to be independent of turbine size. Given the fluid flow conditions and the desired shaft output speed, the specific speed can be calculated and an appropriate turbine design selected. The specific speed, along with some fundamental formulas can be used to reliably scale an existing design of known performance to a new size with corresponding performance. Off-design performance is normally displayed as

385-565: The Académie royale des sciences in Paris. However, it was not until 1824 that a committee of the Académie (composed of Prony, Dupin, and Girard) reported favorably on Burdin's memo. Benoit Fourneyron , a former student of Claude Burdin, built the first practical water turbine. Credit for invention of the steam turbine is given both to Anglo-Irish engineer Sir Charles Parsons (1854–1931) for invention of

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420-477: The Greek τύρβη , tyrbē , or Latin turbo , meaning vortex ) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work . The work produced can be used for generating electrical power when combined with a generator . A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on

455-588: The Vietnam War shut it down for good in 1965. Rodney Adams, in a 1996 Atomic Insights article, argues that the ML-1 design and implementation was flawed due to the decision to build an advanced, highly efficient, easily transportable closed-cycle nitrogen gas turbine before any other functional version of the design had been created. Adams opines that the designers of ML-1 made several incorrect decisions, including adding an unnecessary recuperator to enhance efficiency, using

490-542: The blade root to its periphery. Hero of Alexandria demonstrated the turbine principle in an aeolipile in the first century AD and Vitruvius mentioned them around 70 BC. Early turbine examples are windmills and waterwheels . The word "turbine" was coined in 1822 by the French mining engineer Claude Burdin from the Greek τύρβη , tyrbē , meaning " vortex " or "whirling", in a memo, "Des turbines hydrauliques ou machines rotatoires à grande vitesse", which he submitted to

525-405: The blades so that they move and impart rotational energy to the rotor. Gas , steam , and water turbines have a casing around the blades that contains and controls the working fluid. The word "turbine" was coined in 1822 by the French mining engineer Claude Burdin from the Greek τύρβη , tyrbē , meaning " vortex " or "whirling". Benoit Fourneyron , a former student of Claude Burdin, built

560-401: The calculations are empirical or 'rule of thumb' formulae, and others are based on classical mechanics . As with most engineering calculations, simplifying assumptions were made. Velocity triangles can be used to calculate the basic performance of a turbine stage. Gas exits the stationary turbine nozzle guide vanes at absolute velocity V a1 . The rotor rotates at velocity U . Relative to

595-462: The delivered product. The ML-1 first operated as a power plant on September 21, 1962, producing only a few kilowatts of electricity. It first reached full power on February 28, 1963 . On March 4, after the first 100-hour high power test, it was discovered that coolant gas was leaking into the moderator water. The plant was disassembled and rebuilt, and went back online in the spring of 1964. The ML-1 worked (though never to specification, only achieving

630-424: The expanding gas efficiently. Newton's third law describes the transfer of energy for reaction turbines. Reaction turbines are better suited to higher flow velocities or applications where the fluid head (upstream pressure) is low. In the case of steam turbines, such as would be used for marine applications or for land-based electricity generation, a Parsons-type reaction turbine would require approximately double

665-423: The first practical water turbine. Credit for invention of the steam turbine is given both to Anglo-Irish engineer Sir Charles Parsons (1854–1931) for invention of the reaction turbine, and to Swedish engineer Gustaf de Laval (1845–1913) for invention of the impulse turbine. Modern steam turbines frequently employ both reaction and impulse in the same unit, typically varying the degree of reaction and impulse from

700-527: The gas or fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the turbine stage(s) or the turbine must be fully immersed in the fluid flow (such as with wind turbines). The casing contains and directs the working fluid and, for water turbines, maintains the suction imparted by the draft tube . Francis turbines and most steam turbines use this concept. For compressible working fluids, multiple turbine stages are usually used to harness

735-491: The mean stage radius. Mean performance for the stage can be calculated from the velocity triangles, at this radius, using the Euler equation : Hence: where: The turbine pressure ratio is a function of Δ h T {\displaystyle {\frac {\Delta h}{T}}} and the turbine efficiency. Modern turbine design carries the calculations further. Computational fluid dynamics dispenses with many of

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770-469: The needs of the Army; the Army was interested, and the design and fabrication process began. The design of ML-1 was driven by the requirements of the customer, i.e., the Army, which wanted a turbine transportable by aircraft (having a low weight and being a cargo container in size) which led the engineers of Aerojet-General Nucleonics, the principal contractor, to make unusual design choices. Extensive shielding

805-523: The number of blade rows as a de Laval-type impulse turbine, for the same degree of thermal energy conversion. Whilst this makes the Parsons turbine much longer and heavier, the overall efficiency of a reaction turbine is slightly higher than the equivalent impulse turbine for the same thermal energy conversion. In practice, modern turbine designs use both reaction and impulse concepts to varying degrees whenever possible. Wind turbines use an airfoil to generate

840-415: The operating fluid medium expands in volume for small reductions in pressure. Under these conditions, blading becomes strictly a reaction type design with the base of the blade solely impulse. The reason is due to the effect of the rotation speed for each blade. As the volume increases, the blade height increases, and the base of the blade spins at a slower speed relative to the tip. This change in speed forces

875-416: The plant worked (on paper); and was transportable to Army requirements. The ML-1 was fabricated as specified, though it was discovered later that materials not to specification were present (the specified stainless steel alloy for some of the piping, grade 316L had insufficient chromium in its composition in several locations, making it susceptible to corrosion) though this was not immediately evident in

910-410: The ratio of power to mass, or power to volume) because they run at very high speeds. The Space Shuttle main engines used turbopumps (machines consisting of a pump driven by a turbine engine) to feed the propellants (liquid oxygen and liquid hydrogen) into the engine's combustion chamber. The liquid hydrogen turbopump is slightly larger than an automobile engine (weighing approximately 700 lb) with

945-460: The reaction turbine, and to Swedish engineer Gustaf de Laval (1845–1913) for invention of the impulse turbine. A working fluid contains potential energy (pressure head ) and kinetic energy (velocity head). The fluid may be compressible or incompressible . Several physical principles are employed by turbines to collect this energy: Impulse turbines change the direction of flow of a high velocity fluid or gas jet. The resulting impulse spins

980-459: The rotor, the velocity of the gas as it impinges on the rotor entrance is V r1 . The gas is turned by the rotor and exits, relative to the rotor, at velocity V r2 . However, in absolute terms the rotor exit velocity is V a2 . The velocity triangles are constructed using these various velocity vectors. Velocity triangles can be constructed at any section through the blading (for example: hub, tip, midsection and so on) but are usually shown at

1015-408: The simplifying assumptions used to derive classical formulas and computer software facilitates optimization. These tools have led to steady improvements in turbine design over the last forty years. The primary numerical classification of a turbine is its specific speed . This number describes the speed of the turbine at its maximum efficiency with respect to the power and flow rate. The specific speed

1050-437: The supercritical CO 2 cycle is comparable efficiency with the helium Brayton cycle at significantly lower temperature" (550 °C vs. 850 °C), but with the disadvantage of higher pressure (20 MPa vs. 8 MPa). Sandia National Laboratories had a goal of developing a 10 MWe supercritical CO 2 demonstration CCGT by 2019. Turbine A turbine ( / ˈ t ɜːr b aɪ n / or / ˈ t ɜːr b ɪ n / ) (from

1085-510: The turbine and leaves the fluid flow with diminished kinetic energy. There is no pressure change of the fluid or gas in the turbine blades (the moving blades), as in the case of a steam or gas turbine, all the pressure drop takes place in the stationary blades (the nozzles). Before reaching the turbine, the fluid's pressure head is changed to velocity head by accelerating the fluid with a nozzle . Pelton wheels and de Laval turbines use this process exclusively. Impulse turbines do not require

ML-1 - Misplaced Pages Continue

1120-547: Was Oberhausen 2 , a 50 megawatt cogeneration plant that operated from 1975 to 1987 in Germany. Compared to Europe where the technology was originally developed, CCGT is not well known in the US. Gas-cooled reactors powering helium-based closed-cycle gas turbines were suggested in 1945. The experimental ML-1 nuclear reactor in the early-1960s used a nitrogen-based CCGT operating at 0.9 MPa . The cancelled pebble bed modular reactor

1155-544: Was intended to be coupled with a helium CCGT. Future nuclear ( Generation IV reactors ) may employ CCGT for power generation, e.g. Flibe Energy intends to produce a liquid fluoride thorium reactor coupled with a CCGT. Closed-cycle gas turbines hold promise for use with future high temperature solar power and fusion power generation. They have also been proposed as a technology for use in long-term space exploration . Supercritical carbon dioxide closed-cycle gas turbines are under development; "The main advantage of

1190-499: Was omitted in favor of a personnel exclusion zone of 500 feet (150 m) while in operation; efficiency enhancing devices such as recuperators were incorporated; insulation was specified to keep thermal values within optimum limits; a complex control system and a complex core were implemented; a completely new gas turbine was designed for the application; and the working fluid - nitrogen - was compressed to 9 standard atmospheres (910 kPa). The design specification achieved its goals;

1225-448: Was strong, the design failed to live up to expectations, and was abandoned with the closure of ML-1 in 1965 after several major refits and with only a few hundred hours of testing completed in all. Similar concepts have been more recently proposed as part of the PBMR program as derivatives thereof. A 1964 economic analysis concluded that the overall cost of purchasing and operating the ML-1 for

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