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Tesla turbine at Nikola Tesla Museum The Tesla turbine is a bladeless centripetal flow
turbine A turbine ( or ) (from the Greek , ''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 ...
invented by
Nikola Tesla Nikola Tesla (;"Tesla"
. ''Random House Webster's Unabridged Dictionary''.
; 10 July 1856 – 7 ...
in 1913. It functions as nozzles apply a moving fluid to the edges of a set of discs. The engine uses smooth discs rotating in a chamber to generate rotational movement due to the
momentum In Newtonian mechanics, momentum (: momenta or momentums; more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. ...
exchange between the fluid and the discs. The discs are arranged in an orientation similar to a stack of CDs on an axle. The Tesla
turbine A turbine ( or ) (from the Greek , ''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 ...
uses the boundary-layer effect, instead of the method employed by more conventional turbines, wherein a fluid acts on blades. The Tesla turbine is also referred to as the ''bladeless turbine'', ''boundary-layer turbine'', ''cohesion-type turbine'', and ''Prandtl-layer turbine.'' The latter is named for Ludwig Prandtl. Bioengineering researchers have additionally referred to the Tesla turbine as a multiple-disk
centrifugal pump Centrifugal pumps are used to transport fluids by the Energy transformation, conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are ...
. One of Tesla's intended implementations for this turbine was for the generation of
geothermal power Geothermal power is electricity generation, electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation i ...
, which he described in his work '' Our Future Motive Power''.


Theory

In standard
steam turbines A steam turbine or steam turbine engine is a machine or heat engine that extracts thermal energy from pressurized steam and uses it to do mechanical work utilising a rotating output shaft. Its modern manifestation was invented by Sir Charles Par ...
, the steam must press on the blades for the rotor to extract energy from the steam; the blades must be carefully oriented to minimize the angle of attack to the blade surface area. In other words, in the optimal regime, the orientation of the blades minimizes the angle (blade pitch) with which the steam is hitting their surface area, to create smooth steam flow and to minimize
turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...
. This turbulence reduces the amount of useful energy that can be extracted from the incoming steam flow. In the Tesla turbine, considering that there are no blades to be impacted, the mechanics of the reaction forces are different. The reaction force to the steam head pressure builds relatively quickly, in the form of a steam pressure "belt" along the periphery of the turbine. That belt is most dense, and pressurized, in the periphery as its pressure, when the rotor is not under load, will be not much less than the (incoming) steam pressure. In a normal operational mode, that peripheral pressure limits the flow of the incoming stream, and in this way, the Tesla turbine can be said to be self-governing. When the rotor is not under load, the relative speeds between the "steam compressed spirals" (SCS, the steam spirally rotating between the disks) and the disks are minimal. When a load is applied to the Tesla turbine, the shaft slows down; that is, the speed of the discs relative to the (moving) fluid increases as the fluid, at least initially, preserves its angular momentum. For example, in a radius, where at 9000
RPM Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...
the peripheral disk speeds are when there is no load on the rotor, the disks move at approximately the same speed as the fluid, but when the rotor is loaded, the relative velocity differential (between the SCS and the metal disks) increases and, at a rotor speed of , the rotor has a relative speed of 45 m/s to the SCS. This is a dynamic environment, and these speeds reach these values over time interval and not instantly. Here we have to note that fluids start to behave like solid bodies at high relative velocities, and in the case of the Tesla turbine, we also have to take into consideration the additional pressure. With this pressure and relative velocity toward the faces of the discs, the steam should start behaving like a solid body (SCS) dragging on the disks' surfaces. The created "friction" can only lead to the generation of additional heat directly on the disk and in SCS and will be most pronounced in the peripheral layer, where the relative velocity between the metal discs and SCS discs is the highest. This increase in the temperature, due to the friction between the SCS disks and the turbine disks, will be translated to an increase in the SCS temperature, and that will lead to SCS steam expansion and pressure increase perpendicular to the metal discs as well as radially on the axis of rotation, and so this fluid-dynamic model appears to be positive feedback for transmitting a stronger "dragging" on the metal disks and consequently increasing the torque at the axis of rotation.


Design

View of Tesla turbine system View of Tesla turbine bladeless design The guiding principle for developing the Tesla turbine is the idea that, to obtain the highest efficiency, the changes in the velocity and direction of movement of fluid should be as gradual as possible. Therefore, the propelling fluid of the Tesla turbine moves in natural paths, or streamlines, of least resistance. A Tesla turbine consists of a set of smooth disks, with
nozzle A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe (material), pipe. A nozzle is often a pipe or tube of varying cross ...
s applying a moving fluid to the edge of the disk. The fluid drags on the disk through
viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...
and the
adhesion Adhesion is the tendency of dissimilar particles or interface (matter), surfaces to cling to one another. (Cohesion (chemistry), Cohesion refers to the tendency of similar or identical particles and surfaces to cling to one another.) The ...
of the surface layer of the fluid. As the fluid slows and adds energy to the disks, it spirals into the center exhaust. Since the
rotor ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. To get it operational as quickly as possible, it was initially made up primarily of WWII-era syst ...
is a simple disk, it is more robust and easier to manufacture, compared to a traditional bladed turbine. Tesla wrote:
This turbine is an efficient self-starting prime mover which may be operated as a steam or mixed fluid turbine at will, without changes in construction and is on this account very convenient. Minor departures from the turbine, as may be dictated by the circumstances in each case, will suggest themselves but if it is carried out on these general lines it will be found highly profitable to the owners of the steam plant while permitting the use of their old installation. However, the best economic results in the development of power from steam by the Tesla turbine will be obtained in plants especially adapted for the purpose.
Smooth rotor disks were originally proposed, but these gave poor starting torque. Tesla subsequently discovered that smooth rotor disks with small washers bridging the disks in about 12 to 24 places around the perimeter of a 10″ disk and a second ring of 6–12 washers at a sub-diameter made for a significant improvement in starting torque without compromising efficiency.


Efficiency and calculations

Testing of a Tesla turbine In Tesla's time, the efficiency of conventional turbines was low because turbines used a direct-drive system that severely limited the potential usable output speed of a turbine. At the time of introduction, ship turbines were massive, and included dozens, or even hundreds, of stages of turbines, yet produced extremely low efficiency due to their low speed. For example, the turbine on both the '' Olympic'' and ''
Titanic RMS ''Titanic'' was a British ocean liner that sank in the early hours of 15 April 1912 as a result of striking an iceberg on her maiden voyage from Southampton, England, to New York City, United States. Of the estimated 2,224 passengers a ...
'' weighed over 400 tons, ran at only 165
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...
, and used steam at a pressure of only 6
psi Psi, PSI or Ψ may refer to: Alphabetic letters * Psi (Greek) (Ψ or ψ), the twenty-third letter of the Greek alphabet * Psi (Cyrillic), letter of the early Cyrillic alphabet, adopted from Greek Arts and entertainment * "Psi" as an abbreviat ...
. This limited it to harvesting waste steam from the main power plants, a pair of reciprocating steam engines. The Tesla turbine could run on higher-temperature gases than bladed turbines of the time, which contributed to its greater efficiency. Eventually, axial turbines were given gearing to allow them to operate at higher speeds, but the efficiency of axial turbines remained very low in comparison to the Tesla turbine. Continued improvements resulted in dramatically more efficient and powerful axial turbines, and a second stage of reduction gears was introduced in most cutting-edge U.S. naval ships of the 1930s. The improvement in steam technology gave the U.S. Navy aircraft carriers a clear advantage in speed over both Allied and enemy aircraft carriers, and so the proven axial steam turbines became the preferred form of propulsion until the
1973 oil crisis In October 1973, the Organization of Arab Petroleum Exporting Countries (OAPEC) announced that it was implementing a total oil embargo against countries that had supported Israel at any point during the 1973 Yom Kippur War, which began after Eg ...
, which drove the majority of new civilian vessels to turn to diesel engines. Axial steam turbines still had not exceeded 50% efficiency by that time, and so civilian ships chose to use diesel engines due to their superior efficiency. By this time, the comparably-efficient Tesla turbine was over 60 years old. Tesla's design attempted to sidestep the key drawbacks of the bladed axial turbines, and even the lowest estimates for efficiency still dramatically outperformed the efficiency of axial steam turbines of the day. However, in testing against more modern engines, the Tesla turbine had expansion efficiencies far below contemporary steam turbines and far below contemporary reciprocating steam engines. It also suffers from other problems, such as shear losses and flow restrictions, but this is partially offset by the relatively massive reduction in weight and volume. Some of the Tesla turbine's advantages lie in relatively-low-flow-rate applications or when small sizes are needed. The disks need to be as thin as possible at the edges in order to not introduce turbulence as the fluid leaves the disks. This translates to needing to increase the number of disks as the flow rate increases. Maximum efficiency comes in this system when the inter-disk spacing approximates the thickness of the
boundary layer In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a Boundary (thermodynamic), bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces ...
, and since boundary layer thickness is dependent on viscosity and pressure, the claim that a single design can be used efficiently for a variety of fuels and fluids is incorrect. A Tesla turbine differs from a conventional turbine only in the mechanism used for transferring energy to the shaft. Various analyses demonstrate that the flow rate between the disks must be kept relatively low to maintain efficiency. Reportedly, the efficiency of the Tesla turbine decreases with increased load. Under light load, the spiral taken by the fluid moving from the intake to the exhaust is tight, undergoing many rotations. Under load, the number of rotations drops, and the spiral becomes progressively shorter. This will increase the shear losses and also reduce the efficiency because the gas is in contact with the discs for less distance. upA man holding a Tesla turbine The turbine efficiency (defined as the ratio of the ideal change in
enthalpy Enthalpy () is the sum of a thermodynamic system's internal energy and the product of its pressure and volume. It is a state function in thermodynamics used in many measurements in chemical, biological, and physical systems at a constant extern ...
to the real enthalpy for the same change in
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...
) of the gas Tesla turbine is estimated to be above 60%. The turbine efficiency is different from the cycle efficiency of the engine using the turbine. Axial turbines that operate today in steam plants or
jet engines A jet engine is a type of reaction engine, discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition may include Rocket engine, rocket, Pump-jet, water jet, and ...
have efficiencies of over 90%. This is different from the cycle efficiencies of the plant or engine, which are between approximately 25% and 42%, and are limited by any irreversibility to be below the
Carnot cycle A Carnot cycle is an ideal thermodynamic cycle proposed by French physicist Nicolas Léonard Sadi Carnot, Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem (thermodynamics), Carnot's theorem, it provides ...
efficiency. Tesla claimed that a steam version of his device would achieve around 95% efficiency. The
thermodynamic efficiency In thermodynamics, the thermal efficiency (\eta_) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, steam turbine, steam engine, boiler, furnace, refrigerator, ACs etc. For a he ...
is a measure of how well it performs compared to an isentropic case. It is the ratio of the ideal to the actual work input/output. In the 1950s, Warren Rice attempted to recreate Tesla's experiments, but he did not perform these early tests on a pump built strictly in line with Tesla's patented design (it, among other things, was not a Tesla multiple staged turbine nor did it possess Tesla's nozzle). Rice's experimental single-stage system's working fluid was air. Rice's test turbines, as published in early reports, produced an overall measured efficiency of 36–41% for a ''single stage''. Higher efficiency would be expected if designed as originally proposed by Tesla. In his final work with the Tesla turbine published just before his retirement, Rice conducted a bulk-parameter analysis of model laminar flow in multiple disk turbines. A very high claim for rotor efficiency (as opposed to overall device efficiency) for this design was published in 1991 titled "Tesla Turbomachinery". This paper states: Modern multiple-stage bladed turbines typically reach 60–70% efficiency, while large steam turbines often show turbine efficiency of over 90% in practice.
Volute A volute is a spiral, scroll-like ornament that forms the basis of the Ionic order, found in the capital of the Ionic column. It was later incorporated into Corinthian order and Composite column capitals. Four are normally to be found on an ...
rotor-matched Tesla-type machines of reasonable size with common fluids (steam, gas, and water) would also be expected to show efficiencies in the vicinity of 60–70% and possibly higher.


Applications

A Tesla turbine with the top removed Tesla's patents state that the device was intended for the use of
fluid In physics, a fluid is a liquid, gas, or other material that may continuously motion, move and Deformation (physics), deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are M ...
s as motive agents, as distinguished from the propulsion or compression of fluids (though it can also be used for those purposes). As of 2016, the Tesla turbine has not seen widespread commercial use. The Tesla pump, however, has been commercially available since 1982 and is used to pump fluids that are abrasive, viscous, shear-sensitive, loaded with solids, or are otherwise difficult to handle with other pumps. Tesla himself did not procure a large contract for production. The main disadvantage was poor knowledge of material characteristics and behaviors at high
temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
s. The best
metallurgy Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the ...
of the day could not prevent the turbine disks from moving and warping unacceptably during operation. Many amateur experiments have been conducted using Tesla turbines with
compressed air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air in vehicle tires and shock absorbers are commonly used for improved traction and reduced vibration. Compressed air is an important medium for t ...
or steam as the power source. Disc warping has been ameliorated by using new materials such as carbon fiber. One proposed application for the device is a waste pump, in factories and mills where normal vane-type
turbine A turbine ( or ) (from the Greek , ''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 ...
pumps typically become fouled. Applications of the Tesla turbine as a multiple-disk centrifugal blood pump have yielded promising results due to the low peak shear force.
Biomedical engineering Biomedical engineering (BME) or medical engineering is the application of engineering principles and design concepts to medicine and biology for healthcare applications (e.g., diagnostic or therapeutic purposes). BME also integrates the logica ...
research on such applications has continued into the 21st century. The device functions as a pump if a similar set of disks and a housing with an
involute In mathematics, an involute (also known as an evolvent) is a particular type of curve that is dependent on another shape or curve. An involute of a curve is the Locus (mathematics), locus of a point on a piece of taut string as the string is eith ...
shape (versus circular for the turbine) are used. In this configuration, a motor is attached to the shaft. The fluid enters near the center, is energized by the disks, and exits at the periphery. The Tesla turbine does not use friction in the conventional sense, rather using adhesion (the Coandă effect) and
viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...
instead. It uses the boundary-layer effect on the disc blades.


History

The turbine was
patented A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...
by
Nikola Tesla Nikola Tesla (;"Tesla"
. ''Random House Webster's Unabridged Dictionary''.
; 10 July 1856 – 7 ...
on October 21, 1913, which was his 100th patent.


See also

*
List of Nikola Tesla patents Nikola Tesla was an inventor who obtained around 300 patents worldwide for his inventions. Some of Tesla's patents are not accounted for, and various sources have discovered some that have lain hidden in patent archives. There are a minimum of 278 ...
* Radial turbine * Tesla coil


References


Further reading

* Tesla, Nikola
"Dr. Tesla Talks Of Gas Turbines"
Motor World. September 18, 1911. * * US106120

- New and useful Improvements in Rotary Engines and Turbines * US132955

- Includes the Tesla gas turbine * GB18608

- Form of rotor * GB18608

- Tesla turbine system * , ''Disc turbine inlet to assist self-starting'', Letourneau (February 11, 2002) * , ''Labyrinth seal for disc turbine'', Letourneau (February 13, 2002) * , ''Rotor assembly for disc turbine'', Letourneau (March 15, 2002) * , ''Method of and apparatus for a multi-stage boundary layer engine and process cell'', Hicks (December 13, 2005)


External links





from Uncle Taz Library

from OBI Laser Products
Tesla Turbine
featuring the work of Ken Rieli and others


Rice, Warren, "''"Tesla Turbomachinery''." Proc. IV International Nikola Tesla Symposium, Sept. 23-25, 1991




* ttp://www.stanford.edu/~hydrobay/lookat/tt.html Swithenbank, Alan, "''The Tesla Boundary Layer Turbine''"
Peterson, Gary, ''Nikola Tesla's Disk Turbine''
Tomorrow's Gas Engine. Feed Line No. 7
Boundary Layer Effect


{{Nikola Tesla Inventions by Nikola Tesla Turbines Boundary layers Mechanical devices using viscosity