View source for Physics:Tesla turbine

{{short description|Bladeless centripetal flow turbine}}
thumb|Tesla turbine at [[Nikola Tesla Museum]]

The '''Tesla turbine''' is a bladeless centripetal flow [[Physics:Turbine|turbine]] invented by [[Biography:Nikola Tesla|Nikola Tesla]] in 1913.<ref name="US patent|1061206"/> 
Nozzles apply a moving fluid to the edges of a set of discs. The engine uses smooth discs rotating in a chamber to generate [[Physics:Rotation|rotational movement]] due to the exchange of [[Physics:Momentum|momentum]] between the fluid and the discs. The discs are arranged in an orientation similar to a stack of CDs on a pole.<ref>{{Cite web|title=The Tesla turbine: a failed invention with amazing applications|url=https://www.protec-arisawa.com/the-tesla-turbine-failed-invention-with-amazing-applications/|access-date=2023-08-01|language=es}}</ref>

The Tesla turbine 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 [[Biography:Ludwig Prandtl|Ludwig Prandtl]]. Bioengineering researchers have additionally referred to the Tesla turbine as a multiple-disk [[Engineering:Centrifugal pump|centrifugal pump]].<ref name="Miller-Sidhu-Fink-Etter"/><ref name="Miller-Fink"/>

One of Tesla's intended implementations for this turbine was for the generation of [[Earth:Geothermal power|geothermal power]], which he described in his work ''Our Future Motive Power''.<ref name="Our Future Motive Power"/>

==Theory==
{{ blockquote
|In the pump, the radial or static pressure, due to centrifugal force, is added to the tangential or dynamic (pressure), thus increasing the effective head and assisting in the expulsion of the fluid. In the motor, on the contrary, the first named pressure, being opposed to that of the supply, reduces the effective head and the velocity of radial flow towards the center. Again, the propelled machine a great torque is always desirable, this calling for an increased number of disks and smaller distance of separation, while in the propelling machine, for numerous economic reasons, the rotary effort should be the smallest and the speed the greatest practicable.
|author=Nikola Tesla<ref name="patent-1061206"/>
}}

In standard steam turbines, the steam has to press on the blades for the rotor to extract energy from the steam. In the bladed steam turbine, the blades must be carefully oriented in the optimal speed regime of the turbine's work, to minimize the angle of attack to the blade surface area. In their words, in the optimal regime, the orientation of the blades is trying to minimize the angle (blade pitch) with which the steam is hitting their surface area, to create smooth steam flow, and to try to minimize turbulence. These eddies are created in reaction to the steam impacting (although the minimized angle in the optimal turbine speed) the surface of the blades. In this dynamic, eddies first cause a loss of the useful energy that can be extracted from the system, and second, as they are in opposite directions, they subtract from the energy of the incoming steam flow.{{Citation needed|date=July 2021}}

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, as 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, as Tesla noted, plays the role of BEMF ([[Physics:Counter-electromotive force|Back Electromotive Force]]), limiting 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.{{Citation needed|date=July 2021}}

When a load is applied to the Tesla turbine, the shaft slows down, i.e., the relative speed of the discs to the (moving) fluid increases as the fluid, at least initially, preserves its angular momentum. For example, in a {{convert|10|cm|abbr=on}} radius, where at 9000 RPM the peripheral disk speeds are {{convert|90|m/s|abbr=on}} 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 {{convert|45|m/s|abbr=on}}, 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 delta and not instantly. Here we have to note that fluids start to behave like solid bodies at high relative velocities, and in the TT case, we also have to take into consideration the additional pressure. According to the logic, with this pressure and relative velocity toward the faces of the discs, the steam should start behaving like a solid body (SCS) dragging on disk metal 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 (SCS trying to expand, to absorb additional heat energy), 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.{{Citation needed|date=July 2021}}

==Design==
thumb|View of Tesla turbine system
thumb|View of Tesla turbine bladeless design

The guiding principle for developing the Tesla turbine is the idea that to attain the highest efficiency, the changes in the velocity and direction of movement of fluid should be as gradual as possible.<ref name="US patent|1061206"/> Therefore, the propelling fluid of the Tesla turbine moves in natural paths, or streamlines, of the least resistance.

A Tesla turbine consists of a set of smooth disks, with [[Physics:Nozzle|nozzle]]s applying a moving fluid to the edge of the disk. The fluid drags on the disk through [[Physics:Viscosity|viscosity]] and the [[Chemistry:Adhesion|adhesion]] 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 is a simple disk, it is more robust and easy 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."<ref name="rexresearch"/>

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==
thumb|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, modern 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 ''Olympic'' and ''Titanic'' weighed over 400 tons, ran at only 165 [[Revolutions per minute|rpm]], and used steam at a pressure of only 6 [[Pound per square inch|psi]]. This limited it to harvesting waste steam from the main power plants, a pair of reciprocating steam engines.<ref name="Titanic"/> The Tesla turbine also 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 [[Finance:1973 oil crisis|1973 oil crisis]] took place. It 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.<ref name="Wilson"/> 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 Tesla's turbine advantages lie in relatively low flow rate applications or when small applications are called for. The disks need to be as thin as possible at the edges in order not to 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 [[Physics:Boundary layer|boundary layer]], and since [[Physics:Boundary layer thickness|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 drops with increased load. Under light load, the spiral taken by the fluid moving from the intake to the exhaust is a tight spiral, undergoing many rotations. Under load, the number of rotations drops, and the spiral becomes progressively shorter.{{Citation needed|date=February 2007}} This will increase the shear losses and also reduce the efficiency because the gas is in contact with the discs for less distance.

thumb|upright|A man holding a Tesla turbine

The turbine efficiency (defined as the ratio of the ideal change in [[Physics:Enthalpy|enthalpy]] to the real enthalpy for the same change in [[Physics:Pressure|pressure]]{{citation needed|date=September 2021}}) of the gas Tesla turbine is estimated to be above 60%.{{Citation needed|date=July 2015}} 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 have efficiencies of over 90%.<ref name="Denton"/> 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 [[Physics:Carnot cycle|Carnot cycle]] efficiency. Tesla claimed that a steam version of his device would achieve around 95% efficiency.<ref name="Stearns"/><ref name="Aquila"/> The thermodynamic efficiency is a measure of how well it performs compared to an [[Physics:Isentropic process|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).<ref name="Lancaster"/> 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''.<ref name="Lancaster"/> 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".<ref name="tfcbooks"/> This paper states:

{{blockquote
|With proper use of the analytical results, the rotor efficiency using laminar flow can be very high, even above 95%. However, to attain high rotor efficiency, the flowrate number must be made small which means high rotor efficiency is achieved at the expense of using a large number of disks and hence a physically larger rotor. For each value of the flow rate number, there is an optimum value of the Reynolds number for maximum efficiency. With common fluids, the required disk spacing is dismally small causing [rotors using] laminar flow to tend to be large and heavy for a prescribed throughflow rate.

Extensive investigations have been made of Tesla-type liquid pumps using laminar-flow rotors. It was found that overall pump efficiency was low even when rotor efficiency was high because of the losses occurring at the rotor entrance and exit earlier mentioned.

|<ref name="Rice"/>{{rp|4}}
}}

Modern multiple-stage bladed turbines typically reach 60–70% efficiency, while large steam turbines often show turbine efficiency of over 90% in practice. [[Physics:Volute (pump)|Volute]] 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.<ref name="Rice"/>

==Applications==
thumb|A Tesla turbine with the top removed

Tesla's patents state that the device was intended for the use of [[Physics:Fluid|fluid]]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<ref name="discflo"/> and is used to pump fluids that are abrasive, viscous, shear sensitive, contain 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 [[Physics:Materials science|material characteristics]] and behaviors at high [[Physics:Temperature|temperature]]s. The best [[Chemistry:Metallurgy|metallurgy]] 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 [[Physics:Compressed air|compressed air]], or [[Engineering:Steam turbine|steam as the power source]] (the steam is generated with heat from fuel combustion or [[Physics:Solar energy|solar radiation]]). Disc warping has been ameliorated by using new materials such as carbon fiber.

One proposed application for the device is a [[Engineering:Pump|waste pump]], in factories and mills where normal [[Engineering:Stator|vane]]-type [[Physics:Turbine|turbine]] pumps typically become fouled.

Applications of the Tesla turbine as a multiple-disk centrifugal [[Medicine:Ventricular assist device|blood pump]] have yielded promising results due to the low peak shear force.<ref name="Miller-Etter-Dorsi"/> [[Medicine:Biomedical engineering|Biomedical engineering]] research on such applications has continued into the 21st century.<ref name="Manning-Miller"/>

The device functions as a pump if a similar set of disks and a housing with an [[Involute|involute]] 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, then exits at the periphery. The Tesla turbine does not use friction in the conventional sense, rather using adhesion (the [[Physics:Coandă effect|Coandă effect]]) and [[Physics:Viscosity|viscosity]] instead. It uses the boundary-layer effect on the disc blades.

==History==
The turbine was patented by [[Biography:Nikola Tesla|Nikola Tesla]] on October 21, 1913.<ref name="US patent|1061206"/> It was his 100th patent.<ref>{{Cite patent|number=US1061206A|title=Turbine|gdate=1913-05-06|invent1=Tesla|inventor1-first=Nikola|url=https://patents.google.com/patent/US1061206/en}}</ref> 

==See also==
* List of Tesla patents
* [[Engineering:Radial turbine|Radial turbine]]
* [[Organization:Tesla coil|Tesla coil]]

==References==
{{reflist|refs=
<ref name="US patent|1061206">{{US patent|1061206}}.</ref>
<ref name="Miller-Sidhu-Fink-Etter">{{Cite journal|doi=10.1111/j.1525-1594.1993.tb00599.x|last1=Miller|first1=G. E.|last2=Sidhu|first2=A|last3=Fink|first3=R.|last4=Etter|first4=B. D.|year=1993|title=July). Evaluation of a multiple disk centrifugal pump as an artificial ventricle|journal=Artificial Organs|volume=17|issue=7|pages=590–592|pmid=8338431}}</ref>
<ref name="Miller-Fink">{{Cite journal|doi=10.1046/j.1525-1594.1999.06403.x|last1=Miller|first1=G. E.|last2=Fink|first2=R.|year=1999|title=June). Analysis of optimal design configurations for a multiple disk centrifugal blood pump|journal=Artificial Organs|volume=23|issue=6|pages=559–565|pmid=10392285}}</ref>
<ref name="Our Future Motive Power">Nikola Tesla, "''[http://www.tfcbooks.com/tesla/1931-12-00.htm Our Future Motive Power]''".</ref>
<ref name="patent-1061206">{{cite web|url=https://teslauniverse.com/nikola-tesla/patents/us-patent-1061206-turbine|title=TESLA patent 1,061,206 Turbine}}</ref>
<ref name="rexresearch">[http://www.rexresearch.com/teslatur/turbine2.htm Nicola Tesla in British Patent 179,043] on RexResearch.</ref>
<ref name="Titanic">Titanic: Building the World's Most Famous Ship By Anton Gill, P121</ref>
<ref name="Wilson">The Design of High-Efficiency Turbomachinery and Gas Turbines, David Gordon Wilson, P.15</ref>
<ref name="Denton">{{Cite journal|doi=10.1115/1.2929299|last1=Denton|first1=J. D.|year=1993|title=Loss mechanisms in turbomachines|url=https://turbomachinery.asmedigitalcollection.asme.org/article.aspx?articleid=1464386|journal=Journal of Turbomachinery|volume=115|issue=4|pages=621–656}}</ref>
<ref name="Stearns">Stearns, E. F., "''[http://www.lindsaybks.com/arch/turbine/ The Tesla Turbine] {{webarchive|url=https://web.archive.org/web/20040409144851/http://www.lindsaybks.com/arch/turbine/|date=2004-04-09}}''". Popular Mechanics, December 1911. (Lindsay Publications)</ref>
<ref name="Aquila">Andrew Lee Aquila, Prahallad Lakshmi Iyengar, and Patrick Hyun Paik, "''The Multi-disciplinary Fields of Tesla''; [http://www.nuc.berkeley.edu/dept/Courses/E-24/E-24Projects/Aquila/BladelessTurbine.htm bladeless turbine] {{webarchive|url=https://web.archive.org/web/20060905163353/http://www.nuc.berkeley.edu/dept/Courses/E-24/E-24Projects/Aquila/BladelessTurbine.htm|date=2006-09-05}}". nuc.berkeley.edu.</ref>
<ref name="Lancaster">"''[http://www.teslaengine.org/images/teba15p17.pdf Debunking the Debunker, Don Lancaster Again Puts His Foot In]''", Tesla Engine Builders Association.</ref>
<ref name="tfcbooks">"''Interesting facts about Tesla''" Q&A: [http://www.tfcbooks.com/teslafaq/q&a_033.htm I've heard stories about the Tesla turbine that cite a figure of 95% efficiency. Do you have any information regarding this claim? And, why haven't these devices been utilized in the mainstream?]. 21st Century Books.</ref>
<ref name="Rice">Rice, Warren, "[http://www.gyroscope.com/images/teslaturbine/TeslaTurboMachinery.pdf Tesla Turbomachinery]". Conference Proceedings of the IV International Tesla Symposium, September 22–25, 1991. Serbian Academy of Sciences and Arts, Belgrade, Yugoslavia. ([[PDF]])</ref>
<ref name="discflo">[http://www.discflo.com/history.htm Discflo Disc Pump Technology] {{webarchive|url=https://web.archive.org/web/20090214220002/http://www.discflo.com/history.htm|date=February 14, 2009}}</ref>
<ref name="Miller-Etter-Dorsi">{{Cite journal|doi=10.1109/10.46255|last1=Miller|first1=G. E.|last2=Etter|first2=B. D.|last3=Dorsi|first3=J. M.|year=1990|title=February). A multiple disk centrifugal pump as a blood flow device|journal=IEEE Trans Biomed Eng|volume=37|issue=2|pages=157–163|pmid=2312140|s2cid=1016308}}</ref>
<ref name="Manning-Miller">{{Cite journal|doi=10.1046/j.1525-1594.2002.06931_4.x|last1=Manning|first1=K. B.|last2=Miller|first2=G. E.|year=2002|title=Flow through an outlet cannula of a rotary ventricular assist device|journal=Artificial Organs|volume=26|issue=8|pages=714–723|pmid=12139500}}</ref>
}}

==Further reading==
* Tesla, Nikola, [http://www.tfcbooks.com/tesla/1911-09-18.htm "Dr. Tesla Talks Of Gas Turbines"]. Motor World. September 18, 1911.
* {{cite journal|last=Stockbridge|first=Frank Parker|date=March 1912|title=The Tesla Turbine: A Machine As Big As A Derby Hat That Generates 110 Horsepower|journal=The World's Work: A History of Our Time|volume=XXIII|pages=543–548|url=https://books.google.com/books?id=Vv--PfedzLAC&pg=PA543|access-date=2009-07-10}}
* US1061206 [http://phoenixnavigation.com/ptbc/tesla1.htm Turbine] - New and useful Improvements in Rotary Engines and Turbines
* US1329559 [http://www.tfcbooks.com/patents/valvular.htm Valvular Conduit] - Includes the Tesla gas turbine
* GB186082 [http://www.teslaengine.org/debunk/Patent1.html Improvements in the Construction of Steam and Gas Turbines] - Form of rotor
* GB186083 [http://www.teslaengine.org/debunk/Patent2.html Economic Transformation of the Energy of Steam by Turbines] - Tesla turbine system
* {{US patent|6726442}}, ''Disc turbine inlet to assist self-starting'', Letourneau (February 11, 2002)
* {{US patent|6682077}}, ''Labyrinth seal for disc turbine'', Letourneau (February 13, 2002)
* {{US patent|6692232}}, ''Rotor assembly for disc turbine'', Letourneau (March 15, 2002)
* {{US patent|6973792}}, ''Method of and apparatus for a multi-stage boundary layer engine and process cell'', Hicks (December 13, 2005)

==External links==

* [https://web.archive.org/web/20100719220042/http://www.vanderbilt.edu/dces/tesla.html Vanderbilt Tesla Turbine]
* [http://www.uncletaz.com/library/scimath/tesla/teslaturb.html Tesla turbine], from Uncle Taz Library
* [http://www.obilaser.com/AirPoweredTeslaTurbine.html Tesla Turbine Kit, Turbo-Generator], from OBI Laser Products
* [https://web.archive.org/web/20070423211602/http://freeenergynews.com/Directory/Devices/TeslaTurbine/ Tesla Turbine] featuring the work of Ken Rieli and others
* [http://www.phys.washington.edu/users/sbtroy/Tesla_Turbine/Tesla_Turbine.html Building a Tesla turbine using hard disk platters] {{Webarchive|url=https://web.archive.org/web/20140218013900/http://www.phys.washington.edu/users/sbtroy/Tesla_Turbine/Tesla_Turbine.html|date=2014-02-18}}
* [http://www.gyroscope.com/images/teslaturbine/TeslaTurboMachinery.pdf Rice, Warren, "''"Tesla Turbomachinery''." Proc. IV International Nikola Tesla Symposium, Sept. 23-25, 1991]
* [http://www.sredmond.com/disk_turbine.htm Redmond, Stephen, "''Building a Disk Turbine''"]
* [http://www.frankgermano.net/index.htm Germano, Frank D., "''Tesla's Bladeless Boundary Disk Turbine and Pump''"] 
* [http://www.stanford.edu/~hydrobay/lookat/tt.html Swithenbank, Alan, "''The Tesla Boundary Layer Turbine''"]
* [http://www.tfcbooks.com/articles/tdt7.htm#materials Peterson, Gary, ''Nikola Tesla's Disk Turbine''] Tomorrow's Gas Engine. Feed Line No. 7
* [https://web.archive.org/web/19981203123145/http://naca.larc.nasa.gov/reports/1953/naca-report-1124/ Boundary Layer Effect]
* [https://www.pbs.org/tesla/ll/pv_gen_pop.html "''Tesla turbine''" from PBS


[[Category:Turbines]]
[[Category:Boundary layers]]
[[Category:Mechanical devices using viscosity]]

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