Geometry, Working and Application of Tesla Turbine

A bladeless turbine called Tesla turbine comprised of a sequence of Nozzle discs from which gas or liquid flows to the disc edge. Related to fluid properties of viscosity and adhesion, momentum transformation among fluid and disc occurs. Discs and washers are mounted on a sleeve with individual discs, fixed at the top, and nuts are used to keep dense top plates intact. There is a void in the sleeve which fits tightly onto the shaft. To connect with exhaust ports founded on the edge of the casing, holes are carved out across the middle of the discs. Therefore, a multi-disk tesla turbine is known as a shear force or secondary flow turbo equipment that operates with compressible and incompressible fluid. Fluid arrives radially then through the channels exits axially. The benefits of the Tesla turbine are ease of development, flexibility and low servicing. Vapor or water can be the fluid used. Owing to the absence of vanes, it is untouched by sediment erosion. Low performance is a problem associated with Tesla turbines. For optimum configuration, the Tesla turbine states higher torque performance, yet quantitatively several complexities were identified in achieving high productivity gains in nozzles and rotors. 

 

Figure 1 Tesla Turbine

In 1903, Nikola Tesla invented the Tesla Turbine. The turbine was using 22.5 cm disc, and the complete rotor was 5 cm thick, generating 110 horsepower, and steam is the percussive fluid. In 1909, the Tesla pump was invented using smooth spinning discs on volute casing. Between 1906 and 1914, Tesla carried out experiments with his turbine, but then there were few developments in this field until a resurgence of interest started in the beginning of 50s (Matej, 1993). 

Geometry of Tesla Turbine

The Tesla turbines are made up of rigid flat disk type rotors usually mounted on a revolving shaft parallel to each other. The disk thickness should be minimum as per theory.  Thin spacers are used to provide passage for movement of fluid among each disk. Spacers could either be disk-shaped or they can be constructed of thin magnets of cylindrical shape. In the latter case, the spacers are arranged in a round pattern about the point of entry. In this case, they are a cause of disturbance to the entering flow. It is pertinent to highlight that, after the commencement of motion of whole pack, there might be insignificant motion between spacers and disks. Rice [9] noted that, the maximum efficiency is obtained when the gaps are approximately two times the thickness of boundary layer. The existing flow situations and the working fluid’s physical properties are the deciding factors of the gap between the disks. Other factors upon which the gap depends upon are; the strength of material, manufacturing technology and assembly. The spacer assembly and the disk bank are shown in Figure below. 

 

Figure 2 Tesla Turbine Geometry

The assembly and the disk bank are locked together by a nut, which in turn is fastened by thread at one end shaft and on the other end it is fastened to a sleeve integrated into the shaft. The shaft, on both ends, is inserted into radial bearings. Bearings seats are used alongside radial bearing for smoother operation and are a part of external casing. The fluid is introduced into the row of blades using nozzle exit. The supply nozzles are positioned across the circumference. The nozzles placed at a specific angle with the disk’s tangent. When the nozzles are placed in opposing directions, the direction of rotation is defined by selecting the specific nozzle which needs to be rotated in a specific direction. The turbine’s performance depends strongly upon the nozzle efficiency and interaction of rotor and nozzle (Warren Rice, 1991).

Working Principle of Tesla Turbine

The fluid arrives in the chamber in the tangential direction through the inlet and travels over the disk surface through the spacing of the disk. Momentum exchange between discs and fluid takes place because of viscosity. Energy transfer between disc and fluid decreases the fluid velocity and it travels toward exhaust due in a spiral manner. As there are no projections on the rotor, it is quite durable. Flat discs that have exhaust ports close to their centers are piled up on a shaft and have thin spacers between them. By directing any fluid (air, exhaust gas or water) between them, these discs are rotated due to the development of fluid boundary layer on the surface of the disks which pushes them around when the fluid arrives in from the disk’s outer edge and move outwards from the central vent holes. The working fluid starts moving in lengthier spiral paths due to greater centrifugal force as disks begin to rotate and their velocity increases. Some part of the energy of fluid is converted into mechanical work by this phenomenon, resulting in the rotation of the shaft and disk.

Application of Tesla Turbine

Application of this system is typically in the narrower power ranges for turbines and compressors. This device has applications in compressing the slurries and fluids having significantly abrasive, solid, viscous, sensitive shear or in other words, any fluids which are hard to manage with centrifugal or vane pumps. Miller (1992) demonstrated successfully that the Tesla pump can be used in the human heart as an artificial ventricle. As the Tesla pump does not have a valve, voltage control of a DC drive motor can operate the pump in pulsating mode. Valente (2008) reported that the Tesla turbine could be successfully used for the reducing the pressure of hydrocarbon gases in gas liquefaction plants. We can liquefy Hydrocarbon gases almost isothermally with the integration of Tesla Turbine in liquefaction series. The ability of Tesla turbine for exploiting wind energy has been recognized in the recent years. In order to generate lift and apply more torque to the spinning shaft, the design incorporates a spacer of airfoil shape near the perimeter of the disk (Fuller 2010).

The general fields of use of Tesla turbo machinery are listed below.

• Power plants fueled by biomass

• Heat recover installations

• Systems using co-generation technology

• Solar energy systems

• Systems using exhaust heat

• Low-temperature geothermal medium plants 

Several other uses that use the concepts of the Tesla turbine are air motor motors, dentist drills, air compressors, vacuum exhausters and small expandable arms propulsion systems i.e. torpedoes.