Tesla turbine.....

                     

Report : Tesla Turbine       

        Introduction:-

           The job of any engine is to convert energy from a fuel source into mechanical energy. Whether the natural source is air, moving water, coal or petroleum, the input energy is a fluid. And by fluid we mean something very specific -- it's any substance that flows under an applied stress. Both gases and liquids,As we can use  liquid water and gaseous water, or steam, function as a fluid.                                

          At the beginning of the 20th century, two types of engines were there that was common: bladed turbines, driven by either moving water or steam generated from heated water, and piston engines, driven by gases produced during the combustion of gasoline. The former is a type of rotary engine, the latter a type of reciprocating engine. Both types of engines were complicated machines that were difficult and time-consuming to build.

         Consider a piston as an example. A piston is a cylindrical piece of metal that moves up and down, usually inside another cylinder. In addition to the pistons and cylinders themselves, other parts of the engine include valves, cams, bearings ,and rings .some time each part could be a cause of failure  And, due to their weight it will directly  effects  of efficiency of engine.

Bladed turbines have moving parts, but they have their own problems. Most of the parts are very small and made with accurate tolerance. If not built properly, blades could break or crack.

Tesla's new engine was a bladeless turbine, which use a fluid as the vehicle of energy.

2. Literature review :

             Tesla had several machines built. The first, built in 1906, have eight disks, each 15.2 centimeters in diameter. The machine weighed less than 4.5 kilograms and developed 30 horsepower. The rotor attained such high speeds -- 35,000 revolutions per minute (rpm) -- that the metal disks stretched considerably, hampering efficiency.

                In 1910, Czito and Tesla built a larger model with disks 30.5 centimeters in diameter. It rotated at 10,000 rpm and developed 100 horsepower.

                Then, in 1911, the pair built a model with disks 24.8 centimeters in diameter. This reduced the speed to 9,000 rpm but increased the power output to 110 horse

Bolstered by these successes on a small scale, Tesla built a larger double unit, which he planned to test with steam in the main powerhouse of the New York Edison Company. Each turbine had a rotor bearing disks 18 inches (45.7 centimeters) in diameter. The two turbines were placed in a line on a single base. During the test, Tesla was able to achieve 9,000 rpm and generate 200 horsepower. However, some engineers present at the test, loyal to Edison, claimed that the turbine was a failure based on a misunderstanding of how to measure torque in the new machine. This bad press, combined with the fact that the major electric companies had already invested heavily in bladed turbines, made it difficult for Tesla to attract investors.

                     In Tesla's final attempt to commercialize his invention, he persuaded the Allis-Chalmers Manufacturing Company in Milwaukee to build three turbines. Two had 20 disks 18 inches in diameter and developed speeds of 12,000 and 10,000 rpm respectively. The third had 15 disks 60 inches (1.5 meters) in diameter and was designed to operate at 3,600 rpm, generating 675 horsepower. During the tests, engineers from Allis-Chalmers grew concerned about both the mechanical efficiency of the turbines, as well as their ability to endure prolonged use. They found that the disks had distorted to a great extent and concluded that the turbine would have eventually failed.

        

3. Theoretical Analysis and Construction:-

There are mainly 2 parts in the turbine.

3.1 Rotor:-

                  In the rotor it consists of series of smooth discs mounted on a shaft. Each disk is made with openings surrounding the shaft. These openings act as exhaust ports through which the fluid exits.  Washers are used as Spacers; the thickness of a washer is not to exceed 2 to 3 millimeters.

                                        Fig no.3.1

          

3.2  Stator :-

               The rotor assembly is housed within a cylindrical stator, or the stationary part of the turbine. Each end of the stator contains a bearing for the shaft.  

The stator also contains one or two inlets, into which nozzles are inserted, which allows the turbine to run either clockwise or counterclockwise. To make the turbine run, a high-pressure fluid enters the nozzles at the stator inlets. The fluid passes between the rotor disks and causes the rotor to spin. Eventually, the fluid exits through the exhaust ports in the center of the turbine.

3.3  Working Principle:-

          Adhesion and viscosity are the two properties of any fluid, these two properties work together in the Tesla turbine to transfer energy from the fluid to the rotor or vice versa.

                   1. As the fluid moves past each disk, adhesive forces cause the fluid molecules just above the metal surface to slow down and stick.

        2. The molecules just above those at the surface slow down when they collide with the molecules sticking to the surface.

Fig no.3.3

3. These molecules in turn slow down the flow just above them.

4. The farther one moves away from the surface, the fewer the     collisions affected by the object surface.

5. At the same time, viscous forces cause the molecules of the fluid to resist separation.

6. This generates a pulling force that is transmitted to the disk, causing the disk to move in the direction of the fluid.

                The thin layer of fluid that interacts with the disk surface in this way is called the boundary layer, and the interaction of the fluid with the solid surface is called the boundary layer effect. As a result of this effect, the propelling fluid follows a rapidly accelerated spiral path along the disk faces until it reaches a suitable exit

With proper use of the analytical results, the rotor efficiency using laminar flow can be very high, even above 95%.

4. Advantages:-

• Simple in construction.
• Corrosion and cavitation is less.
• Pollution free.
• Low cost to produce and maintain.
• Lower design and production costs than standard turbines, jet engines and pumps
• Blade-less
• High-speed (100,000rpm+ be achieved with some versions)
• Low friction (uses boundary layer effect , adhesion + viscosity rather friction)
• Reversible
• Can be run on a vacuum
• Can be powered by air, steam, gasses or liquids
• Proven technology (but rarely used)
• Lower complexity the conventional Jet Engine
• Can be used as a pump by rotating the shaft
• Quieter in operation than conventional machinery
• Noise is more ‘white’
• 2 stage or multi stage versions can run on combustible gas/liquids (Just like a jet engine)
• This type of equipment can be operated at a wide range of working medium parameters without any danger and malfunction.
• It is not so sensitive to a partially polluted working medium, since the fluid flow is parallel to disks, so it can be operated with saturated steam.
• This turbine can be adjusted to different circumstances by applying a few cross sections have to be adjusted to the actual demand which is an interchangeable part of the equipment.

5. Disadvantages:-

• Low rotor torque
• Often not suitable for a direct replacement for conventional turbines and pumps, without changes to the machinery it is interacting with.
• Proof of its efficiency compared to conventional turbines is still questionable and needs more research
• It has remain underdeveloped and hence design improvements are still being made

6. Applications:-

• Tesla turbine has not seen widespread commercial use since its invention.
• The Tesla pump, however, has been commercially available since 1982 and is used to pump fluids that are abrasive, viscous, contain solids, shear sensitive or otherwise difficult to handle with other pumps.

Applications of the Tesla turbine as a multiple-disk centrifugal blood pump have yielded promising results. Biomedical engineering research on such applications has been continued into the 21st century.

7. Future of the turbine:-

• Tesla’s ultimate goal was to replace the piston combustion engine with a much more efficient, more reliable engine based on his technology.

8. Predicted Results and Discussions:-

                   The turbine efficiency of the gas Tesla turbine is estimated to be above 60, reaching a maximum of 95 percent. Keep in mind that turbine efficiency is different from the cycle efficiency of the engine using the turbine. Axial turbines which operate today in steam plants or jet engines have efficiencies of about 60 - 70 % .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 efficiency. Tesla claimed that a steam version of his device would achieve around 95 percent efficiency .The methods and apparatus for the propulsion of fluids and thermodynamic transformation of energy were disclosed in various patents. The

href="http://en.wikipedia.org/wiki/Thermodynamic_efficiency" style="text-decoration-line: none;">thermodynamic efficiency 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. This can be taken to be the ratio of the ideal change in enthalpy to the real enthalpy for the same change in pressure.

9. Design and Analysis of Prototype Tesla Turbine for Power Generation Applications

                 Tesla turbine implementation as a non-conventional energy resource.

                                          Fig no.9

9.1 Material and methods
        The most important part of the tesla turbine is the rotor (shaft discs) and the             nozzle. Material selection for these parts is of the extreme importance .Table 1 illustrates the various elements of tesla turbine. Ten aluminum discs with 9 spacers of 0.5mm & 16 washers of 5/16'' were used as a series of discs in rotor of tesla turbine.
                                                

                                                     Table I

Parts	quantity
Plexi glass sheet	2
Collars	2
Aluminum  shaft	1
Ball bearing	2
Plastic pipe	1
Nut bolts	8
Cylinder	1
Rubber hose	2

9.2 Design of Tesla Turbine :

                   The important criterion used in the tesla turbine was the designing of rotor, shaft, stator, nozzle. In rotor's designing, a number of discs with same diameter (6 inch) and thickness (2mm) were mounted on a shaft and fixed with a very fine spacing (0.3-0.5mm) between each two. The nozzle slot, compared to the overall width of the rotor, was narrower i.e. the number of the active discs must be less in number than the total discs.

             For this case turbine with 25 discs, have 23 active discs including the disks with thicker ends. In order to attain more efficiency and overcome losses, nozzle with platinum chamber can be experimented.inlet, losses could be controlled. The Propelling fluid get pass the outer most active discs.

          The assembly of rotor was housed inside a cylindrical stator, or within the stationary part of the turbine. In order to house the rotor, the interior format diameter was slightly larger in size than the discs of rotor. Ball bearing for the shaft at each end of the stator was used. Two inlets were contained by the stator, in which nozzles were inserted.

9.3 Tesla Turbine Prototype:

A Tesla Turbine prototype was designed as shown in Fig. 4. This prototype model consists of various parts such as stator, stator outlets, rotor discs, exhaust port and shaft.

   

nbsp;                                                               Fig no.9.3

9.4   Working Principle :

            The principle of Boundary Layer (BL) was use for the working of Tesla Turbine (TT). According to this principal, molecules which are right next to the surface, stick to the surface as the fluid moves past each disc surface. Those molecules which follow the surface, stick to it and are slowed down in their collision to the molecules..

        

Fig no. 12.1

These  molecules in results slowdown the flow which is just above them. As these molecules move away from these surfaces, the chances of their collisions are reduced with the object surface. Meanwhile, due to viscous forces, the molecules of the fluid resist for separation. These forces become prominent over the inertial forces. This will produce a pulling force that is transferred or moved to the disk, which causes the

Disk rotate in the direction of fluid

   

                                                       fig no. 12.2

10.  Results and discussion :

                  The stator of Tesla turbine contains two or more inlets for nozzles. Through nozzles compressed air at about 272 kPa enters rotor discs results to spin rotor which was coupled with generator and gives output. A tube light of 40 watt was tested and different parameters such as voltage, current and power were observed.

10.1 Power Outcome

               Power obtained from tesla turbine was analyzed on different speeds. The result shows that the power increased with the increase of speed of rotor of the tesla turbine. There is direct relation between power and number of rotation. Fig. 5 shows the power at different speeds of the turbine. It can be observed that at 1000 rpm power obtained is 16.5 watt which increases linearly by increasing speed

                                        fig no. 10.1

      

10.2 Relation between Voltage & Speed :-

                        Fig . 6  depicters the relationship between the voltage and the speed. It is clear that there is almost linear relation between voltage and rpm. As speed decreases from 2230 to 1000 rpm voltage also declined from 14 to 11 volts. Solid line shows the actual behavior while dotted line shows linear relation. There is slight more variation of voltage comparatively at speed of 2000 rpm but still the relationship is linear.

                                             

                                                             Fig no .10.2    

   

10.3 Comparison of Efficiency:-

             Among different turbines Three key efficiency points of this turbine are inlet nozzle, disc geometry and the outlet. Disk geometry means the use of compatible material with quite perfect spacing and the accurate number of positions of dividers. Between discs, space must be from 0.032 inch to 0.125 inch. High torque and low horsepower was developed due to narrow spacing and vice versa. Two major functions are performed by inlet nozzle.

            It transforms gas pressure into the gas kinetic energy and converts the kinetic energy, in parallel streams, into the rotor (turbine disk pack). Figure 8 illustrates comparison of efficiencies of different turbines. The efficiency of bladed turbine is 22 percent and the efficiency of tesla turbine is 58 percent. Among all turbines, Tesla has maximum efficiency where as other turbines like Bladed, Gas Piston, Diesel and Fuel Cell are less in efficiencies of about 22%, 32%,42% and 45% respectively.

           It clearly depicts that using Tesla disc turbines could bring more work output by utilizing maximum energy for running turbine. Conventional turbines are mostly reaction and impulse type or both.

Tesla turbine is an unconventional turbine that uses fluid properties such as boundary layer and adhesion of fluid on series of smooth disks keyed to a shaft.

                                                                   fig no. 10.3

11. References:-

1. V. D Romanin and V. P Carey. “An integral perturbation model of flow and momentum transport in rotating micro channels with smooth or micro structured wall surfaces”. Physics of fluid, 23(2011
2. V. G. Krishnan, Z. Iqbal and M.M Maharbiz “A micro tesla turbine for power generation from low pressure heads and evaporation driven flows”. pp. 1851-1854, (2011).
3. A. Guha and B. Smiley. “Experiment and analysis for an improved design of the inlet and nozzle in tesla disc turbines”. pp. 261-277, 224 (2010). [vi] G. P. Hoya and A. Guha. “The design of test rig and study of performance and efficiency of a Tesla disc turbine”. pp. 451-465, 223 (2009).