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The Tesla turbine is a bladeless centripetal flow turbine patented by Nikola Tesla in 1913. It is referred to as a bladeless turbine because it uses the boundary layer effect and not a fluid impinging upon the blades as in a conventional turbine. The Tesla turbine is also known as the boundary layer turbine, cohesion-type turbine, and Prandtl layer turbine (after Ludwig Prandtl). Bioengineering researchers have referred to it as a multiple disk centrifugal pump.
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, therefore, are fluids, which can be exemplified by water. As far as an engineer is concerned, liquid water and gaseous water, or steam, function as a fluid.
At the beginning of the 20th century, two types of engines were 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, gaskets and rings. Each one of these parts represents an opportunity for failure. And, collectively, they add to the weight and inefficiency of the engine as a whole.
Bladed turbines had fewer moving parts, but they presented their own problems. Most were huge pieces of machinery with very narrow tolerances. If not built properly, blades could break or crack.
Tesla's new engine was a bladeless turbine, which would still use a fluid as the vehicle of energy, but would be much more efficient in converting the fluid energy into motion.
Tesla had several machines built. Juilus C. Czito, the son of Tesla's long-time machinist, built several versions. The first, built in 1906, featured eight disks, each six inches (15.2 centimeters) in diameter. The machine weighed less than 10 pounds (4.5 kilograms) and developed 30 horsepower. It also revealed a deficiency that would make ongoing development of the machine difficult. 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 12 inches (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 9.75 inches (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.
Even as late as the 1970s, researchers had difficulty replicating the results reported by Tesla. Warren Rice, a professor of engineering at Arizona State University, created a version of the Tesla turbine that operated at 41 percent efficiency. Some argued that Rice's model deviated from Tesla's exact specifications. But Rice, an expert in fluid dynamics and the Tesla turbine, conducted a literature review of research as late as the 1990s and found that no modern version of Tesla's invention exceeded 30 to 40 percent efficiency. This, more than anything, prevented the Tesla turbine from becoming more widely used.
Objectives of the experiment: -
According to Nikola Tesla, the three key efficiency points of his turbine are:
• The inlet nozzle
• Disk geometry
• The outlet nozzle
Experimental works aimed first of all at establishing relationships between the turbine efficiency and parameters given below:
• Distance between the turbine disks
• Number and diameter of the turbine disks
• Number of inlet nozzles to the turbine
• Rotational speed of the rotor
• Inlet pressure
• Inlet temperature
• Inlet velocity and inlet angle
• Corrosion and erosion of turbine elements
• Constructional materials (composites, ceramic
materials, bronzes, aluminum alloys)
• Kind of medium flowing through the turbine
(air, biogas, organic agents, exhaust gases, multiphase
Proposed Experimental Programme / Theoretical Analysis:-
There are mainly 2 parts in the turbine.
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.