1.1 Problem Summary
Nikola Tesla invented this bladeless turbine (patented 1913) originally, which uses boundary layer effect to run and not impingement of fluid upon the blades as in conventional. There are number of discs sequentially mounted on a shaft and the fluid is made to flow in a tangential direction with considerable pressure onto the discs with the help of convergent nozzles, then follows a spiral path towards the center and exits axially. The discs rotate due to the very properties of the fluid – viscosity and adhesion, as momentum is transferred via this forces and kinetic energy of fluid is converted into the rotational energy of the shaft. Many researchers have studied this concept and given various improvements with proofs basically into two ways – one suggesting modifying the design of various components involved while others to change the parameters involved.
1.2 Aim and Objective:
This project is aiming to study and research the right parameters which would highly increase the performance of this bladeless turbine and also to conclude that, though, being such a beautiful invention why it haven’t made it to the commercial platform.. We are trying to study the parameters in detail on how it would affect the performance of the turbine and by changing which measurement we could improve the overall working of this Tesla turbine.
1.3 Problem Specification
Nikola Tesla invented and patented this design of turbine in 1913 and according to him this turbine is capable of achieving efficiency up to 95%.
There are several parameters on which the performance of Tesla Turbine is depended. These all parameters and their influence is shown below:
Number of Disks: There is a direct relation between the number of disks and performance. By increasing the number of disks, torque increases and hence more efficient performance.
Size of the gaps between disks: The thickness of the gap according to theory should be equal to twice the boundary layer thickness.
Number of nozzles: The torque obtained will be increased if the number of nozzles is increased.
Reynolds number: The laminar boundary layer thickness depends upon the Reynolds number.
Velocity of the flow: The velocity of the fluid causes the kinetic energy which is transferred in the turbine.
1.4 Literature Review
The foremost patent for the design was registered by the Nikola Tesla in 1913 which led to a great revolution in turbo machinery sector. After that not much research was done in this area until 1950 but after that a revival of interest was seen.
Tesla’s work has been characterized by a number of researchers among which Rice’s analysis was the first and he claimed certain parameters which could improve the performance. He constructed a six disks turbine and did experiments on it. Later he suggested some solutions like to reduce the gaps between the disks, some changes in the supersonic nozzle and its angle. Rice observed a max efficiency of about 24% through his experimentation.
K.Boyd and Rice studied the incompressible flow nature between the rotating disks and proposed a solution for the inlet conditions. This complete formulated statement is being on based of Navier Stoke’s equation and relies on the flow rate, tangential velocity and Reynolds number.
Ho-Yan and Lawn claims that they can make this turbine work to reach 70% efficient.
Micro turbine designs were tested and verified by Hoya, Guha, and Smiley who claimed 25% efficiency by computational models and analysis.
Though a large body of history does not exist for the micro inertial turbines but some of the experiments were done by Epstein, Herrault, Jan Peirs, and Camacho who confirmed the systems which do operate between 100k and 1M rpm at power densities a full order higher compared with larger versions of the same.
As the size of the turbines becomes smaller, the frictional considerations become an important factor and it should be determined accurately.
The surfaces that have a relative roughness higher than 0.05, value of flow constriction becomes important which was argue by Kandlikar et al. He was able to do that by modifying the original moody diagram.
Gumrat reported that Poiseuille number increases with surface roughness and also providing the detailed summary of the previous work.
The vast majority of the experimental results published utilize air as the working fluid. It is the author’s opinion that the best opportunity for the Tesla turbine to gain significance would be related to steam or particulate laden fluid applications. In particular, low quality steam power generation would be an ideal situation. There is a definite lack of published experimental data where the working fluid is steam of any quality.
Nikola Tesla also invented a machine for propelling energy to fluid by a combination of plularity of the discs enclosed is a volute casing, port of inlet at the central portion while outlet at the periphery.
Though, the development relating to the nozzle inlets was given by Stocklinger in 2012 and possell in 1978 as part of a larger generation system by Bohl in2012, Foulton and Taylor in 1974.
Also, an arrangement of turbine/pump and various modifications to the inlet edges of the disks by Conrad & Conrad in 2001 and Fuller in 2010.
Disc turbines which used heat pipes to dissipate the heat and thereby increase the efficiency was proposed by William W. Cochran.
This boundary layer turbine can also be used in Internal Combustion Engine in replacement of conventional reciprocating engine also outruns it in every parameter.
Also, Simon Higgins proposed that if the discs comprised more friction by making raised spiral edges on its surface then its efficiency can be improved.
Turbo-machinery and methods are disclosed for a bladeless Tesla conical radial turbine wherein fluid is directed axially within Tesla the pump body to produce an axial output as given by Salvatore F. Grande The rotor comprises a plurality of spaced apart conical elements.
Robert D. Saunders suggested slotted bladeless turbine disc stamped or otherwise formed from a single solid sheet of material With slots formed in the disc to redirect fluid passing through it is disclosed.
Salvatore F. Grande and David R Draper modified the shape shape of the disc to a conical one in order to achieve more efficiency.
Considerable Designs from Literature:
As mentioned earlier the first of the designs were given by Nikola Tesla, after which the primary inspections occurred in 1950 and 1960s.
Later, E.W. Beans (1961), and another PhD thesis, authored by R.C. North (1969).
These should be considered the primary set of designs, as later designs are very similar to these.
(Fig 1.1 Leaman’s Design)
The first appearance of this feature with central exhaust was seen in 1950 by Leaman.
The turbine used 4.6” (.126 m) discs, with a maximum inlet pressure of 85 psi (5.8 bar).
The efficiency was attained 8.24% at the rpm of 9,000.
In his design, Leamanhad slightly different approach for the affixing of the discs from Tesla’s original concept, where the exhaust was delivered to a central cavity, and the shaft was slotted to allow for the exhaust flow to pass.
He used various surface textures of discs in his design, to see the effects.
He found that the smooth discs performed slightly better than rough discs.
(Fig 1.2 Armstrong’s Design)
Armstrong built a steam turbine which made several modifications to Tesla’s design, most notably in the profile of the discs.
To decrease the turbulence caused as the fluid entered the turbine, he made the turbine disks tapered.
He used 7” (.178 m) diameter discs, with steam at a pressure of 125 psi (8.6 bar).
The maximum speed reached with the design was 9,000 RPM, with an efficiency of only 4% in 1952.
1.4.4 Bean’s Design
(Fig 1.3 Bean’s Design)
Beans’ primary investigation was on the effects of disc spacing and on the effects of inlet pressure.
His design had two inlet nozzles, with a cantilevered bearing arrangement.
Beans’ design maintained a disc diameter of 6” (.152 m), operated at a pressure of 40 psig (2.76 bar), and a top speed of 18,000 RPM.
Beans in 1966 determined the efficiency of his turbine, under those conditions of about 24%.
1.4.5 North’s Design
(fig 1.4 North’s Design)
The early papers of North in 1969 considered a design that sought to modify the method that the fluid entering into the system.
The most remarkable change was the creation of a ‘supply chamber’, a volume at pressure, to supply a relatively large number of circumferential 26 nozzles.
The discs used in his paper were 4 7/8” in diameter (.124m), operated at an extremely low pressure of 14.5 psig (1 bar) at a maximum speed of 2,070 RPM.
North was able to achieve a maximum efficiency to be 16%.
1.4.6 Rice’s Design
(Fig 1.5 Rice’s Design)
Later work was done by students under Rice, but many of those works were not available to review, including Rice’s original thesis in 1963.
However, one of Rice’s works appeared in a Nikola Tesla Symposium in 1991, which shows an early occurrence of a hub-exhaust version, as shown in the left of Figure.
1.4.7 Hoya &Guha’s Design
In addition to the beforementioned theses, several papers were published based on the design presented in “The Design of a test rig and study of the performance of a Tesla disc turbine” by Hoya and Guha (2009), and “Experiment and analysis for an improved design of the inlet and nozzle in Tesla Disc Turbines” by Guha and Smiley (2009).
The design used is principally the same as that of Rice, but with some subtle modifications primarily concerning the nozzle. This design used discs that were 92mm in diameter, and operated at a pressure of 3.9 bar.
Maximum efficiency was measured at approaching 25%, however, that value included the frictional torque within the system.
1.4.8 Comparison of various designs:
Below, shows a comparison of the various design features and results obtained by the authors.
( Table 1.1 Comparison of various designs)
1.4.9Expected Results from the Literature:
Here, we can see from the graph that as the rpm of the turbine is increased, the torque transmission capacity of the turbine is decreased.
This result was obtained by Rice in 1965.
(Fig 1.6 graph of Torque v/s RPM)
In addition, from the below graph it can be said that as we increase the rpm continuously with the going time, it will attain a steady state value of speed after which it may not increase further.
(Fig 1.7 graph of RPM v/s time)
Now, as the angle is changed the torque with it also changes .
The greatest torque was observed when the angle was almost tangential and as it moved radially inward the torque also decreased with it consequentially.
This was observed by Romanin in 2012.
(Fig 1.8 effect of nozzle angle)
1.5 Plan of Work
(Table 1.2 Plan of Work)
All this materials depends on the application of turbine.
(Table 1.3 Materials)
A simple lathe machine with a tailstock and a dead or live center.
Drill press or Milling machine:
A set of holes are required to be drilled precisely on the platters.
CHAPTER 2: DESIGN
2.1 Design Methodology
At large power requirements, the performance of bladed turbines outruns the bladeless turbine.
However, bladeless turbines are highly efficient in small power generations.
(Fig 2.1 graph of efficiency v/s output)
According to experimental results the efficiency of bladeless turbine is found to be maximum at low power output requirements as depicted in the above graph.
Distance between the disks is needed to be very small.
In theory, the exact distance required to be maintained between the disks is the double the thickness of the boundary layer developed.
The efficiency of this turbine depends on the parameters: pressure, temperature, inlet medium velocity, number, diameter, thickness and distance between the disks as well as on the state of the disk surface, rotational speed of the rotor, flow kinematics at the inlet to and outlet from the turbine, etc.
In the subject-matter literature, examples of experimental research referring to the following models of Tesla micro- turbines can be found :
(Table 2.1 experimental output power study )
Experiments had been conducted to establish the relations among the turbine efficiency and the parameters involved:
Quantity of discs used
Inner, outer diameter kept, and thickness of the discs used
Nozzle angle and its quantuty
Whether flow is compressible or Non-compressible
Reynolds number of the flow
Jet inlet angle
The roughness of the disc
Inlet pressure and Load applied
Medium of flow and it’s type
Number of inlets provided
Placement of outlet
Type of the application
Stator, bearing, spacer and rotor sealing’s
Dynamic and Kinematic viscosity
Stagnation and static pressure
2.2 TURBINE OVERVIEW:
The main advantageous aspect of this turbine is its: simplicity in – design, manufacturing and maintenance.
These turbines are very cheap to manufacture in comparison to the bladed turbines and their various counterparts.
In general, the main point to be considered in designing these turbines is – symmetry of the disks.
As these will revolve at very high rpm, they require to be perfectly balanced, else may lead to a catastrophic failure.
2.3 General Considerations of the Disc:
Disc is the most crucial part of a Tesla turbine which should be designed very carefully.
If the discs are not parallel and at exact same distance then vibration analysis becomes an important factor.
As the overall stability and robustness of the model becomes dwindled.
Finishing of the disc also affects the efficiency of turbine. By simply increasing the roughness of the surface efficiency will increase by 5% to 7%.
(Fig 2.2 Disc)
2.4 General Considerations of the Disc Pack:
Disk pack is the foremost consideration here as it is the most critical part to be examined.
It will depend upon various parameters such as- the steam pressure generated, input nozzle velocity, spacing between them.
For instance in the case of a high pressure steam turbine, larger discs would be preferred, since the nozzle exhaust velocity would be much higher, and a larger moment would store energy in the event of a sudden load, in order to prevent excessive deceleration.
In the case for our project, however, relatively low pressure air is the working fluid, zero to low load requirements, and for ease of material sourcing and construction, the diameter of the disc pack was chosen to be 92mm – the diameter of a single 3.5” hard drive platter.
Hard drive platters were chosen since they are extremely smooth, have extremely precise dimensions, and were readily available at no additional cost.
Also the material used here is aluminum as that of platter.
If to work for higher speed and higher yield strength then more suitable materials like carbon should be selected (Bergen, 2009).
Hoya and Guha (2009) calculated the maximum allowable angular speed without plastic deformation by using the below equation:
Considering above parameters, the maximum safe rotational speed obtained is about 34,500 rpm nearly and in literature mostly found a maximum speed of 35,000 rpm, thus the platter should have no issues (Burton, 1955).
2.4.1 Disc Pack:
As earlier mentioned, the hard disk platters are used as disks here which have a 3.5” of outer diameter.
These type platters are common in every hard drives, however, some may be a little different.
For the initial design step, the hard drives will be disassembled and then the platters be measured.
Some variation, especially in the thickness can be found in the platters though most of them are identical.
(Fig 2.3 Disc Pack in assembly)
In addition, the design would include spacers between the discs, mounted on the bolts, in order to keep a consistent spacing between them.
The overall design can be adjusted somewhat by changing the thickness of the spacers, so that one can vary the gap between the discs to test the effects of so doing.
The shaft should be straight and robust for the required work.
Discs will be mounted on shaft along with spacers, and the 2 ends will be mounted on bearing which will be attached with end plates.
The center diameter will be made equal to that of the inner diameter of the hard drive platter.
The material used could be aluminum or steel, both of them prove to be of withstanding the required performance.
The shaft should now wobble around due to the vibrations produced which will but not above a certain limit.
(Fig 2.4 Shaft )
Bearings are a critical component. They needed to be compact, but also able to withstand a reasonable amount of heat, and extreme speeds.
Research on the turbine showed that it was reasonable to expect speeds in excess of 30,000 RPM, dependent on pressure.
While it was not expected that this turbine would be run at those speeds for safety concerns, it seemed appropriate to provision bearings that were capable of reaching those speeds for the purposes of further study.
SKF bearings were chosen because of the company’s high quality standards, large selection, and effective online tools for determining the proper bearing based on the various criteria of the system.
They must be capable of very high speeds. Most bearings are not designed to exceed a few thousand RPM, and it is very reasonable to expect that the Tesla Turbine can exceed 25,000RPM. Examples exist in the literature of speeds in excess of 35,000RPM (Burton, 1955). Therefore, the choice of bearings was limited to those that could easily handle these speeds, or greater.
They must be of high quality, and the bearings should be sealed. Since it was not desirable to include an oiler in the system, and also ensure that the disc pack and exhaust flow was not contaminated, sealed bearings were a clear choice.
(Fig 2.5 Ball Bearing)
2.7 End plates and Casing
End plates and casing makes closed air tight chamber which will make an closed chamber which will give direction to the flow.
The casing of turbine is cylindrical in shape. The rotor of the turbine rotates in this cylindrical casing which is of slightly larger diameter then the disks of the rotor
(Fig 2.6 End plate)
(Fig 2.7 casing)
2.8 Final Assembly
All the components will be assembled together to form a turbine.
(Fig 2.8 Final assembly A)
(Fig 2.9 Final assembly B)
This section includes the details on various canvas which helps to identify the potential
users and applications of the product as well as to known the activities performed by the
device. It also includes the various components that are used in the device.
2.9.1 AEIOU summary canvas
2.9.2 Empathy Mapping Canvas
2.9.3 Ideation Canvas
2.9.4 Product Development Canvas
2.9.5 AEIOU summary canvas
As shown in the figure, this section contains the details of the activities that are going on in the product to give the maximum benefit. It includes pressurizing the fluid, impinging it on the discs, rotation of discs and outlet of the fluid from the central portion generating power.
It includes the factors which are favorable for the product, where it is mostly used
& the effect of this factor on the product and the environment or surrounding. The size of this turbine is compact and its take a minimal place. Also, it has no fumes coming out and has least mechanical parts. It can be utilized easily in any low power requirements with greatest efficiency.
In this section it states the interactions which are held in the product for better
function of turbine. It is seen that in order to work successfully each of the element interact directly or indirectly to the person operating the turbine. The pressurized fluid is supplied to the inlet of the turbine and hence the process takes inside the turbine quietly without much outside interference, except for the maintenance work.
The users of this turbine are mainly the universities and meager companies using it as its still in a development stage. Some users which are intend to use it are as follows:
It includes the process which are held by the Bladeless Turbine and the flow of the activities going on in the product as
-Pressurizing the fuild
-Directing forcefully it on the discs
-Rotation of the discs
-Generation of power
It includes the one which are using the product and getting the benefit of it to
fulfill their needs.
- Power plants
-Students and researchers
It includes the elements in the product which are beneficial for the effective
working of turbine such as
-Multi specialty hospitals
-Internal Combustion Engines
EMPATHY MAPPING CANVAS:
This canvas gives us the idea of the activities performed by turbine, users &
stockholders of turbine & the story which denotes the benefits or advantages and the
disadvantages of the turbine. Activities & Users are similar to other canvas only the new thing is the stockholders and the story.
Story based on true events Happy & Sad which describe how the device is beneficial
and how it may be change to get the better result with the modified and effective
device. Universities and research institutions are the main stockholders for bladeless turbine.
PRODUCT DEVELOPMENT CANVAS:
It is the section where purpose of the device is describe which includes the basic aim & objective of the device such as,
-Most effective micro power generation
-Effectively drug injection into blood
-Internal combustion engine
It includes the user which helps them to fulfill their needs by the help of this
device which includes various power generation industries, in small households and in agricultural fields basically everywhere where power is needed in medium amounts.
It defines the device perfectly as it is being used in various cases and knowing the
merits and demerits of it. From experience of this device some factors are
important to describe it such as its productive and effective nature, scalable quality, work satisfaction and 100% uptime.
It includes the function which is performed by the device to achieve the objective
of the device such as rotation of the discs by the centrifugal action of the fluid and thereby producing the power. The discs rotate due to the properties of the fluid such as as viscosity and adhesion.
For any device, users are generally in search of the features of the device which
gives the basic information of the device. Features of bladeless turbine are as follows:
-Ease to manufacture
-No restriction on fluid purity and type
They are the heart of the device as proper functioning of the components is
advisable for effective function of the device. Components used are compressor, shaft, nozzle, bearing, coupling, spacers, casing, discs and generator.
This section includes the feedback which is given by the customer that is the
problem faced by the customer after using the bladeless turbine. Thus it gives us problems
that are faced by the customer. The problems faced are not much in account as this turbine has not much widespread in use still there are problems of low efficiency at high power requirements.
REJECT, REDESIGN, AND RETAIN:
The main effective parameters to increase the efficiency is the nozzle angle directing the pressurized fluid, then there is the space between the discs which should be maintained constant.
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