03-10-2016, 11:12 AM
1457438656-IJSETRVOL4ISSUE4710714.pdf (Size: 370.63 KB / Downloads: 76)
ABSTRACT
Turbines that would provide a quiet, safe, simple and efficient alternative to our supposedly advanced bladed turbine aircraft engines are the need of the hour.
One such turbine called the bladeless turbine that poses to be the ideal replacement for the conventional turbines was successfully designed. The design of such
an unconventional turbine was conceived considering the catastrophic effects that conventional turbines may have on the machines they are incorporated. The
turbine is designed in such a way that the blades of a conventional turbine are replaced by a series of flat, parallel, co-rotating discs spaced along a shaft. The
discs are used to eliminate the expansion losses that are incurred in conventional turbines and also to reduce noise considerably at high RPMs. Furthermore, the
design of the turbine ensures that the turbine rotates at high RPMs with total safety unlike a conventional turbine which explodes under failure due to fatigue. The
engines making use of these bladeless turbines can run efficiently on any fuel, from sawdust to hydrogen. Bladeless turbines are also the greenest turbines with
almost nil harmful effects on the environment. Another major advantage of this design is that this turbine has only one moving part, thereby reducing the
vibrations to a minimum. Overall this design aims at bringing out a new age turbine with improved performance that can provide an engine that is economic, ecofriendly
and reliable as the expensive, complicated and wear prone transmission is eliminated.
. Introduction
In 1913 Nikola Tesla patented a bladeless centripetal flow turbine called the
Tesla turbine. It is referred to as a bladeless turbine. The turbine is also
known as the boundary layer turbine because it uses the boundary layer
effect for its operation unlike a conventional turbine where a fluid
impinging upon the blades drives it. Bioengineering researchers have
referred to it as a multiple disccentrifugal pump[1].The performance of
Tesla turbine is found to be influenced by a number of parameters including width of discs, number of discs, gap between discs, jet angle at inlet, inlet
pressure, load applied, Mach number and Reynolds’s number[2].
Tesla in his patent argued that for high efficiency devices changes in
velocity and direction should be gradual. Tesla sought to design a device
where the fluid was allowed to follow its natural path with minimal
disturbance, both to increase efficiency and to reduce cost and complexity
in the device. He pointed out several important factors affecting performance, including that increasing size and speed increases the
efficiency, as does decreasing the disc spacing. He also mentions that
centrifugal pressure gradients, increasing with the square of velocity,
prevent the device from running away to high speeds and thus preventing
the device from damage [3].
Conventional turbines suffer a major drawback in practical applications
because of their low efficiencies. Their efficiency is lowered by the use of
moving blades to generate shaft power. Thus failure of a single blade results
in inadequate expansion which directly affects the overall efficiency of the
turbine. On the contrary Tesla turbine consists of a set of smooth disks, with
nozzles applying a moving gas to the edge of the disc. The gases drag on
the disc by means of viscosity and the adhesion of the surface layer of the
gas. As the gas slows and adds energy to the discs, it spirals into the center
exhaust and causes rotation of the discs[4].Thus minimizing the expansion
losses and increasing the efficiency of the prime mover.
2. Formula for determining torque
Tesla describes a dynamic relation between the disc and the fluid [3].
However the mass and viscosity of the fluid are essential in developing an
equation that will work across fluid. The equations are:
Momentum = mass * velocity
Kinetic energy = (mass*velocity2
) / 2
Also engineers have developed a dynamic relation between torque and fluid
viscosity as follows,
Torque = (3uvr
2
) / 2h
Where
v = velocity of the fluid, in meters/second
u = viscosity of the fluid, in Pascal-second
r = radius of the disc, in meters
h = half of the distance between the discs, in meters