1. Introduction
The first bladeless turbine, also known as a friction turbine, was designed
and manufactured by a Serbian engineer and inventor Nicola Tesla in 1913
(Tesla, 1913). This unusual device makes use of viscous effects which occur in
the boundary layer flow. Opposite to classical bladed turbines, where viscous
effects in flow are undesirable as a source of efficiency loss, these effects enable
rotational movement of the rotor. The rotor consists of up to a few dozens of
thin disks locked on a shaft perpendicular to its axis of revolution. In theory,
the disks should be as thin as possible. The distances, or gaps, between the
disks should also be very small. According to Rice (1991), the highest value of
efficiency appears when they are approximately equal to the double boundary layer thickness. Therefore, the gaps between the disks should depend on the
occurring flow conditions and physical properties of the working fluid. On the
other hand, the thickness of the disks and the distances between them are
also limited by the material strength and the technology of manufacture and
assembly. An example of the multidisk rotor construction of the Tesla turbine
found in the patent documentation (Hicks, 2005) is shown in Fig. 1.
The supply of the Tesla turbine is accomplished by one or several noz-
zles discretely located along the circumference. The nozzles are tilted under a
certain angle to the disk tangent. The working fluid flows between the disks
spirally from the outer to inner radius and transfers energy to the rotating
disks. The medium flows out in the axial direction through a number of holes
in the disks situated near the turbine shaft. The efficiency of the Tesla turbine
depends on many parameters, namely on: pressure, temperature and velocity
conditions between the disks, number, diameter, thickness and distance be-
tween the disks as well as on the state of the disk surface, rotational speed of
the rotor, number and arrangement of the supply nozzles, etc.
In the subject-matter literature, examples of experimental research refer-
ring to the following models of Tesla micro-turbines can be found