Tesla Turbine Theory
As mentioned early, the Tesla Turbine uses adhesion and the boundary layer principle to derive energy from a fluid stream. Supersonic gases are directed against the chamber by several nozzles. The nozzles inject the gases at the edge of the discs, in the direction of the desired rotation. Because of boundary layer effects and the viscosity effects, the gases drag against the plates and transfer their kinetic energy to the plates, which rotate. As the gases slow, the move into the central ventilation holes and are expelled as exhaust.
Interestingly, the turbine can be altered to act as a pump instead of a turbine. In the Tesla pump design, a motor spins the discs, which then suck in fluid through the exhaust holes. This pump is useful for applications with excessively viscous, abrasive, solid-containing, or shear-averse fluids due to its increased sturdiness.
Calculations show that the turbine efficiency for Tesla turbines is above 60 percent, and up to 95 percent. Tesla himself believed that steam-powered Tesla turbines could achieve turbine efficiencies up to 95 percent. These calculations use the shear stress induced by the boundary layer effects of the flowing fluid. This requires calculation of some characteristics of the motive fluid, like the Reynolds number. To prevent drag on the ends of the discs, which reduces efficiency, the spinning plates must be as thin as possible. This requirement contributed to material problems that prevented the Tesla turbine from gaining acceptance.