What type of turbine did Nikola Tesla invent that has no blades?

Nikola Tesla invented the Tesla turbine, a turbine that operates without conventional blades.

Instead of using rows of shaped blades, the Tesla turbine uses a stack of smooth, closely spaced discs mounted on a shaft. Fluid enters tangentially near the discs’ outer edges and transfers energy through viscosity and adhesion as it spirals inward. The resulting boundary-layer effect turns the discs and shaft.

Tesla developed the concept in the early twentieth century and patented his turbine design in 1913. He demonstrated a 200-horsepower version in 1906, and later tests examined machines ranging from roughly 100 to 5,000 horsepower. He imagined applications including steam power and geothermal energy.

The turbine is also called a bladeless turbine, boundary-layer turbine, or Prandtl-layer turbine. Kaplan, Pelton, and Francis turbines are different designs: all rely on fluid interacting with blades or buckets. The Tesla turbine’s smooth-disc arrangement is its defining feature, although the word “bladeless” does not mean it lacks rotating components.