Abstract: The present invention provides systems, devices, and methods for transferring kinetic energy from a working fluid to mechanical energy. The claimed device comprises a housing, at least one fluid inlet, a rotor assembly with a plurality of closely related blades that are positioned to create at least one spiral pathway which is continuous for the length of the rotor assembly, a shaft connected to the rotor assembly, and at least one fluid outlet. The energy is transferred when a working fluid enters the fluid inlet, flows trough the spiral pathway in the rotor assembly's direction of rotation, and exits through the fluid outlet.