Patent ID: 8801386

Claim:
A blade for driving an axial-flow underwater power generation machine, the blade in use being adapted for rotation about a rotation axis in response to water flow from a direction parallel with the rotation axis, the underwater power generation machine being adapted to be mounted in a body of the water and having a power generation unit adapted to be driven by the blade so as to generate power, the blade comprising: a blade root mounted to a hub; a free blade tip; a leading edge extending from the blade root to the blade tip; a trailing edge extending from the blade root to the free blade tip; a blade profile for generating lift when the blade rotates with the hub about the rotation axis the blade profile defining two blade surfaces extending between the leading edge and the trailing edge; a blade root chord defined as a straight line between the leading edge and the trailing edge at the blade root; and a blade tip chord defined as a straight line between the leading edge and the trailing edge at the free blade tip; wherein the blade tip chord is angularly displaced from the blade root chord by a twist angle of between 70 degrees and 90 degrees.