Patent ID: 9267511
Filing Date: 2016-02-23
CPC Classification: F04D,F05D

Claim Text:
1. A turbofan comprising a disc-shaped main plate having a boss projecting in a predetermined region containing a center of rotation; a ring-shaped shroud facing the main plate; and a plurality of blades each having two ends thereof joined to the main plate and the shroud, respectively, wherein a blade rear edge of each of the plurality of blades resides on a virtual cylinder defined by an outer circumference of the main plate and an outer circumference of the shroud, a blade front edge of each of the plurality of blades resides at a position nearer to the center of rotation than the blade rear edge, and a virtual line connecting the blade rear edge and the blade front edge is angled with respect to a radial line extending from the center of rotation, wherein a blade outer-circumferential surface, that is a surface of each of the plurality of blades farther from the center of rotation, has a plurality of rear-edge horizontal grooves having predetermined lengths reaching the blade rear edge, wherein the rear-edge horizontal grooves extend perpendicularly to the center of rotation and wrap around an end of the blade rear edge to a blade inner-circumferential surface that is a surface of each of the plurality of blades nearer to the center of rotation, and wherein the blade outer-circumferential surface of each of the plurality of blades has inter-groove surface portions extending between adjacent ones of the rear-edge horizontal grooves, and one of the inter groove surface portions is larger than other inter-groove surface portions.