The impeller has three forms: a closed impeller, a semi-open impeller and an open impeller.
The closed impeller consists of front and rear cover plates and intermediate blades. The semi-open impeller has no front cover and the open impeller has only a part of the rear cover. The blade has two shapes:
1. Single-curvature blades, also called cylindrical blades, whose surface is unidirectionally curved. Because the cylindrical surface is a unidirectionally curved surface, it is called a cylindrical blade.
2. Double-curvature blades, the surface of which is a bi-directionally curved surface, that is, a spatial curved surface, also known as a twisted blade.
In order to completely and clearly represent the geometry of the impeller, two auxiliary planes (planar and axial) are now introduced. The plane is the plane of the vertical axis, and the plane of the axis is the plane of the axis of the axis, and the axis plane and the plane can be any number.
