Patent attributes
A guiding grid is disclosed and includes plural circumferential elements and plural radial elements. The circumferential elements are disposed concentrically relative to a central axis, spaced apart from each other in a radial direction, and form different heights relative to a bottom surface. One of the circumferential elements forms a top height relative to the bottom surface, so that the circumferential elements are divided into an outer-ring region and a central region in the radial direction. The circumferential elements located in the central region are increased in height relative to the bottom surface along the radial direction. The circumferential element located in the outer ring region are reduced in height relative to the bottom surface along the radial direction. The radial elements are connected between each of two adjacent circumferential elements. At least one of the radial elements is misaligned and discontinuous in the radial direction.
