Figure 1A-1C A typical embodiment of a sheet metal swirler 1 is shown. The swirler includes an outer circumferential ring 2, a central part 3, and three blades 4 arranged equidistantly in the radial direction. These blades 4 bridge the central part 3 and the outer circumferential ring 2 . The size and shape of these blades 4 are the same. The blade 4 has a flow inlet portion 5 located at the flow inlet side edge 6 and a flow outlet portion 7 located at the flow outlet side edge 8.
 Such as Figure 1C As shown, an inlet angle α of approximately 90 degrees is defined between the flow inlet portion 5 and the plane passing through the ring 2 and the central portion 3, which plane constitutes the plane of the original sheet metal blank. The flow outlet portion 7 defines an outlet angle β of approximately 40 degrees. The side edge 6 of the flow inlet is truncated to be substantially perpendicular to the flow direction (e.g. Figure 1C Shown by arrow A in).
 In the illustrated embodiment, the flow inlet portion 5 of the blade 4 is gradually curved from an inlet angle of 90 degrees to an outlet angle of 40 degrees. The position where the outlet angle is 40 degrees is Figure 1A The position shown in the imaginary line B. In alternative embodiments, line B may be located at a higher or lower position. The curvature radius of the curved portion of the blade 4 is, for example, constant or gradually increases or decreases from the inlet edge toward the line B. The flow outlet portion 7 is flat, maintaining an angle of approximately 40 degrees. In an alternative embodiment, the flow inlet portion 5 may also have a flat portion located near the edge of the flow inlet; and/or the flow outlet portion 7 may also be bent to gradually reach a suitable position at the flow outlet edge 8, and Achieve the required exit angle.
 Such as Figure 1B As shown, the blade 4 has an outer peripheral edge 9 which together define a circular profile shown in plan view. In this way, the outer peripheral edge 9 joins the channel wall surface (not shown) so that there is no large gap between the two.
 Figure 1D The state of the sheet metal blank 10 for the cyclone 1 after the cutting line is formed is shown. The radial cutting line 11 is cut to at least partially define the flow inlet edge 6 and the flow outlet edge 8 of the blade 4. The radial cutting line 11 is bridged by a cutting line 12 delimiting the outer peripheral edge 9 of the blade 4. The shape of the cutting line 12 is set such that after the blade 4 is bent into the final shape, the outer peripheral edge 9 follows the circular contour in a plan view. Therefore, compared with the end point 14 of the cutting line 12 at the entrance edge 6, the radial distance between the end point 13 of the cutting line 12 on the side of the exit edge 8 and the central portion 3 is larger.
 In order to cut off the flow inlet edge 6, the triangular part 15 is cut off. The blade 4 is then bent into the final shape. Alternatively, the outer circumferential ring 2 may be removed, or the outer circumferential ring may be retained to support fasteners or the like.
 Such as Figure 1B As shown, the gap 16 is open between the blades 4. Therefore, a part of the gas can flow through the blade 4 without being swirled. In order to improve the swirling efficiency, two identical cyclones 1 can be stacked together as sub-cyclones to form Figure 2A-2D The single cyclone 20 shown in. The sub-cyclones 1 are stacked together so that the blades 4 arranged at equal intervals are entangling, and the rings 2 are connected to each other. The ring 2 is provided with holes 17. When the blades 4 are arranged at equal intervals, the holes 17 of the lower sub-cyclone 1 are aligned with the holes 17 of the upper sub-cyclone 1.
 Figure 2C with 2D A plan view of the swirler 20 is shown from a downstream angle and an upstream angle, respectively. Figure 2C Shows a straight flow outlet edge 6, Figure 2D The truncated flow inlet edge 6 is shown. The blade 4 covers the entire circular flow area. Any gas passing through the swirler 20 will be hit by the blade 4, causing the gas to swirl. Depending on the direction of the blade 4, the airflow can swirl in a clockwise or counterclockwise direction.
 The ring 2 can be used, for example, to fasten the cyclone 20 at the end of a pipe or between two pipes, so that the blade 4 is located in the channel defined by the pipe, and the ring 2 does not cross the flow path of the channel.
 If the cyclone is located in the channel with a certain distance from the end of the channel, then a cyclone without any peripheral ring 2 can be used. image 3 Another embodiment is shown, namely such an acyclic cyclone 30, which is similar to Figure 2A-2C The difference between the cyclone 20 in the dies is that the ring 2 is removed. The cyclone 30 is formed by stacking two ringless sub cyclones.
 The central part 3 can be smaller relative to the blade 4, or the central part 3 can be made larger. A larger central section 3 generally produces a greater pressure drop. In the illustrated embodiment, the central part 3 is positioned between the flow outlet part 7 and the flow inlet part 5 of the blade 4. Alternatively, the central part may be used to connect two or more sub-cyclones to each other, for example by bolting.