A volute-free centrifugal fan impeller

Abstract

The impeller of the volute-free centrifugal fan of the application comprises an upper disc, a lower disc and a plurality of spatial curved blades arranged between the upper disc and the lower disc. The three-dimensional modeling of the blades satisfies a set of cooperative geometric rules: the inlet angles of five characteristic sections along the blade height satisfy alpha2 > alpha3 > alpha1 > alpha4 > alpha5, and the outlet angles satisfy beta5 > beta4 > beta3 > beta2 > beta1; in the polar projection, the profile of the upper disc end section is the outermost, the profile of the lower disc end section is the innermost, and the profile of the middle section is inwardly tapered towards the tail edge; and the most protruding point of the leading edge and / or the trailing edge of the blade is located near the 25% blade height section. Through systematic optimization of the spatial geometry of the blades, reasonable distribution of the load and efficient expansion of the flow passage are achieved, thereby significantly improving the fan efficiency, widening the working range and reducing the noise.

Description

Technical Field

[0001] This invention relates to the field of fluid machinery technology, and specifically to a centrifugal fan impeller without a volute. Background Technology

[0002] Casingless centrifugal fans are widely used in air conditioning, ventilation, and other fields due to their compact structure and flexible outlet airflow direction. Their performance hinges on the impeller, especially the three-dimensional design of the blades.

[0003] Traditional volute-less centrifugal impeller blade designs often employ simple two-dimensional molding or linearly varying twist angles along the blade height. Such designs frequently suffer from the following drawbacks: 1) Poor airflow matching along the blade height, leading to uneven load distribution between the blade root and tip; 2) Flow separation easily occurs at the blade's suction surface, especially under off-design conditions, resulting in significant efficiency reduction and increased noise; 3) The design methodology lacks specificity, making it difficult to fully utilize the aerodynamic potential of the volute-less structure.

[0004] While some patents in the existing technology focus on blade shape, they are mostly concentrated on specific curve equations or local optimizations, lacking an understanding of the overall spatial configuration of the blade. The aforementioned improved design methods lack systematicity and cannot unleash the unique advantages of the volute-less configuration, resulting in a narrow range of applications and limited improvement in aerodynamic performance.

[0005] Therefore, there is an urgent need for a volute-less centrifugal impeller based on a novel three-dimensional spatial configuration concept, in order to systematically optimize the flow field, broaden the high-efficiency working area, and improve the overall aerodynamic performance. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies and provide a volute-less centrifugal fan impeller. It achieves systematic optimization of the three-dimensional flow field inside the impeller through a set of innovative and interrelated blade spatial geometric parameters, thereby improving efficiency, reducing noise, and expanding the stable operating range.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A centrifugal fan impeller without a volute includes an upper plate, a lower plate, and multiple blades disposed between the two. The blades are sheet metal stamped blades of uniform thickness with a spatial curved surface shape. Along the blade height direction, five evenly distributed cross-sections are provided. These cross-sections include a first cross-section S1 near the upper plate and a fifth cross-section S5 near the lower plate. Specifically, the five cross-sections include a first cross-section S1 representing 100% of the blade height, a second cross-section S2 representing 75% of the blade height, a third cross-section S3 representing 50% of the blade height, a fourth cross-section S4 representing 25% of the blade height, and a fifth cross-section S5 representing 0% of the blade height. The impeller is characterized in that the geometric parameters of the five evenly distributed cross-sections satisfy at least three of the following spatial distribution rules:

[0009] (a) The entrance angle α1-α5 and the exit angle β1-β5 of each section satisfy: α2 > α3 > α1 > α4 > α5 and β5 > β4 > β3 > β2 > β1;

[0010] (b) The airflow angle of the arc in each section increases monotonically from the leading edge to the middle of the middle arc, and the growth rate slows down or becomes negative from the middle to the trailing edge;

[0011] (c) Project the profiles of each blade onto a polar coordinate system with the center of the disk as the origin. The profile of the first section S1 is located on the outermost side, the profile of the fifth section S5 is located on the innermost side, and the trailing edge 32 of the second section S2 and the third section S3 is closer to the trailing edge of the first section S1 in the circumferential position than its leading edge.

[0012] (d) The most prominent point of the point on the leading edge of the blade in the direction of rotation is located on the fourth section S4, and / or the most prominent point of the point on the trailing edge of the blade in the direction of rotation is located on the fourth section S4.

[0013] Furthermore, in the first section S1, the fourth section S4, and the fifth section S5, the airflow angle of the arc increases monotonically from the leading edge to the middle of the arc, and the rate of increase slows down from the middle to the trailing edge. In the second section S2 and the third section S3, the airflow angle of the arc increases monotonically from the leading edge to the middle of the arc, and the airflow angle decreases from the middle to the trailing edge.

[0014] Furthermore, both the leading edge and trailing edge of the blade are spatial curves that bulge in the direction of rotation.

[0015] Furthermore, the cross-sectional profile of the upper plate consists of a transition curve segment, a first horizontal straight line segment, and a first flange from the inlet to the outlet, while the cross-sectional profile of the lower plate consists of a second horizontal straight line segment and a second flange.

[0016] Furthermore, the transition curve segment is part of a hyperbola.

[0017] Furthermore, the first and second flanges are straight segments, circular arc segments, or curved segments with a swept-over structure.

[0018] Furthermore, when the first flange and the second flange are straight line segments, there is a first included angle between the first horizontal straight line segment and the first flange, and the size of the first included angle is 75° to 90°; there is a second included angle between the second horizontal straight line segment and the second flange, and the size of the second included angle is 60° to 85°.

[0019] Furthermore, the position where the second horizontal straight segment connects to the second flange and the position where the first horizontal straight segment connects to the first flange are not in the same axial position; and in the radial position, the position where the second horizontal straight segment connects to the second flange is further away from the impeller center axis.

[0020] Furthermore, the blades are also equipped with reinforcing ribs.

[0021] Furthermore, the number of leaves is 6 to 12.

[0022] Furthermore, the transition curve segment is a curve with continuously changing curvature.

[0023] A method for manufacturing a centrifugal fan impeller without a volute is characterized by comprising at least the following steps: forming a spatial curved blade of uniform thickness by a stamping process; and fixing the blade to an upper plate and a lower plate by welding or riveting.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. High aerodynamic efficiency: Through the coordinated non-monotonic distribution of inlet and outlet angles and a unique spatial projection layout, the load is optimized along the blade height and the flow channel is expanded efficiently, which significantly reduces secondary flow and separation losses. The static pressure efficiency of the impeller is increased from 60.8% to 63.9%, an improvement of 3.1%.

[0026] 2. Wide operating range: The unique design makes the blades insensitive to changes in the angle of attack of the incoming flow, maintaining good airflow adhesion even when deviating from the design conditions, thus widening the stable and efficient operating range of the fan. Furthermore, optimized transition curve sections, the design of the first and second flanges further expand the operating range and reduce noise.

[0027] 3. Low noise: The optimized flow structure effectively reduces flow separation and eddy intensity, thereby reducing aerodynamic noise sources. The outlet noise (sound pressure level) of the fan under optimal efficiency conditions is reduced from 80 dBA to 75 dBA, a reduction of 5 dB.

[0028] 4. Excellent structural manufacturability: The blades are formed by stamping from sheet metal of uniform thickness, achieving complex spatial curved surfaces while maintaining good manufacturability and economy. In addition, the well-defined geometric shape of the impeller of the volute-less centrifugal fan facilitates digital design and manufacturing. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a three-dimensional structural diagram of the impeller of the present invention.

[0031] Figure 2 for Figure 1 The right view (axial view).

[0032] Figure 3 For along Figure 2 The cross-sectional view along line AA shows the cross-sectional structure of the upper and lower plates.

[0033] Figure 4 This is a schematic diagram of the blade's spatial profile and the locations of its five characteristic sections.

[0034] Figures 5a-5e This is a schematic diagram of the airfoil with five characteristic sections.

[0035] Figure 6 The polar coordinate projection of the five characteristic cross-sectional profiles onto the lower plate plane.

[0036] Figure 7 The measured airflow-pressure performance curves are for the examples and comparative examples.

[0037] Figure 8 The measured airflow-static pressure efficiency performance curves are for the examples and comparative examples.

[0038] The reference numerals in the above figures are as follows: upper plate 1, transition curve segment 11, first horizontal straight line segment 12, first flange 13, lower plate 2, second horizontal straight line segment 21, second flange 22, blade 3, leading edge 31, trailing edge 32, middle arc line 33, first section S1, second section S2, third section S3, fourth section S4, fifth section S5, entrance angle α1-α5 of each section, and exit angle β1-β5 of each section. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings.

[0041] like Figure 1-8As shown, a centrifugal fan impeller without a volute includes an upper plate 1, a lower plate 2, and multiple blades 3 disposed between the two. The blades 3 are sheet metal stamped blades of uniform thickness with a spatial curved surface shape. Along the blade height direction, five evenly distributed cross-sections are provided. These cross-sections include a first cross-section S1 near the upper plate 1 and a fifth cross-section S5 near the lower plate 2. Specifically, the five cross-sections include a first cross-section S1 representing 100% of the blade height, a second cross-section S2 representing 75% of the blade height, a third cross-section S3 representing 50% of the blade height, a fourth cross-section S4 representing 25% of the blade height, and a fifth cross-section S5 representing 0% of the blade height. The impeller is characterized in that the geometric parameters of the five evenly distributed cross-sections satisfy at least three of the following spatial distribution rules:

[0042] (a) The entrance angle α1-α5 and the exit angle β1-β5 of each section satisfy: α2 > α3 > α1 > α4 > α5 and β5 > β4 > β3 > β2 > β1;

[0043] (b) The airflow angle of the arc 33 in each section increases monotonically from the leading edge 31 to the middle of the middle arc 33, and its growth rate slows down or becomes negative from the middle to the trailing edge 32.

[0044] (c) Project the profiles of each blade 3 onto a polar coordinate system with the center of the disk as the origin. The profile of the first section S1 is located on the outermost side, and the profile of the fifth section S5 is located on the innermost side. The trailing edge 32 of the second section S2 and the third section S3 is closer to the trailing edge 32 of the first section S1 in the circumferential position than the leading edge 31 of the second section S2.

[0045] (d) The most prominent point of the point on the leading edge 31 of the blade 3 in the direction of rotation is located on the fourth section S4, and / or the most prominent point of the point on the trailing edge 32 of the blade 3 in the direction of rotation is located on the fourth section S4.

[0046] Furthermore, in the first section S1, the fourth section S4, and the fifth section S5, the airflow angle of the arc 33 increases monotonically from the leading edge 31 to the middle of the arc 33, and the growth rate slows down from the middle to the trailing edge 32. In the second section S2 and the third section S3, the airflow angle of the arc 33 increases monotonically from the leading edge 31 to the middle of the arc 33, and the airflow angle shows a decreasing trend from the middle to the trailing edge 32.

[0047] Furthermore, both the leading edge line 3 and the trailing edge line 32 of the blade 3 are spatial curves that bulge in the direction of rotation.

[0048] Furthermore, the cross-sectional profile of the upper plate 1 is composed of a transition curve segment 11, a first horizontal straight line segment 12 and a first flange 13 from the inlet to the outlet, while the cross-sectional profile of the lower plate 2 is composed of a second horizontal straight line segment 21 and a second flange 22.

[0049] Furthermore, transition curve segment 11 is part of a hyperbola.

[0050] Furthermore, the first flange 13 and the second flange 22 are straight segments, circular arc segments, or curved segments with a swept-back structure.

[0051] Furthermore, when the first flange 13 and the second flange 22 are straight line segments, there is a first included angle between the first horizontal straight line segment 12 and the first flange 13, and the size of the first included angle is 75° to 90°; there is a second included angle between the second horizontal straight line segment 21 and the second flange 22, and the size of the second included angle is 60° to 85°.

[0052] Furthermore, the position where the second horizontal straight segment 21 connects to the second flange 22 and the position where the first horizontal straight segment 12 connects to the first flange 13 are not in the same axial position (i.e., the line connecting the two positions is not parallel to the impeller central axis); and in the radial position, the position where the second horizontal straight segment 21 connects to the second flange 22 is further away from the impeller central axis.

[0053] Furthermore, blade 3 is also equipped with reinforcing ribs.

[0054] Furthermore, the number of leaves 3 is 6 to 12.

[0055] Furthermore, transition curve segment 11 is a curve with continuously changing curvature.

[0056] A method for manufacturing a centrifugal fan impeller without a volute is characterized by comprising at least the following steps: forming a spatial curved blade 3 of uniform thickness by a stamping process; and fixing the blade 3 to the upper plate 1 and the lower plate 2 by welding or riveting.

[0057] Example

[0058] See Figures 1 to 4 This embodiment provides a centrifugal fan impeller without a volute. The impeller mainly consists of an upper disk 1, a lower disk 2, and eight blades 3 evenly distributed circumferentially. The blades 3 are made of steel plates of uniform thickness, stamped into complex spatial curved surfaces by a die, with a thickness of 1.5 mm.

[0059] like Figure 3 As shown, the cross-sectional profile of the upper plate 1, from the inlet to the outlet, consists of a smooth transition curve segment 11, a first horizontal straight line segment 12, and an upward-folding first flange 13. The lower plate 2 is a flat plate, and its cross-section is composed of a second horizontal straight line segment 21 and a downward-folding second flange 22. The upper plate 1 and the lower plate 2 together constitute the flow channel boundary of the impeller. Figure 3 It is also shown that the position where the second horizontal straight segment 21 connects to the second flange 22 and the position where the first horizontal straight segment 12 connects to the first flange 13 are not in the same axial position; and in the radial position, the position where the second horizontal straight segment 21 connects to the second flange 22 is further away from the impeller center axis.

[0060] The core feature of the blade 3 of this invention is embodied in the geometric relationship of its five characteristic sections S1 to S5. For example... Figure 4 and Figures 5a-5e As shown, these five sections are evenly distributed along the blade height direction. The blade profile of each section is defined by the mid-curve 33 and the uniform thickness line surrounding it. The inlet angle α is defined as the angle between the tangent of the mid-curve 33 at the leading edge and the tangent of the circle at that point, and the outlet angle β is defined as the angle between the tangent of the mid-curve 33 at the trailing edge and the tangent of the circle at that point.

[0061] In this embodiment, the angle measurements of the five cross sections are shown in the table below, and they strictly follow a certain pattern:

[0062] S1 0% 13.82 20.37 21.38 S2 25% 19 23.97 21.55 S3 50% 16.87 26.35 23.13 S4 75% 13.01 27.64 27.96 S5 100% 7.25 27.29 35.34

[0063] See Figure 6 Projecting the outlines of the five sections onto a polar coordinate plane with the center of the disk as the origin, it is clear that the outline of section S1 is located on the outermost side, while the outline of section S5 is located on the innermost side. The trailing edges of sections S2 and S3 are significantly closer to the trailing edge of section S1 in the circumferential direction than their respective leading edges, forming a unique "protruding trailing edge" layout. (See also...) Figure 6 In the schematic diagram showing the spatial orientation of the leading edge 31 and trailing edge 32 of the blade, it can be clearly observed that the most convex vertex of the spatial curve formed by connecting the leading edge points of each section is located at section S4. Similarly, the most convex vertex of the spatial curve formed by connecting the trailing edge points of each section is also located at section S4. This proves the "peak" position of the three-dimensional surface of the blade. Furthermore, as... Figure 6 As shown, the curvature of the mid-arc 33 in each cross-section ensures that the airflow angle (the angle between the tangent of the mid-arc and the circumferential direction) increases continuously and smoothly from the leading edge to the middle of the arc, and the rate of increase gradually slows down after the middle. In particular, the airflow angle of the mid-arc in cross-sections 2 and 3 shows a decreasing trend from the middle to the trailing edge. This angle variation pattern is conducive to smooth airflow turning and avoids separation.

[0064] Blade 3 is fixed between upper plate 1 and lower plate 2 by welding. To improve blade stiffness, two to five reinforcing ribs (not shown in the figure) can be stamped in the middle of the blade pressure surface.

[0065] Figure 7 and Figure 8The data on airflow-pressure and airflow-static pressure efficiency curves of the fan with the assembled impeller and the existing two-dimensional molded impeller are displayed on a standard fan performance test bench. As can be seen from the figures, this invention achieves optimized load distribution and efficient flow channel expansion along the blade height direction through a coordinated non-monotonic distribution of the inlet and outlet angles and a unique spatial projection layout. This significantly reduces secondary flow and separation losses, increasing the impeller's static pressure efficiency from 60.8% to 63.9%, an improvement of 3.1%.

[0066] The unique design of this invention makes the blades insensitive to changes in the angle of attack of the incoming flow, and can still maintain good airflow adhesion when deviating from the design conditions, thereby expanding the stable and efficient operating range of the fan.

[0067] The optimized flow structure of this invention effectively reduces flow separation and eddy intensity, thereby reducing aerodynamic noise sources. The outlet noise (sound pressure level) of the fan under optimal efficiency conditions is reduced from 80 dBA to 75 dBA, a reduction of 5 dB.

[0068] The above embodiments are illustrative of the present invention and not intended to limit the invention. It is understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A centrifugal fan impeller without a volute, comprising an upper plate (1), a lower plate (2), and a plurality of blades (3) disposed between the two; the blades (3) are sheet metal stamped blades of uniform thickness with a spatial curved surface shape, and five uniformly distributed cross sections are provided along the blade height direction, the aforementioned cross sections including a first cross section S1 near the upper plate (1) to a fifth cross section S5 near the lower plate (2), the five cross sections specifically including a first cross section S1 of 100% blade height, a second cross section S2 of 75% blade height, a third cross section S3 of 50% blade height, a fourth cross section S4 of 25% blade height, and a fifth cross section S5 of 0% blade height; characterized in that: The geometric parameters of the five uniformly distributed cross-sections must satisfy at least three of the following spatial distribution rules: (a) The entrance angle α1-α5 and the exit angle β1-β5 of each section satisfy: α2 > α3 > α1 > α4 > α5 and β5 > β4 > β3 > β2 > β1; (b) The airflow angle of the arc (33) in each section increases monotonically from the leading edge (31) to the middle of the middle arc (33), and its growth rate slows down or becomes negative from the middle to the trailing edge (32). (c) Project the outline of each blade (3) onto the polar coordinate system with the center of the disk as the origin. The outline of the first section S1 is located on the outermost side, and the outline of the fifth section S5 is located on the innermost side. The trailing edge (32) of the second section S2 and the third section S3 is closer to the trailing edge (32) of the first section S1 in the circumferential position than its leading edge (31). (d) The most prominent point of the point on the leading edge (31) of the blade (3) in the direction of rotation is located on the fourth section S4, and / or the most prominent point of the point on the trailing edge (32) of the blade (3) in the direction of rotation is located on the fourth section S4.

2. The centrifugal fan impeller without a volute as described in claim 1, characterized in that, The airflow angle of the arc (33) in the first section S1, the fourth section S4, and the fifth section S5 increases monotonically from the leading edge (31) to the middle of the arc (33), and the growth rate slows down from the middle to the trailing edge (32). The airflow angle of the arc (33) in the second section S2 and the third section S3 increases monotonically from the leading edge (31) to the middle of the arc (33), and the airflow angle decreases from the middle to the trailing edge (32).

3. The centrifugal fan impeller without a volute as described in claim 1, characterized in that, The leading edge (3) line and trailing edge (32) line of the blade (3) are both spatial curves that bulge in the direction of rotation.

4. The centrifugal fan impeller without a volute as described in claim 1, characterized in that, The cross-sectional profile of the upper plate (1) consists of a transition curve segment (11), a first horizontal straight line segment (12) and a first flange (13) from the inlet to the outlet. The cross-sectional profile of the lower plate (2) consists of a second horizontal straight line segment (21) and a second flange (22).

5. The centrifugal fan impeller without a volute as described in claim 4, characterized in that, The transition curve segment (11) is part of the hyperbola.

6. The centrifugal fan impeller without a volute as described in claim 5, characterized in that, The first flange (13) and the second flange (22) are straight segments, circular arc segments, or curved segments with a sweeping structure.

7. The centrifugal fan impeller without a volute as described in claim 6, characterized in that, When the first flange (13) and the second flange (22) are straight segments, there is a first included angle between the first horizontal straight segment (12) and the first flange (13), and the size of the first included angle is 75° to 90°; there is a second included angle between the second horizontal straight segment (21) and the second flange (22), and the size of the second included angle is 60° to 85°.

8. The centrifugal fan impeller without a volute as described in claim 6, characterized in that, The position where the second horizontal straight segment (21) connects to the second flange (22) and the position where the first horizontal straight segment (12) connects to the first flange (13) are not in the same axial position; and in the radial position, the position where the second horizontal straight segment (21) connects to the second flange (22) is further away from the impeller center axis.

9. The centrifugal fan impeller without a volute as described in claim 1, characterized in that, The blade (3) is also equipped with reinforcing ribs.

10. The centrifugal fan impeller without a volute as described in claim 1, characterized in that, The number of leaves (3) is 6 to 12.

11. The centrifugal fan impeller without a volute as described in claim 4, characterized in that, The transition curve segment (11) is a curve with continuously changing curvature.

12. A method for manufacturing a volute-less centrifugal fan impeller as described in any one of claims 1 to 11, characterized in that, The process includes at least the following steps: forming a spatial curved blade (3) of equal thickness by stamping; and fixing the blade (3) to the upper plate (1) and the lower plate (2) by welding or riveting.

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