Backward plate type three-dimensional flow blade volute-free centrifugal fan

Abstract

A backward plate type three-dimensional flow blade volute-free centrifugal fan comprises a rear wheel disc, a blade and a front wheel disc which are coaxially connected, the surface of the blade belongs to a spatial three-dimensional curved surface, the blade comprises a rear blade root, a front blade root, an inlet edge, an outlet edge, a pressure surface and a suction surface, and a plurality of sections are taken between the middle of the rear blade root and the middle of the front blade root in the Z-axis direction. The cross sections are the cross sections which are obliquely divided in the direction where the blades are attached to the back face of the rear wheel disc, a rear blade root and a front blade root are captured by the two cross sections located at the ends respectively, and the inlet angle and the outlet angle of each cross section are optimally designed respectively. According to the design of the blade flow channels, the pneumatic loss and the noise level can be reduced to the maximum extent, it is guaranteed that air flow reaches the optimal state under the rated working condition, and the static pressure efficiency of the impeller is improved to an almost unprecedented height; meanwhile, the plate type blade fan has the advantages of being low in machining and manufacturing difficulty, low in machining cost, high in working efficiency and the like.

Description

Technical Field

[0001] This application relates to the field of fan technology and its applications, and in particular to a backward-curved plate-type three-dimensional flow centrifugal fan without a volute. Background Technology

[0002] Backward-curved centrifugal fans are a type of general-purpose fan that is increasingly favored and widely used in various industrial and civil fields, such as cooling units in high-speed trains, HVAC units, fresh air units, and air supply systems. Compared with traditional volute fans, volute-less fans have many advantages, including simpler construction, easier layout, and convenient installation and maintenance.

[0003] In existing technology, backward-curved centrifugal fans mainly consist of an impeller, an inlet, and a motor. The impeller is the core component of the fan, generating airflow through rotation. The inlet guides the airflow direction, and the motor provides power to the fan. Typical volute-less centrifugal fans use a single-arc blade design with a plate-like cross-section, which is convenient to manufacture due to its simple arc shape. However, the blade shape of this plate-type design does not conform to the complex airflow characteristics inside the impeller, leading to increased airflow loss, aerodynamic noise, and decreased fan efficiency. To improve efficiency and reduce noise, some volute-less centrifugal fans employ two-dimensional or even three-dimensional airfoil blade designs, where the blade cross-section is an airfoil. By adjusting the shape and angle of the airfoil, the airflow within the impeller can be influenced, achieving higher efficiency. However, impellers with airfoil cross-sections inevitably increase manufacturing difficulty and production costs.

[0004] Therefore, there is an urgent need for a new type of centrifugal fan with a volute-less structure that is easy to process and manufacture, has low processing costs, and high working efficiency. Utility Model Content

[0005] The purpose of this application is to provide a backward-curved plate-type three-dimensional flow blade centrifugal fan without a volute, so as to solve the problems of high processing and manufacturing difficulty, high processing cost and low working efficiency in the prior art.

[0006] The embodiments of this application can be implemented through the following technical solutions:

[0007] A backward-curved plate-type three-dimensional flow centrifugal fan without a volute includes a rear impeller, blades, and a front impeller. The blades are connected between the back of the rear impeller and the front impeller, which are coaxially arranged. The surface of the blade is a three-dimensional curved surface. The blade includes a rear blade root, a front blade root, an inlet edge, an outlet edge, a pressure surface, and a suction surface. The rear blade root is the curved surface that connects the blade to the back of the rear impeller, and the front blade root is the curved surface that connects the blade to the back of the front impeller.

[0008] Along the Z-axis inlet and outlet direction, several cross sections are taken between the middle of the rear blade root and the middle of the front blade root. The cross section is a cross section that is obliquely divided along the direction where the blade is attached to the back of the rear wheel disk. The two cross sections at the ends respectively capture the rear blade root and the front blade root.

[0009] In each cross section, the outline of the pressure surface is a cross section profile. The angle between the two tangents at the endpoint of the inlet side of the cross section profile is denoted as the inlet angle α, and the angle between the two tangents at the endpoint of the outlet side of the cross section profile is denoted as the outlet angle β.

[0010] Along the front-rear direction from the front wheel to the rear wheel, the inlet angle α of the section adjacent to the front wheel is greater than the inlet angle α of the section adjacent to the rear wheel, and the inlet angle α of the section adjacent to the rear wheel is greater than the inlet angle α of the section in front of it; the outlet angle β of the section adjacent to the front wheel is greater than the outlet angle β of the section behind it, and the outlet angle β of the section adjacent to the rear wheel is greater than the outlet angle β of the section in front of it.

[0011] Furthermore, the inlet angle α and outlet angle β of each section are determined in the following ways:

[0012] On the pressure surface, the endpoint where the cross section intersects with the inlet edge is denoted as point N, and the endpoint where the cross section intersects with the outlet edge is denoted as point M. The intersection line of the cross section and the pressure surface is curve NM, which is denoted as the cross section profile. Two tangents are drawn on the cross section profile at points N and M, respectively, and are denoted as tangent A and tangent D.

[0013] Next, draw a straight line perpendicular to the back of the rear wheel disc, intersecting the Z-axis, with the intersection point located at the center of the center hole end of the rear wheel disc. This straight line is denoted as the E-section. Within the section, draw two perpendicular lines from points N and M, respectively, perpendicular to the direction of the E-section. The intersection point of the two perpendicular lines with the E-section is O. In the plane where NMO is located, draw a front circle with the straight line NO as the leading radius. The tangent of this front circle at N is denoted as the B-tangent. Similarly, in the plane where NMO is located, draw a rear circle with the straight line MO as the trailing radius. The tangent of this rear circle at M is denoted as the C-tangent. The inlet angle is ∠BNA, and the outlet angle is ∠DMC.

[0014] Furthermore, along the Z-axis, at least five spaced cross sections are taken between the middle of the posterior leaf root and the middle of the anterior leaf root. Each cross section is a first cross section, a second cross section, a third cross section, a fourth cross section, and a fifth cross section. The inlet angles α of each cross section are α1, α2, α3, α4, and α5, respectively, where α5>α1>α2>α3>α4. The outlet angles β of each cross section are β1, β2, β3, β4, and β5, respectively, where β5>β4, and β1>β2>β3>β4.

[0015] Furthermore, the inlet angle α1 of the first section ranges from 7.6° to 15.6°, the inlet angle α2 of the second section ranges from 4.6° to 12.6°, and the inlet angle α5 of the fifth section ranges from 12.9° to 20.9°.

[0016] Furthermore, the inlet angle α3 of the third section ranges from 3.2° to 11.2°, and the inlet angle α4 of the fourth section ranges from 1.7° to 9.7°.

[0017] Furthermore, the exit angle β1 of the first section ranges from 39.3° to 43.3°, and the exit angle β2 of the second section ranges from 32.5° to 36.5°.

[0018] Furthermore, the exit angle β4 of the fourth section ranges from 29.1° to 33.1°, and the exit angle β5 of the fifth section ranges from 30.6° to 34.6°.

[0019] Furthermore, the exit angle β3 of the third section ranges from 29.7° to 33.7°.

[0020] Furthermore, at point O within any cross section, a vertical extension line is drawn along the Z-axis. The intersection of this vertical extension line and the cross section profile is H, and ∠HON is denoted as the position angle γ. The position angle γ3 of the third cross section is greater than the position angle γ2 of the second cross section Q2, and the position angle γ3 of the third cross section is greater than the position angle γ4 of the fourth cross section, making part of the leading edge of the inlet side convex outward.

[0021] Furthermore, the trailing edge of the outlet side is concave, and the chord length C of each cross-section is different.

[0022] Furthermore, the exit edge at the location of the second cross-section is designed to be concave, that is, the chord length d of the second cross-section is... c2 The chord length d is smaller than that of the first cross section c1 And the chord length d of the second section c2 The chord length d is less than that of the third section. c3 .

[0023] The embodiments of this application provide a backward-curved plate-type three-dimensional flow blade centrifugal fan without a volute, which has at least the following beneficial effects:

[0024] The blades in this application are structurally improved through the analysis of the internal flow field of the wind turbine impeller. By selecting appropriate blade inlet and outlet angles and chord lengths for multiple blade sections, the aerodynamic performance of each blade section is optimized. The concave design of the blade trailing edge makes the flow field on the blade pressure surface more uniform and further improves the impeller efficiency. In particular, in the actual test of A-type inlet performance, the measured impeller efficiency can reach up to 82.2%. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a backward-curved plate-type three-dimensional flow blade centrifugal fan without a volute according to this application;

[0026] Figure 2 This is a side view of the rear wheel in this application;

[0027] Figure 3 This is a side view of the front vane disk in this application;

[0028] Figure 4 This is a three-dimensional structural diagram of the blade in this application;

[0029] Figure 5 This is a schematic diagram showing the position and dimensions of the cross-section of the blade in this application;

[0030] Figure 6 This is a schematic diagram of the first cross-section of the blade in this application;

[0031] Figure 7 This is a schematic diagram of the second cross-section of the blade in this application;

[0032] Figure 8 This is a schematic diagram of the third cross-section of the blade in this application;

[0033] Figure 9 This is a schematic diagram of the fourth cross-section of the blade in this application;

[0034] Figure 10 This is a schematic diagram of the fifth cross-section of the blade in this application;

[0035] Figure 11 Pressure cloud diagrams of the centrifugal fan blade trailing edge under different shapes in the outlet region;

[0036] Figure 12 This is a velocity contour plot of the rotating surface at the impeller inlet of the centrifugal fan.

[0037] Figure 13 A comparative curve of the measured static pressure data for each example;

[0038] Figure 14 A comparative curve of the measured static pressure efficiency for each example.

[0039] Numbers in the diagram

[0040] 1-Rear wheel disc; 11-Outer edge of rear wheel disc; 12-Center hole end; 13-Transition surface; 2-Blade; 21-Rear blade root; 22-Front blade root; 23-Inlet edge; 24-Outlet edge; 25-Pressure surface; 26-Suction surface; 3-Front wheel disc; 31-Outer edge of front wheel disc; 32-Inlet end of front wheel disc;

[0041] Q1 - First section; Q2 - Second section; Q3 - Third section; Q4 - Fourth section; Q5 - Fifth section. Detailed Implementation

[0042] The present application will now be further described based on preferred embodiments and with reference to the accompanying drawings.

[0043] In addition, for ease of understanding, various components on the drawings have been enlarged (thickened) or reduced (thinned), but this is not intended to limit the scope of protection of this application.

[0044] Singular forms of words also include plural meanings, and vice versa.

[0045] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, in the description of this application, in order to distinguish different units, the terms "first," "second," etc. are used in this specification, but these are not limited by the manufacturing order, nor should they be construed as indicating or implying relative importance. Their names may differ in the detailed description and claims of this application.

[0046] The vocabulary used in this specification is for illustrative purposes and is not intended to limit the scope of this application. It should also be noted that, unless otherwise expressly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection via an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of these terms in this application.

[0047] like Figures 1 to 4As shown, a rearward-curved plate-type three-dimensional flow centrifugal fan without a volute includes a rear impeller 1, blades 2, and a front impeller 3. The rear impeller 1 and the front impeller 3 are arranged coaxially, and this axis is denoted as the Z-axis. The two ends of the rear impeller 1 are open, with one end being a wide-diameter outer edge 11 and the other end being a narrow-diameter central hole end 12. The outer edge 11 and the central hole end 12 of the rear impeller smoothly transition to a transition surface 13. The transition surface 13 is located on the back side of the rear impeller 1 that is obliquely arranged towards the front impeller 3, making the rear impeller 1 a conical structure.

[0048] In some preferred embodiments, the front wheel 3 is a disc-shaped structure that folds inward. Both ends of the front wheel 3 are open, with one end being the outer edge 31 of the large-diameter front wheel 3 and the other end being the inlet end 32 of the small-diameter front wheel 3, which is used to optimize the airflow at the inlet and reduce flow loss. The blade 2 is connected between the transition surface 13 of the rear wheel 1 and the end where the outer edge 31 of the front wheel 3 is located. The surface of the blade 2 is a three-dimensional curved surface in space. There are several blades 2, which are arranged along the circumference of the wheel 3.

[0049] For ease of description, the direction of the fan's rotation axis is marked as the Z-axis, and the airflow direction is from the negative direction of the Z-axis to the positive direction.

[0050] Specifically, the blade 2 includes a rear blade root 21, a front blade root 22, an inlet edge 23, an outlet edge 24, a pressure surface 25, and a suction surface 26. The curved surface of the blade 2 connected to the back of the rear wheel disk 1 is the rear blade root 21, and the curved surface of the blade 2 connected to the back of the front wheel disk 3 is the front blade root 22. The inlet edge 23 is the edge where the airflow enters, and the outlet edge 24 is the edge where the airflow exits. The pressure surface 25 is the surface on which the blade 2 performs work. The edge of the blade 2 adjacent to the rear wheel disk 1 is the trailing edge, and the edge of the blade 2 adjacent to the front wheel disk 3 is the leading edge. The trailing edge of the outlet edge 24 is connected to the end of the transition surface 13 adjacent to the outer edge 11 of the rear wheel disk, and the trailing edge of the inlet edge 23 is connected to the end of the transition surface 13 adjacent to the center hole end 12.

[0051] As blade 2 rotates, it draws air in from its center and then throws it outwards through centrifugal force, forming an airflow. Unlike typical duct flow, where the velocity is higher at the center and lower near the wall, centrifugal fans exhibit the opposite velocity distribution: high velocity at the edges and lowest near the center. For example, the airflow velocity at the leading edge of blade 2's inlet 23 is higher, while the velocity at the center is lower. This same velocity trend is observed in the velocity cloud diagram of the impeller inlet's rotating surface. This velocity distribution should be considered when designing the blades. Figure 12 As shown, the red area represents the high-speed region. Therefore, in order to design a blade structure that matches the airflow characteristics in the flow field of the volute-less centrifugal fan, the applicant divides any blade 2 into sections along the airflow direction in the flow field of the volute-less centrifugal fan and optimizes the inlet and outlet angles and chord length of each section.

[0052] Specifically, along the Z-axis inlet and outlet direction, several cross sections are taken between the middle of the rear blade root 21 and the middle of the front blade root 22. The cross section is a cross section of the blade 2 obliquely divided along the direction of the back of the rear wheel disk 1. The two cross sections at the ends respectively capture the rear blade root 21 and the front blade root 22.

[0053] In each cross section, the outline of the pressure surface 25 is a cross section profile. The angle between the two tangents at the endpoint of the inlet edge 23 in the cross section profile is denoted as the inlet angle α, and the angle between the two tangents at the endpoint of the outlet edge 24 in the cross section profile is denoted as the outlet angle β.

[0054] Along the front-rear direction from the front wheel 3 to the rear wheel 1, the inlet angle α of the section adjacent to the front wheel 3 is greater than the inlet angle α of the section adjacent to the rear wheel 1, and the inlet angle α of the section adjacent to the rear wheel 1 is greater than the inlet angle α of the section in front of it; the outlet angle β of the section adjacent to the front wheel 3 is greater than the outlet angle β of the section behind it, and the outlet angle β of the section adjacent to the rear wheel 1 is greater than the outlet angle β of the section in front of it.

[0055] In some preferred embodiments, along the Z-axis, five spaced cross-sections are taken between the middle of the posterior leaf root 21 and the middle of the anterior leaf root 22. These cross-sections are designated as a first cross-section Q1, a second cross-section Q2, a third cross-section Q3, a fourth cross-section Q4, and a fifth cross-section Q5. Detailed schematic diagrams of each cross-section are provided below. Figures 6 to 10 The first section Q1 captures the rear blade root 21, and the second section Q2 captures the front blade root 22. This is used to capture more sections and make full use of the airflow in the fan to design each section in detail, so as to effectively reduce turbulence dissipation and reduce power consumption.

[0056] Specifically, taking any cross section among the equally spaced cross sections as an example, on the pressure surface 25, the endpoint where the cross section intersects with the inlet edge 23 is denoted as point N, the endpoint where the cross section intersects with the outlet edge 24 is denoted as point M, and the intersection line of the cross section and the pressure surface is curve NM, denoted as the cross section profile. Two tangents are drawn on the cross section profile at points N and M, respectively, and denoted as tangent A and tangent D.

[0057] Next, draw a straight line perpendicular to the transition surface 13, intersecting the Z-axis, with the intersection point located at the center of the central hole end 12. This straight line is denoted as the E-section. Within the cross-section, draw two perpendicular lines from points N and M, respectively, perpendicular to the direction of the E-section. The intersection point of the two perpendicular lines with the E-section is point O. In the plane containing NMO, draw a front circle with the straight-line distance of line NO as the leading radius. The leading radius is denoted as R. NO The tangent to the front circle at point N is denoted as tangent B. Similarly, in the plane containing NMO, a rear circle is constructed with the straight-line distance from line MO as the rear radius, denoted as R. MO The tangent to the rear circle at point M is denoted as the G tangent, the inlet angle α is ∠BNA, and the outlet angle β is ∠DMG.

[0058] The leading edge radii within the first section Q1, the second section Q2, the third section Q3, the fourth section Q4, and the fifth section Q5 are denoted as R. NO1 R NO2 R NO3 R NO4 R NO5 The radii of the trailing edges within the first section Q1, the second section Q2, the third section Q3, the fourth section Q4, and the fifth section Q5 are denoted as R. MO1 R MO2 R MO3 R MO4 R MO5 .

[0059] In some preferred embodiments, along the axial direction from the rear wheel 1 to the front wheel 3, at least five equidistant cross-sections are taken between the middle of the rear leaf root 21 and the middle of the front leaf root 22, and the cross-sectional lines of each cross-section are distributed as follows: Figure 3As shown, the cross section is a cross section cut by the blade 2 along the oblique extension of the back of the rear wheel disk 1. Along the direction from the rear wheel disk 1 to the front wheel disk 3, each cross section is a first cross section Q1, a second cross section Q2, a third cross section Q3, a fourth cross section Q4, and a fifth cross section Q5. The inlet angles α of each cross section are α1, α2, α3, α4, and α5, respectively, where α5>α1>α2>α3>α4. The outlet angles β of each cross section are β1, β2, β3, β4, and β5, respectively, where β5>β4, and β1>β2>β3>β4. This allows each cross section of the blade 2 to achieve optimal aerodynamic performance, reduces the resistance of the airflow when flowing through the flow channel, and obtains a uniform pressure rise near the outlet edge when the airflow exits the blade trailing edge, thereby improving the working efficiency of the fan.

[0060] In some preferred embodiments, in order to reduce the airflow loss at the inlet angle α, the design of the tangent A should be as consistent as possible with the airflow direction at the inlet edge 23. To achieve this, the position angle γ of the inlet edge 23 can be adjusted. However, since the airflow field is different at different positions, if the same position angle γ is used, the airflow in the flow field cannot be utilized efficiently. Therefore, the applicant has optimized the position angle γ of each section so that the leading edge of the inlet edge 23 is convex.

[0061] Specifically, within any cross-section, a vertical extension line is drawn from point O along the Z-axis. The intersection of this vertical extension line and the cross-sectional profile is H. The position angle γ is ∠HON. The position angles γ within the first cross-section Q1, the second cross-section Q2, the third cross-section Q3, the fourth cross-section Q4, and the fifth cross-section Q5 are γ1, γ2, γ3, γ4, and γ5, respectively. The position angle γ3 of the third cross-section Q3 is greater than the position angle γ2 of the second cross-section Q2, and the position angle γ3 of the third cross-section Q3 is greater than the position angle γ4 of the fourth cross-section Q4, i.e., γ3>γ2 and γ3>γ4, causing part of the leading edge of the inlet edge 23 to be convex.

[0062] Furthermore, the trailing edge of the outlet edge 24 is concave, and the straight-line distance between point N and point M within the cross-section is a chord C, the length of which is denoted as d. c The lengths of the chords within the first section Q1, the second section Q2, the third section Q3, the fourth section Q4, and the fifth section Q5 are denoted as γ. c1 d c2 d c3 d c4 d c5 The length of the chord C varies in different cross sections, which makes the flow field on the pressure surface of the blade more uniform and further improves the impeller efficiency.

[0063] The reason for setting the trailing edge of the outlet edge 24 to be concave is that the trailing edge is a high-pressure concentration area. If the trailing edge were set to a smooth contour, it would lead to uneven pressure distribution at the trailing edge across different sections. Figure 11 As shown, Figure 11 For the pressure cloud diagrams of the trailing edge under different shapes, Figure 11 In order to visually represent the pressure distribution in different parts of the blade, different pressures in the blade are marked with different colors. The area at the trailing edge is the high-pressure zone, i.e., the red area in the cloud map. As can be seen from the figure, when the trailing edge is straight, the high-pressure zone at the outlet is too concentrated, which is not conducive to the impeller's work. After adopting the concave shape of the trailing edge in this application, the pressure distribution near the outlet edge is more uniform, and the pressure rise at the trailing edge is more uniform for each section, which is beneficial to improving the impeller efficiency.

[0064] In some preferred embodiments, the exit edge 24 at the location of the second cross-section Q2 is set to be concave, that is, the chord length d of the second cross-section Q2 is... c2 The chord length d is smaller than that of the first cross section Q1 c1 And the chord length d of the second section Q2 c2 The chord length d is smaller than that of the third section Q3. c3 This makes the pressure distribution near the exit edge more uniform due to the concave tail edge.

[0065] The static pressure efficiency of a volute-less centrifugal fan is considered to ensure that the fan can meet the requirements of air volume and air pressure while optimizing the overall performance of the system, reducing energy consumption, thereby improving the energy efficiency and energy saving level of the entire fan system, reducing carbon emissions, and saving operating costs. Therefore, static pressure efficiency is often used as a major indicator to evaluate the performance of a volute-less centrifugal fan.

[0066] In this application, by optimizing the design of the blades, the static pressure efficiency of each section of the blades basically reaches more than 70%, which can ensure that all areas of the blades work efficiently.

[0067] Specific embodiments are given below.

[0068] Example 1:

[0069] The diameter of the outer edge 11 of the rear disc of the rear disc 1 It is 598mm long, with a center hole diameter of 12mm. The diameter is 190mm, the straight-line distance d1 between the outer edge 11 of the rear wheel disc and the center hole end 12 along the Z-axis is 130mm, and the diameter of the outer edge 31 of the front wheel disc is... The diameter is 659mm, and the inlet end diameter of the front wheel disc is 32mm. For example, the distance from the center hole end 12 along the Z-axis to the outer edge 31 of the front wheel disk along the Z-axis is 270mm, with a diameter of 496mm.

[0070] Along the axial direction from the rear wheel 1 to the front wheel 3, five equally spaced cross sections are taken between the middle of the rear blade root 21 and the middle of the front blade root 22. These cross sections are designated as the first cross section Q1, the second cross section Q2, the third cross section Q3, the fourth cross section Q4, and the fifth cross section Q5. The geometric dimensions of each cross section are shown in Table 1.1 below.

[0071] Table 1.1 Geometric Dimensions of Each Section

[0072]

[0073] For detailed static pressure and static pressure efficiency data of this fan on a standard fan performance test bench, please refer to [link / reference]. Figure 13 and Figure 14 .

[0074] Example 2:

[0075] The diameter of the outer edge 11 of the rear disc of the rear disc 1 It is 598mm long, with a center hole diameter of 12mm. The diameter is 190mm, the straight-line distance d1 between the outer edge 11 of the rear wheel disc and the center hole end 12 along the Z-axis is 130mm, and the diameter of the outer edge 31 of the front wheel disc is... The diameter is 659mm, and the inlet end diameter of the front wheel disc is 32mm. For example, the distance from the center hole end 12 along the Z-axis to the outer edge 31 of the front wheel disk along the Z-axis is 270mm, with a diameter of 496mm.

[0076] Along the axial direction from the rear wheel 1 to the front wheel 3, five equally spaced cross sections are taken between the middle of the rear blade root 21 and the middle of the front blade root 22. These cross sections are designated as the first cross section Q1, the second cross section Q2, the third cross section Q3, the fourth cross section Q4, and the fifth cross section Q5. The geometric dimensions of each cross section are shown in Table 2.1 below.

[0077] Table 2.1 Geometric Dimensions of Each Section

[0078]

[0079] For detailed static pressure and static pressure efficiency data of this fan on a standard fan performance test bench, please refer to [link / reference]. Figure 13 and Figure 14 .

[0080] Comparative example:

[0081] The diameter of the outer edge 11 of the rear disc of the rear disc 1 It is 598mm long, with a center hole diameter of 12mm. The diameter is 190mm, the straight-line distance d1 between the outer edge 11 of the rear wheel disc and the center hole end 12 along the Z-axis is 130mm, and the diameter of the outer edge 31 of the front wheel disc is... The diameter is 659mm, and the inlet end diameter of the front wheel disc is 32mm. For example, the distance from the center hole end 12 along the Z-axis to the outer edge 31 of the front wheel disk along the Z-axis is 270mm, with a diameter of 496mm.

[0082] Along the axial direction from the rear wheel 1 to the front wheel 3, five equally spaced cross sections are taken between the middle of the rear blade root 21 and the middle of the front blade root 22. These cross sections are designated as the first cross section Q1, the second cross section Q2, the third cross section Q3, the fourth cross section Q4, and the fifth cross section Q5. The geometric dimensions of each cross section are shown in Table 3.1 below.

[0083] Table 3.1 Geometric Dimensions of Each Section

[0084]

[0085] For detailed static pressure and static pressure efficiency data of this fan on a standard fan performance test bench, please refer to [link / reference]. Figure 13 and Figure 14 .

[0086] pass Figure 13 and Figure 14 Comparative analysis of measured data shows that the blade flow channel design in Examples 1 and 2 can minimize aerodynamic losses and noise levels, ensuring optimal airflow under rated operating conditions, thereby increasing the impeller static pressure efficiency to an almost unprecedented level. Following the design logic, actual measurements show a maximum static pressure efficiency of 82%. However, compared to Examples 1 and 2, the maximum impeller static pressure efficiency in the comparative example cannot reach 82%, which represents a significant breakthrough in this field.

[0087] The specific embodiments of this application have been described in detail above. For those skilled in the art, several improvements and modifications can be made to this application without departing from the principle of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A backward-curved plate-type three-dimensional flow centrifugal fan without a volute, comprising a rear impeller (1), blades (2), and a front impeller (3), wherein the blades (2) are connected between the back of the rear impeller (1) and the front impeller (3) arranged coaxially, and the surface of the blades (2) is a three-dimensional curved surface, characterized in that: The blade (2) includes a rear blade root (21), a front blade root (22), an inlet edge (23), an outlet edge (24), a pressure surface (25), and a suction surface (26). The rear blade root (21) is a curved surface that connects the blade (2) to the back of the rear wheel disk (1), and the front blade root (22) is a curved surface that connects the blade (2) to the back of the front wheel disk (3). Along the Z-axis inlet and outlet direction, several cross sections are taken between the middle of the rear blade root (21) and the middle of the front blade root (22). The cross section is a cross section of the blade (2) that is obliquely divided along the direction of the back of the rear wheel disk (1). The two cross sections at the ends respectively capture the rear blade root (21) and the front blade root (22). In each cross section, the outline of the pressure surface (25) is a cross section profile. The angle between the two tangents at the endpoint of the inlet edge (23) in the cross section profile is denoted as the inlet angle α, and the angle between the two tangents at the endpoint of the outlet edge (24) in the cross section profile is denoted as the outlet angle β. Along the front-rear direction from the front wheel (3) to the rear wheel (1), the inlet angle α of the section adjacent to the front wheel (3) is greater than the inlet angle α of the section adjacent to the rear wheel (1), and the inlet angle α of the section adjacent to the rear wheel (1) is greater than the inlet angle α of the section in front of it; the outlet angle β of the section adjacent to the front wheel (3) is greater than the outlet angle β of the section behind it, and the outlet angle β of the section adjacent to the rear wheel (1) is greater than the outlet angle β of the section in front of it.

2. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 1, characterized in that: The inlet angle α and outlet angle β of each section are determined in the following ways: On the pressure surface (25), the endpoint where the cross section intersects with the inlet edge (23) is marked as point N, and the endpoint where the cross section intersects with the outlet edge (24) is marked as point M. The intersection line of the cross section and the pressure surface is curve NM, which is called the cross section profile. Two tangents are drawn on the cross section profile at points N and M, respectively, and are marked as tangent A and tangent D. Next, draw a straight line perpendicular to the back of the rear wheel (1) that intersects the Z-axis and the intersection point is located at the center of the center hole end (12) of the rear wheel (1). This straight line is denoted as the E-section. In the cross section, draw two perpendicular lines from points N and M, respectively, perpendicular to the direction of the E-section. The intersection point of the two perpendicular lines with the E-section is O. In the plane where NMO is located, draw a front circle with the straight line NO as the leading radius. The tangent of this front circle at N is denoted as the B-tangent. Similarly, in the plane where NMO is located, draw a rear circle with the straight line MO as the trailing radius. The tangent of this rear circle at M is denoted as the d-tangent. The inlet angle is ∠BNA, and the outlet angle is ∠DMC.

3. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 2, characterized in that: Along the Z-axis, at least five cross sections are taken at intervals between the middle of the rear leaf root (21) and the middle of the front leaf root (22). Each cross section is a first cross section (Q1), a second cross section (Q2), a third cross section (Q3), a fourth cross section (Q4), and a fifth cross section (Q5). The inlet angles α of each cross section are α1, α2, α3, α4, and α5, respectively, where α5 > α1 > α2 > α3 > α4. The outlet angles β of each cross section are β1, β2, β3, β4, and β5, respectively, where β5 > β4, and β1 > β2 > β3 > β4.

4. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 3, characterized in that: The inlet angle α1 of the first section (Q1) ranges from 7.6° to 15.6°, the inlet angle α2 of the second section (Q2) ranges from 4.6° to 12.6°, and the inlet angle α5 of the fifth section (Q5) ranges from 12.9° to 20.9°.

5. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 3, characterized in that: The inlet angle α3 of the third section (Q3) ranges from 3.2° to 11.2°, and the inlet angle α4 of the fourth section (Q4) ranges from 1.7° to 9.7°.

6. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 3, characterized in that: The exit angle β1 of the first section (Q1) ranges from 39.3° to 43.3°, and the exit angle β2 of the second section (Q2) ranges from 32.5° to 36.5°.

7. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 3, characterized in that: The exit angle β4 of the fourth section (Q4) ranges from 29.1° to 33.1°, and the exit angle β5 of the fifth section (Q5) ranges from 30.6° to 34.6°.

8. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 3, characterized in that: The exit angle β3 of the third section (Q3) ranges from 29.7° to 33.7°.

9. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 2, characterized in that: A vertical extension line is drawn from point O in any cross section along the Z-axis. The intersection of this vertical extension line and the cross section profile is H. ∠HON is denoted as the position angle γ. The position angle γ3 of the third cross section (Q3) is greater than the position angle γ2 of the second cross section Q2, and the position angle γ3 of the third cross section (Q3) is greater than the position angle γ4 of the fourth cross section (Q4), so that part of the leading edge of the inlet edge (23) is convex.

10. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 3, characterized in that: The tail edge of the exit edge (24) is concave, and the chord length C of each section is different.

11. The backward-curved plate-type three-dimensional flow blade centrifugal fan without volute as described in claim 10, characterized in that: The exit edge (24) at the location of the second section (Q2) is set to be concave, that is, the chord length d of the second section (Q2) is... c2 The chord length d is smaller than that of the first cross section (Q1). c1 And the chord length d of the second section (Q2) c2 The chord length d is smaller than that of the third section (Q3). c3 .

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