Axial diffuser and fan

Abstract

The application discloses an axial diffuser and a fan, wherein the axial diffuser comprises a body and a plurality of diffuser blades which are circumferentially spaced on the outer periphery of the body, the diffuser blades have opposite suction surfaces and pressure surfaces, and at least one of the diffuser blades is provided with a gap, the gap penetrates the diffuser blade body to communicate the suction surface and the pressure surface. By introducing the high-energy airflow of the pressure surface into the suction surface through the gap, the energy supplement for the boundary layer is effectively performed, and the flow separation phenomenon is significantly inhibited. When the structure is applied to a centrifugal fan with axial air outlet, the outlet air pressure can be obviously improved, and the operation noise can be effectively controlled and reduced. The scheme has simple structure, low manufacturing cost and significantly improved comprehensive performance.

Description

Technical Field

[0001] This application relates to the technical field of fans, and more particularly to an axial diffuser and a fan. Background Technology

[0002] In centrifugal compressors used in industrial centrifugal compressors and micro gas turbines, axial diffusers are widely used to convert circumferentially swirling airflow into axial flow, thereby converting the tangential velocity component into static pressure and further increasing the outlet pressure. However, since axial diffusers typically operate under adverse pressure gradient conditions, significant boundary layer separation easily occurs on the suction surface of their blades. This not only causes substantial flow losses but also reduces the compressor's stability margin. Therefore, the industry continues to focus on optimizing and improving axial diffusers, such as by employing tandem blade arrays or adjustable blades.

[0003] In contrast, centrifugal fans used in ventilators typically do not employ axial diffuser structures. This is presumably because, firstly, boundary layer separation of the axial diffuser blades can generate significant noise, while ventilators have strict requirements for low-noise operation; secondly, ventilator fans often operate under low-flow conditions, and in such conditions, the use of an axial diffuser could lead to a drop in outlet pressure, which would be detrimental to system performance.

[0004] like Figure 1 As shown, in some existing ventilators using axial-flow centrifugal fans, the airflow flows out of the impeller outlet in the direction of the arrow, first changing from radial to axial flow through a bend, and then flows through an annular channel without an axial diffuser. Afterward, the airflow changes back to radial flow through a bend at the motor end, and finally, with the help of centripetal guide vanes, the circumferential swirling flow is adjusted into axial outflow.

[0005] This structure has the following key problems: the high airflow velocity at the impeller outlet and the large swirling intensity (typically the airflow angle with the axis is greater than 75°), resulting in a spiral flow within the annular channel, significantly extending the flow path and causing substantial pressure loss along the flow path. Simultaneously, due to the lack of an axial diffuser to effectively slow the airflow, the inlet dynamic pressure of the centripetal guide vanes is too high, further increasing the pressure loss during the guide flow process.

[0006] like Figure 2 As shown, if a traditional axial diffuser is installed in the annular channel, although it has a certain diffusion effect, under the influence of the reverse pressure gradient, severe boundary layer separation is likely to occur on the suction surface of the blade, forming a large-scale low-speed vortex region. This will not only increase airflow noise, but also cause the outlet static pressure to drop under low flow conditions.

[0007] Furthermore, when the fan flow rate decreases, the radial velocity of the airflow at the impeller outlet decreases, while the tangential velocity at the impeller rim remains essentially unchanged. This leads to a further increase in the swirl angle of the outlet airflow, resulting in... Figure 4The inlet swirl angle α of the central axial diffuser increases accordingly, exacerbating flow separation on the suction side. Therefore, the aforementioned negative effects are particularly significant under low flow rate conditions. Utility Model Content

[0008] This application provides an axial diffuser that significantly increases outlet air pressure while also controlling noise.

[0009] This application provides an axial diffuser, including a body and a plurality of diffuser blades circumferentially spaced around the body. The diffuser blades have opposing suction surfaces and pressure surfaces. At least one of the diffuser blades has a slit that penetrates the diffuser blade body to connect the suction surface and the pressure surface.

[0010] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0011] Optionally, the angle between the extension direction of the slit and the tangent direction of the mid-arc line of the blade at the slit location is within 15°-25°.

[0012] Optionally, the width of the diffuser blade gradually increases from its leading edge to its trailing edge.

[0013] Optionally, all of the diffuser blades are provided with the slots.

[0014] Optionally, the width of the slit is 1% to 8% of the chord length of the diffuser blade.

[0015] Optionally, the width of the gap is 3% to 5% of the chord length of the diffuser blade.

[0016] Optionally, the slit is located in the middle region of the blade.

[0017] This application also provides a fan, including a housing and an impeller and a motor disposed within the housing. The motor is used to drive the impeller to rotate. The housing has opposing air inlets and outlets. The fan is provided with an annular channel, and the axial diffuser is disposed inside the annular channel.

[0018] Optionally, an annular channel is provided between the housing and the motor.

[0019] Optionally, the body of the axial diffuser is sleeved and fixed on the motor.

[0020] Optionally, the front end of the motor is connected to the impeller, and the rear end is provided with guide vanes extending radially.

[0021] The axial diffuser disclosed in this application features a slotted structure on the conventional diffuser blades. This design effectively replenishes the boundary layer by introducing high-energy airflow from the pressure side to the suction side, thereby significantly suppressing flow separation. When applied to a centrifugal fan with axial exhaust, this structure can significantly increase the outlet air pressure while effectively controlling and reducing operating noise. This solution has a simple structure, low manufacturing cost, and significantly improved overall performance. Attached Figure Description

[0022] Figure 1 This is a structural diagram of a wind turbine based on existing technology; Figure 2 This is a schematic diagram of the structure of an existing axial diffuser; Figure 3 for Figure 2 Velocity contour plot and streamline contour plot of a central axial diffuser blade; Figure 4 for Figure 2 A schematic diagram of the swirl angle at the inlet end of the intermediate blade; Figure 5 This is a schematic diagram of the structure of an axial diffuser according to an embodiment of this application; Figure 6 for Figure 5 Schematic diagram of the structure of a diffuser blade; Figure 7 This is a schematic diagram of the structure of a fan according to an embodiment of this application; Figure 8 for Figure 6 Velocity cloud map and streamline cloud map of a medium-sized wind turbine; Figure 9 for Figure 6 and Figure 2 The PQ performance comparison curves of the axial diffuser.

[0023] The annotations in the figure are explained as follows: 10. Axial diffuser; 100. Body; 101. Inflow side; 102. Outflow side; 200, diffuser blade; 200b, blade; 210b, suction surface; 220b, pressure surface; 210. Suction surface; 211. Midpoint; 220. Pressure surface; 230. Gap; 231. Inlet; 232. Outlet; 400. Casing; 410. Air inlet; 420. Air outlet; 430. First elbow; 440. Second elbow; 450. Annular channel; 500. Impeller; 600, motor; 610, output shaft; 700, guide vanes. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] It should be noted that when a component is said to be "connected" to another component, it can be directly connected to the other component or it can be connected to a component in between. When a component is said to be "set on" another component, it can be directly set on the other component or it may be set to a component in between.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] In this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number or order of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0028] like Figures 5-7 As shown, this application provides an axial diffuser 10, which can be installed within an annular channel 450 of a fan. The annular channel 450 extends axially, and the internal airflow flows in a spiral motion around its axis. The axial direction of the axial diffuser 10 is aligned with the direction of the annular channel, and it has an inflow side 101 and an outflow side 102 sequentially along the airflow direction. In the following description, unless otherwise specified, the axial, circumferential, and radial directions are all based on the axial direction of the axial diffuser 10.

[0029] The axial diffuser includes a body 100 and a plurality of diffuser blades 200. The body 100 extends axially and has an annular structure, and the plurality of diffuser blades 200 are circumferentially spaced and protrude from the outer periphery of the body 100. In the radial direction, each diffuser blade 200 has a proximal end connected to the body 100 and an outer end away from the body. In a preferred embodiment, the outer end of the diffuser blade 200 is close to the inner wall of the annular channel 450 to ensure that the airflow flowing through the annular channel 450 passes through the diffuser blade 200.

[0030] The diffuser blade 200 and the body 100 are integrally molded. Each diffuser blade 200 includes two surfaces in the circumferential direction: a suction surface 210 and a pressure surface 220. In the embodiment shown in the figures, the diffuser blade 200 extends in a curved manner from the inflow side 101 to the outflow side 102, with the curvature such that the angle between the line connecting the inflow end and the outflow end of the diffuser blade 200 and the airflow direction is less than 90 degrees. The suction surface 210 protrudes outward, and the pressure surface 220 is recessed inward. In this embodiment, at least one diffuser blade 200 is provided with a slit 230, which penetrates the diffuser blade 200 along its thickness direction, i.e., connects the suction surface 210 and the pressure surface 220 in the circumferential direction.

[0031] First, such as Figure 2 and Figure 3 As shown, the blade 200b in the prior art is complete and has no gaps 230. Taking one blade 200b as an example, the airflow is split into two by the blade 200b. The first stream is introduced into the pressure surface 220b. Because the pressure surface 220b has a concave structure, the first stream of airflow loses little energy when passing through the pressure surface 220b and still possesses relatively high energy, including kinetic energy. The second stream is introduced into the suction surface 210b. Because the suction surface 210b has a convex structure, the second stream of airflow is blocked when passing through the suction surface 210b and loses more energy.

[0032] The axial diffuser 10 in this embodiment effectively replenishes the boundary layer by introducing high-energy airflow from the pressure surface 220 into the suction surface 210 through the slot 230, thus obtaining sufficient kinetic energy to resist the pressure difference force in the opposite direction and significantly suppressing flow separation. When this structure is applied to a centrifugal fan with axial air output, it can significantly increase the outlet air pressure while effectively controlling and reducing operating noise. Furthermore, this application creates slots on the blades of existing axial diffusers, resulting in a simple structure and low manufacturing cost.

[0033] To further increase the outlet air pressure and reduce operating noise, all diffuser blades 200 are provided with slots 230, and each slot 230 has the same structure. In one embodiment, the proximal end of the slot 230 extends to the outer peripheral surface of the body 100 and the outer end extends to the outer end of the diffuser blade 200, that is, the outer end of the slot 230 is open.

[0034] like Figure 6 As shown, in one embodiment, the slit 230 extends with a uniform width and in a straight direction. Along the airflow direction, the slit 230 has an inlet 231 and an outlet 232, wherein the outlet 232 is located at the starting position of the airflow diversion. Figure 2 and Figure 3As shown, the starting position of the diversion is approximately located at the midpoint 211 of the suction surface 210b. Therefore, in this embodiment, the outlet 232 is located near the midpoint 211 of the suction surface 210, and preferably, the outlet 232 includes the midpoint 211.

[0035] The width d of the slot 230 satisfies the following formula: d = 1% - 8%L. L is the chord length of the diffuser blade 200, which is the line connecting the inflow end and outflow end of the diffuser blade 200. Preferably, the width formula of the slot 230 is: d = 3% - 5%L. This avoids the slot 230 being too wide, which would damage the original diffuser blade profile and consequently reduce the diffusion performance at high flow rates.

[0036] In one embodiment, the extension direction of the slit 230 is the same as the flow direction of the airflow at the inlet 231 (e.g., Figure 6 The direction of the arrow is roughly the same as that of the pressure surface 220, which ensures that the high-energy airflow on the pressure surface 220 side can be introduced to the suction surface 210 side with almost no loss. In the figure, the diffuser blade 200 forms an angle σ between the tangent of the mid-arc line at the slot 230 and the extension direction of the slot 230. The angle σ satisfies 15°-25°, preferably σ=22°.

[0037] In one embodiment, the width (i.e., thickness) of the diffuser blade 200 gradually increases from the leading edge (i.e., the inflow end) to the trailing edge (i.e., the outflow end), and both the leading and trailing edges are rounded.

[0038] like Figure 7 As shown, this application also provides a fan, including a housing 400 and an impeller 500 and a motor 600 disposed within the housing 400. The housing 400 has opposing air inlets 410 and air outlets 420, both extending axially. The fan is provided with an annular channel 450, which can be entirely constructed from the housing 400, or as... Figure 7 As shown, the housing 400 and the motor 600 together form the annular channel 450. Specifically, the outer wall of the annular channel 450 is constructed by the housing 400, and the inner wall is constructed by the housing of the motor 600. The axial diffuser 10 of this application is disposed inside the annular channel 450. In some embodiments, the impeller 500 may be axial or centrifugal.

[0039] The body 100 of the axial diffuser 10 is sleeved and fixed on the motor 600. The front end of the motor 600 is provided with an output shaft 610, which is connected to the impeller 500 to make it rotate around the axial direction. The impeller 500 shown in the attached figure is a centrifugal impeller. The casing 400 is provided with a first bend 430 and a second bend 440 at the front and rear ends, respectively, for guiding the airflow. The rear end of the motor 600 is provided with guide vanes 700, which are located inside the second bend 440 and extend radially.

[0040] The specific airflow path is as follows: First, the airflow enters axially from the air inlet 410, gains energy under the action of the high-speed rotating impeller 500, and flows out radially from the axial direction; then, guided by the first bend 430, it enters the annular channel 450, where it flows in a spiral manner and is effectively pressurized by the axial diffuser; finally, the airflow turns radially again through the second bend 440, and is stably delivered axially from the air outlet 420 through the rectification and guidance of the guide vanes 700.

[0041] The advantages of the axial diffuser in this application are demonstrated from multiple aspects based on actual test data: like Figure 8 As shown, after adopting the axial diffuser of this application, flow separation is significantly suppressed, with only slight local separation occurring at the 200° trailing edge radius of the diffuser blades. This not only helps to increase the outlet pressure but also has a positive impact on reducing aerodynamic noise. Tests showed that, with the fan outlet pressure at 10 cmH2O and other components remaining unchanged, the fan equipped with the axial diffuser of this application exhibited an overall noise reduction of 1 dB(A) compared to the traditional structure. Furthermore, from... Figure 9 The performance comparison shown indicates that, under full speed and high flow conditions, the pressure rise of the fan in this application is slightly lower than that of the traditional structure; while under full speed and low flow conditions, the pressure rise of the fan in this application is significantly higher than that of the traditional fan, demonstrating superior partial load performance.

[0042] Therefore, the axial diffuser of this application incorporates a slotted structure on the conventional diffuser blades. This design effectively replenishes the boundary layer by introducing high-energy airflow from the pressure side to the suction side, thereby significantly suppressing flow separation. When this structure is applied to a centrifugal fan with axial exhaust, it can significantly increase the outlet air pressure while effectively controlling and reducing operating noise. This solution has a simple structure, low manufacturing cost, and significantly improved overall performance.

[0043] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered to be within the scope of this specification. When technical features of different embodiments are embodied in the same drawing, it can be regarded as the drawing also disclosing examples of combinations of the various embodiments involved.

[0044] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are quite specific and detailed. However, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. An axial diffuser, comprising a body and a plurality of diffuser blades circumferentially spaced around the outer periphery of the body, wherein the diffuser blades have opposing suction surfaces and pressure surfaces, characterized in that, At least one of the diffuser blades has a slit that penetrates the diffuser blade body to connect the suction surface and the pressure surface.

2. The axial diffuser according to claim 1, characterized in that, The angle between the extension direction of the slit and the tangent direction of the mid-arc line of the blade at the slit location is within 15°-25°.

3. The axial diffuser according to claim 1, characterized in that, The width of the diffuser blade gradually increases from its leading edge to its trailing edge.

4. The axial diffuser according to claim 1, characterized in that, All of the aforementioned diffuser blades are provided with the aforementioned slots.

5. The axial diffuser according to claim 1, characterized in that, The width of the slit is 1% to 8% of the chord length of the diffuser blade.

6. The axial diffuser according to claim 1, characterized in that, The width of the slit is 3% to 5% of the chord length of the diffuser blade.

7. The axial diffuser according to claim 1, characterized in that, The slit is located in the middle region of the blade.

8. A fan, characterized in that, The fan includes a housing and an impeller and a motor disposed within the housing. The motor drives the impeller to rotate. The housing has opposing air inlets and outlets. The fan is provided with an annular channel, and an axial diffuser as described in any one of claims 1 to 7 is disposed inside the annular channel.

9. The fan according to claim 8, characterized in that, The annular channel is constructed between the housing and the motor.

10. The fan according to claim 9, characterized in that, The body of the axial diffuser is sleeved and fixed on the motor.

11. The fan according to claim 9, characterized in that, The motor is connected to the impeller at the front end and has guide vanes extending radially at the rear end.

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