A low-noise centrifugal fan with Oloyd body curved blades and dual air inlets

Abstract

This invention relates to the field of fluid machinery technology, specifically disclosing an Oloy body curved blade dual-inlet low-noise centrifugal fan. This Oloy body curved blade dual-inlet low-noise centrifugal fan includes a volute, impeller, motor, front inlet, rear inlet, and outlet. The impeller includes a hub and Oloy body curved blades arranged circumferentially along the hub. The Oloy body curved blades have continuous three-dimensional curved surface features formed by truncating and spatially transforming a continuous developable Oloy body surface, and have continuously varying chord length and installation angle distribution along the impeller radial direction. This structure improves the matching between the dual-side air intake and the blade channels, reduces airflow separation and wake vortex shedding, thereby reducing operating noise while meeting airflow and static pressure requirements.

Description

Technical Field

[0001] This invention relates to the field of fluid machinery technology, and in particular to an Oloy body curved blade dual-inlet low-noise centrifugal fan. Background Technology

[0002] Centrifugal fans are commonly used power components in ventilation systems such as range hoods, air purifiers, fresh air systems, and industrial dust removal. Their aerodynamic efficiency, noise level, and operational reliability directly affect the performance of the end-user equipment. Especially in the field of kitchen appliances, range hoods usually need to operate under conditions of large air volume and high static pressure. In order to meet the smoke exhaust requirements, traditional centrifugal fans often need to increase the impeller speed, which can easily generate high aerodynamic noise and vibration noise, affecting user comfort.

[0003] Existing centrifugal fan impeller blades mainly include straight plate blades, simple circular arc blades, forward-curved blades, and ordinary backward-curved blades. Straight plate blades have a simple structure but relatively limited aerodynamic performance; simple circular arc blades typically use a single circular arc as the blade centerline, easily forming local adverse pressure gradients during airflow deflection; forward-curved blades can generate some pressure at lower speeds, but their efficiency and noise control capabilities are limited; ordinary backward-curved blades are mostly formed by radially stretching or simply lofting two-dimensional airfoils, belonging to a quasi-three-dimensional blade structure. When airflow passes over the blade surface, these blades are prone to boundary layer separation in the leading edge, suction surface, or trailing edge regions, forming wake vortices at the trailing edge, thereby increasing flow losses and aerodynamic noise. In oily fume environments such as range hoods, grease particles may also deposit on the blade surface, changing the blade surface condition and dynamic balance, further affecting the fan's aerodynamic performance and operating noise.

[0004] Regarding the overall air intake structure of centrifugal fans, most existing centrifugal fans adopt a single-sided air intake structure. After the airflow enters axially from one side of the impeller, it needs to be diverted radially to exit. This easily leads to pre-vortices, air intake deflection, and uneven flow near the air inlet, thus reducing the stability of the impeller inlet flow field and increasing intake noise. Some centrifugal fans have adopted a dual-inlet structure to improve air intake uniformity. For example, Chinese utility model patent CN203548268U discloses a bidirectional air intake centrifugal fan structure, with air inlets at both ends of the casing, air outlets on the side walls, and an impeller inside the casing. This type of dual-inlet structure can alleviate the uneven air intake problem caused by single-sided air intake to some extent, but its blade profile usually still uses traditional geometric configurations and has not fully integrated the characteristics of the dual-sided air intake flow field to systematically match the three-dimensional curved surface, radial installation angle, and chord length distribution of the blades.

[0005] Regarding the three-dimensional geometry of blades, existing centrifugal fan blades are mostly quasi-three-dimensional configurations formed by radial stretching or simple lofting of two-dimensional airfoils, lacking blade configuration designs based on continuous three-dimensional spatial surfaces. An Oroy body is a three-dimensional spatial volume composed of two orthogonal circles of equal radius and perpendicular planes, with a surface characterized by continuous developable surfaces. Publicly available information indicates applications of the overall shape of Oroy bodies in mixing and aeration scenarios; however, these applications typically utilize the complete shape of the Oroy body directly to achieve mixing or turbulence, without involving the application of locally continuous developable surfaces of the Oroy body, after truncation, spatial transformation, radial scaling, and lofting, to the structural design of centrifugal fan blades.

[0006] Regarding auxiliary measures for noise control, various local noise reduction techniques have been used individually or in combination in existing technologies. For example, Chinese invention patent application CN107605766A discloses a technical solution of setting a serrated trailing edge at the tail of a rotating blade to reduce eddy noise; Chinese invention patent CN102251986A discloses a method of improving flow, increasing efficiency, and reducing aerodynamic noise through biomimetic stripes, grooves, and serrated structures on the blade surface and blade edges; Chinese invention patent CN115263801A discloses a composite noise reduction method of setting biomimetic spherical grooves on the suction surface of the blade, setting noise-reducing serrated structures on the trailing edge of the blade, setting biomimetic spherical grooves on the surface of the volute tongue, and setting slit plates, resonant sound-absorbing layers, and micro-perforated plates inside the volute. The above-mentioned technical means can play a certain role in noise reduction in their respective application scenarios, but they are mainly concentrated on local structures such as the trailing edge of the blade, the blade surface, or the inner wall of the volute, and do not optimize the internal flow of the centrifugal fan as a whole from the perspective of the three-dimensional curved surface configuration of the blade body and its matching relationship with the dual-inlet airflow field.

[0007] In summary, existing centrifugal fans still suffer from several problems, including blade aerodynamic profiles that are mostly limited to two-dimensional stretching or simple lofting, insufficient continuity of the three-dimensional curved surface of the blades, limited matching between the dual-side air intake and the blade channels, and inadequate matching between the volute flow channel and the impeller outlet airflow. These issues easily lead to boundary layer separation and wake vortex shedding on the blade surface, making it difficult to simultaneously achieve fan efficiency, static pressure capacity, and low noise performance. Therefore, it is necessary to further improve the three-dimensional curved surface configuration of centrifugal fan blades, the dual-inlet structure, and the matching relationship of the volute flow channel. Summary of the Invention

[0008] The technical problem to be solved by this invention is that existing centrifugal fan blades are mostly limited to two-dimensional line stretching or simple lofting configurations. The three-dimensional curved surface continuity, radial parameter variation, and matching with the double-sided air inlet flow field and volute flow channel of the blades are insufficient, which easily leads to airflow separation and wake vortex shedding, making it difficult to balance fan efficiency, static pressure capacity and low noise performance. To this end, we propose an Oroy body curved surface blade double air inlet low noise centrifugal fan.

[0009] To achieve the above objectives, this application adopts the following technical solution: a low-noise centrifugal fan with dual inlet and curved blades, comprising a volute, an impeller, a motor, a front inlet, a rear inlet, and an outlet; a gradually expanding spiral air duct is formed inside the volute, and the impeller is disposed within the gradually expanding spiral air duct; the volute is used to collect and guide the airflow radially discharged from the impeller to the outlet; the impeller includes a hub and multiple curved blades arranged circumferentially along the hub; the hub is coaxially connected to the output shaft of the motor; the curved blades extend from the hub to the outer edge of the impeller; the suction surface and pressure surface of the curved blades both have a continuous surface of the Oloyed body. The developable surface, after being truncated and spatially transformed, forms a continuous three-dimensional curved surface. The Oroy body is composed of two orthogonal circles with equal radii and perpendicular planes. The Oroy body curved blade has a streamlined airfoil profile with a blunt leading edge and a sharp trailing edge. The Oroy body curved blade has a continuously varying chord length and installation angle distribution along the impeller radial direction, and the projection profile of the Oroy body curved blade on the plane perpendicular to the impeller axis is a backward curved profile. The front air inlet and the rear air inlet are arranged coaxially and located on opposite sides of the impeller axis, so that the two air streams enter the impeller from opposite sides of the impeller axis, merge inside the impeller, and are discharged radially.

[0010] Preferably, the Orloyal body is composed of orthogonal circles C1 and C2, with the center of orthogonal circle C1 being O1 and the center of orthogonal circle C2 being O2. The radii of orthogonal circles C1 and C2 are both R0. The distance between the center O1 and the center O2 is equal to R0, and the center O1 is located on the circumference of orthogonal circle C2, while the center O2 is located on the circumference of orthogonal circle C1.

[0011] Preferably, the diameters of orthogonal circles C1 and C2 are both d, R0 = d / 2, and the height H0 of the Orloyal body is equal to d; in one coordinate representation, orthogonal circle C1 lies in the xz plane, with its center O1 at (0, 0, 0), and orthogonal circle C1 satisfies x 2 +z 2 =R0 2 y=0; Orthogonal circle C2 lies in the xy plane, with center O2 at (R0, 0, 0), and satisfies (x-R0). 2 +y 2 =R0 2 z=0.

[0012] Preferably, the Oroy body curved surface blade is formed as follows: a continuous truncation curve is determined on the continuous developable surface of the Oroy body, and the parent surface of the blade surface is obtained by truncation curve; N cross-section positions are set along the radial direction of the Oroy body curved surface blade, N≥5, and the parent surface is truncation at each cross-section position to obtain the corresponding cross-section contour line; rotation transformation, scaling transformation and translation transformation are performed on each cross-section contour line, wherein the rotation transformation is used to adjust the installation angle of the cross-section contour line at the corresponding radial position, the scaling transformation is used to adjust the chord length of the cross-section contour line at the corresponding radial position, and the translation transformation is used to position the cross-section contour line to the corresponding radial position of the impeller; the transformed cross-section contour lines are smoothly connected by surface fitting or lofting to form the suction surface and pressure surface of the Oroy body curved surface blade.

[0013] Preferably, the installation angle is the angle between the local chord line of the blade and the circumferential tangent at that location; for the Oroy body curved blade, the installation angle on the hub side is the inlet angle β1, β1 = 40°~60°, and the installation angle on the outer edge side of the impeller is the outlet angle β2, β2 = 20°~35°; wherein, the installation angle continuously varies along the impeller radial direction, specifically: let the radial coordinate of the blade be r, the radial coordinate of the hub side be r1, the radial coordinate of the outer edge side of the impeller be r2, and the normalized radial coordinate τ = (r-r1) / (r2-r1), then the installation angle β(τ) continuously varies according to the law of quadratic Bezier curve: β(τ) = (1-τ) 2 ·β1+2(1-τ)τ·β m +τ 2 ·β2; where β m β is the midpoint control angle. m = (β1+β2) / 2+Δβ, where Δβ is 5°~15°; or, the installation angle changes continuously according to the cubic spline interpolation function, so that the first and second derivatives of the installation angle are continuous.

[0014] Preferably, the chord length of the Oroy body curved blade gradually increases from the hub side to the outer edge of the impeller, with the hub side chord length c1 being 30mm to 50mm and the outer edge side chord length c2 being 50mm to 80mm; the leading edge radius ρ1 of the Oroy body curved blade is 1.5mm to 3.5mm, the trailing edge radius ρ2 is 0.2mm to 0.5mm, the maximum thickness is located at 25% to 35% of the chord length from the leading edge, and the ratio of the maximum thickness to the chord length is 5% to 10%.

[0015] Preferably, the projection of the mid-curve of the Oroy body surface blade onto a plane perpendicular to the impeller axis is a logarithmic spiral or a combination of circular arcs and straight lines; when the mid-curve is a logarithmic spiral, its polar coordinate equation is R. c (ψ) = R c0 ·exp(kψ), where R c(ψ) is the polar radius of the middle arc at the polar angle ψ, R c0 Let be the initial polar diameter of the mid-arc line, and k be the helical coefficient, where 0 < k < 1.

[0016] Preferably, there are six Oroy body curved blades, which are evenly arranged around the circumference of the hub; the diameters of the front air inlet and the rear air inlet are equal, and both are 55% to 65% of the impeller outer diameter D; the inner edges of the front air inlet and the rear air inlet are provided with guide rings, which are arc-shaped flange structures protruding towards the inside of the impeller.

[0017] Preferably, the volute is a logarithmic spiral volute or a volute with unequal side distances, and the cross-sectional area of ​​the volute duct gradually increases along the airflow direction; the ratio of the volute tongue clearance t to the impeller outer diameter D is t / D = 0.04~0.08, the volute tongue angle θ = 15°~35°, and the volute outlet diffuser angle α d =8°~15°.

[0018] Preferably, the centrifugal fan further includes an auxiliary noise reduction structure, which includes at least one of the following: the trailing edge of the Oroy body curved blades is provided with a serrated trailing edge structure or a wavy trailing edge structure; the pressure surface and / or suction surface of the Oroy body curved blades are provided with a microgroove drag reduction structure extending along the mainstream airflow direction; the inner wall of the volute is provided with a composite sound absorption structure, which includes, from the inner side of the volute's air duct to the outside, a micro-perforated plate layer, a honeycomb pore layer, and a fiber sound absorption layer.

[0019] The technical effects and advantages of this invention are as follows: Compared with the prior art, this invention uses the continuous developable surface of the Oroy body as the surface source of the Oroy body curved blade, and forms the suction surface and pressure surface of the blade through interception, spatial transformation, radial scaling and surface lofting, so that the blade surface has a continuous and smooth three-dimensional curvature change; since the Oroy body curved blade has a streamlined cross-sectional profile with a blunt leading edge and a sharp trailing edge, and has a continuously changing chord length distribution and installation angle distribution along the impeller radial direction, the airflow enters from the axial direction in the blade channel and gradually turns to radial discharge. Therefore, the blade surface guides the airflow more smoothly, which can reduce the sudden change of local adverse pressure gradient, reduce the possibility of boundary layer separation and wake vortex shedding in the suction surface and trailing edge region of the blade, and thus help to reduce aerodynamic losses and blade trailing edge noise.

[0020] This invention combines the Oroy curved blades with a front and rear air inlet to form a dual-inlet structure, allowing two axial air streams to enter from both sides of the impeller, converge inside the impeller, and then exit radially. This structure can improve the problems of airflow deviation, pre-vortex, and uneven flow that easily occur in single-side air inlet structures, and improve the stability of the impeller inlet flow field. At the same time, the backward curvature projection profile of the Oroy curved blades matches the gradually expanding spiral air duct of the volute, allowing the airflow discharged from the outer edge of the impeller to enter the volute more smoothly and gradually diffuse, thereby improving the volute's recovery effect on the dynamic pressure at the impeller outlet and reducing the interference noise between the impeller wake and the volute tongue.

[0021] Furthermore, the guide rings set on the inner edges of the front and rear air inlets can guide the airflow smoothly into the blade channel, reducing flow separation at the inlet edges; the serrated or wavy trailing edge structure set on the trailing edge of the Oroy curved blades can disperse the trailing edge wake vortex and reduce its coherence; the microgroove drag-reducing structure set on the pressure and / or suction surfaces of the blades can improve the flow state near the wall; and the composite sound-absorbing structure set on the inner wall of the volute can absorb noise propagating within the volute. These auxiliary structures, in conjunction with the Oroy curved blades, the front and rear dual air inlet structure, and the gradually expanding spiral volute, enable the fan to meet airflow and static pressure requirements while maintaining low operating noise.

[0022] In addition, the impeller can be integrally molded using fiber-reinforced thermoplastic materials, so that the hub and multiple Oroy curved surface blades form an integral structure. This is beneficial to improving the positional consistency between the blades and the hub and the dynamic balance stability of the impeller, while reducing the weight of the impeller and improving the feasibility of mass production of complex three-dimensional curved surface blades. Attached Figure Description

[0023] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0024] Figure 1 This is a front view of the centrifugal fan of the present invention; Figure 2 This is a three-dimensional exploded view of the centrifugal fan of the present invention; Figure 3 This is a schematic diagram of the structure of the present invention viewed from a perspective perpendicular to the axial direction of the centrifugal fan; Figure 4 This is a schematic diagram of the longitudinal section structure of the centrifugal fan of the present invention; Figure 5 This is a top view of the air outlet of the centrifugal fan of the present invention; Figure 6 This is a three-dimensional top view of the air outlet of the centrifugal fan of the present invention; Figure 7 This is a front view schematic diagram of the impeller structure of the present invention; Figure 8 This is a three-dimensional structural diagram of the impeller of the present invention; Figure 9This is a side view of the impeller structure of the present invention; Figure 10 This is a side view of the impeller structure in three-dimensional form according to the present invention; Figure 11 This is a top view of the impeller structure of the present invention; Figure 12 This is a schematic diagram of the planar structure of the Oloyd body of the present invention; Figure 13 This is a three-dimensional structural diagram of the Oloyd body of the present invention; Figure 14 This is a wireframe perspective view of the Oloyd body of the present invention; Figure 15 This is a top view of the Oloyd body structure of the present invention; Figure 16 This is a three-dimensional top view of the Oloyd body of the present invention; Figure 17 This is a schematic diagram of the blade mounting angle of the present invention; Figure 18 This is a schematic diagram of the parameters of the volute tongue of the present invention; Figure 19 This is a schematic diagram of the air outlet diffusion angle of the present invention; Figure 20 This is a schematic diagram of the inlet angle of the present invention; Figure 21 This is a schematic diagram of the exit angle of the present invention.

[0025] Legend: 1. Impeller; 2. Volute; 3. Front air inlet; 4. Air outlet; 5. Hub; 6. Rear air inlet; 7. Motor; 8. Oloy curved blade; 9. Oloy body. Detailed Implementation

[0026] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0027] In this embodiment, the impeller 1, volute 2, front air inlet 3, air outlet 4, hub 5, rear air inlet 6, motor 7, Oroy curved blade 8, and Oroy body 9 are the main structural components of the present invention.

[0028] Example 1: Overall structure and assembly relationship of the fan.

[0029] Please see Figures 1 to 6 This embodiment provides an overall structural implementation scheme for an Oloyd body curved blade dual-inlet low-noise centrifugal fan.

[0030] The centrifugal fan includes a volute 2, an impeller 1, a front air inlet 3, an air outlet 4, and a motor 7. The volute 2 forms a gradually expanding spiral air duct inside, and the impeller 1 is located inside the volute 2. The motor 7 is installed on one side of the rear of the fan, and its output shaft is coaxially connected to the hub 5 of the impeller 1 to drive the impeller 1 to rotate. The front air inlet 3 is located on the front of the fan and has an annular opening structure. The ambient airflow enters the impeller 1 along the axial direction through the front air inlet 3. The air outlet 4 is located in the tangential direction of the volute 2 and is used to guide the airflow collected inside the volute 2 to downstream pipes or smoke exhaust systems. The inner wall of the volute 2 has a gradually expanding spiral shape, which gradually expands from near the outer edge of the impeller along the direction of impeller rotation and extends to the air outlet 4.

[0031] Furthermore, the centrifugal fan adopts a front and rear dual air inlet structure. The front air inlet 3 and the rear air inlet 6 are coaxially arranged on both sides of the impeller 1. The impeller 1 is located in the central area inside the volute 2. The motor 7 is installed on the outside of the rear air inlet 6. The output shaft of the motor 7 passes through the central hole of the rear air inlet 6 and is connected to the hub 5. The inner edges of the front air inlet 3 and the rear air inlet 6 are provided with guide rings. The guide rings are arc-shaped flanged structures and protrude into the inside of the impeller 1. They are used to guide the airflow smoothly into the blade channel along the axial direction and avoid the airflow from separating and swirling due to sharp turning at the edge of the air inlet.

[0032] The airflow path of the front and rear dual-inlet structure is as follows: the ambient airflow flows in axially from the front inlet 3 and the rear inlet 6 at the same time, forming two intake jets; the two intake jets converge in the axial middle region of the impeller 1, and under the push and guidance of the Oroy curved blades 8, they gradually change from axial to radial; after the airflow is discharged at the outer edge of the impeller, it enters the gradually expanding spiral air duct of the volute 2, and is collected along the circumference of the volute 2, and finally discharged from the outlet 4; since the airflow enters from both sides of the impeller 1, it can reduce the airflow deflection and pre-vortex phenomenon commonly found in single-sided intake structures, and improve the uniformity of intake.

[0033] Viewed from above, the gradually expanding spiral air duct outline of the volute 2 is relatively clear. The cross-sectional area of ​​the air duct gradually increases along the airflow direction. The cross-section of the air duct is smaller near the volute tongue and gradually expands along the spiral direction to the air outlet 4. This gradually expanding structure is used to convert part of the dynamic pressure of the high-speed airflow discharged from the outer edge of the impeller 1 into static pressure, thereby improving the static pressure output capacity of the fan. The air outlet 4 can be set as a rectangle, a flat circle, or other cross-sectional form adapted to the downstream pipe interface, and its outlet section can form a diffuser section.

[0034] Example 2: Three-dimensional configuration of impeller structure and Oroy body curved blade.

[0035] Please see Figures 7 to 10 This embodiment details the structure of the impeller 1 and the three-dimensional configuration of the Oroy body curved blade 8.

[0036] The impeller 1 includes a hub 5 and six Oloy surface blades 8 evenly arranged around the hub 5. The hub 5 is located at the center of the impeller 1 and has a hollow cylindrical or disc-shaped structure. The outer circumferential surface of the hub 5 is connected to the root of each Oloy surface blade 8. The six Oloy surface blades 8 extend outward from the outer circumferential surface of the hub 5 to the outer edge of the impeller. The circumferential angle between two adjacent Oloy surface blades 8 is 60°. Each Oloy surface blade 8 has a continuously varying curvature in the axial, circumferential, and radial directions, and its shape is different from that of a simple flat blade or a single circular arc blade.

[0037] The Oroy body curved blade 8 has a streamlined airfoil profile with a blunt leading edge and a sharp trailing edge. The leading edge is the side of the blade facing the incoming flow, and the trailing edge is the side where the airflow leaves the blade. The leading edge radius ρ1 can be 1.5mm to 3.5mm, and is preferably 2.5mm in this embodiment. The trailing edge radius ρ2 can be 0.2mm to 0.5mm, and is preferably 0.3mm in this embodiment. The maximum thickness of the blade is located at 25% to 35% of the chord length from the leading edge, and is preferably located at 30% of the chord length in this embodiment. The ratio of the maximum thickness to the chord length is 5% to 10%, and is preferably 7% in this embodiment. By setting the above airfoil parameters, the airflow can adhere more smoothly to the blade surface at the leading edge and the trailing edge wake area of ​​the blade can be reduced.

[0038] The projected profile of the Oroy body curved blade 8 on the plane perpendicular to the impeller axis is backward curved, meaning that as the blade extends from the hub 5 side towards the outer edge of the impeller, its curvature is opposite to the rotation direction of the impeller 1. The arc of the blade can be a logarithmic spiral or a combination of circular arc and straight line curves. In this embodiment, the arc of the blade adopts a logarithmic spiral form, and its expression is R. c (ψ) = R c0 ·exp(kψ), where R c (ψ) represents the polar radius of the middle arc at the polar angle ψ, R c0 Let R be the initial polar radius, k be the helical coefficient, and 0 < k < 1; as a specific example, the middle arc can satisfy R c (ψ) = 84 × exp(0.12ψ), in mm, where ψ is the polar angle in radians; the use of backward bending projection profile can make the airflow deflection in the blade channel smoother and match the airflow direction at the outlet of impeller 1 with the gradually expanding spiral airflow channel of volute 2.

[0039] In this embodiment, the main geometric parameters of the impeller 1 are as follows: impeller outer diameter D = 280 mm; hub outer diameter D1 = 168 mm, the ratio of hub outer diameter to impeller outer diameter D1 / D = 0.6; impeller axial thickness H = 140 mm, that is, the blade spanwise length is 140 mm; the hub 5 is a hollow cylindrical structure with an inner diameter of Φ50 mm, used to install the motor shaft, and a wall thickness of 5 mm, with a keyway and positioning boss inside; the radial length of the six Oroy curved surface blades 8 is L = (D-D1) / 2 = 56 mm; the above specific values ​​are used to illustrate the structural dimensions of this embodiment. Under the condition of meeting the requirements of air volume, static pressure and structural strength, the proportion can be adjusted according to different models of fans.

[0040] Example 3: Oloyd geometry and blade surface formation method.

[0041] Please see Figures 11 to 16 This embodiment illustrates the geometric structure of the Oloyd body 9, and the specific method for generating the Oloyd body surface blade 8 from the surface of the Oloyd body 9.

[0042] The Oloyd body 9 is composed of two orthogonal circles C1 and C2 with equal radii and perpendicular planes. The center of orthogonal circle C1 is O1, and the center of orthogonal circle C2 is O2. The diameters of orthogonal circles C1 and C2 are both d, and the radii are both R0 = d / 2. The distance between the centers O1 and O2 is R0, and the center O1 is located on the circumference of orthogonal circle C2, while the center O2 is located on the circumference of orthogonal circle C1. The height H0 of the Oloyd body 9 is equal to the diameter d of the orthogonal circle.

[0043] In a coordinate representation that facilitates modeling, let the radius of the orthogonal circle R0 = 30 mm and the diameter of the orthogonal circle d = 60 mm; the orthogonal circle C1 lies in the xz plane, with its center O1 at (0, 0, 0), and its equation is x 2 +z 2 =R0 2 y=0; the orthogonal circle C2 lies in the xy plane, with center O2 at (R0, 0, 0), and its equation is (x-R0). 2 +y 2 =R0 2 z=0; From this, we can know that the plane containing the orthogonal circle C1 is perpendicular to the plane containing the orthogonal circle C2. The distance from the center O1 to the center O2 is R0, and O2 satisfies the equation of the orthogonal circle C1, while O1 satisfies the equation of the orthogonal circle C2. Therefore, the geometric constraint that the center of each orthogonal circle lies on the circumference of another orthogonal circle is satisfied.

[0044] Looking at the Orodic solid 9 from the front view, one can see the outlines of two orthogonal circles C1 and C2 and their mutual constraint relationship. The two orthogonal circles intersect and jointly define the spatial range of the Orodic solid 9, so that the Orodic solid 9 as a whole presents a three-dimensional geometric shape with a continuous curved surface transition. This structure is not an ellipsoid or a simple surface of revolution, but is formed by a continuous developable surface defined by two orthogonal circles.

[0045] Viewed from above, the Oloyd body 9 has a projected outline that resembles a lens or a rhombus. The surface of the Oloyd body 9 has no obvious edges, creases or abrupt changes in curvature. Its surface can be unfolded into a plane in one direction, exhibiting the geometric characteristics of a continuously developable surface. This surface feature makes it suitable as a matrix for blade surfaces, used to form three-dimensional blades with continuously varying surface curvature.

[0046] Viewing the Oroj 9 from the side, one can see the contour changes in its height direction; the total height H0 of the Oroj 9 is equal to the diameter d of the orthogonal circle, and in this embodiment, H0=d=60mm; the Oroj 9 is relatively narrow in the middle region, forming a continuously changing bulging surface towards both ends, and then shrinking towards the extreme point; this width variation law and the continuous developable surface feature together constitute the geometric basis of the Oroj 9.

[0047] The process of generating the Olloy surface blade 8 from the Olloy body 9 includes the following steps.

[0048] Step S1: Construct the basic Orodic geometry model. Using CAD software or parametric modeling software, construct a three-dimensional solid model or surface model of the Orodic body 9 based on the radius R0 and diameter d of the orthogonal circles C1 and C2, as well as the positional relationship between the centers O1 and O2. The diameter d of the orthogonal circle can be adjusted within the range of 40mm to 80mm. In this embodiment, d=60mm, R0=30mm, and H0=d=60mm are used. The modeling method can be parametric surface modeling, sweep modeling, or envelope surface modeling.

[0049] Step S2: Determine the interception path. Define a path on the surface of the Oroj 9 starting from the top pole P. top Extending to the bottom pole P bottom A continuous smooth curve is used as the cut curve; the cut curve may be located in a plane passing through the axis of symmetry of the Oroy body 9, or in a plane forming a predetermined angle with the plane; the cut curve divides the continuous developable surface of the Oroy body 9 into at least two surface regions, and selects the surface region containing the bulging region and suitable for forming the suction surface or pressure surface of the blade as the parent surface of the blade surface; the cut curve must at least satisfy first-order continuity to ensure that the blade surface generated subsequently does not have obvious creases.

[0050] Step S3: Cut the blade radially in layers. Along the radial direction of the Oroy body curved surface blade 8, i.e., from the hub 5 side to the outer edge of the impeller, set N cross-section positions, N≥5, preferably 7~11. Let the radial coordinate of the i-th cross-section position be r. i , i=1,2,…,N; at each cross-section position r i At the location, the parent surface obtained in step S2 is intercepted by a cross-sectional plane parallel to the impeller axis, resulting in the corresponding i-th cross-sectional profile line; each cross-sectional profile line reflects the local curvature characteristics of the continuous developable surface of the Oroy body 9 at the corresponding radial position.

[0051] Step S4: Spatial transformation of the cross-sectional profile. Apply rotation transformation, scaling transformation and translation transformation to each cross-sectional profile line. Rotation transformation is to rotate the cross-sectional profile line around its own normal or a specified axis by a corresponding angle so that it meets the target installation angle at the radial position. Scaling transformation is to scale the cross-sectional profile line proportionally according to the target chord length at the radial position so that the chord length gradually changes along the radial direction. Translation transformation is to position the transformed cross-sectional profile line to the corresponding radial position in impeller 1. Through the above transformations, the leading edge of the blade faces the incoming flow direction of the impeller rotation direction, and the trailing edge faces the exhaust direction of the outer edge of the impeller, and a continuous transition is formed between each cross-section.

[0052] Step S5: Generate the blade surface. Use NURBS surface fitting or Loft lofting to smoothly connect the transformed cross-sectional contours to form the suction and pressure surfaces of the Oroy body surface blade 8. The suction and pressure surfaces can be formed from different Oroy body surface patches, or from the same parent surface through thickness offset, surface trimming, and edge connection. The generated Oroy body surface blade 8 has continuously varying three-dimensional curvature in both the spanwise and radial directions, and undergoes smooth transition processing at the leading edge, trailing edge, and blade root.

[0053] The Oloy body curved surface blade 8 formed by the above steps is not a direct application of the complete Oloy body 9 shape. Instead, it uses the continuous developable surface of the Oloy body 9 as the surface source, and forms a blade configuration that is adapted to the centrifugal impeller airflow channel after being cut, rotated, scaled, translated and lofted.

[0054] Example 4: Chord length distribution and installation angle distribution.

[0055] The Oroy body curved blade 8 has a continuously varying chord length distribution along the radial direction. Let the radial coordinate of the blade be r, the radial coordinate of the hub side be r1, and the radial coordinate of the impeller outer edge side be r2. The chord length of the blade on the hub side is c1, and the chord length on the impeller outer edge side is c2. c1 can be 30mm to 50mm, and c2 can be 50mm to 80mm, and c2 is greater than c1. The chord length can gradually increase from the hub side to the impeller outer edge side, and can be continuously varied according to a linear function, a quadratic function, or a cubic spline interpolation function to adapt to the gradually changing flow area of ​​the blade channel along the radial direction.

[0056] like Figure 17 , Figure 20 and Figure 21 As shown, the Oroy body curved blade 8 also has a continuously varying installation angle distribution along the radial direction; the installation angle is the angle between the local cross-section chord line of the blade and the circumferential tangent at that point, and the measurement reference is the circumferential tangent direction; the installation angle at the blade root near the hub 5 is the inlet angle β1, which can be 40° to 60°; the installation angle at the blade tip near the outer edge of the impeller is the outlet angle β2, which can be 20° to 35°; in this embodiment, the inlet angle β1 can be 41.8° and the outlet angle β2 can be 30° to match the airflow direction at the blade inlet and outlet.

[0057] To make the installation angle change smoothly along the impeller radial direction, the normalized radial coordinate τ can be set as τ = (r - r1) / (r2 - r1), where r is the radial coordinate of the blade, r1 is the radial coordinate of the hub side, and r2 is the radial coordinate of the outer edge of the impeller. The installation angle β(τ) can change continuously according to the law of quadratic Bézier curve, and its expression is: β(τ) = (1 - τ). 2 ·β1+2(1-τ)τ·β m +τ 2 ·β2; where β m β is the midpoint control angle. m = (β1 + β2) / 2 + Δβ, where Δβ is taken as 5° to 15°; in one specific embodiment, r1 = 84mm, r2 = 140mm, β1 = 48°, β2 = 28°, β m =40°, then the installation angle can be expressed as β(τ) = (1-τ) 2 ×48°+2(1-τ)τ×40°+τ 2 ×28°; by adjusting β m It can control the rate of change of the installation angle in the middle region of the blade, and avoid abrupt changes in the blade installation angle in the radial direction.

[0058] The installation angle can also be continuously varied according to the cubic spline interpolation function, so that the first and second derivatives of the installation angle are continuous between r1 and r2. The continuous variation of the installation angle and the chord length together limit the variation law of the radial parameters of the Oroy body curved blade 8, making the deflection and diffusion process of the airflow in the blade channel smoother, thereby reducing the risk of boundary layer separation caused by excessive local reverse pressure gradient.

[0059] Example 5: Air inlet, volute and motor system.

[0060] Please see Figures 1 to 6 , Figures 18-19 This embodiment further explains the structure and parameters of the front air inlet 3, the rear air inlet 6, the volute 2, and the motor 7.

[0061] The front air inlet 3 and the rear air inlet 6 have the same diameter and are both arranged coaxially with the impeller 1. In one specific embodiment, the diameter of the front air inlet 3 and the rear air inlet 6 is Φ165mm, the outer diameter of the impeller D is 280mm, and the diameter of the air inlet is about 59% of the outer diameter of the impeller D, which is within the range of 55% to 65% of the outer diameter of the impeller D.

[0062] Both the front air inlet 3 and the rear air inlet 6 are provided with guide rings on their inner edges; the guide rings are arc-shaped flanged structures with a flange radius of 5mm to 20mm, preferably 12mm; the flange height or axial depth can be 10mm; the guide rings protrude into the impeller 1 to smoothly guide the airflow entering from the outside in an approximately axial direction to the blade channel inlet, so as to avoid the airflow from separating and forming vortices at the sharp edge of the air inlet.

[0063] The volute 2 can be a logarithmic spiral volute or a volute with unequal side distances; when using a logarithmic spiral volute, its profile equation can be expressed as r v (φ) = r o ×exp(φ×tanα;where, r v (φ) is the extreme diameter of the volute profile at the wrap angle φ, r o α is the impeller outer radius, φ is the helix angle, and φ is the wrap angle measured from the volute tongue; in this embodiment, the impeller outer diameter D = 280 mm, and the impeller outer radius r o =140mm, the helix angle α can be 12°; the cross-sectional area of ​​the air duct of the volute 2 gradually increases along the airflow direction, thereby collecting and diffuses the high-speed airflow discharged from the impeller 1.

[0064] The volute tongue clearance t is the shortest distance from the tip of the volute tongue to the outer edge of the impeller; the ratio of the volute tongue clearance t to the outer diameter D of the impeller, t / D, can be 0.04 to 0.08; in this embodiment, the volute tongue clearance t is 15 mm, t / D = 15 / 280 ≈ 0.054; the volute tongue angle θ is the angle between the tangent line on the inner wall at the tip of the volute tongue and the radial line connecting the center of the volute and the center of the impeller, θ can be 15° to 35°, and in this embodiment, θ can be 25°; the volute outlet diffuser angle α d α is the semi-expansion angle of the gradually expanding air duct at the outlet section. d It can be 8° to 15°, and in this embodiment, α d 12° is acceptable.

[0065] The axial width of the air duct in the volute 2 can gradually increase along the airflow direction; in one specific embodiment, the axial width b0 of the air duct at the volute tongue, i.e., φ=0°, is equal to the axial thickness H of the impeller, b0=140mm; at the air outlet 4, the axial width b0 of the air duct is... exit The diameter is increased to 240mm, with an expansion ratio of approximately 1.71. By gradually increasing the cross-sectional area of ​​the air duct, the airflow pressure discharged from the outer edge of the impeller 1 can be gradually converted into static pressure within the volute 2, thereby improving the diffusion effect of the volute 2.

[0066] The motor 7 can be a permanent magnet DC inverter motor. In one specific implementation, the rated power of the motor 7 is 500W to 800W, preferably 650W; the rated speed range is 800r / min to 2800r / min, and can be continuously adjusted by a PWM inverter driver. The output shaft of the motor 7 passes through the rear air inlet 6 and is connected to the hub 5, so that the impeller 1 rotates synchronously with the motor 7.

[0067] The stator of motor 7 can be integrally cast in aluminum with the support base to reduce weight and improve support rigidity; the support base can be fixedly connected to the outer edge of the rear air inlet 6 by six radially evenly arranged support ribs, with an included angle of 60° between adjacent support ribs; the cross section of the support ribs can adopt a streamlined airfoil section, such as the simplified cross section of the NACA0012 symmetrical airfoil; the thickness of the support ribs can be 5mm and the chord length can be 40mm to reduce the obstruction and disturbance of the airflow of the rear air inlet 6 by the support ribs.

[0068] Example 6: Tail edge structure, microgroove and composite sound absorption structure.

[0069] To further reduce the operating noise of the wind turbine, the trailing edge of the Oroy body curved blade (8) can be provided with a sawtooth trailing edge structure or a wave trailing edge structure; the sawtooth trailing edge structure is set along the blade span near the outer edge of the impeller, the sawtooth tooth height can be 2mm to 8mm, preferably 4mm; the tooth pitch can be 5mm to 15mm, preferably 10mm; the wave amplitude of the wave trailing edge structure can be 1.5mm to 5mm, preferably 3mm; the wavelength can be 8mm to 20mm, preferably 12mm; the sawtooth trailing edge structure or the wave trailing edge structure can disperse the relatively concentrated wake vortex at the trailing edge into multiple smaller-scale sub-vortices with different phases, thereby reducing the coherence of the wake vortex and the interference to the volute tongue.

[0070] The pressure and / or suction surfaces of the Oroy body curved blade 8 can be equipped with microgrooves to reduce drag. The microgrooves are arranged along the mainstream airflow direction, with the groove direction parallel to the local mainstream direction. The microgroove depth can be 20 μm to 100 μm, preferably 50 μm; the groove width can be 50 μm to 200 μm, preferably 120 μm; the groove spacing can be 100 μm to 500 μm, preferably 250 μm. The microgrooves can be formed by laser micromachining, micro-injection molding, or micro-texture transfer onto the mold surface. The microgroove structure is used to restrict the lateral movement of the near-wall turbulent structure, reducing blade surface friction drag and near-wall flow disturbance.

[0071] The inner wall of the volute 2 can be covered with a composite sound-absorbing structure consisting of a micro-perforated plate, a honeycomb pore layer, and a fiber sound-absorbing layer. The composite sound-absorbing structure, from the inside of the air duct outwards, includes a micro-perforated plate layer, a honeycomb pore layer, and a fiber sound-absorbing layer. The thickness of the micro-perforated plate layer can be 0.5mm to 2mm, preferably 1.0mm; the pore diameter can be Φ0.3mm to Φ1mm, preferably Φ0.5mm; the perforation rate can be 0.5% to 5%, preferably 3%, and the perforations can be arranged in an equilateral triangle. The honeycomb pore layer can adopt a hexagonal honeycomb structure, with a single pore diameter of 3mm. The thickness can be 10 mm, preferably 6 mm; the wall thickness can be 0.1 mm to 0.5 mm, preferably 0.2 mm; the depth can be 10 mm to 30 mm, preferably 20 mm; the fiber sound-absorbing layer can be made of nanofiber felt, the fiber diameter can be 50 nm to 500 nm, preferably 150 nm; the porosity can be 85% to 95%, preferably 92%; the thickness can be 5 mm to 15 mm, preferably 8 mm; the composite sound-absorbing structure absorbs the noise propagating inside the volute 2 through multi-layer cavities and multi-scale fiber pores.

[0072] Example 7: Material selection and manufacturing process.

[0073] Impeller 1 can be integrally molded from fiber-reinforced thermoplastic material. As a specific embodiment, impeller 1 uses PA6 and GF30 materials, namely glass fiber reinforced polyamide 6 with a glass fiber content of 30wt%. The density of this material is about 1.35g / cm³, the tensile strength can be 120MPa, the flexural modulus can be 5.5GPa, and the heat distortion temperature can meet the requirements of the operating environment of the range hood fan. Compared with metal impellers, the use of this material can reduce the mass of impeller 1 and has better injection molding fluidity, which is suitable for forming the complex three-dimensional curved surface of the Oroy body curved blade 8.

[0074] In addition to PA6 and GF30, glass fiber reinforced polybutylene terephthalate (PBT) and GF30, glass fiber reinforced polypropylene (PP) and GF30, or carbon fiber reinforced polyphenylene sulfide (PPS) and CF20 can also be selected according to specific working conditions.

[0075] The impeller 1's hub 5 and six Oloyed surface blades 8 can be integrally injection molded to ensure the positional accuracy and dynamic balance between the hub 5 and each blade. The injection mold cavity can be machined using five-axis linkage CNC and mirror polished to ensure that the surface roughness Ra of the cavity is ≤0.4μm, thereby ensuring the molding accuracy and surface smoothness of the Oloyed surface blades 8. For blades with microgroove structures, reverse microtextures can be pre-formed on the surface of the mold cavity so that the microgrooves are synchronously transferred to the blade surface during the injection molding process.

[0076] The volute 2 can be manufactured by injection molding of reinforced plastic, metal sheet molding, or composite material molding. As a specific embodiment, the volute 2 can be injection molded using glass fiber reinforced polypropylene (PP) and GF20. This material has good toughness, chemical corrosion resistance, and molding economy. The gradually expanding spiral air duct, volute tongue, air outlet 4, front air inlet 3, and rear air inlet 6 of the volute 2 can be assembled after separate molding, or integral molding or half-shell combination molding can be adopted according to manufacturing conditions. When the inner wall of the volute 2 is provided with a composite sound-absorbing structure, the micro-perforated plate layer, honeycomb hole layer, and fiber sound-absorbing layer can be fixed to the inner wall of the volute 2 by bonding, snap-fit ​​fixing, pressing, secondary injection molding, or insert injection molding.

[0077] Example 8: When designing this fan, the target air volume Q and target static pressure p can be used as a reference. s Determine the impeller outer diameter D, hub outer diameter D1, and rated speed n0; as a design objective, the target air volume Q can be 30m³ / h. 3 / min~35m 3 / min, target static pressure p s The range is 2500Pa to 2800Pa; the initial parameters can be obtained through similarity laws and Euler equations, and then iteratively optimized based on the geometric parameters of the Olois surface blade 8.

[0078] Design variables may include the orthogonal circle diameter d, the Orojoid body height H0, the chord length distribution, the installation angle distribution, the inlet angle β1, the outlet angle β2, and the midpoint control angle β. m The parameters of the blade's mid-curve, the volute tongue clearance t, the volute tongue angle θ, and the volute outlet diffusion angle α. d The three-dimensional computational domain of the wind turbine can be established using computational fluid dynamics methods, and three-dimensional aerodynamic calculations can be performed on the impeller 1, volute 2 and dual air inlet channels based on the Reynolds-averaged Navier-Stokes equations and the k-ω SST turbulence model.

[0079] During calculation, a rotating domain can be set for the impeller 1 region, and a stationary domain can be set for the volute 2 and the inlet and outlet regions. Data transfer between the dynamic and static domains is completed through the interface. Pressure inlets or mass flow inlets can be set at the front inlet 3 and the rear inlet 6, and a pressure outlet can be set at the outlet 4. No-slip boundary conditions can be set for the walls of the impeller 1 and the volute 2. Local mesh refinement can be performed on the blade surface and the volute tongue region to improve the accuracy of boundary layer separation and wake vortex calculation.

[0080] During the optimization process, total pressure efficiency, air volume, static pressure and noise power level can be used as evaluation indicators, and orthogonal circle diameter, chord length distribution, installation angle distribution and mid-arc parameters can be used as the main design variables. Multi-objective genetic algorithm or particle swarm optimization algorithm can be used for optimization. The optimized blades can also be subjected to modal analysis and fluid-structure interaction verification to ensure that the first natural frequency of the blades avoids the excitation frequency of motor 7 and its harmonics, thereby reducing the risk of resonance.

[0081] Based on simulation results, a comparative analysis can be conducted between the Oloy body curved surface blade 8 and the ordinary circular arc blade. Under the same impeller outer diameter, the same rotational speed, and the same volute, the Oloy body curved surface blade 8 exhibits better surface curvature continuity, a smaller local separation zone on the suction surface, and a lower peak vortex in the wake region. With the front and rear dual inlet structure combined with guide rings, the total pressure recovery capability at the inlet is improved, and the inlet vortex is weakened. The above simulation results can be used to correct the blade surface curvature, installation angle, chord length distribution, and volute parameters. The final performance is subject to prototype testing results.

[0082] Example 9: Working process.

[0083] When the invention is in operation, the motor 7 drives the impeller 1 to rotate. The ambient airflow enters the inner side of the volute 2 through the front air inlet 3 and the rear air inlet 6 respectively. The airflow smoothly enters the blade channel through the guide ring. The air intakes on both sides converge in the middle of the impeller 1 in the axial direction and gradually change from axial to radial under the drive of the Oroy curved surface blade 8. Since the suction surface and pressure surface of the Oroy curved surface blade 8 are formed by cutting a continuous developable surface and transforming it in space, and the blade chord length and installation angle change continuously in the radial direction, the curvature change of the airflow along the blade surface is relatively smooth, and the local flow separation and wake vortex shedding are weakened.

[0084] The airflow discharged from the outer edge of impeller 1 enters the gradually expanding spiral duct of volute 2, is gathered and gradually diffused along the circumference of volute 2, and finally discharged through outlet 4; volute tongue gap t, volute tongue angle θ, and volute outlet diffusion angle α d Matching the outer diameter D of impeller 1 and the blade outlet flow direction can reduce the interference between the impeller wake and the volute tongue; the trailing edge sawtooth or wave-shaped structure is used to weaken the trailing edge wake vortex, the microgroove drag reduction structure is used to reduce the frictional resistance on the blade surface, and the composite sound absorption structure is used to absorb the aerodynamic noise propagating inside the volute 2.

[0085] Example 10: Integrated application of range hood.

[0086] The Oloyd body curved blade dual-inlet low-noise centrifugal fan of the present invention can be applied to range hoods. When applied to a range hood, the centrifugal fan is installed in the static pressure box of the range hood. The inlet of the static pressure box is connected to the smoke collection hood, and the outlet of the static pressure box is connected to the exhaust pipe. Both the front air inlet 3 and the rear air inlet 6 can be connected to the inner cavity of the static pressure box to improve the uniformity of airflow entering the impeller 1 in the static pressure box by utilizing the dual-inlet structure.

[0087] The range hood can also be equipped with an oil fume sensor system and a control system. The oil fume sensor system is used to detect changes in oil fume concentration during cooking. The control system adjusts the speed of motor 7 according to the oil fume concentration, duct static pressure, or user-set speed, so that the fan speed is reduced to reduce noise under low oil fume conditions, and the speed is increased to ensure smoke extraction capacity under high oil fume conditions. The inner wall of the static pressure box can also be lined with the aforementioned composite sound-absorbing structure to attenuate the radiation of fan noise into the kitchen space.

[0088] Because the impeller 1 adopts the Oroy body curved blade 8, and is combined with the front and rear double air intake structure, the gradually expanding spiral volute 2, the guide ring and the auxiliary noise reduction structure, the range hood can reduce the operating noise of the fan while meeting the air volume and static pressure requirements. It is suitable for kitchen ventilation equipment that requires low noise and high static pressure smoke exhaust capacity.

[0089] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A low-noise centrifugal fan with Oloyd body curved blades and dual air inlets, characterized in that, The system includes a volute (2), an impeller (1), a motor (7), a front air inlet (3), a rear air inlet (6), and an air outlet (4). The volute (2) forms a gradually expanding spiral air duct inside, and the impeller (1) is located inside the gradually expanding spiral air duct. The volute (2) is used to collect the airflow radially discharged from the impeller (1) and guide it to the air outlet (4). The impeller (1) includes a hub (5) and multiple Oroy curved surface blades (8) arranged circumferentially along the hub (5). The hub (5) is coaxially connected to the output shaft of the motor (7), and the Oroy curved surface blades (8) extend from the hub (5) to the outer edge of the impeller. The suction surface and pressure surface of the Oroy curved surface blades (8) are both formed by the continuous developable surface of the Oroy body (9) through a cross section. Taking the continuous three-dimensional curved surface features formed after spatial transformation, the Oroy body (9) is composed of two orthogonal circles with equal radii and perpendicular planes; the cross section of the Oroy body curved blade (8) is a streamlined airfoil profile with a blunt leading edge and a sharp trailing edge; the Oroy body curved blade (8) has a continuously varying chord length distribution and installation angle distribution along the impeller radial direction; and the projection profile of the Oroy body curved blade (8) on the plane perpendicular to the impeller axis is a backward curved profile; the front air inlet (3) and the rear air inlet (6) are arranged coaxially and are located on the axial sides of the impeller (1), so that the two air streams enter the impeller (1) from the axial sides of the impeller (1) and then merge and discharge radially inside the impeller (1).

2. The low-noise centrifugal fan with double air inlet and curved blades according to claim 1, characterized in that: The Oroy body (9) is composed of orthogonal circles C1 and C2. The center of orthogonal circle C1 is O1, and the center of orthogonal circle C2 is O2. The radii of orthogonal circles C1 and C2 are both R0. The distance between the center O1 and the center O2 is equal to R0. The center O1 is located on the circumference of orthogonal circle C2, and the center O2 is located on the circumference of orthogonal circle C1.

3. The low-noise centrifugal fan with double air inlet and curved blades according to claim 2, characterized in that: The diameters of the orthogonal circles C1 and C2 are both d, R0 = d / 2, and the height H0 of the Orojoid body (9) is equal to d; in one coordinate representation, the orthogonal circle C1 lies in the xz plane, with its center O1 at (0, 0, 0), and the orthogonal circle C1 satisfies x 2 +z 2 =R0 2 y=0; Orthogonal circle C2 lies in the xy plane, with center O2 at (R0, 0, 0), and satisfies (x-R0). 2 +y 2 =R0 2 z=0.

4. The low-noise centrifugal fan with double air inlet and curved blades according to any one of claims 1-3, characterized in that: The Oroy body curved blade (8) is formed in the following manner: a continuous cut curve is determined on the continuous developable surface of the Oroy body (9), and the parent surface of the blade surface is obtained by the continuous cut curve; N cross-section positions are set along the radial direction of the Oroy body curved blade (8), N≥5, and the parent surface is cut at each cross-section position to obtain the corresponding cross-section contour line; rotation transformation, scaling transformation and translation transformation are performed on each cross-section contour line respectively, wherein the rotation transformation is used to adjust the installation angle of the cross-section contour line at the corresponding radial position, the scaling transformation is used to adjust the chord length of the cross-section contour line at the corresponding radial position, and the translation transformation is used to position the cross-section contour line to the corresponding radial position of the impeller (1); the transformed cross-section contour lines are smoothly connected by surface fitting or lofting to form the suction surface and pressure surface of the Oroy body curved blade (8).

5. The low-noise centrifugal fan with double air inlet and curved blades according to claim 4, characterized in that: The installation angle is the angle between the local chord line of the blade and the circumferential tangent at that point; the installation angle of the Oroy curved blade (8) on the hub side is the inlet angle β1, β1 = 40°~60°, and the installation angle on the outer edge side of the impeller is the outlet angle β2, β2 = 20°~35°; wherein, the installation angle changes continuously along the impeller radial direction, specifically: let the radial coordinate of the blade be r, the radial coordinate of the hub side be r1, the radial coordinate of the outer edge side of the impeller be r2, and the normalized radial coordinate τ = (r-r1) / (r2-r1), then the installation angle β(τ) changes continuously according to the law of the quadratic Bezier curve: β(τ) = (1-τ) 2 ·β1+2(1-τ)τ·β m +τ 2 ·β2; where β m β is the midpoint control angle. m = (β1+β2) / 2+Δβ, where Δβ is 5°~15°; or, the installation angle changes continuously according to the cubic spline interpolation function, so that the first and second derivatives of the installation angle are continuous.

6. The low-noise centrifugal fan with double air inlet and curved blades according to claim 5, characterized in that: The chord length of the Oroy body curved blade (8) gradually increases from the hub side to the outer edge of the impeller. The chord length c1 on the hub side is 30mm to 50mm, and the chord length c2 on the outer edge of the impeller is 50mm to 80mm. The leading edge radius ρ1 of the Oroy body curved blade (8) is 1.5mm to 3.5mm, the trailing edge radius ρ2 is 0.2mm to 0.5mm, and the maximum thickness is located at 25% to 35% of the chord length from the leading edge. The ratio of the maximum thickness to the chord length is 5% to 10%.

7. The low-noise centrifugal fan with double air inlet and curved blades according to claim 6, characterized in that: The projection of the mid-arc line of the Oroy body curved blade (8) onto a plane perpendicular to the impeller axis is a logarithmic spiral or a combination of circular arc and straight line curve; when the mid-arc line adopts a logarithmic spiral, its polar coordinate equation is R. c (ψ) = R c0 ·exp(kψ), where R c (ψ) is the polar radius of the middle arc at the polar angle ψ, R c0 Let be the initial polar diameter of the mid-arc line, and k be the helical coefficient, where 0 < k < 1.

8. The low-noise centrifugal fan with double air inlet and curved blades according to any one of claims 1-7, characterized in that: The number of Oroy body curved blades (8) is six, and the six Oroy body curved blades (8) are evenly arranged along the circumference of the hub (5); the diameters of the front air inlet (3) and the rear air inlet (6) are equal, and both are 55% to 65% of the outer diameter D of the impeller; the inner edges of the front air inlet (3) and the rear air inlet (6) are provided with guide rings, and the guide rings are arc-shaped flange structures protruding towards the inside of the impeller (1).

9. The low-noise centrifugal fan with double air inlet and curved blades according to claim 8, characterized in that: The volute (2) is a logarithmic spiral volute or an unequal-width volute, and the cross-sectional area of ​​the volute (2) gradually increases along the airflow direction; the ratio of the volute tongue clearance t to the impeller outer diameter D is t / D = 0.04~0.08, the volute tongue angle θ = 15°~35°, and the volute outlet diffuser angle α d =8°~15°.

10. The low-noise centrifugal fan with double air inlet and curved blades according to claim 9, characterized in that: The centrifugal fan also includes an auxiliary noise reduction structure, which includes at least one of the following: the trailing edge of the Oroy body curved blade (8) is provided with a serrated trailing edge structure or a wavy trailing edge structure; The pressure surface and / or suction surface of the Oroy body curved blade (8) are provided with a microgroove drag reduction structure extending along the mainstream airflow direction; the inner wall of the volute (2) is provided with a composite sound absorption structure, which includes a micro-perforated plate layer, a honeycomb pore layer and a fiber sound absorption layer from the inside of the air duct of the volute (2) outward.

Images