Air inlet ring provided with fixed guide vanes and used for prewhirling air inlet, centrifugal fan and range hood

Abstract

An air inlet ring provided with fixed guide vanes and used for prewhirl air inlet comprises a flow guide cone, the guide vanes and an installation ring which are sequentially connected outwards in the radial direction, the guide vanes are evenly arranged at intervals in the circumferential direction, the flow guide cone and the installation ring are arranged at intervals in the axial direction, and the guide vanes continuously extend from the flow guide cone to the installation ring along a concave curve. Compared with the prior art, the technical scheme provided by the invention has the following advantages that wind breaking dispersion is carried out on incoming flow, the incoming flow prewhirl effect is more remarkable, flow separation of the suction surface of the impeller can be prevented, fan surge can be prevented, the pneumatic structure is more reasonable, and the noise reduction effect is more excellent.

Description

Technical Field

[0001] The invention relates to the field of air inlet rings for centrifugal fans, and in particular to an air inlet ring for pre-swirl air inlet with fixed guide vanes, a centrifugal fan and a range hood. Background Art

[0002] In today's kitchen appliance market, the performance of range hoods is facing unprecedented challenges. With the reduction of living space and the increase of building density, the effective emission of oil smoke and the control of noise of range hoods have become the focus of users when purchasing range hoods. In the prior art, range hoods use forward multi-blade centrifugal fan systems for smoke exhaust. Generally, the structure that provides air intake guides for centrifugal fans also mostly adopts traditional designs, that is, a circular guide structure formed by rotating an arc or a smooth curve to improve the air intake flow state entering the centrifugal fan impeller, thereby improving the smoke exhaust effect and reducing the smoke exhaust noise. For example, a Chinese invention application with application publication number CN114017392A and titled "Guide Inlet Ring and Centrifugal Fan" discloses: a guide inlet ring for a centrifugal fan, the guide inlet ring is formed with a plurality of guide structures to guide the airflow from the outside of the guide inlet ring to the air inlet of the centrifugal fan on the inside of the guide inlet ring; the plurality of guide structures are rotationally symmetrical about the center of the guide inlet ring, the guide structures form an arc-shaped guide path to deflect the airflow, so that the airflow passing through the plurality of guide paths moves in a preset motion direction, and the preset motion direction has a tangential motion component consistent with the rotation direction of the impeller of the centrifugal fan. The guide structure forms an arc-shaped guide path to deflect the airflow to generate a tangential motion in the same direction as the impeller linear velocity. Under the joint action of the fan inlet traction force, an inlet airflow rotating toward the inside of the fan is generated. This method of pre-rotating the airflow improves the uniformity of the airflow at the air inlet, increases the flow area of ​​the air inlet, and makes it easier for the airflow to enter the impeller; the airflow has a certain tangential velocity, so that when the airflow enters the blade flow channel, it has a movement trend close to the impeller rotation direction, and has a smaller tangential velocity difference relative to the blade, thereby weakening the blade flow channel airflow separation, optimizing the flow of the flow channel airflow, and solving the problems of uneven airflow at the fan inlet causing poor smoking effect and significant vortex impact noise.

[0003] However, due to the asymmetry of the flow channel inside the volute of the centrifugal fan, when the impeller of the centrifugal fan rotates, the pressure distribution of the air inlet circle in the radial direction is uneven. The traditional air inlet circle structure cannot meet the requirements of pre-swirl and rectification of the incoming flow before entering the impeller. When the airflow enters the centrifugal fan, it will produce a large impact loss and a large aerodynamic noise. In response to such problems, many experts and engineers have made certain improvement plans. The common improvement plan is to add annular or radial structures, honeycomb structures, grid structures, etc. to the existing air inlet circle, so as to improve the airflow direction, make the impeller intake pressure more uniform, and improve aerodynamic noise. For example, the Chinese utility model patent with the authorization announcement number CN218882569U, entitled "air inlet grille and fan assembly having the same", discloses: an air inlet grille, comprising: a mounting frame (1); a guide plate (2), located on one side of the mounting frame (1); a radial blade group (3), connected between the mounting frame (1) and the guide plate (2); a circumferential blade (4), connected to the radial blade group (3); wherein; through the cooperation of the radial blade group (3) and the circumferential blade (4); the direction of the airflow is guided. The technical solution described in the invention application makes the inlet airflow consistent with the rotation direction of the impeller through the radial blade group and the circumferential blades, avoids the increase of the blade inlet impact loss when there is no pre-rotation, causes the impeller suction surface to produce flow separation and block the blade path, achieves the purpose of noise reduction and anti-surge, and improves the performance of the fan. For another example, a Chinese invention application with application publication number CN116857230A, entitled A collector and a range hood, discloses: A collector, installed at the air inlet of a fan of the range hood, the collector comprising: a collector body (21); a plurality of pre-rotation guide vanes (22), arranged on the inner side of the collector body (21), the first ends of the pre-rotation guide vanes (22) being connected to the collector body (21), and two adjacent pre-rotation guide vanes (22) being arranged at intervals; an air-uniforming net (23), arranged on the inner side of the pre-rotation guide vanes (21) and connected to the second ends of the pre-rotation guide vanes (22); the impeller (3) of the fan and the collector satisfying the relationship: D b -D a1 ≥2W; among which, D b is the inner diameter of the fan impeller (3), D a1 is the inner diameter of the pre-swirl guide vane (22), and W is the minimum radial clearance requirement between the collector and the impeller (3). The pre-swirl guide vane (22) is twisted along the axial direction to form a first twisted top and a second twisted top. The protruding directions of the first twisted top and the second twisted top are the same as the rotation direction of the impeller (3). The first twisted top is the air inlet, and the second twisted top is the air outlet. The tangent of the first twisted top and the air inlet diameter D of the collector body (21) are a The angle between the tangent of the circle is F2, and the angle between the tangent of the second twist tip and the inner diameter D of the pre-rotation guide vane is a1The angle between the tangent lines of the circle is F1, F1, F2∈[0°-90°], F1∈[0-α+25°], F1≤F2; wherein α is the air inlet placement angle of the blade (31).

[0004] However, from the perspective of actual application effects, most of the above-mentioned improvement schemes only play a safety protection and limited rectification role, and the effect of improving noise is not obvious (even the setting of circumferential blades in some schemes affects the radial component of the airflow, and the airflow movement has no continuity, resulting in flow separation on the impeller suction surface). In particular, they are unable to break and disperse the incoming flow, and the pre-rotation performance of the incoming flow has not yet approached the high threshold. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an air inlet ring, a centrifugal fan and a range hood with fixed guide vanes for pre-swirling air, which can break and disperse the incoming flow, have a more significant effect of pre-swirling the incoming flow, thereby preventing the impeller suction surface from separating and preventing the fan from surging, have a more reasonable aerodynamic structure and a better noise reduction effect.

[0006] The present invention mainly adopts the following technical solutions:

[0007] An air inlet ring for pre-swirling air inlet with fixed guide vanes comprises a guide cone, a guide vane and a mounting ring which are sequentially connected radially outward, the guide vanes are evenly spaced along the circumferential direction, the guide cone and the mounting ring are spaced apart in the axial direction, and the guide vane extends continuously from the guide cone along a concave curve to the mounting ring.

[0008] The guide vane adopts a variable-section twisted blade, the trailing edge of the guide vane blade shape gradually bends radially outward and away from the leading edge of the guide vane blade shape, and the angle α between the chord line of the guide vane blade shape and the axial direction in the radial direction meets the following relationship: f(α)=a 1 *Di 3 +a 2 *Di 2 +a 3 *Di+a 4 , where 0.04≤a 1 ≤0.05, -0.5≤a 2 ≤-0.35,5.1≤a 3 ≤5.8, -0.2≤a 4≤0.5, where Di is the length measured from the center of the axis along the radial direction, which is the projection of the intersection point between the leading edge of the guide vane profile and the mean camber line of the guide vane profile onto the projection of the line connecting the intersection points between the leading edge of the guide vane profile and the mean camber line of the guide vane profile in the radial direction, and D1 / 2 < Di ≤ D3 / 2. D1 is the diameter of the flow guiding cone projected in the radial direction, and D3 is the diameter of the ring where the maximum length of the guide vane projected in the radial direction is located.

[0009] Among them, the guide vane is integrally in a tongue-shaped spoon shape.

[0010] Among them, when D1 / 2 < Di < Da / 2, the projection of the line connecting the intersection points between the leading edge of the guide vane profile and the mean camber line of the guide vane profile in the radial direction extends linearly, and the included angle θ between its deviation from the radial direction is ≤ 2°; when Da / 2 ≤ Di ≤ D3 / 2, the included angle θ between the projection of the line connecting the intersection points between the leading edge of the guide vane profile and the mean camber line of the guide vane profile in the radial direction and the radial direction conforms to the following relational expression: f(θ) = b 1 *Di 3 +b 2 *Di 2 +b 3 *Di + b 4 , where 0.06 ≤ b 1 ≤ 0.08, -0.7 ≤ b 2 ≤ -0.9, 3 ≤ b 3 ≤ 4.5, -3.5 ≤ b 4 ≤ -3, and 0.7 ≤ Da / D3 ≤ 0.9.

[0011] Among them, when Da / 2 ≤ Di ≤ D3 / 2, the included angle θ between the projection of the line connecting the intersection points between the leading edge of the guide vane profile and the mean camber line of the guide vane profile in the radial direction and the radial direction satisfies 0 < θ ≤ 45°.

[0012] Among them, the concave curve adopts at least one of an arc, an exponential curve, a parabola, and a Bessel curve.

[0013] A centrifugal fan includes a volute and an impeller installed in the volute. At the air inlet of the volute, the above-mentioned air inlet ring for pre-whirl inlet with fixed guide vanes is installed, and the flow guiding cone is arranged on the side of the installation ring away from the impeller.

[0014] Among them, the included angle α between the chord line of the guide vane profile and the axial direction and the inlet blade setting angle β of the impeller satisfy 0.8β ≤ α ≤ 1.2β.

[0015] An oil fume extractor adopts the above-mentioned air inlet ring for pre-whirl inlet with fixed guide vanes.

[0016] A range hood adopts the centrifugal fan.

[0017] According to the technical scheme described in the present invention, the following beneficial effects are achieved: the guide cone and the mounting ring are spaced apart in the axial direction, and the guide cone is designed to protrude outside the mounting ring so that the guide cone plays a wind-breaking role; the guide vanes that extend continuously along the concave curve can not only disperse stress through the concave curve design to provide greater strength support, but the concave curve design of the guide vanes is also more in line with aerodynamic principles and is therefore more conducive to guiding the airflow and sound wave propagation direction and better dispersing the incoming flow. In addition, the continuous design of the guide vanes can also effectively ensure the continuity of the airflow movement in the radial direction, and the periodic airflow channel formed by the guide vanes arranged in an array around the axis also has a certain degree of sound insulation and reflection noise reduction effect on the radiated sound field inside the centrifugal fan. The existence of the angle between the chord line of the guide vane blade and the axial direction increases the projected area of ​​the guide vane in the radial direction of the air inlet circle, thereby increasing the coverage area on the air inlet side of the impeller, thereby reducing the risk of surge under high back pressure at the fan outlet; the regular change of the angle between the chord line of the guide vane blade and the axial direction along the radial outward direction also causes the airflow before entering the impeller to be gradually pre-swirled to be consistent with the impeller rotation direction, thereby effectively reducing the impact loss at the impeller inlet and avoiding flow separation on the impeller suction surface and causing blockage of the impeller flow channel. The radial projection of the line of intersection between the leading edge of the guide vane blade profile and the center arc line has different angles of deviation from the radial direction in different length ranges. Considering that the airflow in the central area of ​​the air inlet circle is less affected by the rotation of the impeller and the overall intake flow is relatively stable, the radial deviation angle is smaller, and the area close to the circumferential edge of the air inlet circle is the key area for pre-rotation of the incoming flow. By following the radial deviation angle design according to specific rules, the airflow is facilitated to enter the impeller more smoothly and the kinetic energy loss of the airflow is minimized. The component of the airflow along this angle also tends to be consistent with the rotation direction of the impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the side structure of the air inlet ring.

[0019] Figure 2 The structure of the air inlet ring is shown from a top view Figure 1 .

[0020] Figure 3 The structure of the air inlet ring is shown from a top view Figure 2 .

[0021] Figure 4 It is a schematic diagram of the longitudinal cross-section structure of the air inlet ring.

[0022] Figure 5 It is a schematic diagram of the structure of the guide vane of the air inlet ring after being cut into a cylindrical section concentric with the axis, which shows the blade shape of the guide vane.

[0023] Figure 6 for Figure 5 The enlarged view of the middle K part shows the profile line, center arc line and chord line of the guide vane.

[0024] Figure 7 : is a distribution diagram of the relationship between the angle α between the chord line of the guide vane and the axial direction and the value of Di in the radial direction outward in an embodiment.

[0025] Figure 8 Schematic diagram of the exploded structure of a centrifugal fan.

[0026] Fig. 9 It is a schematic diagram of the impeller structure from a top view.

[0027] 1 guide cone, 10 air flow hole, 2 guide vane, 3 mounting ring, 4 volute, 40 air inlet, 5 impeller, L the line connecting the intersection of the leading edge of the guide vane blade profile and the middle arc line of the guide vane blade profile. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings:

[0029] See also Figure 1 , 4 As shown in Figures 5 and 8, a pre-rotation air inlet ring with fixed guide vanes includes a guide cone 1, a guide vane 2 and a mounting ring 3 connected in sequence radially outward, the guide vane 2 is evenly spaced along the circumferential direction, the guide cone 1 and the mounting ring 3 are spaced in the axial direction, and the guide vane 2 extends continuously from the guide cone 1 to the mounting ring 3 along the concave curve. In the present application, the guide cone and the mounting ring are spaced in the axial direction, and the guide cone is designed to protrude from the mounting ring so that the guide cone plays a wind-breaking role. In the present application, the guide vane is continuously extended along the concave curve, which can not only disperse the stress through the concave curve design to provide greater strength support, but also the concave curve design of the guide vane is more in line with the aerodynamic principle and is more conducive to guiding the airflow and sound wave propagation direction and better dispersing the incoming flow. In addition, in the present application, the continuous extension of the guide vane along the concave curve can also effectively ensure the continuity of the airflow movement in the radial direction, and the periodic airflow channel formed by the arrangement of the guide vanes around the axis array also has a certain degree of sound insulation and reflection noise reduction effect on the radiated sound field inside the centrifugal fan. Preferably, the guide cone is designed with air flow holes 10, which is beneficial to increase the air inlet area and ensure high air volume performance.

[0030] See also Figures 1 to 7 As shown, the guide vane 2 adopts a variable-section twisted blade, the trailing edge of the blade profile of the guide vane 2 gradually bends radially outward and away from the leading edge of the blade profile of the guide vane 2, and the angle α between the chord line of the guide vane 2 and the axial direction in the radial direction meets the following relationship: f(α)=a 1 *Di 3 +a 2 *Di 2+a 3 *Di + a 4 where 0.04 ≤ a 1 ≤ 0.05, -0.5 ≤ a 2 ≤ -0.35, 5.1 ≤ a 3 ≤ 5.8, -0.2 ≤ a 4 ≤ 0.5. Di is the length measured from the center of the axis along the projection in the radial direction of the intersection point between the leading edge of the blade profile of guide vane 2 and the mean camber line of the blade profile of guide vane 2 with respect to the projection of the connection line L between the intersection point between the leading edge of the blade profile of guide vane 2 and the mean camber line of the blade profile of guide vane 2 in the radial direction, and D1 / 2 < Di ≤ D3 / 2. D1 is the diameter of the projection of the flow guide cone 1 in the radial direction, and D3 is the diameter of the ring where the maximum value of the length of the projection of guide vane 2 in the radial direction is located. In this application, the existence of the angle between the chord line of the guide vane blade profile and the axial direction increases the projected area of the guide vane in the radial direction of the air inlet circle, thus increasing the covered area on the air inlet side of the impeller, and further reducing the risk of surge phenomenon under high back pressure at the outlet of the fan. It is also beneficial to construct a sound wave propagation channel inward (along the air flow direction) (i.e., guide the sound wave to propagate along the air flow direction). That is, the resistance of the air flow entering the impeller is smaller, while the resistance of the reverse flow movement is larger, which is beneficial to improving the noise experience during the use of the centrifugal fan and the range hood. Moreover, the regular change of the angle between the chord line of the guide vane blade profile and the axial direction along the radial outward direction also makes the air flow before entering the impeller gradually pre-rotated to be consistent with the rotation direction of the impeller, thereby effectively reducing the impact loss at the impeller inlet, avoiding the flow separation on the suction surface of the impeller and causing the blockage of the impeller flow passage. At the same time, pre-rotating the oncoming flow can also reduce the aerodynamic noise generated by the impact at the impeller inlet.

[0031] See Figures 1 to 3 As shown, guide vane 2 is integrally in a tongue-shaped spoon shape.

[0032] See Figures 1 to 3 As shown, when D1 / 2 < Di < Da / 2, the projection of the connection line L between the intersection point between the leading edge of the blade profile of guide vane 2 and the mean camber line of the blade profile of guide vane 2 in the radial direction extends linearly and the deviation angle θ from the radial direction is θ ≤ 2°; when Da / 2 ≤ Di ≤ D3 / 2, the deviation angle θ of the projection of the connection line L between the intersection point between the leading edge of the blade profile of guide vane 2 and the mean camber line of the blade profile of guide vane 2 in the radial direction from the radial direction conforms to the following relational expression: f(θ) = b 1 *Di 3 +b 2 *Di 2 +b 3 *Di + b 4 where 0.06 ≤ b 1 ≤ 0.08, -0.7 ≤ b 2 ≤ -0.9, 3 ≤ b 3≤4.5, -3.5≤b 4 ≤-3, and 0.7≤Da / D3≤0.9. In the present application, the projection of the intersection line between the leading edge of the guide vane blade profile and the middle arc line in the radial direction has different angles of deviation from the radial direction in different length ranges. Considering that the airflow in the central area of ​​the air inlet circle is less affected by the rotation of the impeller and the overall intake flow is relatively stable, the radial deviation angle is smaller, while the area close to the circumferential edge of the air inlet circle is the key area for the pre-rotation of the incoming flow. By following the radial deviation angle design according to a specific rule, the airflow is facilitated to enter the impeller more smoothly and the kinetic energy loss of the airflow is minimized, the intake flow velocity is increased, and the component of the airflow turning along this angle is more inclined to be consistent with the rotation direction of the impeller.

[0033] See also Figures 1 to 3 As shown, when Da / 2≤Di≤D3 / 2, the angle θ of the projection of the line L between the leading edge of the blade profile of the guide vane 2 and the mid-arc line of the guide vane 2 in the radial direction deviates from the radial direction to satisfy 0<θ≤45°. In the present application, the radial velocity component of the inlet airflow is made consistent with the impeller rotation direction by matching the radial inclination angle of the guide vane with the impeller inlet placement angle. Compared with the state without pre-swirl, the risk of blocking the blade flow path caused by the impeller suction surface separation caused by the impeller inlet impact loss can be effectively reduced.

[0034] See also Figure 4 As shown, the concave curve adopts at least one of a circular arc, an exponential curve, a parabola, and a Bezier curve.

[0035] See also Figure 8 As shown, a centrifugal fan includes a volute 4 and an impeller 5 installed in the volute 4, and the above-mentioned pre-swirl air inlet ring with fixed guide vanes is installed at the air inlet 40 of the volute 4, and the guide cone 1 is arranged on the side of the installation ring 3 away from the impeller 5.

[0036] See also Figure 8 , 9 As shown, the angle α between the chord line of the blade profile of the guide vane 2 and the axial direction and the inlet placement angle β of the impeller 5 satisfy 0.8β≤α≤1.2β.

[0037] Furthermore, a range hood adopts the above-mentioned pre-swirl air inlet ring with fixed guide vanes.

[0038] Furthermore, a range hood adopts the centrifugal fan.

[0039] Measured data show that, under the same working air volume, the range hood equipped with the above-mentioned pre-swirl air inlet ring with fixed guide vanes has a significantly reduced working noise by 0.7-1.2dB compared to the range hood equipped with the traditional air inlet ring in the prior art (based on the standard "GBT 17713-2022 Range hoods and other cooking fume suction and exhaust devices").

[0040] Although the specific embodiments of the present invention have been described above, those skilled in the art may modify them without departing from the spirit and principles of the present invention. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. An air inlet ring for pre-swirl air inlet with fixed guide vanes, comprising a guide cone, a guide vane and a mounting ring which are sequentially connected radially outward, wherein the guide vanes are evenly spaced and arranged circumferentially, and characterized in that: The guide cone and the mounting ring are spaced apart in the axial direction, and the guide vane extends continuously from the guide cone along a concave curve toward the mounting ring.

2. The air inlet ring for pre-swirl air inlet with fixed guide vanes according to claim 1, characterized in that: The guide vane adopts a variable cross-section twisted blade, the trailing edge of the profile line of the guide vane gradually bends outward in the radial direction and is away from the leading edge of the profile line of the guide vane. The included angle α between the chord line of the guide vane profile and the axial direction in the radial outward direction conforms to the following relational expression: f(α) = a1*Di 3 + a2*Di 2 + a3*Di + a4, where 0.04 ≤ a1 ≤ 0.05, -0.5 ≤ a2 ≤ -0.35, 5.1 ≤ a3 ≤ 5.8, -0.2 ≤ a4 ≤ 0.

5. Di is the length starting from the center of the axis and measured along the projection in the radial direction of the intersection point between the leading edge of the profile line of the guide vane and the mean camber line of the guide vane profile relative to the projection of the connection line between the intersection points of the leading edge of the profile line of the guide vane and the mean camber line of the guide vane profile in the radial direction, and D1 / 2 < Di ≤ D3 / 2. D1 is the diameter of the projection of the flow guide cone in the radial direction, and D3 is the diameter of the ring where the maximum value of the projection length of the guide vane in the radial direction is located.

3. The air inlet ring for pre-swirl air inlet with fixed guide vanes according to claim 2 is characterized in that: The guide vane is tongue-shaped and spoon-shaped as a whole.

4. The air inlet ring for pre-swirl air inlet with fixed guide vanes according to claim 2 or 3, characterized in that: When D1 / 2 < Di < Da / 2, the projection of the line connecting the intersection points between the leading edge of the profile line of the guide vane and the mean camber line of the guide vane in the radial direction extends linearly and the included angle θ deviating from the radial direction satisfies θ ≤ 2°; when Da / 2 ≤ Di ≤ D3 / 2, the included angle θ of the projection of the line connecting the intersection points between the leading edge of the profile line of the guide vane and the mean camber line of the guide vane in the radial direction deviates from the radial direction and conforms to the following relational expression: f(θ) = b1 * Di 3 + b2 * Di 2 + b3 * Di + b4, where 0.06 ≤ b1 ≤ 0.08, -0.7 ≤ b2 ≤ -0.9, 3 ≤ b3 ≤ 4.5, -3.5 ≤ b4 ≤ -3, and 0.7 ≤ Da / D3 ≤ 0.

9.

5. The air inlet ring for pre-swirl air inlet with fixed guide vanes according to claim 4, characterized in that: When Da / 2≤Di≤D3 / 2, the angle θ of the projection of the line connecting the intersection of the leading edge of the guide vane profile and the mid-camber line of the guide vane profile in the radial direction deviates from the radial direction satisfies 0<θ≤45°.

6. The air inlet ring for pre-swirl air inlet with fixed guide vanes according to any one of claims 1 to 3 and 5, characterized in that: The concave curve is at least one of a circular arc, an exponential curve, a parabola, and a Bezier curve.

7. A centrifugal fan, comprising a volute and an impeller installed in the volute, characterized in that: An air inlet ring for pre-swirl air inlet with fixed guide vanes as claimed in any one of claims 2 to 6 is installed at the air inlet of the volute, and the guide cone is arranged on a side of the installation ring away from the impeller.

8. A centrifugal fan according to claim 7, characterized in that: The angle α between the chord line of the guide vane profile and the axial direction and the inlet placement angle β of the impeller satisfy 0.8β≤α≤1.2β.

9. A range hood, characterized in that: An air inlet ring for pre-swirl air inlet with fixed guide vanes as described in any one of claims 1 to 6 is used.

10. A range hood, characterized in that: Use the centrifugal fan described in claim 7 or 8.

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