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

Abstract

An air inlet ring 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 flow guide cone and the installation ring are arranged at intervals in the axial direction, and the guide vanes extend towards the installation ring from the flow guide cone along a concave curve. Compared with the prior art, the technical scheme provided by the utility model has the following advantages that wind breaking dispersion is carried out on incoming flow, the incoming flow prewhirl effect is more obvious, the flow separation of the suction surface of the impeller can be prevented, the fan surge can be prevented, the pneumatic structure is more reasonable, and the noise reduction effect is more excellent.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of air inlet ring for centrifugal fan, especially to an air inlet ring for pre-swirl air inlet with fixed guide vanes, a centrifugal fan and an extractor hood. BACKGROUND

[0002] In today's kitchen appliance market, the performance of the extractor hood is facing unprecedented challenges. With the reduction of living space and the increase of building density, the effective discharge of oil fume and the control of noise and other related performances of the extractor hood have become the focus of users when purchasing the extractor hood. In the prior art, the extractor hood adopts a forward multi-wing centrifugal fan system for smoke exhaust. Generally, the structure for providing air inlet guide for the centrifugal fan also adopts a traditional design, i.e., a ring-shaped guide structure is formed by rotating a circular arc or a smooth curve to improve the air inlet flow state at the impeller of the centrifugal fan, thereby improving the smoke exhaust effect and reducing the smoke exhaust noise. For example, a Chinese invention application with the title of "air guide air inlet ring and centrifugal fan" and the application publication number CN114017392A discloses: an air guide air inlet ring for a centrifugal fan, the air guide air inlet ring is formed with a plurality of guide structures to guide the airflow from the outer side of the air guide air inlet ring to the air inlet of the centrifugal fan at the inner side of the air guide air inlet ring; the plurality of guide structures are rotationally symmetrical about the center of the air guide air inlet ring, the guide structures form arc-shaped guide paths to deflect the airflow, so that the airflow passing through the plurality of guide paths moves in a preset movement direction, the preset movement direction has a tangential movement component consistent with the rotation direction of the impeller of the centrifugal fan. The guide structures form arc-shaped guide paths to deflect the airflow to generate a tangential movement in the same direction as the linear speed of the impeller. Under the joint action of the air inlet traction force of the fan, the inlet airflow rotates and moves into the fan. This pre-rotation method of the airflow improves the uniformity of the air inlet airflow, increases the air inlet flow area, and makes the airflow more easily enter the impeller; the airflow has a certain tangential velocity, so that when the airflow enters the blade flow passage, it has a movement trend close to the rotation direction of the impeller, and has a small tangential velocity difference relative to the blade, thereby weakening the airflow separation in the blade flow passage, optimizing the airflow flow in the flow passage, and solving the problems of poor smoke suction effect and significant vortex impact noise caused by non-uniform airflow at the air inlet of the fan.

[0003] However, due to the asymmetry of the internal flow passage of the volute of the centrifugal fan, when the impeller of the centrifugal fan rotates, the pressure distribution of the air inlet ring in the radial direction is uneven, the traditional air inlet ring structure cannot meet the demand of pre-rotation and flow regulation of the incoming flow before entering the impeller, and when the airflow enters the centrifugal fan, a large impact loss and a large aerodynamic noise will be generated. In view of such problems, many experts and engineers have made certain improvement schemes, and the common improvement schemes are: adding annular or radial structures, honeycomb structures, grid structures and the like to the existing air inlet ring, so as to improve the airflow direction and make the air inlet pressure of the impeller more uniform and improve the aerodynamic noise. For example, a Chinese utility model patent with the title of "air inlet grid and fan assembly with the same" and the authorization announcement number of CN218882569U discloses: an air inlet grid, comprising: a mounting frame (1); a flow guide disc (2) located on one side of the mounting frame (1); a radial blade group (3) connected between the mounting frame (1) and the flow guide disc (2); a circumferential blade (4) connected to the radial blade group (3); wherein; the direction of the airflow is guided through the cooperation of the radial blade group (3) and the circumferential blade (4). The technical scheme of the invention application makes the inlet airflow consistent with the rotation direction of the impeller through the radial blade group and the circumferential blade, avoids the increase of the blade inlet impact loss without pre-rotation, causes the flow separation and blockage of the impeller suction surface, and realizes the purposes of noise reduction, anti-surge and performance improvement of the fan. For another example, a Chinese invention application with the title of "a flow collector and a range hood" and the application publication number of CN116857230A discloses: a flow collector installed at the air inlet of a fan of a range hood, the flow collector comprising: a flow collector body (21); a plurality of pre-rotation guide vanes (22) arranged on the inner side of the flow collector body (21), the first end of the pre-rotation guide vane (22) being connected with the flow collector body (21), and the adjacent two pre-rotation guide vanes (22) being spaced apart; a uniform gas net (23) arranged on the inner side of the pre-rotation guide vane (21) and connected with the second end of the pre-rotation guide vane (22); the relationship formula D b -D a1 ≥2W is satisfied between the impeller (3) of the fan and the flow collector; wherein, D b is the inner diameter of the impeller (3) of the fan, D a1 is the inner diameter of the pre-rotation guide vane (22), and W is the minimum radial gap requirement between the flow collector and the impeller (3). The pre-rotation guide vane (22) is twisted along the axial direction to form a first twisted top end and a second twisted top end, the convex directions of the first twisted top end and the second twisted top end are the same as the rotation direction of the impeller (3), the first twisted top end is the air inlet, the second twisted top end is the air outlet, the angle between the tangent line of the first twisted top end and the tangent line of the circle where the air inlet diameter D a of the flow collector body (21) is F2, and the angle between the tangent line of the second twisted top end and the inner diameter D a1The angle between the tangents of the circle where it is located is F1, F1, F2 ∈ [0° - 90°], F1 ∈ [0 - α + 25°], F1 ≤ F2; where α is the installation angle of the air inlet of the blade (31).

[0004] However, from the perspective of actual application effects, most of the above improvement schemes only play a role in safety protection and limited flow rectification, and the improvement effect on noise is not obvious (even in individual schemes, the setting of circumferential blades affects the radial component of the air flow, and the air flow movement lacks coherence, resulting in flow separation on the suction surface of the impeller). In particular, it is impossible to break and disperse the incoming flow, and the pre-whirl performance of the incoming flow has not yet approached the high threshold. Summary of the Utility Model

[0005] In view of the deficiencies of the prior art, the present utility model provides an air inlet ring for pre-whirl air inlet with fixed guide vanes, a centrifugal fan, and an oil fume extractor, which can break and disperse the incoming flow, have a more significant pre-whirl effect on the incoming flow, thus preventing flow separation on the suction surface of the impeller, preventing fan surging, having a more reasonable pneumatic structure, and a better noise reduction effect.

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

[0007] An air inlet ring for pre-whirl air inlet with fixed guide vanes includes a guide cone, guide vanes, and an installation ring that are sequentially connected to each other radially outward. The guide cone and the installation ring are spaced apart in the axial direction, and the guide vanes extend from the guide cone along a concave curve towards the installation ring.

[0008] Among them, the guide vanes adopt variable-section twisted blades. The trailing edge of the profile line of the guide vane blade gradually curves radially outward and away from the leading edge of the profile line of the guide vane blade. The angle α between the chord line of the guide vane blade and the axial direction in the radial outward direction conforms to the following relational formula: 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 measured from the center of the circle where the axis is located along the projection of the intersection point between the leading edge of the profile line of the guide vane blade and the mean camber line of the guide vane blade in the radial direction relative to the projection of the line connecting the intersection points between the leading edge of the profile line of the guide vane blade and the mean camber line of the guide vane blade in the radial direction, and D1 / 2 < Di ≤ D3 / 2. D1 is the diameter of the projection of the guide cone in the radial direction, and D3 is the diameter of the ring where the maximum value of the length of the projection of the guide vane in the radial direction is located.

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

[0010] Wherein, when D1 / 2 < Di < Da / 2, the projection of the connection line of the intersection points between the leading edge of the profile line of the guide vane profile and the mean camber line of the guide vane profile extends linearly in the radial direction and the included angle θ deviating from the radial direction is θ ≤ 2°; when Da / 2 ≤ Di ≤ D3 / 2, the included angle θ of the projection of the connection line of the intersection points between the leading edge of the profile line of the guide vane profile and the mean camber line of the guide vane profile deviating from the radial direction conforms to the following relational expression: f(θ) = b1 * Di 3 + b2 * Di 2 + b3 * Di + b4, wherein, 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.

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

[0012] Wherein, 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 air 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] Wherein, the included angle α between the chord line of the guide vane profile and the axial direction and the inlet 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 air inlet with fixed guide vanes.

[0016] An oil fume extractor adopts the above-mentioned centrifugal fan.

[0017] According to the technical solution described in this utility model, the following beneficial effects are achieved: the guide cone and the mounting ring are spaced apart in the axial direction, and the design of the guide cone protruding beyond the mounting ring enables the guide cone to play 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 also the concave curve design of the guide vanes is more in line with the aerodynamic principle, thus being more conducive to guiding the direction of airflow and sound wave propagation and better dispersing the incoming flow. In addition, the continuous design of the guide vanes can also effectively ensure the coherence 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, reflection and noise reduction effect on the radiated sound field inside the centrifugal fan. The angle between the chord line of the guide vane and the axial direction increases the projected area of ​​the guide vane in the radial direction of the inlet ring, thus increasing the coverage area on the inlet side of the impeller and 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 and the axial direction in the radial direction also gradually pre-swirls the airflow before entering the impeller to be consistent with the impeller's rotation direction, thereby effectively reducing the impact loss at the impeller inlet and avoiding impeller flow channel blockage caused by flow separation from the impeller suction surface. The radial projection of the line connecting the leading edge and the middle arc of the guide vane profile deviates from the radial direction at different angles within different length ranges. Considering that the airflow in the central area of ​​the inlet ring is less affected by the impeller rotation and the overall inlet flow is relatively stable, the radial deviation angle is small. However, the area near the circumferential edge of the inlet ring is the key area for pre-swirl of the inlet flow. By designing the radial deviation angle according to a specific rule, the airflow can enter the impeller more smoothly and the kinetic energy loss of the airflow can be minimized. The component of the airflow along this angle is also more likely to be consistent with the impeller rotation direction. Attached Figure Description

[0018] Figure 1 This is a side view of the air inlet ring structure.

[0019] Figure 2 Schematic diagram of the air intake ring from top view Figure 1 .

[0020] Figure 3 Schematic diagram of the air intake ring from top view Figure 2 .

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

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

[0023] Figure 6 for Figure 5 The enlarged view of section K shows the profile, mid-curve, and chord of the guide vane.

[0024] Figure 7 This is a diagram showing the relationship between the angle α between the chord of the guide vane and the axial direction and the value of Di along the radial outward direction in one embodiment.

[0025] Figure 8 This is a schematic diagram of the exploded structure of a centrifugal fan.

[0026] Figure 9 This is a top view of the impeller structure.

[0027] 1. Guide cone, 10. Airflow through hole, 2. Guide vane, 3. Mounting ring, 4. Volute, 40. Air inlet, 5. Impeller, L. The line connecting the leading edge of the guide vane profile and the mid-arc line of the guide vane profile. Detailed Implementation

[0028] The technical solution of this utility model will be further described below with reference to the accompanying drawings:

[0029] See Figure 1 , 4 As shown in Figures 5 and 8, an air inlet ring with fixed guide vanes for pre-rotating air intake includes a guide cone 1, a guide vane 2, and a mounting ring 3 connected sequentially in a radially outward direction. The guide cone 1 and the mounting ring 3 are spaced apart in the axial direction, and the guide vane 2 extends from the guide cone 1 along a concave curve towards the mounting ring 3. In this application, the guide cone and the mounting ring are spaced apart in the axial direction. This design, where the guide cone protrudes beyond the mounting ring, enables the guide cone to break the airflow. In this application, the guide vane extends continuously along the concave curve. This not only disperses stress through the concave curve design, thus providing greater strength support, but also conforms to aerodynamic principles, making it more conducive to guiding the airflow and sound wave propagation direction and better dispersing the incoming flow. Furthermore, in this application, the continuous extension of the guide vane along the concave curve effectively ensures the continuity of airflow movement in the radial direction. 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 noise reduction effect on the radiated sound field inside the centrifugal fan. Preferably, the guide cone is designed with airflow through holes 10, which helps to increase the air intake area and ensure large air volume performance.

[0030] See Figures 1 to 7 As shown, guide vane 2 adopts a variable cross-section twisted blade. The trailing edge of the guide vane 2 blade profile gradually bends outward radially and moves away from the leading edge of the guide vane 2 blade profile. The angle α between the radially outward chord of the guide vane 2 blade profile and the axial direction conforms to the following relationship: 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, and 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 relative 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. And D1 / 2 < Di ≤ D3 / 2, where 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 inlet circle, thus increasing the coverage area on the inlet side of the impeller, and further reducing the risk of surge under high back pressure at the outlet of the fan. It is also beneficial to construct a sound wave propagation channel inward (along the airflow direction) (that is, guiding the sound wave to propagate along the airflow direction). That is, the resistance of the airflow 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 gradually pre-rotates the airflow before entering the impeller to be consistent with the rotation direction of the impeller, thereby effectively reducing the impact loss at the impeller inlet, avoiding the blockage of the impeller flow passage caused by the separation of the suction surface of the impeller, and at the same time pre-rotating the incoming flow can also reduce the aerodynamic noise generated by the impact at the impeller inlet.

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

[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 angle θ deviating from the radial direction satisfies θ ≤ 2°; when Da / 2 ≤ Di ≤ D3 / 2, the 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 deviating from the radial direction conforms to the following relational formula: 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. In this application, the projection of the line connecting the intersection of the leading edge and the middle arc of the guide vane profile in the radial direction has different angles of deviation from the radial direction at different length ranges. Considering that the airflow in the central area of ​​the inlet ring is less affected by the impeller rotation and the overall inlet flow is relatively stable, the radial deviation angle is small. However, the area near the circumferential edge of the inlet ring is the key area for pre-swirl of the inlet flow. By designing the radial deviation angle according to a specific rule, the airflow enters the impeller more smoothly and minimizes the kinetic energy loss of the airflow, thereby increasing the inlet flow velocity. The component of the airflow turning at this angle is also more likely to be consistent with the impeller rotation direction.

[0033] See Figures 1 to 3 As shown, when Da / 2≤Di≤D3 / 2, the angle θ between the projection of the line L connecting the leading edge of the guide vane 2 and the mid-arc line of the guide vane 2 in the radial direction and the radial direction satisfies 0<θ≤45°. In this application, by matching the radial tilt angle of the guide vane with the impeller inlet placement angle, the radial velocity component of the intake airflow tends to be consistent with the impeller rotation direction. Compared with the state without pre-swirl, this can effectively reduce the risk of impeller suction surface deflow caused by impeller inlet impact loss and resulting in blockage of the blade flow channel.

[0034] See Figure 4 As shown, the concave curve is at least one of the following: circular arc, exponential curve, parabola, and Bézier curve.

[0035] See Figure 8 As shown, a centrifugal fan includes a volute 4 and an impeller 5 installed in the volute 4. The aforementioned pre-rotating air inlet ring with fixed guide vanes is installed at the air inlet 40 of the volute 4. The guide cone 1 is located on the side of the mounting ring 3 away from the impeller 5.

[0036] See Figure 8 , 9 As shown, the angle α between the chord 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 employs the aforementioned pre-rotating air intake ring with fixed guide vanes.

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

[0039] Actual measurement data shows that, under the same working air volume, the range hood with the above-mentioned pre-rotating air intake ring with fixed guide vanes has a significantly lower operating noise of 0.7-1.2 dB compared to the range hood with the traditional air intake ring design in the existing technology (based on the standard GBT 17713-2022 Range Hoods and Other Cooking Smoke Extraction Devices).

[0040] Although the specific embodiments of this utility model have been described above, those skilled in the art can make changes to it without departing from the spirit and principle of this utility model. The scope of protection of this utility model is defined by its claims and their equivalents.

Claims

1. An air inlet ring with fixed guide vanes for pre-rotating air intake, comprising a guide cone, guide vanes, and a mounting ring connected sequentially outward along the radial direction, characterized in that: The guide cone and the mounting ring are spaced apart in the axial direction, and the guide vane extends from the guide cone along a concave curve toward the mounting ring.

2. The pre-rotating air inlet ring 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 blade gradually bends outward in the radial direction and moves away from the leading edge of the profile line of the guide vane blade. The angle α between the chord line of the guide vane blade 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 measured from the center of the axis along the projection in the radial direction of the intersection point between the leading edge of the profile line of the guide vane blade and the mean camber line of the guide vane blade relative to the projection in the radial direction of the connection line between the intersection point between the leading edge of the profile line of the guide vane blade and the mean camber line of the guide vane blade, 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 length of the projection of the guide vane in the radial direction is located.

3. The pre-rotating air inlet ring with fixed guide vanes according to claim 2, characterized in that: The guide vane is generally tongue-shaped or spoon-shaped.

4. The pre-rotating air inlet ring with fixed guide vanes according to claim 2 or 3, characterized in that: When D1 / 2 < Di < Da / 2, the projection of the connecting line of the intersection points between the leading edge of the profile line of the guide vane profile and the mean camber line of the guide vane profile extends linearly in the radial direction and the included angle θ deviating from the radial direction is θ ≤ 2°; when Da / 2 ≤ Di ≤ D3 / 2, the included angle θ of the projection of the connecting line of the intersection points between the leading edge of the profile line of the guide vane profile and the mean camber line of the guide vane profile deviating from the radial direction 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 pre-rotating air inlet ring with fixed guide vanes according to claim 4, characterized in that: When Da / 2≤Di≤D3 / 2, the angle θ between the projection of the line connecting the leading edge of the guide vane profile and the middle arc line of the guide vane profile in the radial direction and the radial direction satisfies 0<θ≤45°.

6. The pre-rotating air inlet ring 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 the following: circular arc, exponential curve, parabola, and Bézier curve.

7. A centrifugal fan, comprising a volute and an impeller mounted in the volute, characterized in that: An air inlet ring with fixed guide vanes, as described in any one of claims 2 to 6, is installed at the air inlet of the volute, and the guide cone is located on the side of the mounting ring away from the impeller.

8. A centrifugal fan according to claim 7, characterized in that: The angle α between the chord of the guide vane 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: The air inlet ring with fixed guide vanes described in any one of claims 1 to 6 is used.

10. A range hood, characterized in that: The centrifugal fan described in claim 7 or 8 is used.

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