Centrifugal fans and air conditioners

Abstract

To provide a centrifugal fan which can make compatible both the reduction of a pressure loss and noise, and the integral molding of a hub and a blade.SOLUTION: A blade 1 constituting a centrifugal fan 100 is constituted so that shapes of cross sections 1A, 1B and 1C in three prescribed height positions between a hub 2 side and a shroud 3 side are superimposed on, and coincide with one another with respect to the same blade 1 at the inside of an inner edge 8 of a suction port 31, and has an outlet angle for the shroud 3 so as to be decreased toward the shroud 3 side from the hub 2 side. In the prescribed blade 1, a first cross point between a rear edge at a side opposite to a rotation direction of an impeller 101 and the shroud 3 is arranged at an anti-rotation side of a second cross point between the rear edge and the hub, and an inflection point arranged between the first cross point and the second cross point on the rear edge is arranged at the rotation direction side from a linear line passing the first cross point and the second cross point.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to a centrifugal fan and an air conditioner.

Background Art

[0002] In recent years, air conditioners are required to achieve energy saving, low noise, and low cost simultaneously. In the indoor unit of an air conditioner, it is preferable to improve the efficiency and reduce the noise of a low-cost centrifugal fan. Uniformization of the velocity distribution at the blade outlet of the centrifugal fan is an effective means for improving efficiency and reducing noise. Also, for cost reduction, it is preferable to manufacture the centrifugal fan with as few component parts as possible.

[0003] In the abstract of Patent Document 1, it is described that “at the first connection position (6h) which is the connection position between the blade (6) and the hub (5) at the trailing edge of the blade, the first tangent line (21) contacting the trailing edge extends in a direction approaching the shroud (4) toward the front side in the rotation direction of the blade (6), and at the second connection position (6s) which is the connection position between the blade (6) and the shroud (4), the second tangent line (22) contacting the trailing edge of the blade extends in a direction approaching the hub (5) toward the front side in the rotation direction of the blade (6).”

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] To achieve high efficiency and low noise, reducing the pressure loss of the indoor unit is a consideration. Reducing pressure loss necessitates a large airflow with a small pressure increase in the centrifugal fan used. Such centrifugal fans have a characteristic where the airflow at the blade outlet is biased towards the hub side. This results in an uneven velocity distribution in the heat exchanger located at the blade outlet, limiting the effectiveness of efficiency improvement and noise reduction. Furthermore, to reduce the manufacturing cost of the fan, it is preferable to be able to integrally mold the hub and blades. However, the centrifugal fan described in Patent Document 1 does not specify whether the hub and blades can be integrally molded. The problem that this disclosure aims to solve is to provide a centrifugal fan and air conditioner that can achieve both high efficiency and low noise, as well as integrated molding of the hub and blades. [Means for solving the problem]

[0006] The centrifugal fan of this disclosure comprises an impeller comprising a hub, a shroud having a gas intake port, and a plurality of blades disposed between the hub and the shroud, wherein, inside the edge of the intake port, the cross-sectional shapes of the same blade overlap and coincide at at least two predetermined height positions between the hub side and the shroud side, and the blades have an outlet angle that decreases from the hub side toward the shroud side, and of a given blade, the first intersection of the trailing edge opposite to the direction of rotation of the impeller and the shroud is located on the counter-rotation side of the second intersection of the trailing edge and the hub, and the inflection point located on the trailing edge between the first and second intersections is located on the rotational side of the straight line passing through the first and second intersections. The second intersection point is located on the rotational side of the inflection point. Other solutions will be described later in the embodiments for carrying out the invention. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a centrifugal fan and air conditioner that can achieve both high efficiency and low noise, as well as integrated molding of the hub and blades. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates an indoor unit and an air conditioner equipped with a centrifugal fan according to the present disclosure. [Figure 2A] This diagram shows the flow field near the shroud at the blade outlet in a conventional centrifugal fan, and it is a diagram with a relatively small width. [Figure 2B] This diagram shows the flow field near the shroud at the blade outlet of a conventional centrifugal fan, and the width is relatively medium. [Figure 2C] This diagram shows the flow field near the shroud at the blade exit of a conventional centrifugal fan, and it is a diagram with a relatively large width. [Figure 3] This is a perspective view of the centrifugal fan in this disclosure. [Figure 4] This figure illustrates the shape of the trailing edge of the centrifugal fan of this disclosure. [Figure 5A] This diagram shows the flow field near the shroud at the blade outlet in a conventional centrifugal fan. [Figure 5B] This figure shows the flow field near the shroud at the blade outlet in the centrifugal fan of this disclosure. [Figure 6A] This diagram illustrates the velocity triangle at the trailing edge of the blade in the centrifugal fan of this disclosure, and also illustrates the position of the cross-section in the height direction. [Figure 6B] This diagram illustrates the velocity triangle at the trailing edge of the blade in the centrifugal fan of this disclosure, and shows the velocity triangle in the cross-section along line A1-A1. [Figure 6C] This diagram illustrates the velocity triangle at the trailing edge of the blade in the centrifugal fan of this disclosure, and shows the velocity triangle in the cross section along the line C1-C1. [Figure 6D] This diagram illustrates the velocity triangle at the trailing edge of the blade in the centrifugal fan of this disclosure, and shows the velocity triangle in the cross-section along line B1-B1. [Figure 7] This figure shows the overlapping state of the blade cross-sections in the centrifugal fan of this disclosure. [Figure 8A] This diagram illustrates the manufacturing method for integrally molded wings and hubs, and shows the molding process of the wings and hubs using a mold. [Figure 8B] This is a diagram illustrating the manufacturing method of a one-piece molded wing and hub, specifically showing the process of removing the mold. [Figure 9]It is an explanatory diagram of variables that define the shape of the trailing edge of the blade in another embodiment. [Figure 10A] In another embodiment, it is a diagram explaining the quantitative effect of the angle θs calculated by numerical fluid analysis, and it is a graph showing the ratio of the axial power. [Figure 10B] In another embodiment, it is a diagram explaining the quantitative effect of the angle θs calculated by numerical fluid analysis, and it is a graph showing the difference in noise. [Figure 11A] In another embodiment, it is a diagram explaining the quantitative effect of the angle θs+ calculated by numerical fluid analysis, and it is a graph showing the ratio of the axial power. [Figure 11B] In another embodiment, it is a diagram explaining the quantitative effect of the angle θs+ calculated by numerical fluid analysis, and it is a graph showing the difference in noise. [Figure 12A] In another embodiment, it is a diagram explaining the quantitative effect of the ratio of the length to the outer diameter calculated by numerical fluid analysis, and it is a graph showing the ratio of the axial power. [Figure 12B] In another embodiment, it is a diagram explaining the quantitative effect of the ratio of the length to the outer diameter calculated by numerical fluid analysis, and it is a graph showing the difference in noise.

Modes for Carrying Out the Invention

[0009] Hereinafter, modes for carrying out the present disclosure (referred to as embodiments) will be described with reference to the drawings. In the description of one of the following embodiments, descriptions of other embodiments applicable to one embodiment will be given as appropriate. The present disclosure is not limited to the following embodiments, and different embodiments can be combined with each other, or arbitrarily modified within a range that does not significantly impair the effects of the present disclosure. Also, the same members will be denoted by the same reference numerals, and overlapping descriptions will be omitted. Furthermore, those having the same function will be given the same name. The illustrated content is merely schematic, and for the convenience of illustration, it may be changed from the actual configuration within a range that does not significantly impair the effects of the present disclosure, or the illustration of some members may be omitted or deformed between the drawings.

[0010] Figure 1 illustrates an indoor unit 300 and an air conditioner 400 equipped with a centrifugal fan 100 of the present disclosure. The air conditioner 400 comprises an indoor unit 300 and an outdoor unit 302. The indoor unit 300 comprises a centrifugal fan 100 (described later) and a heat exchanger 5 that exchanges heat with indoor gas (e.g., air). The outdoor unit 302 comprises a heat exchanger 305 that exchanges heat with outside air, a compressor 301 that compresses a refrigerant, and an expansion mechanism 303 that expands the refrigerant. The compressor 301, heat exchanger 305, expansion mechanism 303, and heat exchanger 5 function as a refrigeration cycle as the refrigerant flows through piping 306. The direction of refrigerant flow can be controlled, for example, by a three-way valve (not shown) provided in the refrigeration cycle. Furthermore, the air conditioner 400 may be a so-called simultaneous cooling and heating multi-type air conditioner in which multiple indoor units 300 are connected to one outdoor unit 302.

[0011] The indoor unit 300 is, for example, an indoor unit installed on the ceiling surface RS of a room that blows conditioned gas in four directions (hereinafter, as appropriate, referred to as a four-way indoor unit). The centrifugal fan 100 blows out a gas such as air by drive and is equipped with an impeller 101. The impeller 101 is equipped with a plurality of blades 1, a hub 2, and a shroud 3. The blades 1 are arranged at integral intervals. The hub 2 is, for example, disc-shaped. The shroud 3 is annular-shaped. The shroud 3 is equipped with an intake port 31 for gas such as air. The blades 1 are arranged between the hub 2 and the shroud 3 and are formed, for example, with the same thickness (for example, with the same cross-sectional shape) in the direction between the hub 2 and the shroud 3. In the example of this disclosure, the blades 1 and the hub 2 are, for example, integrally molded products made of resin. This makes it possible to reduce the manufacturing costs of the impeller 101, centrifugal fan, and indoor unit 300. Integral molding can be performed, for example, by injection molding.

[0012] The indoor unit 300 is equipped with a bell mouth 4 on the side of the gas intake port 31 to the shroud 3. The bell mouth 4 is equipped with an intake port 41 for drawing in indoor air on the side opposite to the side connected to the intake port 31. The indoor unit 300 is equipped with a heat exchanger 5 on the side of the gas outlet 61 from the blade 1, and an outlet 6 downstream of the heat exchanger 5. The outlet 61, formed between the edge of the hub 2 and the edge of the shroud 3, has a width b2 which is the length between the hub 2 and the shroud 3. The indoor unit 300 is equipped with a motor 7 connected to the hub 2. The rotational drive of the motor 7 causes the impeller 101 to rotate around the rotation axis L0. The indoor unit 300 is equipped with a housing 200. The centrifugal fan 100 equipped with the impeller 101, the bell mouth 4, the heat exchanger 5, the motor 7, etc. are housed in the housing 200. The rotational drive of the motor 7 causes the air inside the room to pass through the bell mouth 4, the outlet 61 formed between the adjacent blades 1, and the heat exchanger 5, in the order of flow S and flow T, and is blown into the room from the outlet 6.

[0013] Figure 2A shows the flow field near the shroud 3 at the outlet of blade 1 in a conventional centrifugal fan, where the width b2 is relatively small. Figure 2B shows the flow field near the shroud 3 at the outlet of blade 1 in a conventional centrifugal fan, where the width b2 is relatively medium. Figure 2C shows the flow field near the shroud 3 at the outlet of blade 1 in a conventional centrifugal fan, where the width b2 is relatively large. In a conventional centrifugal fan, in a cylindrical unfolded diagram as shown in Figure 4 below, blade 1 is represented by a straight line between the hub 2 and the shroud 3. Hereafter, when referring to a conventional centrifugal fan, it refers to a centrifugal fan having this structure. Figures 2A to 2C are velocity contour plots calculated by numerical fluid analysis in the region X in Figure 1, with the width b2 of the outlet 61 (Figure 1) as a variable, and represent the velocity relative to the velocity vector. In Figures 2A to 2C, the velocity inside the impeller 101 is shown as relative velocity, and the velocity outside the impeller 101 is shown as absolute velocity. Darker colors indicate higher velocity, and lighter colors indicate lower velocity (see Figure 2C).

[0014] To improve the efficiency and reduce the noise of the indoor unit 300, efforts are made to equalize the velocity distribution of the gas flowing into the heat exchanger 5. Specifically, for example, an increase in width b2 can be considered. As shown by the flow S in Figure 1 above, the gas flow is redirected radially by the centrifugal fan 100 from the axial direction of the motor 7. As shown in Figures 2A to 2C, because the shroud 3 has a small radius of curvature, a flow U indicating reverse flow is generated. The flow U increases as the width b2 increases. This flow U2 causes turbulence in the gas flow. Therefore, simply increasing the width b2 as shown in Figure 2 to equalize the velocity distribution will increase the flow U2 and cause turbulence. For this reason, simply increasing the width b2 has limitations in equalizing the velocity distribution of the gas passing through the heat exchanger 5 due to the presence of flow U.

[0015] Figure 3 is a perspective view of the centrifugal fan 100 of this disclosure. The direction indicated by the white arrow is the rotation direction of the impeller 101 (unless otherwise specified, the same applies hereafter). In the centrifugal fan 100, of a given blade 1 (one of a plurality of blades 1, when focusing on that blade 1), intersection B (first intersection) is located on the opposite side of rotation from intersection A (second intersection). Intersection B is the intersection of the trailing edge TE on the opposite side of the rotation direction of the impeller 101 and the shroud 3. In the illustrated example, the trailing edge TE is the portion exposed to the outside of the impeller 101. The blade 1 is formed between the trailing edge TE and the leading edge FE. Intersection A is the intersection of the trailing edge TE and the hub 2.

[0016] Figure 4 illustrates the shape of the trailing edge TE of the centrifugal fan 100 of this disclosure. Figure 4 is a cylindrical unfolded view of the centrifugal fan 100 having a cylindrical appearance, with the blade 1 unfolded on a cylindrical surface. The inflection point C, located on the trailing edge TE between intersection point B and intersection point A, is located on the rotational side of the straight line L1 passing through intersection point B and intersection point A. The inflection point C is the point where the slope of the tangent changes from increasing to decreasing, or from decreasing to increasing, with the inflection point C as the boundary.

[0017] By shaping the blade 1 as described in this disclosure, when the blade 1 rotates, the direction of the blade force acting on the air by the trailing edge TE can be changed between intersection A and inflection point C, and between inflection point C and intersection B, as shown by arrows M and N. Due to this difference in the direction of the blade force, the blade force indicated by arrow N is directed more downward toward the shroud 3. As a result, the gas is pressed toward the shroud 3. Due to the viscosity of the air, this effect occurs not only on the pressure surface PS of the blade 1 but also in the negative pressure surface SS region.

[0018] Figure 5A shows the flow field near the shroud 3 at the outlet of blade 1 in a conventional centrifugal fan. 。 Figure 5 B Figure 5A shows the flow field near the shroud 3 at the outlet of the blade 1 in the centrifugal fan 100 of this disclosure. Figures 5A and 5B are contour plots obtained in the same manner as in Figure 2 above. However, in Figures 5A and 5B, the color becomes darker as the amount of air flowing out on the near side perpendicular to the plane of the paper increases (see Figure 5B).

[0019] The regions X1 and X2 enclosed in white circles indicate reverse flow perpendicular to the plane of the paper. Due to the effect of this disclosure, the reverse flow in region X2 is lighter in color, and it can be confirmed that the reverse flow is suppressed compared to the conventional region X1. As a result, the velocity distribution at the outlet of the blade 1 can be made uniform, and the velocity distribution of the gas flowing into the heat exchanger 5 can be made uniform. As a result, higher efficiency and lower noise can be achieved for the indoor unit 300 (Figure 1).

[0020] Figure 6A is a diagram illustrating the velocity triangle at the trailing edge TE of blade 1 in the centrifugal fan of this disclosure, and illustrates the position in the height direction of the cross section. Figure 6B is a diagram illustrating the velocity triangle at the trailing edge TE of blade 1 in the centrifugal fan of this disclosure, and shows the velocity triangle in the A1-A1 cross section. Figure 6C is a diagram illustrating the velocity triangle at the trailing edge TE of blade 11 in the centrifugal fan of this disclosure, and shows the velocity triangle in the C1-C1 cross section. Figure 6D is a diagram illustrating the velocity triangle at the trailing edge TE of blade 1 in the centrifugal fan of this disclosure, and shows the velocity triangle in the B1-B1 cross section.

[0021] Figure 6A shows the cutting points of the impeller 101 perpendicular to the rotation axis L0 (Figure 1) near intersections A, B, and inflection point C. In addition, Figure 6D shows cross-sections 1A (Figure 6B) of the blade 1 cut along the line A1-A1 near intersection A (Figure 4), cross-section 1C (Figure 6C) of the blade 1 cut along the line C1-C1 near intersection C, and cross-section 1B of the blade 1 cut along the line B1-B1 near intersection B. In the velocity triangle of cross-section 1A, arrow u2A represents the circumferential velocity vector, arrow w2A represents the relative velocity vector, and arrow c2A represents the absolute velocity vector. Arrow cm2A is a vector extending perpendicularly from arrow u2A toward the intersection of arrows w2A and c2A, and is the radial velocity vector. Angle β2A is the flow angle, which is the angle between the relative velocity direction and the circumferential direction. The same applies to the arrows u2C, w2C, c2C, cm2C, u2B, w2B, c2B, cm2B and angles β2C, β2B in sections 1C and 1B.

[0022] As described above, in the specification requiring a large airflow with a small pressure increase for the centrifugal fan 100, the flow at the outlet of the blade 1 is biased towards the hub 2 side. Therefore, in this disclosure, for the purpose of high efficiency and low noise, the centrifugal fan 100 is designed so that the flow follows the blade 1 as closely as possible. Specifically, due to the bias of the flow at the outlet 61 of the blade 1 toward the hub 2 side, the radial velocity vectors indicated by arrows cm2A, cm2C, and cm2B become asymptotically smaller, for example, from the hub 2 side toward the shroud 3 side. Consequently, at the outlet 61 of the blade 1, the angles β2A, β2C, and β2B of the relative velocity vectors indicated by arrows w2A, w2C, and w2B have the relationship β2A > β2C > β2B.

[0023] Figure 7 shows the overlapping state of the cross-sections 1A, 1B, and 1C of the blades 1 in the centrifugal fan 100 of this disclosure. Figure 7 is a view of the centrifugal fan 100 from the side of the intake port 31 in Figure 1. The impeller 101 has an outer diameter D2. In Figure 7, for the sake of simplicity, only two adjacent blades 1 are shown among the multiple blades 1 arranged in the circumferential direction.

[0024] Wing 1 is the inner edge of the shroud 3 that constitutes the intake port 31 7In the inner portion 1a, the shapes of the cross-sections 1A, 1B, and 1C at at least two (three in the illustrated example) predetermined height positions between the hub 2 side (far side of the paper) and the shroud 3 side (foreground side of the paper) overlap and coincide for the same wing 1. That is, the inner edge 7 Further inside, the shapes of cross-sections 1A, 1B, and 1C overlap and coincide, as shown in Figure 7. This coincidence is not limited to a strict agreement, but includes the concept of "approximate agreement," which allows for slight differences that do not affect the gas flow (especially those that do not have a significant impact).

[0025] Furthermore, the wing 1 has exit angles βb2A, βb2B, and βb2C such that they decrease from the hub 2 side towards the shroud 3 side. The exit angles βb2A, βb2B, and βb2C are the angles of the wings 1A, 1B, and 1C with respect to the tangent to the annular (circular in Figure 7) shroud 3 in cross-sections 1A, 1B, and 1C. Therefore, the wing 1 has an inner edge 7 In the outer portion 1b, the exit angles βb2A, βb2B, and βb2C are set such that the relationship β2A > β2C > β2B (see Figures 6B, 6C, and 6D) is satisfied. That is, the exit angles βb2A, βb2B, and βb2C are set such that the angle of the shroud 3 with respect to the tangent decreases asymptotically from the hub 2 side towards the shroud 3 side, for example, so that βb2A > βb2C > βb2B is satisfied. In other words, the wing 1 is the inner edge 7 In the outer portion 1b, the cross-sections 1A, 1B, and 1C of the same wing 1 are configured to extend in at least two (three in the illustrated example) directions. In the illustrated example, the cross-sections 1A, 1B, and 1C all extend in different directions.

[0026] Figure 8A illustrates the manufacturing method of integrally molded wings 1 and hub 2, showing the molding of wings 1 and hub 2 using molds 10 and 11. Figure 8B illustrates the manufacturing method of integrally molded wings 1 and hub 2, showing the removal of molds 10 and 11. Mold 10 molds part 1a of wings 1, and mold 11 molds part 1b of wings 1. The boundary between molds 10 and 11 is the inner edge of the shroud 3. 7The wings are positioned inward from the outer edges of the hub 2 and shroud 3, and do not protrude outside the hub 2 and shroud 3. Even in this case, the wing 1 having the structure of the present disclosure allows the hub 2 and the wing 1 to be integrally molded using molds 10 and 11.

[0027] Although not shown in Figures 8A and 8B, another mold (not shown) for molding the hub 2 is positioned above molds 10 and 11. Therefore, the wing 1 and hub 2 are integrally molded between this other mold and molds 10 and 11.

[0028] As explained with reference to Figure 7 above, part 1a has overlapping and coincident cross-sections 1A, 1B, and 1C. Therefore, after forming part 1a by arranging the mold 10 as shown in Figure 8A, part 1a of the wing 1 can be formed by removing it, for example in the direction of the rotation axis L0 (Figure 1) away from the hub 2, as shown by the black arrow in Figure 8B.

[0029] On the other hand, in portion 1b, the exit angles βb2A, βb2B, and βb2C with respect to the tangent to the shroud 3 decrease asymptotically from the hub 2 side towards the shroud 3 side. Therefore, as shown in Figure 8A, portion 1a is molded using a different mold 11 than the mold 10 used to mold portion 1a. After molding, as shown in Figure 8B, portion 1b of the blade 1 can be molded by, for example, removing it in the direction outward from the hub 2. The outward direction here refers to the direction outward from the hub 2 in the extension direction of portion 1b, as indicated by the arrow Y in Figure 7. If portion 1b includes a curved surface, it is the tangential direction of that curved surface. As shown in Figures 8A and 8B, by using molds 10 and 11, the blade 1 and the hub 2 can be molded as a single unit, and the manufacturing cost of the centrifugal fan 100 and the indoor unit 300 (both in Figure 1) can be reduced.

[0030] The centrifugal fan 100 and indoor unit 300 (Figure 1) having the above structure can achieve both a reduction in pressure loss and noise, and the integral molding of the blades 1 and hub 2.

[0031] Figure 9 is an explanatory diagram of the variables defining the shape of the trailing edge TE of the wing 1 in another embodiment. The angle θs (first angle) is the skew angle as the angle between the line L2 passing through intersection A and inflection point C and the line L3 passing through intersection A and parallel to the rotation axis L0 (Figure 1) of the impeller 101. The angle θs+ (second angle) is the additional skew angle as the angle between the line L2 and the line L4 passing through intersection B and inflection point C. Both angles θs and θs+ are greater than 0° and less than 90°. The length Zs is the length (shortest distance) between the hub 2 and inflection point C.

[0032] Figure 10A is a diagram illustrating the quantitative effect of the angle θs calculated by computational fluid dynamics analysis in another embodiment, and is a graph showing the ratio of shaft powers. Figure 10B is a diagram illustrating the quantitative effect of the angle θs calculated by computational fluid dynamics analysis in another embodiment, and is a graph showing the difference in noise. The computational fluid dynamics analysis calculation model is a centrifugal fan 100 (Figure 1) shown in Figures 3 and 4 mounted on an indoor unit 300 (Figure 1). The outer diameter D2 (Figure 7) of the impeller 101 is 450 mm, and the indoor unit 300 is a commonly used four-way indoor unit (an example of an indoor unit that blows in multiple directions).

[0033] However, if the outer diameter D2 is 500 mm or less, it is thought that the same results as in Figure 10 will be shown even if the outer diameter D2 is not 450 mm. Also, the centrifugal fan 100 changes the direction of gas flow by almost a right angle or more. Therefore, the centrifugal fan 100 is prone to increased pressure loss and high noise, while the parts of the structure equipped with the centrifugal fan 100 (e.g., indoor unit 300) other than the centrifugal fan 100 are usually not affected by pressure loss and noise. For this reason, it is thought that the results shown in Figures 10A and 10B can be similarly applied when used in indoor units other than four-way units.

[0034] In the embodiments shown in Figures 10A and 10B, only the angle θs is changed, while the other shapes and parameters remain the same. Note that in this calculation, the angle θs+ is 35°, and the ratio of length Zs to outer diameter D2 (the ratio Zs / D2 described later) is 19%. The driving force and noise are calculated from the change in rotational speed (decrease or increase) for the same airflow using the following equations 1 and 2. The vertical axis of each graph in Figures 10A and 10B is shown as a ratio or difference with the conventional centrifugal fan described above.

[0035] (Formula 1) The ratio of shaft power ΔL = (shaft power of this disclosure obtained from each calculation result / shaft power calculated for a conventional centrifugal fan) × (rotational speed of this disclosure obtained from each calculation result / rotational speed calculated for a conventional centrifugal fan) 3 (Formula 2) Noise difference ΔLA = 60 × log(rotational speed obtained from each calculation result in this disclosure / rotational speed calculated for a conventional centrifugal fan)

[0036] As shown in Figure 10A, if the angle θs is 42° or less, the ratio ΔL can be reduced to 100% or less, confirming that it requires less driving force than conventional centrifugal fans, i.e., high efficiency. Also, as shown in Figure 10B, if the angle θs is 42° or less, the difference ΔLA can be reduced to 0 dB or less, confirming that it is quieter than conventional centrifugal fans. Therefore, the centrifugal fan 100 is equipped with an impeller 101 having an outer diameter D2 of 450 mm to 500 mm, and by setting the angle θs to 42° or less, high efficiency and low noise can be achieved.

[0037] In particular, as shown in Figure 10A, it can be confirmed that when the angle θs is between 27° and 38°, the ratio ΔL can be made smaller, and the driving force can be made smaller. Also, as shown in Figure 10B, it can be confirmed that when the angle θs is between 27° and 35°, the difference ΔLA can be made smaller, and noise can be reduced. Within these ranges, setting the angle θs to between 30° and 35° allows for particularly high efficiency and particularly low noise, while setting the angle θs to 33° allows for the highest efficiency and the lowest noise.

[0038] Figure 11A is a graph illustrating the quantitative effect of angle θs+ calculated by computational fluid dynamics in another embodiment, showing the ratio of shaft powers. Figure 11B is a graph illustrating the quantitative effect of angle θs+ calculated by computational fluid dynamics in another embodiment, showing the difference in noise. The calculation model is the same as in the embodiments shown in Figures 10A and 10B above. In the embodiments shown in Figures 11A and 11B, only the angle θs+ is changed, while the other shapes and parameters are the same. The angle θs is 42° (ratio ΔL is 100%, difference ΔLA is 0dB), and the ratio of length Zs to outer diameter D2 (ratio Zs / D2 described later) is 19%. The calculation method for the vertical axis is the same as in the embodiments shown in Figures 10A and 10B.

[0039] As shown in Figure 11A, if the angle θs+ is 9° or greater, the ratio ΔL can be reduced to 100% or less, confirming that the driving force is smaller than that of conventional centrifugal fans, i.e., that it is highly efficient. Furthermore, as shown in Figure 11B, if the angle θs+ is 10° or greater, the difference ΔLA can be reduced to 0dB or less, confirming that it is quieter than conventional centrifugal fans. Therefore, the centrifugal fan 100 is equipped with an impeller 101 having an outer diameter D2 of 450mm to 500mm, and by setting the angle θs+ to 10° or greater, high efficiency and low noise can be achieved.

[0040] In particular, as shown in Figure 11A, it can be confirmed that if the angle θs+ is 42° or less, the ratio ΔL can be made smaller, and the driving force can be made smaller. In this case, the lower limit of the angle θs+ is, for example, 32°. Also, as shown in Figure 11B, it can be confirmed that if the angle θs+ is 42° or less, the difference ΔLA can be made smaller, and noise can be reduced. In this case, the lower limit of the angle θs+ is, for example, 30°. Therefore, by setting the angle θs+ to 32° or more and 42° or less, particularly high efficiency and particularly low noise can be achieved.

[0041] Figure 12A is a diagram illustrating the quantitative effect of the ratio of length Zs to outer diameter D2 calculated by computational fluid analysis in another embodiment, and is a graph showing the ratio of shaft power. Figure 12B is a diagram illustrating the quantitative effect of the ratio of length Zs to outer diameter D2 calculated by computational fluid analysis in another embodiment, and is a graph showing the difference in noise. The calculation model is the same as in the embodiments shown in Figures 10A and 10B above. In the embodiment shown in Figure 12, only the ratio of length Zs (Figure 9) to outer diameter D2 (Figure 7) is changed, and the other shapes and parameters are the same. The ratio here is the value obtained by dividing length Zs by outer diameter D2 (ratio Zs / D2). The embodiments shown in Figures 12A and 12B examine the preferred height position of the inflection point C between the hub 2 and the shroud 3 with respect to the outer diameter D2 of the impeller 101. The angle θs is 42° (ratio ΔL is 100%, difference ΔLA is 0dB), and the angle θs+ is 35°. The calculation method for the vertical axis is the same as in the embodiments shown in Figures 10 and 11.

[0042] As shown in Figure 12A, if the ratio Zs / D2 on the horizontal axis is between 18.8 and 22.6, the ratio ΔL can be reduced to 100% or less, confirming that it requires less driving force than conventional centrifugal fans, i.e., high efficiency. Furthermore, as shown in Figure 12B, if the ratio Zs / D2 is between 19.5 and 22.3, the difference ΔLA can be reduced to 0 dB or less, confirming that it is quieter than conventional centrifugal fans. Therefore, the centrifugal fan 100 is equipped with an impeller 101 having an outer diameter D2 of 450 mm to 500 mm, and with a ratio Zs / D2 of 19.5 to 22.3, achieving both high efficiency and low noise.

[0043] In particular, as shown in Figure 12A, it can be confirmed that if the ratio Zs / D2 is between 19.7 and 21.5, the ratio ΔL can be made smaller, and the driving force can be made smaller. Also, as shown in Figure 12B, it can be confirmed that if the ratio Zs / D2 is between 20.2 and 21.6, the difference ΔLA can be made smaller, and noise can be reduced. Of these ranges, setting the ratio Zs / D2 to between 20.2 and 21.5 results in particularly high efficiency and particularly low noise.

[0044] According to the centrifugal fan 100 and indoor unit 300 of this disclosure described above, the inner edge of the shroud 3 7 In the inner wing 1, the cross-sectional shapes at two predetermined height positions overlap and coincide, creating a two-dimensional shape. By making the exit angle of the wing 1 asymptotically smaller from the hub 2 side to the shroud 3 side, the hub 2 and the wing 1 can be integrally molded. This reduces manufacturing costs. Furthermore, by making the shape of the trailing edge TE between the shroud 3 and the inflection point C the shape described above, backflow at the wing 1 exit can be suppressed. This makes it possible to equalize the gas velocity distribution at the wing 1 exit, thereby increasing the efficiency and reducing the noise of the air conditioner 400. [Explanation of Symbols]

[0045] 1 wing 10 molds 100 centrifugal fan 101 Impeller 11 molds 1A cross section 1a part 1B cross section 1b part 1C cross section 2 hubs 200 cabinets 3 Shroud 300 indoor unit 31 Inlet 400 Air conditioner 41 Inlet 6 Air outlet 61 Exit 7 Common-law marriage A intersection (second intersection) B Intersection (1st intersection) C inflection point PS pressure surface RS ceiling surface S flow SS suction side TE trailing edge Zs length β2A angle β2B angle β2C angle βb2A Exit angle βb2B Exit Angle βb2C exit angle ΔL ratio ΔLA difference θs Angle (First Angle) θs + (second angle)

Claims

1. Hub and, A shroud equipped with a gas intake, The impeller comprises a plurality of wings positioned between the hub and the shroud, The aforementioned wing is Inward from the edge of the intake port, the cross-sectional shapes of the same blade are configured to overlap and coincide at at least two predetermined height positions between the hub side and the shroud side, The exit angle is such that it decreases from the hub side toward the shroud side. Of the predetermined wings, the first intersection point between the trailing edge opposite to the direction of rotation of the impeller and the shroud is positioned on the opposite side of the rotation than the second intersection point between the trailing edge and the hub. The inflection point located on the trailing edge between the first and second intersections is located on the rotational side of the straight line passing through the first and second intersections. The second intersection point is located on the rotational side of the inflection point. A centrifugal fan characterized by the following features.

2. The impeller has an outer diameter of 450 mm or more and 500 mm or less. The first angle formed by the line passing through the second intersection and the inflection point and the line passing through the second intersection and parallel to the rotation axis of the impeller is 42° or less. The centrifugal fan according to feature 1.

3. The first angle is between 30° and 35°. The centrifugal fan according to feature 2.

4. The impeller has an outer diameter of 450 mm or more and 500 mm or less. The second angle formed by the line passing through the second intersection and the inflection point and the line passing through the first intersection and the inflection point is 10° or more. The centrifugal fan according to feature 1.

5. The aforementioned second angle is between 32° and 42°. The centrifugal fan according to feature 4.

6. The impeller has an outer diameter of 450 mm or more and 500 mm or less. The value obtained by dividing the length between the hub and the inflection point by the outer diameter of the impeller is 19.5 or more and 22.3 or less. The centrifugal fan according to feature 1.

7. The hub and the wing are integrally molded. The centrifugal fan according to feature 1.

8. The blade is configured such that, outside the edge of the intake port, the cross-section of the same blade extends in at least two directions. The centrifugal fan according to feature 1.

9. It is equipped with an indoor unit that has a centrifugal fan that blows out air when driven, The aforementioned centrifugal fan is Hub and, A shroud equipped with a gas intake, The impeller comprises a plurality of wings positioned between the hub and the shroud, The aforementioned wing is Inward from the edge of the intake port, the cross-sectional shapes of the same blade are configured to overlap and coincide at at least two predetermined height positions between the hub side and the shroud side, The exit angle is such that it decreases from the hub side toward the shroud side. Of the predetermined wings, the first intersection point between the trailing edge opposite to the direction of rotation of the impeller and the shroud is positioned on the opposite side of the rotation than the second intersection point between the trailing edge and the hub. The inflection point located on the trailing edge between the first and second intersections is located on the rotational side of the straight line passing through the first and second intersections. The second intersection point is located on the rotational side of the inflection point. An air conditioner characterized by the following features.

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