WO2023242950A1

WO2023242950A1 - Propeller fan and axial blower

Info

Publication number: WO2023242950A1
Application number: PCT/JP2022/023795
Authority: WO
Inventors: 俊勝新井; 一樹蓮池
Original assignee: 三菱電機株式会社
Priority date: 2022-06-14
Filing date: 2022-06-14
Publication date: 2023-12-21

Abstract

The outer peripheral part of a rotary blade (1) has a shape that is bent toward the upstream side of an airflow. A protrusion (20) extending parallel to a blade trailing edge (1b) of the rotary blade (1) is provided on a negative-pressure surface (1f) side of the blade trailing edge (1b). The protrusion (20) has a first inclined part (20a) that gradually increases in height from a blade leading edge side toward the apex of the protrusion (20), and a second inclined part (20b) that gradually decreases in height from the apex of the protrusion (20) toward the blade trailing edge (1b). A first angle, which is the angle of the first inclined part (20a), is steeper than a second angle, which is the angle of the second inclined part (20b).

Description

Propeller fans and axial blowers

The present disclosure relates to a propeller fan and an axial blower used in ventilation fans, air conditioners, etc.

The rotor blades of the propeller fan of an axial blower have been advanced in the direction of rotation and tilted toward the upstream side of the airflow in order to reduce noise. In recent years, in order to further reduce noise, it has been proposed to bend the outer circumferential side of the rotor blade toward the upstream side of the airflow to reduce interference caused by blade tip vortices generated at the outer circumference of the blade.

Additionally, a separated vortex is formed near the leading edge of the blade, and airflow in a turbulent boundary layer is generated on the suction surface side of the rotor blade. The larger the separation vortex generated near the leading edge of the blade, the larger the trailing vortex generated behind the trailing edge of the blade as the airflow on the suction surface side flows toward the trailing edge of the blade while being turbulent. In an axial blower, noise is generated due to interference between blade tip vortices, separation vortices, and blade trailing vortices with adjacent rotary blades, bell mouths, and the like. The noise characteristics deteriorate as the blade tip vortices, separation vortices, and trailing vortices become larger, and as the airflow turbulence generated on the suction surface increases.

In Patent Document 1, a substantially triangular protrusion is provided on the rear edge of the rotational direction of the suction side of the blade, which extends approximately in the direction in which the blade extends, to reduce noise caused by airflow on the suction side. It's suppressed.

Japanese Patent Application Publication No. 2013-19335

In Patent Document 1, the approximately triangular protrusion has a larger inclination angle on the leading edge side of the blade than on the trailing edge side of the blade. For this reason, the blade trailing vortex generated behind the blade trailing edge cannot be efficiently reduced, and the noise reduction effect is small.

The present disclosure has been made in view of the above, and aims to provide a propeller fan that further reduces noise generated by a trailing vortex of the blade generated behind the trailing edge of the blade.

In order to solve the above-mentioned problems and achieve the objectives, a propeller fan according to the present disclosure includes a rotatably driven boss part, and a plurality of rotary blades that are radially attached to the boss part and generate airflow in the direction of the rotation axis. , is provided. The outer peripheral portion of the rotor blade has a shape that is bent toward the upstream side of the airflow. A protrusion extending parallel to the blade trailing edge is provided on the suction surface side of the blade trailing edge of the rotary blade. The protrusion includes a first inclined portion whose height gradually increases from the leading edge of the wing toward the apex of the protrusion, and a first slope whose height gradually decreases from the apex of the protrusion toward the trailing edge of the wing. a second slope, and the first angle, which is the angle of the first slope, is steeper than the second angle, which is the angle of the second slope.

According to the propeller fan of the present disclosure, it is possible to further reduce the noise generated by the trailing vortex of the blade generated behind the trailing edge of the blade.

A perspective view showing the configuration of an axial blower according to an embodiment. A perspective view showing the configuration of a propeller fan according to an embodiment. A perspective view showing the generation of a blade tip vortex in a rotor blade of a propeller fan according to an embodiment. A plan view showing a rotor blade of a propeller fan according to an embodiment. A partial cross-sectional view of the propeller fan according to the embodiment taken along the radial direction. A perspective view showing a rotor blade of a propeller fan according to an embodiment. A cross-sectional developed view of the inner peripheral edge of a blade in a propeller fan according to an embodiment A cross-sectional developed view of the outer peripheral edge of a blade in a propeller fan according to an embodiment A cross-sectional developed view of the intermediate portion between the inner peripheral edge of the blade and the outer peripheral edge of the blade in the propeller fan according to the embodiment. A partial cross-sectional developed view showing a protrusion of a rotor blade of a propeller fan according to an embodiment. An enlarged cross-sectional development view showing an enlarged protrusion of the rotor blade of the propeller fan according to the embodiment. A diagram showing changes in the slope of the tangent to the negative pressure surface of the rotor blade of the propeller fan according to the embodiment. A cross-sectional development diagram showing the trailing vortices of the blade that occur in a comparative example without protrusions. A cross-sectional developed view showing a trailing vortex generated in a rotor blade of a propeller fan according to an embodiment having a protrusion. A diagram showing the relationship between the height of the protrusion of the blade of the propeller fan according to the embodiment and specific noise reduction. A diagram showing the relationship between the distance of the protrusion to the trailing edge of the blade of the propeller fan according to the embodiment and the specific noise reduction rate. A plan view showing a modified example of the propeller fan according to the embodiment. A plan view showing another modification of the propeller fan according to the embodiment. A plan view showing a propeller fan according to an embodiment. An enlarged cross-sectional developed view of the propeller fan according to the embodiment shown in FIG. 11 rotated so that the Z-axis direction is the vertical direction.

Below, a propeller fan and an axial blower according to an embodiment of the present disclosure will be described in detail based on the drawings.

Embodiment.
FIG. 1 is a perspective view showing the configuration of an axial blower 100 according to an embodiment. The axial blower 100 includes a propeller fan 10, a main body 21, a bell mouth 30 as a wind tunnel, a motor (not shown), and a motor fixing member (not shown). A propeller fan 10 and a motor are arranged inside the bell mouth 30. The propeller fan 10 has a cylindrical boss portion 2 and a plurality of rotary blades 1 having the same three-dimensional shape. The boss portion 2 is rotationally driven by a motor, and rotates in the direction of arrow W around a rotating shaft 3. Each rotor blade 1 is attached radially to the outer periphery of the boss portion 2. As the propeller fan 10 rotates, the rotor blade 1 generates an airflow in the direction of arrow A. The bell mouth 30 has a diameter that is gradually reduced from the large-diameter suction port side toward the blowout port side.

FIG. 2 is a perspective view showing the configuration of the propeller fan 10 according to the embodiment. FIG. 3 is a perspective view showing the generation of a blade tip vortex in the rotor blade 1 of the propeller fan 10 according to the embodiment. FIG. 4 is a plan view showing the rotor blade 1 of the propeller fan 10 according to the embodiment. FIG. 5 is a partial cross-sectional view of the propeller fan 10 according to the embodiment taken along the radial direction. The rotary blade 1 has a leading edge 1a, which is the front end in the rotational direction indicated by arrow W, a trailing blade edge 1b, which is the rear end in the rotational direction indicated by arrow W, and an inner circumference ( The blade has an inner peripheral edge portion 1c which is an end portion on the boss portion 2 side) and an outer peripheral blade portion 1d which is an end portion on the outer peripheral portion side. In FIG. 1, five rotary blades 1 are shown, and in FIG. 2, three rotary blades 1 are shown. As the number of rotary blades 1, other numbers may be adopted.

When an airflow in the direction of arrow A is generated by the rotation of the propeller fan 10, the flow in the inner peripheral portion advects in the centrifugal direction, creating a pressure difference between the pressure surface 1g and the negative pressure surface 1f of the rotor blade 1. As a result, a leakage vortex is generated in the outer peripheral portion of the rotary blade 1 from the pressure surface 1g where the pressure is high to the negative pressure surface 1f where the pressure is low, as shown in FIG. This is called a wing tip vortex 5. This blade tip vortex 5 is a cause of noise generation due to interference between a separation vortex generated near the blade leading edge 1a and a blade trailing vortex generated behind the blade trailing edge 1b, which will be described later. Become. As shown in FIG. 5, with respect to the direction of the airflow indicated by arrow A, the blade surface on the upstream side becomes a negative pressure surface 1f with low pressure, and the blade surface on the downstream side becomes a pressure surface 1g with high pressure. FIG. 4 shows the blade chord, which connects the midpoints of the blade leading edge 1a and the blade trailing edge 1b at each radial position centering on the coordinate center O from the blade inner peripheral edge 1c to the blade outer peripheral edge 1d. A center line g is shown. 3 and 4, the Z-axis corresponding to the rotation axis 3, the X-axis and Y-axis that are two axes perpendicular to the Z-axis, and the coordinate center O of the X-axis, Y-axis, and Z-axis are shown. There is.

As shown in FIG. 5, the propeller fan 10 has a shape in which the outer circumferential portion is bent toward the upstream side of the airflow as indicated by arrow A in terms of the shape in the direction connecting the inner circumferential portion and the outer circumferential portion. This reduces the interference caused by the blade tip vortex 5 mentioned above. In FIG. 4, the inner periphery side is convex with respect to the airflow, and the outer periphery side is concave with respect to the airflow. Although the S-shape is not limited to this, the shape is not limited to this, and the outer periphery is bent toward the upstream side of the airflow. It is sufficient if it has the following.

FIG. 6 is a perspective view showing the rotor blade 1 of the propeller fan 10 according to the embodiment. FIG. 7 is a cross-sectional development view of the blade inner circumferential edge portion 1c of the propeller fan 10 according to the embodiment. FIG. 7 is a cross-sectional developed view of the propeller fan 10 cut along a cylindrical surface having a radius D1-D1' in FIG. 4 and expanded into a two-dimensional plane. FIG. 8 is a developed cross-sectional view of the blade outer peripheral edge portion 1d of the propeller fan 10 according to the embodiment. FIG. 8 is a cross-sectional developed view of the propeller fan 10 cut along a cylindrical surface having a radius D2-D2' in FIG. 4 and expanded into a two-dimensional plane. FIG. 9 is a cross-sectional developed view of an intermediate portion between the inner blade edge 1c and the outer blade edge 1d in the propeller fan 10 according to the embodiment. FIG. 9 is a cross-sectional exploded view of the propeller fan 10 cut along a cylindrical surface having a radius D3-D3' in FIG. 4 and expanded into a two-dimensional plane. FIG. 10 is a partially sectional exploded view showing the protrusion 20 of the rotor blade 1 of the propeller fan 10 according to the embodiment. FIG. 11 is an enlarged cross-sectional developed view showing the protrusion 20 of the rotor blade 1 of the propeller fan 10 according to the embodiment. FIG. 12 is a diagram showing a change in the slope of the tangent to the suction surface 1f of the rotor blade 1 of the propeller fan 10 according to the embodiment. FIG. 13 is a cross-sectional developed view showing the blade trailing vortex 14 and the like generated in a comparative example without the protrusion 20. FIG. 14 is a cross-sectional development view showing the blade trailing vortex 14 and the like generated in the rotor blade 1 of the propeller fan 10 according to the embodiment in which the protrusion 20 is provided.

As shown in FIGS. 7 to 9, the shape of the rotary blade 1 from the blade leading edge 1a to the blade trailing edge 1b is convex toward the upstream side as a whole. Therefore, near the blade trailing edge 1b, the rotary blade 1 is inclined toward the downstream side (negative side in the ZL direction) as it advances toward the blade trailing edge 1b. Further, the blade leading edge 1a is thicker than the blade trailing edge 1b. Further, as can be seen from FIGS. 7 to 9, the thickness of the rotary blade 1 gradually becomes thinner from the inner peripheral edge 1c of the blade toward the outer peripheral edge 1d. Further, the blade leading edge portion 1a has an R shape to prevent separation of airflow. Further, the blade trailing edge portion 1b also has a rounded shape to prevent separation of airflow. In the blade trailing edge portion 1b, the curvature of the R shape on the side of the suction surface 1f is larger than the curvature of the R shape on the side of the pressure surface 1g.

As shown in FIGS. 2, 3, 4, 6, and 9, the blade trailing vortex 14 shown in FIG. A protrusion 20 is provided for suppression. The protrusion 20 extends parallel to the wing trailing edge 1b. It is desirable that the protrusion 20 is continuously provided over one-third or more of the length of the blade trailing edge 1b. As shown in FIG. 4, the protrusion 20 is preferably provided continuously from a radial position Rrib near the inner blade edge 1c to a radial position Rrib' near the outer blade edge 1d.

As shown in FIGS. 10 and 11, the projection 20 increases in height from the end of the projection on the wing leading edge 1a side (point PB in FIG. 11) toward the apex of the projection 20 (point PD in FIG. 11). The first inclined portion 20a gradually increases in height, and the height increases from the apex of the protrusion 20 (point PD in FIG. 11) to the end of the protrusion on the wing trailing edge 1b side (point PF in FIG. 11). It has a second slope portion 20b that gradually becomes lower. The first angle, which is the angle of the first inclined portion 20a, is steeper than the second angle, which is the angle of the second inclined portion 20b. In other words, the projection 20 has a shape in which the inclination θ2 with respect to the blade surface on the downstream side (the blade trailing edge 1b side) is larger than the inclination θ1 with respect to the blade surface on the upstream side (the blade leading edge 1a side). has. Note that it is preferable that the protrusions 20 have the same cross-sectional shape in the direction along the blade trailing edge 1b.

As shown in FIG. 9, the chord length L is the longest distance between the straight line LW1 and the straight line LW2 when the blade is sandwiched between two parallel straight lines LW1 and LW2 in the cylindrical cross section of the rotary blade 1. It is defined as the length. The direction parallel to the blade chord length L and going from the blade leading edge 1a to the blade trailing edge 1b is defined as the XL direction, which is perpendicular to the blade chord length L, parallel to the straight line LW1 and the straight line LW2, and runs from the downstream side to the upstream side. The heading direction is defined as the ZL direction.

In FIG. 11, the curved surface connecting point PA and point PB is the curved surface on the wing leading edge 1a side of the wing surface adjacent to the protrusion 20. The arc connecting portion connecting point PB and point PC is a portion connecting the portion of the projection portion 20 on the blade leading edge portion 1a side and the blade surface. The curved surface connecting the point PC and the apex point PD is the curved surface of the protrusion 20 on the wing leading edge portion 1a side. The curved surface connecting point PD and point PE is the curved surface of the protrusion 20 on the wing trailing edge 1b side. The arc connecting portion connecting point PE and point PF is a portion connecting the portion of the projection portion 20 on the blade trailing edge portion 1b side and the blade surface. The curved surface connecting point PF and point PG is a curved surface on the blade trailing edge 1b side of the blade surface adjacent to the protrusion 20. Point PG is a point included in the trailing edge portion 1b of the wing.

The curved surface connecting points PA and PB and the curved surface connecting points PF and PG are part of the suction surface 1f, which is the upstream surface of the rotor blade 1. The protrusion 20 is formed by a curved surface connecting points PC and PD and a curved surface connecting points PD and PE. The curved surface connecting points PA and PB and the curved surface connecting points PF and PG are curved surfaces that are convex toward the upstream side. The curved surface connecting point PC and point PD and the curved surface connecting point PD and point PE are curved surfaces convex to the upstream side, and the curved surface connecting point PA and point PB and the curved surface connecting point PF and point PG. The curvature is greater than the curved surface. That is, the protrusion 20 is a curved surface with a larger curvature than the suction surface 1f of the rotor blade 1.

The negative pressure surface 1f and the protrusion 20 are smoothly connected in an arc shape by an arc connection part connecting points PB and PC and an arc connection part connecting points PE and PF. The curved surface that connects points PA and PB and the curved surface that connects points PC and PD are continuous and smooth so that the slopes at the connection points are equal due to the arc connection section that connects point PB and point PC. connected to. The arc connecting portion connecting point PB and point PC is convex toward the downstream side. The curved surface that connects points PD and PE and the curved surface that connects points PF and PG are continuously smoothed by the arc connection connecting points PE and PF so that the slopes at the connection are equal. connected to. The arc connecting portion connecting point PE and point PF is convex toward the downstream side. The curved surface connecting point PD, which is the curved surface on the wing trailing edge 1b side of the protrusion 20, and point PE is, from the curved surface connecting the point PC and point PD, which is the curved surface on the wing leading edge 1a side of the protrusion 20, It is formed with a small curvature.

FIG. 12 shows a change in the slope dZL/dXL of the tangent to the suction surface 1f of the rotor blade 1 of the propeller fan 10 in the XL direction. As shown in FIGS. 11 and 12, the curved surface connecting point PA and point PB is a curved surface that is convex toward the upstream side, and the arc connecting portion connecting point PB and point PC is a curved surface that is convex toward the downstream side. , the slope dZL/dXL of the tangent line becomes maximum at point PB between point PA and point PC. Straight line LPB is a straight line that touches the blade surface at point PB. The inclination of the blade surface portion adjacent to the protrusion 20 on the blade leading edge 1a side is defined by a straight line LPB. That is, the slope of the blade surface portion adjacent to the protrusion 20 on the wing leading edge 1a side is closer to the blade leading edge 1a than the point PD, which is the apex of the protrusion 20, and the slope of the tangent is on the downstream side. This is the inclination at point PB, which is the maximum inclination position.

The curved surface connecting points PC and PD constituting the protrusion 20 is a curved surface that is convex toward the upstream side, and has a shape that protrudes toward the upstream side toward the blade trailing edge 1b. Since the arc connecting portion connecting point PB and point PC is a curved surface convex toward the downstream side, the slope of the tangent of the protrusion 20 on the blade leading edge portion 1a side with respect to the XL axis becomes maximum at point PC. Straight line LPC is a straight line that touches the blade surface at point PC. The inclination of the projection 20 on the wing leading edge 1a side is defined by a straight line LPC. In other words, the inclination of the protrusion 20 on the wing leading edge 1a side is a point on the wing leading edge 1a side from the point PD, which is the apex of the protrusion 20, at a point where the inclination of the tangent line is maximum upstream. This is the tilt of the PC.

The curved surface connecting point PD and point PE that constitutes the protrusion 20 is a curved surface that is convex toward the upstream side, and has a shape that protrudes toward the upstream side as it approaches the blade leading edge portion 1a side. Since the arcuate connection connecting point PE and point PF is a curved surface convex toward the downstream side, the slope of the tangent of the protrusion 20 on the blade trailing edge 1b side with respect to the XL axis becomes maximum at point PE. Straight line LPE is a straight line that touches the blade surface at point PE. The slope of the protrusion 20 on the blade trailing edge 1b side is defined by a straight line LPE. That is, the inclination of the protrusion 20 on the blade trailing edge 1b side is at a point PE near the connection between the protrusion 20 and the blade trailing edge 1b, where the inclination of the tangent line is maximum downstream. This is the slope at . A straight line passing through point PE and parallel to straight line LPB is defined as straight line LPB2.

The inclination θ1 of the protrusion 20 on the wing leading edge 1a side is defined by the angle between the straight line LPB and the straight line LPC. The inclination θ2 of the projection 20 on the blade trailing edge 1b side is defined by the angle between the straight line LPB2 and the straight line LPE.

The height tr of the protrusion 20 and the plate thickness tk of the rotor blade 1 are defined as follows. The apex of the protrusion 20 in the ZL direction is defined as a point PD. The height tr of the protrusion 20 and the plate thickness tk of the wing portion are defined by the height in the ZL direction at the position of this point PD. Let the straight line LPB be the virtual wing surface. Point Pt is a point on a straight line that passes through the vertex indicated by point PD of protrusion 20 and extends in the ZL direction, and intersects with straight line LPB. The height from point Pt to point PD, which is the apex of protrusion 20, is defined as height tr of protrusion 20. Point Pk is a point that passes through the apex of the protrusion 20 indicated by point PD and intersects with the blade surface of the pressure surface 1g on a straight line extending in the ZL direction. Let the width from point Pt to point Pk be the plate thickness tk of the wing section.

The width tw of the protrusion 20 and the distance B of the protrusion 20 from the wing trailing edge 1b are defined as follows. The width tw of the protrusion 20 is defined as the distance from point PC, which is the front edge of the protrusion 20, to point PE, which is the rear edge of the protrusion 20, in the XL direction. In the XL direction, the distance from point PE, which is the trailing edge of the projection 20, to point PG on the blade trailing edge 1b of the rotor 1 is defined as distance B of the projection 20 from the blade trailing edge 1b.

As shown in FIGS. 13 and 14, since airflow from the front and airflow from the sides flow into the leading edge 1a of the blade, a separation vortex 31 is formed near the leading edge 1a. Ru. An airflow 32 in a turbulent boundary layer is generated on the suction surface 1f side of the rotary blade 1. The larger the separation vortex 31 generated near the blade leading edge 1a, the larger the blade trailing vortex 14 generated behind the blade trailing edge 1b as the airflow 32 flows toward the blade trailing edge 1b while being turbulent. Become. As shown in FIG. 13, if there is no protrusion 20, the flow of airflow 32 toward the trailing edge 1b of the blade cannot be obstructed, and a relatively large Karman vortex forms behind the trailing edge 1b of the blade. A wake vortex 14 is generated. On the other hand, as shown in FIG. 14, when the rotor blade 1 is provided with the protrusion 20, it is possible to prevent the air flow 32 from flowing toward the blade trailing edge 1b, and airflow occurs behind the blade trailing edge 1b. The blade trailing vortex 14 can be made smaller.

In the embodiment, the slope θ2 of the protrusion 20 on the blade trailing edge 1b side is larger than the slope θ1 of the protrusion 20 on the blade leading edge 1a side. In other words, the first angle, which is the angle of the first inclined portion 20a, is made steeper than the second angle, which is the angle of the second inclined portion 20b. As a result, compared to the protrusion in Patent Document 1, it is possible to prevent the airflow 32 from flowing toward the blade trailing edge 1b, and to further reduce the blade trailing vortex 14 generated behind the blade trailing edge 1b. can. Therefore, it is possible to further reduce noise.

That is, in Patent Document 1, when the flow point changes and the angle of the flow flowing into the rotor blade 1 changes, separation may become excessive due to the protruding shape and noise may worsen. In addition, dust and the like tend to accumulate on the apex of the protrusion, and when dust accumulates, the shape of the protrusion changes, which may change the flow, resulting in excessive separation and worsening of noise. In contrast, the protrusion 20 of the embodiment has a shape that is curved on the upstream side of the flow and sharply pointed on the downstream side, and the thicker apex portion is closer to the upstream side of the flow. This prevents the flow from separating excessively and stabilizes the flow. Therefore, even if the flow point changes and the flow angle changes, the effect is small and the effect of the protrusion 20 can be stably obtained. Furthermore, since the shape of the protrusion changes continuously, there are no corners and it becomes difficult for dust etc. to accumulate, so the shape of the protrusion is difficult to change and the effect of the protrusion 20 can be stably obtained.

Furthermore, it is desirable that θ1 be larger than 90°. By making θ1 larger than 90°, the turbulence caused by the blade trailing vortex 14 can be weakened. That is, it is desirable that the angle of the protrusion 20 satisfies the relationship 90°<θ1<θ2.

FIG. 15 is a diagram showing the relationship between the height of the protruding portion 20 of the blade portion of the propeller fan 10 and the specific noise reduction according to the embodiment. In FIG. 15, the horizontal axis represents the ratio of the height tr of the protrusion 20 to the plate thickness tk, and the vertical axis represents the specific noise reduction ratio ΔK _T. As shown in FIG. 15, there is an optimal point between the height tr of the protrusion 20 and the specific noise reduction rate ΔK _T. It can be seen that in order to obtain an effective noise reduction effect, in the range of 0.04≦tr/tk≦0.56, an effect of −1 (db) or more in specific noise can be obtained.

The specific noise _KT is a calculated value as shown below.
K _T = SPL _A -10Log (Q P _T ^2.5 )
Q is the air volume [m ³ /min], P _T is the total pressure [Pa], and SPL _A is the noise characteristic [dB] after A-characteristic correction.

The width tw of the protrusion 20 preferably satisfies a range from one time the height tr of the protrusion 20 to four times the height tr of the protrusion 20, as shown by the following formula.
1×tr≦tw≦4×tr

The shape of the protrusion 20 is a smooth curved shape that is high at the center and low at the periphery. For example, a parabola or a quadratic curve may be used as the curve shape.

FIG. 16 is a diagram showing the relationship between the distance of the protrusion 20 with respect to the blade trailing edge 1b of the propeller fan 10 and the specific noise reduction rate ΔK _T according to the embodiment. In FIG. 16, the horizontal axis represents the ratio of the distance B of the protrusion 20 from the blade trailing edge 1b to the blade chord length L, and the vertical axis represents the specific noise reduction ratio ΔK _T. As shown in FIG. 16, if the position of the protrusion 20 is too far away from the blade trailing edge 1b, the noise reduction effect will be small. It is desirable to provide the protrusion 20 in the range of ≦B/L≦0.08.

FIG. 17 is a plan view showing a modification of the propeller fan 10 according to the embodiment. FIG. 18 is a plan view showing another modification of the propeller fan 10 according to the embodiment. In FIG. 17, the protrusion 20 is provided from the center position in the radial direction to the outer peripheral side. In FIG. 18, the protrusion 20 is provided from the center position in the radial direction to the inner peripheral side.

According to the propeller fan 10 according to the embodiment, it is possible to achieve low noise with any pattern of the projections 20, and experiments have shown that an effect of -1.8 (db) in specific noise can be obtained. I was able to confirm that. Even when the protrusion 20 could not be arranged over the entire blade trailing edge 1b due to manufacturing reasons, certain effects were obtained. These series of evaluation results are the results of evaluating the rotor blade 1 having a diameter of 220 mm at a constant rotation speed of 1400/min. Note that the length of the protrusion 20 is preferably parallel to the blade trailing edge 1b and is 1/3 or more of the length of the blade trailing edge 1b.

Next, the shape related to the method of molding the propeller fan 10 will be explained. FIG. 19 is a plan view showing the propeller fan 10 according to the embodiment. As shown in FIGS. 1, 2, and 9, in the propeller fan 10 of the embodiment, when viewed from the direction of the rotating shaft 3 (Z-axis direction), the plurality of rotary blades 1 are arranged so that they do not overlap. , are evenly arranged in the circumferential direction around the rotating shaft 3. With this configuration, when resin molding the propeller fan 10, it is possible to form the propeller fan 10 using a mold that is divided into two parts vertically in the Z-axis direction.

Here, in the embodiment, the protrusion 20 is also shaped to be compatible with two-part molding. FIG. 20 is an enlarged sectional developed view of the propeller fan 10 according to the embodiment shown in FIG. 11, which is rotated so that the Z-axis direction is in the vertical direction. It is assumed that resin molding is performed using a mold that is divided into two parts in the vertical direction of FIG. 20, that is, in the positive direction and the negative direction of the Z axis. In order to make this molding possible, the cross section of the protrusion 20 on a cylindrical surface centered on the rotating shaft 3 extending in the Z-axis direction should have a shape that becomes wider from the upstream side to the downstream side. good. Specifically, as the slope of the straight line LPC advances from the downstream side (Z-axis negative side) to the upstream side (Z-axis positive side), it increases from the blade leading edge 1a side to the blade trailing edge 1b side. As the slope of the straight line LPE advances from the downstream side (Z-axis negative side) to the upstream side (Z-axis positive side), it slopes upward from the blade trailing edge 1b side to the blade leading edge 1a side. It may be a shape.

By adopting this shape, it becomes a shape that prevents undercuts during molding, and it becomes possible to use a mold consisting of a simple upper and lower mold configuration, and there is no large increase in cost for introduction. Moreover, by adopting this shape, there are no corners, which prevents dust from adhering, and even when there is no cleaning work, the noise reduction effect can be exerted for a long period of time.

The configurations shown in the embodiments described above are examples of the contents of the present disclosure, and can be combined with other known technologies, and the configurations can be modified without departing from the gist of the present disclosure. It is also possible to omit or change parts.

1 rotor blade, 1a blade leading edge, 1b blade trailing edge, 1c blade inner peripheral edge, 1d blade outer peripheral edge, 1f suction surface, 1g pressure surface, 2 boss, 3 rotating shaft, 5 blade tip vortex, 10 Propeller fan, 14 Blade wake vortex, 20 Projection, 20a First slope, 20b Second slope, 21 Main body, 30 Bell mouth, 31 Separation vortex, 32 Airflow, 100 Axial blower, g Chord center line, L: chord length, O: coordinate center.

Claims

A propeller fan comprising a rotationally driven boss part and a plurality of rotary blades that are radially attached to the boss part and generate airflow in the direction of a rotation axis,
The outer peripheral portion of the rotary blade has a shape bent toward the upstream side of the airflow,
A protrusion extending parallel to the blade trailing edge is provided on the suction side of the blade trailing edge of the rotary blade,
The protrusion includes a first inclined part whose height gradually increases from the leading edge of the wing toward the apex of the protrusion, and a first slope whose height gradually increases from the apex of the protrusion toward the trailing edge of the wing. and a second sloping part that gradually lowers, and the first angle that is the angle of the first sloping part is steeper than the second angle that is the angle of the second sloping part. propeller fan.
The propeller fan according to claim 1, wherein the first inclined part and the second inclined part are curved surfaces convex toward the upstream side.
The propeller fan according to claim 1 or 2, wherein a cross section of the protrusion on a cylindrical surface centering on the rotation axis has a shape that becomes wider from the upstream side to the downstream side.
When the height of the protrusion is tr and the thickness of the rotary blade is tk,
0.04≦tr/tk≦0.56
The propeller fan according to any one of claims 1 to 3, characterized in that:
The distance between the end of the projection on the blade trailing edge side and the blade trailing edge of the rotary blade is B, and the distance is the distance between the blade leading edge and the blade trailing edge of the rotary blade. Letting the chord length of the blade be L,
0.01≦B/L≦0.08
The propeller fan according to any one of claims 1 to 4, characterized in that:
6. The curved surface of the protrusion on the wing trailing edge side is formed to have a smaller curvature than the curved surface of the protrusion on the wing leading edge side. propeller fan.
The propeller according to any one of claims 1 to 6, wherein the length of the projection along the trailing edge of the blade is 1/3 or more of the length of the trailing edge of the blade. fan.
The propeller fan according to any one of claims 1 to 7,
a motor that rotationally drives the boss portion of the propeller fan;
a main body including a bell mouth disposed around the propeller fan;
An axial flow blower characterized by comprising: