EP4726213A1

EP4726213A1 - Impeller, blower, and air conditioner

Info

Publication number: EP4726213A1
Application number: EP23941462.6A
Authority: EP
Inventors: Kisho Hatakenaka; Ryutaro Asano; Miyu NAKANO
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2023-06-12
Filing date: 2023-06-12
Publication date: 2026-04-15
Also published as: WO2024257150A1; JPWO2024257150A1; JP7483171B1; CN121285700A

Abstract

In an impeller, where, in the case where imaginary cylinders concentric with a rotation axis are assumed, an imaginary cross-section of each of parts of each of blades that correspond to the imaginary cylinders is defined as a chordwise-direction cross-section; in the chordwise-direction cross-section, a straight line that connects the leading edge and the trailing edge is defined as a chord, and a central line of a cross-section of the blade is defined as a camber line; the distance between the chord and the camber line is defined as a camber height; on the camber line, a point equidistant from the leading edge and the trailing edge is defined as a camber midpoint; and a point at which the camber height is maximum is defined as a maximum extreme point, in the chordwise-direction cross-section close to the inner edge of the blade, the maximum extreme point is located closer to the trailing edge than to the camber midpoint and closer to an air suction side than to the chord, and the camber line has at least one inflection point between the leading edge and the maximum extreme point, and in the chordwise-direction cross-section close to the outer end of the blade, the maximum extreme point is located closer to the leading edge than to the camber midpoint and closer to the air suction side than to the chord.

Description

Technical Field

The present invention relates to an impeller, a fan, and an air-conditioning apparatus.

Background Art

As an existing impeller, an impeller including multiple blades arranged radially is present (see, for example, Patent Literature 1). In an impeller described in Patent Literature 1, blades each have a root having a midpoint R1 in a circumferential direction, an outer peripheral portion having a midpoint R2 in the circumferential direction, and a rotation center O. In the impeller of Patent Literature 1, the angle between a line that connects O and R1 and a line that connects O and R2 is 18 to 22 degrees, and a line P that connects R1 and R2 is inclined toward a suction side by an angle of 22 to 27 degrees relative to a plane perpendicular to the axis of rotation that passes through R1.
In the impeller of Patent Literature 1, each of the blades has an inflection point in its section in the circumferential direction. In the impeller of Patent Literature 1, the blade has a convex surface that has a convex shape on a discharge side in an area that extends to the inflection point from a leading edge of the blade in a rotation direction of the blade and a concave surface that has a concave shape on the discharge side in an area that extends from the inflection point to a trailing edge of the blade in the rotation direction of the blade. The impeller of Patent Literature 1 includes the blades each having the above convex and concave shapes over the entire length thereof from the root to the outer peripheral portion.

Citation List

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication JP Hei 9-068 200 A

Summary of Invention

Technical Problem

An impeller improves its efficiency by reducing occurrence of airflow separation on blade surfaces. The impeller of Patent Literature 1 including the blades having the above configuration and can thus reduce noise made by rotation of the blades during rotation of the impeller. However, since each of the blades of the impeller of Patent Literature 1 has a convex shape in an area adjacent to the leading edge and a concave shape in an area adjacent to the trailing edge, over its entire length from the root to the outer peripheral portion, airflow separation may occur due to the convex shape on an outer peripheral side of each blade where air flows faster than on an inner peripheral side of each blade, thus deteriorating the air-sending performance.
The present invention is applied to solve the above problem, and relates to an impeller that reduces occurrence of airflow separation and is improved in air-sending performance, a fan, and an air-conditioning apparatus.

Solution to Problem

An impeller according to an embodiment of the present invention includes a boss provided on a rotation axis and a plurality of blades provided on an outer circumference of the boss. The blades each have a leading edge that is an edge facing forward in a rotation direction of the plurality of blades, a trailing edge that is an edge facing rearward in the rotation direction, an outer end that is an outer peripheral edge, and an inner edge that is an inner peripheral edge.
Where, in the case where a plurality of imaginary cylinders concentric with the rotation axis are assumed, an imaginary cross-section of each of parts of each of the plurality of blades that correspond to the imaginary cylinders is defined as a chordwise-direction cross-section; in the chordwise-direction cross-section, a straight line that connects the leading edge and the trailing edge is defined as a chord, and a central line of a cross-section of the blade is defined as a camber line; in the chordwise-direction cross-section, a distance between the chord and the camber line in a direction perpendicular to the chord is defined as a camber height; on the camber line, a point equidistant from the leading edge and the trailing edge is defined as a camber midpoint; and on the camber line, a point at which the camber height is maximum is defined as a maximum extreme point, in the chordwise-direction cross-section closer to the inner edge than to the outer end of the blade, the maximum extreme point is located closer to the trailing edge than to the camber midpoint and closer to an air suction side than to the chord, and the camber line has at least one inflection point between the leading edge and the maximum extreme point, and in the chordwise-direction cross-section closer to the outer end than to the inner edge of the blade, the maximum extreme point is located closer to the leading edge than to the camber midpoint and closer to the air suction side than to the chord.
A fan according to another embodiment of the present invention includes a casing including a bell mouth and the impeller having the above configuration and accommodated in the casing. In the case where the casing has a length H_b in an axial direction along the rotation axis and a factor ε satisfies 0 < ε ≤ 0.5, the impeller is provided within a region that is located inward of an imaginary plane located on the air suction side and apart from the casing by a distance εH_b in the axial direction along the rotation axis and is located inward of an imaginary plane located on an air blowing side and apart from the casing by the distance εH_b in the axial direction along the rotation axis.
An air-conditioning apparatus according to still another embodiment of the present invention includes the impeller having the above configuration, and a heat exchanger that causes heat exchange to be performed between air supplied by the impeller and refrigerant flowing in the heat exchanger.

Advantageous Effects of the Invention

The impeller and the impellers included in the fan and the air-conditioning apparatus according to the embodiments of the present invention are configured as follows. In the chordwise-direction cross-section closer to the inner edge than to the outer end of each of the plurality of blades, the maximum extreme point is located closer to the trailing edge than the camber midpoint and closer to the air suction side than to the chord. The camber line has at least one inflection point between the leading edge and the maximum extreme point.
Furthermore, in the chordwise-direction cross-section closer to the outer end of the blade than to the inner edge thereof, the maximum extreme point is located closer to the leading edge than the camber midpoint and on the air suction side relative to the chord. By virtue of the above configuration, in the impeller, it is possible to cause airflow to move along the blades, whereby it is possible to reduce occurrence of airflow separation on part of an outer portion of the blade that is adjacent to the leading edge and thus improve the air-sending performance.

Brief Description of Drawings

FIG. 1 is a perspective view of a configuration of a fan including an impeller according to Embodiment 1.
FIG. 2 is a conceptual diagram illustrating a basic configuration of the impeller according to Embodiment 1, with the impeller projected on a plane perpendicular to the axis of rotation of the impeller.
FIG. 3 is a conceptual diagram of a section taken along line III-III in FIG. 2 as viewed in the direction indicated by an arrow.
FIG. 4 is a conceptual diagram of an example of a chordwise-direction cross-section of a blade of the impeller according to Embodiment 1.
FIG. 5 is a conceptual diagram illustrating a chord and a camber line of a chordwise-direction cross-section taken along line IV-IV in FIG. 2.
FIG. 6 is a conceptual diagram illustrating the chord and the camber line of a chordwise-direction cross-section taken along line V-V in FIG. 2.
FIG. 7 is a conceptual diagram illustrating the chord and the camber line of the chordwise-direction cross-section taken along line IV-IV in FIG. 2 to explain the operation of the impeller according to Embodiment 1 and airflow.
FIG. 8 is a conceptual diagram illustrating the chord and the camber line of the chordwise-direction cross-section taken along line V-V in FIG. 2 to explain the operation of the impeller according to Embodiment 1 and the airflow.
FIG. 9 is a conceptual diagram of an impeller according to Embodiment 2, which illustrates the chord and the camber line of the chordwise-direction cross-section taken along line IV-IV in FIG. 2.
FIG. 10 is a conceptual diagram of the impeller according to Embodiment 2, which illustrates the chord and the camber line of the chordwise-direction cross-section taken along line V-V in FIG. 2.
FIG. 11 is a graph indicating a relationship between the flow coefficient and the fan efficiency of the impeller according to Embodiment 2 and that of an impeller of the related art.
FIG. 12 is a graph indicating a relationship between the flow coefficient and the pressure coefficient of the impeller according to Embodiment 2 and that of an impeller of the related art.
FIG. 13 is a conceptual diagram of an impeller according to Embodiment 3, which illustrates illustrating the chord and the camber line of the chordwise-direction cross-section taken along line IV-IV in FIG. 2.
FIG. 14 is a conceptual diagram of the impeller according to Embodiment 3, which illustrates the chord and the camber line of the chordwise-direction cross-section taken along line V-V in FIG. 2.
FIG. 15 is a conceptual diagram of a fan according to Embodiment 4, which illustrates a section of the fan on a plane that is parallel to and passes through the axis of rotation of the fan illustrated in FIG. 1.
FIG. 16 is a perspective view of an air-conditioning apparatus according to Embodiment 5 illustrating the configuration of the apparatus.

Description of Embodiments

Impellers, a fan, and an air-conditioning apparatus according to embodiments will be described below with reference to the drawings. It should be noted that in figures including FIG. 1 that will be referred to below, the relationships, for example, in relative dimension and shape between components may differ from those of actual ones. Furthermore, in each of the figures, components that are the same as or equivalent to those in a previous figure or previous figures are denoted by the same reference signs. The same is true of the entire text of the specification.
In addition, in order that descriptions be more easily understood, terms indicating directions (for example, "up", "down", "right", "left", "front", and "back") will be used as appropriate; however, they are merely used as a matter of convenience for explanation, but do not intend to limit the arrangement or orientations of devices or components. Additionally, although the following figures illustrate shapes of components that are not chamfered, even if components are chamfered, it is possible to obtain the same advantages as in the case where the components are not chamfered. That is, for example, if the impellers, the fan, and the air-conditioning apparatus are subjected to C-chamfering or R-chambering, it is possible to obtain the same advantages.

Embodiment 1

Fan 100

FIG. 1 is a perspective view illustrating a configuration of a fan 100 including an impeller 10 according to Embodiment 1. FIG. 1 illustrates part of the configuration of the fan 100 as viewed from a suction side, or as viewed from a side where suction surfaces 26 of blades 20 are located. In FIG. 1 and following figures that will be referred to later, a bold black arrow R indicates the rotation direction of the impeller 10, or the rotation direction of the blades 20 and a boss 12, which is part of the impeller 10. In the figures, a double arrow CD indicates the circumferential direction of the impeller 10.
In FIG. 1 and the following figures, an outlined bold arrow F indicates a general air flow direction in which air flows when the impeller 10 rotates. In the air flow direction indicated by the outlined bold arrow F, relative to the impeller 10, the Y1 side is an upstream side of the airflow, and the Y2 side is a downstream side of the airflow. In other words, relative to the impeller 10, the Y1 side is an air suction side, and the Y2 side is an air blowing side.
In FIG. 1, the X axis is a direction perpendicular to a rotation axis 11 of the impeller 10, that is, a radial direction of the impeller 10. In the radial direction, part on the X2 side is outer part relative to part on the X1 side, and the part on the X1 side is inner part relative to the part on the X2 side. In other words, the X1 side of the impeller 10 is the inner part of the impeller 10, and the X2 side of the impeller 10 is the outer part of the impeller 10. The rotation axis 11 is an imaginary rotation axis about which the impeller 10 rotates.
The impeller 10 according to Embodiment 1 and the fan 100 including the impeller will be described with reference to FIG. 1. The fan 100 according to Embodiment 1 is a device that creates a flow of air and is used to send the air. The fan 100 of Embodiment 1 is an axial flow fan that sends the air in a direction along the rotation axis 11. For example, the fan 100 is employed in an air-conditioning apparatus 200 (see FIG. 16), which will be described later.
As illustrated in FIG. 1, the fan 100 includes the impeller 10 and a casing 80. The casing 80 forms a shell of the fan 100. For example, the casing 80 is box-shaped (not illustrated). The casing 80 has a substantially cylindrical bell mouth 81. The impeller 10 is provided inward of an inner circumferential side of the bell mouth 81. The impeller 10 is provided such that the impeller 10 is rotatable about the rotation axis 11. The fan 100 includes a driving part (not illustrated) such as a motor, which causes the impeller 10 to rotate.

Impeller 10

FIG. 2 is a conceptual diagram for explanation of a basic configuration of the impeller 10 according to Embodiment 1, and is a view illustrating the impeller 10 projected on a plane perpendicular to the rotation axis 11. The conceptual diagram of FIG. 2 is used to explain the basic configuration of the impeller 10. The relationships in relative dimensions, shape, and other conditions between the components in FIG. 2 may differ from those of actual ones. FIG. 2 illustrates the configuration of the impeller 10 as the suction surface 26 of each of the blades 20 is viewed. The impeller 10 according to Embodiment 1 will be described with reference to FIGS. 1 and 2.
The impeller 10 is an axial flow impeller and is a device that creates a flow of fluid such as air. The impeller 10 rotates about the rotation axis 11 in the rotation direction indicated by the bold black arrow R, thus creating a flow of air. As illustrated in FIG. 2, the impeller 10 includes the boss 12 on the rotation axis 11 and the multiple blades 20 on an outer circumference of the boss 12.

Boss 12

The boss 12 has a substantially cylindrical shape. The center of the boss 12 is connected to a drive shaft (not illustrated) included in the driving part. When receiving a rotational driving force from the driving part via the drive shaft, the boss 12 rotates about the rotation axis 11. The boss 12 is driven to rotate, by the driving part, and the rotation axis 11 extends through the boss 12.

Blades 20

When the impeller 10 rotates, the blades 20 push air between the blades 20 to send the air. The blades 20 are substantially equiangularly spaced on the outer circumference of the boss 12. The blades 20 protrude substantially radially from an outer circumferential wall of the boss 12. The blades 20 are arranged around the boss 12 and extend outward radially from the boss 12.
More specifically, each of the blades 20 protrudes from the outer circumferential wall of the boss 12 toward an outer circumference of the impeller 10 in the radial direction from the rotation axis 11 such that the blade 20 slopes forward in the rotation direction of the impeller 10. Although FIG. 2 illustrates the impeller 10 including four blades 20, the number of blades 20 included in the impeller 10 is not limited to four. The number of the blades 20 of the impeller 10 may be less than four or may be more than four.
Each of the blades 20 has a leading edge 21, a trailing edge 22, an outer end 23, and an inner edge 24. The leading edge 21 is an edge that is included in the periphery of the blade 20 and faces forward in the rotation direction. The trailing edge 22 is an edge that is included in the periphery of the blade 20 and faces rearward in the rotation direction. The outer end 23 is an outer peripheral edge of the periphery of the blade 20. The outer end 23 forms an outer edge between the leading edge 21 and the trailing edge 22. The inner edge 24 is an inner peripheral edge of the periphery of the blade 20. The inner edge 24 is shaped along the outer circumferential wall of the boss 12 and is joined to the outer circumferential wall.
The outer end 23 and the leading edge 21 are adjacent to each other, with an outer leading end 23a interposed between the outer end 23 and the leading edge 21. The outer leading end 23a is a front end of the outer end 23 in the rotation direction and is also an outer end of the leading edge 21 in the radial direction from the rotation axis 11. The outer end 23 and the trailing edge 22 are adjacent to each other, with an outer trailing end 23b interposed between the outer end 23 and the trailing edge 2. The outer trailing end 23b is a rear end of the outer end 23 in the rotation direction and is also an outer end of the trailing edge 22 in the radial direction from the rotation axis 11.
The inner edge 24 and the leading edge 21 are adjacent to each other, with an inner leading end 24a interposed between the inner edge 24 and the leading edge 21. The inner leading end 24a is a front end of the inner edge 24 in the rotation direction and is also an inner end of the leading edge 21 in the radial direction from the rotation axis 11. The inner edge 24 and the trailing edge 22 are adjacent to each other, with an inner trailing end 24b interposed between the inner edge 24 and the trailing edge 22. The inner trailing end 24b is a rear end of the inner edge 24 in the rotation direction and is also an inner end of the trailing edge 22 in the radial direction from the rotation axis 11.
Each of the blades 20 has a pressure surface 25 and the suction surface 26 as blade surfaces 35. Of the two blade surfaces 35 of the blade 20, the pressure surface 25 is a surface that faces forward in the rotation direction. The pressure surface 25 pushes the air when the blade 20 rotates. Of the two blade surfaces 35 of the blade 20, the suction surface 26 is a surface that faces rearward in the rotation direction and is opposite to the pressure surface 25. FIGS. 1 and 2 illustrate the configuration of the fan 100 and that of the impeller 10 as the suction surface 26 is viewed. The pressure surface 25 is indicated by a dashed leader line.
Regarding the blade surfaces 35, the suction surface 26 faces an upstream side (the Y1 side) of the blade 20 in the air flow direction indicated by the outlined bold arrow F, and the pressure surface 25 faces downstream side (the Y2 side) of the blade 20 in the air flow direction indicated by the outlined bold arrow F. The pressure surface 25 faces in the rotation direction of the blade 20. The suction surface 26 faces in the opposite direction to the rotation direction of the blade 20.
The blades 20 rotate together with the boss 12 about the rotation axis 11. When the blades 20 rotate, as indicated by the outlined bold arrow F in FIG. 1, the air flows along the rotation axis 11 in a direction downward from a side located above the plane of the drawing and is sucked into the fan 100. The air sucked into the fan 100 flows along the rotation axis 11 and is blown out of the fan 100 in the direction further downward from the plane of the drawing.
FIG. 3 is a conceptual diagram of a section taken along line III-III in FIG. 2 as viewed in the direction indicated by arrows. FIG. 4 is a conceptual diagram of an example of a chordwise-direction cross-section CS of the blade 20 of the impeller 10 according to Embodiment 1. FIG. 5 is a conceptual diagram illustrating a chord 30 and a camber line 31 of a chordwise-direction cross-section CS1 taken along line IV-IV in FIG. 2. FIG. 6 is a conceptual diagram illustrating the chord 30 and the camber line 31 of a chordwise-direction cross-section CS2 taken along line V-V in FIG. 2. In FIGS. 3, 5, and 6, a vertical direction corresponds to the direction along the rotation axis 11, an upper side corresponds to the suction side, and a lower side corresponds to the blowing side.
As illustrated in FIG. 2, in the case where imaginary cylinders CL in each of which the rotation axis 11 is set as the center thereof are assumed, an imaginary cross-section of each of parts of each of the blades 20 that correspond to the imaginary cylinders CL will be referred to as "chordwise-direction cross-section CS". In other words, regarding each of the imaginary cylinders CL in each of which the center thereof corresponds to the rotation axis 11, an imaginary cross-section of the blade 20 that is cut along the imaginary cylinder CL will be referred to as "chordwise-direction cross-section CS".
The blade 20 has multiple chordwise-direction cross-sections CS in the radial direction from the rotation axis 11. It should be noted that the chordwise-direction cross-section CS as illustrated in FIG. 4 is an example. The blade surfaces 35 including the pressure surface 25 and the suction surface 26 as illustrated in FIG. 4 are examples. The blade surfaces 35 are not limited to those in the example illustrated in FIG. 4. In the multiple chordwise-direction cross-sections CS, for example, a cross-section taken along line IV-IV in FIG. 2 will be referred to as "chordwise-direction cross-section CS1", and a cross-section taken along line V-V in FIG. 2 will be referred to as "chordwise-direction cross-section CS2".
As illustrated in FIGS. 5 and 6, in the chordwise-direction cross-section CS, a straight line that connects the leading edge 21 and the trailing edge 22 will be referred to as "chord 30", and in the chordwise-direction cross-section CS, a central line of the cross-section of the blade that connects the leading edge 21 and the trailing edge 22 will be referred to as "camber line 31". The central line of the cross-section of the blade is a line passing through the center between the pressure surface 25 and the suction surface 26 in the chordwise-direction cross-section CS. In FIGS. 5 and 6, only the chord 30 and the camber line 31 are illustrated to indicate the relationship between the chord 30 and the camber line 31, and illustration of the blade surfaces 35 including the pressure surface 25 and the suction surface 26 of the blade 20 is omitted.
In each of the chordwise-direction cross-sections CS, in the case where the ratio of a distance from the leading edge 21 to a point to a distance from the trailing edge 22 to the point is constant, the point will be referred to as "imaginary point P". A line that connects imaginary points P in the chordwise-direction cross-sections CS from the inner edge 24 to the outer end 23 will be referred to as "span line 27" (see FIG. 2). The ratio of the distance from the leading edge 21 to the imaginary point P to the distance from the trailing edge 22 to the imaginary point P is determined based on required design objectives.
The distance from each of the leading edge 21 and the trailing edge 22 to the imaginary point P is measured along a camber line of the blade 20 on a cross-section of the cylinder, for example. In other words, the distance from each of the leading edge 21 and the trailing edge 22 to the imaginary point P is measured along the camber line 31 of the blade 20 on the chordwise-direction cross-section CS, for example. It should be noted that the positions of the points P indicated in FIGS. 5 and 6 are each an example. The positions of the points P are not limited to those in FIG. 5 or 6.
A direction along the span line 27 from the inner edge 24 toward the outer end 23 will be referred to as "spanwise direction". Furthermore, a section of the blade 20 that is taken along the span line 27 and parallel to the rotation axis 11 will be referred to as "spanwise-direction section SS". FIG. 3 illustrates a spanwise-direction section SS of the blade 20 that is taken along a span line 27.
A span line 27a, a span line 27b, and a span line 27c illustrated in FIG. 2 are examples of span lines 27 that indicate spanwise-direction sections SS of the blade 20. The span line 27b in FIG. 2 is a span line 27 that passes through imaginary points P corresponding to midpoints between the leading edge 21 and the trailing edge 22 in the chordwise-direction cross-sections CS of the blade 20, which are the cross-sections of the cylinders. In other words, in each chordwise-direction cross-section CS of each of the blades 20 located around the rotation axis 11, the distance between the leading edge 21 and the span line 27b is equal to the distance between the trailing edge 22 and the span line 27b. That is, in the chordwise-direction cross-section CS of each of the blades 20 located around the rotation axis 11, the distance between the leading edge 21 and the imaginary point P is equal to the distance between the trailing edge 22 and the imaginary point P.
The span line 27a in FIG. 2 is one of span lines 27 located closer to the leading edge 21 than to the span line 27b. The span line 27a in FIG. 2 is a span line 27 that passes through imaginary points P that are located closer to the leading edge 21 than the midpoints between the leading edge 21 and the trailing edge 22 in the chordwise-direction cross-sections CS of the blade 20 that are the cross-sections of the cylinders. That is, in each of the chordwise-direction cross-sections CS of the blades 20 located around the rotation axis 11, the distance between the leading edge 21 and the span line 27a is less than the distance between the trailing edge 22 and the span line 27a. Thus, in the chordwise-direction cross-section CS of each of the blades 20 located around the rotation axis 11, the distance between the leading edge 21 and the imaginary point P is less than the distance between the trailing edge 22 and the imaginary point P.
The span line 27c in FIG. 2 is one of span lines 27 that is located closer to the trailing edge 22 than to the span line 27b. In the chordwise-direction cross-sections CS of the blade 20 that are the cross-sections of the cylinders, the span line 27c in FIG. 2 is a span line 27 that passes through imaginary points P that are located closer to the trailing edge 22 than the midpoints between the leading edge 21 and the trailing edge 22. That is, in each of the chordwise-direction cross-sections CS of each of the blades 20 located around the rotation axis 11, the distance between the leading edge 21 and the span line 27c is greater than the distance between the trailing edge 22 and the span line 27c. Thus, in each of the chordwise-direction cross-sections CS of the above blade 20 located around the rotation axis 11, the distance between the leading edge 21 and the imaginary point P is greater than the distance between the trailing edge 22 and the imaginary point P.
As illustrated in FIG. 3, the spanwise-direction section SS of the blade 20 that is adjacent to the trailing edge 22 is convex on the suction side in, for example, the whole of an area between the inner edge 24 and the outer end 23. That is, part of the blade 20 that is adjacent to the trailing edge 22 bends in an area between a radially middle portion 28 and the outer end 23 such that the part is convex on the suction side or concave on the blowing side.
The midpoint between a joint between the boss 12 and the leading edge 21 and a joint between the boss 12 and the trailing edge 22 will be referred to as "boss midpoint 12a". A plane that passes through the boss midpoint 12a and that is perpendicular to an axial direction along the rotation axis 11 will be referred to as "boss middle plane 40". The distance between the boss middle plane 40 and the spanwise-direction section SS adjacent to the trailing edge 22 in the axial direction along the rotation axis 11 will be referred to as "trailing-edge side blade height Sh". In the spanwise-direction section SS of the blade 20 that is adjacent to the trailing edge 22, an extreme point at which the lowest "trailing-edge side blade height Sh" is located in the area between the inner edge 24 and the outer end 23 and at which the section is concave on the suction side will be referred to as "trailing-edge concave portion 29". The blade 20 has "trailing-edge concave portion 29".
The distance from the rotation axis 11 to a point on the boss middle plane 40 will be referred to as "distance r". As illustrated in FIG. 2, the distance from the rotation axis 11 to the inner edge 24 will be referred to as "distance r1", and the distance from the rotation axis 11 to the outer end 23 will be referred to as "distance r2". In this case, when v = (r - r1)/(r2 - r1), it is preferable that the trailing-edge concave portion 29 be located such that v satisfies 0.4 < v < 0.8.
As illustrated in FIGS. 5 and 6, the distance from the chord 30 to the camber line 31 will be referred to as "camber height H". The camber height H is the distance between the chord 30 and the camber line 31 in a direction perpendicular to the chord 30, in the chordwise-direction cross-section CS. On the camber line 31, a point at which the camber height H is maximum will be referred to as "maximum extreme point 33", and a position at which the distance from the leading edge 21 to this position is equal to the distance from the trailing edge 22 to the position on the camber line 31 will be referred to as "camber midpoint 34".
As illustrated in FIG. 5, in the chordwise-direction cross-section CS1 closer to the inner edge 24 than to the outer end 23 of the blade 20, the maximum extreme point 33 is located closer to the trailing edge 22 than to the camber midpoint 34 and closer to the air suction side than to the chord 30. As illustrated in FIG. 5, in the chordwise-direction cross-section CS1 closer to the inner edge 24 than to the outer end 23 of the blade 20, the camber line 31 has at least one inflection point 32 between the leading edge 21 and the maximum extreme point 33. The inflection point 32 is a point at which the camber line 31 changes from convex on the suction side to convex on the blowing side or from convex on the blowing side to convex on the suction side in a direction from the leading edge 21 toward the trailing edge 22.
As illustrated in FIG. 6, in the chordwise-direction cross-section CS2 closer to the outer end 23 than to the inner edge 24 of the blade 20, the maximum extreme point 33 is located closer to the leading edge 21 than to the camber midpoint 34 and closer to the air suction side than to the chord 30.

Advantages of Impeller 10

The impeller 10 is configured as follows. In the chordwise-direction cross-section CS1 closer to the inner edge 24 than to the outer end 23 of each blade 20, the maximum extreme point 33 is located closer to the trailing edge 22 than to the camber midpoint 34 and closer to the air suction side than to the chord 30. The camber line 31 has at least one inflection point 32 between the leading edge 21 and the maximum extreme point 33. In the chordwise-direction cross-section CS2 closer to the outer end 23 than to the inner edge 24 of the blade 20, the maximum extreme point 33 is located closer to the leading edge 21 than to the camber midpoint 34 and closer to the air suction side than to the chord 30.
By virtue of such a configuration, in the impeller 10, it is possible to cause airflow to move along the blade 20, thus reducing airflow separation on an outer portion of the blade 20 that is adjacent to the leading edge 21. It is therefore possible to improve the air-sending performance of the impeller 10, improve the air-sending efficiency, and achieve a higher fan efficiency.
In a typical axial flow fan, the efficiency of an impeller is improved by reduction of occurrence of airflow separation that occurs on the surfaces of blades. Furthermore, in the impeller, it is possible to achieve a large volume of air by increasing the area of the blades or increasing the rotation speed of the impeller. However, it is not possible to increase the area of the blades to such an extent that the height of the blades of the impeller exceeds a height based on design constraints, nor to increase the rotation speed to such an extent that the impeller rotates beyond a maximum rotation speed that is determined based on the strength of the impeller and an upper limit capacity of a motor.
In the impeller of Patent Literature 1, where R1 is the midpoint of the root of the blade in the circumferential direction, R2 is the midpoint of the outer portion of the blade in the circumferential direction, and O is the axis about which the blade rotates, the angle between the line that connects O and R1 and the line that connects O and R2 falls within the range of 18 to 22 degrees, and the line P connecting R1 and R2 is inclined at an angle of 22 to 27 degrees toward the suction side relative to a plane that passes through R1 and is perpendicular to the axis of rotation.
In the impeller of Patent Literature 1, the blades each have an inflection point in its cross-section in the circumferential direction. In the impeller of Patent Literature 1, the blade has a convex shape on the discharge side from the leading edge of the blade in the rotation direction of the blade to the inflection point and a concave shape on the discharge side from the inflection point to the trailing edge of the blade in the rotation direction of the blade. The impeller of Patent Literature 1 includes the blades each having the above convex and concave shapes over the entire length thereof from the root to the outer portion. It is therefore possible to reduce noise caused by rotation of the blades during rotation of the impeller without increasing the height of each blade.
In an impeller, the magnitude of a rotation-direction component of airflow that passes through the leading edge of each of blades is proportional to the radius of the impeller. Therefore, the magnitude of the rotation-direction component of the airflow passing through the leading edge of the blade at a position closer to the inner edge than to the outer end is smaller than that in a position closer to the outer end than to the inner edge.
The magnitude of the rotation-direction component of the airflow passing through the leading edge of the blade at the position closer to the outer end than to the inner edge is greater than that at the position closer to the inner edge than to the outer end. That is, the closer the leading edge of the blade is to the inner edge in the radial direction, the smaller the magnitude of the rotation-direction component of the airflow passing through the leading edge of the blade, and the closer the leading edge of the blade is to the outer end in the radial direction, the greater the magnitude of the rotation-direction component of the airflow passing through the ledge edge of the blade.
In the impeller of Patent Literature 1, each of the blades has the convex shape in an area adjacent to the leading edge and the concave shape in an area adjacent to the trailing edge over the entire length thereof from the root to the outer portion. Due to the convex shape in the outer portion, where air flows fast, of each blade of the impeller, airflow separation may occur, and thus deteriorate the air-sending performance. In the impeller, therefore, it is necessary to reduce occurrence of airflow separation at part of the outer portion of the blade that is adjacent to the leading edge.
FIG. 7 is a conceptual diagram illustrating the chord 30 and the camber line 31 of the chordwise-direction cross-section CS1 taken along line IV-IV in FIG. 2 to explain the operation of the impeller 10 according to Embodiment 1 and the airflow. In FIG. 7, the vertical direction corresponds to the direction along the rotation axis 11, the upper side corresponds to the air suction side, and the lower side corresponds to the air blowing side. In FIG. 7, dashed arrows FA indicate airflow around the blade 20.
As illustrated in FIG. 7, in the chordwise-direction cross-section CS1 closer to the inner edge 24 than to the outer end 23 of the blade 20, the maximum extreme point 33 is located closer to the trailing edge 22 than to the camber midpoint 34 and closer to the air suction side than to the chord 30.
Thus, as indicated by dashed arrows FA in FIG. 7, the airflow is bent at part of the blade 20 that is adjacent to the trailing edge 22 or that is closer to the trailing edge 22 than to the leading edge 21 of the blade 20, such that the radius of the curvature decreases, thus increasing a rise in static pressure on the blade 20. Therefore, the impeller 10 increases the volume of air at the same rotation speed of the blades 20 as in an impeller that does not have the above configuration, as compared with the impeller that does not have the above configuration.
In addition to the above shape, as illustrated in FIGS. 5 and 7, in the chordwise-direction cross-section CS1 closer to the inner edge 24 than to the outer end 23 of the blade 20, the camber line 31 has at least one inflection point 32 between the leading edge 21 and the maximum extreme point 33.
By virtue of the above configuration, in the impeller 10, it is possible to reduce the radius of curvature of part of the blade 20 that is adjacent to the trailing edge 22 and also reduces occurrence of airflow separation on part of the blade 20 that is adjacent to the leading edge 21 to increase the air-sending efficiency of the blade 20, as compared with the impeller that does not have the above configuration.
That is, in the impeller 10, it is possible to reduce the radius of curvature of part of the blade 20 that is closer to the trailing edge 22 than to the leading edge 21 and reduces occurrence of airflow separation on part of the blade 20 that is closer to the leading edge 21 than to the trailing edge 22 to increase the air-sending efficiency of the blade 20. Thus, the impeller 10 achieves a higher fan efficiency than the impeller that does not have the above configuration.
Unlike the impeller that does not have the above configuration, In the impeller 10, the positions of the leading edge 21 and the trailing edge 22 of the blade 20 remain unchanged. Therefore, the impeller 10 can obtain the above advantages, for example, achieve a higher fan efficiency of the impeller 10 and an increase in air volume at the same rotation speed, without changing the size of the impeller 10.
FIG. 8 is a conceptual diagram illustrating the chord 30 and the camber line 31 in the chordwise-direction cross-section CS2 taken along line V-V in FIG. 2 to explain the operation of the impeller 10 according to Embodiment 1 and the airflow. In FIG. 8, the vertical direction corresponds to the direction along the rotation axis 11, the upper side corresponds to the air suction side, and the lower side corresponds to the air blowing side. In FIG. 8, the dashed arrow FA indicates airflow around the blade 20.
As illustrated in FIG. 8, in the chordwise-direction cross-section CS2 closer to the outer end 23 than to the inner edge 24 of the blade 20, the maximum extreme point 33 is located closer to the leading edge 21 than to the camber midpoint 34 and closer to the air suction side than to the chord 30.
As described above, the magnitude of the rotation-direction component of airflow that passes through the leading edge of the blade is proportional to the radius. Therefore, the magnitude of the rotation-direction component of airflow that passes through the leading edge of part of the blade that is adjacent to the outer end is greater than that of airflow that passes through the leading edge of part of the blade that is adjacent to the inner edge.
Thus, in the impeller 10, the airflow that has passed through the leading edge 21 flows along part of the blade 20 that is closer to the outer end 23 than to the inner edge 24 in the impeller 10. It is therefore possible to reduce occurrence of airflow separation and increase the air-sending efficiency of the blade 20. As a result, the impeller 10 achieves a higher fan efficiency than the impeller that does not have the above-described configuration.
Additionally, in the impeller 10, the maximum extreme point 33 is located closer to the leading edge 21 than to the camber midpoint 34 and closer to the air suction side than to the chord 30, whereby it is possible to reduce the radius of curvature at part of the blade 20 that is adjacent to the leading edge 21. In other words, since the maximum extreme point 33 is located closer to the leading edge 21 than to the camber midpoint 34 and closer to the air suction side than to the chord 30 in the impeller 10, it is possible to reduce the radius of curvature at part of the blade 20 that is closer to the leading edge 21 than to the trailing edge 22.
Therefore, in the impeller 10, it is possible to increase a rise in static pressure on the part of the blade 20 that is adjacent to the leading edge 21, as compared with the impeller that does not have the above configuration. Thus, it is possible to reduce a pressure gradient from the leading edge 21 of the blade 20 to the trailing edge 22 thereof. As a result, in the impeller 10, it is possible to increase the volume of air at the same rotation speed of the blades 20 as in the impeller that does not have the above configuration, as compared with the impeller that does not have the above configuration. Thus, the impeller 10 achieves a higher fan efficiency than the impeller that does not have the above configuration.
In the impeller 10, unlike the impeller that does not have the above configuration, the positions of the leading edge 21 and the trailing edge 22 of the blade 20 remain unchanged. Therefore, in the impeller 10, it is possible to obtain the above advantages, for example, increase the fan efficiency of the impeller 10 and increase the air volume at the same rotation speed as in the impeller that does not have the above configuration, without changing the size of the impeller 10.

Embodiment 2

FIG. 9 is a conceptual diagram of an impeller 10 according to Embodiment 2, which illustrates the chord 30 and the camber line 31 of the chordwise-direction cross-section CS1 taken along line IV-IV in FIG. 2. FIG. 10 is a conceptual diagram of the impeller 10 according to Embodiment 2, which illustrates the chord 30 and the camber line 31 of the chordwise-direction cross-section CS2 taken along line V-V in FIG. 2. The impeller 10 according to Embodiment 2 will be described.
Features of the impeller 10 according to Embodiment 2 reside in the chordwise-direction cross-sections CS of the blades 20 located around the rotation axis 11. A configuration of the impeller 10 according to Embodiment 2 will be described below, and the other configurations thereof are the same as those of the impeller 10 according to Embodiment 1. The features of the impeller 10 according to Embodiment 2 will be described with reference to FIG. 2 referred to above and FIGS. 9 and 10. It should be noted that components that have the same functions and operations as those in Embodiment 1 will be denoted by the same reference signs, and their descriptions will thus be omitted.
As illustrated in FIG. 2 and 9 and 10, the impeller 10 is formed such that in a region located across each of the blades 20 in the radial direction from the rotation axis 11, the camber line 31 is located closer to the air suction side than to the chord 30. In other words, the impeller 10 is formed such that the camber line 31 is located closer to the air suction side than to the chord 30 in each of the chordwise-direction cross-sections CS from the inner edge 24 of the blade 20 to the outer end 23 thereof.

Advantages of Impeller 10

The impeller 10 is formed such that in the region located across the blade 20 in the radial direction from the rotation axis 11, the camber line 31 is located closer to the air suction side than to the chord 30. Since the impeller 10 is formed such that in the region located across the blade 20, the camber line 31 is located closer to the air suction side than to the chord 30, it is possible to increase the amount of pressure rising in the impeller 10 and improve the fan efficiency, as compared with the impeller that does not have such a configuration.
If an impeller is formed such that the camber line is located closer to the air blowing side than to the chord at part of each blade, airflow is greatly bent by the part in the opposite direction to a direction in which the effect of pressure rising is obtained, and the blade will thus fail to work in the impeller. Therefore, if an impeller is formed such that the camber line is located closer the air blowing side than to the chord at part of each blade, in the impeller, the amount of pressure rising decreases to a small value, or airflow will not flow along the blade at the above part and separate from the blade, thus deteriorating the fan efficiency of the impeller.
In contrast, the blade 20 of the impeller 10 according to Embodiment 2 is formed such that in the region located across the blade 20, the camber line 31 is located closer to the air suction side than to the chord 30. Therefore, it is possible to increase the amount of pressure rising in the impeller 10, and improve the fan efficiency, as compared with that in the impeller that does not have such a configuration.
FIG. 11 is a graph indicating a relationship between the flow coefficient and the fan efficiency of the impeller 10 according to Embodiment 2 and that of an impeller used in the related art. In FIG. 11, circles represent the impeller of the related art, and crosses represent the impeller 10 according to Embodiment 2. The impeller of the related art is a typical impeller that does not have the features of the impeller 10 according to Embodiment 2. As illustrated in FIG. 11, the impeller 10 according to Embodiment 2 exhibits a higher fan efficiency with respect to the flow coefficient than the impeller of the related art. The impeller 10 according to Embodiment 2 thus exhibits an improved fan efficiency as compared with the impeller of the related art.
FIG. 12 is a graph indicating a relationship between the flow coefficient and the pressure coefficient of the impeller 10 according to Embodiment 2 and that of the impeller of the related art. In FIG. 12, circles represent the impeller of the related art, and cross marks represent the impeller 10 according to Embodiment 2. It should be noted that the impeller of the related art is a typical impeller that does not have the features of the impeller 10 according to Embodiment 2.
As illustrated in FIG. 12, the impeller 10 according to Embodiment 2 exhibits a higher pressure coefficient for all regions with respect to the flow coefficient than the impeller of the related art. The impeller 10 according to Embodiment 2 can thus increase the volume of air at the same rotation speed as the impeller of the related art, as compared with the impeller of the related art.

Embodiment 3

FIG. 13 is a conceptual diagram of an impeller 10 according to Embodiment 3, which illustrates the chord 30 and the camber line 31 of the chordwise-direction cross-section CS1 taken along line IV-IV in FIG. 2. FIG. 14 is a conceptual diagram of the impeller 10 according to Embodiment 3, which illustrates the chord 30 and the camber line 31 of the chordwise-direction cross-section CS2 taken along line V-V in FIG. 2. The impeller 10 according to Embodiment 3 will be described.
Features of the impeller 10 according to Embodiment 3 reside in the chordwise-direction cross-sections CS of part of each of the blades 20 located around the rotation axis 11 that is close to the inner edge 24 and part thereof that is close to the outer end 23. A configuration of the impeller 10 according to Embodiment 3 will be described below, and the other configurations thereof are the same as those of the impeller 10 according to Embodiment 1 or 2. The features of the impeller 10 according to Embodiment 3 will be described with reference to FIG. 2 referred to above and FIGS. 13 and 14. It should be noted that components that have the same functions and operations as those in Embodiment 1 or 2 will be denoted by the same reference signs, and their descriptions will thus be omitted.
As described above, the distance from the chord 30 to the camber line 31 will be referred to as "camber height H". The camber height H is the distance between the camber line 31 and the chord 30 in the direction perpendicular to the chord 30 in the chordwise-direction cross-section CS.
Regarding the camber height H, as illustrated in FIG. 13, in the chordwise-direction cross-section CS1 closer to the inner edge 24 than to the outer end 23 of the blade 20, the distance between the maximum extreme point 33 and the chord 30 in the direction perpendicular to the chord 30 will be referred to as "distance H_h".
Regarding the camber height H, as illustrated in FIG. 14, in the chordwise-direction cross-section CS2 closer to the outer end 23 than to the inner edge 24 of the blade 20, the distance between the maximum extreme point 33 and the chord 30 in the direction perpendicular to the chord 30 will be referred to as "distance Ht".
The impeller 10 is formed such that the distance H_t is greater than the distance H_h. That is, the impeller 10 is formed such that the distance H_h and the distance H_t satisfy a relationship expressed by H_h < H_t.

Advantages of Impeller 10

As described above, the magnitude of the rotation-direction component of airflow that passes through the leading edge of the blade is proportional to the radius. Therefore, the magnitude of the rotation-direction component of airflow passing by the leading edge of part of the blade that is adjacent to the outer end is greater than that of airflow passing through the leading edge of part of the blade that is adjacent to the inner edge. In addition, the area of each of the cross-sections of the cylinders that is used to define the chordwise-direction cross-sections CS of the blades 20 around the rotation axis 11 is proportional to the radius in the case where the height in the axial direction is constant. Therefore, the chord length of the blade 20 can be increased in a direction from the inner edge 24 toward the outer end 23.
In the impeller 10, by setting chord lengths to great values, it is possible to increase the volume of air at the same rotation speed as in the impeller that does not have the above configuration. Therefore, since the impeller 10 is formed such that the distance H_h and the distance H_t satisfy the relationship expressed by H_h < H_t, in the blades 20, it is possible to further raise the static pressure on an outer portion, where the magnitude of airflow is greater than that of airflow on an inner portion, as compared with the impeller that does not have the above configuration. As a result, in the impeller 10, it is possible to increase the volume of air at the same rotation speed of the blades 20 as in the impeller that does not have the above configuration, as compared with the impeller that does not have the above configuration. Thus, the impeller 10 achieves a higher fan efficiency than the impeller that does not have the above configuration.

Embodiment 4

FIG. 15 is a conceptual diagram of a fan 100 according to Embodiment 4, which illustrates a section of the fan 100 on an arbitrary plane that is parallel to and passes through the rotation axis 11 of the fan 100 as illustrated in FIG. 1. The fan 100 according to Embodiment 4 will be described with reference to FIG. 15 and FIG. 1 referred to above. It should be noted that components that have the same functions and operations as those in Embodiments 1 to 3 will be denoted by the same reference signs, and their descriptions will thus be omitted.
The fan 100 according to Embodiment 4 is provided with the casing 80 including the bell mouth 81 and the impeller 10 according to any one of Embodiments 1 to 3 that is provided in the casing 80. In other words, the fan 100 according to Embodiment 4 includes the casing 80 including the bell mouth 81 and the impeller 10 according to any one of Embodiments 1 to 3 that is provided at the inner circumference of the bell mouth 81 as viewed in the axial direction along the rotation axis 11.
The casing 80 is box-shaped and accommodates the impeller 10. The casing 80 has the bell mouth 81, which is substantially cylindrical on each of the air blowing side and the air suction side. The bell mouth 81 is shaped such that the distance from the rotation axis 11 to the bell mouth 81 increases in a direction away from the middle of the casing 80 along the rotation axis 11, for example. That is, the casing 80 is defined by the bell mouth 81 such that the distance from the rotation axis 11 to the casing 80 increases in the direction away from the middle of the casing 80 along the rotation axis 11.
The shapes of the bell mouth 81 and the casing 80 are not limited to the above shapes. Each of the bell mouth 81 and the casing 80 may have any shape unless the distance from the rotation axis 11 to it decreases in the direction away from the middle of the casing 80 along the rotation axis 11. In other words, the overall shape of the casing 80 may be cylindrical.
FIG. 15 illustrates the impeller 10 as an example of a trajectory that is traced by the blades 20 as the blades are rotated. In FIG. 15, the position of each of impellers 10S depicted by dotted lines is indicated as the limit of a range in which the advantages of the impeller 10 can be obtained when the impeller 10 is moved toward an associated one of the air suction side and the air blowing side.
The length of the casing 80 in the axial direction along the rotation axis 11 will be referred to as "length H_b". When the casing 80 is set such that the rotation axis 11 extends vertically, the length H_b of the casing 80 corresponds to the height of the casing 80.
As illustrated in FIG. 15, the impeller 10 can achieve its advantageous effects within a region that is located inward of an imaginary plane SF located on the air suction side and apart from the casing 80 by a distance εH_b in the axial direction along the rotation axis 11 and that is located inward of an imaginary plane SF located on the air blowing side and apart from the casing 80 by the distance εH_b in the axial direction along the rotation axis 11. The factor ε may be greater than 0 and less than or equal to 0.5 (0 < ε ≤ 0.5). In other words, the impeller 10 is provided within the region between the imaginary planes SF that are located on the air suction side and the air blowing side and apart from the casing 80 by the distance εH_b in the axial direction along the rotation axis 11.

Advantages of Fan 100

In the fan 100, the impeller 10 operates effectively, as illustrated in FIG. 15, when being provided within the region between the plane that is located on the air suction side and apart from the casing 80 by the distance εH_b in the axial direction along the rotation axis 11 and the plane that is located on the air blowing side and apart from the casing 80 by the distance εH_b in the axial direction along the rotation axis 11 to achieve the advantageous effects of the impeller 10.
By virtue of the above configuration, in the fan 100 according to Embodiment 4, in the impeller 10, it is possible to achieve a higher fan efficiency and increase the air volume at the same rotation speed as in the impeller that does not have the above configuration, without changing the size of the impeller 10.

Embodiment 5

FIG. 16 is a perspective view of an air-conditioning apparatus 200 according to Embodiment 5, which illustrates a configuration thereof. The air-conditioning apparatus 200 according to Embodiment 5 will be described with reference to FIG. 16. It should be noted that components that have the same functions and operations as those in Embodiments 1 to 4 are denoted by the same reference signs, and their descriptions will thus be omitted. Although the air-conditioning apparatus 200 is illustrated as an outdoor unit of a variable refrigerant flow (VRF) system in Embodiment 5, the air-conditioning apparatus 200 is not limited to the outdoor unit of the VRF system.
As illustrated in FIG. 16, the air-conditioning apparatus 200 includes the impeller 10 according to any of Embodiments 1 to 3 and the fan 100 according to Embodiment 4 including the impeller 10. The air-conditioning apparatus 200 further includes a housing 203. The air-conditioning apparatus 200 further includes a heat exchanger 204 that is provided in the housing 203 and causes heat exchange to be performed between air supplied by the impeller 10 and refrigerant flowing in the heat exchanger.
As illustrated in FIG. 16, the housing 203 is box-shaped. For example, the housing 203 has a rectangular cuboid shape. The shape of the housing 203 is not limited to a rectangular cuboid. The housing 203 has, in its upper portion, an air outlet 202 through which outdoor air sucked into the housing 203 is discharged therefrom to the outside of the air-conditioning apparatus 200.
In sides of the housing 203, respective air inlets 201 are formed as air inlets through which outdoor air is sucked into the housing 203. The air inlets 201 may be provided in all the four sides of the housing 203 or may be located in any one or more of the four sides. Each air inlet 201 may be located in part of the side of the housing 203 or may be located in the entire side of the housing 203.
The housing 203 has therein an air passage extending from the air inlet 201 to the air outlet 202. In the air passage, the fan 100 and the heat exchanger 204 are provided. The fan 100 is located upstream of the air outlet 202 and downstream of the heat exchanger 204 in the flow direction of air that is sent by the fan 100. The heat exchanger 204 causes heat exchange to be performed between the outdoor air and refrigerant that flows in the heat exchanger 204 to generate conditioned air.
In the air-conditioning apparatus 200, as the impeller 10 of the fan 100 rotates, the outdoor air is sucked into the housing 203 through the air inlet 201. The outdoor air exchanges heat with the refrigerant while passing through the heat exchanger 204, so that the outdoor air is heated or cooled and then serves as conditioned air. The conditioned air obtained through the heat exchange is blown from the air outlet 202 into an air-conditioning target space.

Advantages of Air-Conditioning Apparatus 200

As described above, in the fan 100, it is possible to achieve a higher efficiency and provide a larger volume of air than the impeller of the related art, without changing the size of the impeller, as compared with the impeller of the related art. Therefore, the air-conditioning apparatus 200 according to Embodiment 5 operates with a higher power efficiency and a larger volume of air than an air-conditioning apparatus used in the related art that includes a fan different from the fan 100, without any increase in dimensions of the air-conditioning apparatus 200, as compared with the air-conditioning apparatus of the related art.
As described above, the air-conditioning apparatus 200 according to Embodiment 5 includes the impeller 10 according to any one of Embodiments 1 to 3 and the heat exchanger 204 that causes heat exchange to be performed between air supplied by the impeller 10 and the refrigerant that flows in the heat exchanger. With the above configuration, the air-conditioning apparatus 200 includes the impeller 10, and can thus operate with a higher power efficiency and a larger volume of air than the air-conditioning apparatus of the related art that includes an impeller different from the impeller 10, without any change in dimensions of the air-conditioning apparatus 200, as compared with the air-conditioning apparatus of the related art.
The configurations described above with respect to the above embodiments are merely examples, and can be combined with another known technique or can be partly omitted or modified without departing from the gist of the present invention.

List of Reference Signs

10: impeller
10S: impeller
11: rotation axis
12: boss
12a: boss midpoint
20: blade
21: leading edge
22: trailing edge
23: outer end
23a: outer leading end
23b: outer trailing end
24: inner edge
24a: inner leading end
24b: inner trailing end
25: pressure surface
26: suction surface
27: span line
27a: span line
27b: span line
27c: span line
28: middle portion
29: trailing-edge concave portion
30: chord
31: camber line
32: inflection point
33: maximum extreme point
34: camber midpoint
35: blade surface
40: boss middle plane
80: casing
81: bell mouth
100: fan
200: air-conditioning apparatus
201: air inlet
202: air outlet
203: housing
204: heat exchanger
CD: double arrow
CL: cylinder
CS: chordwise-direction cross-section
CS1: chordwise-direction cross-section
CS2: chordwise-direction cross-section
F: outlined bold arrow
FA: arrow
H: height
H_h: distance
Ht: distance
P: imaginary point
R: bold black arrow
SF: imaginary plane
SS: spanwise-direction section
Sh: trailing-edge side blade height
r: distance
r1; distance
r2: distance

Claims

An impeller comprising:
a boss provided on a rotation axis; and

a plurality of blades provided on an outer circumference of the boss, and each having
a leading edge that is an edge facing forward in a rotation direction of the plurality of blades,

a trailing edge that is an edge facing rearward in the rotation direction,

an outer end that is an outer peripheral edge, and

an inner edge that is an inner peripheral edge,

wherein

where, in a case where a plurality of imaginary cylinders concentric with the rotation axis are assumed, an imaginary cross-section of each of parts of each of the plurality of blades that correspond to the imaginary cylinders is defined as a chordwise-direction cross-section,

in the chordwise-direction cross-section, a straight line that connects the leading edge and the trailing edge is defined as a chord, and a central line of a cross-section of the blade is defined as a camber line,

in the chordwise-direction cross-section, a distance between the chord and the camber line in a direction perpendicular to the chord is defined as a camber height,

on the camber line, a point equidistant from the leading edge and the trailing edge is defined as a camber midpoint, and

on the camber line, a point at which the camber height is maximum is defined as a maximum extreme point,

in the chordwise-direction cross-section closer to the inner edge than to the outer end of the blade, the maximum extreme point is located closer to the trailing edge than to the camber midpoint and closer to an air suction side than to the chord, and the camber line has at least one inflection point between the leading edge and the maximum extreme point, and

in the chordwise-direction cross-section closer to the outer end than to the inner edge of the blade, the maximum extreme point is located closer to the leading edge than to the camber midpoint and closer to the air suction side than to the chord.
The impeller of claim 1,
wherein in a region located across the blade in a radial direction from the rotation axis, the camber line is located closer to the air suction side than to the chord.
The impeller of claim 1 or 2, wherein
in a case where in the chordwise-direction cross-section closer to the inner edge than to the outer end of the blade, a distance between the chord and the maximum extreme point in the direction perpendicular the chord is defined as a distance H_h, and

in the chordwise-direction cross-section closer to the outer end than to the inner edge of the blade, a distance between the chord and the maximum extreme point in the direction perpendicular to the chord is defined as a distance H_t,

the distance H_h and the distance H_t satisfy a relationship expressed by H_h < H_t.
A fan comprising:
a casing including a bell mouth; and

the impeller of any one of claims 1 to 3 accommodated in the casing,

wherein in a case where the casing has a length H_b in an axial direction along the rotation axis and a factor ε satisfies 0 < ε ≤ 0.5, the impeller is provided within a region that is located inward of an imaginary plane located on the air suction side and apart from the casing by a distance εH_b in the axial direction along the rotation axis and is located inward of an imaginary plane located on an air blowing side and apart from the casing by the distance εH_b in the axial direction along the rotation axis.
An air-conditioning apparatus comprising:
the impeller of any one of claims 1 to 3; and

a heat exchanger configured to cause heat exchange to be performed between air supplied by the impeller and refrigerant flowing in the heat exchanger.