U.S. patent application number 12/933838 was filed with the patent office on 2011-01-27 for blower and heatpump using the same.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. Invention is credited to Yasuaki Kato, Takahide Tadokoro.
Application Number | 20110017427 12/933838 |
Document ID | / |
Family ID | 41216695 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110017427 |
Kind Code |
A1 |
Kato; Yasuaki ; et
al. |
January 27, 2011 |
BLOWER AND HEATPUMP USING THE SAME
Abstract
A now-noise blower is provided which reduces the turbulence of
incoming air flow itself even if there is un-uniformity resulting
from circumferential positions around a rotation shaft of air inlet
passage. Such a blower includes a blade 1 having its outer
circumferential edge 1c warped in a rotational direction and a
bellmouth 5 covering the circumference of the blade at the air
outlet side, wherein a surface of the bellmouth facing the blade
has a convex-shaped first upstream expanding portion 5c upstream
extending from a minimum inner diameter portion Pb3 and a
concave-shaped second upstream expanding portion 5d further
upstream extending, the second upstream expanding portion being
continuous from the first upstream expanding portion.
Inventors: |
Kato; Yasuaki; (Tokyo,
JP) ; Tadokoro; Takahide; (Tokyo, JP) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Chiyoda-ku
JP
|
Family ID: |
41216695 |
Appl. No.: |
12/933838 |
Filed: |
March 11, 2009 |
PCT Filed: |
March 11, 2009 |
PCT NO: |
PCT/JP2009/054645 |
371 Date: |
September 21, 2010 |
Current U.S.
Class: |
165/59 ;
416/242 |
Current CPC
Class: |
F24F 1/38 20130101; F24F
1/40 20130101; F04D 29/164 20130101; F04D 29/526 20130101 |
Class at
Publication: |
165/59 ;
416/242 |
International
Class: |
F24F 7/007 20060101
F24F007/007; F04D 29/38 20060101 F04D029/38 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 22, 2008 |
JP |
2008-111585 |
Sep 5, 2008 |
JP |
2008-228399 |
Claims
1. A blower comprising: a blade having an outer circumferential
edge having a recessed warp in a rotational direction, and an
annular bellmouth covering the circumference of the blade at an air
outlet side, wherein a portion of the bellmouth facing a face
composed of a rotational trajectory of the outer circumferential
edge has a first upstream expanding portion formed in a shape of a
convex, facing an upstream direction of a rotation shaft and
extending upstream from a minimum inner diameter position and a
second upstream expanding portion formed in a shape of a concave,
facing the upstream direction of the rotation shaft, being
continuous with and extending upstream from the first upstream
expanding portion.
2. The blower of claim 1, wherein an upstream portion of the second
upstream expanding portion is formed generally in a shape of a
cone.
3. The blower of claim 1, wherein a transition between the first
upstream expanding portion and the second upstream expanding
portion is located downstream of a maximum warpage position on the
outer circumferential edge of the blade.
4. The blower of claim 1, wherein a third upstream expanding
portion is formed in a shape of a convex in the upstream direction
of the rotation shaft, the third upstream expanding portion being
continuous with and extending upstream from the second upstream
expanding portion.
5. The blower of claim 4, wherein the second upstream expanding
portion or the third upstream expanding portion covers the maximum
warpage portion on the outer circumferential edge of the blade.
6. The blower of claim 1, wherein an outer circumferential edge
side of the blade of a propeller fan is warped toward an inlet side
from an outlet side.
7. The blower of claim 6, wherein regarding a warp formed from the
outlet side toward the inlet side in the outer circumferential edge
side of the blade of the propeller fan, a degree of the warp
becomes gradually smaller from a middle point between a leading
edge and a trailing edge toward the trailing edge.
8. A heat pump apparatus comprising: an air outlet face provided on
a top face or a side face of an enclosure and disposing a blower
thereon, an air inlet face provided on at least one face except the
air outlet face, a heat exchanger disposed so as to cover the air
inlet face; and a plurality of side plates to form the other faces
except the air outlet face and the air inlet face, wherein the
blower includes a blade having an outer circumferential edge having
a recessed warp in a rotational direction and an annular bellmouth
covering the circumference of the blade at an outlet side; and
wherein a portion of the bellmouth facing a face composed of a
rotational trajectory of the outer circumferential edge has a first
upstream expanding portion formed in a shape of a convex, facing an
upstream direction of a rotation shaft and extending upstream from
a minimum inner diameter position at an entire portion of a
circumferential direction of the bellmouth and a second upstream
expanding portion formed in a shape of a concave, facing the
upstream direction of the rotation shaft, being continuous with and
extending upstream from the first upstream expanding portion at an
entire portion of the circumferential direction of the
bellmouth.
9. The heat pump apparatus of claim 8, wherein an upstream portion
of the second upstream expanding portion is formed generally in a
shape of a cone.
10. (canceled)
11. A heat pump apparatus comprising: an air outlet face provided
on a top face or a side face of an enclosure and disposing a blower
thereon, an air inlet face provided on at least one face except the
air outlet face, a heat exchanger disposed so as to cover the air
inlet face; and a plurality of side plates to form the other faces
except the air outlet face and the air inlet face, wherein the
blower includes a blade having an outer circumferential edge having
a recessed warp in a rotational direction and an annular bellmouth
covering the circumference of the blade at an outlet side; and
wherein a portion of the bellmouth facing a face composed of a
rotational trajectory of the outer circumferential edge has a first
upstream expanding portion formed in a shape of a convex, facing an
upstream direction of a rotation shaft and extending upstream from
a minimum inner diameter position at an entire portion of a
circumferential direction of the bellmouth and a second upstream
expanding portion formed in a shape of a concave, facing the
upstream direction of the rotation shaft, being continuous with and
extending upstream from the first upstream expanding portion at
some portions of the circumferential direction of the
bellmouth.
12. The heat pump apparatus of claim 11, wherein an upstream
portion of the second upstream expanding portion is formed
generally in a shape of a cone.
13. The heat pump apparatus of claim 11, wherein the second
upstream expanding portion of the bellmouth has a curved surface at
both circumferential ends thereof, the curved surface being formed
in a shape of a convex in the direction of a rotation shaft.
14. The heat pump apparatus of claim 11, wherein a circumferential
position of the bellmouth where the second upstream expanding
portion partly extends upstream from the first upstream expanding
portion corresponds to a corner between side faces surrounding the
air outlet face of the enclosure.
15. The heat pump apparatus of claim 14, wherein the side faces
surrounding the air outlet face of the enclosure consist of the
plurality of side plates.
16. The heat pump apparatus of claim 14, wherein the side faces
surrounding the air outlet face of the enclosure consist of the
plurality of side plates and the heat exchanger.
17. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a propeller fan type blower
provided with a bellmouth and an impeller and to a heat pump
apparatus using such a blower and, more particularly, to
improvement of a bellmouth structure.
BACKGROUND ART
[0002] In order to provide a low-noise blower, it is necessary to
minimize a turbulent air flow coming into a blower. Until now,
various efforts have been made to improve the shape of a bellmouth
to reduce blast noise emissions from a blower provided with a
bellmouth and an impeller. For example, there has been proposed a
bellmouth that increases a diameter in a bending fashion toward an
upstream side from a straight pipe section having the smallest
bellmouth diameter and has a straight section formed radially
outwardly from its edge. Even if an air flow separation takes place
at a rim of such a straight section, such air flow again attaches
to the inner surface of the straight section while flowing
therealong, and thereafter smoothly moves and is inhaled into the
bellmouth, thereby reducing blast noise emissions (for example, see
Patent Document 1).
[0003] Also, there has been proposed a bellmouth which has an inlet
side wall having a cross-sectional shape which is a almost
semi-circular shape curved toward a radially outward direction from
the inner surface of an inlet opening, thereby suppressing
separation of air flow at the inlet opening to reduce noise
emissions when operating a fan (for example, Patent Document
2).
[0004] A bellmouth shape is proposed in such a way that, while
keeping a front panel of the outdoor unit of an air conditioning
apparatus rectangular, by changing the magnitude of a curvature of
the upstream diameter expanding curved portion from the portion
having the minimum bellmouth inner diameter in accordance with the
distance between the top, bottom, left, and right peripheral side
plates of a surrounding outdoor unit enclosure and the outer
circumference of the impeller, an orifice shape can be set in
accordance with a different inflow air flow angle in the vicinity
of the impeller, separation of flow is reduced in the vicinity of
the orifice, so that low noise is achieved. (For example, refer to
Patent Document 3.)
[0005] [Patent Document 1] Japanese Unexamined Patent Application
Publication No. 2003-184797 (FIGS. 1 to 3)
[0006] [Patent Document 2] Japanese Patent No. 3084790 (FIGS. 1 and
2)
[0007] [Patent Document 3] Japanese Patent No. 2769211 (FIGS. 2 and
3)
DISCLOSURE OF INVENTION
Problems To Be Solved By the Invention
[0008] A bellmouth having a radially outwardly extending straight
section formed at the rim, or having its inlet side wall curved in
an almost semi-circular shape toward a radially outward direction
from the inner surface of an inlet opening so as to reduce
separation of air flow on the bellmouth incoming from the outer
circumferential edge of a blade such as air flow incoming from a
region concealed by the bellmouth when seen from a blade of the
blower, can fulfill its function only when the blower is used under
an ideal air passage environment, that is, an environment where air
passage is circumferentially uniform about its rotation shaft.
However, such an ideal air passage environment is rare as an actual
air passage where the blower is operated. In addition, even if the
air passage is circumferentially uniform about the rotation shaft,
air flow coming into a blower is hardly stable and uniform. In
fact, incoming air flow is always changing and significantly
turbulent when viewed from a rotating blade, which makes it
difficult for a blower to sufficiently fulfill its function.
[0009] Further, a blower having a bellmouth whose curvature changes
according to un-uniformity resulting from a circumferential
position of an inlet side air passage just reduces separation on
the bellmouth, and is not effective in reducing the turbulence of
incoming air flow, assuming that such a blower is mounted on an air
conditioning apparatus.
[0010] An objective of the present invention is to reduce the
turbulence of incoming air flow itself to obtain a low noise blower
even if there is un-uniformity resulting from circumferential
positions about the rotation shaft of the inlet side air
passage.
Means For Solving the Problems
[0011] A blower according to the present invention comprises;
[0012] a blade having an outer circumferential edge having a
recessed warp in a rotational direction, and
[0013] a bellmouth covering the circumference of the blade at an
air outlet side,
[0014] wherein a surface of the bellmouth facing the blade has a
first upstream expanding portion formed in a shape of a convex in
an upstream direction of a rotation shaft, extending upstream from
a minimum inner diameter position and a second upstream expanding
portion formed in a shape of a concave in the upstream direction of
the rotation shaft, being continuous with and extending upstream
from the first upstream expanding portion.
Advantages
[0015] In a blower according to the present invention, a surface of
the bellmouth facing the blade has a first upstream expanding
portion formed in a shape of a convex in an upstream direction of a
rotation shaft, extending upstream from a minimum inner diameter
position and a second upstream expanding portion formed in a shape
of a concave in the upstream direction of the rotation shaft, being
continuous with and extending upstream from the first upstream
expanding portion, whereby the outer circumferential edge of the
blade is enclosed and a distance between the outer circumferential
edge and the bellmouth becomes wider. This allows more air to be
drawn in from around the outer circumferential edge, thereby
preventing a pressure change on the bellmouth surface arising from
turbulence by the blade tip vortex. In addition, this allows air
passage around the outer circumferential edge of a blade to be
circumferentially uniform, which suppresses fluctuation of air flow
coming into the blade, leading to the achievement of a low-noise
blower. Furthermore, this allows a section from the second upstream
expanding portion to the minimum inner diameter point to form a
smoothly continuous shape, which suppresses the turbulence of the
air flow itself and effectively reduces noise levels.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a front view of a blower according to Embodiment 1
of the present invention, as viewed from an outlet opening.
[0017] FIG. 2 is a cross-sectional view taken along the line A-A of
FIG. 1.
[0018] FIG. 3 is a cross-sectional view taken along the line B-B of
FIG. 1, whose outer circumferential edge is developed into a plane
with lines indicating a position of each part in a bellmouth.
[0019] FIG. 4 is an enlarged partial view of FIG. 2.
[0020] FIG. 5 is the same view as FIG. 3, with the addition of a
line illustrating the state of airflow in the vicinity of an outer
circumferential edge of a blade.
[0021] FIG. 6 is the same view as FIG. 2, with the addition of
lines indicating a conventional bellmouth for comparison.
[0022] FIG. 7(a) is a front view of an outdoor unit of an air
conditioning apparatus according to Embodiment 2, 6 of the present
invention. FIG. 7(b) is a cross-sectional view taken along the line
C-C.
[0023] FIG. 8 is a view showing the direction of an air passage, as
seen from the rotational shaft of an outdoor unit of an air
conditioning apparatus according to Embodiment 2, 6 of the present
invention,
[0024] FIG. 9(a) is a front view of an outdoor unit of an air
conditioning apparatus according to Embodiment 3 of the present
invention. FIG. 9(b) is a cross-sectional view taken along the line
D-D. FIG. 9(c) is a cross-sectional view taken along the line
E-E.
[0025] FIG. 10 is a view showing the direction of an air passage,
as seen from the rotational shaft of an outdoor unit of an air
conditioning apparatus according to Embodiment 3 of the present
invention.
[0026] FIG. 11 is a partially enlarged cross-sectional view of a
main section of a bellmouth and a propeller fan, as seen from an
inlet side.
[0027] FIG. 12(a) is a front view of an outdoor unit of a heat pump
water heater according to Embodiment 4 of the present invention.
FIG. 12(b) is a cross-sectional view taken along the line F-F. FIG.
12(c) is a cross-sectional view taken along the line G-G.
[0028] FIG. 13 is an enlarged view of a main section of a blower
according to Embodiment 5 of the present invention.
[0029] FIG. 14 is a view obtained by developing an outer
circumferential edge of a blade of a blower according to Embodiment
5 of the present invention into a plane with the addition of leader
lines indicating a position in a bellmouth as well as those
indicating the state of air flow in the vicinity of the outer
circumferential edge of a blade.
[0030] FIG. 15 is an enlarged view of a main section of a blower
according to Embodiment 5 of the present invention, with a
comparison with conventional one.
[0031] FIG. 16 is a comparison chart of aerodynamic noise
properties of a heat pump apparatus according to Embodiment 7 of
the present invention with conventional one.
[0032] FIG. 17 is a comparison chart of aerodynamic noise
properties of a heat pump apparatus according to Embodiment 7 of
the present invention with conventional one.
[0033] FIG. 18 is a diagram showing the shape of a blade of a
propeller fan according to Embodiment 7 of the present
invention.
[0034] FIG. 19 is a diagram showing the shape of a blade of a
propeller fan according to Embodiment 7 of the present
invention.
REFERENCE NUMERALS
[0035] 1 blade
[0036] 1c outer circumferential edge
[0037] Pb3 minimum inner diameter position
[0038] Pb4 point (transition position)
[0039] Pf3 maximum warpage position
[0040] 5 bellmouth
[0041] 5c first upstream expanding portion
[0042] 5d second upstream expanding portion
[0043] 5e third upstream expanding portion
[0044] 13 air outlet face
[0045] 15 heat exchanger (side face)
[0046] 17 top face of enclosure
[0047] 18 bottom plate (side face)
[0048] 22 separation plate (side face)
[0049] 23 end warpage (curved surface)
BEST MODES FOR CARRYING OUT THE INVENTION
Embodiment 1
[0050] Embodiment 1 of the present invention is described below
with reference to the accompanying drawings.
[0051] FIG. 1 is a front view of a blower according to Embodiment 1
of the present invention, as viewed from an outlet opening. FIG. 2
is a cross-sectional view taken along the line A-A of FIG. 1. FIG.
3 is a cross-sectional view taken along the line B-B of FIG. 1,
whose outer circumferential edge is developed into a plane with
lines indicating a position of each part in a bellmouth. FIG. 4 is
an enlarged partial view of FIG. 2. FIG. 5 is the same view as FIG.
3, with the addition of a line illustrating the state of airflow in
the vicinity of an outer circumferential edge of a blade. FIG. 6 is
the same view as FIG. 2, with the addition of lines indicating a
conventional bellmouth for comparison.
[0052] In a blower according to the present embodiment, a propeller
fan 3 having a plurality of blades 1 around a hub 2 is driven by a
fan motor 7. The blade 1 is formed of a joining edge with the hub
2, a leading edge 1a facing a rotational direction, a trailing edge
1b opposed to the leading edge 1a, an outer circumferential edge
1c, which is opposed to the joining edge and connecting the leading
edge 1a and the trailing edge 1b, and a curved surface surrounded
by these joining edges, the leading edge 1a, the trailing edge 1b,
and the outer circumferential edge 1c. The blade 1 has a pressure
surface 1d facing the rotational direction 10 formed at one side
thereof and a negative-pressure surface 1e formed at the other side
thereof. Pf1 is a point at the intersection of the leading edge 1a
with the outer circumferential edge 1c, while Pf2 is a point at the
intersection of the trailing edge 1b with the outer circumferential
edge 1c. The outer circumferential edge 1c has a concave warpage in
the rotational direction, as shown in FIG. 3. Pf3 represents a
maximum warpage position at which the distance between a chord 4
connecting Pf1 and Pf2 and the outer circumferential edge 1c is the
largest.
[0053] In FIGS. 2 and 4, lines of the blade 1 show a rotational
trajectory of the leading edge 1a, the trailing edge 1b, and the
outer circumferential edge 1c. A shaft about which the fan motor 7
and the propeller 3 rotate is referred to as a rotational shaft. A
direction toward the air inlet side of the rotational shaft (the
left side of FIG. 2) is set as an upstream direction of the
rotation shaft, while a direction toward the air outlet side of the
rotational shaft (the right side of FIG. 2) is set as a rotational
downstream direction of the rotation shaft.
[0054] The outer periphery of the air outlet of the blade 1 is
covered with a bellmouth 5. As shown in FIG. 4, the bellmouth 5 is
located so as to cover the entire blade outer circumference or part
of the trailing edge 1b. When classifying characteristics of each
section of the bellmouth 5 by a cross-section shape in the blade
side face, a section between Pb2 and Pb3 is a minimum inner
diameter portion 5b that is the closest to the outer
circumferential edge 1c of the blade 1 so as to cover the trailing
edge 1b of the outer circumference edge 1c of the blade 1. A
section from Pb2 to a Pb1 curves to form a downstream of expanding
portion 5a for expanding an air passage toward the rotational
downstream of the rotation shaft direction, and at Pb1 connects to
a baffle plate 6 for separating an air outlet space .beta. from an
air inlet space .alpha..
[0055] The bellmouth 5 has the following air passage expanding
shape (contraction flow shape as seen from the air flow
direction)in the inlet side direction. The bellmouth 5 has a convex
shaped first upstream expanding portion 5c between Pb3 and Pb4, Pb3
being an upstream end of the rotation shaft of the minimum inner
diameter portion 5b of the bellmouth 5. The bellmouth 5 has a
concave shaped second upstream expanding portion 5d from Pb4 to
Pb5, which follows the first upstream expanding portion 5c. The
second upstream expanding portion 5d has a large curvature in the
vicinity of Pb4, while it has a small curvature in the vicinity of
Pb5, and has a substantially conic section in the vicinity of Pb5.
In addition, the bellmouth 5 has a convex shaped third upstream
expanding portion 5e from Pb5 to Pb6, which follows the second
upstream expanding portion 5d.
[0056] Next, the positional relationship in the rotational shaft
direction between the propeller fan 3 and the bellmouth 5 is
described below with reference to FIGS. 3 and 4. Dashed lines Lb3,
Lb4, Lb5, and Lb6 in FIG. 3 represent positions of Pb3, Pb4, Pb5,
and Pb6 in the rotational shaft direction in the bellmouth 5,
respectively. In FIG. 4, a dashed line Lf3 represents a position in
the rotational direction of the maximum warpage position Pf3 on the
outer circumferential edge 1c of the blade 1. Pb3, the upstream end
of the rotation shaft of the minimum inner diameter portion 5b of
the bellmouth 5, is located upstream of the rotation shaft
direction of the trailing edge end Pb2 in the outer circumferential
edge 1c of the blade 1. Pb4 in the transition portion between the
first upstream expanding portion 5c and the second upstream
expanding portion 5d of the bellmouth 5 is located downstream of
the rotation shaft direction of the maximum warpage position Pf3 on
the outer circumferential edge 1c of the blade 1. In other words, a
position in the rotation shaft direction of the maximum warpage
position Pf3 on the outer circumferential edge 1c of the blade 1 is
included within the range covered by the second upstream expanding
portion 5d.
[0057] The operation of a blower according to the present
embodiment is described using FIGS. 1 to 5.
[0058] In the blower having the structure described above, the
propeller fan 3, when driven by the fan motor 7, sends to the air
outlet space .beta. the air inside a region where the propeller fan
3 rotates and at the same time draws in the air in the air inlet
space .alpha. to the region where the propeller 3 rotates. Gases
enter the propeller fan 3 from the face formed of a rotational
trajectory of the leading edge 1a and the face formed of the
rotational trajectory of the outer circumferential edge 1c. In this
way an air flow from the inlet side space .alpha. to the outlet
side space .beta. takes place.
[0059] As shown in FIG. 5, part of the gas entering the propeller
fan 3 becomes a leak flow 8 to a negative pressure surface 1e from
a pressure surface 1d via the outside of the outer circumferential
edge 1c. A flow having a vortex structure called a blade tip vortex
9 takes place at a position along the outer circumferential edge 1c
of the negative pressure surface 1e, originating from the leak flow
8 occurring in the vicinity of the leading edge of the outer
circumferential edge 1c. The blade tip vortex 9 becomes larger as
it moves toward the trailing edge side from the leading edge side,
and moves away from the outer circumferential edge 1c in the
vicinity of the maximum warpage position Pf3 at which a flow
deflection becomes large. The blade tip vortex 9 having moved away
from the outer circumferential edge 1c is pushed by the entire flow
from the inlet side space .alpha. to the outlet side space .beta.
to gradually proceed to the outlet side space .beta. and is
discharged out of the blower as the structure of the vortex
weakens.
[0060] The positional relationship in the downstream side between
the bellmouth 5 and the outer circumferential edge 1c is described
below. In order for the blower to generate a required flow rate, a
pressure difference should be maintained between the inlet side
space .alpha. and the outlet side space .beta. depending upon the
flow rate. The portion at which the distance between the blade 1
and the bellmouth 5 is smallest is the gap between the minimum
inner diameter portion 5b from Pb2 to Pb3 and the outer
circumferential edge 1c. In the present embodiment, such a gap is
set at a position in the vicinity of the trailing edge 1b of the
outer circumference edge 1c. If the gap is too large, the required
pressure difference and flow rate cannot be attained when there is
a greater air flow resistance before and after the blower.
Accordingly, the present embodiment makes the gap between the
bellmouth 5 and the blade 1 in the vicinity of the trailing edge 1b
of the outer circumferential edge 1c smaller. Preferably, the gap
is about one to three percent of the blade outer diameter (diameter
of a rotation circle of the outer circumferential edge 1c).
[0061] The positional relationship in the upstream side between the
bellmouth 5 and the outer circumferential edge 1c is described
below. As described above, the face composed of the rotational
trajectory of the outer circumferential edge 1c of the blade 1 is
an air inlet face. Receiving incoming flow from a larger inlet area
has an effect to reduce incoming flow speed at the same flow amount
and reduce noise levels. Accordingly, it is preferable to make the
distance between the outer circumferential edge 1c of the blade 1
and the bellmouth 5 sufficiently wide. The outer circumferential
edge 1c of the blade 1 is also a place where the blade tip vortex 9
originates, grows, and moves away. The blade tip vortex 9 has large
turbulence, and, if there is a wall such as a bellmouth 5 in the
vicinity, a pressure change on the wall surface becomes so large
that results in an increase in noise. To prevent these problems, it
is preferable to make the distance between the bellmouth 5 and the
outer circumferential edge 1c of the blade 1 in the upstream side
sufficiently large.
[0062] A blower for practical use, however, it is quite rare that
there is a wide area around the blade 1 in the inlet space .alpha.
and the blade has a circumferentially uniform shape. Air flow to
the blade tends to become circumferentially nonuniform and varies
in terms of time, as seen from the rotating blade 1, causing an
increase in noise. Accordingly, in order to achieve a low-noise
blower, it is preferable to provide a circumferentially uniform air
passage shape. More preferably, the outer circumferential edge 1c
of the blade 1 is covered with the bellmouth 5.
[0063] In order to achieve a low-noise blower while maintaining the
pressure difference between the inlet space .alpha. and the outlet
space .beta., it is preferable to narrow the distance between the
outer circumferential edge 1c of the blade 1 and the bellmouth 5 in
the vicinity of the trailing edge 1b and to secure a wider space at
a position closer to the upstream side to take in more air flow. In
addition, in order to prevent a pressure change on the bellmouth
wall surface resulting from the blade tip vortex 9, it is
preferable while covering the outer circumferential edge 1c of the
blade 1 to widen the distance between the outer circumferential
edge 1c of the blade 1 and the bellmouth 5 to suppress an increase
in noise arising from the nonuniform air passage shape.
[0064] In a blower according to the present embodiment, since
following a convex-shaped first upstream expanding portion 5c
formed upstream of the rotation shaft, there is the concave-shaped
upstream second expanding portion 5d formed upstream of the
rotation shaft, as is evident from FIG. 6, it is found that the
distance between the outer circumference 1c of the blade 1 and the
bellmouth 5 can be made larger while surrounding the outer
circumference 1c of the blade 1 than the upstream expanding shape
in a convex-shaped curved section 11 (shown by dashed line in the
figure) upstream of the rotation shaft from inner diameter minimum
portion conventionally employed in general. This allows more air to
be drawn in from around the outer circumferential edge 1c of the
blade 1, thereby preventing a pressure change in the bellmouth
surface resulting from turbulence by the blade tip vortex 9. In
addition, this allows air passage around the outer circumferential
edge 1c of a blade 1 to be circumferentially uniform, which
suppresses fluctuation of air flow coming into the blade 1, leading
to the achievement of a low-noise blower. Furthermore, this allows
a section from the upstream of the rotation shaft direction of the
second upstream expanding portion 5d to the minimum inner diameter
point Pb3 to form a smoothly continuous shape, which is effective
in suppressing the turbulence of air flow and efficiently reduces
noise.
[0065] Furthermore, the second upstream expanding portion 5d has a
large curvature close to the first upstream expanding portion 5c
and a smaller curvature at more upstream position and has a
substantially conic section at the upstream portion, which allows
for a wider opening area upstream of the rotation shaft of the
second upstream expanding portion 5d, thereby guiding a large
amount of air flow to the space between the outer circumferential
edge 1c and the bellmouth 5. This enables a large-air-capacity,
low-noise blower to be implemented. In addition to the second
upstream expanding portion 5d, the blower has a convex-shaped third
upstream expanding portion 5e upstream of the rotation shaft. The
blower allows air entering from the end of the bellmouth to follow
the third upstream expanding portion 5e for reduction in turbulence
and guides it to the blade 1. As a result, a much lower-noise
blower can be obtained.
[0066] An advantage of the relationship between the warpage of the
outer circumferential edge 1c of the blade 1 and the expanded shape
of the bellmouth 5 in the blower according to the present
embodiment is described below. The blade tip vortex 9 undergoes
significant fluctuation in the vicinity of the maximum warpage
where the blade tip vortex grows and moves away, having great
influence on a pressure change on the bellmouth wall surface. Here,
the bellmouth 5 has the transition point Pb4 between the first
upstream expanding portion 5c and the second upstream expanding
portion 5d located downstream of the maximum warpage position Pf3
on the outer circumferential edge 1c of the blade 1, which results
in a large distance between the outer circumferential edge 1c of
the blade 1 and the bellmouth 5 in the vicinity of the maximum
warpage point Pf3, thereby suppressing a pressure change on the
bellmouth wall surface.
[0067] In addition, the location in the rotation shaft direction of
the maximum warpage point Pf3 on the outer circumferential edge 1c
of the blade 1 falls within the range covered by the second
upstream expanding portion 5d, which reduces turbulent air flow
around the blade tip vortex 9 when it moves away and also reduces
the turbulence of the blade tip vortex 9, thereby suppressing the
noise caused by the moving blade tip vortex 9.
[0068] Descriptions will be given to the case when the location in
the rotation shaft direction of the maximum warpage point Pf3 on
the outer circumferential edge 1c of the blade 1 falls within the
range covered by the second upstream expanding portion 5d. A
similar advantage is also provided when the maximum warpage point
Pf3 is located within the range covered by the third upstream
expanding portion 5e.
Embodiment 2
[0069] FIGS. 7 and 8 show a heat pump apparatus, namely an air
conditioning apparatus according to Embodiment 2 of the present
invention. FIG. 7(a) is a front view of a box-shaped outdoor unit
of an air conditioning apparatus, while FIG. 7(b) is a
cross-section taken along the line C-C of FIG. 7(a). FIG. 8 is a
view showing the direction of air passage, as seen from the
rotation shaft. The reference numerals and symbols in FIG. 7 refer
to the same components as those with the same numerals and symbols
in the above-described Embodiment 1. Reference is also made to
FIGS. 1 to 6 when describing a blower.
[0070] An air conditioning apparatus, namely, a box-shaped outdoor
unit 12 according to the present embodiment includes an air outlet
face 13 formed in the front face, an air inlet face 14 formed at
two faces including its opposite face (back face) and one face on
the left-hand side, and a L-shaped heat exchanger 15 disposed so as
to cover the air inlet face 14. A blower is disposed close to the
heat exchanger 15. Such a blower includes a blower according to
above described Embodiment 1. The heat exchanger 15 includes a pipe
having a multilayer fin for heat dissipation formed on an outer
surface thereof, the pipe having a refrigerant circulating
thereinside. The heat exchanger 15 does not necessarily have an
L-shaped form, and may be provided on a back face only. In such a
case, the side surrounding the air outlet face 13 on the box-shaped
unit is formed of a plurality of side plates.
[0071] A grill 16 is disposed downstream of the rotation shaft of
the blower, which protects a propeller fan 3 or protects a person
from the rotating propeller fan 3. The air outlet face 13 and the
bellmouth 5 are surrounded by the heat exchanger 15, top plate 17,
bottom plate 18, and separating plate 22. The separating plate 22
separates an inboard air passage chamber 19 housing the blower
inside the outdoor unit 12 from a compressor chamber 21 housing a
compressor 20.
[0072] As shown in FIG. 3, a blade 1 of the propeller fan 3 has a
concave-shaped warpage in the outer circumferential edge 1c in the
rotational direction 10. As described in FIG. 4, with the bellmouth
5 surrounding the entire periphery side of the blade or trailing
edge side of the propeller fan 3, a minimum inner diameter portion
5b having the shortest distance with the outer circumferential edge
1c of the blade 1 in the section from Pb2 to Pb3, covers a trailing
edge 1b of the outer circumferential edge 1c in any of directions
(i) to (viii) shown in FIG. 8. A downstream expanding portion 5a is
provided whose air passage bends at a section from Pb2 to Pb1 to
expand in the rotation shaft downstream direction. The air passage
expanding shape (contraction flow shape as seen from the air flow
direction) in the inlet direction includes a convex shaped first
upstream expanding portion 5c between Pb3 and Pb4, Pb3 being an end
point of upstream direction of the rotation shaft of the minimum
inner diameter portion 5b. Also, the bellmouth 5 has a concave
shaped second upstream expanding portion 5d from Pb4 to Pb5
upstream of the rotation shaft, which follows the first upstream
expanding portion 5c. The second upstream expanding portion 5d has
a large curvature in the vicinity of Pb4, while it has a small
curvature in the vicinity of Pb5, and has a substantially conic
section in the vicinity of Pb5, which is an upstream portion.
Furthermore, the bellmouth 5 has a convex shaped third upstream
expanding portion 5e in a section from Pb5 to Pb6, which follows
the second upstream expanding portion 5d.
[0073] As described in FIG. 4, in the rotation shaft direction of
the propeller fan 3 and the bellmouth 5, Pb3, an upstream end of
the minimum inner diameter portion 5b of the bellmouth 5 in the
rotation shaft direction, is located upstream of the rotation shaft
direction of the trailing edge end Pb2 in the outer circumferential
edge 1c of the blade 1. Pb4 in the transition between the first
upstream expanding portion 5c and the second upstream expanding
portion 5d is located downstream of the rotation shaft of the
maximum warpage position Pf3 on the outer circumferential edge 1c
of the blade 1. In other words, a position in the rotation shaft
direction of the maximum warpage position Pf3 on the outer
circumferential edge 1c of the blade 1 falls within the range
covered by the second upstream expanding portion 5d.
[0074] An air conditioning apparatus, namely an outdoor unit 12
according to the present embodiment is described with regard to
operation. When driven by the fan motor 7, the propeller fan 3
rotates to send the air inside the inboard air passage chamber 19,
a region where the propeller fan 3 rotates, from the air outlet
face 13 to the air outlet space .beta., and at the same time draws
in the air in the air inlet space .alpha. from the air inlet face
14 through the fin of the heat exchanger 15, which enters the
inboard air passage chamber 19 where the propeller fan 3 rotates.
The heat exchanger 15 include a refrigerant having higher or lower
temperature than the gas outside the exchanger circulating
thereinside, providing heat exchange when the air outside the
exchanger 15 passes therethrough. The air, which becomes warmer or
colder after undergoing heat exchange by the heat exchanger 15 when
entering the inboard air passage chamber 19, is blown out to the
outside with the rotating propeller fan 3.
[0075] Air flow around the blade of the propeller fan 3 behaves in
the same manner as that in Embodiment 1. That is, as shown in FIG.
5, part of the air entering the propeller fan 3 becomes a leak flow
8 to the negative pressure surface 1e from the pressure surface 1d
via the outside of the outer circumferential edge 1c. A blade tip
vortex 9 takes place at a position along the outer circumferential
edge 1c of the negative pressure surface 1e, originating from the
leak flow 8 occurring in the vicinity of the leading edge of the
outer circumferential surface 1c. The blade tip vortex 9 grows as
it transits to the trailing edge side from the leading edge side,
and moves away from the outer circumferential edge 1c of the blade
in the vicinity of the maximum warpage position Pf3 at which a flow
deflection becomes large. The blade tip vortex 9 that left the
outer circumferential edge 1c is pushed by an entire flow from the
inboard air passage chamber 19 to the outside of the unit and is
discharged out of the blower through the air outlet face 13, while
weakening its vortex structure.
[0076] As described above, since an air conditioning apparatus
according to the present embodiment employs the blower described
above in Embodiment 1 as a blower for promoting heat exchanger by
the heat exchanger 15 in the outdoor unit 12, it is characterized
by the shape of the bellmouth 15 around the propeller fan 3 and the
positional relationship between the propeller fan 3 and the
bellmouth 5. Accordingly, in the same way as with the above
described Embodiment 1, a great amount of air can be drawn in from
the outer circumferential edge 1c of the blade 1 of the blower,
which suppresses a pressure change on the surface of the bellmouth
5 arising from turbulence of the blade tip vortex 9. In addition,
air passage around the outer circumferential edge 1c of the blade 1
can be circumferentially homogenized, which helps to suppress
fluctuation of air entering the blade 1, leading to the achievement
of a lower-noise blower.
[0077] A section between the upstream side of the rotation shaft of
the second upstream expanding portion 5d and the Minimum inner
diameter point Pb3 can be constructed into a smoothly continued
shape, which effectively suppresses turbulent of air flow and
efficiently reduces noise. In particular, in a box-shaped outdoor
unit 12, the distance to the end of air passage except the
bellmouth 5 seen from the blade 1 is small, for example, in the
direction of (i), (iii), (v), or (vii) in FIG. 8 and large in the
direction of (ii), (iv), (vi), or (viii). An outdoor unit employing
a conventional blower which has no sufficient distance between the
bellmouth 5 and the maximum warpage position Pf3 on the outer
circumferential edge 1c of the blade 1 experiences significant
fluctuation in incoming flow and the blade tip vortex 9 due to the
change in air passage distance resulting from the rotation position
of the blade 1. However the outdoor unit 12 employing a blower
according to the present embodiment having a sufficient distance
between the bellmouth 5 and the maximum warpage position Pf3 on the
outer circumferential edge 1c of the blade 1 is capable of
preventing fluctuation of incoming flow of the air passage distance
resulting from the rotation position of the blade 1, leading to a
significant reduction in noise.
[0078] Also, a change in air flow at the rotational position of the
blade 1 can be reduced, which results in reduction of a change of
force exerted by the propeller fan 3 on the fan motor 7, leading to
reduction of bearing wear or shaft deflection of the fan motor 7.
This prolongs the durability of the outdoor unit 12 and helps to
achieve the outdoor unit 12 that provides a stable quality during a
long period of service.
Embodiment 3
[0079] In the above-described Embodiment 2, an air conditioning
apparatus as a heat pump is described which has a bellmouth 5
around a propeller fan 3, the bellmouth 5 having a second upstream
expanding portion 5d formed at the circumferential surface thereof
and a third upstream expanding portion 5e formed upstream of the
second upstream expanding portion 5d. An objective of the present
invention can also be achieved by forming the second upstream
expanding portion 5d and the third upstream expanding portion 5e
only at a portion where the distance to the end of an air flow
passage other than the bellmouth 5 seen from the blade 1 rapidly
changes in the circumferential direction, for example, a portion
(having a long distance to the end of the air flow passage)
corresponding to a corner of a box-shaped outdoor unit 12. An
outdoor unit 12 of a heat pump apparatus, namely an air
conditioning apparatus having an upstream portion including the
second upstream expanding portion 5d formed only in some portions
of the circumferential direction of the bellmouth 5 is described
below with reference to FIGS. 9 to 11.
[0080] FIG. 9(a) is a front view of an outdoor unit of an air
conditioning apparatus according to Embodiment 3 of the present
invention. FIG. 9(b) is a cross-sectional view taken along the line
D-D including its rotation shaft. FIG. 9(c) is a cross-sectional
view taken along the line E-E. FIG. 10 is a view showing the
direction of an air passage, as seen from the rotational shaft.
FIG. 11 is a partially enlarged cross-sectional view of a main
section of a bellmouth and a propeller fan, as seen from an inlet
side. In each figure the same reference numerals and symbols are
given to the same parts in Embodiments 1 and 2. Reference is also
made to FIGS. 1 to 6 to describe below a blower.
[0081] An air conditioning apparatus, namely a box-shaped outdoor
unit 12 according to the present embodiment includes a blade 1 of a
propeller fan 3 of its blower having a concave-shaped warpage (see
FIG. 3) formed at the circumferential edge 1c thereof so as to warp
in a rotational direction 10.
[0082] As shown in FIG. 9(a), the bellmouth 5 surrounding the
entire periphery or the trailing edge of the propeller fan 3 has
its upstream portion terminated at a first upstream expanding
portion 5c (see FIG. 4) in a portion extending in any of directions
(i), (iii), (v), and (vii) as shown in FIG. 10, namely in a portion
having a smaller distance to an air flow passage other than the
bellmouth 5. In contrast, the bellmouth 5 has a minimum inner
diameter portion 5b being face-to-face with the trailing edge 1b of
the outer circumferential edge 1c in a portion defined by lines
extending in the directions of (ii) and (iv) in a section
consisting of a separating plate 22, a top plate 17, and a bottom
plate 18 and in a portion defined by lines extending in the
directions of (vi) and (viii) in a section consisting of a heat
exchanger 15, the bottom plate 18, and the top plate 17, the
minimum inner diameter portion 5b being the closest to the outer
circumferential edge 1c of the blade 1 in a section from Pb2 to
Pb3, as described in Embodiment 1 with reference to, for example,
FIG. 4. The bellmouth 5 has a downstream expanding portion 5a
formed at a section from Pb2 to Pb1 so as to expand the air passage
in the rotational shaft upstream direction. The air passage
expanding shape (contraction flow shape as seen from the air flow
direction) in the air inlet direction includes a convex shaped
first upstream expanding portion 5c upstream of the rotation shaft
between Pb3 and Pb4, Pb3 being an upstream end of the minimum inner
diameter portion 5b. Also, the bellmouth 5 has a concave shaped
second upstream expanding portion 5d from Pb4 to Pb5, which follows
the first upstream expanding portion 5c. The second upstream
expanding portion 5d has a large curvature in the vicinity of Pb4,
while it has a small curvature in the vicinity of Pb5, and has a
substantially conic section in the vicinity of Pb5. Furthermore,
the bellmouth 5 has a convex shaped third upstream expanding
portion 5e in a section from Pb5 to Pb6, which follows the second
upstream expanding portion 5d.
[0083] As described in Embodiment 1, in the rotation shaft
direction of the propeller fan 3 and the bellmouth 5, Pb3, an
upstream end of the minimum inner diameter portion 5b, is located
upstream of the trailing edge end Pb2 in the outer circumferential
edge 1c in any of directions of (ii), (iv), (vi), and (viii). Pb4
in the transition between the first upstream expanding portion 5c
and the second upstream expanding portion 5d is located downstream
of the rotation shaft direction of the maximum warpage position Pf3
on the outer circumferential edge 1c of the blade 1. A position in
the rotation shaft direction of the maximum warpage position Pf3 on
the outer circumferential edge 1c of the blade 1 falls within the
range covered by the second upstream expanding portion 5d.
[0084] An air conditioning apparatus according to the present
embodiment that is an outdoor unit 12 is also characterized by the
shape of the bellmouth 15 around the propeller fan 3 and the
positional relationship between the propeller fan 3 and the
bellmouth 5. Accordingly, as with the above described Embodiments 1
and 2, a great amount of air can be drawn in from the outer
circumferential edge 1c of a blade 1 of a blower, which suppresses
a pressure change on the surface of the bellmouth 5 arising from
turbulence of the blade tip vortex 9.
[0085] A section between the upstream side of the second upstream
expanding portion 5d and the minimum inner diameter point Pb3 can
be constructed with a smoothly continued surface, which effectively
suppresses turbulent air flow and efficiently reduces noise. In
particular, in an outdoor unit 12, the second upstream expanding
portion 5d and the third upstream expanding portion 5e cover the
periphery of the blade in any of directions (ii), (iv), (vi), and
(viii) as shown in FIG. 8 where a distance to an air flow passage
other than the bellmouth 5 rapidly changes in the circumferential
direction, thereby efficiently suppressing the fluctuation of
incoming air flow and the blade tip vertex 9 as well as attaining
reduction in noise.
[0086] Also, a change in air flow at the rotational position of the
blade 1 can be reduced, which results in reduction of a change of
force exerted by the propeller fan 3 on the fan motor 7, leading to
reduction of bearing wear or shaft deflection of the fan motor 7.
This prolongs the durability of the outdoor unit 12 and helps to
achieve the outdoor unit 12 that provides a stable quality during a
long period of service.
[0087] Since in the present embodiment, an upstream portion of the
bellmouth 5 including the second upstream expanding portion 5d
exists only at a part of the periphery direction of the outer
circumferential edge 1c, the effect of suppressing fluctuation of
incoming air flow or the blade tip vortex 9 is reduced compared
with above-described Embodiment 2 where such a upstream portion is
provided around the entire periphery. Instead, the diameter of the
propeller fan 3 can be large. A propeller fan 3 having an increased
diameter reduces the revolution of the fan for a required amount of
air, leading to reduced noise. In addition, an increased-diameter
fan reduces the velocity of air flow blown out by the propeller fan
3 and passing through the grill 16, leading to a reduction in noise
emissions caused by the grill 16. So that low noise outdoor unit 12
can be obtained
[0088] Also, reduced velocity of air flow passing through the grill
16 results in reduced air flow resistance of the grill 16, leading
to electric power saving as well as the achievement of an highly
energy-saving outdoor unit 12. Furthermore, reduced air flow
resistance of the grill 16 leads to a reduction in a required
pressure boost, resulting in reduction in noise emissions from the
propeller fan 3 and resultant lower-noise outdoor unit 12.
[0089] As shown in FIG. 11 depicting a cross-section perpendicular
to the rotation shaft in the second upstream expanding portion 5d,
the bellmouth 5 has a convex-shaped end warpage 23 formed at both
circumferential ends of the second upstream expanding portion 5d in
the rotation shaft direction. This makes continuously smooth a
transitional section between the second upstream expanding portion
5d and a portion where no such portion is found, for example,
between the direction of (vii) and that of (viii), or between the
direction of (viii) and that of (I), thereby suppressing the
fluctuation due to separation of the air flow coming into the
bellmouth 5 in these transitional section, so that low noise effect
can be easily obtained.
Embodiment 4
[0090] FIG. 12(a) is a front view of a rectangular box-shaped
outdoor unit of a heat pump water heater according to Embodiment 4
of the present invention. FIG. 12(b) is a horizontal
cross-sectional view including a rotation shaft taken along the
line F-F. FIG. 12(c) is a cross-sectional view including a rotation
shaft taken along the line G-G. The reference numerals and symbols
in FIG. 12 refer to the same components as those in Embodiments 1
and 3. Reference is also made to FIGS. 1 to 6 to provide
descriptions on the blower.
[0091] In a heat pump water heater, namely a rectangular box-shaped
outdoor unit 25 according to the present embodiment, its blower has
the same structure as in Embodiment 3. Accordingly, descriptions on
the blower are omitted, and differences in structure from those in
Embodiment 3 are described below. As shown in FIG. 12, the heat
pump water heater according to the present embodiment has an outlet
face 13 provided in the front of the outdoor unit 25, an external
air inlet face 14 provided in two faces, that is, its opposing face
(back face) and a face of the left-hand side of the figure, and an
L-shaped heat exchanger 15 is disposed so as to cover the air inlet
face 14. Also, a water heat exchanger 24 for performing heat
exchange between a refrigerant and water is provided at the bottom
of the inboard air passage chamber 19. The water heat exchanger 24
occupies the bottom of the inboard air passage chamber 19. When
viewed from the propeller fan 3, the top plate 24a of the water
heat exchanger 24 is replaced by the bottom plate 18 in Embodiment
3. Therefore, the outdoor unit 25 of a heat pump water heater
according to the present embodiment also provides the same
advantages and effects as the blower described in Embodiment 3,
leading to the implementation of the outdoor unit 25 which provides
low-noise and, preserves quality for a long period of time.
Embodiment 5
[0092] In addition to features described in Embodiment 1, a blower
according to the present embodiment is characterized in that a
circumferential edge of the blade 1 is warped toward an inlet side
(.alpha.) from an outlet side (.beta.). The shape of such a
circumferential edge is described below in terms of the warpage
toward the inlet side from the outlet side. Features of a bellmouth
5 except the shape of the blade, the relative position of a
propeller fan 3 and bellmouth 5, and the structure with a fan motor
7 are the same as Embodiment 1. Accordingly, reference is also made
to FIGS. 1 to 6 to provide a description on the blower.
[0093] FIG. 13 is an enlarged view, equivalent to FIG. 4, of a main
section of a blower according to Embodiment 5 of the present
invention, where dashed lines Ld1 to Ld11 are dividing meridians
obtained by equally dividing a radial section of a blade with the
rotation shaft being the center and rotating lines that connect
divided points from hub side to an outer circumference side about
the rotational shaft to project the dividing points to a plane
containing the rotation shaft. The outer circumference side is
shown. FIG. 13 shows 12 divisions ranging from the leading edge to
the trailing edge. The dividing meridian is warped in front and at
the back of a line Lf4 drawn in the outer circumferential edge of a
blade in such a manner that the outer circumferential edge curves
toward an inlet side (inlet space .alpha.) from an outlet side
(outlet space .beta.). Such a warpage shown in FIG. 13 is becoming
greater at in the middle between the leading edge and the trailing
edge, Ld5 to Ld7, and is gradually becoming smaller toward the
leading edge or the trailing edge, while no warpage is found at a
leading edge 1a and a trailing edge 1b (represented as meridian in
FIG. 13) that are ends of the dividing meridian.
[0094] A blower provided with a propeller fan 3 according to the
present embodiment having a blade outer circumferential edge warped
toward the inlet side is described below in terms of its operation.
As described above, the propeller fan 3, when driven by the fan
motor 7, sends to the air outlet space .beta. the air inside a
region where the propeller fan 3 rotates and at the same time draws
in the air in the air inlet space .alpha. to the region where the
propeller 3 rotates through surfaces defined by a leading edge 1a
or an outer circumferential edge 1c when a blade is rotating.
[0095] Like FIG. 5, FIG. 14 is a view of an outer circumferential
edge of a blade, with the addition of leader lines indicating the
state of air flow in the vicinity of the outer circumferential edge
of the blade. As shown in FIG. 14, part of the air entering the
propeller fan 3 becomes a leak flow 8 to the negative pressure
surface 1e from the pressure surface 1d via the outside of the
outer circumferential edge 1c. In the present embodiment, the outer
circumferential edge of a blade is warped toward an inlet side,
which reduces the pressure difference between the pressure surface
1d and the negative pressure surface 1e in the outer
circumferential edge 1c as well as makes smooth the leak flow 8
coming into the negative pressure surface 1e from the pressure
surface 1d. Accordingly, a blade tip vortex 9 occurring at a
position along the outer circumferential edge is on the negative
pressure surface 1e, originating from the leak flow 8 occurring in
the vicinity of the leading edge of the outer circumferential
surface 1c, has a higher central pressure than those with no warped
outer circumferential edge made toward an inlet side, which causes
the vortex to be weaker.
[0096] The blade tip vortex 9 grows as it transits to the trailing
edge side 1b from the leading edge side 1a, and moves away from the
outer circumferential edge 1c of the blade 1 at the maximum warpage
position Pf3 at which a flow deflection becomes large. The blade
tip vortex 9 that left the outer circumferential edge 1c is pushed
by an entire flow from the inlet space .alpha. to the outlet space
.beta. and is discharged out of the blower, while it is weakening
in vortex structure.
[0097] The vortex that left the outer circumferential edge 1c
interferes with the bellmouth 5 and an adjacent blade causing noise
emissions and impedes air flow from the inlet space .alpha. to the
outlet space .beta.. For this reasons, fan rotating speeds is
increased to obtain a required amount of air volume and pressure,
increasing in noise emissions. Like the present embodiment, the
blade outer circumferential edge is warped toward an upstream side,
thereby weakening the blade tip vortex 9 and suppressing increased
noise level caused by the blade tip vortex 9.
[0098] However, the blade tip vortex 9 becomes unstable such that
its position and vortex diameter are easily changed although it is
weak as a vortex due to its relatively high central when the outer
circumferential edge of the blade is warped toward the inlet side.
For this reason, a conventional bellmouth 25 having only a first
upstream expanding portion as shown in FIG. 15 cannot sufficiently
obtain effects. As described above, actual blowers rarely have a
wide area around the blade 1 in the air inlet space a and a
circumferentially uniform shape. A bellmouth 24 having a small
first expanding portion indicated by a solid line is susceptible to
fluctuation in the periphery, causing the weak, unstable blade tip
vortex 9 to further become unstable, which disturbs a flowing path
and induces noise emissions. In contrast, in the case of the
bellmouth 25 having a large first expanding portion indicated by
dashed-dotted lines an influence of fluctuations in the periphery
of the outer circumferential edge is mitigated. However, due to a
narrow air passage from the outer circumferential edge 1c, air flow
coming from the outer circumferential edge 1c declines at the
upstream side of the rotation shaft direction, and at the same time
a leak flow 8 from the pressure surface 1d to the negative pressure
surface 1e also declines, resulting in a narrower region where the
blade tip vortex 9 grows. Accordingly, if the warped outer
circumferential edge technique according to the present invention
is applied to this case, the blade tip vortex 9 becomes weak and
therefore moves away from the blade earlier. This tends to cause
interfere with the bellmouth and its adjacent blade and expand a
disturbance in the flowing path, resulting in increased noise
emissions. As described above, a combination of a conventional
bellmouth and a propeller fan having warped outer circumferential
edges cannot achieve maximum noise reduction effects.
[0099] As shown in FIG. 15 using dashed lines, in a blower
according to the present embodiment having a convex-shaped first
upstream expanding portion and a concave-shaped second upstream
expanding portion formed at the upstream side of the rotation
shaft, the bellmouth 5 covers area of the outer circumferential
edge 1c of the blade 1 and provides a greater distance to the outer
circumferential edge 1c of the blade 1 than a conventional
bellmouth indicated by solid lines or dashed-dotted lines. This
makes circumferentially uniform air passage around the outer
circumferential edge 1c of the blade 1, thereby suppressing
fluctuations of the air flow coming into the blade 1 and unstable
blade tip vortex as well as allowing more air flow to be taken in
from the outer circumferential edge 1c of the blade 1 and
preventing the blade tip vortex 9 from moving away. Consequently, a
propeller fan 3 having the warped blade outer circumferential edge
can effectively achieve noise reduction effects, leading to the
achievement of a low-noise blower.
[0100] The warpage of the outer circumferential edge made toward
the inlet side from the outlet side, as shown in FIG. 13, is
becoming greater in the middle between the leading edge 1a and the
trailing edge 1b and is gradually becoming smaller toward the
trailing edge 1b, while no warpage is found at the trailing edge
1b, an end of the dividing meridian. As described above, the
bellmouth 5 causes less air flow to come from the outer
circumferential edge 1c of the blade 1, and the less warped outer
circumferential edge at the trailing edge 1b where there is less
leak flow 8 where the blade tip vortex 9 originates and grows
results in a greater turning angle at an outer circumferential edge
having a high circumferential velocity, thereby effectively
heightening blade boosting. This reduces the rotating speed for a
required amount of air volume and pressure, resulting in a
reduction in relative velocity of air flow on the blade surface.
Such a reduction in relative velocity of air flow on the blade
surface means a reduction in pressure change which causes noise
emissions, leading to the achievement of a low-noise blower.
Embodiment 6
[0101] A heat pump apparatus, for example, an air conditioning
apparatus is described with reference to FIGS. 7 and 8 provided
with a blower, with a blade outer circumferential edge of a
propeller fan 3 being warped toward an inlet side from an outlet
side, having a second upstream expanding portion 5d along the
entire circumference in the circumference direction continuously
upstream of the first upstream expanding portion of the bellmouth
5. Reference to FIGS. 1 to 6 is made to describe the blower.
[0102] An air conditioning apparatus to which a blower according to
the present embodiment is applied has the same structure and
operation as those described in Embodiment 2, and provides the same
advantages and effects as those in Embodiment 2. Accordingly,
descriptions provided below are mainly regarding warped outer
circumferential edge of a blade 1 of the propeller fan 3.
[0103] As described above, a conventional bellmouth structure
cannot provide sufficient effect even if the blade 1 of the
propeller fan 3 has a warped outer circumferential edge toward the
inlet side. In particular, when installed in a heat pump apparatus
such as an air conditioning apparatus, a conventional bellmouth
structure has difficulties in providing noise reduction effect
resulting from a blade having a warped outer circumferential edge,
due to low circumferential uniformity in air passages at the
periphery of the blade circumferential edge.
[0104] An air conditioning apparatus according to the present
embodiment includes a bellmouth that has a first upstream expanding
portion and a second upstream expanding portion provided at the
entire circumference thereof and a propeller fan 3 that has an
outer circumferential edge of its blade 1 warped toward an air
inlet side, which suppresses the effect of non-uniform air passage
around the outer circumferential edge and ensures the entry of air
from the outer circumferential edge 1c as well as weakens a blade
tip vortex 9 and achieves noise reduction effects, leading to the
achievement of a low-noise heat pump apparatus.
Embodiment 7
[0105] Descriptions will be given to a heat pump apparatus, for
example, an air conditioning apparatus provided with a propeller
fan 3 having a outer circumferential edge of its blade warped
toward an inlet side from an outlet side and a second upstream
expanding portion 5d formed along part of the circumference
continuously upstream side of the first upstream expanding portion
5c, Reference to FIGS. 1 to 6 is made to describe the blower.
[0106] An air conditioning apparatus to which a blower according to
the present embodiment is applied has the same structure and
operation as those described in Embodiment 3 using FIGS. 10 and 11,
and provides the same advantages and effects of Embodiment 3.
Accordingly, descriptions provided below are mainly regarding
warping outer circumferential edge of a blade 1 of the propeller
fan 3 toward the inlet side.
[0107] As described above, a conventional bellmouth structure
cannot achieve sufficient effects even if a blade 1 of a propeller
fan 3 has a warped outer circumferential edge toward the inlet
side. In particular, when installed in a heat pump apparatus such
as an air conditioning apparatus, uniformity is low in the air
passage around the outer circumferential edge of the blade. When
adopting a large outer diameter of the fan, the distance between
ambient faces and the blade becomes small, so that it is difficult
to obtain low noise effect in the case of warping the outer
circumferential edge of the blade toward the inlet side.
[0108] An air conditioning apparatus according to the present
embodiment includes a bellmouth that has a first upstream expanding
portion and a second upstream expanding portion provided at a
location in which there is a significant change in distance between
the blade and the surface of the apparatus, as viewed from the
rotating blade, which effectively suppresses the effect of
un-uniform air passage of the outer circumferential edge and
ensures the entry of air from the outer circumferential edge 1c as
well as weakens a blade tip vortex 9 and achieves noise reduction
effects, leading to the achievement of a low-noise heat pump
apparatus.
[0109] FIGS. 16 and 17 are graphs showing the relationship of air
volume and aerodynamic noise level by combining cases of an outdoor
unit of an air conditioning apparatus having a blade 1 of a
propeller fan 3 with and without a warped outer circumferential
edge, second upstream expanding portion upstream of the bellmouth
first upstream expanding portion in a corner consisting of a
separation plate, a top plate, and a bottom plate of the outdoor
unit, and those having a conventional bellmouth. The outer
circumferential edge of a blade 1 has a different shape between
FIG. 16 and FIG. 17. Blade shapes in FIGS. 16 and 17 are
hereinafter referred to as propeller fan A and propeller fan B,
respectively.
[0110] Warpage of the propeller fan A and the propeller fan B is
concretely described below. FIG. 18 shows dividing meridians, like
those in FIG. 13. A .theta. being an angular difference between
before and after the inclination of the dividing meridian changes,
in the propeller fan A, .theta. at a dividing meridian in the
middle of the leading edge 1a and the trailing edge 1b, that is, a
dividing meridian Ld6 in FIG. 18 is set at a maximum of about 14
degrees. In the propeller fan B, .theta. at a dividing meridian
closer to the leading edge 1a, that is, a dividing meridian Ld4 in
FIG. 18 is set at a maximum of about 14 degrees. Radius position
which is a base point where the gradient of the dividing meridian
changes is specified as 85% radius of the outer circumferential
diameter for both fans. The maximum .theta. value (about 14
degrees) is obtained after various tests are conducted and
preferably approximately 14 degrees. FIG. 19 is a development view
of the outer circumferential edge of a blade 1. Warpage ratio is
defined as D divided by L, where D is a maximum distance between
the blade chord and the blade and L is the length of the chord.
Warpage ratio is set to 5.8 percent at a position 85 percent of the
radius and to 8.7 percent at a position of the outer diameter.
[0111] Both of FIGS. 16 and 17 shows that a bellmouth having a
second upstream expanding portion provides more noise reduction
than a conventional bellmouth in the case where no warpage is
formed in the outer circumferential edge of a blade. In the case
where a warpage is formed in the outer circumferential edge of a
blade toward the inlet side, the conventional bellmouth provides
nearly no noise reduction for an outdoor unit, while a bellmouth
having a second upstream expanding portion provides a significant
noise reduction.
INDUSTRIAL APPLICABILITY
[0112] An outdoor unit 12 of an air conditioning apparatus and an
outdoor unit 25 of a heat pump water heater are described above as
an example of applications of a blower according to the present
invention. The blower according to the present invention can be
widely used in other various types of apparatuses (for example, a
ventilating fan) and facilities which are provided with a
blower.
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