Technical Field
[0001] The present invention relates to an outdoor unit and the like that each include an
air-sending device including a propeller fan and a bellmouth.
Background Art
[0002] There is an air-sending device (fan unit) that sends air (that performs cooling,
heat exhaust, and so forth) while producing a flow of air by rotating a propeller
fan having blades (a propeller). Such an air-sending device including a propeller
fan is applied to a wide variety of fields such as outdoor devices (outdoor units)
for refrigeration and air-conditioning apparatuses, refrigerators, electric fans,
and cooling devices for computers and the like.
[0003] Some of such air-sending devices each include, for example, a bellmouth with a wall
extending in the direction of rotation of the propeller fan. Such a bellmouth generally
has an opening spreading outward so that air is blown out smoothly (see Patent Literatures
1 and 2, for example).
Citation List
Patent Literature
[0004]
Patent Literature 1: Japanese Patent No. 3087876
Patent Literature 2: Japanese Patent No. 3199931
Summary of Invention
Technical Problem
[0005] For example, in the air-sending device described above in which the opening simply
spreads outward, sound regarded as noise increases and the fan efficiency is reduced.
For example, in a case where the above air-sending device is provided in an outdoor
unit of an air-conditioning apparatus, noise from the outdoor unit generated with
the rotation of the propeller fan may annoy neighborhood residents. Therefore, there
is a need to reduce noise of outdoor unit. Meanwhile, in recent years, there have
been a need for air-conditioning apparatuses having high energy efficiency for prevention
of global warming. To achieve high energy efficiency, measures such as increasing
the air flow rate of the outdoor unit is effective. Basically, however, noise increases
with the air flow rate. Moreover, air-conditioning apparatuses or the like are typically
operated without any stoppage or for a long time. Therefore, it is also important
to reduce power consumed by the air-sending device itself.
[0006] In view of the above, it is an object of the present invention to provide an outdoor
unit of a refrigeration cycle apparatus and the like, the outdoor unit and the like
each including an air-sending device in which the generation of noise and the increase
in power consumption are further suppressed.
Solution to Problem
[0007] An air-sending device of an outdoor unit according to the present invention includes
a propeller fan that rotates about a rotation axis extending in a direction of gravity
and includes a plurality of blades that produce a flow of gas in a direction opposite
to the direction of gravity, and a bellmouth for rectifying the gas, the bellmouth
having an annular wall extending in a direction of rotation of the blades of the propeller
fan on an outer side with respect to outer peripheral edges of the blades. The bellmouth
has a wall forming a sloping surface extending such that an air passage on an outlet
side spreads outward. The bellmouth has a shape satisfying conditions represented
as a relationship of H/D ≥ 0.04 between a length H of the sloping surface in a direction
of the rotation axis from an end on an inlet side to an end on the outlet side and
a fan diameter D of the propeller fan, a relationship of 0 < θ ≤ 60° for an angle
θ formed between a line connecting the ends of the sloping surface and the rotation
axis, and a relationship of L/L0 ≥ 0.5 between a length L in the direction of the
rotation axis from an opening on the inlet side to the end of the sloping surface
on the inlet side and a length L0 of the blades of the propeller fan in the direction
of the rotational axis.
Advantageous Effects of Invention
[0008] In the air-sending device of an outdoor unit according to the present invention,
the bellmouth has the sloping surface extending such that the air passage on the outlet
side spreads outward. Furthermore, with respect to the propeller fan, the bellmouth
has a shape satisfying the relationships of L/L0 ≥ 0.5, 0 < θ ≤ 60°, and H/D ≥ 0.04.
Therefore, the relationship between the static pressure and the air flow rate on an
open side can be made closer to the relationship between the static pressure and the
air flow rate in a surging zone without increasing the fan diameter. This, for example,
reduces the differences between the specific noise level and the fan efficiency at
an operating point in an operation at the highest air flow rate and the smallest specific
noise level and the highest fan efficiency, respectively. Thus, input to the fan and
noise can be reduced.
Brief Description of Drawings
[0009]
[Fig. 1] Fig. 1 is a diagram illustrating an outline of an air-sending device according
to Embodiment 1 of the present invention.
[Fig. 2] Fig. 2 is a graph illustrating a P-Q characteristic and a Ks-Q characteristic
of a propeller fan 1 alone.
[Fig. 3] Fig. 3 is a graph illustrating the P-Q characteristic and an η-Q characteristic
of the propeller fan 1 alone.
[Fig. 4] Fig. 4 is a graph illustrating relationships of the P-Q characteristic and
the Ks-Q characteristic with respect to the diameter.
[Fig. 5] Fig. 5 is a graph illustrating relationships of the P-Q characteristic and
the η-Q characteristic with respect to the diameter.
[Fig. 6] Fig. 6 is a diagram illustrating exemplary dimensional parameters related
to a bellmouth 2.
[Fig. 7] Fig. 7 is a graph illustrating the P-Q characteristic based on the dimensional
parameters.
[Fig. 8] Fig. 8 is a graph illustrating the P-Q characteristic observed when L/L0
is varied.
[Fig. 9] Fig. 9 is a graph illustrating a relationship between specific noise level
Ks and the value of L/L0 at an air flow rate Q2.
[Fig. 10] Fig. 10 is a graph illustrating the P-Q characteristic observed when a sloping-portion
angle θ is varied.
[Fig. 11] Fig. 11 is a graph illustrating relationships of fan efficiency η and the
specific noise level Ks with respect to the angle θ at the air flow rate Q2.
[Fig. 12] Fig. 12 is a graph illustrating the P-Q characteristic observed when the
value of H/D is varied.
[Fig. 13] Fig. 13 is a graph illustrating a relationship between static pressure P
and the value of H/D at the air flow rate Q2.
[Fig. 14] Fig. 14 is a graph illustrating relationships of the fan efficiency η and
the specific noise level Ks with respect to the angle θ at the air flow rate Q2.
[Fig. 15] Fig. 15 is a perspective view of a bellmouth 2 having another shape.
[Fig. 16] Fig. 16 includes diagrams illustrating sloping portions 5a having other
exemplary shapes.
[Fig. 17] Fig. 17 includes diagrams illustrating configurations of top-blowing outdoor
units.
[Fig. 18] Fig. 18 is a diagram illustrating a configuration of a side-blowing outdoor
unit.
[Fig. 19] Fig. 19 is an exploded perspective view of a side-blowing bellmouth.
[Fig. 20] Fig. 20 is a diagram illustrating a relationship between the shape of the
bellmouth 2 and the flow of air.
[Fig. 21] Fig. 21 is a diagram illustrating a shape of the bellmouth 2 according to
Embodiment 2 and the flow of air.
[Fig. 22] Fig. 22 is a diagram illustrating a relationship between the bellmouth 2
and a fan guard 10.
[Fig. 23] Fig. 23 is a graph illustrating relationships of input to the fan and noise
with respect to an angle α.
[Fig. 24] Fig. 24 is a diagram illustrating a propeller fan 1 according to Embodiment
4.
[Fig. 25] Fig. 25 is a diagram illustrating path lines representing a blade-tip vortex
produced in a case where ribs 6 are not provided.
[Fig. 26] Fig. 26 is a diagram illustrating path lines representing a blade-tip vortex
produced in a case where the ribs 6 are provided.
[Fig. 27] Fig. 27 is a diagram illustrating an inlet opening 3 of the bellmouth 2.
[Fig. 28] Fig. 28 is a graph illustrating a relationship between the P-Q characteristic
and the R/D value.
[Fig. 29] Fig. 29 is a graph illustrating a relationship between the specific noise
level Ks and the R/D value at the air flow rate Q2.
[Fig. 30] Fig. 30 is a graph illustrating a relationship between the fan efficiency
η and the R/D value at the air flow rate Q2.
[Fig. 31] Fig. 31 is a block diagram of a refrigeration and air-conditioning apparatus
according to Embodiment 5 of the present invention.
Description of Embodiments
Embodiment 1
[0010] Fig. 1 is a diagram illustrating an outline of an air-sending device according to
Embodiment 1 of the present invention. Fig. 1 illustrates a propeller fan 1 and a
bellmouth 2 in sectional view. The air-sending device according to Embodiment 1 is
to be provided in, for example, an outdoor unit of a refrigeration cycle apparatus
such as an air-conditioning apparatus.
[0011] The propeller fan 1 is an axial fan that produces a flow of air (fluid) by causing
a plurality of blades (a propeller, or wings) to rotate about a rotation axis when
a motor or the like (not illustrated) is driven with power supplied thereto. The propeller
fan 1 described herein is not especially limited to but is a fan having a forward-swept
shape. Furthermore, the propeller fan 1 (air-sending device) is disposed as a top-blowing
air-sending device in the outdoor unit such that the rotation axis thereof substantially
corresponds to the direction of gravity (vertical direction, hereinafter also referred
to as height direction of the air-sending device) and air is thus blown in a direction
opposite to the direction of gravity.
[0012] The bellmouth 2 covers the propeller fan 1 in such a manner as to extend in the circumferential
direction (direction of rotation) of the propeller fan 1 (the bellmouth 2 surrounds
the propeller fan 1) and is configured to rectify the flow of air produced by the
rotation of the propeller fan 1. That is, a tubular wall is provided around the propeller
fan 1. As illustrated in Fig. 1, the bellmouth 2 according to Embodiment 1 covers
about 50% of the propeller fan 1 in the direction of the rotation axis (height direction)
of the propeller fan 1.
[0013] An inlet opening 3 is open on the upstream side (inlet side) of the bellmouth 2 so
that air is taken in therefrom. In the bellmouth 2 according to Embodiment 1, the
distance between the rotation axis of the propeller fan 1 and the end of the inlet
opening 3 (the radius of the opening) is larger than the distance between the rotation
axis and the surface of a straight tubular portion 4 (the radius of the straight tubular
portion 4) (the end of the inlet opening 3 spreads outward). Furthermore, an inner
wall (a surface facing the propeller fan 1) extending from the inlet-side end of the
straight tubular portion 4 to the end of the inlet opening 3 forms a curved surface
(with an arc sectional shape). The curved surface has a radius of curvature R. A portion
of the inlet opening 3 having the curved surface is referred to as radius corner 3a.
[0014] The straight tubular portion 4 is a portion of the bellmouth 2 where the inner wall
of the bellmouth 2 extends parallel to the rotation axis of the propeller fan 1. The
position of the outlet-side end of the straight tubular portion 4 and the outlet-side
position of the blades of the propeller fan 1 are not especially limited to but substantially
coincide with each other in the height direction of the air-sending device.
[0015] An outlet opening 5 is open on the downstream side (outlet side) of the bellmouth
2 so that air is blown therefrom. Regarding the outlet opening 5 also, the distance
between the rotation axis of the propeller fan 1 and the end of the outlet opening
5 (the radius of the opening) is larger than the distance between the rotation axis
and the surface of the straight tubular portion 4 (the radius of the straight tubular
portion 4). Furthermore, an inner wall extending from the outlet-side end of the straight
tubular portion 4 (the inlet-side end of the outlet opening 5) to the outlet-side
end of the outlet opening 5 forms a sloping surface that spreads outward with a tapered
(flared) sectional shape. The tapered portion is referred to as a sloping portion
5a. Although the inner wall of the bellmouth 2 according to Embodiment 1 may be formed
merely with the sloping portion 5a and the radius corner 3a.
[0016] Fig. 2 is a graph illustrating a P-Q characteristic and a Ks-Q characteristic of
the propeller fan 1 alone. Fig. 3 is a graph illustrating the P-Q characteristic and
an η-Q characteristic of the propeller fan 1 alone. Here, P denotes static pressure,
Q denotes air flow rate, Ks denotes specific noise level [dB], and η denotes fan efficiency
(static-pressure efficiency) [%]. Given the static pressure P and the air flow rate
Q, the specific noise level Ks and the fan efficiency η satisfy the below Equations
(1) and (2), respectively, where SPL denotes noise [dB] at a position away from the
propeller fan 1 by a predetermined distance, T denotes torque [Nm], and ω denotes
angular velocity [rad/s]. In Equation (1), the unit of static pressure P1 is [mmAq],
and the unit of air flow rate Q1 is [m
3/min]. In Equation (2), the unit of static pressure P2 is [Pa], and the unit of air
flow rate Q2 is [m
3/s].
[0017]

[0018] Referring to Figs. 2 and 3, relationships among the static pressure P, the air flow
rate Q, the specific noise level Ks, and the fan efficiency η will be described. The
P-Q characteristic represents a relationship between the static pressure P, which
is airflow resistance, and the air flow rate Q, supposing that the fan rotation speed
of the propeller fan 1 is constant. Hereinafter, a side having low air flow rate and
high static pressure is referred to as closed side, and a side having high air flow
rate and low static pressure is referred to as open side. In general, air flows more
easily as the airflow resistance becomes smaller (the air flow rate Q becomes higher
as the static pressure P becomes lower), whereas air flows more difficultly as the
airflow resistance becomes larger (the air flow rate Q becomes lower as the static
pressure P becomes higher).
[0019] However, the air flow rate Q and the static pressure P do not always have such a
relationship. There is a zone in which the variation in static pressure P with respect
to the air flow rate Q is small. This zone is referred to as a surging zone. During
rotation of any propeller fan 1, the specific noise level Ks becomes smallest and
the fan efficiency η becomes highest around the surging zone.
[0020] Fig. 4 is a graph illustrating relationships of the P-Q characteristic and the Ks-Q
characteristic with respect to the fan diameter (fan rotation diameter) of the propeller
fan 1. Fig. 5 is a graph illustrating relationships of the P-Q characteristic and
the η-Q characteristic with respect to the diameter of the propeller fan 1. As illustrated
in Figs. 4 and 5, when the fan diameter is increased, the surging zone shifts toward
the open side. Furthermore, when the fan diameter is increased, the gradient of the
P-Q characteristic becomes gentler in a zone on the open side with respect to the
surging zone. In contrast, when the fan diameter is reduced, the gradient of the P-Q
characteristic becomes steeper in the zone on the open side with respect to the surging
zone.
[0021] Now, an operating point will be described. In an outdoor unit of an air-conditioning
apparatus including the propeller fan 1 (air-sending device), let the fan rotation
speed of the propeller fan 1 at a predetermined air flow rate Q0 be N0 while a static
pressure P0 at the air flow rate Q0 is calculated from the P-Q characteristic of the
propeller fan 1 alone obtained at the fan rotation speed N0, then, (P0, Q0) is defined
as the operating point.
[0022] In a case in which the operating point of the air-sending device is on the open side
with respect to the surging zone, the specific noise level Ks at the operating point
is larger than the specific noise level at a point where specific noise level is smallest
and the fan efficiency η at the operating point is lower than the fan efficiency at
a point where fan efficiency is highest. In this case, when the fan diameter is increased,
the surging zone shifts toward the open side, as described above, and closer to the
operating point. Therefore, the specific noise level Ks and the fan efficiency η at
the operating point become closer to the specific noise level at the point where specific
noise level is smallest and to the fan efficiency at the point where fan efficiency
is highest, respectively. Hence, noise and input (power supply) to the fan can be
reduced.
[0023] However, if the fan diameter is increased, the size of the air-sending device increases
and hence the size of an apparatus in which the air-sending device is to be provided
needs to be increased. The increase in size leads to problems such as increase in
cost, deterioration in design, increase in installation space, and so forth.
[0024] To make the specific noise level Ks and the fan efficiency η at the operating point
become closer to the smallest specific noise level and the highest fan efficiency
in a case where the fan diameter cannot be increased and the operating point is on
the open side with respect to the surging zone, the gradient of the P-Q characteristic
may be made gentler in a zone on the open side with respect to the surging zone so
that the static pressure on the open side becomes higher. In such a case, the gradients
of the Ks-Q characteristic and the η-Q characteristic also become gentler, and the
deviations of the specific noise level Ks and the fan efficiency η at the operating
point from the specific noise level at the point where specific noise level is smallest
and the fan efficiency at the point where fan efficiency is highest become smaller
than those in a case where the foregoing gradients are steep. Therefore, noise and
input to the fan can be reduced. In the case where the gradients of the Ks-Q characteristic
and the η-Q characteristic are gentle, even if the operating point is shifted by,
for example, changing the setting of the air flow rate in the air-sending device,
the variations in the specific noise level Ks and in the fan efficiency η can be suppressed
to be small. Therefore, an efficient operation is achieved. In such a case, the smallest
specific noise level and the highest fan efficiency are determined dominantly by the
fan diameter. The larger the fan diameter, the smaller the smallest specific noise
level and the higher the highest fan efficiency. The smaller the fan diameter, the
larger the smallest specific noise level and the lower the highest fan efficiency.
Furthermore, the larger the fan diameter, the gentler the gradient of the P-Q characteristic.
The smaller the fan diameter, the steeper the gradient of the P-Q characteristic.
[0025] For example, in an air-conditioning apparatus including a propeller fan 1, there
are ones in which the setting of the air flow rate is changed among a plurality of
levels. In the case where the fan diameter cannot be increased, during an operation
at the highest air flow rate, the operating points for the Ks-Q characteristic and
for the η-Q characteristic deviate from the point where specific noise level is smallest
and the point where fan efficiency is highest, respectively. Consequently, noise and
input to the fan tend to increase. This is because of the following reason. As described
above, in the case where the fan diameter cannot be increased sufficiently, the surging
zone is on the closed side while the operating point in the operation at the highest
air flow rate is on the open side.
[0026] Fig. 6 is a diagram illustrating exemplary dimensional parameters related to the
bellmouth 2. As illustrated in Fig. 6, the diameter of the propeller fan 1 (fan diameter)
is denoted by D, the length of the bellmouth 2 in the direction of the rotation axis
from the end of the inlet opening 3 to the outlet-side end of the straight tubular
portion 4 (bellmouth height) is denoted by L, the length of the blades in the direction
of the rotation axis of the propeller fan 1 (fan height) is denoted by L0, the lengths
of the sloping portion 5a at the outlet opening 5 in the direction of the rotation
axis of the propeller fan 1 (height, hereinafter referred to as sloping-portion height)
and in the direction of the fan diameter D (hereinafter referred to as sloping-portion
length) are denoted by H and W, respectively, and the angle between a direction in
which the sloping portion 5a is tapered and the direction of the rotation axis of
the propeller fan 1 is denoted as sloping-portion angle θ.
[0027] Fig. 7 is a graph illustrating the P-Q characteristic based on the dimensional parameters
illustrated in Fig. 6, specifically, the P-Q characteristic observed when the parameters
related to the air-sending device illustrated in Fig. 6 are set so as to satisfy D
= 700 mm, L/L0 = 0.1, H/D = 0.01, and θ = 45°, with the fan rotation speed set to
NA. In Fig. 7, the air flow rate Q1 corresponds to the air flow rate around the surging
zone, and the air flow rate Q2 corresponds to the air flow rate at the operating point
that is on the open side with respect to the surging zone.
[0028] Now, there will be described an air-sending device in which the static pressure P
at the operating point that is on the open side with respect to the surging zone is
high and the gradient of the P-Q characteristic on the open side with respect to the
surging zone is gentle. Hereinafter, the term open side refers to an operating point
that is on the open side with respect to the surging zone.
[0029] Fig. 8 is a graph illustrating the P-Q characteristic observed when L/L0 is varied.
In this case, L/L0 is varied by varying the bellmouth height L with the fan height
L0 being constant. As illustrated in Fig. 8, the static pressure P is substantially
constant around the surging zone where the air flow rate is Q1, regardless of the
value of L/L0. At the operating point where the air flow rate is Q2 that is on the
open side with respect to the air flow rate Q1, as L/L0 becomes larger, the static
pressure P becomes higher in a range of L/L0 < 0.5 but is substantially constant in
a range of L/L0 ≥ 0.5.
[0030] Fig. 9 is a graph illustrating a relationship between the specific noise level Ks
[dB] and the value of L/L0 in the air-sending device with the fan rotation speed being
NA and the air flow rate being Q2. As illustrated in Fig. 9, in the range of L/L0
< 0.5, the specific noise level Ks on the open side can be reduced more as the value
of L/L0 becomes larger. Meanwhile, in the range of L/L0 ≥ 0.5, the specific noise
level Ks on the open side does not substantially change.
[0031] The reason for this is as follows. In a case where the bellmouth height L is small,
a blade-tip vortex tends to occur from portions of the blades of the propeller fan
1 that are not covered by the bellmouth 2, generating noise. In contrast, in a case
where the bellmouth height L is large, the flow path for the blade-tip vortex is narrowed.
Therefore, noise due to the blade-tip vortex is reduced, whereas variations in the
static pressure on the wall of the bellmouth 2 facing the fan increase. Hence, in
the range of L/L0 < 0.5, noise due to the blade-tip vortex is reduced more as the
bellmouth height L becomes larger. In the range of L/L0 ≥ 0.5, the influences of the
two are of substantially the same level and do not substantially vary. Accordingly,
the specific noise level Ks does not vary. Considering the above, the propeller fan
1 and the bellmouth 2 desirably satisfy a relationship of L/L0 ≥ 0.5 in the height
direction.
[0032] Now, there will be described a case where the sloping-portion angle θ is varied while
the parameters illustrated in Fig. 6 are set so as to satisfy L/L0 = 0.5 and W/D =
0.15. In this case, H = W/tanθ. To distinguish this case from a case where W = 0 and
the fan diameter D is large, the sloping-portion length W is set so as to be constant.
[0033] Fig. 10 is a graph illustrating the P-Q characteristic observed when the sloping-portion
angle θ is varied with the fan rotation speed being NA. The static pressure P is substantially
constant around the surging zone, regardless of the sloping-portion angle θ. In contrast,
in a range of θ ≥ 60°, the static pressure P on the open side with respect to the
surging zone becomes smaller as the sloping-portion angle θ becomes larger. In a range
of 0 < θ ≤ 60°, the static pressure P on the open side is substantially constant.
[0034] Fig. 11 is a graph illustrating relationships of the fan efficiency η and the specific
noise level Ks with respect to the angle θ with the fan rotation speed being NA and
the air flow rate being Q2. In Fig. 11, the fan efficiency η and the specific noise
level Ks around the surging zone are substantially constant regardless of θ. In the
range of θ ≥ 60°, the fan efficiency η becomes lower and the specific noise level
Ks becomes higher as θ becomes larger. In the range of 0 < θ ≤ 60°, the fan efficiency
η and the specific noise level Ks on the open side are considered to be substantially
constant with small rates of increase (note that 0 < θ ≤ 45° is considered to be more
preferable because the fan efficiency η and the specific noise level Ks slightly increase
in a range between 45° and 60°).
[0035] The reason why the fan efficiency η and the specific noise level Ks on the open side
are improved in the range of 0 < θ ≤ 60° compared with those observed in the range
of θ ≥ 60° is as follows. Since the area of an outlet air passage provided at the
outlet opening 5 is increased, the velocity at which air is blown is reduced and the
static pressure P is increased. Furthermore, since the outlet opening 5 spreads outward,
the outlet air passage functions as a diffuser. In such a situation, in the range
of 0 < θ ≤ 60°, air flowing near the sloping portion 5a is blown along the sloping
portion 5a. Thus, the function as a diffuser is exerted.
[0036] Fig. 12 is a graph illustrating the P-Q characteristic observed when the value of
H/D is varied with the fan rotation speed being NA. Fig. 13 is a graph illustrating
a relationship between the static pressure P and the value of H/D with the fan rotation
speed being NA and the air flow rate being Q2. In this case, the parameters related
to the air-sending device illustrated in Fig. 6 are set so as to satisfy L/L0 = 0.5
and θ = 60°.
[0037] Referring to Fig. 12, the static pressure P is substantially constant around the
surging zone, regardless of the value of H/D. In contrast, in a range of H/D < 0.04,
the static pressure P on the open side with respect to the surging zone becomes larger
as the value of H/D becomes larger. In a range of H/D ≥ 0.04, the static pressure
P on the open side is substantially constant.
[0038] As illustrated in Fig. 13, as the value of H/D becomes larger, the static pressure
P on the open side becomes larger but the increase in the static pressure P with respect
to the value of H/D is smaller than that in the range of H/D < 0.04.
[0039] Fig. 14 is a graph illustrating relationships of the fan efficiency η and the specific
noise level Ks with respect to H/D with the fan rotation speed being NA and the air
flow rate being Q2. In Fig. 14, the fan efficiency η and the specific noise level
Ks around the surging zone are substantially constant regardless of the value of H/D.
In contrast, in the range of H/D < 0.04, the fan efficiency η becomes lower and the
specific noise level Ks becomes larger as the value of H/D becomes smaller. In the
range of H/D ≥ 0.04, the improvements in the fan efficiency η and in the specific
noise level Ks on the open side become smaller relative to the increase in the value
of H/D.
[0040] The reason why the fan efficiency and the specific noise level on the open side are
more improved in the range of H/D ≥ 0.04 than in the range of H/D < 0.04 is as follows.
Since the area of the outlet air passage is increased, the velocity at which air is
blown is reduced and the static pressure P is increased. Furthermore, since the outlet
opening 5 spreads outward, the outlet air passage functions as a diffuser. In such
a situation, in the range of H/D ≥ 0.04, the function as a diffuser is exerted efficiently.
[0041] As described above, when the fan diameter D is small, the surging zone is shifted
toward the closed side. Therefore, a certain size of the fan diameter D needs to be
provided (for example, in an outdoor unit, the fan diameter D is desired to be 600
mm or larger). Hence, when it is attempted to increase the value of H/D, the sloping-portion
height H is to be increased. This accompanies an increase in the size of a downstream
portion of the bellmouth 2.
[0042] As illustrated in Fig. 14, for example, in the range of H/D ≥ 0.04, the improvements
in the fan efficiency η and in the specific noise level Ks on the open side are relatively
small even if the value of H/D is increased. Therefore, in the range of H/D ≥ 0.04,
H/D is set to a large value if, for example, there is any allowance for the range
of possible size of the bellmouth 2 in relation to the casing of a heat source unit.
If there is no such allowance, at least H/D = 0.04 is to be satisfied. Thus, the fan
efficiency η and the specific noise level Ks on the open side can be improved.
[0043] In the air-sending device according to Embodiment 1 that is to be provided in an
outdoor unit, the propeller fan 1 and the bellmouth 2 are configured such that conditions
(parameters) are set so as to satisfy the relationships of H/D ≥ 0.04, 0 < θ ≤ 60°,
and L/L0 ≥ 0.5 as described above. In addition, as demonstrated by the above results,
if the air-sending device is configured on the basis of the conditions satisfying
the above relationships, the conditions each provide an effect of suppressing the
increase in noise and power consumption (input to the fan). For example, one of the
conditions for suppressing the increase in noise and power consumption that provides
the most significant effect is the condition satisfying H/D ≥ 0.04, followed by the
condition satisfying 0 < θ ≤ 60° and the condition satisfying L/L0 ≥ 0.5, sequentially.
Therefore, even if not all of the conditions are satisfied, one of or a combination
of any of the conditions only needs to be satisfied, whereby the effects according
to the present invention are provided.
[0044] Fig. 15 is a perspective view of a bellmouth 2 having another shape. For example,
if the diameter of the bellmouth 2 (particularly, the outlet opening 5) is larger
than at least one of the width and the depth of the casing of an outdoor unit, the
bellmouth 2 extends beyond the casing and comes into contact with another bellmouth
provided in another outdoor unit. This may make it difficult to arrange a plurality
of outdoor units close to one another. Hence, the shape of the bellmouth 2 may be
partially altered such that the diameter thereof becomes smaller than the width and
the depth of the casing of the outdoor unit. For example, in the bellmouth 2 illustrated
in Fig. 16, the sloping-portion angle θ is not constant over the entire circumference
of the bellmouth 2 and is changed in some portions. Thus, the bellmouth 2 is prevented
from extending beyond the casing while the above-described conditions are satisfied.
[0045] Fig. 16 includes diagrams illustrating sloping portions 5a having other exemplary
shapes, respectively. For example, in Figs. 1 and others, the sloping portion 5a extends
linearly in sectional view. In some cases, however, the sloping portion 5a may not
be able to extend linearly because of restrictions on the manufacturing process, design,
dimensions, and so forth. Even in such a case, an effect similar to that provided
by the sloping portion 5a that extends linearly can be provided, as long as the angle
of a straight line connecting the two ends of the sloping portion 5a falls within
a range of about 0 < θ ≤ 60°. For example, the sloping portion 5a may have a concave,
substantially arc shape as illustrated in Fig. 16(a), a convex, substantially arc
shape as illustrated in Fig. 16(b), or the like.
[0046] Fig. 17 includes diagrams illustrating configurations of top-blowing outdoor units,
respectively. Fig. 17(a) illustrates an outdoor unit in which an outdoor-side heat
exchanger that exchanges heat between a refrigerant and air has a rectangular U shape
in a casing. Fig. 17(b) illustrates an outdoor unit in which an outdoor-side heat
exchanger has a V shape, or a W shape. As illustrated in Fig. 17, in a top-blowing
outdoor unit, the heat exchanger has a rectangular U, V, or W shape with a plurality
of bends, and the air-sending device blows air in the direction opposite to the direction
of gravity (in a top-blowing direction).
[0047] Fig. 18 is a diagram illustrating a configuration of a side-blowing outdoor unit.
As illustrated in Fig. 18, an air-sending device provided in the side-blowing outdoor
unit blows air in a direction perpendicular to the direction of gravity. The side-blowing
outdoor unit includes an outdoor-side heat exchanger having an L shape.
[0048] Comparing the rectangular-U-shaped heat exchanger for the top-blowing type illustrated
in Fig. 17(a) and an L-shaped heat exchanger for the side-blowing type, the rectangular-U-shaped
heat exchanger takes in air from three sides, whereas the L-shaped heat exchanger
takes in air from two sides. Therefore, the rectangular-U-shaped heat exchanger can
have a certain level of capacity more easily than the L-shaped heat exchanger.
[0049] In the top-blowing type with a plurality of bends illustrated in Fig. 17(b), a portion
of the heat exchanger allocated to one propeller fan (air-sending device) has a V
shape. In this case, air is taken in from two sides, as with the L-shaped heat exchanger.
Furthermore, the two heat exchangers have the same length. In contrast, in the L-shaped
heat exchanger for the side-blowing outdoor unit, one side of the heat exchanger as
the inlet side is short. Therefore, the V-shaped heat exchanger provided in the top-blowing
outdoor unit can have a certain level of capacity more easily than the L-shaped heat
exchanger. Hence, the area of the front surface of the heat exchanger increases, and
the front velocity through the heat exchanger is reduced. Accordingly, the airflow
resistance of the heat exchanger is reduced. Thus, the airflow resistance of the outdoor
unit as a whole can be reduced.
[0050] Hereinafter, a loss factor ξ is used as an index that indicates on which of the closed
side and the open side the operating point is. Letting the static pressure and the
air flow rate at the operating point be P and Q, respectively, the loss factor ξ is
expressed as ξ = P/Q
2. As ξ becomes smaller, the operating point is shifted more toward the open side.
As ξ becomes larger, the operating point is shifted more toward the closed side.
[0051] The heat exchanger of the top-blowing outdoor unit, which in general has smaller
airflow resistance than that of the side-blowing outdoor unit as described above,
has a smaller loss factor ξ with the operating point being on the open side. Therefore,
to bring the surging zone closer to the operating point, the top-blowing type needs
to have a larger fan diameter D than the side-blowing type. If the fan diameter D
cannot be increased because of any design restrictions, such as installation area,
on the size of the outdoor unit, the operating point is defined on the open side with
respect to the surging zone. Consequently, the specific noise level Ks is increased
and the fan efficiency η is reduced.
[0052] In view of the above, the configuration according to the present invention defined
so as to bring the operating point closer to the surging zone without increasing the
fan diameter D is more necessary for the top-blowing outdoor unit than for the side-blowing
outdoor unit and can exert its effects more in the top-blowing outdoor unit.
[0053] Now, differences between a bellmouth for the top-blowing type and a bellmouth for
the side-blowing type will be described. As an exemplary bellmouth for the top-blowing
type, the bellmouth 2 shaped as illustrated in Fig. 15 is made of resin and can be
formed by solid casting, regardless of L/L0 illustrated in Fig. 1.
[0054] Fig. 19 is an exploded perspective view of the side-blowing bellmouth. In general,
a bellmouth sheet metal 10 illustrated in Fig. 19 is formed into a bellmouth for a
side-blowing outdoor unit by solid casting. In such a case, L/L0 of the bellmouth
2 cannot be made large (L/L0 = 1, for example). To do so, other parts need to be prepared.
[0055] Hence, to apply the bellmouth shape according to the present invention to a side-blowing
outdoor unit is relatively more difficult than to apply it to a top-blowing outdoor
unit and is not practical.
[0056] As described above, according to Embodiment 1, the air-sending device of the outdoor
unit is configured under the conditions of L/L0 ≥ 0.5, 0 < θ ≤ 60°, and H/D ≥ 0.04.
Therefore, the relationship between the static pressure P and the air flow rate Q
on the open side can be made closer to the relationship between the static pressure
P and the air flow rate Q in the surging zone without increasing the fan diameter
D, and hence the fan efficiency η and the specific noise level Ks can be improved.
Thus, input to the fan and noise can be reduced.
Embodiment 2
[0057] Fig. 20 is a diagram illustrating a relationship between the shape of the bellmouth
2 and the flow of air. In Fig. 20, individual airflows are represented by streamlines.
On the downstream side of the bellmouth, air blown from the outlet opening 5 flows
more obliquely along the sloping portion 5a as the distance to the wall of the sloping
portion 5a becomes smaller. For example, in a case where an air-conditioning apparatus
includes a plurality of outdoor units that are provided on the rooftop of a building,
short cycles may occur in which air that have been blown obliquely is taken into adjacent
outdoor units because of the suction force of propeller fans 1 of the adjacent outdoor
units and ambient wind. For example, in an outdoor unit that has taken in high-temperature
air blown from another outdoor unit including an outdoor-side heat exchanger functioning
as a condenser in a casing, the temperature difference between the refrigerant and
air is reduced. This may reduce the efficiency of heat exchange and hence COP.
[0058] Fig. 21 is a diagram illustrating a shape of the bellmouth 2 according to Embodiment
2 and the flow of air. The bellmouth 2 according to Embodiment 2 illustrated in Fig.
21 includes a straight tubular portion 5b provided at the downstream exit (end) of
the outlet opening 5. Suppose that the sloping portion 5a satisfies the conditions
(parameters) that are set as described in Embodiment 1.
[0059] Under such circumstances, air around the outer circumference of a downstream portion
of the bellmouth 2 flows along the sloping portion 5a and the straight tubular portion
5b and is blown upward (the direction opposite to the direction of gravity). Therefore,
the occurrence of short cycles into adjacent outdoor units can be suppressed.
[0060] Furthermore, for example, to protect the propeller fan 1 and other members from foreign
matter that may be taken into the outlet opening 5, a fan guard in the form of a grating
that covers the outlet opening 5 may be provided. In such a case, the fan guard can
be easily fixed by providing a straight tubular portion 5b at the downstream end of
the bellmouth.
[0061] As described above, in the outdoor unit including the air-sending device according
to Embodiment 2, the straight tubular portion 5b is provided at the downstream exit
(end) of the outlet opening 5 and allows air to be blown upward so that adjacent outdoor
units are not affected. Thus, the occurrence of short cycles can be suppressed. Furthermore,
the fan guard in the form of a grating can be easily fixed.
Embodiment 3
[0062] Fig. 22 is a diagram illustrating a relationship between the bellmouth 2 of an air-sending
device and a fan guard 10 provided to the air-sending device. In Fig. 22, the fan
guard 10 is a grating-like net and covers the outlet opening 5, thereby protecting
the propeller fan 1 and other devices provided in the casing of the outdoor unit.
The grating has a certain length in the height direction. Therefore, some air collides
on side surfaces depending on the angle of airflow. In this case, the angle between
the grating of the fan guard 10 and the rotation axis of the fan is denoted by α.
[0063] Fig. 23 is a graph illustrating relationships of the input to the fan and the noise
with respect to the angle α in a case where, for example, air is blown from the outdoor
unit at a predetermined rate. As illustrated in Fig. 23, when α = 0°, the input to
the fan and the noise are both smallest. This is because the airflow resistance at
the grating of the fan guard 10 becomes smallest when α = 0°. Considering such circumstances,
the grating of the fan guard 10 is preferably configured such that the angle thereof
with respect to the rotation axis of the fan becomes as close to 0° as possible.
[0064] As described above, in the outdoor unit including the air-sending device according
to Embodiment 3, air resistance can be minimized by setting the angle between the
grating of the fan guard 10 and the rotation axis of the fan to 0°. Therefore, input
to the fan required and noise generated when air is blown from the outdoor unit at
a predetermined air flow rate can be minimized, and the outdoor unit can have high
operation and energy efficiency.
Embodiment 4
[0065] Fig. 24 is a diagram illustrating a propeller fan 1 according to Embodiment 4. In
Embodiment 4, a shape of the propeller fan 1 will be described. The propeller fan
1 according to Embodiment 4 has ribs 6 extending from the outer peripheral edge of
a suction surface of the propeller fan 1 toward the upstream side in the axial direction.
[0066] Table 1 summarizes values of the input to the fan and the noise at a predetermined
air flow rate for an air-sending device including the propeller fan 1 having the ribs
6 and an air-sending device including the propeller fan 1 not having the ribs 6.
[0067]
[Table 1]
|
Input to fan [W] |
Noise [dB] |
Without ribs 6 |
632 |
62.1 |
With ribs 6 |
630 |
60.8 |
[0068] Table 1 shows that the values of the input to the fan are substantially the same,
whereas the noise for the case where the ribs 6 are provided is smaller. The reason
for this is as follows. First, the rms of variations in the static pressure on the
wall of the straight tubular portion 4 of the bellmouth 2 is defined on the basis
of a static pressure Ps(t) in accordance with Equations (3) and (4) given below. The
larger the rms of variations in the static pressure, the larger the noise generated
from the wall.
[0069] 
[0070] With the increase in the vorticity of the blade-tip vortex, which is a leakage flow
occurring because of a difference in static pressure near the outer peripheral edge
of the propeller fan 1 and from the pressure surface to the suction surface, the rms
of variations in the static pressure increases, generating noise. The ribs 6 act as
airflow resistances for the leakage flow in the form of a blade-tip vortex occurring
from the pressure surface to the suction surface and hence narrow the flow path for
the leakage flow. Therefore, the occurrence of a blade-tip vortex can be suppressed.
[0071] Fig. 25 is a diagram illustrating path lines representing a blade-tip vortex produced
by the rotation of the propeller fan 1 not having the ribs 6. Fig. 26 is a diagram
illustrating path lines representing a blade-tip vortex produced in the case where
the ribs 6 are provided. Table 2 summarizes values of the rms of variations in the
static pressure in the cases where the ribs 6 are provided and not provided.
[0072]
[Table 2]
|
rms [Pa] |
Without ribs 6 |
118.0 |
With ribs 6 |
94.4 |
[0073] As illustrated in Fig. 26, in the case where the ribs 6 are provided, the vorticity
of the blade-tip vortex is smaller than that in the case where the ribs 6 are not
provided. Therefore, in the air-sending device of the outdoor unit according to Embodiment
4, the rms of variations in the static pressure on the wall of the bellmouth 2 is
reduced as shown in Table 2. Accordingly, noise can be reduced.
Embodiment 5
[0074] Fig. 27 is a diagram illustrating the radius of curvature R at the radius corner
3a of the inlet opening 3 of the bellmouth 2 according to Embodiment 5. In Fig. 27,
two shapes of the inlet opening 3 having different radii of curvature R are illustrated.
[0075] Fig. 28 is a graph illustrating a relationship between the P-Q characteristic and
R/D. The graph is based on values of R/D (hereinafter referred to as R/D) obtained
when the radius of curvature R at the radius corner 3a is varied while the fan diameter
D and the rotation speed N0 are set so as to be constant and the position of the end
of the inlet opening 3 of the bellmouth 2 is fixed. In Fig. 28, the P-Q characteristic
is represented as R/D at each of the air flow rates Q1 and Q2.
[0076] As illustrated in Fig. 28, the static pressure P does not significantly vary at the
air flow rate Q1 regardless of R/D. Although not especially illustrated, the specific
noise level Ks and the fan efficiency η at Q1 do not significantly vary, either, despite
the variations in R/D.
[0077] Fig. 29 is a graph illustrating a relationship between the specific noise level Ks
and R/D at the air flow rate Q2. Fig. 30 is a graph illustrating a relationship between
the fan efficiency η and R/D at the air flow rate Q2. As illustrated in Figs. 28 to
30, at the air flow rate Q2, as R/D is increased, the static pressure P and the fan
efficiency η become higher and the specific noise level Ks becomes smaller. Furthermore,
the gradients of the P-Q characteristic, the Ks-Q characteristic, and the η-Q characteristic
on the open side become gentler. That is, in the bellmouth 2, the more the radius
of curvature R at the radius corner 3a is increased, the more the static pressure
P and the fan efficiency η at the operating point that is on the open side are improved
and the more the specific noise level Ks at the operating point that is on the open
side is reduced. Thus, rotation speed, input to the fan, and noise can be reduced.
[0078] As described above, the larger the radius of curvature R at the radius corner 3a
of the inlet opening 3, the higher the fan efficiency η and the smaller the specific
noise level Ks. However, for example, if the radius of curvature R at the radius corner
3a are to be made uniform over the entire circumference in a case where the casing
has a width and a depth (longitudinal side and lateral side) that are of different
lengths (sizes) because of restrictions on the dimensions of the outdoor unit and
so forth, the radius of curvature R generally becomes small.
[0079] Hence, if the ratios of the longitudinal length and the lateral length of the casing
of the outdoor unit are different, any part of the radius corner 3a that can be widened
may be widened such that there are variations in the position of the end of the inlet
opening 3 so that the integrated value of radii of curvature R at the radius corner
3a obtained over the entire circumference of the inlet opening 3 becomes largest.
Embodiment 6
[0080] Fig. 31 is a block diagram of a refrigeration and air-conditioning apparatus according
to Embodiment 6 of the present invention. Embodiment 6 concerns a refrigeration and
air-conditioning apparatus as an exemplary refrigeration cycle apparatus including
the above-described air-sending device. The refrigeration and air-conditioning apparatus
illustrated in Fig. 31 includes an outdoor unit (outdoor device) 100, which is the
one described above, and a load unit (indoor device) 200 that are connected by refrigerant
pipes, thereby forming a refrigerant circuit as a main part (hereinafter referred
to as main refrigerant circuit) through which a refrigerant is made to circulate.
One of the refrigerant pipes through which a refrigerant in a gas state (gas refrigerant)
flows is referred to as gas pipe 300. Another of the refrigerant pipes through which
a refrigerant in a liquid state (liquid refrigerant or, occasionally, two-phase gas-liquid
refrigerant) flows is referred to as liquid pipe 400.
[0081] The outdoor unit 100 according to Embodiment 6 includes the following devices (means):
a compressor 101, an oil extractor 102, a four-way valve 103, an outdoor-side heat
exchanger 104, an outdoor-side air-sending device 105, an accumulator (gas-liquid
separator) 106, an outdoor-side throttle device (expansion valve) 107, a heat exchanger
108 related to a refrigerant, a bypass throttle device 109, and an outdoor-side controller
110.
[0082] The compressor 101 compresses a refrigerant sucked thereinto and discharges the refrigerant.
The compressor 101 includes an inverter device or the like and is capable of finely
changing the capacity of the compressor 101 (the amount of the refrigerant to be discharged
per unit time) by arbitrarily changing the operating frequency.
[0083] The oil extractor 102 extracts lubricant contained in the refrigerant that has been
discharged from the compressor 101. The lubricant thus extracted is returned to the
compressor 101. The four-way valve 103 switches the flow of the refrigerant between
that for a cooling operation and that for a heating operation on the basis of instructions
issued by the outdoor-side controller 110. The outdoor-side heat exchanger 104 exchanges
heat between a refrigerant and air (outdoor air). For example, in the heating operation,
the outdoor-side heat exchanger 104 functions as an evaporator and exchanges heat
between the refrigerant having flowed thereinto via the outdoor-side throttle device
107 and thus having a low pressure and air, thereby evaporating and gasifying the
refrigerant. In the cooling operation, the outdoor-side heat exchanger 104 functions
as a condenser and exchanges heat between the refrigerant having been compressed by
the compressor 101 and having flowed thereinto from the side of the four-way valve
103 and air, thereby condensing and liquefying the refrigerant. The outdoor-side heat
exchanger 104 includes the outdoor-side air-sending device 105, which is the air-sending
device according to any of Embodiments 1 to 4 described above, so that heat is efficiently
exchanged between the refrigerant and air. The outdoor-side air-sending device 105
may also include an inverter device so as to finely change the rotation speed of the
propeller fan 1 by arbitrarily changing the operating frequency of the fan motor.
[0084] The heat exchanger 108 related to a refrigerant exchanges heat between the refrigerant
flowing through a main flow path in the refrigerant circuit and the refrigerant having
branched off from the flow path into the bypass throttle device 109 (expansion valve)
and whose flow rate has been thus controlled. Particularly, in a case where the refrigerant
needs to be supercooled in the cooling operation, the heat exchanger 108 related to
the refrigerant supercools the refrigerant and supplies the refrigerant to the load
unit 200. The liquid flowing therethrough via the bypass throttle device 109 is returned
to the accumulator 106 via a bypass pipe. The accumulator 106 is means that stores,
for example, an excessive refrigerant that is in a liquid state. The outdoor-side
controller 110 includes, for example, a microcomputer or the like. The outdoor-side
controller 110 is capable of wired or radio communication with a load-side controller
204 and controls operations concerning the entirety of the refrigeration and air-conditioning
apparatus by controlling various means included in the refrigeration and air-conditioning
apparatus by, for example, controlling the operating frequency of the compressor 101
while controlling the inverter circuit on the basis of data concerning detection performed
by various detecting means (sensors) provided in the refrigeration and air-conditioning
apparatus.
[0085] The load unit 200 includes a load-side heat exchanger 201, a load-side throttle device
(expansion valve) 202, a load-side air-sending device 203, and the load-side controller
204. The load-side heat exchanger 201 exchanges heat between a refrigerant and air.
For example, in the heating operation, the load-side heat exchanger 201 functions
as a condenser and exchanges heat between the refrigerant having flowed thereinto
from the gas pipe 300 and air, thereby condensing and liquefying the refrigerant (or
turning the refrigerant into two-phase gas-liquid) before discharging the refrigerant
toward the side of the liquid pipe 400. In the cooling operation, the load-side heat
exchanger 201 functions as an evaporator and exchanges heat between the refrigerant
whose pressure has been reduced by the load-side throttle device 202 and air, thereby
evaporating and gasifying the refrigerant, while letting the refrigerant take away
the heat from the air, before discharging the refrigerant toward the side of the gas
pipe 300. The load unit 200 includes the load-side air-sending device 203 for adjusting
the flow of air used for heat exchange. The speed of operation of the load-side air-sending
device 203 is determined on the basis of, for example, settings made by the user.
The load-side throttle device 202 is provided for adjusting the pressure of the refrigerant
in the load-side heat exchanger 201 by changing its opening degree.
[0086] The load-side controller 204 also includes a microcomputer or the like and is capable
of wired or radio communication with, for example, the outdoor-side controller 110.
The load-side controller 204 controls various devices (means) included in the load
unit 200 so that, for example, indoor air comes to have a predetermined temperature
on the basis of instructions issued by the outdoor-side controller 110, the residents,
or the like. Furthermore, the load-side controller 204 transmits signals containing
data concerning detection performed by detecting means provided in the load unit 200.
[0087] As described above, in the refrigeration and air-conditioning apparatus according
to Embodiment 5, the outdoor-side air-sending device 105, which is the air-sending
device described in any of Embodiments 1 to 4, is applied to the outdoor unit 100
so that air is blown in the direction opposite to the direction of gravity, whereby
noise reduction is realized while air flow rate is increased. Thus, the energy efficiency
of the refrigeration and air-conditioning apparatus (refrigeration cycle apparatus)
can be improved.
Reference Signs List
[0088] 1 propeller fan, 2 bellmouth, 3 inlet opening, 3a radius corner, 4 straight tubular
portion, 5 outlet opening, 5a sloping portion, 5b straight tubular portion, 6 rib,
10 bellmouth sheet metal, 100 outdoor unit, 101 compressor, 102 oil extractor, 103
four-way valve, 104 outdoor-side heat exchanger, 105 outdoor-side air-sending device,
106 accumulator, 107 outdoor-side throttle device, 108 heat exchanger related to the
refrigerant, 109 bypass throttle device, 110 outdoor-side controller, 200 load unit,
201 load-side heat exchanger, 202 load-side throttle device, 203 load-side air-sending
device, 204 load-side controller, 300 gas pipe, 400 liquid pipe.