U.S. patent application number 16/761530 was filed with the patent office on 2020-11-26 for impeller having primary blades and secondary blades.
This patent application is currently assigned to AERONET INC.. The applicant listed for this patent is AERONET INC.. Invention is credited to Seungbae LEE.
Application Number | 20200370562 16/761530 |
Document ID | / |
Family ID | 1000005051095 |
Filed Date | 2020-11-26 |
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United States Patent
Application |
20200370562 |
Kind Code |
A1 |
LEE; Seungbae |
November 26, 2020 |
IMPELLER HAVING PRIMARY BLADES AND SECONDARY BLADES
Abstract
Provided is an impeller including a first portion including a
first hub and a plurality of primary blades each extending while
being spaced an equal distance from each other along an outer
circumference of the first hub and a second portion including a
second hub coupled to a lower side of the first hub by using a
projection-groove coupling manner and a plurality of secondary
blades each extending while being spaced apart from each other
along an outer circumference of the second hub. Here, when a
projection angle between a leading edge (L.E.) and a trailing edge
(T.E.) of each of the primary blades is .PHI..sub.1, and a
projection angle between a leading edge (L.E.) and a trailing edge
(T.E.) of each of the secondary blades is .theta.1, the projection
angle .PHI..sub.1 and .theta..sub.1 includes an upstream angle
.PHI..sub.1u and .theta..sub.1u and a downstream angle .PHI..sub.1d
and .theta..sub.1d, at which the primary blade and the secondary
blade overlap each other, and an angle .PHI..sub.1m and
.theta..sub.1m at which the primary blade and the secondary blade
do not overlap each other, and the projection angle .theta..sub.1
is less than the projection angle .PHI..sub.1 to satisfy an
equation 0<.theta..sub.1<.PHI..sub.1 as a radius of each of
the primary blade and the secondary blade goes from the hub to the
edge.
Inventors: |
LEE; Seungbae; (Incheon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AERONET INC. |
Incheon |
|
KR |
|
|
Assignee: |
AERONET INC.
Incheon
KR
|
Family ID: |
1000005051095 |
Appl. No.: |
16/761530 |
Filed: |
December 15, 2017 |
PCT Filed: |
December 15, 2017 |
PCT NO: |
PCT/KR2017/014809 |
371 Date: |
May 5, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/30 20130101 |
International
Class: |
F04D 29/30 20060101
F04D029/30 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2017 |
KR |
10-2017-0147057 |
Dec 14, 2017 |
KR |
10-2017-0171944 |
Claims
1. An impeller comprising: a first portion comprising a first hub
and a plurality of primary blades each extending while being spaced
an equal distance from each other along an outer circumference of
the first hub; and a second portion comprising a second hub coupled
to a lower side of the first hub by using a projection-groove
coupling manner and a plurality of secondary blades each extending
while being spaced apart from each other along an outer
circumference of the second hub, wherein when a projection angle
between a leading edge (L.E.) and a trailing edge (T.E.) of each of
the primary blades is .PHI..sub.1, and a projection angle between a
leading edge (L.E.) and a trailing edge (T.E.) of each of the
secondary blades is .theta..sub.1, the projection angle .PHI..sub.1
and .PHI..sub.1 comprises an upstream angle 1.sub.1u and
.theta..sub.1u and a downstream angle .PHI..sub.1d and
.theta..sub.1d, at which the primary blade and the secondary blade
overlap each other, and an angle .PHI..sub.1m and .theta..sub.1m at
which the primary blade and the secondary blade do not overlap each
other, and the projection angle .theta..sub.1 is less than the
projection angle .PHI..sub.1 to satisfy an equation
0<.theta.1<.PHI..sub.1 as a radius of each of the primary
blade and the secondary blade goes from the hub to the edge.
2. The impeller of claim 1, wherein the angles .theta..sub.1u and
.theta..sub.1d of the secondary blade have magnitudes overlapping
the primary blade so that a channel around a downstream of a
negative-pressure surface of the primary blade is guided.
3. The impeller of claim 1, wherein the first hub comprises a
plurality of first coupling projections, which are spaced apart
from each other on a bottom surface thereof, and a plurality of
first coupling grooves that are provided by the plurality of first
coupling projections, the second hub comprises a plurality of
second coupling projections, which are spaced apart from each other
on a top surface thereof, and a plurality of second coupling
grooves that are provided by the plurality of second coupling
projections, the plurality of first coupling projections are
coupled to the plurality of second coupling grooves, and the
plurality of second coupling projections are coupled to the
plurality of first coupling grooves.
4. The impeller of claim 3, wherein the plurality of first coupling
projections are coupled to the plurality of second coupling grooves
in a pressing manner, and the plurality of second coupling
projections are coupled to the plurality of first coupling grooves
in a pressing manner.
5. The impeller of claim 3, wherein the plurality of first coupling
projections are coupled to the plurality of second coupling grooves
by using an adhesive, and the plurality of second coupling
projections are coupled to the plurality of first coupling grooves
by using an adhesive.
6. The impeller of claim 1, wherein each of the first hub and the
second hub has a band shape.
7. The impeller of claim 1, wherein the first and second hubs form
a single cone shape when coupled to each other.
8. An impeller comprising: a first portion comprising a circular
bottom plate, a hub protruding from a central portion of a top
surface of the circular bottom plate, and a plurality of primary
blades formed in a circumferential direction with respect to the
hub while being spaced an equal distance from each other on the top
surface of the circular bottom plate; and a second portion
comprising a shroud having a band shape and a plurality of
secondary blades spaced a distance from each other along a bottom
surface of the shroud in an integrated manner, wherein when an
inlet area between a negative-pressure surface of the primary blade
and a pressure surface of the secondary blade is Ssu, an inlet area
between the pressure surface of the primary blade and a
negative-pressure surface of the secondary blade is Spu, a
downstream area of a channel of the negative-pressure surface of
the primary blade, which is an area at a downstream of each
channel, is Ssd, and a downstream area of a channel of the pressure
surface of the primary blade is Spd, an outlet angle of the
secondary blade is equal to that of the primary blade, an inlet of
the secondary blade is disposed at a position at which an S-shape
is varied, and an inlet angle of the secondary blade allows a
tangent line of a flow angle to coincide with a primary streamline
of the channel.
9. The impeller of claim 8, wherein a leading edge (L.E.) of the
secondary blade is disposed between channels having the same radial
inlet so hat the areas Ssu and Spu are equal to each other.
10. The impeller of claim 8, wherein an outlet angle and an outlet
position between channels are set by rotating a trailing edge
(T.E.) of the secondary blade to be disposed between channels
having the same radial outlet by using a leading edge (L.E.) of the
secondary blade as a pivot point, thereby maintaining the areas Ssu
and Ssd are similar to each other.
11. The impeller of claim 8, wherein the shroud has a band
shape.
12. The impeller of claim 8, wherein a plurality of first coupling
groove, to which lower edges of the plurality of secondary blades
are inserted, are defined in the top surface of the bottom plate,
and a plurality of second coupling groove, to which upper edges of
the plurality of primary blades are inserted, are defined in the
bottom surface of the shroud.
13. The impeller of claim 12, wherein the lower edges of the
plurality of secondary blades are coupled to the plurality of first
coupling grooves in a pressing manner, and the lower edges of the
plurality of primary blades are coupled to the plurality of second
coupling grooves in a pressing manner.
14. The impeller of claim 12, wherein the lower edges of the
plurality of secondary blades are coupled to the plurality of first
coupling grooves by using an adhesive, and the lower edges of the
plurality of primary blades are coupled to the plurality of second
coupling grooves by using an adhesive.
15. The impeller of claim 1, wherein the plurality of secondary
blades each disposed between each of the primary blades are spaced
different distances from each other along a rotation direction of
the impeller.
16. The impeller of claim 8, wherein the circular bottom plate and
the shroud are inclined in a flow downstream direction or formed in
a horizontal direction.
17. The impeller of claim 16, wherein the circular bottom plate has
an outer diameter less than an inner diameter of the shroud.
18. The impeller of claim 16, wherein the plurality of primary
blades and the plurality of secondary blades are coupled to the
circular plate and the shroud in an integrated manner.
19. The impeller of claim 8, wherein the plurality of secondary
blades each disposed between each of the primary blades are spaced
different distances from each other along a rotation direction of
the impeller.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This U.S. non-provisional patent application claims priority
under 35 U.S.C. .sctn. 119 of Korean Patent Application No.
10-2017-0147057, filed on Nov. 7, 2017 and 10-2017-0171944, filed
on Dec. 14, 2017, the entire contents of which are hereby
incorporated by reference.
BACKGROUND
[0002] The present disclosure herein relates to an impeller, and
more particularly, to an impeller performing blade flow control by
disposing a plurality of secondary blades between a plurality of
primary blades.
[0003] Researches on well-known fluid machinery such as a fan, a
blower, and a pump have been continuously performed for the past
several decades to make progress in design technique. In recent
years, since requirements on noise reduction as well as performance
are enhanced, and sizes of products are reduced, further higher
level of design techniques are required to be developed.
[0004] A typical axial impeller applied to the fluid machinery
exhibits performance thereof by using a pressure and a flow rate.
Specifically, as illustrated in FIG. 1, a pressure difference
(.DELTA.p) between an inlet and an outlet is formed such that while
a fluid passes between blades 1, a streamline is bent along a
curvature of the blade, and a pressure increases by a lift force.
Thus, as the streamline is more bent along a blade camber line 3, a
rotation velocity component is generated to increase a
pressure.
[0005] However, when the streamline is extremely bent, flow
separation progresses at an angle of .alpha..sub.2 instead of an
angle of .alpha..sub.2' that is an angle of a trailing edge (T.E.)
of the blade, and a deviation angle is generated as much as a
difference between .alpha..sub.2 and .alpha..sub.2'
(.alpha..sub.2-.alpha..sub.2' (=.delta.)). Here, as shown in
mathematical equation 1 below, the deviation angle .delta. is a
function of soildity (.sigma.=C/s) that is a ratio of a camber
angle (.PHI..sub.c) at which the blade is bent, a blade chord (C),
and a pitch (s) between the blades. That is, when the camber angle
(.PHI..sub.c) increases, the deviation angle increases, and when
the soildity increases, the deviation angle decreases to improve
performance.
.delta. = .delta. 0 + ( m 0 .sigma. b ) .phi. c [ Mathematical
equation 1 ] ##EQU00001##
[0006] Here, .delta..sub.0 is an air foil shape, mo is the
soildity, and b is a constant determined according to an inlet flow
angle (.alpha..sub.1).
[0007] The related art has been focused to lengthen the chord while
generating great pressure increase through lift force increase by
magnifying the camber angle as large as possible while preventing
flow separation or reducing an outlet deviation angle through
soildity increase by increasing the number of blades and reducing
the pitch between the blades. However, when the chord is
lengthened, the impeller increases in a rotation shaft direction,
and the camber angle for increasing a pressure is restricted due to
flow separation at a negative-pressure surface.
[0008] U.S. Publication Patent No. US 2014/0233178 A1 discloses an
example of improving performance by reducing a deviation angle of a
blade outlet and increasing soildity by using an effect of
lengthened blade as a secondary blade initiates around a trailing
edge (T.E.) of a primary blade. However, the above-described
invention has a limitation in that a height of the impeller
increases, a length of the primary blade increases as much as a
length in which the primary blade and the secondary blade overlap,
and a difference in performance is insignificant.
[0009] Korean Registered Patent No. 10-1342746 discloses a typical
impeller having increasing soildity by installing a plurality of
secondary blades between a plurality of primary blades to reduce a
blade pitch. The above-described impeller has a disadvantage in
that a portion in which primary blades overlap is removed due to
difficulty of injection molding to cause reduction in lift force
and noise increase.
[0010] FIG. 2 illustrates a flow angle and a blade of a backward
centrifugal impeller 20. Mathematical equation 2 shows a
relationship between pressure increase of the impeller and a work
given by Euler equation.
.delta. = .delta. 0 + ( m .sigma. b ) .phi. c [ Mathematical
equation 2 ] ##EQU00002##
[0011] Here, .eta.R is an efficiency of the impeller, i.e., a
percentage (%) of substantial transfer energy except for a flow
loss from theoretical voltage increase caused by internal flow with
respect to theoretical transfer energy.
[0012] A flow discharged from the impeller in FIG. 2 does not flow
along an outlet blade and generates slip. Here, if a slip
coefficient is .mu. when a blade angle is .beta.2b,
.mu. - C .theta. 2 C .theta. 2 , ideal , ##EQU00003##
and a slip coefficient .mu.E is expressed as in mathematical
equation 3 by using Stodola equation.
.mu. E = 1 - .pi. sin .beta. 2 N B ( 1 - C m 2 cot .beta. 2 U 2 ) [
Mathematical equation 3 ] ##EQU00004##
[0013] Here, N.sub.B is the number of blades, .beta..sub.2 is an
outlet flow angle, U.sub.2 and C.sub.m2 are rotation velocity of an
edge of the blade and a radial component of an absolute velocity of
outlet flow, respectively. Referring to mathematical equations 2
and 3, a rotation component C.sub..theta.2 of an absolute velocity
of an outlet necessarily increases in order to improve pressure
transfer, and, to this end, a slip coefficient necessarily
increases by increasing the number of blades as many as
possible.
[0014] U.S. Publication Patent No. US 2009/0155048 A1 discloses an
example of an effect of increasing the number of blades by
installing split vanes, which are secondary blades rotating by
using the same shaft as primary blades, between the primary blades
in a centrifugal pump impeller. In a fan or a blower that requires
flow rate increase instead of pressure increase unlike the
centrifugal pump producing a great static pressure, since a ratio
of a height to a diameter of the impeller is extremely greater than
that of a pump, an upper portion of an impeller blade is
necessarily covered by a typical shroud plate, or an outlet above
the blade is necessarily covered by a circular plate having a
narrow band shape to reinforce rigidity. However, this case has a
difficulty in injection molding.
SUMMARY
[0015] The present invention provides an impeller in which a
plurality of secondary blades are installed between primary blades
without increasing a height of the impeller for performance
improvement and noise reduction in the axial and centrifugal
impeller. In case of the axial impeller, a blade deviation angle is
reduced to improve performance, and a size of a blade wake flow is
reduced, to reduce noises. In case of the centrifugal impeller, as
flow separation at a negative-pressure surface is reduced,
performance improvement and reduction in flow separation noise are
obtained through improvement of a slip constant.
[0016] An embodiment of the present invention provides an impeller
including: a first portion including a first hub and a plurality of
primary blades each extending while being spaced an equal distance
from each other along an outer circumference of the first hub; and
a second portion including a second hub coupled to a lower side of
the first hub by using a projection-groove coupling manner and a
plurality of secondary blades each extending while being spaced
apart from each other along an outer circumference of the second
hub. Here, when a projection angle between a leading edge (L.E.)
and a trailing edge (T.E.) of each of the primary blades is
.theta..sub.1, and a projection angle between a leading edge (L.E.)
and a trailing edge (T.E.) of each of the secondary blades is
.theta..sub.1, the projection angle .PHI..sub.1 and .theta..sub.1
includes an upstream angle .PHI..sub.1u and .theta..sub.1u and a
downstream angle .PHI..sub.1d and .theta..sub.1d, at which the
primary blade and the secondary blade overlap each other, and an
angle .theta..sub.1m and .theta..sub.1m at which the primary blade
and the secondary blade do not overlap each other, and the
projection angle .theta..sub.1 is less than the projection angle
.PHI..sub.1 to satisfy an equation
0<.theta..sub.1<.PHI..sub.1 as a radius of each of the
primary blade and the secondary blade goes from the hub to the
edge.
[0017] In an embodiment, the angles Om and Old of the secondary
blade may have magnitudes overlapping the primary blade so that a
channel around a downstream of a negative-pressure surface of the
primary blade is guided.
[0018] In an embodiment, the first hub may include a plurality of
first coupling projections, which are spaced apart from each other
on a bottom surface thereof, and a plurality of first coupling
grooves that are provided by the plurality of first coupling
projections, the second hub may include a plurality of second
coupling projections, which are spaced apart from each other on a
top surface thereof, and a plurality of second coupling grooves
that are provided by the plurality of second coupling projections,
the plurality of first coupling projections may be coupled to the
plurality of second coupling grooves, and the plurality of second
coupling projections may be coupled to the plurality of first
coupling grooves.
[0019] In an embodiment, the plurality of first coupling
projections may be coupled to the plurality of second coupling
grooves in a pressing manner, and the plurality of second coupling
projections may be coupled to the plurality of first coupling
grooves in a pressing manner
[0020] In an embodiment, the plurality of first coupling
projections may be coupled to the plurality of second coupling
grooves by using an adhesive, and the plurality of second coupling
projections may be coupled to the plurality of first coupling
grooves by using an adhesive.
[0021] In an embodiment, each of the first hub and the second hub
may have a band shape.
[0022] In an embodiment, the first and second hubs may form a
single cone shape when coupled to each other.
[0023] In an embodiment of the present invention, an impeller
includes: a first portion including a circular bottom plate, a hub
protruding from a central portion of a top surface of the circular
bottom plate, and a plurality of primary blades formed in a
circumferential direction with respect to the hub while being
spaced an equal distance from each other on the top surface of the
circular bottom plate; and a second portion including a shroud
having a band shape and a plurality of secondary blades spaced a
distance from each other along a bottom surface of the shroud in an
integrated manner Here, when an inlet area between a
negative-pressure surface of the primary blade and a pressure
surface of the secondary blade is Ssu, an inlet area between the
pressure surface of the primary blade and a negative-pressure
surface of the secondary blade is Spu, a downstream area of a
channel of the negative-pressure surface of the primary blade,
which is an area at a downstream of each channel, is Ssd, and a
downstream area of a channel of the pressure surface of the primary
blade is Spd, an outlet angle of the secondary blade is equal to
that of the primary blade, an inlet of the secondary blade is
disposed at a position at which an S-shape is varied, and an inlet
angle of the secondary blade allows a tangent line of a flow angle
to coincide with a primary streamline of the channel.
[0024] In an embodiment, a leading edge (L.E.) of the secondary
blade may be disposed between channels having the same radial inlet
so hat the areas Ssu and Spu are equal to each other.
[0025] In an embodiment, an outlet angle and an outlet position
between channels may be set by rotating a trailing edge (T.E.) of
the secondary blade to be disposed between channels having the same
radial outlet by using a leading edge (L.E.) of the secondary blade
as a pivot point, thereby maintaining the areas Ssu and Ssd are
similar to each other.
[0026] In an embodiment, the shroud may have a band shape.
[0027] In an embodiment, a plurality of first coupling groove, to
which lower edges of the plurality of secondary blades are
inserted, may be defined in the top surface of the bottom plate,
and a plurality of second coupling groove, to which upper edges of
the plurality of primary blades are inserted, may be defined in the
bottom surface of the shroud.
[0028] In an embodiment, the lower edges of the plurality of
secondary blades may be coupled to the plurality of first coupling
grooves in a pressing manner, and the lower edges of the plurality
of primary blades may be coupled to the plurality of second
coupling grooves in a pressing manner.
[0029] In an embodiment, the lower edges of the plurality of
secondary blades may be coupled to the plurality of first coupling
grooves by using an adhesive, and the lower edges of the plurality
of primary blades may be coupled to the plurality of second
coupling grooves by using an adhesive.
[0030] In an embodiment, the plurality of secondary blades each
disposed between each of the primary blades may be spaced different
distances from each other along a rotation direction of the
impeller.
[0031] In an embodiment, the circular bottom plate and the shroud
may be inclined in a flow downstream direction or formed in a
horizontal direction.
[0032] In an embodiment, the circular bottom plate may have an
outer diameter less than an inner diameter of the shroud.
[0033] In an embodiment, the plurality of primary blades and the
plurality of secondary blades may be coupled to the circular plate
and the shroud in an integrated manner
BRIEF DESCRIPTION OF THE FIGURES
[0034] The accompanying drawings are included to provide a further
understanding of the inventive concept, and are incorporated in and
constitute a part of this specification. The drawings illustrate
exemplary embodiments of the inventive concept and, together with
the description, serve to explain principles of the inventive
concept. In the drawings:
[0035] FIG. 1 is a view for explaining design variables related to
a flow between blades of a general axial impeller and design
variables related to the blades;
[0036] FIG. 2 is a view for explaining design variables related to
a blade of a typical backward centrifugal impeller and a flow
angle;
[0037] FIG. 3 is an assembly perspective view illustrating an axial
impeller according to an embodiment of the present invention;
[0038] FIG. 4 is an exploded perspective view simultaneously
illustrating a bottom surface of a first portion and a top surface
of a second portion of the axial impeller in FIG. 3;
[0039] FIG. 5 is a schematic view illustrating a flow around a
blade of each of the axial impeller according to an embodiment of
the present invention and a typical impeller in conjunction with a
streamline;
[0040] FIG. 6 is a view illustrating a structure between a primary
blade and a secondary blade of the axial impeller according to an
embodiment of the present invention;
[0041] FIG. 7 is an assembly perspective view illustrating a
centrifugal impeller according to another embodiment of the present
invention;
[0042] FIG. 8 is an exploded perspective view simultaneously
illustrating a bottom surface of a first portion and a top surface
of a second portion of the centrifugal impeller in FIG. 7;
[0043] FIG. 9 is a view illustrating an example of a centrifugal
impeller including a primary blade having a backward wake flow
shape (expressed by a solid line) and a secondary blade having a
split vane shape according to another embodiment of the present
invention in conjunction with an example of a centrifugal impeller
including a primary blade having a forward wake flow shape
(expressed by a dotted line);
[0044] FIG. 10 is a cross-sectional view illustrating the primary
blade and the secondary blade of the centrifugal impeller according
to another embodiment of the present invention;
[0045] FIG. 11 is a view illustrating an example of randomly
determining a position of the secondary blade of the centrifugal
impeller between channels instead of determining the position as
same as a rotation direction according to another embodiment of the
present invention;
[0046] FIG. 12 is a perspective view illustrating an impeller
including a mixed flow type primary blade and a secondary blade
according to another embodiment of the present invention;
[0047] FIG. 13 is a plan view illustrating an impeller according to
another embodiment of the present invention; and
[0048] FIG. 14 is a cross-sectional view taken along line A-A of
FIG. 13.
DETAILED DESCRIPTION
[0049] Hereinafter, an axial impeller according to an embodiment of
the present invention and a centrifugal impeller according to
another embodiment will be sequentially described with reference
the drawings.
[0050] FIG. 3 is an assembly perspective view illustrating an axial
impeller according to an embodiment of the present invention, and
FIG. 4 is an exploded perspective view simultaneously illustrating
a bottom surface of a first portion and a top surface of a second
portion of the axial impeller in FIG. 3.
[0051] Referring to FIG. 3, an axial impeller 100 according to an
embodiment of the present invention includes a first portion 110
and a second portion 130, which are manufactured by separate
components. The first portion 110 and the second portion 130, which
are separately manufactured, are coupled to each other to be used
as an impeller.
[0052] Referring to FIG. 4, the first portion 110 includes a first
hub 111 having an approximately ring shape and a plurality of
primary blades 120 spaced an equal distance from each other on an
outer circumferential surface of the first hub 111.
[0053] The first hub 111 may have a hole 113 defined at a central
portion thereof so as to be connected with a predetermined driving
member such as a rotation shaft (not shown), thereby rotating the
axial impeller 100.
[0054] Also, the first hub 111 includes a plurality of first
coupling projections 115 protruding from a bottom surface thereof
and spaced an equal distance from each other along the bottom
surface. In this case, a plurality of coupling grooves 117 to which
a plurality of second coupling projections 135 are inserted are
provided between the first coupling projections 115.
[0055] Each of a plurality of primary blades 120 has one edge
connected to the outer circumferential surface of the first hub 111
in an integrated manner and is gradually bent at a predetermined
curvature in a direction toward the other edge thereof.
[0056] As in FIG. 4, each of the primary blades 120 includes a
negative-pressure surface 121, a pressure surface 123 disposed
opposite to the negative-pressure surface 121, a blade hub surface
125 disposed adjacent to the first hub 111, and a blade tip surface
127 disposed at an edge of the primary blade 120. In this case,
each of the primary blades 120 has an upper edge that is defined as
a leading edge (L.E.) and a lower edge that is defined as a
trailing edge (T.E.).
[0057] The second portion 130 includes a second hub 131 having an
approximately ring shape and a plurality of primary blades 140
spaced an equal distance from each other on an outer
circumferential surface of the second hub 131.
[0058] Also, the second hub 131 may have a hole 133 defined at a
central portion thereof like the first hub 111. In this case, the
second hub 131 may have an outer diameter equal to that of the
first hub 111 and an inner diameter equal to or less than that of
the first hub 111. This structure may fix the impeller 100 to a
rotation shaft or a rotating driving member corresponding to the
rotation shaft.
[0059] Also, a plurality of second coupling projections 135
protrude from a top surface of the second hub 131 and are spaced an
equal distance from each other along the top surface. In this case,
a plurality of second coupling grooves 137 to which a plurality of
first coupling projections 115 are inserted are provided between
the second coupling projections 135.
[0060] As described above, the first and second hubs 111 and 131
are coupled to each other as the plurality of first coupling
projections 115 are inserted to the plurality of second coupling
grooves 137, and the plurality of second coupling projections 135
are inserted to the plurality of first coupling grooves 117. In
this case, the first and second hubs 111 and 131 are coupled in a
mutually pressing state or attached to each other by using a
separate adhesive.
[0061] Each of the plurality of secondary blades 140 has one edge
connected to an outer circumferential surface of the second hub 131
in an integrated manner and is gradually bent at a predetermined
curvature in a direction toward the other edge thereof. Also, when
the first and second hubs 111 and 131 are coupled to each other,
the plurality of secondary blades 140 are disposed below the
plurality of primary blades 120, respectively.
[0062] As in FIG. 4, each of the secondary blades 140 includes a
negative-pressure surface 141, a pressure surface 143 disposed
opposite to the negative-pressure surface 140, a blade hub surface
145 disposed adjacent to the second hub 131, and a blade tip
surface 147 disposed at an edge of the secondary blade 140. In this
case, each of the secondary blades 140 has an upper edge that is
defined as a leading edge (L.E.) and a lower edge that is defined
as a trailing edge (T.E.).
[0063] FIG. 5 is a schematic view illustrating a flow around a
blade of each of the axial impeller according to an embodiment of
the present invention and a typical impeller in conjunction with a
streamline
[0064] Referring to FIG. 5A, when an incidence angle of an inlet is
positive (+) (i.e., an inlet flow is incident toward a pressure
surface more than a camber tangential direction of an inlet blade),
as flow separation is generated above the negative-pressure surface
S due to a camber of the blade, a streamline may not flow along the
blade and be deviated toward the negative-pressure surface more
than a camber tangential direction of a trailing edge of the blade.
In this case, as a thick boundary layer flow processes due to the
flow separation around the trailing edge of the blade, a thick wake
flow of .delta.' is generated. In FIG. 5A, a reference symbol P
represents the pressure surface of the blade.
[0065] In the present invention, the secondary blade 140 is
disposed between two primary blades 120 as in FIG. 5B. Thus, when a
channel flow having inlet areas A2 and A3 is formed, while an
acceleration is rather generated around the inlet area A2, a flow
separation is not generated at a downstream of the pressure surface
121 of the primary blade 120, unlike a case in FIG. 5A, in which a
flow is decelerated from an inlet area A1 between primary blades to
generate flow separation. Also, since a narrow wake thickness
.delta.' is generated at the negative-pressure surface due to
small-sized flow separation, and pressure increase is generated due
to a blade camber as a deviation angle .delta. between channels is
reduced, a camber angle greater than a case without the secondary
blade may be applied.
[0066] FIG. 6 is a view illustrating a relationship between the
primary blade and the secondary blade of the axial impeller
according to an embodiment of the present invention.
[0067] Referring to FIG. 6, a first cylinder projection angle
between the leading edge (L.E.) and the trailing edge (T.E.) of the
primary blade 120 is .PHI.1, and a second cylinder projection angle
between leading edge (L.E.) and the trailing edge (T.E.) of the
secondary blade 140 is .theta.1.
[0068] Also, the first cylinder projection angle .PHI.1 includes an
upstream angle .PHI.1u and a downstream angle .PHI.1d, which
overlap the secondary blade 140, and an angle .PHI.1m not
overlapping the secondary blade 140. Here, .PHI.1u=.theta.1d, and
.PHI.1d=.theta.1u, and these values are varied as a blade radius
goes from the hub to the edge. When .PHI.1=.theta.1, the number of
the same blades becomes two times. Thus, in the present invention,
an equation 0<.theta.1<.PHI.1 is satisfied, i.e., an angle
gap of the secondary blade 140 is less than that of the primary
blade 120, the trailing edge of the secondary blade 140 coincides
with the trailing edge of the primary blade 120 so that a height of
the impeller 100 (refer to FIG. 3) does not increase, and .theta.1u
of the secondary blade is greater than .theta.1d so that a channel
around a downstream of the negative-pressure surface 121 (refer to
FIG. 4) of the primary blade 120 is sufficiently guided.
[0069] As described above, the first hub 111 and the second hub 131
are coupled to each other by the first and second coupling
projections 115 and 135 and the first and second coupling grooves
117 and 137 as in FIG. 3. Here, the trailing edge of the primary
blade 120 corresponding to the downstream angle .PHI.1d of the
primary blade 120 is not attached to the first hub 111, but coupled
with the second hub 132.
[0070] Although not shown in the drawing, each of the first and
second hubs 111 and 131 may have a cone shape instead of the
cylinder shape. For example, when the second hub 131 is coupled to
a lower portion of the first hub 111, an overall integrated cone
shape may be formed. As described above, the first and second hubs
forming the cone shape may be used for a mixed flow impeller.
[0071] FIG. 7 is an assembly perspective view illustrating a
centrifugal impeller according to another embodiment of the present
invention, and FIG. 8 is an exploded perspective view
simultaneously illustrating a bottom surface of a first portion and
a top surface of a second portion of the centrifugal impeller in
FIG. 7.
[0072] Referring to FIG. 7, a centrifugal impeller 200 impeller
according to another embodiment of the present invention includes a
first portion 210 and a second portion 230, which are components
separately manufactured through injection molding, like the
above-described axial impeller 100 according to an embodiment of
the present invention The first portion 210 and the second portion
230 are coupled to each other to be used as an impeller.
[0073] Referring to FIG. 8, the first portion 210 includes a hub
211, a bottom plate 225 formed by a circular plate, and a plurality
of primary blades 220 spaced an equal distance from each other.
[0074] The hub 211 may have a hole 213 defined at a central portion
thereof so as to be connected with a predetermined driving member
such as a rotation shaft (not shown), thereby rotating the
centrifugal impeller 200. The hub 211 may have an approximately
cone shape.
[0075] The hub 211 has a lower edge connected to a central portion
of a top surface of the bottom plate 215 in an integrated manner.
The plurality of primary blades 220 are spaced an equal distance
from each other along a circumferential direction on the bottom
plate 215, and lower edges of the plurality of primary blades 220
are connected to the top surface of the bottom plate 215 in an
integrated manner.
[0076] Also, a plurality of first coupling grooves 217, to which
lower edges of a plurality of secondary blades 240 that will be
described later are inserted between neighboring primary blades
220, are defined in the top surface of the bottom plate 215.
[0077] Each of the plurality of primary blades 220 has a leading
edge (L.E.) disposed adjacent to an outer circumferential surface
of the first hub 211 and is gradually bent at a predetermined
curvature in a direction from the leading edge (L.E.) to a trailing
edge (T.E.).
[0078] Each of the primary blades 220 includes a negative-pressure
surface 221, a pressure surface disposed opposite to the
negative-pressure surface, a blade bottom surface 225 adjacent to
the bottom plate 215, and a blade top surface 227 adjacent to a
shroud 231 of the second portion 230, which will be described
later. In this case, each of the primary blades 220 has an inside
edge that is defined as a leading edge (L.E.) and an outside edge
that is defined as a trailing edge (T.E.).
[0079] The second portion 230 includes a shroud 231 having an
approximately ring shape and a plurality of secondary blades 240
spaced an equal distance from each other along a bottom surface of
the shroud 231. In this case, each of the plurality of secondary
blades 240 may have an arc shape or an S-shape.
[0080] The shroud 231 may have an outer diameter that is
approximately equal to that of the bottom plate 215. Also, a
plurality of second coupling grooves 233, to which the plurality of
primary blades 220 are inserted, are defined between the plurality
of secondary blades 240 in a bottom surface of the shroud 231. A
portion of an upper edge of each of the plurality of primary blades
220 may be inserted to each of the plurality of second coupling
grooves 233.
[0081] As described above, as lower edges of the plurality of
secondary blades 240 are inserted to the plurality of first
coupling grooves 217, respectively, and upper edges of the
plurality of primary blades 220 are inserted to the second coupling
grooves 233, respectively, the first and second portions 210 and
230 are coupled to each other. In this case, each of coupled
portions are coupled in a mutually pressing manner or attached to
each other by using a separate adhesive.
[0082] Each of the plurality of secondary blades 240 includes a
negative-pressure surface 241, a pressure surface 243 disposed
opposite to the negative-pressure surface, a blade bottom surface
245, and a blade top surface 247 adjacent to the shroud 231. In
this case, each of the secondary blades 240 has an inside edge that
is defined as a leading edge (L.E.) and an outside edge that is
defined as a trailing edge (T.E.).
[0083] FIG. 9 is a view illustrating an example of a centrifugal
impeller including a primary blade having a backward wake flow
shape (expressed by a solid line) and a secondary blade having a
split vane shape according to another embodiment of the present
invention in conjunction with an example of a centrifugal impeller
including a primary blade having a forward wake flow shape
(expressed by a dotted line), and FIG. 10 is a cross-sectional view
illustrating the primary blade and the secondary blade of the
centrifugal impeller according to another embodiment of the present
invention.
[0084] Referring to FIG. 9, the wake flow is expressed by a solid
line when the primary blade of the centrifugal impeller has the
backward wake flow shape, and the wake flow is expressed by a
dotted line when the primary blade of the centrifugal impeller has
the forward wake flow shape.
[0085] In this case, at a backward blade bent in a direction
opposite to a rotation direction, a wide wake flow between blades
caused by slip exists except for the pressure surface as expressed
by a blue solid line. Also, at a forward blade bent in the same
direction as the rotation direction, great flow separation is
generated at the negative-pressure surface as an outlet of the
primary blade is bent in the rotation direction as expressed by an
orange solid line, and an energy loss of the wake is greater than
that at an outlet of the blade at the backward blade. However, a
pressure energy increase is relatively great as C.theta.2 of the
above mathematical equation 2 increases, which is a relative
velocity at the outlet in the rotation direction.
[0086] Although S-shaped hybrid blades are illustrated in FIG. 10
in order to use advantages of a high efficiency of the backward
blade and a high pressure energy of the forward blade at the same
time, as a channel is divided into two portions as in the axial
impeller by installing the secondary blade called a split vane
between the primary blades to overcome the great flow separation of
the negative-pressure surface of the forward blade, slip and wake
flow at the negative-pressure surface of the primary blade are
reduced as expressed by a green solid line, and wake flow exists
only at the negative-pressure surface of the secondary blade in
conjunction with small flow separation. Thus, this flow type is the
most preferable among three flow types.
[0087] In FIG. 9, reference symbols U2 and Cm2 are a rotation
velocity of a blade edge and a radial component of an absolute
velocity of an outlet flow, respectively, a reference symbol
C.theta.2 is a rotation component of an outlet absolute velocity,
and reference symbols C2 and W2 are a magnitude of an outlet
absolute velocity vector and a magnitude of an outlet relative
velocity vector, respectively.
[0088] Referring to FIG. 10, the channel of the hybrid blade
installing the secondary blade includes: an inlet area Ssu (here,
the suffix u represents the upstream) between the negative-pressure
surface of the primary blade and the pressure surface of the
secondary blade; an inlet area Spu between the pressure surface of
the primary blade and the negative-pressure surface of the
secondary blade; and an areas Ssd and Spd at each channel
downstream. Since an inlet height and an outlet height of the blade
are generally similar to each other, a flow separation is generated
by pressure increase and velocity decrease as an outlet area
increases more than an inlet area because a radius increases in a
direction toward the blade downstream.
[0089] The present invention maintains an outlet angle of the
secondary blade to be similar to an outlet angle .beta..sub.2b
(refer to FIG. 2) of the primary blade and initiates an inlet of
the secondary blade around a position at which the S-shape is
varied, so that an inlet angle of the secondary blade allows a flow
angle tangent line to coincide with a primary streamline between
the channels in order to prevent the inlet area Ssu and the outlet
area Ssd of the channel of the negative-pressure surface of the
primary blade from being greatly varied. Also, since the area Ssu
is less than the area Spu among the vertical areas of the channels
although the secondary blade is disposed at a central portion of
two primary blades, the leading edge (L.E.) of the secondary blade
may move between channels having the same radial inlet so that the
two areas are equal to each other, and as the leading edge (L.E.)
of the secondary blade at the previously obtained position moves to
a pivot point, and the trailing edge (T.E.) of the secondary blade
moves between channels having the same radial outlet so that the
area Ssu is similar to the area Ssd, an outlet angle and an outlet
position between the channels may be determined.
[0090] FIG. 11 is a view illustrating an example of randomly
determining a position of the secondary blade of the centrifugal
impeller between channels instead of determining the position as
same as a rotation direction according to another embodiment of the
present invention.
[0091] The present invention randomly determines a position between
the channels of the secondary blade of the centrifugal impeller as
in FIG. 11 instead of determining the position as same as the
rotation direction in order to cancel phases of a flow separation
vortex above the negative-pressure surface of the secondary blade
and a vortex passing through the channel In this case, the position
may be determined so that a thrust and a torque balance of a shaft
vertical surface are obtained by lift force distribution.
[0092] The centrifugal impeller 200 in FIG. 7 is obtained by
coupling the first portion 210 and the second portion 230 to each
other, and the first and second portions 210 and 230 are separately
manufactured. However, the embodiment of the present invention is
not limited thereto. For example, an impeller having an integrated
body may be provided. Hereinafter, detailed description will be
described with reference to FIGS. 12 to 14.
[0093] FIG. 12 is a perspective view illustrating an impeller
including a mixed flow type primary blade and a secondary blade
according to another embodiment of the present invention, FIG. 13
is a plan view illustrating an impeller according to another
embodiment of the present invention, and FIG. 14 is a
cross-sectional view taken along line A-A of FIG. 13.
[0094] Referring to FIGS. 12 to 14, an impeller 300 according to
another embodiment of the present invention may be manufactured
such that an outer diameter of a circular bottom plate 315 is
slightly less than an inner diameter of a shroud 331 to inject a
single body.
[0095] In this case, although all of the circular bottom plate 315
and the shroud 331 are formed inclined to a flow downstream
direction as in FIG. 14, the embodiment of the present invention is
not limited thereto. For example, all of the circular bottom plate
315 and the shroud 331 may be formed in a horizontal direction to
be perpendicular to a rotation shaft direction.
[0096] Also, a plurality of primary blades 320 and a plurality of
secondary blades 330 of the impeller 300 may be integrated with the
shroud 331 and the circular bottom plate 315 or a hub 317 so as to
be manufactured by using a single mold. That is, each of the
plurality of primary blades 320 may have an upper edge connected to
the shroud 331 and a lower edge connected to the circular bottom
plate 315 or the hub 317. Also, each of the plurality of secondary
blades 330 may have an upper edge connected to the shroud 331 and a
lower edge connected to the circular bottom plate 315 or the hub
317.
[0097] In this case, the plurality of primary blades 320 and the
plurality of secondary blades 330 may be alternately formed along a
circumferential direction.
[0098] The axial impeller 200 in FIG. 7 operates such that a flow
is introduced in a rotation shaft direction and then discharged in
a radial direction perpendicular to the rotation shaft direction as
a pressure increases. However, the mixed flow type impeller 300 in
FIG. 12 operates such that a flow is introduced in a rotation shaft
direction and then discharged in a direction inclined at a
predetermined angle with respect to the rotation shaft direction as
a pressure increases in a manner similar to the axial impeller. In
this case, the mixed flow impeller 300 may form a flow path equal
to the flow direction of the streamline in FIG. 14.
[0099] As described above, the impeller according to the present
invention, in which the secondary blades are disposed between the
primary blades, has an advantage with respect to each of the axial
type and the centrifugal type as stated below.
[0100] In case of the axial impeller according to the present
invention, effects of pressure increase and noise reduction may be
obtained by reducing secondary flow at the negative-pressure
surface of the main blade and reducing the deviation angle at the
trailing edge of the blade. Also, when the plurality of secondary
blades are disposed between the plurality of primary blades not to
increase the height of the impeller, the first portion including
the upper hub to which the plurality of primary blades are
connected and the second portion including the lower hub to which
the plurality of secondary blades are connected may be separately
injection-molded, and the upper hub and the lower hub may each have
a band shape having a circumferential radial thickness and be
coupled to each other in the projection-groove coupling manner.
Thus, a limitation of hardly separating upper and lower molds
during the injection molding process because the blades overlap
each other may be fundamentally resolved.
[0101] In case of the centrifugal impeller according to the present
invention, effects of energy transfer increase and noise reduction
may be obtained through reduction of blade slip by reducing the
secondary flow at the negative-pressure surface of the primary
blade having the backward and forward or radial combined hybrid
S-shape. Also, as the first portion including the bottom plate to
which the plurality of primary blades are attached and the second
portion including the shroud having the band shape to which the
plurality of secondary blades are attached are injection-molded as
separate components, and the plurality of primary blades are
coupled to the shroud in the projection-groove coupling manner, and
the plurality of secondary blades are coupled to the bottom plate
in the projection-groove coupling manner, a limitation generated
during the injection molding may be resolved.
[0102] Although the exemplary embodiments of the present invention
have been described, it is understood that the present invention
should not be limited to these exemplary embodiments but various
changes and modifications can be made by one ordinary skilled in
the art within the spirit and scope of the present invention as
hereinafter claimed. Hence, all changes, modifications, or
alterations should therefore be seen as within the scope of the
invention.
* * * * *