U.S. patent application number 11/680010 was filed with the patent office on 2007-09-20 for dovetail structure of fan.
This patent application is currently assigned to ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES CO., LTD.. Invention is credited to Tetsuji Fujimura, Takashi Oka.
Application Number | 20070217915 11/680010 |
Document ID | / |
Family ID | 37908789 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070217915 |
Kind Code |
A1 |
Fujimura; Tetsuji ; et
al. |
September 20, 2007 |
DOVETAIL STRUCTURE OF FAN
Abstract
The invention provides a dovetail structure of a fan which
attaches the fan 20 having an inlet hub diameter smaller than an
outlet hub diameter to a portion around a discoid disc 10
rotationally driven by a turbine. The disc 10 has a plurality of
main dovetail grooves 12 extending in parallel to an axis 1 of a
rotation axis from a leading edge to a trailing edge thereof. The
fan 20 has a main dovetail portion 22 fitted to the main dovetail
groove 12, and a sub engagement portion 24 for supporting a front
centrifugal force. Further, the dovetail structure is provided with
a spin cone 30 engaging with the sub engagement portion 24 so as to
be capable of transmitting the front centrifugal force to the disc
10.
Inventors: |
Fujimura; Tetsuji; (Tokyo,
JP) ; Oka; Takashi; (Tokyo, JP) |
Correspondence
Address: |
GRIFFIN & SZIPL, PC
SUITE PH-1, 2300 NINTH STREET, SOUTH
ARLINGTON
VA
22204
US
|
Assignee: |
ISHIKAWAJIMA-HARIMA HEAVY
INDUSTRIES CO., LTD.
Tokyo
JP
|
Family ID: |
37908789 |
Appl. No.: |
11/680010 |
Filed: |
February 28, 2007 |
Current U.S.
Class: |
416/219R |
Current CPC
Class: |
F01D 5/3015 20130101;
Y02T 50/60 20130101; Y02T 50/671 20130101 |
Class at
Publication: |
416/219.R |
International
Class: |
F01D 5/30 20060101
F01D005/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2006 |
JP |
068517/2006 |
Claims
1. A dovetail structure of a fan which attaches the fan having an
inlet hub diameter smaller than an outlet hub diameter to a portion
around a discoid disc rotationally driven by a turbine, wherein the
disc has a plurality of main dovetail grooves extending in parallel
to an axis of a rotation axis from a leading edge to a trailing
edge thereof, and spaced at a fixed angle in a peripheral
direction, wherein the fan has a main dovetail portion fitted to
the main dovetail groove so as to be capable of transmitting a rear
centrifugal force applied to a portion from an intermediate portion
to a trailing edge, and a sub engagement portion for supporting a
front centrifugal force applied to a portion from a leading edge to
the intermediate portion, and wherein the dovetail structure is
provided with a spin cone engaging with the sub engagement portion
so as to be capable of transmitting the front centrifugal force to
the disc.
2. The dovetail structure of the fan as claimed in claim 1, wherein
the fan is constituted by a zero hub ratio fan which is capable of
sucking an air close to a center of rotation, and in which a
substantial inlet hub diameter is zero or close to zero, and a
hub/tip ratio is between 0 and 0.35.
3. The dovetail structure of the fan as claimed in claim 1, wherein
the sub engagement portion is constituted by a projection portion
which is provided in an inner end portion of a forward end of the
fan, and has an outer peripheral surface spaced at a fixed distance
R from the axis of the rotating shaft, and the spin cone has a
concave groove having an inner peripheral surface fitted to an
outer peripheral surface of the projection portion, and a faucet
portion fitted to a cylindrical inner surface provided in the
disc.
4. The dovetail structure of the fan as claimed in claim 1, wherein
the sub engagement portion is constituted by a plurality of slope
dovetail portions extending at a fixed angle with respect to the
axis of the rotating shaft from the leading edge of the fan to the
intermediate portion, and spaced at a fixed angle in a peripheral
direction, and the spin cone has a plurality of slope dovetail
grooves fitted to the slope dovetail portions, and a faucet portion
fitted to the cylindrical inner surface provided in the disc.
5. The dovetail structure of the fan as claimed in claim 1, wherein
the sub engagement portion has a plurality of parallel dovetail
portions extending in parallel to the axis of the rotating shaft
from the leading edge of the fan to the intermediate portion, and
spaced at a fixed angle in a peripheral direction, and the spin
cone has a plurality of parallel dovetail grooves fitted to the
parallel dovetail portions, and a faucet portion fitted to the
cylindrical inner surface provided in the disc.
6. The dovetail structure of the fan as claimed in claim 1, wherein
the sub engagement portion is constituted by a plurality of
expanded portions extending from the leading edge of the fan to the
intermediate portion and spaced at a fixed angle in a peripheral
direction, and the spin cone has a plurality of fitting grooves
fitted to a front lower edge of the fan in an upper portion than
the expanded portions, and a faucet portion fitted to the
cylindrical inner surface provided in the disc.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field of the Invention
[0002] The present invention relates to a turbofan engine which has
a high bypass ratio and can achieve a good mileage and a low noise,
and more particularly to a dovetail structure of a fan in which an
inlet hub diameter is smaller than an outlet hub diameter.
[0003] 2. Description of the Related Art
[0004] FIG. 1 is a schematic view of an aircraft engine 51 (a
turbojet engine). As shown in this drawing, the turbojet engine is
provided with a fan 52 taking in an air, a compressor 53
compressing the intake air, a burning device 54 burning a fuel by
the compressed air, a turbine 55 driving the fan 52 and the
compressor 53 on the basis of a combustion gas of the burning
device 54, an afterburner 56 afterburning for increasing a thrust,
and the like.
[0005] The afterburner 56 is constituted by a flame holder 57
having a triangular cross section or the like and forming a
circulating region in a downstream side so as to achieve a flame
holding, a fuel nozzle 58 for jetting out a fuel, a spark plug 59
and the like, jets out from an exhaust nozzle 62 through an inner
side of a liner 61 in an inner side of an after duct 60, and
increases a thrust.
[0006] In the turbojet engine mentioned above, a structure in which
the fan 52 taking in the air is enlarged in size, and a bypass
ratio is enlarged is called "turbofan engine". The bypass ratio
corresponds to a flow ratio (bypass flow/core flow) of a bypass
flow bypassing a core engine (the compressor 53, the burning device
54 and the turbine 55 mentioned above) with respect an air flow (a
core flow) flowing into the core engine. The larger the bypass
ratio is, the more the flow rate of the exhaust jet is reduced, so
that there is obtained an effect of lowering a noise and a specific
fuel consumption.
[0007] However, in the turbo engine mentioned above, if the bypass
ratio is enlarged, a fan first stage rotor blade (a fan blade in
the front row) and an inner diameter of a casing surrounding it
become enlarged, and there is a problem that a weight of the engine
is increased.
[0008] In other words, since a fan first stage rotor blade 52a
having a structure embedded in a spinner 63 of the turbofan engine
has an embedded structure, a certain degree of hub/tip ratio (inlet
hub diameter/tip diameter shown in FIG. 2: normally about 0.3) is
necessary, and a fan inlet area becomes narrower at an area
corresponding to the inlet hub diameter.
[0009] Accordingly, if it is intended to increase the bypass ratio
in order to achieve the good mileage and the low noise, the fan
diameter and the inlet hub diameter become further larger, and the
weight of the engine is increased.
[0010] Then, in order to solve the problem, the same applicant as
that of the present invention has already proposed "turbofan
engine" in patent document 1.
[0011] The turbofan engine is provided with a fan first stage rotor
blade 65 for taking in an air, and a spinner 64 rotationally
driving the fan first stage rotor blade, as shown in FIG. 3, and
the spinner has a spiral blade 66 extending spirally to an outer
side in a radial direction from an axis thereof and sucking the air
from a front surface of the spinner so as to supply to the fan
first stage rotor blade.
[0012] In this case, reference numerals 67 and 67' denote a casing
inner diameter, and reference numeral 68 denotes an inflow air
flow.
[0013] In accordance with the structure of the patent document 1,
since the spinner 64 has the spiral blade 66 extending spirally to
the outer side in the radial direction from the axis thereof and
sucking the air from the front surface of the spinner so as to
supply to the fan first stage rotor blade 65, it is possible to
suck the air from the front surface of the spinner corresponding to
the inlet hub diameter so as to compress the air and supply to the
fan first stage rotor blade 65.
[0014] Therefore, since an entire area in the front side of the
engine becomes the air inflow area of the fan first stage rotor
blade 65, it is possible to make the fan diameter small, and it is
possible to reduce the engine weight.
[0015] Further, since the fan first stage rotor blade 65 and the
spiral blade 66 of the turbofan engine mentioned above are
integrally coupled, it is possible to connect the respective blade
surfaces smoothly, and it is possible to suck and compress the air
efficiently. Hereinafter, the fan in which the fan first stage
rotor blade 65 and the spiral blade 66 are integrally formed, the
air can be sucked from the front surface of the spinner, and the
substantial hub/tip ratio can be set to 0 is called as "zero hub
tip ratio fan".
[0016] Patent Document 1: Japanese Unexamined Patent Publication
No. 2004-27854, "TURBOFAN ENGINE"
[0017] Patent Document 2: U.S. Pat. No. 6,764,282, "BLADE FOR
TURBINE ENGINE"
[0018] It is necessary to attach the fan blade of the turbofan
engine to a portion around a discoid disc (or spinner) rotationally
driven by a turbine. Accordingly, in conventional, there has been
generally employed a dovetail structure in which a dovetail portion
extending in a longitudinal direction is provided in a root portion
of the fan blade, and the dovetail portion is fitted to a dovetail
groove formed around the disc.
[0019] In the conventional dovetail structure mentioned above, the
dovetail portion and the dovetail groove are provided in parallel
to a rotation axis Z-Z of the disc, thereby preventing a
centrifugal force applied to the fan blade from generating a
component force in an axial direction. Hereinafter, this structure
is called as "parallel dovetail structure".
[0020] However, in the case that a diameter change in an inner side
of a donut-shaped flow path to which the fan blade is attached is
large, if the parallel dovetail structure is employed, it is
necessary to make a diameter of the dovetail portion and the
dovetail groove equal to or smaller than a minimum diameter of the
flow path, and there is a risk that a stress generated in the
dovetail portion and the dovetail groove becomes too large.
[0021] Accordingly, there has been proposed a dovetail structure in
which the dovetail portion and the dovetail groove shown in FIG. 4
are sloped with respect to the rotation axis (for example, patent
document 2). In this drawing, reference numeral 71 denotes a disc,
reference numeral 73 denotes a blade, reference numeral 77 denotes
a dovetail, and reference numeral 79 denotes a tab.
[0022] Hereinafter, this structure is called as "slope dovetail
structure".
[0023] However, in the case of the zero hub tip ratio fan mentioned
above, since the hub/tip ratio is between 0 and 0.35, and the
diameter of the inner side of the donut-shaped flow path to which
the zero hub tip ratio fan is attached is zero or close to zero,
there is a problem that the parallel dovetail structure can not be
essentially applied.
[0024] Further, even in the case that the slope dovetail structure
is applied, it is impossible to support the centrifugal force of
the front side portion (the portion corresponding to the spiral
blade mentioned above) of the zero hub tip ratio fan by the disc
(or the spinner).
[0025] Further, in the case that the slope dovetail structure is
applied to the zero hub tip ratio fan, since the component force in
the axial direction of the centrifugal force applied to the fan
blade is large, there is a risk that the generated stress becomes
too large in the structure having a small shear area such as the
tab disclosed in the patent document 2.
SUMMARY OF THE INVENTION
[0026] The present invention is made for the purpose of solving the
problems mentioned above. In other words, an object of the present
invention is to provide a dovetail structure of a fan which can
securely attach a fan having an inlet hub diameter smaller than an
outer hub diameter to a portion around a disc rotationally driven
by a turbine, and can securely support component forces in a radial
direction and an axial direction of a centrifugal force applied to
the fan having the inlet hub diameter smaller than the outlet hub
diameter by a low stress.
[0027] In accordance with the present invention, there is provided
a dovetail structure of a fan which attaches a fan having an inlet
hub diameter smaller than an outlet hub diameter to a portion
around a discoid disc rotationally driven by a turbine,
[0028] wherein the disc has a plurality of main dovetail grooves
extending in parallel to an axis of a rotation axis from a leading
edge to a trailing edge thereof, and spaced at a fixed angle in a
peripheral direction,
[0029] wherein the fan has a main dovetail portion fitted to the
main dovetail groove so as to be capable of transmitting a rear
centrifugal force applied to a portion from an intermediate portion
to a trailing edge, and a sub engagement portion for supporting a
front centrifugal force applied to a portion from a leading edge to
the intermediate portion, and
[0030] wherein the dovetail structure is provided with a spin cone
engaging with the sub engagement portion so as to be capable of
transmitting the front centrifugal force to the disc.
[0031] In accordance with a preferable aspect of the present
invention, the fan is constituted by a zero hub ratio fan which is
capable of sucking an air close to a center of rotation, and in
which a substantial inlet hub diameter is zero or close to zero,
and a hub/tip ratio is between 0 and 0.35.
[0032] Further, the sub engagement portion is constituted by a
projection portion which is provided in an inner end portion of a
forward end of the fan, and has an outer peripheral surface spaced
at a fixed distance R from the axis of the rotating shaft, and
[0033] the spin cone has a concave groove having an inner
peripheral surface fitted to an outer peripheral surface of the
projection portion, and a faucet portion fitted to a cylindrical
inner surface provided in the disc.
[0034] Further, in accordance with the other preferable embodiment,
the sub engagement portion is constituted by a plurality of slope
dovetail portions extending at a fixed angle with respect to the
axis of the rotating shaft from the leading edge of the fan to the
intermediate portion, and spaced at a fixed angle in a peripheral
direction, and
[0035] the spin cone has a plurality of slope dovetail grooves
fitted to the slope dovetail portions, and a faucet portion fitted
to the cylindrical inner surface provided in the disc.
[0036] Further, in accordance with the other preferable embodiment,
the sub engagement portion has a plurality of parallel dovetail
portions extending in parallel to the axis of the rotating shaft
from the leading edge of the fan to the intermediate portion, and
spaced at a fixed angle in a peripheral direction, and
[0037] the spin cone has a plurality of parallel dovetail grooves
fitted to the parallel dovetail portions, and a faucet portion
fitted to the cylindrical inner surface provided in the disc.
[0038] Further, in accordance with the other preferable embodiment,
the sub engagement portion is constituted by a plurality of
expanded portions extending from the leading edge of the fan to the
intermediate portion and spaced at a fixed angle in a peripheral
direction, and
[0039] the spin cone has a plurality of fitting grooves fitted to a
front lower edge of the fan in an upper portion than the expanded
portions, and a faucet portion fitted to the cylindrical inner
surface provided in the disc.
[0040] In accordance with the structure of the present invention
mentioned above, since the disc has the main dovetail groove
extending in parallel to the axis of the rotation axis from the
leading edge to the trailing edge, and the fan having the inlet hub
diameter smaller than the outlet hub diameter has the main dovetail
portion extending at the same angle as the angle of the dovetail
groove and capable of being fitted to the dovetail groove, it is
possible to securely attach the fan to the portion around the disc,
and it is possible to securely transmit the rear centrifugal force
applied to the fan to the disc via the main dovetail portion and
the main dovetail groove.
[0041] Further, since the main dovetail portion and the main
dovetail groove extend in parallel to the axis of the rotation
axis, it is possible to set a sufficient long main dovetail groove
capable of transmitting the rear centrifugal force applied to the
portion from the intermediate portion to the trailing edge, even in
the case of attaching the fan having the inlet hub diameter smaller
than the outlet hub diameter, and it is possible to sufficiently
suppress the stress generated in the main dovetail portion and the
main dovetail groove.
[0042] Further, since the fan has the sub engagement portion for
supporting the front centrifugal force applied to the portion from
the leading edge to the intermediate portion, and is provided with
the spin cone engaging with the sub engagement portion so as to be
capable of transmitting the front centrifugal force to the disc, it
is possible to securely support the front centrifugal force applied
to the portion having the small hub diameter of the fan in which
the inlet hub diameter is smaller than the outlet hub diameter, via
the spin cone so as to be capable of securely transmitting to the
disc.
[0043] Further, since the rear centrifugal force applied to the
portion from the intermediate portion to the trailing edge is
transmitted to the disc by the main dovetail groove and the main
dovetail portion extending in parallel to the axis of the rotating
shaft, it is possible to make the component force along the main
dovetail groove of the centrifugal force applied to the fan in
which the inlet hub diameter is smaller than the outlet hub
diameter small, and it is possible to securely support the
component force by the low stress on the basis of the retainer
structure having the same structure as the conventional one.
[0044] The other objects and advantageous features of the present
invention will be apparent from the following description with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a schematic view of a conventional turbofan
engine;
[0046] FIG. 2 is an explanatory view of a hub/tip ratio;
[0047] FIG. 3 is a schematic view of "turbofan engine" in patent
document 1;
[0048] FIG. 4 is a schematic view of "slope dovetail structure" in
patent document 2;
[0049] FIG. 5 is a transverse cross sectional view of a fan
provided with a dovetail structure in accordance with a first
embodiment of the present invention;
[0050] FIGS. 6A, 6B, 6C and 6D are partly cross sectional views of
FIG. 5;
[0051] FIG. 7 is a view of a second embodiment of the dovetail
structure in accordance with the present invention;
[0052] FIGS. 8A, 8B and 8C are partly perspective views and a
partly cross sectional view of FIG. 7;
[0053] FIG. 9 is a view of a third embodiment of the dovetail
structure in accordance with the present invention;
[0054] FIG. 10 is a partly perspective view of FIG. 9;
[0055] FIG. 11 is a view of a fourth embodiment of the dovetail
structure in accordance with the present invention; and
[0056] FIGS. 12A and 12B are partly perspective views of FIG.
11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0057] A description will be given below of a preferable embodiment
in accordance with the present invention with reference to the
accompanying drawings. In this case, in each of the drawings, the
same reference numerals are attached to a common portion, and an
overlapping description will be omitted.
[0058] FIG. 5 is a transverse cross sectional view of a fan
provided with a dovetail structure in accordance with a first
embodiment of the present invention, and shows only an upper side
of an axis 1 of a rotating shaft.
[0059] Further, FIGS. 6A, 6B, 6C and 6D are partly cross sectional
views of FIG. 5, and are respectively cross sectional views along a
line A-A, a line B-B, a line C-C and a line D-D.
[0060] A dovetail structure in accordance with the present
invention is structured such that a fan in which an inlet hub
diameter is smaller than an outlet hub diameter is attached to a
portion around a discoid disc 10 rotationally driven by a turbine
(not shown).
[0061] Further, in this embodiment, the fan is constituted by a
zero hub tip ratio fan which can suck an area close to a center of
rotation, and in which a substantial inlet hub diameter is zero or
close to zero, and a hub/tip ratio is between 0 and 0.35.
[0062] In this case, in FIG. 5, reference numeral 1 denotes an axis
of a rotating shaft of a disc 10 and the zero hub tip ratio fan 20,
reference numeral 2 denotes an air flow path, reference numeral 3
denotes an inner peripheral surface of the air flow path, reference
numeral 4 denotes a bearing rotatably supporting the disc 10, and
reference numeral 5 denotes a flow of an inflow air.
[0063] The zero hub tip ratio fan 20 is formed such that a fan
first stage rotor blade 20a for taking in the air and a spiral
blade 20b sucking the air from the portion close to the center of
rotation so as to compress and supply to the fan first stage rotor
blade are integrally coupled, and respective blade surfaces are
smoothly connected. In this case, the substantial hub/tip ratio of
the zero hub tip ratio fan 20 is not 0, but can be set to 0.
[0064] In FIGS. 5, 6A, 6B, 6C and 6D, the disc 10 has a plurality
of (for example, eighteen in this embodiment) main dovetail grooves
12 spaced at a fixed angle (for example, 20 degree in this
embodiment) in a peripheral direction. Further, the main dovetail
grooves 12 extend in parallel to the axis 1 of the rotating shaft
from a leading edge 10a to a trailing edge 10b of the disc 10.
[0065] The zero hub tip ratio fan 20 has a main dovetail portion 22
in an inner end thereof. The main dovetail portion 22 extends in
parallel to the axis 1 of the rotating shaft in the same manner as
the main dovetail groove 12 of the disc 10, and is structured such
as to be capable of being fitted to the main dovetail groove
12.
[0066] It is preferable that the main dovetail portion 22 is
provided at a position corresponding to a fan first stage rotor
blade 20a, and is structured such as to be capable of transmitting
a rear centrifugal force applied to a portion from an intermediate
portion to a trailing edge of the fan to the disc 10.
[0067] The zero hub tip ratio fan 20 further has a sub engagement
portion 24 for supporting a front centrifugal force applied to a
portion from a leading edge to the intermediate portion of the fan.
The sub engagement portion 24 is preferably provided at a position
corresponding to a spiral blade 20b. In this case, reference
numeral 26 in this drawing denotes a platform portion constituting
the inner peripheral surface 3 of the air flow path 2 of the zero
hub tip ratio fan 20.
[0068] In FIG. 5, the dovetail structure in accordance with the
present invention is further provided with a spin cone 30 capable
of being fixed to the disc 10 by a coupling bracket 15 in a forward
side (a left side in the drawing) of the zero hub tip ratio fan 20.
The spin cone 30 engages with the sub engagement portion 24 of the
zero hub tip ratio fan 20 and has a function of transmitting a
front centrifugal force applied to the portion from the leading
edge to the intermediate portion of the fan to the disc 10.
[0069] In the first embodiment in FIG. 5, the sub engagement
portion 24 is constituted by a projection portion 25 which is
provided in an inner end portion of a forward end of the zero hub
tip ratio fan 20, and has an outer peripheral surface 25a spaced at
a fixed distance R from the axis 1 of the rotating shaft.
[0070] Further, in this embodiment, the spin cone 30 has a concave
groove 31 having an inner peripheral surface fitted to the outer
peripheral surface 25a of the projection portion 25, and a faucet
portion 37 fitted to a cylindrical inner surface 10c provided in
the disc 10.
[0071] In this embodiment, the spin cone 30 has a cone head 36
attached to a leading end thereof by a coupling bracket 35.
[0072] In the case of the zero hub tip ratio fan 20 in which a
substantial inlet hub diameter is zero or close to zero, a flow
path diameter of the inner peripheral surface 3 of the air flow
path 2 is largely changed from zero or a small diameter close to
zero to a large diameter reaching three times or more (about three
times in this embodiment) thereof. Accordingly, a diameter of outer
peripheral surface 25a of the projection portion 25 becomes equal
to or less than one third of the maximum diameter of the mounting
portion of the main dovetail portion 22.
[0073] Further, the front centrifugal force applied to the portion
from the leading edge to the intermediate portion of the fan
corresponds to a centrifugal force applied to the spiral blade 20b
positioned in an outer side thereof, and is smaller in comparison
with a rear centrifugal force applied to the portion from the
intermediate portion to the trailing edge of the fan.
[0074] Accordingly, it is possible to support the front centrifugal
force on the basis of the engagement between the projection portion
25 provided in the inner end portion of the forward end and the
concave groove 31 of the spin cone 30.
[0075] In accordance with the structure mentioned above, since the
disc 10 has the main dovetail groove 12 extending in parallel to
the axis 1 of the rotating shaft from the leading edge 10a to the
trailing edge 10b, and the zero hub tip ratio fan 20 has the main
dovetail portion 22 which is fitted to the main dovetail groove and
can transmit the rear centrifugal force applied to the portion from
the intermediate portion to the trailing edge, it is possible to
securely attach the zero hub tip ratio fan 20 to the portion around
the disc 10, and it is possible to securely transmit the rear
centrifugal force applied to the zero hub tip ratio fan 20 to the
disc 10 via the main dovetail portion 22 and the main dovetail
groove 12.
[0076] Further, since the main dovetail portion 22 and the main
dovetail groove 12 extend in parallel to the axis 1 of the rotating
shaft, it is possible to set the sufficiently long main dovetail
groove which can transmit the rear centrifugal force applied to the
portion from the intermediate portion to the trailing edge, even in
the case of attaching the zero hub tip ratio fan in which the
substantial inlet hub diameter is zero or close to zero, and it is
possible to suppress the stress generated in the main dovetail
portion 22 and the main dovetail groove 12 sufficiently small.
[0077] Further, since the zero hub tip ratio fan 20 has the sub
engagement portion 24 (the projection portion 25 in this
embodiment) for supporting the front centrifugal force applied to
the portion from the leading edge to the intermediate portion,
further has the concave groove 31 and the faucet portion 37 in this
embodiment, and is provided with the spin cone 30 engaging with the
sub engagement portion 24 so as to be capable of transmitting the
front centrifugal force to the disc 10, it is possible to securely
support the front centrifugal force applied to the portion in which
the hub diameter of the zero hub tip ratio fan is zero or close to
zero via the concave groove 31 and the faucet portion 37 of the
spin cone 30 so as to securely transmit to the disc 10.
[0078] Further, since the rear centrifugal force applied to the
portion from the intermediate portion to the trailing edge is
transmitted to the disc 10 by the main dovetail groove 12 and the
main dovetail portion 22 extending in parallel to the axis of the
rotating shaft, it is possible to make the component force along
the main dovetail groove of the centrifugal force applied to the
zero hub tip ratio fan 20 small, and it is possible to securely
support the component force by the low stress on the basis of the
retainer structure having the same structure as the conventional
one.
[0079] In FIG. 5, the main dovetail portion 22 of the zero hub tip
ratio fan 20 has a vertical rear surface 23 which is orthogonal to
the main dovetail groove 12, in a rearward end thereof.
[0080] Further, the dovetail structure in accordance with the
present invention has a rear retainer 16 fixed to a rear end
surface (a rear edge 10b) of the disc 10 by a coupling bracket (for
example, a bolt and a nut) (not shown).
[0081] The rear retainer 16 is structured such that a front surface
thereof is closely attached to the vertical rear surface 23 so as
to prevent the main dovetail portion 22 from moving backward.
[0082] In accordance with this structure, it is possible to make a
surface pressure of a contact surface of the rear retainer
substantially constant, and it is possible to reduce the internal
stress generated in the rear retainer.
[0083] In this case, the fixing means in the axial direction of the
zero hub tip ratio fan 20 is not limited to the vertical rear
surface 23 and the rear retainer 16 mentioned above, but may employ
the other well-known means singly or together.
[0084] FIG. 7 is a view showing a second embodiment of the dovetail
structure in accordance with the present invention. Further, FIG.
8A is a partly perspective view of a fan front portion, FIG. 8B is
a perspective view along a line B-B in FIG. 7, and FIG. 8C is a
partly cross sectional view along a line C-C in FIG. 7.
[0085] In this embodiment, the sub engagement portion 24 is
constituted by a plurality of slope dovetail portions 27. The slope
dovetail portions 27 extend at a fixed angle .THETA. with respect
to the axis 1 of the rotating shaft from the leading edge to the
intermediate portion of the zero hub tip ratio fan 20, and are
spaced at a fixed angle (for example, 20 degree in this embodiment)
in a peripheral direction.
[0086] The fixed angle .THETA. corresponds to an angle in which a
forward side is close to the axis 1 and a rearward side is away
from the axis 1, and preferably corresponds to an angle along the
inner peripheral surface 3 of the air flow path 2. In this case,
the angle .THETA. is about 40 degree in this embodiment.
[0087] Further, in this embodiment, the spin cone 30 has a
plurality of slope dovetail grooves 32 fitted to the slope dovetail
portions 27, a faucet portion 37 fitted to a cylindrical inner
surface 10c provided in the disc 10, and a faucet portion 38 fitted
to a cylindrical inner surface 10d provided in an outer side of the
disc 10.
[0088] The other structures are the same as those of the first
embodiment.
[0089] In accordance with the structure mentioned above, since the
zero hub tip ratio fan 20 has the sub engagement portion 24 (the
slope dovetail portion 27 in this embodiment) for supporting the
front centrifugal force applied to the portion from the leading
edge to the intermediate portion, further has the slope dovetail
groove 32 and the faucet portions 37 and 38 in this embodiment, and
is provided with the spin cone 30 engaging with the sub engagement
portion 24 so as to be capable of transmitting the front
centrifugal force to the disc 10, it is possible to securely
support the front centrifugal force applied to the portion in which
the hub diameter of the zero hub tip ratio fan is zero or close to
zero via the slope dovetail groove 32 and the faucet portions 37
and 38 of the spine cone 30 so as to be capable of securely
transmitting to the disc 10.
[0090] The other operations and effects are the same as those of
the first embodiment.
[0091] FIG. 9 is a view of a third embodiment of the dovetail
structure in accordance with the present invention. Further, FIG.
10 is a partly perspective view of a fan front portion of FIG.
9.
[0092] In this embodiment, the sub engagement portion 24 is
constituted by a plurality of parallel dovetail portions 28. The
parallel dovetail portions 28 extend in parallel to the axis 1 of
the rotating shaft from the leading edge to the intermediate
portion of the zero hub tip ratio fan 20, and are spaced at a fixed
angle (for example, 20 degree in this embodiment) in the peripheral
direction.
[0093] A centrifugal force (a front centrifugal force) applied to
the parallel dovetail portion 28 corresponds to a centrifugal force
applied to the spiral blade 20b positioned in an outer thereof, and
is smaller in comparison with a centrifugal force of the fan first
stage rotor blade 20a applied to the main dovetail portion 22.
[0094] Accordingly, it is preferable that a size of the parallel
dovetail portion 28 is made sufficiently smaller than a size of the
main dovetail portion 22.
[0095] Further, in this embodiment, the spin cone 30 has a
plurality of parallel dovetail grooves 33 fitted to the parallel
dovetail portion 28, and a faucet portion 37 fitted to a
cylindrical inner surface 10c provided in the disc 10.
[0096] The other structures are the same as those of the first
embodiment.
[0097] In accordance with the structure mentioned above, since the
zero hub tip ratio fan 20 has the sub engagement portion 24 (the
parallel dovetail portion 28 in this embodiment) for supporting the
front centrifugal force applied to the portion from the leading
edge to the intermediate portion, further has the parallel dovetail
groove 33 and the faucet portion 37 in this embodiment, and is
provided with the spin cone 30 engaging with the sub engagement
portion 24 so as to be capable of transmitting the front
centrifugal force to the disc 10, it is possible to securely
support the front centrifugal force applied to the portion in which
the hub diameter of the zero hub tip ratio fan is zero or close to
zero via the parallel dovetail groove 33 and the faucet portion 37
of the spin cone 30 so as to be capable of securely transmitting to
the disc 10.
[0098] The other operations and effects are the same as those of
the first embodiment.
[0099] FIG. 11 is a view of a fourth embodiment of the dovetail
structure in accordance with the present invention, FIG. 12A is a
partly perspective view of the fan front portion, and FIG. 12B is a
partly perspective view of the spin cone.
[0100] In this embodiment, the sub engagement portion 24 is
constituted by a plurality of expanded portions 29. The expanded
portions 29 extend to the intermediate portion from the leading
edge of the zero hub tip ratio fan 20, and are spaced at a fixed
angle (for example, 20 degree in this embodiment) in the peripheral
direction. A width in the peripheral direction of the expanded
portion 29 is preferably formed thicker than a front lower edge of
the fan.
[0101] In this case, "structure in which the width in the
peripheral direction of the expanded portion 29 is formed thicker
than the front lower edge of the fan" is not essential in the case
that the front centrifugal force applied to the intermediate
portion from the leading edge of the zero hub tip ratio fan 20 is
sufficiently low. In other words, it is not essential to employ a
structure in which a thickness is increased and a load is
transmitted.
[0102] Further, in this embodiment, the spin cone 30 has a
plurality of fitting grooves 34 fitted to the front lower edge of
the fan in the upper portion than the expanded portion 29, a faucet
portion 37 fitted to the cylindrical inner surface 10c provided in
the disc 10, and a faucet portion 38 fitted to the cylindrical
inner surface 10d provided in an outer side of the disc 10.
[0103] The other structures are the same as those of the first
embodiment.
[0104] In accordance with the structure mentioned above, since the
zero hub tip ratio fan 20 has the sub engagement portion 24 (the
expanded portion 29 in this embodiment) for supporting the front
centrifugal force applied to the portion from the leading edge to
the intermediate portion, further has the fitting groove 34 and the
faucet portions 37 and 38 in this embodiment, and is provided with
the spin cone 30 engaging with the sub engagement portion 24 so as
to be capable of transmitting the front centrifugal force to the
disc 10, it is possible to securely support the front centrifugal
force applied to the portion in which the hub diameter of the zero
hub tip ratio fan is zero or close to zero via the fitting groove
34 and the faucet portions 37 and 38 of the spin cone 30 so as to
be capable of securely transmitting to the disc 10.
[0105] The other operations and effects are the same as those of
the first embodiment.
[0106] In the fourth embodiment mentioned above, (1) it is possible
to transmit the front centrifugal force applied to the portion in
which the hub diameter of the zero hub tip ratio fan is zero or
close to zero, and the hub/tip ratio is between 0 and 0.35, to the
disc 10 on the basis of the fitting between the main dovetail
portion 22 and the main dovetail groove 12, and (2) it is possible
to make the size of the expanded portion 29 small or substantially
omit the expanded portion 29, as far as the front lower edge of the
fan in the upper portion than the expanded portion 29 and the
fitting groove 34 are fitted so as to suppress the vibration of the
fan.
[0107] In this case, it goes without saying that the present
invention is not limited to the embodiments mentioned above, but
can be variously modified in a range within the scope of the
present invention.
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