U.S. patent application number 11/404136 was filed with the patent office on 2006-10-19 for slotted bladeless turbine disc.
Invention is credited to Robert D. Saunders.
Application Number | 20060233647 11/404136 |
Document ID | / |
Family ID | 37108641 |
Filed Date | 2006-10-19 |
United States Patent
Application |
20060233647 |
Kind Code |
A1 |
Saunders; Robert D. |
October 19, 2006 |
Slotted bladeless turbine disc
Abstract
A slotted bladeless turbine disc stamped or otherwise formed
from a single solid sheet of material with slots formed in the disc
to redirect fluid passing through it is disclosed and illustrated
in FIG. 1 and FIG. 2. The form of the slots is curved, slanted and
aligned at an angle to the plane of the disc and along a radial
from the center of rotation of the disc in such a manner as to
force fluids passing through the disc to change direction. Reaction
forces of the fluid on the many slots in the disc creates a
resultant rotational force on the center of rotation of the disc
and thus on the rotatable shaft to which the disc is rigidly
attached. To form a turbine one or more slotted discs are assembled
on a shaft and enclosed in a case.
Inventors: |
Saunders; Robert D.;
(Woodruff, WI) |
Correspondence
Address: |
ROBERT D. SAUNDERS
P.O. BOX 412
WOODRUFF
WI
54568
US
|
Family ID: |
37108641 |
Appl. No.: |
11/404136 |
Filed: |
April 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60672196 |
Apr 14, 2005 |
|
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Current U.S.
Class: |
416/223A |
Current CPC
Class: |
Y02T 50/671 20130101;
F01D 5/34 20130101; F01D 5/14 20130101; F01D 5/03 20130101; Y02T
50/60 20130101 |
Class at
Publication: |
416/223.00A |
International
Class: |
F01D 5/14 20060101
F01D005/14 |
Claims
1. A turbine disc for rotating machinery, comprising a disk and a
plurality of slots; each slot comprising a shaped hole in the disk
and an adjacent tab formed from the material punched or otherwise
extracted from the hole.
2. A bladeless turbine disc according to claim 1 for use in
rotating mechanisms, whereby blades and blade attachments to a hub
are eliminated from turbine rotor and stator discs, comprising: a
disk of rigid material, a plurality of slots formed within a disk,
generally arranged in a pattern around its center of rotation, each
slot comprising: a hole having a predetermined shape through which
fluid material flows, thereby forming an orifice, a flat or concave
shaped tab, generally being located on one side of the disc, and
oriented along a disk radial, and tilted at an angle to the surface
of the disk, and being adjacent to the hole, thereby providing a
means for deflecting or redirecting fluid material flowing through
the orifice; a centrally located hole cut at the center of rotation
of the disc, thereby providing a means to pass a rotatable shaft of
predetermined cross section through the hole, comprising: a means
to rigidly attach the bladeless disc to the shaft thereby forming a
rotor disc, a means to attach a bearing or bushing between the
bladeless disc and the rotating shaft, thereby forming a stator
disc.
3. A steam turbine engine including a rotor disc according to claim
2.
4. A gas turbine engine including a stator disc according to claim
2.
5. A hydro turbine including a rotor disc according to claim 2.
6. A wind turbine including a rotor disc according to claim 2.
7. A pump including a rotor disc according to claim 2.
8. A fan including a rotor disc according to claim 2.
9. A lifting device or machine including a rotor disc according to
claim 2.
10. A yard ornament including a rotor disc according to claim 2.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
REFERENCE TO SEQUENCE LISTING A TABLE OR A COMPUTER PROGRAM LISTING
COMPACT DISC APPENDIX
[0003] Not applicable
BACKGROUND
[0004] 1. Field of the Invention
[0005] This invention relates to turbine discs used in rotary
mechanisms, such as in steam turbines, gas turbines and jet
engines, hydroelectric plants, and in bladed wind turbines. Slotted
bladeless discs provide less costly rotor and stator discs than
bladed discs or wheels historically used in such turbines. The
slotted disc is fabricated from a single blank disk by stamping and
forging instead of fabricating and assembling a multitude of
individual turbine blades requiring attachments to a central
hub
[0006] 2. Description of Prior Art
[0007] Steam turbines were invented during the late 1800s and early
1900s. One of the first patents for bladed steam turbines is found
in U.S. Pat. No. 639,608, dated Dec. 19, 1899, by Sir Charles A.
Parsons of Newcastle-Upon-Tyne, England and assigned to the
Westinghouse Machine Company of Pittsburgh, Pa. Parsons' first
steam engine patent was issued in 1884. Additional related patents
were issued to C. A. Parsons on Jan. 29, 1924 (U.S. Pat. No.
1,482,031) and on Jun. 14, 1932 (U.S. Pat. No. 1,862,827). Many
other patents have been issued relating to the shape of the blades
and to the attachment of the blades to the hub of the turbine wheel
and thus to the turbine shaft. While many more patents have been
issued to improve the seal between the bladed turbine wheel and the
turbine housing, seals are not within the scope of this
invention.
[0008] There is a longstanding need for relatively inexpensive
steam driven power generators capable of using renewable
sustainable sources of energy. Slotted disc steam turbines are
ideally suited for such machines. Wood and other bio-mass burning
stoves and boilers are commonly used to generate steam. Other
suitable sources of energy include but are not limited to solar
energy, geothermal energy and energy from flammable oils, gases and
chemicals. There is a further need for small distributed electrical
power generating units in remote areas where power distribution
lines do not exist. Mainly there is a need for an inexpensive steam
or gas turbine to satisfy these requirements. Although small steam
and gas turbines do exist, the widespread use of these machines has
been greatly prohibited by the cost of bladed turbine discs. My
invention will enable the building of small inexpensive power
plants to satisfy these needs using stamped, welded and widely
available off-the-shelf parts. This invention is not limited to
energy derived from steam or gas but can also be applied to
hydroelectric power plants, where energy is derived from flowing
water or other incompressible fluids, and to wind driven turbine
generators.
[0009] Nearly all steam and gas turbines use a bladed turbine disc
or wheel constructed of individual flat or twisted blades mounted
radially on a hub to form a wheel or disc arrangement. The purpose
of the bladed turbine wheel is to transform energy contained in
high-pressure steam or other fluid media flowing through the blades
into rotational energy. Steam does this by harnessing the energy
released when gas under pressure flows from a higher temperature
and pressure through a turbine stage, wheel or set of wheels to a
lower temperature and pressure. High-pressure steam is allowed to
expand, resulting in an acceleration of the axial flow of material
through the turbine blades. When the high pressure is on one side
of the turbine blades and the low pressure is on the opposite side
of the turbine blades the flow of steam attains a relatively high
rate of speed through the flat, twisted or curved turbine blades.
As the material passes through the turbine blades, the direction of
the fluid is changed and the resulting reaction creates an equal
and opposite force on the turbine blades and thus a torque on the
hub and shaft of the rotating wheel.
[0010] Structure of the turbine. In a 1911 speech Parsons said:
[0011] "that steam behaves almost like an incompressible fluid in
each turbine of the series, but because of its elasticity its
volume gradually increases with the succession of small falls of
pressure, and the succeeding turbines consequently are made larger
and larger. This enlargement is secured in three ways: [0012] 1. By
increasing the height of each blade. [0013] 2. By increasing the
diameter of the succeeding drums [0014] 3. By altering the angles
and openings between the blades."
[0015] Turbine blades are generally made of high temperature
hardened steel or other alloy capable of withstanding heat and
centrifugal forces associated with high speed rotating machinery.
Failures in turbine blades can be catastrophic. If one blade fails
the resulting imbalance causes the whole machine to become
unbalanced and must be shut down to avoid more serious damage. In
more serious failures, a blade breaking at high speed results in
other blades being shattered as well as the casing containing the
high-pressure steam or gas. This condition sometimes results in
catastrophic explosions.
[0016] The slotted disc [0017] a. eliminates increasing the height
of each blade by allowing the length and width of the slots to be
increased in each succeeding disc without [0018] b. increasing the
diameter of each succeeding disc, and [0019] c. replaces the angle
and openings of the slots by altering the angle of the tabs and the
size of the apertures in the slots.
SUMMARY OF THE INVENTION
[0020] A longstanding need has existed for a simpler, less
expensive and easier to fabricate turbine disc, especially for use
in rotating mechanism applications. My invention operates using the
same properties of steam and hot gases that the well-known bladed
turbine discs or wheels use in steam and gas turbines. Unlike
bladed turbine wheels, the slotted turbine disc can be stamped from
a single piece of material. The slotted disc comprises a disk with
a multitude of slots through which steam, gas or other fluid passes
at high speed, and through which the direction and speed of the
moving media is changed as it passes through the plane of the disc.
The action of the change in speed and direction through the slots
causes a force to be imposed upon the slot tabs according to the
law of action and reaction resulting in a rotational force or
torque upon a rotor disc and therefore upon the shaft to which the
disc is rigidly attached.
[0021] The slotted disc is fabricated from a flat circular steel
plate, or disk, by forming slots in the plate through which, in the
preferred embodiment, steam is allowed to pass; each slot
comprising a dimensioned hole, also called an aperture or orifice,
plus an associated shaped tab. The shape of the slot is important
and is formed by pressing, hammering, forging, casting or otherwise
creating an open orifice or passageway through which steam or other
fluid passes, and in the same operation forming the associated tab
comprising the same material that was forced out of the plate to
form the orifice. The direction of the flow of steam or fluid
changes as it passes through a slot. As it passes through a slot
from a higher pressure side to a lower pressure side, steam
velocity increases, while the temperature and pressure drop, and
some of the energy is imparted to the slanted or curved portion of
the tab, according to the law of action and reaction. When the disc
is connected to a rotating shaft, the force vector applied to the
slanted portion of the slot's tab imposes a rotational force, or
torque, upon the disc and therefore on the shaft to which it is
attached.
[0022] A slotted disc illustrated in FIG. 1 is formed when a
multitude of slots are cut and shaped in the disc. Each slot has an
associated tab as shown in FIG. 1. When operating, each slot
through which steam passes adds a rotational element of force to
the rotatable disc. When the disc is turning the integration of the
forces from all of the slots combine to create a resultant
rotational force or torque on the disc. If the resultant torque is
sufficient it causes the shaft, to which the rotor disc is rigidly
attached, to rotate. In the preferred embodiment the slots in the
disc are arranged in a pattern similar to that illustrated in FIG.
1. In the preferred embodiment the length and width of all the
slots, and thus the tabs, in the disc are similar. To maximize the
resultant torque, all the slots are oriented so that the reaction
for each slot is additive. The force on each tab has a component
vector, perpendicular to a radial line emanating from the center of
the disc, and parallel to its surface. Each tab faces in the
direction necessary to add to the sum of the rotational forces
created by the steam passing through its slot.
[0023] The tabs on the downstream side of each slot act in a manner
similar to the blades in a bladed turbine. Turbine blades or vanes
are alternatively known as buckets. The tabs associated with the
slotted disc are functionally similar to the blades in a bladed
turbine wheel and hereafter may also be referred to as buckets.
Altering the opening of the slots and the shape and angle of the
tabs in the slotted disc is equivalent to altering the angle and
openings between the blades of a bladed disc. The length of each
slot in a slotted disc roughly corresponds to the length of each
blade in a bladed wheel, therefore the diameter of the discs do not
have to be increased for subsequent turbine stages. Instead of
increasing the diameter of the disc, it is only necessary to vary
the length and the width of the slots in subsequent stages of the
turbine assembly as illustrated in FIG. 3. The importance of this
is that a complete turbine assembly can be built inside a
cylindrical housing instead of the conventional conical shaped
bladed turbine housing. However, if necessary the diameter of
slotted discs can be increased to fit existing conical turbine
rotor casings.
[0024] The same general materials used to fabricate a bladed wheel
are used to fabricate a slotted disc, thus maintaining similar
thermal and mechanical characteristics of the materials. Seals are
attached to turbine discs to reduce leakage between stages. Seals
and stuffing boxes as used in turbines are not within the scope of
this invention.
[0025] With compressible fluids the slots in each consecutive disc
increase in size and shape to compensate for the expected drop in
temperature and pressure of the fluid through the assembly, as
illustrated in FIG. 3. With incompressible fluids the slots are
generally of constant size. Furthermore, the same slotted disc
design is used for stator discs or nozzles in a turbine assembly,
although the design of a stator disc is basically a mirror image of
the rotor disc and the stator disc is rigidly attached to the case.
The purpose of a stator disc, also referred to as a nozzle disc, is
to redirect the flow of material toward a generally axial direction
through the turbine assembly. Embodiments of this invention enable
the construction of steam, gas and hydro turbines using welding and
stamping operations in place of machining operations so as to
greatly reduce the cost of fabricating turbines as compared to the
cost of fabricating turbines that incorporate bladed wheel
assemblies.
[0026] Accordingly, several objects and advantages of my invention
are as follows.
[0027] An object of my invention is to provide turbine rotor and
stator discs for a rotary mechanism, comprising one or a multitude
of slotted discs. The rotor disc is the working part of a turbine
that converts some of the energy in moving water, steam or gas into
mechanical energy, expressed as torque and velocity of a rotating
shaft.
[0028] An advantage of my invention is the simplicity of
manufacturing a turbine disc with a single stamping operation
rather than with an expensive bladed disc made from many machined
blades requiring complicated blade-to-hub attachments.
[0029] It is also an object of my invention to provide simple
methods for attaching a slotted bladeless disc to a shaft, such as
by welding or by other means generally well known to persons versed
in the art and engineering of rotating machinery.
[0030] A further advantage of the slotted disc is that it has
mechanical strength where the bladed turbine is weak, namely in the
blades themselves and in their attachment to the hub and thus the
attachment to the shaft.
[0031] Furthermore, the slotted disc can be fabricated from much
thicker material than common turbine blades, thus providing more
strength and more weight to a single turbine stage whereby the
added weight tends to act as a flywheel, which tends to reduce
certain vibrations unavoidable or difficult to control with thinner
lighter material.
[0032] Another advantage is that the cost of manufacturing the
slotted disc is much less than the cost of machining and
fabricating the multi bladed disc. Blades and other parts in bladed
turbine wheels must be separately machined. A slotted disc is
stamped out of appropriate material in a single stamping operation,
thus eliminating many steps in the manufacturing process.
[0033] Another advantage is a more uniform distribution of
temperature across the surface of the bucket than that of a blade
in a bladed turbine. This results in less thermodynamic stress
across the surface of the bucket in the slotted disc.
[0034] Another advantage is reduced testing and balancing
requirements of the assembled wheel.
[0035] A further advantage is the smooth surface of the bucket in
the slotted disc upon which the moving material impinges compared
to the sharp edge of the blade in a bladed turbine wheel. In a
bladed turbine, the edges of the blades are worn down by the impact
and eroded by the material moving through the circular array of
blades. The path of the moving material through the slots in a
slotted disc does not encounter sharp edges and the disc is subject
to much less erosion from the moving media.
[0036] A disadvantage of the slotted disc is that it can not
accommodate as many buckets of the same size and the same width as
a bladed wheel. A rotor and a stator, if a rotor is used, comprise
a single stage. However, an increase in the number of slotted disc
stages can be added to compensate for the difference.
[0037] Further objects and advantages of my invention will become
apparent from a consideration of the drawings and ensuing
description.
[0038] Preferred and Other Embodiments. The preferred embodiment of
this invention comprises a disc with a multitude of evenly spaced
slots surrounding a center hole through which a rotatable shaft is
inserted; for use in steam turbines and other rotating mechanisms.
The cost advantage of stamping out turbine discs over the cost of
present methods of fabricating bladed turbine wheels means that
stamped discs can be used to build relatively inexpensive turbines.
Conversely, the high cost of fabricating bladed wheels means they
can only be used in relatively high-powered expensive turbines.
Using my invention small steam turbines can be fabricated primarily
with stamped and welded parts that require a minimum of machining
operations compared to the bladed turbine. The ability to obtain
small inexpensive turbines suggests that such turbines connected to
suitable electric generators may be used to power households and
other facilities where electric power is not presently available or
where it is cheaper to produce electricity than to purchase it. It
is suggested that such small turbines can be adapted to power
vehicles by using direct drives or by using the output to drive a
generator and an electric motor or a combination of both.
[0039] Another embodiment of this invention is for use in
low-pressure steam turbines. Bladed steam turbines are generally
used with high pressure and high temperature steam where high power
electrical generation is required, such as in electric power
plants. The cost advantage of fabricating and operating a small
steam turbine using slotted turbine discs suggests that such
distributed power sources can be installed in remote places where
power lines from central power plants are not available.
[0040] Another embodiment of this invention is for use as an
impeller in a compressor or pump.
[0041] Another embodiment of this invention is for use as a rotor
in a hydroelectric plant turbine where hydro turbines are used to
turn generators.
[0042] Another embodiment of this invention is for use in a wind
turbine.
[0043] Another embodiment of this invention is for use as a toy,
similar to a pinwheel.
[0044] Another embodiment of this invention is for use as a lawn
and garden ornament, commonly known as a whirligig.
[0045] Another embodiment of this invention is for use as a rotor
for a helicopter or other lifting machine.
[0046] A further embodiment of this invention is for use as a fan
to move air in the same manner as any bladed fan.
[0047] In the preferred embodiment the shape of the slot is oblong
or eye-shaped, but it could be round, square or triangular or have
other geometrical shapes. In the preferred method, one side of the
slot, or bucket protrudes from the rear or downstream surface of
the flat plate, away from the direction of the flow of steam
through the slot. It is possible for the other side of the slot to
protrude toward the front of the disc in such a way as to open the
pocket to allow more steam to pass through it. Control of the
amount of steam passing through the slots is attained by varying
the size and shape of the openings in the slots and by controlling
the temperature, pressure and volume of the supply steam.
[0048] A complete turbine can have a single disc, forming a single
stage turbine, or a multitude of discs, forming a multi-stage
turbine. An important difference between a conventional bladed
turbine and a slotted disc turbine, is that all the slotted discs
can be made with the same outer diameter. The first stage has
smaller slots than the last stage and each intermediate disc in the
turbine has sequentially larger slots. This allows more steam to
pass through each successive disc in a way that is similar to the
flow of steam through a conventional bladed turbine, without the
need to have each disc increase in diameter.
[0049] The shape of the slots in the disc can be varied to
accommodate a wide range of requirements to control the flow of
steam. A narrower slot will generally result in less steam passing
through but at a higher speed than that of a wider slot. A wider
slot will allow more steam to pass through at a slower speed. The
length of the slot can also be varied to control the amount of
steam passing through it. The longer the slot, the more steam will
pass through it. It is noted here that if the slot is too wide or
too long, steam can pass through the slot without changing
direction. If this occurs some rotational forces on the disc are
lost and the efficiency of the turbine is reduced.
[0050] The tab in the back of the slot, or lower pressure side of
the disc, can be varied in shape and angle from the plane of the
disc to control the direction of the steam leaving the tab. The
angle of the tab relative to the plane of the disc must always be
an acute angle of less than ninety degrees. The shape and position
of the tab can vary along the radial of the disc on which it
resides in such a manner as to emulate the bent shape of a turbine
blade. The strength of the tab can be increased by adding more
material to the back of the tab by welding or by other fabrication
methods well known to those skilled in the arts of sheet metal
fabrication. Tabs can be fabricated separately from the disc and
attached to the back of the disc by any means known to those
skilled in the art. The preferred embodiment is to fabricate the
tabs as part of the original round plate by means of first cutting
slits in the disk and then pressing the tab in such a way that it
does not tear or otherwise significantly weaken the plate. After
forming the slots, the entire disc can be heat treated as is
commonly done for bladed turbines.
[0051] Two types of solid plates can be used in the fabrication of
the bladeless disc, either thin plates or thick plates. Other types
of plates can be fabricated from laminated, sandwiched or honeycomb
materials. The description above is related to the fabrication of
bladeless discs made from thin plates. Thick plates can also be
used as described above, or the slots can be formed in a thick
plate without the need for a tab, or with the use of a smaller tab.
If the slot in the thick plate is cut along a radial of the disc,
but the direction of the slot is other than perpendicular to the
plane of the disc, then the direction of the flow of steam through
the plate will be altered in such a manner as to result in a
component force vector perpendicular to the radial and along the
plane of the disc. Redirecting the steam in this manner is the same
as redirecting the steam using the tabs on the back of the thin
plate. One reason for using a thick or honeycombed plate rather
than a thin plate is to increase the strength of the disc, which
allows higher steam pressure and greater flow of material through
the slots. For high-pressure turbines, the edges of the slot can be
processed and shaped to further reduce wear and erosion. The same
processes used to increase the strength of blades in a bladed
turbine can be used to strengthen the slots in a bladeless disc.
Tabs can be added to the back of the thick plate or honeycombed
disc to enhance the redirection of the steam flowing through the
disc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] The embodiments of the invention illustrated in the
following drawings are disclosed in greater detail in the
Description:
[0053] FIG. 1 illustrates a basic 16-slot slotted turbine disc.
[0054] FIG. 2 illustrates a 16-slot turbine disc comprising longer
slots and shaped tabs.
[0055] FIG. 3 illustrates part of a turbine assembly comprising two
rotor discs and one stator disc.
[0056] FIG. 4 illustrates a 32-slot turbine disc comprising
reinforcing rings and a means for rigidly attaching the disc to a
rotatable shaft.
[0057] FIG. 5 illustrates a pattern of lines useful as a teaching
aid for manually laying out a template for a multitude of slots
along disk radials, as explained in the description.
[0058] FIG. 6 illustrates a preferred embodiment of a steam turbine
comprising slotted rotor and slotted stator discs.
[0059] FIG. 6b illustrates an embodiment of a steam turbine
comprising only slotted rotor discs.
[0060] FIG. 7 illustrates a basic prior art bladed turbine disc or
wheel.
[0061] FIG. 8 illustrates a cylindrical slotted disc turbine
comprising a long and narrow aspect ratio.
DESCRIPTION
[0062] FIG. 1 illustrates a bladeless slotted turbine disc
comprised of a flat round disk [110] containing slots [120] with
tabs or buckets [130] formed on the back, low pressure or
downstream side of the disc. To fabricate a slotted disc, the disc
is formed from a single round blank disk of sheet metal, metal
plate or other suitable material. The disk [110] must be strong
enough to withstand centrifugal forces plus the heat and mechanical
stresses associated with steam, gas or other fluid dynamics. As the
metal is bent along one side of a slit, a hole, aperture or orifice
is formed [120]. Whereby, the tab [130] is formed from the same
operation. Therefore a slot comprises both the orifice [120] and
the tab [130]. A hole [140] is provided at the center of rotation
of the disc for the passage of a shaft through the disc.
[0063] Preferably the slots in the disc are geometrically located
along radials and equally spaced to assure a balanced disc. FIG. 5
illustrates one approach to manually creating a slot pattern on a
blank disk. Other methods include the use of computer generated
patterns created on Computer Aided Design, or CAD systems or by use
of numerically controlled drilling and machining equipment.
[0064] As illustrated in FIG. 5, narrow slits [20'] are cut in the
metal using a milling or routing machine, saw, grinder, laser,
torch or other device commonly used in metal cutting operations. In
the preferred embodiment, the slit [20'] is cut in a straight line
along a radial [12'] and the tab is formed by extending the metal
on one side of the slit. This is accomplished by hammering,
bending, pressing or by other similar forming operations. Other
methods include forging, stamping or casting the entire disc. Tabs
can also be formed by adding shaped or formed material to the back
of the disc and by welding, brazing or by other suitable methods
known to those skilled in the metal working arts.
[0065] The shape and thickness of the slots vary depending on the
strength and stiffness required for disc operation under thermal
and mechanical stresses encountered in operation of the turbine. In
FIG. 2 the shape of the slot [210] can be formed so that the center
of pressure on an individual bucket is moved toward the outer
circumference of the disc, thus producing more torque on the
rotating shaft. The curvature of a bucket [210] can be designed to
emulate the action of a blade in a prior art bladed disc as
depicted in FIG. 7. A hole [230] is provided at the center of
rotation of the disc for the passage of a shaft through the
disc.
[0066] FIG. 3 illustrates a cut-a-way view of a portion of a
turbine comprising a multitude of rotor and stator discs. FIG. 3
shows an assembly of one stationary disc [320] or nozzle, welded to
the frame or casing [310] of the assembly and two rotating discs
[110] [200] mounted on a rotatable shaft [328]. A weldment [324]
rigidly connecting the stationary disc [320] to the inner surface
of the case [310] is shown as a continuous bead [324] around the
circumference or outer edge of the stationary disk [320]. The
primary purpose of the stationary disc is to redirect the flow of
material [342] through the slots to establish a generally axial
flow of material through the entire turbine.
[0067] In FIG. 3 it can be seen that the size of the slots are
smaller toward the high-pressure lower stage of the turbine [130]
and gradually increases for each additional rotating disc [210].
The largest slots are found in the last stage of the turbine. In
FIG. 3 arrows [330] indicate the direction of rotation of the
rotating discs. The different direction of the flow of material
through the slots in the assembly is indicated by arrows [340],
[342] and [344].
[0068] It is noted that the increase in the size of the slots from
the first through the last stages in a slotted disc turbine
emulates the increase in the length of the turbine blades in a
bladed turbine without requiring a conical shaped casing.
[0069] It can further be seen that the direction of the flow of
steam, in the case of a steam turbine, through the disc slots
changes as the steam passes through each disc. The purpose of the
slots and buckets in the stationary disc [320] is to redirect the
flow of material in such a manner as to increase the force of the
impinging fluid on the buckets of the next rotating disc [200]. As
the steam or fluid moves through a bucket in the rotating disc, it
changes direction resulting in a reaction that produces a component
of a force vector in a direction parallel to the plane of the disc
and perpendicular to a radial, thereby producing torque on the
rotating shaft. The sum of all the torque components from all the
buckets in all the rotating discs in the complete turbine assembly
equals the total torque on the rotatable shaft.
[0070] In FIG. 3 it can further be seen that each rotor disc [110]
[200] is rigidly attached to the rotatable shaft [328] by means of
a weldment [336] comprised of a continuous welded bead between the
disc and the shaft. The rotatable shaft [328] is isolated from the
stator disc [320] by a bearing surface or a seal not shown in FIG.
3. Bearings and seals are not within the scope of this
invention.
[0071] FIG. 4 illustrates a 32-slot disc [400] mounted on a shaft
[450]. The disc has reinforcing hub rings [430] [460] attached to
the outer and inner portions of its area. The outer ring [430] is
designed to stiffen the disc while in operation and thus provide
more strength to reduce bending and vibration of the disc due to
dynamic forces resulting from the pressure differential and
velocity of the material flowing through the slots and the rotation
of the disc. The outer ring [430] is attached to the disc [400] by
welding, spot welding, riveting or by other suitable methods. A
similar outer ring is sometimes attached to the opposite side of
the disc for the same purpose and by the same method. The second
outer ring provides more strength if needed.
[0072] The inner ring [460] may be attached to the disc in the same
manner as the outer ring. The primary purpose of the inner ring is
to strengthen the area of the disc where large forces may build up
around the center portion of the disc in the area of the shaft
attachment [450]. The inner hub ring may also be used as a means of
spacing the adjacent discs and to provide a means of attaching the
disc to the shaft. In FIG. 4 the disc [400] is attached to the
shaft [450] by means of a slot and key [470] arrangement. Small
holes [410] are drilled through the disc at the ends of the slots
[420] to mark the ends of the aforementioned slits and to reduce
stresses normally experienced under operating conditions. The
direction of rotation [440] of the disc is determined by the
direction of the material through the slots and the configuration
of the tabs. In this illustration the direction of the steam is out
of the plane of the paper and the tabs [420] are bent outward from
the plane of the paper, toward the reader.
[0073] Designing a slotted disc or template. In accordance with the
spirit of complete disclosure, the following detailed step-by-step
method of creating a slot pattern is hereby included in this
description. A single template illustrated in FIG. 5 can be used to
lay out a whole set of discs with similar slot patterns. This
method of creating a slot pattern template can be used to layout
2-, 4-, 8- and 16-slot discs, and more One method of creating a
template is described below. In a 16-slot template the angle
between the slots is 22.5 degrees. It was created by simple
geometry with the use of a straight edge and a drafting compass. If
a CAD system is available, other patterns can easily be created,
e.g., the angle between the slots in an 18-slot disc is 20 degrees.
It is suggested that a stable base material be used for the
template, such as a sheet of drafting mylar, a thin sheet of tin or
copper or a like material.
[0074] Suggested tools are as follows: [0075] 1. Steel straight
edge. [0076] 2. Center punch. [0077] 3. Drafting compass [0078] 4.
Steel scribe. [0079] 5. Ball peen hammer. [0080] 6. Sharp
instrument to mark the template material. [0081] 7. Sharp
instrument to cut slots through the template material; for example,
a dremel tool or drill with a cut-off wheel is a very convenient
tool for this purpose. [0082] 8. Blunt rod or dull tool such as a
punch or nail setter to form the tabs in the slot. [0083] 9. *A
press such as an arbor press can be used to form the tabs. [0084]
10. *A tool and die if a mechanical press is used. * Optional but
not necessary.
[0085] FIG. 6 Illustrates a pattern layout for a slotted disc. The
following steps are offered to create the pattern: [0086] 1. Draw a
circle the same size as the round blank disc. [0087] 2. Locate the
center of the circle. [0088] 3. Mark the center of the disc,
preferably with an indentation. [0089] 4. Draw a concentric circle
inside the circle. [0090] 5. Draw a vertical line [1'] through the
center. [0091] 6. Draw a horizontal line [2'] through the center.
[0092] 7. Draw horizontal lines [3'] and [4'] tangent to the inner
circle. [0093] 8. Draw vertical lines [5'] and [6'] tangent to the
inner circle. [0094] 9. Draw a 45-degree line [7'] through the
intersection of lines [3'] and [5'] and lines [4'] and [6']. This
should intersect the center point of the circles. [0095] 10. Draw a
45 degree line [8'] through the intersection of lines [4'] and [5']
and lines [3'] and [6']. This should intersect the center point of
the circle. [0096] 11. Draw a circle [1'] tangent to lines [1'] and
[7']. [0097] 12. Draw a line [12'] through the center of the circle
[16'] and through the center of the disc. This line will bisect the
angle between lines [1'] and [7']. [0098] 13. Repeat steps 11 and
12 for lines [13'], [14'] and [15']. [0099] 14. Draw a concentric
circle [9'] at a distance A from the inner circle. [0100] 15. Draw
a concentric circle [10'] at a distance B from circle [9']. [0101]
16. Mark each intersection indicated with a +with a small dent.
[0102] 17. A small hole is drilled at the location of each +mark to
aid in keeping the slots uniform in length. The holes should be at
least at least as large in diameter as the width of the following
slits. [0103] 18. Cut sixteen narrow slits along each radial
between the +marks. A steel straight edge should be used as a guide
when cutting the slits. [0104] 19. The finished templates are used
to mark the blank disks in a set of disks before cutting the final
discs. [0105] 20. Save the template. [0106] 21. Note: A 32-slot
pattern is made from the 16-slot pattern by drawing another circle
(17) tangent to any two 16-slot radials and marking the center of
that circle (18). Repeat this step to add 7 more evenly spaced
lines. Draw straight lines through the center of the new circles
and through the center of the disc. Repeat steps 16 through 20.
Forming a disc. After the slits have been cut, the process of
forming the tabs for the slots is a simple bending and forming
process. This step can be performed by anyone skilled in the art of
fabricating sheet metal using a press, a tool and die or simply a
hammer and a blunt punch.
[0107] FIG. 6 illustrates an example of a turbine assembly
embodiment comprising steam input pipes [810] [812] and nozzles
[842] [843] directing steam jets onto the first rotor [110] of four
turbine stages. The four turbine stages comprise four slotted
rotator discs [110] [200] [892] [896] and three slotted stator
discs [320] [890] [894]. As illustrated, the length of the slots in
each stage increases as the stages progress. The slots in the first
stage rotor [110] are smaller than the slots in the second stage
stator [320] and second stage rotor [200]. In the preferred
embodiment stator discs [320] [890] and [894] are welded to the
cylindrical frame [310] with a continuous weld, or are otherwise
rigidly attached. Rotor discs are rigidly attached to the rotatable
shaft [328] by securing aforementioned hub rings [480] to the
rotatable shaft [328].
[0108] Endcaps or endplates [882] and [884] are attached to the
ends of the cylindrical casing [310] to provide a means of holding
the entire rotor assembly in place during operation of the turbine.
The shaft is precisely located by positioning end bearing
assemblies comprising bearings or bushings [862] and [872], washers
[860] and [870], seals [864] and [874], and retaining nuts [866]
and [876]. The bearing assemblies are inserted within spaces
provided in the endcaps and secured to the shaft [328] by the
threaded retaining nuts [866] and 867].
[0109] In this illustrated preferred embodiment of a small slotted
disc steam turbine, steam enters the assembly through the input
ports [810] [812] and passes through a multitude of nozzles [842]
[843] which increase the velocity of the steam. As steam passes
through the slots in the multitude of turbine stages, torque is
applied to the rotatable shaft as previously described. While there
are many ways to transfer mechanical energy from a rotating shaft,
one of the easiest means is by use of a belt and pulley system,
whereby a belt pulley [850] is attached to the shaft as illustrated
in FIG. 6.
[0110] A multitude of exhaust ports are arranged as a means of
removing exhaust materials from the turbine casing. Two such ports
[820] and [822] are illustrated in FIG. 6.
[0111] FIG. 6b illustrates a turbine without stationary nozzle
discs. This embodiment includes several stages of rotating slotted
discs. The first slotted disc [803] has small slots and the last
disc [896] has the largest slots. The discs in between have slots
that gradually increase in direct proportion to their distance from
the first disc. The intent here is to increase the active area of
the disc or the slots so as to compensate for the reduction in
pressure as a compressible fluid passes from one stage to the next.
For a multi-stage turbine, the slots in each successive disc
increase in proportion to the number of stages. In a ten-stage
turbine, the smallest slots in the first disc are approximately one
tenth the size of the slots in the largest disc and the size of
each successive disc increases by one tenth the size of the largest
slots in the final stage. This gradation in slot size allows a
similar force on each disc to be realized from the steam as it
passes through the disc, since the pressure of the steam drops as
it passes through each disc. In FIG. 6b the position of each slot
is shown as centered on a radius of the disc. This allows for a
more even expansion of steam as it passes through the stages of the
turbine. Positioning of the slots is not a requirement of this
invention and is merely shown as a preferred embodiment for the
turbine with only rotating slotted discs.
[0112] In the case of incompressible fluids, it is not necessary to
vary the size of the slots.
[0113] In FIG. 6b a flywheel 855] is mounted on the rotatable
shaft. This embodiment can be utilized on any turbine and is not a
feature of this invention. The principal purpose of adding a
flywheel is to allow pulsed operation of the turbine. There is an
advantage to allowing steam to enter from the supply nozzles only
when buckets are directly in front of the nozzle. The flywheel thus
tends to reduce variations in shaft speed, and thus vibration, due
to the intermittent application of the steam.
[0114] FIG. 7 illustrates a typical prior art bladed turbine disc
or wheel comprising a multitude of individual turbine blades [10],
a casing [20], a seal and ring area [30] located around the outer
diameter of the blade array, a hub and attachment area [40] at the
root of the blades and a rotatable shaft [50] to which the bladed
wheel is rigidly attached.
[0115] FIG. 8 illustrates a simple turbine with a large length to
diameter ratio. This is a simple embodiment of a slotted disc
turbine illustrating a disc rotor comprising slotted discs [1100],
a rotatable shaft [1130] and a casing [1120], shown split for
clarity.
[0116] An advantage of this arrangement is that it can be made to
fit in irregular or narrow spaces where needed and where suitable
steam, gas or other liquid is already available.
[0117] Another advantage is that the more stages a turbine has, the
slower it runs. However, there is an inherent theoretical limit to
achievable efficiency, called the Betz limit of approximately 59%
for bladed turbines, which also applies to slotted disc
turbines.
[0118] Another advantage related to the lower speed is the
reduction of high-speed gears required in the power train of the
bladed turbine. Lower gear ratios result in less expensive gearing
in the power train.
* * * * *