U.S. patent number 3,664,001 [Application Number 05/044,263] was granted by the patent office on 1972-05-23 for method of changing capacity of fluid reaction device.
This patent grant is currently assigned to Carrier Corporation. Invention is credited to Karol Pilarczyk.
United States Patent |
3,664,001 |
Pilarczyk |
May 23, 1972 |
METHOD OF CHANGING CAPACITY OF FLUID REACTION DEVICE
Abstract
The capacity of a centrifugal compressor having an overhung
rotor with a plurality of separate stage impellers is changed by
machining the free curved edge of each impeller blade by an equal
amount for each impeller along the entire curved edge length from
the radially extending axial flow edge to the axially extending
radial flow edge. Additional separate shrouds are provided that
differ in diameter from the shrouds supplied with the impellers
before machining by an amount equal to the diametric change
occurring during machining. Further, separate annular diffusers are
provided, with each diffuser having integral blades with free
terminal edges lying in a common plane perpendicular to the axis of
rotation and engaging the adjacent shroud, so that these radially
extending diffuser blade edges may be machined by an amount equal
to the axial component of machining on the corresponding impeller
blades.
Inventors: |
Pilarczyk; Karol (Loudonville,
NY) |
Assignee: |
Carrier Corporation (Syracuse,
NY)
|
Family
ID: |
21931394 |
Appl.
No.: |
05/044,263 |
Filed: |
June 8, 1970 |
Current U.S.
Class: |
29/888.021;
29/888.025; 415/214.1; 415/179; 415/199.1; 415/912 |
Current CPC
Class: |
F04D
29/4206 (20130101); F05B 2230/601 (20130101); Y10T
29/49238 (20150115); Y10T 29/49245 (20150115); Y10S
415/912 (20130101) |
Current International
Class: |
F04D
29/42 (20060101); B23p 015/00 () |
Field of
Search: |
;29/156.4R,156.8R
;415/DIG.3,199,213 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
25,391 |
|
May 1906 |
|
GB |
|
578,473 |
|
Jun 1959 |
|
CA |
|
613,892 |
|
Dec 1948 |
|
GB |
|
785,419 |
|
Oct 1957 |
|
GB |
|
991,406 |
|
May 1965 |
|
GB |
|
Primary Examiner: Campbell; John F.
Assistant Examiner: DiPalma; Victor A.
Claims
What is claimed is:
1. A method of changing the capacity of a fluid reaction device
having a fluid reaction wheel provided with a plurality of blades
peripherally arranged on a hub, with each blade having an axially
extending radial flow edge, a radially extending axial flow edge, a
root portion extending between said edges and a connecting outer
free edge extending between the axial flow and radial flow edges,
and a stationary shroud having an annular surface substantially
corresponding to and closely adjacent the connecting edges of the
blades, including the steps of: providing a second shroud having an
annular surface corresponding in shape to the connecting edges of
the blades and having diameters correspondingly less than the
diameters of the connecting edges; and machining the entire
connecting edge of each blade by an amount for operative reception
within the second shroud to produce a reduced flow capacity upon
relative rotation.
2. The method of claim 1 including providing an annular stationary
diffuser separate from the shrouds and provided with integral
diffuser blades having free radially extending edges, with all of
the edges lying in a common radial plane; and machining the free
radially extending edge of each diffuser blade by an amount that
will produce a corresponding diffuser capacity change.
3. The method of claim 2, including providing structural means
separate from the shrouds and diffuser to form an annular chamber
in direct fluid communication with the space between diffuser
blades and further providing a cylindrical casing separately
receiving therein said diffuser, the shrouds and the means forming
the chamber.
4. The method of claim 1 wherein each of said steps is repeated on
other fluid reaction wheels mounted on a common rotor to constitute
separate fluid reaction stages.
5. The method of claim 1 wherein each blade has its axial and
radial edges peripherally offset to correspondingly twist its
curved edge.
6. The method of claim 1 wherein the fluid reaction device is a
multi-stage compressor having an overhung rotor.
Description
BACKGROUND OF THE INVENTION
Fluid reaction and pumping machinery, for example turbines and
compressors, are required for many different predictable loads so
that one capacity machine cannot be efficiently manufactured for
all situations. Thus, the usual practice is to produce several
lines of machines to be matched fairly efficiently with the various
expected capacities over a given range. However, this considerably
increases the cost of each machine due to the number of different
parts that must be manufactured and the inventories involved, as
well as considerably reducing the flexibility of the machine after
it has once been purchased and installed.
Although many attempts have been made to standardize certain parts
of the machines so that only some of the parts need changing for a
change of capacity, these attempts still involve considerable
expense and relatively high inventories without satisfactorily
maintaining efficiency for each capacity. In the Canadian Pat. No.
578,473, to Buchi, issued June 30, 1959, the capacity of a
three-stage centrifugal compressor is changed by picking
corresponding internal parts without changing the external physical
features of the compressor. This patent still involves the
manufacture and inventory of a plurality of compressor rotors,
which in a multi-stage device are quite expensive, particularly
with high speed operation wherein the rotor must be precisely
balanced and exceptionally strong materials must be used due to the
abrasive affects that increase rapidly with speed. Thus, one of the
most expensive components needs to be replaced according to this
patent. A similar interchange of rotors is taught by the British
Pat. No. 785,419, issued Oct. 30, 1957.
While the machining of the radially extending axial flow edges of
an open type impeller to change its capacity is taught by the
British Pat. No. 613,892, issued Dec. 3, 1958, such machining will
considerably reduce the efficiency of the total device,
particularly with respect to blades that are peripherally twisted
from their axially extending edges to their radially extending
edges. Further, if the same diffusers are employed, their
efficiency will be greatly reduced when the capacity is changed by
machining only the rotor.
CROSS REFERENCE TO RELATED APPLICATIONS
The features of the invention of this application may be used in
combination with the features of the inventions in applicant's
following related applications of the same filing date and assignee
as the present application, the disclosures of which are
incorporated herein in their entirety by reference: "Compressor
Barrel Assembly", Ser. No. 44,446; "Compressor Power Recovery",
Ser. No. 44,463; "Interchangeable Compressor Drive", Ser. No.
44,403 now abandoned; "Compressor Base and Intercoolers", Ser. No.
44,034.
SUMMARY
It is an object of the present invention to overcome the
disadvantages of the prior art as mentioned above, particularly
with respect to a high speed multi-stage compressor wherein
tolerances, efficiency, and rotor expense are exceptionally high
and critical.
The foregoing is accomplished by machining the curved edge of each
impeller blade by a desired amount for each impeller, from its
radially extending axial flow edge to its axially extending radial
flow edge. An additional shroud is provided that is oversize by an
amount diametrically and axially equal to the machining of the
blades so that it will efficiently cooperate with the machined
blades. Correspondingly, the free edges of the diffuser blades that
extend in a common radial plane and abut against the adjacent
shroud are machined an amount corresponding to the axial component
of the machining on the impeller blades, so that the diffusers will
operate efficiently at the new capacity. The shrouds and diffusers
are made as small as possible and separate so that the diffuser
blades may be readily removed and machined and the shrouds may be
readily removed and replaced with minimum expense and storage
facilities. To this latter end, separate fluid chamber rings are
provided around the diffusers and shrouds for conducting fluid in
cooperation with a one-piece cast casing having fluid channels
therein, so that all of the components may be releasably clamped as
a removable barrel within the casing to facilitate change of
capacity. In this manner, the capacity of the compressor may be
easily changed with minimum expense and expenditure of time and
effort, while maintaining high efficiency even with respect to high
speed, multi-stage compressors.
BRIEF DESCRIPTION OF THE DRAWING
Further objects, features, and advantages of the present invention
will become more clear from the following detailed description of
the drawing, wherein:
FIG. 1 is an axial cross section through a preferred embodiment of
a compressor according to the present invention set up for
operation at its highest capacity, with the capacity changing
machining being indicated by dotted lines and with ancillary
portions of the compressor removed; and
FIG. 2 shows the lower capacity shrouds of the preferred embodiment
that replaced the shrouds shown in FIG. 1 after machining.
DETAILED DESCRIPTION OF THE DRAWING
The compressor shown in FIG. 1 has a one-piece cast iron casing 1,
which is annular and has a through cylindrical opening therein
formed with fluid guide channels 2. A plurality of annular fluid
guides 3, corresponding in number to the number of stages, are
axially stacked within the casing 1 to form annular fluid chambers
4. Axially interposed between the fluid guides 3, are shrouds 5, 6,
7 and separate diffusers 8, 9, 10, which correspond to the three
separate stages. All of the elements 2-10 are axially stacked and
securely clamped by means of a bolt 11 threaded in a housing 12,
which is rigidly secured relative to the casing 1 by any known
means.
An overhung rotor 13 is rotatably mounted within a bearing 14
mounted within the housing 12 and provided with suitable seals
between the stages formed by its impellers 15, 16, 17. The impeller
15, shroud 5 and diffuser 8 form a first stage of the compressor
discharging into annular chamber 4, for interstage cooling at a
location not shown. The thus cooled fluid from the first stage
travels between the impeller 17, shroud 7 and diffuser 10 of the
second stage for discharge into the adjacent annular chamber 4 to
again be cooled by a second interstage cooler (not shown).
Thereafter, the thus cooled fluid from the second stage passes
between the impeller 16, shroud 6 and diffuser 9 of the third stage
for discharge into the adjacent annular chamber 4 from where it is
conducted to a point of usage.
While the principles of the present invention are specifically
related advantageously to a high speed centrifugal compressor
operating at approximately 54,000 r.p.m., with three-stage
compression, the broader aspects of the invention may be employed
with other fluid reaction type devices, for example low speed pumps
or high speed turbines.
Preferably, the casing 1 is constructed of cast iron, fluid guides
3 are constructed of aluminum, the shrouds 5, 6, 7 are constructed
of aluminum, the diffusers 8, 9, 10 are constructed of aluminum and
the rotor 13, including its blades is integrally constructed of
stainless steel. Thus, it is seen that the diffusers may be easily
machined, the shrouds are relatively cheaply constructed and easily
replaced, the shrouds and diffusers are of minimum size by
utilizing the stacked construction of separate components, the
shrouds, diffusers and rotor may be easily removed by the removable
barrel stacked construction, and the rotor 13 is an item of
considerable relative expense. The expense and criticality of the
rotor flow from its construction from stainless steel to resist the
extreme corrosive and abrasive affects of any fluid at the high
speeds contemplated, its integral construction necessary to obtain
an extremely rigid rotor that may be overhung, its extreme
sensitivity to vibrations due to its cantilevered overhung
mounting, and its extreme sensitivity to vibrations due to the high
speeds of operation. Thus, the rotor construction is quite critical
and expensive requiring accurate balancing and rigid construction
made quite difficult by the general difficulty of working stainless
steel. Thus, the replacement of this rotor would involve a
considerable expense and stocking of separate rotors would be
prohibitive in price. Further, the shape of the blades, conforming
configuration between the blades and adjacent shrouds, and the
diffuser through flow areas are all critical at the high speeds of
operation contemplated and the high pressures encountered with a
multi-stage compressor. Inaccuracies or mismatching of these items
with the capacity would be disastrous with respect to efficiency of
operation.
The capacity of the preferred embodiment of the compressor shown in
FIGS. 1 and 2 is changed by the following procedure. The bolt 11 is
removed and the stacked items of the barrel assembly are axially
removed from the casing 1 to disassemble the fluid guides 3,
shrouds 5, 6, 7, and diffusers 8, 9, 10 from the rotor 13 along
with the miscellaneous components required for sealing the
chambers. After disassembly, each blade is machined by an amount
that is the same for each impeller, which amount will most likely
vary from impeller to impeller. From the drawing it is seen that
the impellers for each stage are of the same type, that is they
have open centrifugal blades, so that the specific description of
one impeller will suffice for all of the impeller blades.
Therefore, with reference to impeller 15, each blade has a radially
extending free edge 18 for axial fluid flow, a free axially
extending edge 19 for radial fluid flow, a portion 20 extending
between edges adjacent the impeller hub 21, and a free curved edge
22 extending from the radially extending edge 18 to the axially
extending edge 19. The blades are twisted to correspondingly twist
the curved edge 22 by circumferentially offsetting the edges 18 and
19 for each blade. During the machining of the impellers, the
machining is conducted along the entire length of each curved edge
22 down to the dotted lines to reduce the radial extent of each
blade an equal amount for any one impeller or a predetermined
varying amount.
After the machining of all the impellers by the desired amount, the
diffusers are correspondingly machined to reduce their capacity by
substantially equal amounts. Each of the diffusers is of a similar
type so that the specific description of one will suffice for all.
The diffuser 8 includes an annular body portion 23 and a plurality
of peripherally spaced diffuser blades 24 oriented in a known
manner. Each of the blades 24 has an outer free edge 25, with all
of the edges 25 being contained within a common radial plane and
abutting against the adjacent shroud 5 in the assembled position.
To change the capacity of the diffuser 8, all of the edges 25 are
machined an equal amount along their entire length so that they
will lie in a new common plane generally indicated by the dotted
lines passing through the blades 24.
After the machining of the impellers on the rotor 13 and the
machining of the blades on the diffusers 8, 9, 10, the compressor
is reassembled, but this time with the shrouds 5', 6', 7' of FIG. 2
replacing the shrouds 5, 6, 7, respectively. For efficient
cooperation with the newly machined impellers and diffusers, the
shrouds of FIG. 2 are correspondingly larger than the shrouds 5, 6,
7. Thus, the annular surfaces 26', 27', 28' of the shrouds 5', 6',
7' are larger than the surfaces 26, 27, 28, respectively, of the
shrouds 5, 6, 7. The amount of this enlargement occurs at least
within the zone of the surfaces that are directly opposite the
curved edges 22 of the impeller blades, with the enlargement being
axially and radially correlated to the axial and radial dimension
changes of the impeller blades caused by machining for adjacent
areas. In addition, the over-all axial length of each shroud 5',
6', 7' is greater than the over-all axial length of each shroud 5,
6, 7, respectively, by an amount substantially corresponding to the
axial change in dimension of the impeller blades caused by
machining. Further, the axial dimension of each flange 29', 30',
31', of the shrouds 5', 6', 7' is larger than the axial dimension
of the flanges 29, 30, 31 of the shrouds 5, 6, 7, respectively, by
an amount substantially equal to the axial change in dimension of
the blades 24 caused by machining the diffusers.
While a single preferred embodiment of the present invention has
been specifically illustrated and described without illustrating
any variations, modifications or other embodiments, there is no
intention to be solely limited thereto, and further modifications,
embodiments and variations are contemplated according to the
broader aspects of the present invention. The teachings of the
present invention may be employed in other and quite different
fluid reactor device environments although they are specifically
well suited to the critical requirements of the specifically set
forth embodiment of a high speed compressor.
The compressor of the present invention is provided with two sets
of shrouds, which are constructed of relatively cheap material, for
example aluminum, and of a minimum dimension to reduce their
over-all storage bulk and expense. For a change of capacity, the
compressor is constructed for easy disassembly and uniform
machining of the impeller blades along their curved intermediate
free edges and uniform machining of the diffuser blades only along
a common radial plane, which radial plane machining is the easiest
to accomplish and least expensive. The machining of the diffusers
is further facilitated by the minimum size of the diffusers, their
separate construction and the use of an easily machinable material
such as aluminum. With the proper sizing of the replacement
shrouds, the clearances between impeller blades and the shrouds are
maintained for maximum performance and efficiency, and the through
flow cross section of the diffusers is changed expeditiously to
correspond to the change in capacity of the impellers. The
machining of the impeller blades along their curved free edges 22
will assure a maximum efficiency of the impeller blades both before
and after machining by maintaining their design shapes, which is
particularly seen if laminar flow through the impellers is assumed
and the machining is conducted along one of the lines of flow so
that the inner flow characteristics through the impellers are
substantially unchanged by machining. This last analysis would also
be true of flow through the diffusers. Further advantages or
machining along the curved edges of the impeller blades are
realized from the fact that this will have a minimum affect upon
the rotor balance, which is critical for high speed operation; this
is true because a very small total quantity of metal will be
removed due to the thinness of the blades adjacent their edges 22.
Machining of the diffuser blades will be particularly inexpensive
and easy to accomplish due to the fact that it is conducted along a
common plane for each diffuser.
Thus, the capacity of the compressor may be changed with a minimum
amount of effort while maintaining the efficiency of the device
even at high speeds. Further, the extremely expensive and critical
rotor does not have to be replaced and there is no added expense of
buying and storing a separate rotor, because it is only necessary
to purchase a second replacement set of relatively small
inexpensive shrouds which will take up little room in storage.
* * * * *