U.S. patent application number 15/122845 was filed with the patent office on 2017-04-13 for methods for making a low inertia laminated rotor.
The applicant listed for this patent is EATON CORPORATION. Invention is credited to William Nicholas EYBERGEN, Matthew James FORTINI, Michael Lee KILLIAN, James Kevin SPRING.
Application Number | 20170101989 15/122845 |
Document ID | / |
Family ID | 54072357 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170101989 |
Kind Code |
A1 |
EYBERGEN; William Nicholas ;
et al. |
April 13, 2017 |
METHODS FOR MAKING A LOW INERTIA LAMINATED ROTOR
Abstract
A rotor assembly having a plurality of rotor plates mounted to a
shaft, and methods of construction for a rotor assembly are
disclosed. Each rotor plate in the assembly may be provided with a
central opening extending between the first and second sides
through which the shaft extends. In one aspect, the rotor plates
are provided with a plurality of lobes extending away from the
central opening, wherein each of the lobes has a lobe opening
extending through the thickness of the plates. In one embodiment,
the rotor plates are rotationally stacked to form a helical
rotor.
Inventors: |
EYBERGEN; William Nicholas;
(Harrison Township, MI) ; KILLIAN; Michael Lee;
(Troy, MI) ; FORTINI; Matthew James; (Livonia,
MI) ; SPRING; James Kevin; (Brighton, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EATON CORPORATION |
Cleveland |
OH |
US |
|
|
Family ID: |
54072357 |
Appl. No.: |
15/122845 |
Filed: |
March 11, 2015 |
PCT Filed: |
March 11, 2015 |
PCT NO: |
PCT/US2015/019876 |
371 Date: |
August 31, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61951788 |
Mar 12, 2014 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 2240/70 20130101;
F04C 2230/60 20130101; F04C 2240/20 20130101; F04C 18/084 20130101;
F04C 2240/60 20130101; F04C 18/126 20130101; F01C 21/08 20130101;
F04C 18/16 20130101; F04C 2230/231 20130101 |
International
Class: |
F04C 18/12 20060101
F04C018/12 |
Claims
1. A method of making a laminated rotor, the method comprising the
steps of: a. providing a plurality of rotor plates, each of the
plates having a plurality of lobes extending radially away from a
central opening and a first indexing feature; b. providing a
mandrel having a second indexing feature; c. stacking each of the
rotor plates onto the mandrel such that the mandrel extends through
the central opening of each plate and such that the rotor plate
first indexing feature is aligned with the mandrel second indexing
feature; d. securing the rotor plates together; e. removing the
mandrel from the rotor plates; and f. inserting a shaft into the
central openings of the rotor plates.
2. The method of making a laminated rotor of claim 1, wherein the
step of providing a plurality of rotor plates includes providing at
least some of the rotor plates with openings in the rotor plate
lobes.
3. The method of making a laminated rotor of claim 1, wherein the
step of securing the rotor plates together includes welding the
rotor plates together.
4. The method of making a laminated rotor of claim 1, further
including the step of burring the shaft before the step of
inserting the shaft into the central openings of the rotor
plates.
5. The method of making a laminated rotor of claim 1, wherein the
step of inserting a shaft is performed after the step of securing
the rotor plates together.
6. The method of making a laminated rotor of claim 1 further
including the step of forming each of the plurality rotor plates by
one of stamping, fine blanking, laser cutting, and water jet
cutting.
7. The method of making a laminated rotor of claim 1, wherein the
step of providing a mandrel includes providing a mandrel with the
second indexing feature having a plurality of protrusions extending
along a length of the mandrel.
8. The method of making a laminated rotor of claim 7, wherein the
step of providing a mandrel includes providing a mandrel with the
second indexing feature having a plurality of helical
protrusions.
9. The method of making a laminated rotor of claim 8, wherein the
step of providing a mandrel includes providing a mandrel with the
second indexing feature having three helical protrusions.
10. The method of making a laminated rotor of claim 8, wherein the
step of providing a plurality of rotor plates includes providing a
plurality of rotor plates having a plurality of recesses forming
the first indexing feature.
11. The method of making a laminated rotor of claim 10, wherein the
steps of providing a mandrel and providing a plurality of rotor
plates includes providing a mandrel with a number of protrusions
that is equal to a number of recesses provided on each rotor
plate.
12. A rotor assembly comprising: a. a plurality of rotor plates,
each including: i. a first side and a second opposite side
separated by a first thickness; ii. a central opening extending
between the first and second sides; iii. a plurality of lobes
extending away from the central opening; iv. an indexing feature
including at least one recess extending from the central opening;
and b. a shaft extending through the central opening of each of the
plurality of rotor plates; c. wherein the plurality of rotor plates
are stacked and secured together to form the rotor assembly such
that at least one of the first and second sides of one rotor plate
is adjacent to and in contact with at least one of the first and
second sides of another rotor plate.
13. The rotor assembly of claim 12, wherein the rotor plates are
rotated with respect to each other to form a helical rotor.
14. The rotor assembly of claim 13, wherein each of the plurality
of rotor plates includes first, second, and third lobes that are
radially spaced apart by an equal angular degree.
15. The rotor assembly of claim 14, wherein each of the plurality
of rotor plates further includes a fourth lobe, wherein the first,
second, third, and fourth lobes are radially spaced apart by an
equal angular degree.
16. The rotor assembly of claim 13, wherein the helical rotor has
an overall length that is generally equal to the sum of the first
thicknesses of the plurality of stacked rotor plates.
17. The rotor assembly of claim 12, wherein each of the plurality
of lobes includes a lobe opening.
18. The rotor assembly of claim 12, wherein each of the rotor
plates is formed from a metal material.
19. The rotor assembly of claim 18, wherein each of the rotor
plates is formed from stainless steel.
20. The rotor assembly of claim 18, wherein the rotor plates are
secured together by welding.
Description
RELATED APPLICATIONS
[0001] This application is being filed on Mar. 11, 2015, as a PCT
International Patent application and claims priority to U.S. Patent
Application Ser. No. 61/951,788 filed on Mar. 12, 2014, the
disclosure of which is incorporated herein by reference in its
entirety.
TECHNICAL FIELD
[0002] This present disclosure relates to rotor assemblies that may
be utilized in rotary equipment applications, for example,
volumetric expansion and compression devices.
BACKGROUND
[0003] Rotors are a commonly used in applications where it is
desirable to compress or move a fluid and where it is desired to
remove energy from the fluid. In one example, a compressor or
supercharger utilizes a pair of rotors to increase airflow into the
intake of an internal combustion engine. In another example, a
volumetric fluid expander includes a pair of rotors that expand a
working fluid to generate useful work at an output shaft. In such
applications, it is known to provide machined or cast rotors having
a unitary construction with a solid cross-sectional area.
Improvements are desired.
SUMMARY
[0004] The disclosure is directed to a rotor assembly comprising a
plurality of rotor plates mounted to a shaft. In one aspect, each
of the rotor plates has a first side and a second opposite side
separated by a first thickness. Each rotor plate may also be
provided with a central opening extending between the first and
second sides through which the shaft extends. In yet another
aspect, the rotor plates are provided with a plurality of lobes
extending away from the central opening, wherein each of the lobes
has a lobe opening extending between the first and second sides.
The plurality of rotor plates are stacked and secured together to
form the rotor assembly such that at least one of the first and
second sides of one rotor plate is adjacent to and in contact with
at least one of the first and second sides of another rotor plate.
In one embodiment, the rotor plates are stacked directly upon each
other such that the entirety of one side of one rotor plate is
entirely covered by an adjacent rotor plate. In one embodiment, the
rotor plates are rotationally stacked to form a helical rotor such
that one rotor plate does not entirely cover the adjacent rotor
plate. The disclosure also includes a volumetric fluid expander and
a compressor or supercharger including a pair of the above
described rotors.
[0005] The disclosure also is directed to a process for making a
laminated rotor assembly. In one step of the process a plurality of
rotor plates are provided in accordance with the above description.
In one step, the rotor plates are stacked together to form either a
straight rotor or a helical rotor. In one step, the rotor plates
are secured together, for example by welding. In one step, the
rotor is mounted to a shaft to form the laminated rotor assembly.
The shaft may be burred to better engage the shaft with the stacked
rotor plates. The process may also include applying an abradable
coating to the rotor as well.
[0006] In one embodiment, each of the rotor plates may also be
provided with a first indexing feature configured to align with a
second indexing feature on a mandrel. In such a configuration, a
second process for constructing the laminated rotor assembly may
include the steps of providing a plurality of rotor plates having
the first indexing feature and providing a mandrel having the
second indexing feature. In one step of the second process, the
rotor plates are stacked onto the mandrel such that the mandrel
extends through the central opening of each plate and such that
each rotor plate first indexing feature is aligned with the mandrel
second indexing feature. In one embodiment, the second indexing
feature extends along the length of the mandrel and is parallel to
the longitudinal axis of the mandrel such that a straight rotor
will be formed. In one embodiment, the second indexing feature
extends along the length of the mandrel and has a helical shape
such that a helical rotor will be formed.
[0007] In one step of the second process, the rotor plates are
secured together, for example, by welding. In one step of the
second process, the mandrel is removed from the rotor plates. In
one embodiment, an extraction tool is provided that presses the
mandrel out of the assembled rotor plates. In one step of the
second process, a shaft which may be provided with burrs is
inserted into the central openings of the rotor plates to form the
rotor assembly. As with the first process, an abradable coating may
be applied to the assembled rotor in the second process. In one
step of the second process, balancing holes may be provided, for
example by drilling holes into the stacked rotor plates, to
rotationally balance the rotor assembly.
[0008] The above features and advantages and other features and
advantages of the present teachings are readily apparent from the
following detailed description of the best modes for carrying out
the present teachings when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a low inertia laminated
rotor assembly in accordance with the principles of the present
disclosure.
[0010] FIG. 2 is a top view of a rotor plate usable in the rotor
assembly shown in FIG. 1.
[0011] FIG. 3 is a side view of the rotor plate shown in FIG.
2.
[0012] FIG. 4 is a top view of a rotor plate usable in the rotor
assembly shown in FIG. 1.
[0013] FIG. 5 is a top view of a rotor plate usable in the rotor
assembly shown in FIG. 1.
[0014] FIG. 6 is a perspective view of the unitary rotor with the
shaft removed.
[0015] FIG. 7 is a perspective view of a shaft onto which the rotor
plates of FIGS. 2-5 may be mounted.
[0016] FIG. 8 is an end view of the shaft shown in FIG. 7 in a die
forming process.
[0017] FIG. 9 is a schematic showing a process for producing a
laminated rotor.
[0018] FIG. 10 is a schematic view of a vehicle having a fluid
expander and a compressor in which rotor assemblies of the type
shown in FIG. 1 may be included.
[0019] FIG. 11 is a schematic showing a second process for
producing a laminated rotor.
[0020] FIG. 12 is a perspective view of a rotor assembly apparatus
that may be used in the second process for producing a laminated
rotor shown at FIG. 10.
[0021] FIG. 13 is a perspective view of the rotor assembly
apparatus shown in FIG. 12 with a rotor plate aligned with the
mandrel.
[0022] FIG. 14 is a perspective view of the rotor assembly
apparatus shown in FIG. 12 with a rotor plate aligned with the
mandrel.
[0023] FIG. 15 is a perspective view of the rotor assembly
apparatus shown in FIG. 12 with a rotor plate aligned with the
mandrel and with a rotor plate mounted about the mandrel.
[0024] FIG. 16 is a perspective view of the rotor assembly
apparatus shown in FIG. 12 with two rotor plates mounted about the
mandrel.
[0025] FIG. 17 is a perspective view of the rotor assembly
apparatus shown in FIG. 12 with a plurality of rotor plates mounted
about the mandrel to form a completed rotor.
[0026] FIG. 18 is a perspective view of the rotor and rotor
assembly apparatus shown in FIG. 17 with an additional base portion
secured to the assembly such that the rotor plates can be secured
together to form a unitary rotor.
[0027] FIG. 19 is a perspective view of the completed rotor with
the base portions removed from the mandrel and with the plates
secured to each other.
[0028] FIG. 20 is a perspective view of the unitary rotor and
mandrel mounted in a mandrel extraction tool.
DETAILED DESCRIPTION
[0029] Various embodiments will be described in detail with
reference to the drawings, wherein like reference numerals
represent like parts and assemblies throughout the several views.
Reference to various embodiments does not limit the scope of the
claims attached hereto. Additionally, any examples set forth in
this specification are not intended to be limiting and merely set
forth some of the many possible embodiments for the appended
claims. Referring to the drawings wherein like reference numbers
correspond to like or similar components throughout the several
figures.
Rotor Construction
[0030] Referring to FIG. 1, a complete laminated rotor assembly 5
is presented. As shown, laminated rotor 30 includes a plurality of
stacked rotor plates 200 that are mounted to a common shaft 38. In
the embodiment shown, the rotor plates 200 are rotationally stacked
such that the rotor assembly 30 has a helical rotor having a
constant helix angle. By use of the term "rotationally stacked," it
is meant that the plates are rotationally offset with respect to
each other such that one rotor plate does not entirely cover an
adjacent rotor plate. The laminated rotor 30 can also be provided
as a straight rotor by stacking the rotor plates 200 such that
adjacent plates 200 completely cover each other.
[0031] Examples of a rotor plate 200 are shown at FIGS. 2-5. As
shown, rotor plate 200 has three radially spaced lobes 202-1,
202-2, 202-3 (collectively referred to as lobes 202) extending away
from a central axis X to a respective tip portion 203-1, 203-2,
203-2 (collectively tips 203). In one aspect, the lobes 202 have or
define a convex outline and the root portions 204 have or define a
concave outline that together define an outer perimeter 206 of the
rotor plate 200.
[0032] As shown, the lobes 202 are equally spaced apart by adjacent
root portions 204-1, 204-2, 204-3 (collectively referred to as root
portions 204) at a first separation angle a1. In the embodiment
shown, the separation angle a1 is about 120 degrees. Although three
lobes are shown, it should be understood that fewer or more lobes
may be provided with corresponding separation angles, for example,
two lobes with a separation angle of 180 degrees, four lobes with a
separation angle of 90 degrees, five lobes with a separation angle
of 72 degrees, and six lobes with a separation of 60 degrees. When
stacked together to form a rotor 30, the central axis X of each
rotor plate 200 is coaxial with axis X1, X2, respectively.
[0033] Each rotor plate 200 also has a first side 208 and a second
side 210 separated by a first thickness t1. In one embodiment, the
thickness t1 is about 0.25 millimeters (mm). However, it should be
noted that other thicknesses may be used, for example, thicknesses
between about 0.1 mm and about 1 mm and between about 0.1 mm and
about 0.5 mm. Each plate 200 is also shown as being provided with a
central opening 212 extending between the first and second sides
208, 210, wherein the central opening 212 is centered on the
central axis X.
[0034] An indexing feature 214 may also be provided adjacent to or
as part of the central opening 212. In the embodiment shown, the
indexing feature 214 includes three radially spaced notches 214-1,
214-2, and 214-3 that are respectively aligned with the lobes
202-1, 202-2, and 202-3. As discussed in greater detail with
respect to rotor assembly method 2000, the indexing feature 214
allows the rotor plates 200 to be aligned relative to one another
during the stacking or assembly process. Although three notches are
shown for the indexing feature 214, it should be understood that
more or fewer notches or other features capable of performing an
alignment function may be provided, such as tabs extending towards
the center of the central opening 212.
[0035] With reference to the rotor plate 200 shown at FIG. 2, it
can be seen that the lobes 202 are entirely solid material such
that the only opening that extends through the thickness t1 of the
rotor is the central opening 212. This type of lobe may be referred
to as a solid lobe and a rotor plate having such lobes may be
referred to as a solid-lobe rotor plate. However, the rotor plate
200 may be provided with one or more openings within each lobe.
This type of lobe may be referred to as a hollow lobe and a rotor
plate having such lobes may be referred to as a hollow-lobe rotor
plate.
[0036] Referring to FIG. 4, an example of a hollow-lobe rotor plate
200 is shown in which each lobe 202 is provided with a respective
opening 205-1, 205-2, 205-3 (collectively openings 205). In one
aspect, each opening 205 has an area that is the majority of the
surface area of the lobe 202, as defined by the outer perimeter of
the lobe 202. In one aspect, the total opening area defined by the
openings 205 and the central opening 212 is greater than the total
area defined by the outer perimeter 206 of the rotor plate 200. In
one aspect, the openings 205 are configured such that the remaining
material of the lobe 202, adjacent the outer perimeter 206 and
proximate the tip portion 203, has a generally constant width w1.
Near the root portions 204, the material width is shown as being
increased from the first width w1 for greater strength.
[0037] In the embodiment shown at FIG. 4, the total opening area of
the openings 205 and central opening 212 is about 50% of the total
area defined by the outer perimeter 206 resulting in a rotor plate
200 that has about 50% less material, as compared to a solid-lobe
rotor with the same central opening size. The size and
configuration of the openings 205 in the rotor plate 200 can be
configured to result in a total opening area ranging from 0% to 70%
of the total perimeter area, and preferably between about 30% and
about 60% of the total perimeter area. Stated in other terms, the
size and configuration of the openings 205 in the rotor plate 200
can be configured to result in a total material reduction ranging
from 0% to about 70%, and preferably between about 30% and about
60% of the total perimeter area.
[0038] The provision of an opening 205 in the lobe 204, as shown in
FIG. 4, substantially reduces the amount of material required to
form the rotor 30. Accordingly, the weight of the rotor plate 200,
and thus the weight of the rotor 30 is significantly less as
compared to a solid rotor or a laminated rotor using solid-lobe
plates. As importantly, the moment of inertia or rotational inertia
of the rotor plate 200, and thus the assembled rotor 30, is
substantially reduced as compared to a solid material rotor. In the
embodiment shown, the rotational inertia of the rotor plate 200 and
rotors 30 is about 45% less than a solid rotor made of the same
material and having the same geometric configuration. The size and
configuration of the openings 205 in the rotor plate 200 can be
configured to result in a reduction of rotational inertia, as
compared to a solid rotor, ranging from 0% to about 45% and
preferably between about 25% to 55%. Although the rotor plate 200
shown in FIGS. 4 and 5 is shown with one opening 205 in each lobe
202, more than one opening may be provided in each lobe as desired,
for example, two, three, or four openings 205 in each lobe 202.
[0039] With reference to FIG. 5, the openings 205-1, 205-2, 205-3
are provided as smaller circular openings that can be used for the
purpose of determining the geometric center of the rotor plate 200
during assembly. The holes 205-1, 205-2, 205-3 allow for the center
of the rotor lobe to be accurately identified and indexed in a
machining process after assembly of the rotor 30. Where holes
205-1, 205-2, 205-3 are provided, an indexing tool can then be used
that references the holes 205-1, 205-2, 205-3 for the machining
process.
[0040] As the mass of the rotor 30 is reduced when constructed from
at least some hollow-lobe rotor plates 200, the rotor plates 200
can be made from a material that is sufficient to maintain
structural integrity under high temperature and loads, such as
would be the case where a volumetric fluid expander 20 (discussed
later) having rotor assemblies 5 receives direct exhaust from an
internal combustion engine. In some examples, each of the rotor
plates 200 is fine blanked, stamped, or laser or water jet cut from
a thin sheet of metal, such as stainless steel, carbon steel or
aluminum. The material can be pre-coated using a silk screen
process with copper or nickel.
Rotor Assembly Method 1000
[0041] Referring to FIG. 9, an example of a rotor assembly system
and process 1000 in accordance with the disclosure is presented. It
is noted that although the figures diagrammatically show steps in a
particular order, the described procedures are not necessarily
intended to be limited to being performed in the shown order.
Rather at least some of the shown steps may be performed in an
overlapping manner, in a different order and/or simultaneously.
Also, the process shown in FIG. 8 is exemplary in nature and other
steps or combinations of steps may be incorporated or altered
without departing from the central concepts disclosed herein.
[0042] In a step 1002, a plurality of rotor plates 200 in
accordance with the above description are provided. In a step 1004,
each of the provided rotor plates 200 is stacked such that at least
a portion of one of the rotor plate sides 208, 210 is adjacent and
in contact with another rotor plate side 208, 210. In the
embodiment shown, the sides 208, 210 of each rotor plate 200 are
completely planar such that, when stacked, no gap exists between
adjacent rotor plates. As presented, each rotor plate 200 is
slightly offset from the adjacent rotor plate about the central
axis X to form a helical rotor 30.
[0043] It is noted that many configurations of stacked rotor plates
200 are possible using assembly method 1000. In the example
embodiment shown, the stack could include closed-lobe rotor plates
with indexing holes of the type shown in FIG. 5 at each end with
hollow-lobe rotor plates of the type shown in FIG. 4 there between.
In another embodiment, the stack could consist entirely of
hollow-lobe rotor plates of the type shown in FIG. 4.
Alternatively, the stack could include closed-lobe rotor plates of
the type shown in FIG. 2 at each end with hollow-lobe rotor plates
of the type shown in FIG. 4 there between. In even yet another
configuration, the stack could include alternating hollow-lobe
rotor plates with solid-lobe rotor plates. Alternatively, the stack
could include a majority of the plates as being hollow-lobe rotor
plates with solid-lobe rotor plates being inserted incrementally
throughout the stack, for example, every tenth plate could be a
solid-lobe rotor plate with the remaining plates being a
hollow-lobe type.
[0044] In a step 1006, the rotor plates 200 are secured together.
The stacked rotor plates 200 can be secured together, for example
by welding. In one example, the plates 200 are secured together by
laser welding. In another example, the rotor plates 200 can be
welded together in a vacuum or continuous belt furnace. In an
alternative, the plates 200 can be plated and resistive-welded
together. In one embodiment, the rotor plates 200 are secured with
welds that extend along the rotor plate tips 203 and along each
side of the rotor lobes 202 for a total of nine helical welds that
traverse the length of the rotor. Other weld configurations are
possible as well, as are other attachment means, such as
adhesives.
[0045] FIG. 6 shows the rotor 30 after the plates have been stacked
and secured together.
[0046] Once the rotor plates 200 are secured together, such as by
one of the above described welding processes, the rotor shaft 38
can be pressed onto the rotor 30 in a step 1008 to create the rotor
assembly 5 shown at FIG. 1. In one embodiment, and as can be seen
at FIGS. 7 and 8, the rotor shaft 38 is formed by a die set 540 to
include a plurality of burrs 542 set at 90-degree increments about
the output shaft 38. The height of the burrs 542 is set to
interference fit with the central opening 212 in the plates 200
that form the rotor 30 when the shaft 38 is inserted therein. This
permits power to be transferred from the rotor plates 200 to the
shaft 38.
[0047] In a step 1010, a coating is applied to the rotor plates 200
of the rotor 30. In one embodiment, the coating is an abradable
coating to allow tighter clearances between a pair of adjacent
rotors 30, which may be especially useful in high temperature
applications.
Rotor Assembly Applications
[0048] The above described rotor assembly 5 may be used in a
variety of applications involving rotary devices. Two such
applications are for use in a fluid expander 20 and a compression
device 21 (e.g. a supercharger), as shown in FIG. 10. In one
embodiment, the fluid expander 20 and compression device 21 are
volumetric devices in which the fluid within the expander 20 and
compression device 21 is transported across the rotors 30 without a
change in volume. FIG. 10 shows the expander 20 and supercharger 21
being provided in a vehicle 10 having wheels 12 for movement along
an appropriate road surface. The vehicle 10 includes a power plant
16 that receives intake air 17 and generates waste heat in the form
of a high-temperature exhaust gas in exhaust 15. The power plant 16
may be an internal combustion (IC) engine or a fuel cell.
[0049] As shown, the expander 20 receives heat from the power plant
exhaust 15 and converts the heat into useful work which can be
delivered back to the power plant 16 to increase the overall
operating efficiency of the power plant. As configured, the
expander 20 includes housing 23 within which a pair of rotor
assemblies 5 having intermeshed rotors 30 and shafts 38 are
disposed. The expander 20 having rotor assemblies 5 can be
configured to receive heat from the power plant 16 directly or
indirectly from the exhaust.
[0050] One example of a fluid expander 20 that directly receives
exhaust gases from the power plant 16 is disclosed in Patent
Cooperation Treaty (PCT) International Application Number
PCT/US2013/078037 entitled EXHAUST GAS ENERGY RECOVERY SYSTEM.
PCT/US2013/078037 is herein incorporated by reference in its
entirety.
[0051] One example of a fluid expander 20 that indirectly receives
heat from the power plant exhaust via an organic Rankine cycle is
disclosed in Patent Cooperation Treaty (PCT) International
Application Publication Number WO 2013/130774 entitled VOLUMETRIC
ENERGY RECOVERY DEVICE AND SYSTEMS. WO 2013/130774 is incorporated
herein by reference in its entirety.
[0052] Still referring to FIG. 10, the compression device 21 is
shown as being provided with housing 25 within which a pair of
rotor assemblies 5 having intermeshed rotors 30 and shafts 38 are
disposed. As configured, the compression device is driven by the
power plant 16. As configured, the compression device 21 increases
the amount of intake air 17 delivered to the power plant 16. In one
embodiment, compression device 21 is a Roots-type blower of the
type shown and described in U.S. Pat. No. 7,488,164 entitled
OPTIMIZED HELIX ANGLE ROTORS FOR ROOTS-STYLE SUPERCHARGER. U.S.
Pat. No. 7,488,164 is hereby incorporated by reference in its
entirety.
Material Selection
[0053] Where the rotors 30 are disposed in a housing, such as
housings 23 and 25, proper consideration must be given to material
selection for the rotors and the housing in order to maintain
desirable clearances between the rotors and housing. For example,
improper material selection can result in a rotor that expands when
heated by a working fluid (e.g. engine exhaust) into the interior
wall of the housing, thereby damaging the rotor and housing and
rendering the device inoperable. Proper selection of materials
having appropriate relative coefficients of thermal expansion will
result in a rotor that, in the expanded state, will not contact an
also expanded housing and will maintain a minimum clearance between
the rotors and housing for maximum efficiency across a broader
range of temperatures. Also, as the rotors are more directly
exposed to the working fluid (e.g. exhaust gases or a solvent used
in a Rankine cycle) and the housing can radiate heat to the
exterior, the rotors can be expected to expand to a greater degree
than the housing. Accordingly, it is desirable to select a material
for the rotors that has a coefficient of thermal expansion that is
lower than a coefficient of thermal expansion of the housing.
[0054] Because the rotors can be provided with hollow lobes, a
wider selection of materials having relatively low coefficients of
thermal expansion may be used for the rotors because the resulting
rotational inertia of a hollow-lobe rotor made from plates having a
relatively high density can be the same or lower than the
rotational inertia of a solid-lobe cast, machined, or laminated
rotor made from a material having a relatively low density. For
example, a stainless steel rotor with hollow lobes can be created
with a rotational inertia generally similar to a solid-lobe
aluminum rotor. As such, the disclosed rotor design allows a
greater degree of material selection for the rotor which further
widens the suitability of various materials for the housing.
[0055] In one particular application, the rotor assemblies 5 are
used in an expander that receives exhaust gases from an internal
combustion engine. In such an application, it is necessary that the
rotor plates 200 be formed from a material that is suitable for
operation at high exhaust gas temperatures, for example, stainless
steel, tungsten, titanium, and carbon steel. As the rotors 30 can
be provided with hollow lobes, these materials can be used in a
high temperature expander application without resulting in a rotor
30 that has a rotational inertia that is too high for efficient
operation. In one embodiment, stainless steel rotors are used in
conjunction with an aluminum housing. As stainless steel has a
lower coefficient of thermal expansion than aluminum, both the
housing and the rotors will expand, but to a degree wherein each
component expands to achieve clearances that allow for maximum
efficiency. Of course, many other possibilities exist for rotor and
housing materials based on desired performance criteria.
Rotor Assembly Method 2000
[0056] Referring to FIGS. 11-24, an example of a rotor assembly
system and process 2000 in accordance with the disclosure is
presented. It is noted that although the figures diagrammatically
show steps in a particular order, the described procedures are not
necessarily intended to be limited to being performed in the shown
order. Rather at least some of the shown steps may be performed in
an overlapping manner, in a different order and/or simultaneously.
Also, the process shown in FIG. 11 is exemplary in nature and other
steps or combinations of steps may be incorporated or altered
without departing from the central concepts disclosed herein.
[0057] In a step 2002, a rotor assembly apparatus 300 is provided.
As shown at FIG. 12, the rotor assembly apparatus includes an end
plate 302 and a base plate 304 having a central opening 304a. A
mandrel 306 is also provided that extends from the base plate 302.
Referring to FIG. 13, it can be seen that the base plate 304 is
mounted over the mandrel 306 and abutting the end plate 302. As
shown at FIG. 12, the mandrel has an index feature 308 including
projections 308-1, 308-2, and 308-3. As shown, the projections 308
are provided along the length of the mandrel 306 and wrap about the
mandrel 306 to form a helix such that a helical rotor 30 can be
formed. However, it is noted that the projections 308 can be
provided as straight projections running parallel to the length of
the mandrel 306 such that a straight rotor 30 can be formed.
[0058] The index feature 308 is configured to engage with the index
feature 214 of each rotor plate 200 such that projection 308-1
aligns with notch 214-1, projection 308-2 aligns with notch 214-2,
and projection 308-3 aligns with notch 214-3 when the rotor plates
200 are stacked onto the mandrel 308. It is also noted that the
index feature 308 can be provided with recesses or channels instead
of projections to cooperate with corresponding tabs that would be
provided on the rotor plates 200.
[0059] In the particular embodiment shown, the index feature 308
will impart a gradual helical twist for the assembled rotor 30 that
will have a helix angle as defined by the index feature 308. The
total twist angle of the rotor 30 can be defined by the total
number of stacked rotor plates 200 and the helix angle defined by
the index feature 308. In the embodiment shown, the helix angle
defined by the mandrel indexing feature 308 is constant. However,
the helix angle defined by the indexing feature 308 on the mandrel
306 may be increasing or decreasing along the length of the mandrel
306 such that a variable helix angle is imparted onto the stacked
rotor plates 200.
[0060] In a step 2004, a plurality of rotor plates 200 in
accordance with the above description are provided. In a step 2006,
each of the provided rotor plates 200 is stacked onto the mandrel
306 such that the mandrel 306 extends through each of the central
openings 212 of the rotor plates 200 and the index features 308,
214 are aligned. With reference to FIG. 14, it can be seen that a
first rotor plate 200a of the type shown at FIG. 11 is aligned with
the mandrel 306. FIG. 15 shows a rotor plate 200a of the shown in
FIG. 5 installed onto the mandrel 306 with a second rotor plate
200b of the type shown at FIG. 4 being aligned with the mandrel
306. FIG. 16 shows the second rotor plate 200b being installed onto
the mandrel 306 adjacent the first rotor plate 200a. FIG. 17 shows
the process at the point where a plurality of second rotor plates
200b have been stacked together with another two first rotor plates
200a resting on the top of the stack for a total of 125 stacked
rotor plates 200. Because of the helical index feature 308 on the
mandrel 306, it can be seen that each rotor plate 200 is slightly
offset from the adjacent rotor plate about the central axis X to
form a helical rotor. As configured, each of the stacked rotor
plates 200 is adjacent to another rotor plate 200 such that no gap
exists between the adjacent plates.
[0061] It is noted that many configurations of stacked rotor plates
200 are possible using assembly method 2000. In the example
embodiment shown, the stack could include closed-lobe rotor plates
with indexing holes of the type shown in FIG. 5 at each end with
hollow-lobe rotor plates of the type shown in FIG. 4 there between.
In another embodiment, the stack could consist entirely of
hollow-lobe rotor plates of the type shown in FIG. 4.
Alternatively, the stack could include closed-lobe rotor plates of
the type shown in FIG. 2 at each end with hollow-lobe rotor plates
of the type shown in FIG. 4 there between. In even yet another
configuration, the stack could include alternating hollow-lobe
rotor plates with solid-lobe rotor plates. Alternatively, the stack
could include a majority of the plates as being hollow-lobe rotor
plates with solid-lobe rotor plates being inserted incrementally
throughout the stack, for example, every tenth plate could be a
solid-lobe rotor plate with the remaining plates being a
hollow-lobe type.
[0062] In a step 2008, the rotor plates 200 are secured together as
shown at FIG. 18. In one embodiment, the rotor plates 200 are
initially secured together by mounting a top plate 310 over the
mandrel 306 and securing the top plate 310 with a bushing 312 and
nut 314. When the nut is tightened, a compression force is exerted
on the stacked rotor plates via the top plate 310, the bottom plate
304, and the mandrel 306. The stacked rotor plates 200 can then be
further secured together, for example by welding. In one example,
the plates 200 are secured together by laser welding. In another
example, the rotor plates 200 can be welded together in a vacuum or
continuous belt furnace. In an alternative, the plates 200 can be
plated and resistive-welded together. In one embodiment, the rotor
plates 200 are secured with welds that extend along the rotor plate
tips 203 and along each side of the rotor lobes 202 for a total of
nine helical welds that traverse the length of the rotor. Other
weld configurations are possible as well, as are other attachment
means, such as adhesives.
[0063] Once the rotor plates 200 are secured together, such as by
one of the above described welding processes, the rotor plates 200
and mandrel 306 can be removed from the end plate 302, base plate
304, and top plate 306, as shown at FIG. 19. In a step 2010, the
mandrel 306 is extracted from the secured rotor plates 200 with the
rotor assembly apparatus 300 reconfigured as an extraction tool
wherein first end plate 302 is secured to a second end plate 320
via a plurality of connecting rods 322. A push rod 324 can then be
provided that forces the mandrel through the stacked rotor plates
200 to result in the stacked rotor plate assembly shown in FIG.
21.
[0064] In a step 2012, the rotor shaft 38 is pressed into the
stacked rotor plate assembly to create an assembled rotor 30, as
shown at FIG. 1. In a step 2014, a coating is applied to the rotor
plates 200 of the rotor 30. In one embodiment, the coating is an
abradable coating to allow tighter clearances between two adjacent
rotors 30 which may be especially useful in high temperature
applications. In a step 1016, the rotor assembly 5 is balanced. In
one embodiment, the rotor assembly 5 is balanced by selectively
removing material from one or more of the lobes of one or more
rotor plates 200.
[0065] While the best modes for carrying out the many aspects of
the present teachings have been described in detail, those familiar
with the art to which these teachings relate will recognize various
alternative aspects for practicing the present teachings that are
within the scope of the appended claims.
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