U.S. patent application number 15/445458 was filed with the patent office on 2017-06-15 for optimized performance strategy for a multi-stage volumetric expander.
The applicant listed for this patent is Eaton Corporation. Invention is credited to William Nicholas EYBERGEN, Matthew James FORTINI.
Application Number | 20170167302 15/445458 |
Document ID | / |
Family ID | 55400323 |
Filed Date | 2017-06-15 |
United States Patent
Application |
20170167302 |
Kind Code |
A1 |
FORTINI; Matthew James ; et
al. |
June 15, 2017 |
OPTIMIZED PERFORMANCE STRATEGY FOR A MULTI-STAGE VOLUMETRIC
EXPANDER
Abstract
A multi-stage expansion device having bypass capabilities and a
variable speed drive is disclosed. In one example, the multi-stage
expansion device has a housing within which a first stage, a second
stage, and a third stage are housed. The housing may also be
configured with internal working fluid passageways to direct a
working fluid from the first stage to the second stage and/or from
the second stage to the third stage. Each of the stages may include
a pair of non-contacting rotors that are mechanically connected to
each other and to a power output device such that energy extracted
from the working fluid is converted to mechanical work at the
output device. In one example, a bypass line is provided to bypass
working fluid around the first stage and a bypass line is provided
to bypass working fluid around the second stage.
Inventors: |
FORTINI; Matthew James;
(Livonia, MI) ; EYBERGEN; William Nicholas;
(Harrison Township, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Eaton Corporation |
Cleveland |
OH |
US |
|
|
Family ID: |
55400323 |
Appl. No.: |
15/445458 |
Filed: |
February 28, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US2015/044529 |
Aug 10, 2015 |
|
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15445458 |
|
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62043082 |
Aug 28, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01C 20/02 20130101;
F01K 23/065 20130101; F02G 5/02 20130101; F01K 23/10 20130101; F01C
1/16 20130101; F01C 20/26 20130101; F01K 7/20 20130101; F01C 20/08
20130101; F01C 11/002 20130101; F01K 7/04 20130101; F01C 21/18
20130101; F01C 21/008 20130101; F01N 5/02 20130101; F01K 7/02
20130101 |
International
Class: |
F01K 7/20 20060101
F01K007/20 |
Goverment Interests
GOVERNMENT LICENSE RIGHTS
[0002] This invention was made with government support under
Contract No. DE-EE0005650 awarded by the National Energy Technology
Laboratory funded by the Office of Energy Efficiency &
Renewable Energy of the United States Department of Energy. The
government has certain rights in the invention.
Claims
1. A multi-stage volumetric fluid expansion device comprising: a. a
first fluid expansion stage having a first pair of non-contacting
rotors disposed between a first inlet and a first outlet, the first
fluid expansion stage being configured to generate useful work at
the first pair of rotors by expanding a working fluid from a first
pressure to a second pressure that is lower than the first
pressure; b. a second fluid expansion stage having a second pair of
non-contacting rotors disposed between a second inlet and a second
outlet, the second fluid expansion stage being configured to
generate useful work at the second pair of rotors by receiving the
working fluid from the first fluid expansion stage outlet and
expanding the working fluid to a third pressure that is lower than
the second pressure; c. a third fluid expansion stage having a
third pair of non-contacting rotors disposed between a third inlet
and a third outlet, the third fluid expansion stage being
configured to generate useful work at third pair of rotors by
receiving the working fluid from the second fluid expansion stage
outlet and expanding the working fluid to a fourth pressure that is
lower than the third pressure; d. a first working fluid bypass line
extending between the first inlet and first outlet of the first
fluid expansion stage, the first working fluid bypass line
including a first control valve; e. a second working fluid bypass
line extending between the first inlet and first outlet of the
second fluid expansion stage, the second working fluid bypass line
including a second control valve; f. a power output device rotated
by the first, second, and second third of rotors.
2. The multi-stage volumetric fluid expansion device of claim 1,
further comprising: a. a variable speed drive for controlling the
rotational speed of the fluid expansion device first, second, and
third pairs of rotors, the variable speed drive including a motor
connected to the power output device.
3. The multi-stage volumetric fluid expansion device of claim 1,
further comprising: a. a housing within which the first, second,
and third pairs of rotors is disposed, wherein the second outlet
and third inlet are joined within the housing to form a continuous
working fluid passageway extending between the second inlet and the
third outlet, wherein the first bypass line includes a bypass
connection tube extending through the housing and into the
passageway, wherein the second bypass line includes a bypass
connection tube extending through the housing and into the
passageway
4. The multi-stage volumetric fluid expansion device of claim 1,
wherein: a. the first outlet and the second inlet are joined within
the housing to form a continuous working fluid passageway extending
between the first inlet and the third outlet.
5. The multi-stage volumetric fluid expansion device of claim 1,
wherein: a. the first pair of rotors have twisted non-contacting
lobes, wherein one of the first pair of rotors has a number of
twisted lobes that equals a number of twisted lobes of the other of
the first pair of rotors; b. the second pair of rotors have twisted
non-contacting lobes, wherein one of the second pair of rotors has
a number of twisted lobes that equals a number of twisted lobes of
the other of the second pair of rotors; and c. the third pair of
rotors have twisted non-contacting lobes, wherein one of the third
pair of rotors has a number of twisted lobes that equals a number
of twisted lobes of the other of the third pair of rotors.
6. A system for generating mechanical work via a closed-loop
Rankine cycle, the system comprising: a. a power plant that
produces a waste heat stream, wherein the power plant has a waste
heat outlet through which the waste heat stream exits; b. at least
one heat exchanger in fluid communication with the waste heat
stream, the heat exchanger being configured to heat a working
fluid; c. a multi-stage fluid expansion device configured to
generate mechanical work at an output device from the working
fluid, the expansion device having a housing within which a first
stage and a second stage are disposed, the first stage being
configured to expand the working fluid, the second stage being
configured to receive the working fluid from the first stage and to
expand the working fluid; d. a condenser constructed and arranged
to condense the working fluid; e. a pump constructed and arranged
to pump the condensed working fluid to the at least one heat
exchanger; and f. a first working fluid bypass line arranged to
bypass at least a portion of the working fluid around the first
stage and to the second stage, the first working fluid bypass line
including a first control valve.
7. The system for generating mechanical work of claim 6, wherein
the multi-stage fluid expansion device housing further includes: a.
a third stage disposed within the housing that is configured to
receive the working fluid from the second stage and to expand the
working; b. a second working fluid bypass line arranged to bypass
at least a portion of the working fluid around the second stage and
to the third stage, the second working fluid bypass line including
a second control valve.
8. The system for generating mechanical work of claim 7, wherein:
a. The housing defines an internal working fluid pathway within
which the working fluid can pass internally from the first stage to
the second stage and from the second stage to the third stage.
9. The system for generating mechanical work of claim 7, further
comprising: a. a variable speed drive for controlling the
rotational speed of the fluid expansion device first, second, and
third pairs of rotors, the variable speed drive including a motor
connected to the power output device.
10. The system for generating mechanical work of claim 7, further
comprising: a. a housing within which the first, second, and third
pairs of rotors is disposed, wherein the second outlet and third
inlet are joined within the housing to form a continuous internal
working fluid passageway extending between the second inlet and the
third outlet, wherein the first bypass line includes a bypass
connection tube extending through the housing and into the
passageway, wherein the second bypass line includes a bypass
connection tube extending through the housing and into the
passageway
11. The multi-stage volumetric fluid expansion device of claim 8,
wherein: a. the first pair of rotors have twisted non-contacting
lobes, wherein one of the first pair of rotors has a number of
twisted lobes that equals a number of twisted lobes of the other of
the first pair of rotors; b. the second pair of rotors have twisted
non-contacting lobes, wherein one of the second pair of rotors has
a number of twisted lobes that equals a number of twisted lobes of
the other of the second pair of rotors; and c. the third pair of
rotors have twisted non-contacting lobes, wherein one of the third
pair of rotors has a number of twisted lobes that equals a number
of twisted lobes of the other of the third pair of rotors.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Continuation of PCT/US2015/044529,
filed on Aug. 10, 2015, which claims benefit of U.S. Patent
Application Ser. No. 62/043,082, filed on Aug. 28, 2014, and which
applications are incorporated herein by reference. To the extent
appropriate, a claim of priority is made to each of the above
disclosed applications.
TECHNICAL FIELD
[0003] This present disclosure relates to volumetric fluid
expansion devices that convert waste energy from a power plant to
useful work for the purposes of increasing power plant
efficiency.
BACKGROUND
[0004] Waste heat energy is necessarily produced in many processes
that generate energy or convert energy into useful work, such as a
power plant. Typically, such waste heat energy is released into the
ambient environment. In one application, waste heat energy is
generated from an internal combustion engine. Exhaust gases from
the engine have a high temperature and pressure and are typically
discharged into the ambient environment without any energy recovery
process. Alternatively, some approaches have been introduced to
recover waste energy and re-use the recovered energy in the same
process or in separate processes. However, there is still demand
for enhancing the efficiency of energy recovery.
SUMMARY
[0005] In one aspect of the present teachings, a multi-stage
volumetric fluid expansion device is provided to generate useful
work by expanding a working fluid. In one application, the
volumetric fluid expansion device can be utilized to recover waste
energy from a power plant, such as waste heat energy from a fuel
cell or an internal combustion engine. The power plant may be
provided in a vehicle or may be provided in a stationary
application, such as a generator application.
[0006] The multi-stage volumetric fluid expansion device may be
provided as part of a system for generating mechanical work via a
closed-loop Rankine cycle. Such a system may also include a power
plant that produces a waste heat stream, wherein the power plant
has a waste heat outlet through which the waste heat stream exits
and at least one heat exchanger in fluid communication with the
waste heat stream. In operation, the heat exchanger heats the
working fluid. The multi-stage fluid expansion device can be
configured to generate mechanical work at an output device from the
working fluid and be provided with a housing within which a first
stage, a second stage, and a third stage are disposed. The first,
second, and third stages can be configured to sequentially expand
the working fluid and product mechanical work at the output device.
A condenser may also be provided to partially or fully condense the
working fluid while a pump may be provided to pump the condensed
working fluid back to the heat exchanger.
[0007] The volumetric fluid expansion device can be provided with a
first working fluid bypass line extending between the first inlet
and first outlet of the first fluid expansion stage to allow
working fluid to bypass the first stage. In one aspect, the first
working fluid bypass line can include a first control valve. The
volumetric fluid expansion device can be provided with a second
working fluid bypass line extending between the first inlet and
first outlet of the second fluid expansion stage to allow working
fluid to bypass the first stage. In one aspect, the second working
fluid bypass line can include a second control valve. A bypass line
to bypass working fluid around the third stage may also be
provided.
[0008] A variable speed drive for controlling the rotational speed
of the fluid expansion device first, second, and third pairs of
rotors may also be provided. In one aspect, the variable speed
drive includes a motor connected to the power output device of the
fluid expansion device.
[0009] The multi-stage expansion device first stage may include a
first pair of non-contacting rotors disposed between a first inlet
and a first outlet while the second stage may include a second pair
of non-contacting rotors disposed between a second inlet and a
second outlet. The third fluid expansion stage may include a third
pair of non-contacting rotors disposed between a third inlet and a
third outlet. In one aspect, the power output device is rotated by
the first, second, and second third of rotors. In one example, the
second outlet and third inlet are joined within the housing to form
a continuous working fluid passageway extending between the second
inlet and the third outlet. In one example, the first outlet and
the second inlet are joined within the housing to form a continuous
working fluid passageway extending between the first inlet and the
third outlet.
[0010] In one aspect, the output device is mechanically coupled to
the third stage, the second stage is mechanically coupled to the
third stage, and the first stage is mechanically coupled to the
second stage such that power developed by each of the first,
second, and third stages is transmitted to the power output device.
In one example, the first pair of rotors has twisted non-contacting
lobes, wherein one of the first pair of rotors has a number of
twisted lobes that equals a number of twisted lobes of the other of
the first pair of rotors. The second and third pairs of rotors may
be similarly configured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-sectional side view of a vehicle having a
volumetric fluid expansion device having features that are examples
of aspects in accordance with the principles of the present
teachings.
[0012] FIG. 2 is a schematic view of a first example of the
volumetric fluid expansion device shown in FIG. 1.
[0013] FIG. 3 is a perspective view of a rotor suitable for use in
the volumetric fluid expansion device shown in FIG. 1.
[0014] FIG. 4 is a schematic side view of a stage inlet of the
fluid expansion device shown in FIG. 1.
[0015] FIG. 5 is a perspective view of an example fluid expansion
device having features that are examples of aspects in accordance
with the principles of the present disclosure.
[0016] FIG. 6 is a perspective view of the fluid expansion device
shown in FIG. 5.
[0017] FIG. 7 is a perspective view of the fluid expansion device
shown in FIG. 5.
[0018] FIG. 8 is a cut-away partial perspective view of the fluid
expansion device shown in FIG. 5.
[0019] FIG. 9 is a cut-away partial perspective view of the fluid
expansion device shown in FIG. 5.
[0020] FIG. 10 is a perspective view of the drivetrain of the fluid
expansion device shown in FIG. 5.
DETAILED DESCRIPTION
[0021] Various examples 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 examples 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 examples for the appended claims. Referring to the
drawings wherein like reference numbers correspond to like or
similar components throughout the several figures.
[0022] Modern demands for fuel efficient vehicles and power plants
have led to development of hybrid power-generation and propulsion
systems. Generally, such systems combine a power-plant, such as an
internal combustion engine or a fuel cell, and an electric motor to
drive the vehicle. Each of the internal combustion engine and fuel
cell emits high temperature exhaust as a byproduct of the
power-generation cycle employed therein. The high temperature
exhaust constitutes energy that is lost from the power-generation
cycle, which, if recaptured, could be employed to improve
efficiency of the cycle, and, therefore, of the propulsion system
employing the same. Improvements in other applications are also
desired, for example in marine agricultural and industries. Another
example is stationary generator sets.
[0023] Referring to FIG. 1, a vehicle 10 is shown having wheels 12
for movement along an appropriate surface, such as a roadway. The
vehicle 10 includes a power-generation system 14. The system 14 can
include a power-plant 16 employing a power-generation cycle. The
power-plant 16 can use a specified amount of oxygen, which may be
part of a stream of intake air, to generate power. The power-plant
16 can also generate waste heat such in the form of a
high-temperature exhaust gas in exhaust line 17 a byproduct of the
power-generation cycle. In one example, the power-plant 16 can be
an internal combustion (IC) engine, such as a spark-ignition or
compression-ignition type which combusts a mixture of fuel and air
to generate power. In one example, the power-plant 16 may be a fuel
cell which converts chemical energy from a fuel into electricity
through a chemical reaction with oxygen or another oxidizing
agent.
[0024] The vehicle 10 may also include an energy recovery device,
for example volumetric fluid expansion device 20, which recovers
waste heat from the power-plant 16 to improve the efficiency of the
power-plant 16. In one aspect, the volumetric fluid expansion
device 20 can be a multi-stage fluid expansion device 20. A more
detailed description of a multi-stage fluid expansion device 20 is
provided in Patent Cooperation Treaty (PCT) International
Application Publication Number WO 2014/117159 entitled MULTI-STAGE
VOLUMETRIC FLUID EXPANSION DEVICE. WO 2014/117159 is hereby
incorporated herein by reference in its entirety.
[0025] In one example, and as shown in FIG. 1, an organic Rankine
cycle (ORC) can be used to power the fluid expansion device 20. In
such an example, a piping system 1000 including a heat exchanger 18
can be provided that transfers heat from the exhaust gas line 17 to
a working fluid 12 that can then be delivered to the volumetric
fluid expansion device 20. The working fluid 12 may be a solvent or
combination of solvents, such as ethanol, n-pentane, toluene,
and/or water. A condenser 19 can also be provided which creates a
low pressure zone for the working fluid 12 and thereby provides a
location for the working fluid 12 to condense. Once condensed, the
working fluid 12 can be delivered to the heat exchanger 18 via a
pump 17. A more detailed description of an ORC system being
utilized to drive an energy recovery device 20 is provided in
Patent Cooperation Treaty (PCT) International Application
Publication Number WO 2013/130774 entitled VOLUMETRIC ENERGY
RECOVERY DEVICE AND SYSTEMS. WO 2013/130774 is hereby incorporated
herein by reference in its entirety. Additional ORC systems are
disclosed in this application, as well as in PCT Application
Publication WO 2014/117152 entitled VOLUMETRIC ENERGY RECOVERY
SYSTEM WITH THREE STAGE EXPANSION, the entirety of which is
incorporated by reference herein. The volumetric fluid expansion
device 20 may also be utilized in a direct exhaust gas heat
recovery process wherein the exhaust gas is the working fluid 12,
as disclosed in Patent Cooperation Treaty (PCT) Application
Publication WO/2014/107407 entitled EXHAUST GAS ENERGY RECOVERY
SYSTEM, the entirety of which is herein incorporated by reference
in its entirety.
Housing Configurations
[0026] Referring to FIG. 2, a schematic representation of an
example of a multi-stage volumetric fluid expansion device 20 in
accordance with the present teachings is shown. FIGS. 5-10 show a
physical example of the volumetric fluid expansion device 20. As
presented, the multi-stage volumetric fluid expansion device 20 can
include a first stage 20-1, a second stage 20-2, and a third stage
20-3. It should be understood that although three stages is shown,
the device could be provided with fewer stages, such as two stages,
or more stages, such as four, five, six, or more stages. In
generalized terms, each of the stages 20-1, 20-2, 20-3 is or can be
placed in fluid communication with the other such that the working
fluid 12 passes sequentially through the stages 20-1, 20-2, 20-3
whereby energy from the fluid is transferred to useful work. The
fluid expansion device 20 may also include a power output device
400 configured to transfer useful work from the stages 20-1, 20-2,
20-3 to a power input location of the vehicle 10 or power plant
16.
[0027] As shown, the first stage 20-1 can include a main housing
102 that defines a first working fluid passageway 106 extending
between a first inlet 108 and a first outlet 110. Similarly, the
second stage 20-2 can include a main housing 202 defining a working
fluid passageway 206 extending between a second inlet 208 and a
second outlet 210 while the third stage 20-3 can have a main
housing 302 defining a working fluid passageway 306 extending
between a third inlet 308 and a third outlet 306. The fluid
expansion device 20 can also be provided with compartments 150,
152, 154, and 156 to house bearings, timing gears, and/or step
gears, as disclosed in PCT Application Publication WO 2014/117159.
In one example, the compartments 152 and 154 can be configured to
provide a boundary between the working fluid pathways 106/206 and
206/306 so as to prevent the working fluid 12 from bypassing
internally from the first stage 20-1 to the second stage 20-2 and
from the second stage 20-2 to the third stage 20-3 outside of the
defined working fluid pathways 106, 206, 306.
[0028] Disposed within each of the working fluid passageways 106,
206, 306 can be a pair of meshed rotors 130/132, 230/232, and
330/332, respectively. Each pair of meshed rotors 130/132, 230/232,
and 330/332 can be configured such that the rotors are overlapping
and rotate synchronously in opposite directions. As the working
fluid 12 passes through the inlet 108, 208, 308, across the meshed
rotors 130/132, 230/232, 330/332, and to the respective outlet 110,
210, 310, the working fluid 12 undergoes a pressure drop which
imparts rotational movement onto the rotors, thus creating
mechanical work that can be input back into the power plant 16.
Accordingly, each inlet port 108, 208, 308 can be configured to
admit the working fluid 12 at an entering pressure whereas the
corresponding outlet port 110, 210, 310 can be configured to
discharge the working fluid 12 at a leaving pressure lower than the
entering pressure. In such a configuration, the working fluid 12
enters inlet 108 at a first pressure and leaves outlet 110 and
enters inlet 208 at a second pressure lower than the first. The
working fluid can then exit outlet 210 and enter inlet 308 at a
third pressure lower than the second and can subsequently exit
outlet 310 at a fourth pressure lower than the third. In one
example, the pressure drop from the first inlet 108 to the third
outlet 310 can be about 10 bar wherein the pressure drop between
the first inlet and the first outlet can be about 5 bar, the
pressure drop between the second inlet 208 and the second outlet
210 can be about 3 bar, and the pressure drop between the third
inlet 308 and the third outlet 310 can be about 2 bar.
[0029] With reference to the example shown in FIG. 2, the housings
102, 202, 302 can be configured such that the first outlet 10 and
the second inlet 208 can be formed as a common internal working
fluid passageway, as can be the second outlet 210 and the third
inlet 208. In this configuration, as the working fluid 12 enters
the first stage 20-1, at the first inlet 108, the working fluid 12
stays entirely internal to the fluid expansion device 20 until
reaching the third outlet 310. By creating an entirely internal
working fluid passageway 106/206/306 between the first inlet 108
and the third outlet 310, the potential leak paths for working
fluid are even further reduced, which in turn also reduces pressure
drop losses and packaging complexity.
Bypass Configurations
[0030] Still referring to FIG. 2, the volumetric energy recovery
device can be provided with one or more bypass lines to allow some
or all of the working fluid 12 to bypass one or more of the
expander stages 20-1, 20-2, 20-3. Bypassing stages of the expansion
device 20 enables the operation of the expansion device 20 to be
optimized in light of actual system operating conditions. In one
example, bypassing can be effective during transient operating
conditions to accommodate the time lag between system activation
and the working fluid 12 actually being sufficiently heated (e.g.
superheated) in the heat exchanger 18. The bypassing of stages also
allows for the same expander 20 to be operated with different
working fluids 12. In some applications, the internal gearing
ratios between the stages 20-1, 20-2, 20-3 is a function of the
expansion ratio of a particular working fluid to be used in the
expander 20. As different working fluids 12 can have different
expansion ratios, an expander 20 may run optimally for one working
fluid, but not another. For example, if water were to be used as a
working fluid in an expansion device 20 that is optimized for an
ethanol based working fluid, the internal gearing could be too low
resulting in a first stage displacement that is too small for the
expansion device 20 to be operated properly. In such an instance,
the pressure drop across the first and second expander stages 20-1
and 20-1 could be high enough such that no pressure is available
for the third stage 20-3. Where the third stage 20-3 is designed as
the largest displacement size and is responsible for the majority
of the power generated by the expansion device 20, such an
operating condition would drastically decrease the overall
performance of the expansion device 20. However, if the first
and/or second stages are bypassed such that it is ensured that the
third stage 20-1 receives the working fluid 12 at an optimal
pressure, the power output of the third stage 20-3 can be maximized
to an extent that much of the otherwise lost power output can be
realized at the expander output device 400.
[0031] In one example, a first bypass line 51 can be provided that
places the first stage inlet 108 in fluid communication with the
first stage outlet 110. Likewise, a second bypass line 53 can be
provided that places the second stage inlet 208 (or first stage
outlet 110) in fluid communication with the second stage outlet 210
(or the third stage inlet 308). In one example, a bypass line 55 is
provided that places the third stage inlet 308 (or second stage
outlet 210) in fluid communication with the third stage outlet 310.
Accordingly, the first bypass line 51 allows for the working fluid
to bypass around the first stage 20-1, the second bypass line 53
allows for the working fluid to bypass around the second stage
20-2, and the third bypass line 55 allows for the working fluid to
bypass around the second stage 20-3.
[0032] Referring to FIGS. 5-9, it can be seen that a bypass line
connection tube 60 can be provided at the inlet of the second stage
20-2 and that a bypass line connection tube 62 can be provided at
the inlet of the third stage 20-3. The bypass line connection tube
60 can be configured to connect to bypass lines 51 and/or 53 via a
mechanical connector, for example via a SWAGELOK.RTM. type tubing
connector. Similarly, the bypass line connection tube 62 can be
configured to connect to bypass line 55 via a mechanical connector,
for example via a SWAGELOK.RTM. type tubing connector. As shown,
the bypass line connection tube 60 extends through the second stage
housing 202 and into fluid passageway 206 while the bypass line
connection tube 62 extends through the third stage housing 302 and
into fluid passageway 306. In one example, the angle of the bypass
line connection tubes 60, 62 with respect to the housing is
arranged to optimally introduce the bypassed working fluid 12 into
the respective rotors.
[0033] In one aspect, desired flow through the bypass lines 51, 53,
55 can be controlled through the operation of one or more control
valves. For example, bypass line 51 can be provided with a control
valve 52, bypass line 53 can be provided with a control valve 54,
and bypass line 55 can be provided with a control valve 56. It
should be understood that more or fewer valves or different types
of valves may be provided. For example, a three way valve could be
utilized in lieu of the two valves shown for the first and second
bypass lines 51, 53. In one example, valves 52, 54, and 56 are
automatically controlled ball-type control valves.
[0034] In the exemplary configuration shown, the bypass lines and
valves do not prevent flow through a particular stage 20-1, 20-2,
20-3, but rather provide a lower pressure drop pathway around the
bypassed stage while allowing flow through each stage to be open.
Accordingly, when flow is allowed through a bypass line, some of
the working fluid 12 will still travel through the expander stage
being bypassed although at a much lower volume and pressure drop.
The degree to which the working fluid 12 passes through the bypass
line instead of the expander stage can be controlled by the
valve(s) itself and by the size of the bypass line. Alternatively,
the bypass lines and valves can be configured to actively block
flow through the stage being bypassed such that all of the working
fluid 12 is directed around the stage being bypassed.
[0035] In the configuration shown, the bypass valves 52, 54, 56 can
be opened and closed (and/or modulated) to bypass any single stage
or combination of stages to achieve a desired bypass result. For
example, where the first stage bypass valve 52 is open and the
second and third stage bypass valves 54, 56 are closed, at least
some of the working fluid 12 will be bypassed around the first
stage 20-1, but not bypassed around the second and third stages
20-2, 20-3. Where the first and second bypass valves 52, 54 are
open and the third stage bypass valve 56 is closed, at least some
of the working fluid 12 will be bypassed around both the first and
second stages 20-1, 20-2, but not bypassed around the third stage
20-3. The bypass valves 52, 54, 56 can be further operated to
bypass only the second stage 20-2, to bypass only the third stage
20-3, to bypass the second and third stages 20-2, 20-3, and to
bypass the first and third stages 20-1, 20-3.
Variable Speed Drive System
[0036] The expansion device 20 can also be provided with a variable
speed drive 58 to control the rotational speed of the expansion
device rotors via an output shaft, for example through the power
output device 400. In one aspect, the variable speed drive 58
includes a motor and a controller to vary the speed of the motor.
The variable speed drive 58 can be further configured to act as a
generator when the power output of the fluid expansion device 20 is
sufficient. The variable speed drive 58 can be used to replace the
connection between the power output device 400 and the power plant
16 which typically fixes the speed ratio between the power plant 16
crankshaft and the fluid expansion device 20. As such, the
utilization of the variable speed drive 58 can decouple the power
plant operating speed from the power output device 400 to result in
more efficient operation of the fluid expansion device 20. As with
the bypass lines and valves, the variable speed drive 58 can be
configured and operated to optimize the operation of the fluid
expansion device to accommodate different types of working fluids
and/or varying operating conditions of the system.
Electronic Control System
[0037] As described above, the expansion device 20 can be placed in
various bypass operational modes. An electronic control system can
be provided that monitors, initiates, and controls the initiation
of the various modes. In one example, an electronic controller 50
monitors various sensors and operating parameters of the expansion
device 20 and/or the vehicle power plant 16 to configure the
expansion device 20 into the most appropriate bypass mode of
operation such that power output of the expansion device 20 is
optimized.
[0038] Referring to FIG. 2, the electronic controller 50 is
schematically shown as including a processor 50A and a
non-transient storage medium or memory 50B, such as RAM, flash
drive or a hard drive. Memory 50B is for storing executable code,
the operating parameters, and potential inputs from an operator
interface, while processor 50A is for executing the code.
Electronic controller 50 is configured to be connected to a number
of inputs and outputs that may be used for implementing the bypass
operational modes. For example, the electronic controller 50 can
receive information from a vehicle control area network (CAN) bus
56 and information from sensors associated with the expansion
device 20 (e.g. mass flow rate sensors, pressure sensors,
temperature sensors, etc.). One skilled in the art will understand
that many other inputs are possible.
[0039] Examples of outputs from the controller 50 are outputs for
the operation of the control valves 52, 54, and 56 and for the
operation of the variable speed drive 58. Other outputs are
possible as well. In one embodiment, the electronic controller 50
is configured to include all required operational outputs for the
operation of the fluid expansion device 20.
[0040] The electronic controller 50 may also include a number of
maps or algorithms to correlate the inputs and outputs of the
controller 50. For example, the controller 50 may include an
algorithm to control the position of the valves 52, 54, and 56
based on the inlet conditions from the ORC system engine speed, and
expansion device speed to achieve a desired mass flow rate through
the expansion device stages 20-1, 20-2, and 20. The electronic
controller 50 may also store a number of predefined and/or
configurable parameters and offsets for determining when each of
the modes is to be initiated and/or terminated. As used herein, the
term "configurable" refers to a parameter or offset value that can
either be selected in the controller (i.e. via a dipswitch) or that
can be adjusted within the controller.
Rotor Configurations
[0041] In one example, each of the rotors 130, 132, 230, 232, 330,
and 332 (collectively referred to as rotors 30, 32) can be attached
to a respective rotor shaft 138, 140, 238, 240, 338, and 340
(collectively referred to as rotor shafts 38, 40). The rotor shafts
38, 40 can be rigidly connected to the rotors 30, 32 and thus
rotate as the rotors are rotated. The rotor shafts 138, 238, 338
can be individual separate shafts rotationally connected through
gear sets (e.g. step-up gear sets, step-down gear sets, one-to-one
gear sets, etc.) or form part of a common shaft 38. Likewise, rotor
shafts 140, 240, and 340 can be individual separate shafts or form
part of a common shaft 38.
[0042] Each of the rotors 130/132, 230/232, 330/332, collectively
referred to as rotors 30, 32 in this section and with reference to
FIGS. 3-4, can provided with a plurality of lobes. As shown in FIG.
3, each rotor 30, 32 can be provided with three lobes, 30-1, 30-2,
30-3 in the case of the rotor 30, and 32-1, 32-2, 32-3 in the case
of the rotor 32. Although three lobes are shown for each rotor 30
and 32, each of the two rotors may have any number of lobes that is
equal to or greater than two. For example, PCT Publication WO
2013/130774 shows a suitable rotor having four lobes. Additionally,
the rotors of one or more of the stages 20-1, 20-2, 20-3 may have a
different number of lobes than the rotors of the other stages 20-1,
20-2, 20-3 in the device 20.
[0043] In one example, the number of lobes can be the same for each
rotor 30 and 32. This is in contrast to the construction of typical
rotary screw devices and other similarly configured rotating
equipment which have a dissimilar number of lobes (e.g. a male
rotor with "n" lobes and a female rotor with "n+1" lobes).
Furthermore, one of the distinguishing features of the expansion
device 20 is that the rotors 30 and 32 are identical, wherein the
rotors 30, 32 are oppositely arranged so that, as viewed from one
axial end, the lobes of one rotor are twisted clockwise while the
lobes of the meshing rotor are twisted counter-clockwise.
Accordingly, when one lobe of the rotor 30, such as the lobe 30-1
is leading with respect to the inlet port 24, a lobe of the rotor
32, such as the lobe 30-2, is trailing with respect to the inlet
port 24, and, therefore with respect to a stream of the
high-pressure fluid 12.
[0044] As previously mentioned, the first and second rotors 30 and
32 can be interleaved and continuously meshed for unitary rotation
with each other. In one example, the lobes of each rotor 30, 32 are
twisted or helically disposed along the length L of the rotors 30,
32. In one example, each rotor 30, 32 has straight lobes along the
length L of the rotors 30, 32. Upon rotation of the rotors 30, 32,
the lobes at least partially seal the fluid 12 against an interior
side of the housing at which point expansion of the fluid 12 only
occurs to the extent allowed by leakage which represents and
inefficiency in the system. In contrast to some expansion devices
that change the volume of the fluid when the fluid is sealed, the
volume defined between the lobes and the interior side 33 of the
housing is constant as the fluid 12 traverses the length of the
rotors 30, 32. Accordingly, the expansion device 20 can be referred
to as a "volumetric device" as the sealed or partially sealed fluid
volume does not change wherein the working fluid 12 is generally
not reduced or compressed.
[0045] In operation, the rotor shafts 38, 40 can be rotated by the
working fluid 12 as the fluid undergoes expansion from the higher
first pressure working fluid 12 to the lower second pressure
working fluid 12. Accordingly, the shafts 38, 40 are configured to
capture the work or power generated by the expansion device 20
during the expansion of the fluid 12 that takes place between the
inlet port 108, 208, 308 and the respective outlet port 110, 210,
310. As discussed previously, the work is transferred from the
shafts 38, 40 as output torque from the expansion device 20 via
output device 400.
[0046] In one aspect of the geometry of the expansion device 20,
each of the rotor lobes 30-1 to 30-3 and 32-1 to 32-3 has a lobe
geometry in which the twist of each of the first and second rotors
30 and 32 is constant along their substantially matching length L.
Alternatively, the lobes 130, 132, 230, 232, 330, 332 can be
provided without a twist although a drop in efficiency would be
expected to occur. In one example, lobes 130, 132 are provided as
straight lobes while lobes 230, 232, 330, 332 are provided as
twisted lobes. In one example, the length L of all rotors 130, 132,
230, 232, 330, 332 is the same. In one example, the length L of the
rotors 130, 132 is less than a length L of the rotors 230, 232,
which is in turn less than a Length L of the rotors 330, 332.
[0047] The various examples described above are provided by way of
illustration only and should not be construed to limit the claims
attached hereto. Those skilled in the art will readily recognize
various modifications and changes that may be made without
following the examples and applications illustrated and described
herein, and without departing from the true spirit and scope of the
disclosure.
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