U.S. patent application number 13/683175 was filed with the patent office on 2013-05-30 for system and method for compression of fluids.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is General Electric Company. Invention is credited to Charles Erklin Seeley, Sunilkumar Onkarnath Soni, Bhaskar Tamma.
Application Number | 20130133347 13/683175 |
Document ID | / |
Family ID | 48465550 |
Filed Date | 2013-05-30 |
United States Patent
Application |
20130133347 |
Kind Code |
A1 |
Soni; Sunilkumar Onkarnath ;
et al. |
May 30, 2013 |
SYSTEM AND METHOD FOR COMPRESSION OF FLUIDS
Abstract
A fluid compressor for compressing fluids and a method for
operating the same are provided. The fluid compressor includes a
compression chamber with an inlet for the fluid and an outlet for
compressed fluid. The fluid compressor further includes a piston
disposed within the compression chamber. The fluid compressor
includes a driving system that includes piezoelectric actuator
configured to cause displacement of the piston in the compression
chamber. The driving system further includes an amplifying element
that is coupled to the piezoelectric actuator in the direction of
the movement of the piston to enhance the displacement of the
piston caused by the piezoelectric actuator. One end of the
amplifying element is fixed to a base of the fluid compressor and
the piezoelectric actuator is disposed between the amplifying
element and the piston.
Inventors: |
Soni; Sunilkumar Onkarnath;
(Albany, NY) ; Tamma; Bhaskar; (Bangalore, IN)
; Seeley; Charles Erklin; (Niskayuna, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company; |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
48465550 |
Appl. No.: |
13/683175 |
Filed: |
November 21, 2012 |
Current U.S.
Class: |
62/126 ; 417/32;
417/415; 417/44.2; 62/125; 62/426; 62/498 |
Current CPC
Class: |
F04B 17/03 20130101;
F25B 49/022 20130101; F04B 2201/0206 20130101; F25B 1/02 20130101;
F04B 2201/0207 20130101; F04B 35/04 20130101; F04B 17/003 20130101;
F04B 49/065 20130101; F25B 2400/073 20130101 |
Class at
Publication: |
62/126 ; 62/498;
62/426; 62/125; 417/415; 417/32; 417/44.2 |
International
Class: |
F04B 17/03 20060101
F04B017/03; F25B 49/02 20060101 F25B049/02; F25B 1/02 20060101
F25B001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 24, 2011 |
IN |
4061/CHE/2011 |
Claims
1. A system for controlling temperature of an enclosed space, the
system comprising: a fluid compressor to compress a coolant fluid,
wherein the fluid compressor comprises: a compression chamber
having an inlet for the coolant fluid and an outlet for the
compressed coolant fluid; a piston disposed within the compression
chamber; a driving system comprising: a piezoelectric actuator
coupled to the piston, configured to cause lateral displacement of
the piston in the compression chamber in response to an excitation
signal; and an amplifying element operatively coupled to the
piezoelectric actuator in the direction of the movement of the
piston, the amplifying element being configured to enhance the
displacement of the piston caused by the piezoelectric actuator,
one end of the amplifying element being fixed to a base of the
fluid compressor, the piezoelectric actuator being disposed between
the amplifying element and the piston; a condenser operatively
coupled to the fluid compressor, to remove the heat of the
compressed high temperature coolant fluid; an expansion valve to
reduce pressure of the compressed coolant fluid entering from the
condenser and further reduce temperature of the compressed high
temperature coolant fluid; and an evaporator to control temperature
of the enclosed space by drawing heat from the enclosed space
through the coolant fluid from the expansion valve.
2. The system as recited in claim 1, further comprising a fan that
blows air from the enclosed space across the cooled coolant fluid
in the evaporator.
3. The system as recited in claim 1, wherein the condenser
comprises coiled tubes to carry the compressed coolant fluid.
4. The system as recited in claim 1, further comprising an
excitation sub-system to provide the excitation signal to the
piezoelectric actuator.
5. The system as recited in claim 4, further comprising a feedback
controller operatively coupled to the excitation sub-system to
control at least one of frequency or amplitude of the excitation
signal.
6. The system as recited in claim 5, wherein the feedback
controller comprises at least one of a pressure sensor, stroke
sensor, and temperature sensor.
7. A fluid compressor comprising: a compression chamber having an
inlet for a fluid to be compressed and an outlet for compressed
fluid; a piston disposed within the compression chamber for
compressing the fluid; a driving system for the piston comprising,
a piezoelectric actuator coupled to the piston, configured to cause
lateral displacement of the piston in the compression chamber in
response to an excitation signal, and an amplifying element
operatively coupled to the piezoelectric actuator in the direction
of the movement of the piston, the amplifying element being
configured to enhance the displacement of the piston caused by the
piezoelectric actuator, one end of the amplifying element being
fixed to a base of the fluid compressor, the piezoelectric actuator
being disposed between the amplifying element and the piston. a
feedback controller to control at least one of frequency and
amplitude of the excitation signal provided to the piezoelectric
actuator.
8. The fluid compressor as recited in claim 7, further comprising
an excitation sub-system for providing the excitation signal to the
piezoelectric actuator to cause the displacement in the
piezoelectric actuator.
9. The fluid compressor as recited in claim 7, wherein the feedback
controller comprises at least one of a pressure sensor, a stroke
sensor, and a temperature sensor.
10. The fluid compressor as recited in claim 7, further comprising
a driving system comprising a plurality of piezoelectric actuators
and a plurality of amplifying elements stacked in parallel to
displace the piston back and forth in the compressor chamber.
11. A driving system comprising: a piezoelectric actuator coupled
to a piston of a fluid compressor, configured to cause lateral
displacement of the piston in a compression chamber, and an
amplifying element operatively coupled to the piezoelectric
actuator in the direction of the movement of the piston, the
amplifying element being configured to enhance the displacement of
the piston caused by the piezoelectric actuator, one end of the
amplifying element being fixed to a base of the fluid compressor,
the piezoelectric actuator being disposed between the amplifying
element and the piston.
12. The driving system as recited in claim 11, further comprising
an excitation sub-system for providing an excitation signal to the
piezoelectric actuator to cause the displacement in the
piezoelectric actuator.
13. The driving system as recited in claim 12, further comprising a
feedback controller coupled to the excitation sub-system to control
at least one of a frequency and an amplitude of the excitation
signal provided to the piezoelectric actuator.
14. The driving system as recited in claim 13, wherein the feedback
controller comprises at least one of a pressure sensor, a stroke
sensor, and a temperature sensor.
15. The driving system as recited in claim 11, wherein the
amplifying element comprises a coiled spring that is placed in a
position parallel to a direction of movement of the piston.
16. The driving system as recited in claim 11, wherein the
amplifying element comprises a pre-buckled beam.
17. The driving system as recited in claim 11, wherein the
piezoelectric actuator comprises a stack actuator.
18. The driving system as recited in claim 11, wherein the
piezoelectric actuator comprises an amplified piezoelectric
actuator.
19. The driving system as recited in claim 11, further comprising a
plurality of piezoelectric actuators and a plurality of amplifying
elements stacked in parallel to displace the piston back and forth
in the compressor chamber.
20. A method of operating a fluid compressor, the method
comprising: monitoring at least one of fluid pressure and fluid
temperature in a compression chamber of the fluid compressor,
comprising a piston that is laterally displaced back and forth in
the compression chamber by a driving system, wherein the driving
system comprises: a piezoelectric actuator coupled to the piston,
and an amplifying element operatively coupled to the piezoelectric
actuator in the direction of the movement of the piston, the
amplifying element being configured to enhance the displacement of
the piston caused by the piezoelectric actuator, one end of the
amplifying element being fixed to a base of the fluid compressor,
the piezoelectric actuator being disposed between the amplifying
element and the piston; comparing at least one of monitored fluid
pressure and fluid temperature with a reference value; and
providing an excitation signal to the piezoelectric actuator based
on the comparison result.
21. The method as recited in claim 20, further comprising disposing
a plurality of piezoelectric actuators with a plurality of
amplifying elements, in a position parallel to the piston of the
fluid compressor.
Description
BACKGROUND OF THE INVENTION
[0001] Embodiments of the present invention are related generally
to the field of cooling systems and, more particularly, to a system
and method for compression of fluids.
[0002] Compressors are typically used in systems and appliances
that require fluids to be compressed and obtain high pressure. Such
a need is felt in systems that follow a thermodynamic refrigeration
cycle, for example, but not limited to, refrigerators, air
conditioners, automotive cooling systems, and power plant cooling
systems. Compressors are employed in such systems to compress the
coolant and maintain a desired temperature in the system.
[0003] Compressors commonly utilize a piston that compresses fluids
entering a hollow cylinder, called compression chamber, in the
compressor body. The piston moves linearly back and forth to
compress the fluid to create the high pressure fluid required to
carry out the cooling operations in the system. The piston is
displaced from an original position and kept in motion whenever the
requirement for compressing fluids arises. Several configurations
exist where the piston is set in motion to ensure fluids are
compressed.
[0004] In an exemplary configuration, piezoelectric materials have
been used as actuators to initiate displacement of pistons in the
compressors. The piezoelectric material is provided with an
excitation signal that causes the material to expand or contract.
Generally, the piezoelectric material is coupled with the piston in
such a way that the piston is displaced back and forth in the
compression chamber, when the piezoelectric material experiences a
change in shape and/or form.
[0005] Although the piezoelectric material causes displacement that
may be desirable to compress fluids, the amount of displacement is
dependent on several parameters including an excitation signal
provided to the material. For high pressure requirements in a
compression cycle in systems that require intensive cooling at a
fast rate, a significant amount of energy is consumed by the
excitation signal to be provided to the piezoelectric material.
Moreover, piezoelectric material alone, even when provided with
sufficient excitation signal, cannot provide both force and
displacement to achieve the high pressure requirements at a fast
rate.
[0006] Accordingly, there is a need for an improved system and
method that provides for energy efficiency in driving the piston in
the compression chamber of the fluid compressor.
BRIEF DESCRIPTION OF THE INVENTION
[0007] In accordance with an embodiment of the invention, a system
for controlling temperature of an enclosed space is provided. The
system includes a fluid compressor to increase pressure of a
coolant fluid. The fluid compressor includes a compression chamber
having an inlet for the coolant fluid and an outlet for the
compressed coolant fluid. Further, the fluid compressor includes a
piston disposed within the compression chamber. The piston within
the compression chamber is displaced using a driving system. The
driving system includes a piezoelectric actuator coupled to the
piston to cause lateral displacement of the piston in the
compression chamber in response to an excitation signal. The
driving system also includes an amplifying element operatively
coupled to the piezoelectric actuator in the direction of the
movement of the piston to enhance the displacement of the piston
caused by the piezoelectric actuator. One end of the amplifying
element is fixed to a base of the fluid compressor and the
piezoelectric actuator is disposed between the amplifying element
and the piston. Furthermore, the system to control temperature
includes a condenser operatively coupled to the fluid compressor,
to remove a portion of the heat contained in the compressed high
temperature coolant fluid. The system also includes an expansion
valve to reduce pressure of the compressed coolant fluid entering
from the condenser and further reduce the temperature of the
compressed coolant fluid. An evaporator to control temperature of
the enclosed space by drawing heat from the enclosed space through
the coolant fluid from the expansion valve is also included in the
system.
[0008] In accordance with another embodiment of the invention, a
system to compress fluids is provided. The system includes a
driving system to displace a piston back and forth in a compression
chamber. The driving system includes a piezoelectric actuator that
causes a displacement of the piston in the compression chamber. The
piston is disposed on top of the piezoelectric actuator. Further,
the driving system includes an amplifying element that is coupled
to the piezoelectric actuator to enhance the displacement caused by
the piezoelectric actuator. The amplifying element is disposed in
such a way that the piezoelectric actuator is placed on a top end
of the amplifying element and an opposite end of the amplifying
element is mechanically coupled with a base of the fluid
compressor.
[0009] In accordance with another embodiment of the invention, a
method for compressing fluids in a fluid compressor is provided.
The method for compressing fluid includes displacing a
piezoelectric actuator from its initial position with an excitation
signal. The piezoelectric actuator is disposed below a piston of
the fluid compressor that is configured to displace back and forth
in a compression chamber of the fluid compressor. Further, the
method includes amplifying the displacement of the piston by a
degree of at least seven using an amplifying element. The
amplifying element is disposed in such a way that the piezoelectric
actuator is disposed on a top end of the amplifying element and an
opposite end of the amplifying element is mechanically coupled with
a base of the fluid compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The features and advantages of the present invention will
become apparent from the following detailed description of the
invention when read with the accompanying drawings in which:
[0011] FIG. 1 is a schematic illustration of a system to control
temperature of an enclosed space embodying certain aspects of the
present invention;
[0012] FIG. 2 is a block diagram representation of the fluid
compressor embodying aspects of the present invention;
[0013] FIG. 3 is a flow chart representing an exemplary method of
operating a fluid compressor according to an embodiment of the
present invention;
[0014] FIG. 4 is a block diagram representation of a feedback
controller to control an excitation signal provided to a
piezoelectric actuator according to one embodiment of the present
invention;
[0015] FIG. 5 illustrates graph comparing performances of one
embodiment of the present invention and another configuration of a
fluid compressor, with respect to frequency of the fluid compressor
as a function of amplifying element stiffness; and
[0016] FIG. 6 illustrates a graph comparing performance of an
embodiment of the present invention and another configuration of a
fluid compressor, with respect to stroke pressure as a function of
amplifying element stiffness.
DETAILED DESCRIPTION OF THE INVENTION
[0017] While embodiments of the present invention have been shown
and described herein, such embodiments are provided by way of
example only. Numerous variations, changes and substitutions will
occur to those of skill in the art without departing from the
invention herein. Accordingly, it is intended that the invention be
limited only by the spirit and scope of the appended claims.
[0018] As discussed in detail below, embodiments of the invention
include a driving system for compression of fluids. Aspects of the
present technique reduce energy consumption of compressors used to
compress fluids. The system further provides for displacement of a
piston in the fluid compressor at resonant frequency, thus
achieving compression at a fast and efficient rate. The system as
per the present technique includes a piezoelectric actuator and an
amplifying element. The piezoelectric actuator is coupled to the
piston to cause lateral displacement of the piston in the
compression chamber in response to an excitation signal. The system
further includes an amplifying element operatively coupled to the
piezoelectric actuator in the direction of the movement of the
piston to enhance the displacement of the piston caused by the
piezoelectric actuator. The amplifying element is disposed in such
a way that one end of the amplifying element is fixed to a base of
the fluid compressor and the piezoelectric actuator is disposed
between the amplifying element and the piston. The present
technique is described in greater detail in the foregoing
paragraphs with the help of accompanied drawings.
[0019] FIG. 1 is a schematic illustration of a system 100 for
controlling temperature of an enclosed space embodying aspects of
the present invention. The system 100 may be used to control
temperatures of a storage enclosure, a room or similar spaces that
require temperature control. The system 100 includes a fluid
compressor 102, a condenser 104, an expansion valve 106, an
evaporator 108, and a fan 110. The fluid compressor 102 increases
temperature of a coolant fluid by compressing the coolant fluid.
The fluid compressor 102 includes a compression chamber, a piston,
and a driving system. The driving system of the fluid compressor
102 further includes a piezoelectric actuator and an amplifying
element (not shown). The details of the fluid compressor 102 are
explained in FIG. 2. The high temperature compressed coolant fluid
flows from the fluid compressor 102 to the condenser 104. The
condenser 104 reduces temperature of the high temperature
compressed coolant fluid. Furthermore, the coolant fluid leaving
the condenser 104 enters the expansion valve 106. At the expansion
valve 106, the coolant fluid undergoes an abrupt reduction in
pressure. The reduction in pressure leads to further reduction of
temperature in the coolant fluid. The coolant fluid at reduced
temperature enters the evaporator 108 from the expansion valve 106.
The evaporator 108 is configured to draw heat from the enclosed
space using the coolant fluid at reduced temperature. Warm air 112
from the atmosphere passes through the coolant fluid in the
evaporator 108 and cold air 114 enters the enclosed space thereby
drawing heat from the enclosed space. Further, the coolant fluid
that gets heated due to extracting heat from the enclosed space is
passed to the fluid compressor 102 to continue with the cycle for
controlling temperature of the enclosed space.
[0020] In the illustrated embodiment, the system 100 includes a fan
110 that blows the warm air 112 from the atmosphere on the coolant
liquid in the evaporator 108. Further, according to certain
embodiments of the present invention, the condenser 104 includes
coiled tubes 118 to carry the compressed coolant fluid. According
to another embodiment of the present invention, the evaporator 108
also includes coiled tubes 116 to carry the coolant fluid in and
out of the enclosed space.
[0021] In another embodiment, the system 100 includes an excitation
sub-system (not shown) that provides an excitation signal to the
piezoelectric actuator in the fluid compressor 102. The system 100
also includes a feedback controller to control at least one of
frequency and amplitude of the excitation signal provided to the
piezoelectric actuator. The feedback controller includes at least
one of a pressure sensor, a temperature sensor, and a stroke sensor
that sense at least one of pressure of the coolant fluid in the
compression chamber, temperature of the coolant fluid in the
compression chamber, and a stroke of the piston within the
compression chamber respectively. The feedback controller provides
a feedback to the excitation sub-system based on the information
obtained from at least one of the sensors to provide excitation
signal that displaces the piezoelectric actuator appropriately to
achieve efficient performance.
[0022] FIG. 2 is a block diagram representation of the fluid
compressor 102 in FIG. 1. The fluid compressor 102 includes a
compression chamber 202, a piston 204, an inlet 210, an outlet 212,
and a driving system according to one embodiment of the present
invention. The driving system includes a piezoelectric actuator
206, and an amplifying element 208. The piezoelectric actuator 206
is configured to cause lateral back and forth displacement of the
piston 204 in the compression chamber 202 in response to an
excitation signal. Further, the piezoelectric actuator 206 is
operatively coupled to the amplifying element 208. The amplifying
element 208 is configured to enhance the displacement of the piston
caused by the piezoelectric actuator 206. The amplifying element
208 is disposed in the direction of the movement of the piston.
Furthermore, one end of the amplifying element 208 fixed to a base
214 of the fluid compressor 102, and the amplifying element 208 is
disposed in such a way that the piezoelectric actuator 206 is
disposed between the amplifying element 208 and the piston 204.
[0023] According to one embodiment of the present invention, the
piezoelectric actuator 206 is fixed with the amplifying element 208
using at least one of nuts, bolts, rivets, or any known adhesive
material. According to another embodiment of the present invention,
the amplifying element 208 is fixed with the base 214 of the fluid
compressor 102 using at least one of nuts, bolts, rivets, or any
known adhesive material.
[0024] In one embodiment, the fluid compressor 102 includes an
excitation sub-system configured to provide the excitation signal
to the piezoelectric actuator 206. The excitation signal provided
by the excitation sub-system is an electric signal that causes a
displacement in the piezoelectric actuators. When the excitation
signal is transmitted to the piezoelectric actuator 206, the
piezoelectric actuator 206 expands or contracts depending on a
phase of the excitation signal and causes the piston 204 to move.
The movement of the piezoelectric actuator 206 causes the
amplifying element 208 to stretch or expand. The change in shape of
the amplifying element 208 caused by the piezoelectric actuator 206
causes an enhancement in the displacement of the piston 204. The
displaced piston 204 then causes the fluid entering the compression
chamber 202 through the inlet 210 to compress. The compressed fluid
finally exits the compression chamber 202 through the outlet 212
and is supplied to a system utilizing the fluid compressor 102.
According to one embodiment of the present invention, the
displacement of the piston 204 is enhanced when the aforementioned
operation occurs at resonance. To achieve resonance, the fluid
compressor 102 has to be provided excitation signal that has a
frequency close to a resonant frequency of the fluid compressor
102. The resonant frequency of the fluid compressor 102 is
typically dependent on operating conditions, fluid pressure, and
fluid temperature. In another embodiment, the fluid compressor 102
includes a feedback controller coupled to the excitation sub-system
to ensure that the fluid compressor 102 operates in a resonant
frequency with change in the operating conditions of the fluid
compressor 102. The feedback controller is described in greater
detail in conjunction with FIG. 4 of this application.
[0025] In yet another embodiment, the amplifying element 208 is a
coiled spring. The coiled spring has a spring stiffness associated
with it, which signifies an amount of change in shape the coiled
spring can accommodate. The amount of displacement enhanced by the
amplified element 108 varies according to, among other factors, the
spring stiffness. When a coiled spring is used as an amplifying
element, it is placed in such a way that it is parallel to the
direction of the movement of the piston. According to another
embodiment of the present technique, the amplifying element 208 is
a pre-buckled beam.
[0026] The piezoelectric actuator 206, according to one embodiment
of the present technique, is a piezoelectric stack actuator.
Piezoelectric stack actuators are commercially available in the
market and are constructed using piezoelectric materials that
convert applied electrical energy to mechanical energy and cause
movement. Some examples of commercially available piezoelectric
stack actuators include, but are not limited to, Piezomechanik GmBH
manufactured PSt/150/14 . . . VS20 series piezoelectric stack
actuators, PSt/150/20 . . . VS25 series actuators, PSt/150/7 . . .
VS12 series actuators, and other similar piezoelectric stack
actuators manufactured by other actuator manufacturers like
Noliac.RTM., and CEDRAT Technologies. The piezoelectric actuator
206, according to another embodiment of the present technique, is
an amplified piezoelectric actuator that is commercially available
in the market. Examples of Amplified piezoelectric actuators
include, but are not limited to, APA.RTM., XL series manufactured
by CEDRAT Technologies. Alternatively, any piezoelectric material
that converts electrical energy to mechanical energy, like Quartz,
Topaz, Langasite, Sodium Tungstate, and that can be used to
construct a stack of piezoelectric actuator can be used in the
fluid compressor 102 as described in the present technique.
[0027] In yet another embodiment, the amplifying element 208 and
the piezoelectric actuator 206 are selected based on a set of
requirements that include, but are not limited to, degree of
compression expected, volume of fluid in the compression chamber
202 per cycle, and time taken by the fluid compressor 102 to
compress the fluid. In certain situations, a plurality of
piezoelectric actuators along with plurality of amplifying elements
can be stacked in parallel to cause displacement of the piston in
the compression chamber 202.
[0028] FIG. 3 is a flow chart representing an exemplary method for
operating a fluid compressor according to an embodiment of the
present invention. The method, as disclosed, is intended to be
practiced on the fluid compressor 102 described in FIG. 2. Elements
from FIG. 2 have been denoted with the same reference number for
the sake of clarity. The method includes, at step 302, monitoring
at least one of fluid pressure or fluid temperature in the
compression chamber 202 of the fluid compressor 102. The fluid
compressor 102, as described in conjunction with FIG. 2 includes
piston 204, and a driving system that includes a piezoelectric
actuator 206 and an amplifying element 208. The piezoelectric
actuator 206 is configured to cause lateral displacement of the
piston 204 back and forth in the compression chamber 202 by being
disposed below the piston 204. The amplifying element 208 enhances
the displacement caused by the piezoelectric actuator 206 by at
least 7 since the amplifying element 208 is disposed in such a way
that the piezoelectric actuator 206 is between the piston 204 and
the amplifying element 208. Further, one end of the amplifying
element 208 is coupled to a base 214 of the fluid compressor 102.
Further, the method includes the step 304 of comparing the
monitored value of fluid pressure or fluid temperature and a
reference value of the fluid pressure or fluid temperature,
respectively. The reference value of the fluid pressure or fluid
temperature is indicative of the fluid compressor working at a
resonant frequency. Furthermore, at step 306 an excitation signal
to the piezoelectric actuator 206 is provided based on a
comparison.
[0029] The monitored fluid pressure and fluid temperature of the
fluid in the compression chamber 202 are analyzed to determine a
change in frequency or amplitude of the excitation signal provided
to the piezoelectric actuator 206 in such a way that the piston 204
provides maximum strokes and/or the driving system operates in a
frequency that is a resonant frequency of the piezoelectric
actuator 206.
[0030] FIG. 4 is a block diagram representation of a feedback
controller 400 to control an excitation signal provided to the
piezoelectric actuator 206 according to one embodiment of the
present invention. The feedback controller 400 is used to control
the excitation signal provided by excitation sub-system 402 to the
piezoelectric actuator 206. The feedback controller 400 includes at
least one sensor 404, a filter 406, a Phase-Locked Loop (PLL)
detector 408, a voltage converter 410, and a processor 412.
[0031] An output of the sensor 404 is used to determine at least
one of fluid pressure, fluid temperature, and a piston stroke. The
output of the sensor 404 is then split in two separate signals
using a filter 406. One branch of the output of the sensor 404 is
used to compute an amplitude of the displacement of the piston 204
in the compression chamber 202 by first converting the signal to a
DC voltage signal through the converter 410. The second branch from
the sensor 404 is fed to the PLL detector 408 to determine a
frequency at which the piston 204 is being displaced in the
compression chamber 202. The processor 412 determines a change that
is required in an amplitude and/or frequency of the excitation
signal provided by the excitation sub-system 402. The processor 412
is further configured to control the excitation subsystem in such a
way that the excitation signal makes the piston 204 displace at
resonant frequency.
[0032] FIG. 5 illustrates graph comparing performances of one
embodiment of the present invention and another configuration of a
fluid compressor, with respect to frequency of the fluid compressor
as a function of amplifying element stiffness. In the graph
illustrated in FIG. 5, the Y axis 502 represents frequency in Hertz
(Hz) and the X axis 504 represents amplifying element stiffness in
Newton/meter (N/m). Furthermore, the line 506 represents results
for a configuration where a piezoelectric actuator is coupled with
a base of the compression chamber, and an amplifying element is
disposed between the piezoelectric actuator and the fluid
compressor's piston, whereas the line 508 represents results
obtained by usage of the fluid compressor as described in the
present technique. A piston of 150 grams, a piezoelectric actuator
of mass 37.7 grams and stiffness constant of 4.times.106 N/m was
used. The fluid pressure in the compression chamber was maintained
at 1.times.106 Pa. It can be seen from FIG. 5 that the frequency at
which configuration represented by line 508 operates for different
amplifying element stiffness is lesser than the frequency at which
the configuration represented by line 506 operates.
[0033] FIG. 6 illustrates a graph comparing performance of an
embodiment of the present invention and another configuration of a
fluid compressor, with respect to stroke pressure as a function of
amplifying element stiffness. In the graph illustrated in FIG. 6
the Y axis 602 represents stroke measured in meters (m) and X axis
604 represents amplifying element stiffness measured in
Newton/meter (N/m). Further, the line 606 represents results
obtained by usage of the fluid compressor as described in the
present technique, whereas the line 608 represents results for a
configuration where a piezoelectric actuator is coupled with a base
of the compression chamber, and an amplifying element is disposed
between the piezoelectric actuator and the fluid compressor's
piston. A piston of 150 grams, a piezoelectric actuator of mass
37.7 grams and stiffness constant of 4.times.106 N/m was used. The
fluid pressure in the compression chamber was maintained at
1.times.106 Pa. It can be seen from the results obtained from the
experimental tests of the two configurations that the configuration
as per the embodiment of the present technique provides for
amplified displacement of the fluid compressor's piston.
[0034] Further for experimental testing of the fluid compressor
102, a spring with a stiffness of 1.2.times.105 N/m and a
piezoelectric actuator with a constant of 4.times.106 N/m were
selected. The experimental set-up results were compared against a
performance of a fluid compressor using only the piezoelectric
actuator with the same constant. It was observed that with varying
amplitude of excitation signal; the displacement in the fluid
compressor as described in the present technique was greater than
displacement achieved by using only the piezoelectric actuator. For
example, for a voltage of 40V using only the aforementioned
piezoelectric actuator a displacement of 2.9 .mu.m is achieved,
whereas using the driving system of the fluid compressor 102
described in the present technique a displacement of 74.5 .mu.m is
achieved for a voltage of 40V. Similarly for an excitation signal
of 120V usage of only the piezoelectric actuator provides a
displacement of 42.7 .mu.m whereas the driving system of the fluid
compressor 102 of the present technique provides for a displacement
of 326 .mu.m. The degree of displacement amplification observed for
various amplifying element stiffness has been observed to be at
least 7.0.
[0035] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" should be understood as not
excluding plural said elements or steps, unless such exclusion is
explicitly recited. Furthermore, references to "one embodiment" of
the present invention are not intended to be interpreted as
excluding the existence of additional embodiments that also
incorporate the recited features. The systems and methods
illustrated are not limited to the specific embodiments described
herein, but rather, components of the system may be utilized
independently and separately from other components described
herein. Further, steps described in the method may be utilized
independently and separately from other steps described herein.
[0036] While only certain features of embodiments of the invention
have been illustrated and described herein, many modifications and
changes will occur by those skilled in the art. It is, therefore,
to be understood that the appended claims are intended to cover all
such modifications and changes as they fall within the true spirit
of embodiments of the invention.
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