Note: Descriptions are shown in the official language in which they were submitted.
COMPRESSOR WITH LIQUID
INJECTION COOLING
BACKGROUND
1. Technical Field.
[001] The invention generally relates to fluid pumps, such as compressors
and expanders. More specifically, preferred embodiments utilize a novel rotary
compressor design for compressing air, vapor, or gas for high pressure
conditions
over 200 psi and power ratings above 10 HP.
2. Related Art.
[002] Compressors have typically been used for a variety of applications,
such as air compression, vapor compression for refrigeration, and compression
of
industrial gases. Compressors can be split into two main groups, positive
displacement and dynamic. Positive displacement compressors reduce the volume
of
the compression chamber to increase the pressure of the fluid in the chamber.
This is
done by applying force to a drive shaft that is driving the compression
process.
Dynamic compressors work by transferring energy from a moving set of blades to
the
working fluid.
[003] Positive displacement compressors can take a variety of forms. They
are typically classified as reciprocating or rotary compressors. Reciprocating
compressors are commonly used in industrial applications where higher pressure
ratios are necessary. They can easily be combined into multistage machines,
although
single stage reciprocating compressors are not typically used at pressures
above 80
psig. Reciprocating compressors use a piston to compress the vapor, air, or
gas, and
have a large number of components to help translate the rotation of the drive
shaft
into the reciprocating motion used for compression. This can lead to increased
cost
and reduced reliability. Reciprocating compressors also suffer from high
levels of
vibration and noise. This technology has been used for many industrial
applications
such as natural gas compression.
[004] Rotary compressors use a rotating component to perform compression.
As noted in the art, rotary compressors typically have the following features
in
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common: (1) they impart energy to the gas being compressed by way of an input
shaft
moving a single or multiple rotating elements; (2) they perform the
compression in an
intermittent mode; and (3) they do not use inlet or discharge valves. (Brown,
Compressors: Selection and Sizing, 3rd Ed., at 6). As further noted in Brown,
rotary
compressor designs are generally suitable for designs in which less than 20:1
pressure
ratios and 1000 CFM flow rates are desired. For pressure ratios above 20:1,
Royce
suggests that multistage reciprocating compressors should be used instead.
[005] Typical rotary compressor designs include the rolling piston, screw
compressor, scroll compressor, lobe, liquid ring, and rotary vane compressors.
Each
of these traditional compressors has deficiencies for producing high pressure,
near
isothermal conditions.
[006] The design of a rotating element/rotor/lobe against a radially moving
element/piston to progressively reduce the volume of a fluid has been utilized
as early
as the mid-19th century with the introduction of the "Yule Rotary Steam
Engine."
Developments have been made to small-sized compressors utilizing this
methodology
into refrigeration compression applications. However, current Yule-type
designs are
limited due to problems with mechanical spring durability (returning the
piston
element) as well as chatter (insufficient acceleration of the piston in order
to maintain
contact with the rotor).
[007] For commercial applications, such as compressors for refrigerators,
small rolling piston or rotary vane designs are typically used. (P N
Ananthanarayanan, Basic Refrigeration and Air Conditioning, 3rd Ed., at 171-
72.) In
these designs, a closed oil-lubricating system is typically used.
[008] Rolling piston designs typically allow for a significant amount of
leakage between an eccentrically mounted circular rotor, the interior wall of
the
casing, and/or the vane that contacts the rotor. By spinning the rolling
piston faster,
the leakages are deemed acceptable because the desired pressure and flow rate
for the
application can be easily reached even with these losses. The benefit of a
small self-
contained compressor is more important than seeking higher pressure ratios.
[009] Rotary vane designs typically use a single circular rotor mounted
eccentrically in a cylinder slightly larger than the rotor. Multiple vanes are
positioned
in slots in the rotor and are kept in contact with the cylinder as the rotor
turns
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typically by spring or centrifugal force inside the rotor. The design and
operation of
these type of compressors may be found in Mark's Standard Handbook for
Mechanical Engineers, Eleventh Edition, at 14:33-34.
[010] In a sliding-vane compressor design, vanes are mounted inside the
rotor to slide against the casing wall. Alternatively, rolling piston designs
utilize a
vane mounted within the cylinder that slides against the rotor. These designs
are
limited by the amount of restoring force that can be provided and thus the
pressure
that can be yielded.
[011] Each of these types of prior art compressors has limits on the
maximum pressure differential that it can provide. Typical factors include
mechanical
stresses and temperature rise. One proposed solution is to use multistaging.
In
multistaging, multiple compression stages are applied sequentially.
Intercooling, or
cooling between stages, is used to cool the working fluid down to an
acceptable level
to be input into the next stage of compression. This is typically done by
passing the
working fluid through a heat exchanger in thermal communication with a cooler
fluid.
However, intercooling can result in some condensation of liquid and typically
requires
filtering out of the liquid elements. Multistaging greatly increases the
complexity of
the overall compression system and adds costs due to the increased number of
components required. Additionally, the increased number of components leads to
decreased reliability and the overall size and weight of the system are
markedly
increased.
[012] For industrial applications, single- and double-acting reciprocating
compressors and helical-screw type rotary compressors are most commonly used.
Single-acting reciprocating compressors are similar to an automotive type
piston with
compression occurring on the top side of the piston during each revolution of
the
crankshaft. These machines can operate with a single-stage discharging between
25
and 125 psig or in two stages, with outputs ranging from 125 to 175 psig or
higher.
Single-acting reciprocating compressors are rarely seen in sizes above 25 HP.
These
types of compressors are typically affected by vibration and mechanical stress
and
require frequent maintenance. They also suffer from low efficiency due to
insufficient cooling.
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[013] Double-acting reciprocating compressors use both sides of the piston
for compression, effectively doubling the machine's capacity for a given
cylinder
size. They can operate as a single-stage or with multiple stages and are
typically sized
greater than 10 HP with discharge pressures above 50 psig. Machines of this
type with
only one or two cylinders require large foundations due to the unbalanced
reciprocating forces. Double-acting reciprocating compressors tend to be quite
robust
and reliable, but are not sufficiently efficient, require frequent valve
maintenance, and
have extremely high capital costs.
[014] Lubricant-flooded rotary screw compressors operate by forcing fluid
between two intermeshing rotors within a housing which has an inlet port at
one end
and a discharge port at the other. Lubricant is injected into the chamber to
lubricate
the rotors and bearings, take away the heat of compression, and help to seal
the
clearances between the two rotors and between the rotors and housing. This
style of
compressor is reliable with few moving parts. However, it becomes quite
inefficient at
higher discharge pressures (above approximately 200 psig) due to the
intermeshing
rotor geometry being forced apart and leakage occurring. In addition, lack of
valves
and a built-in pressure ratio leads to frequent over or under compression,
which
translates into significant energy efficiency losses.
[015] Rotary screw compressors are also available without lubricant in the
compression chamber, although these types of machines are quite inefficient
due to
the lack of lubricant helping to seal between the rotors. They are a
requirement in
some process industries such as food and beverage, semiconductor, and
pharmaceuticals, which cannot tolerate any oil in the compressed air used in
their
processes. Efficiency of dry rotary screw compressors are 15-20% below
comparable
injected lubricated rotary screw compressors and are typically used for
discharge
pressures below 150 psig.
[016] Using cooling in a compressor is understood to improve upon the
efficiency of the compression process by extracting heat, allowing most of the
energy
to be transmitted to the gas and compressing with minimal temperature
increase.
3() Liquid injection has previously been utilized in other compression
applications for
cooling purposes. Further, it has been suggested that smaller droplet sizes of
the
injected liquid may provide additional benefits.
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[017] In U.S. Pat. No. 4,497,185, lubricating oil was intercooled and injected
through an atomizing nozzle into the inlet of a rotary screw compressor. In a
similar
fashion, U.S. Pat. No. 3,795,117 uses refrigerant, though not in an atomized
fashion,
that is injected early in the compression stages of a rotary screw compressor.
Rotary
vane compressors have also attempted finely atomized liquid injection, as seen
in U.S.
Pat. No. 3,820,923.
[018] In each example, cooling of the fluid being compressed was desired.
Liquid injection in rotary screw compressors is typically done at the inlet
and not
within the compression chamber. This provides some cooling benefits, but the
liquid
is given the entire compression cycle to coalesce and reduce its effective
heat transfer
coefficient. Additionally, these examples use liquids that have lubrication
and sealing
as a primary benefit. This affects the choice of liquid used and may adversely
affect
its heat transfer and absorption characteristics. Further, these styles of
compressors
have limited pressure capabilities and thus are limited in their potential
market
applications.
[019] Rotary designs for engines are also known, but suffer from deficiencies
that would make them unsuitable for an efficient compressor design. The most
well-
known example of a rotary engine is the Wankel engine. While this engine has
been
shown to have benefits over conventional engines and has been commercialized
with
some success, it still suffers from multiple problems, including low
reliability and
high levels of hydrocarbon emissions.
[020] Published International Pat. App. No. WO 2010/017199 and U.S. Pat.
Pub. No. 2011/0023814 relate to a rotary engine design using a rotor, multiple
gates
to create the chambers necessary for a combustion cycle, and an external cam-
drive
for the gates. The force from the combustion cycle drives the rotor, which
imparts
force to an external element. Engines are designed for a temperature increase
in the
chamber and high temperatures associated with the combustion that occurs
within an
engine. Increased sealing requirements necessary for an effective compressor
design
are unnecessary and difficult to achieve. Combustion forces the use of
positively
contacting seals to achieve near perfect sealing, whil6 leaving wide
tolerances for
metal expansion, taken up by the seals, in an engine. Further, injection of
liquids for
cooling would be counterproductive and coalescence is not addressed.
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[021] Liquid mist injection has been used in compressors, but with limited
effectiveness. In U.S. Pat. No. 5,024,588, a liquid injection mist is
described, but
improved heat transfer is not addressed. In U.S. Pat. Publication. No. U.S.
2011/0023977, liquid is pumped through atomizing nozzles into a reciprocating
piston
compressor's compression chamber prior to the start of compression. It is
specified
that liquid will only be injected through atomizing nozzles in low pressure
applications. Liquid present in a reciprocating piston compressor's cylinder
causes a
high risk for catastrophic failure due to hydrolock, a consequence of the
incompressibility of liquids when they build up in clearance volumes in a
reciprocating piston, or other positive displacement, compressor. To prevent
hydrolock situations, reciprocating piston compressors using liquid injection
will
typically have to operate at very slow speeds, adversely affecting the
performance of
the compressor.
[022] The prior art lacks compressor designs in which the application of
liquid injection for cooling provides desired results for a near-isothermal
application.
This is in large part due to the lack of a suitable positive displacement
compressor
design that can both accommodate a significant amount of liquid in the
compression
chamber and pass that liquid through the compressor outlet without damage.
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BRIEF SUMMARY
[023] The presently preferred embodiments are directed to rotary compressor
designs. These designs are particularly suited for high pressure applications,
typically
above 200 psig with compression ratios typically above for existing high-
pressure
positive displacement compressors.
[024] One illustrative embodiment of the design includes a non-circular-
shaped rotor rotating within a cylindrical casing and mounted concentrically
on a
drive shaft inserted axially through the cylinder. The rotor is symmetrical
along the
axis traveling from the drive shaft to the casing with cycloid and constant
radius
portions. The constant radius portion corresponds to the curvature of the
cylindrical
casing, thus providing a sealing portion. The changing rate of curvature on
the other
portions provides for a non-sealing portion. In this illustrative embodiment,
the rotor
is balanced by way of holes and counterweights.
[025] A gate structured similar to a reciprocating rectangular piston is
inserted into and withdrawn from the bottom of the cylinder in a timed manner
such
that the tip of the piston remains in contact with or sufficiently proximate
to the
surface of the rotor as it turns. The coordinated movement of the gate and the
rotor
separates the compression chamber into a low pressure and high pressure
region.
[026] As the rotor rotates inside the cylinder, the compression volume is
progressively reduced and compression of the fluid occurs. At the same time,
the
intake side is filled with gas through the inlet. An inlet and exhaust are
located to
allow fluid to enter and exit the chamber at appropriate times. During the
compression process, atomized liquid is injected into the compression chamber
in
such a way that a high and rapid rate of heat transfer is achieved between the
gas
being compressed and the injected cooling liquid. This results in near
isothermal
compression, which enables a much higher efficiency compression process.
[027] The rotary compressor embodiments sufficient to achieve near
isothermal compression are capable of achieving high pressure compression at
higher
efficiencies. It is capable of compressing gas only, a mixture of gas and
liquids, or for
pumping liquids. As one of ordinary skill in the art would appreciate, the
design can
also be used as an expander.
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[028] The particular rotor and gate designs may also be modified depending
on application parameters. For example, different cycloidal and constant radii
may be
employed. Alternatively, double harmonic or other functions may be used for
the
variable radius. The gate may be of one or multiple pieces. It may implement a
contacting tip-seal, liquid channel, or provide a non-contacting seal by which
the gate
is proximate to the rotor as it turns.
[029] Several embodiments provide mechanisms for driving the gate external
to the main casing. In one embodiment, a spring-backed cam drive system is
used. In
others, a belt-based system with or without springs may be used. In yet
another, a
dual cam follower gate positioning system is used. Further, an offset gate
guide
system may be used. Further still, linear actuator, magnetic drive, and scotch
yoke
systems may be used.
[030] The presently preferred embodiments provide advantages not found in
the prior art. The design is tolerant of liquid in the system, both coming
through the
inlet and injected for cooling purposes. High compression ratios are
achievable due to
effective cooling techniques. Lower vibration levels and noise are generated.
Valves
are used to minimize inefficiencies resulting from over- and under-compression
common in existing rotary compressors. Seals are used to allow higher
pressures and
slower speeds than typical with other rotary compressors. The rotor design
allows for
balanced, concentric motion, reduced acceleration of the gate, and effective
sealing
between high pressure and low pressure regions of the compression chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[031] The invention can be better understood with reference to the following
drawings and description. The components in the figures are not necessarily to
scale,
emphasis instead being placed upon illustrating the principles of the
invention.
Moreover, in the figures, like referenced numerals designate corresponding
parts
throughout the different views.
[032] Figure 1 is a perspective view of a rotary compressor with a spring-
backed cam drive in accordance with an embodiment of the present invention.
[033] Figure 2 is a right-side view of a rotary compressor with a spring-
backed cam drive in accordance with an embodiment of the present invention.
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[034] Figure 3 is a left-side view of a rotary compressor with a spring-backed
cam drive in accordance with an embodiment of the present invention.
[035] Figure 4 is a front view of a rotary compressor with a spring-backed
cam drive in accordance with an embodiment of the present invention.
[036] Figure 5 is a back view of a rotary compressor with a spring-backed
cam drive in accordance with an embodiment of the present invention.
[037] Figure 6 is a top view of a rotary compressor with a spring-backed cam
drive in accordance with an embodiment of the present invention.
[038] Figure 7 is a bottom view of a rotary compressor with a spring-backed
cam drive in accordance with an embodiment of the present invention.
[039] Figure 8 is a cross-sectional view of a rotary compressor with a spring-
backed cam drive in accordance with an embodiment of the present invention.
[040] Figure 9 is a perspective view of rotary compressor with a belt-driven,
spring-biased gate positioning system in accordance with an embodiment of the
present invention.
[041] Figure 10 is a perspective view of a rotary compressor with a dual cam
follower gate positioning system in accordance with an embodiment of the
present
invention.
[042] Figure ills a right-side view of a rotary compressor with a dual cam
follower gate positioning system in accordance with an embodiment of the
present
invention.
[043] Figure 12 is a left-side view of a rotary compressor with a dual cam
follower gate positioning system in accordance with an embodiment of the
present
invention.
[044] Figure 13 is a front view of a rotary compressor with a dual cam
follower gate positioning system in accordance with an embodiment of the
present
invention.
[045] Figure 14 is a back view of a rotary compressor with a dual cam
follower gate positioning system in accordance with an embodiment of the
present
3() invention.
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[046] Figure 15 is a top view of a rotary compressor with a dual cam
follower gate positioning system in accordance with an embodiment of the
present
invention.
[047] Figure 16 is a bottom view of a rotary compressor with a dual cam
follower gate positioning system in accordance with an embodiment of the
present
invention.
[048] Figure 17 is a cross-sectional view of a rotary compressor with a dual
cam follower gate positioning system in accordance with an embodiment of the
present invention.
[049] Figure 18 is perspective view of a rotary compressor with a belt-driven
gate positioning system in accordance with an embodiment of the present
invention.
[050] Figure 19 is perspective view of a rotary compressor with an offset
gate guide positioning system in accordance with an embodiment of the present
invention.
[051] Figure 20 is a right-side view of a rotary compressor with an offset
gate guide positioning system in accordance with an embodiment of the present
invention.
[052] Figure 21 is a front view of a rotary compressor with an offset gate
guide positioning system in accordance with an embodiment of the present
invention.
[053] Figure 22 is a cross-sectional view of a rotary compressor with an
offset gate guide positioning system in accordance with an embodiment of the
present
invention.
[054] Figure 23 is perspective view of a rotary compressor with a linear
actuator gate positioning system in accordance with an embodiment of the
present
invention.
[055] Figures 24A and B are right side and cross-section views, respectively,
of a rotary compressor with a magnetic drive gate positioning system in
accordance
with an embodiment of the present invention
[056] Figure 25 is perspective view of a rotary compressor with a scotch
yoke gate positioning system in accordance with an embodiment of the present
invention.
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[057] Figures 26A-F are cross-sectional views of the inside of an
embodiment of a rotary compressor with a contacting tip seal in a compression
cycle
in accordance with an embodiment of the present invention.
[058] Figures 27A-F are cross-sectional vieWs of the inside of an
embodiment of a rotary compressor without a contacting tip seal in a
compression
cycle in accordance with another embodiment of the present invention.
[059] Figure 28 is perspective, cross-sectional view of a rotary compressor in
accordance with an embodiment of the present invention.
[060] Figure 29 is a left-side view of an additional liquid injectors
embodiment of the present invention.
[061] Figure 30 is a cross-section view of a rotor design in accordance with
an embodiment of the present invention.
[062] Figures 31A-D are cross-sectional views of rotor designs in accordance
with various embodiments of the present invention.
[063] Figures 32A and B are perspective and right-side views of a drive
shaft, rotor, and gate in accordance with an embodiment of the present
invention.
[064] Figure 33 is a perspective view of a gate with exhaust ports in
accordance with an embodiment of the present invention.
[065] Figure 34A and B are a perspective view and magnified view of a gate
with notches, respectively, in accordance with an embodiment of the present
invention.
[066] Figure 35 is a cross-sectional, perspective view a gate with a rolling
tip
in accordance with an embodiment of the present invention.
[067] Figure 36 is a cross-sectional front view of a gate with a liquid
injection channel in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[068] To the extent that the following terms are utilized herein, the
following
definitions are applicable:
[069] Balanced rotation: the center of mass of the rotating mass is located
on the axis of rotation.
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[070] Chamber volume: any volume that can contain fluids for
compression.
[071] Compressor: a device used to increase the pressure of a compressible
fluid. The fluid can be either gas or vapor, and can have a wide molecular
weight
range.
[072] Concentric: the center or axis of one object coincides with the center
or axis of a second object
[073] Concentric rotation: rotation in which one object's center of rotation
is located on the same axis as the second object's center of rotation.
[074] Positive displacement compressor: a compressor that collects a fixed
volume of gas within a chamber and compresses it by reducing the chamber
volume.
[075] Proximate: sufficiently close to restrict fluid flow between high
pressure and low pressure regions. Restriction does not need to be absolute;
some
leakage is acceptable.
1.5 [076] Rotor: A rotating element driven by a mechanical force to rotate
about an axis. As used in a compressor design, the rotor imparts energy to a
fluid.
[077] Rotary compressor: A positive-displacement compressor that
imparts energy to the gas being compressed by way of an input shaft moving a
single
or multiple rotating elements
[078] Figures 1 through 7 show external views of an embodiment of the
present invention in which a rotary compressor includes spring backed cam
drive gate
positioning system. Main housing 100 includes a main casing 110 and end plates
120,
each of which includes a hole through which drive shaft 140 passes axially.
Liquid
injector assemblies 130 are located on holes in the main casing 110. The main
casing
includes a hole for the inlet flange 160, and a hole for the gate casing 150.
[079] Gate casing 150 is connected to and positioned below main casing 110
at a hole in main casing 110. The gate casing 150 is comprised of two
portions: an
inlet side 152 and an outlet side 154. As shown in Figure 28, the outlet side
154
includes outlet ports 435, which are holes which lead to outlet valves 440.
Alternatively, an outlet valve assembly may be used.
[080] Referring back to Figures 1-7, the spring-backed cam drive gate
positioning system 200 is attached to the gate casing 150 and drive shaft 140.
The
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gate positioning system 200 moves gate 600 in conjunction with the rotation of
rotor
500. A movable assembly includes gate struts 210 and cam struts 230 connected
to
gate support arm 220 and bearing support plate 156. The bearing support plate
156
seals the gate casing 150 by interfacing with the inlet and outlet sides
through a bolted
gasket connection. Bearing support plate 156 is shaped to seal gate casing
150, mount
bearing housings 270 in a sufficiently parallel manner, and constrain
compressive
springs 280. Bearing housings 270, also known as pillow blocks, are concentric
to the
gate struts 210 and the cam struts 230.
[081] Two cam followers 250 are located tangentially to each cam 240,
providing a downward force on the gate. Drive shaft 140 turns cams 240, which
transmits force to the cam followers 250. The cam followers 250 may be mounted
on
a through shaft, which is supported on both ends, or cantilevered and only
supported
on one end. The cam followers 250 are attached to cam follower supports 260,
which
transfer the force into the cam struts 230. As cams 240 turn, the cam
followers 250 are
pushed down, thus moving the cam struts 230 down. This moves the gate support
arm
220 and the gate strut 210 down. This, in turn, moves the gate 600 down.
[082] Springs 280 provide a restorative upward force to keep the gate 600
timed appropriately to seal against the rotor 500. As the cams 240 continue to
turn
and no longer effectuate a downward force on the cam followers 250, springs
280
provide an upward force. As shown in this embodiment, compression springs are
utilized. As one of ordinary skill in the art would appreciate, tension
springs and the
shape of the bearing support plate 156 may be altered to provide for the
desired
upward or downward force. The upward force of the springs 280 pushes the cam
follower support 260 and thus the gate support arm 220 up which in turn moves
the
gate 600 up.
[083] Due to the varying pressure angle between the cam followers 250 and
cams 240, the preferred embodiment may utilize an exterior cam profile that
differs
from the rotor 500 profile. This variation in profile allows for compensation
for the
changing pressure angle to ensure that the tip of the gate 600 remains
proximate to the
3() rotor 500 throughout the entire compression cycle.
[084] Line A in Figures 3, 6, and 7 shows the location for the cross-sectional
view of the compressor in Figure 8. As shown in Figure 8, the main casing 110
has a
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cylindrical shape. Liquid injector housings 132 are attached to, or may be
cast as a
part of, the main casing 110 to provide for openings in the rotor casing 400.
Because
it is cylindrically shaped in this embodiment, the rotor casing 400 may also
be
referenced as the cylinder. The interior wall defines a rotor casing volume
410. The
rotor 500 concentrically rotates with drive shaft 140 and is affixed to the
drive shaft
140 by way of key 540 and press fit.
[085] Figure 9 shows an embodiment of the present invention in which a
timing belt with spring gate positioning system is utilized. This embodiment
290
incorporates two timing belts 292 each of which is attached to the drive shaft
140 by
way of sheaves 294. The timing belts 292 are attached to secondary shafts 142
by
way of sheaves 295. Gate strut springs 296 are mounted around gate struts.
Rocker
arms 297 are mounted to rocker arm supports 299. The sheaves 295 are connected
to
rocker arm cams 293 to push the rocker arms 297 down. As the inner rings push
down on one side of the rocker arms 297, the other side pushes up against the
gate
support bar 298. The gate support bar 298 pushes up against the gate struts
and gate
strut springs 296. This moves the gate up. The springs 296 provide a downward
force pushing the gate down.
[086] Figures 10 through 17 show external views of a rotary compressor
embodiment utilizing a dual cam follower gate positioning system. The main
housing
100 includes a main casing 110 and end plates 120, each of which includes a
hole
through which a drive shaft 140 passes axially. Liquid injector assemblies 130
are
located on holes in the main casing 110. The main casing 110 also includes a
hole for
the inlet flange 160 and a hole for the gate casing 150. The gate casing 150
is
mounted to and positioned below the main casing 110 as discussed above.
[087] A dual cam follower gate positioning system 300 is attached to the gate
casing 150 and drive shaft 140. The dual cam follower gate positioning system
300
moves the gate 600 in conjunction with the rotation of the rotor 500. In a
preferred
embodiment, the size and shape of the cams is nearly identical to the rotor in
cross-
sectional size and shape. In other embodiments, the rotor, cam shape,
curvature, cam
3() thickness, and variations in the thickness of the lip of the cam may be
adjusted to
account for variations in the attack angle of the cam follower. Further, large
or
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smaller cam sizes may be used. For example, a similar shape but smaller size
cam
may be used to reduce roller speeds.
[088] A movable assembly includes gate struts 210 and cam struts 230
connected to gate support arm 220 and bearing support plate 156. In this
embodiment, the bearing support plate 157 is straight. As one of ordinary
skill in the
art would appreciate, the bearing support plate can utilize different
geometries,
including structures designed to or not to perform sealing of the gate casing
150. In
this embodiment, the bearing support plate 157 serves to seal the bottom of
the gate
casing 150 through a bolted gasket connection. Bearing housings 270, also
known as
pillow blocks, are mounted to bearing support plate 157 and are concentric to
the gate
struts 210 and the cam struts 230.
[089] Drive shaft 140 turns cams 240, which transmit force to the cam
followers 250, including upper cam followers 252 and lower cam followers 254.
The
cam followers 250 may be mounted on a through shaft, which is supported on
both
ends, or cantilevered and only supported on one end. In this embodiment, four
cam
followers 250 are used for each cam 240. Two lower cam followers 252 are
located
below and follow the outside edge of the cam 240. They are mounted using a
through
shaft. Two upper cam followers 254 are located above the previous two and
follow
the inside edge of the cams 240. They are mounted using a cantilevered
connection.
[090] The cam followers 250 are attached to cam follower supports 260,
which transfer the force into the cam struts 230. As the cams 240 turn, the
cam struts
230 move up and down. This moves the gate support arm 220 and gate struts 210
up
and down, which in turn, moves the gate 600 up and down.
[091] Line A in Figures 11, 12, 15, and 16 show the location for the cross-
sectional view of the compressor in Figure 17. As shown in Figure 17, the main
casing 110 has a cylindrical shape. Liquid injector housings 132 are attached
to or
may be cast as a part of the main casing 110 to provide for openings in the
rotor
casing 400. The rotor 500 concentrically rotates around drive shaft 140.
[092] An embodiment using a belt driven system 310 is shown in Figure 18.
Timing belts 292 are connected to the drive shaft 140 by way of sheaves 294.
The
timing belts 292 are each also connected to secondary shafts 142 by way of
another
set of sheaves 295. The secondary shafts 142 drive the external cams 240,
which are
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placed below the gate casing 150 in this embodiment. Sets of upper and lower
cam
followers 254 and 252 are applied to the cams 240, which provide force to the
movable assembly including gate struts 210 and gate support arm 220. As one of
ordinary skill in the art would appreciate, belts may be replaced by chains or
other
materials.
[093] An embodiment of the present invention using an offset gate guide
system is shown in Figures 19 through 22 and 33. Outlet of the compressed gas
and
injected fluid is achieved through a ported gate system 602 comprised of two
parts
bolted together to allow for internal lightening features. Fluid passes
through
channels 630 in the upper portion of the gate 602 and travels to the
lengthwise sides to
outlet through an exhaust port 344 in a timed manner with relation to the
angle of
rotation of the rotor 500 during the cycle. Discrete point spring-backed
scraper seals
326 provide sealing of the gate 602 in the single piece gate casing 336.
Liquid
injection is achieved through a variety of flat spray nozzles 322 and injector
nozzles
130 across a variety of liquid injector port 324 locations and angles.
[094] Reciprocating motion of the two-piece gate 602 is controlled through
the use of an offset spring-backed cam follower control system 320 to achieve
gate
motion in concert with rotor rotation. Single cams 342 drive the gate system
downwards through the transmission of force on the cam followers 250 through
the
cam struts 338. This results in controlled motion of the crossarm 334, which
is
connected by bolts (some of which are labeled as 328) with the two-piece gate
602.
The crossarm 334 mounted linear bushings 330, which reciprocate along the
length of
cam shafts 332, control the motion of the gate 602 and the crossarm 334. The
cam
shafts 332 are fixed in a precise manner to the main casing through the use of
cam
shaft support blocks 340. Compression springs 346 are utilized to provide a
returning
force on the crossarm 334, allowing the cam followers 250 to maintain constant
rolling contact with the cams, thereby achieving controlled reciprocating
motion of
the two-piece gate 602.
[095] Figure 23 shows an embodiment using a linear actuator system 350 for
gate positioning. A pair of linear actuators 352 is used to drive the gate. In
this
embodiment, it is not necessary to mechanically link the drive shaft to the
gate as with
other embodiments. The linear actuators 352 are controlled so as to raise and
lower
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the gate in accordance with the rotation of the rotor. The actuators may be
electronic,
hydraulic, belt-driven, electromagnetic, gas-drivern, variable-friction, or
other means.
The actuators may be computer controlled or controlled by other means.
[096] Figures 24A and B show a magnetic drive system 360. The gate
system may be driven, or controlled, in a reciprocating motion through the
placement
of magnetic field generators, whether they are permanent magnets or
electromagnets,
on any combination of the rotor 500, gate 600, and/or gate casing 150. The
purpose
of this system is to maintain a constant distance from the tip of the gate 600
to the
surface of the rotor 500 at all angles throughout the cycle. In a preferred
magnetic
system embodiment, permanent magnets 366 are mounted into the ends of the
rotor
500 and retained. In addition, permanent magnets 364 are installed and
retained in the
gate 600. Poles of the magnets are aligned so that the magnetic force
generated
between the rotor's magnets 366 and the gate's magnets 364 is a repulsive
force,
forcing the gate 600 down throughout the cycle to control its motion and
maintain
constant distance. To provide an upward, returning force on the gate 600,
additional
magnets (not shown) are installed into the bottom of the gate 600 and the
bottom of
the gate casing 150 to provide an additional repulsive force. The magnetic
drive
systems are balanced to precisely control the gate's reciprocating motion.
[097] Alternative embodiments may use an alternate pole orientation to
provide attractive forces between the gate and rotor on the top portion of the
gate and
attractive forces between the gate and gate casing on the bottom portion of
the gate. In
place of the lower magnet system, springs may be used to provide a repulsive
force.
In each embodiment, electromagnets may be used in place of permanent magnets.
In
addition, switched reluctance electromagnets may also be utilized. In another
embodiment, electromagnets may be used only in the rotor and gate. Their poles
may
switch at each inflection point of the gate's travel during its reciprocating
cycle,
allowing them to be used in an attractive and repulsive method.
[098] Alternatively, direct hydraulic or indirect hydraulic (hydropneumatic)
can be used to apply motive force/energy to the gate to drive it and position
it
adequately. Solenoid or other flow control valves can be used to feed and
regulate the
position and movement of the hydraulic or hydropneumatic elements. Hydraulic
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force may be converted to mechanical force acting on the gate through the use
of a
cylinder based or direct hydraulic actuators using membranes/diaphragms.
[099] Figure 25 shows an embodiment using a scotch yoke gate positioning
system 370. Here, a pair of scotch yokes 372 is connected to the drive shaft
and the
bearing support plate. A roller rotates at a fixed radius with respect to the
shaft. The
roller follows a slot within the yoke 372, which is constrained to a
reciprocating
motion. The yoke geometry can be manipulated to a specific shape that will
result in
desired gate dynamics.
[0100] As one of skill in the art would appreciate, these alternative drive
mechanisms do not require any particular number of linkages between the drive
shaft
and the gate. For example, a single spring, belt, linkage bar, or yoke could
be used.
Depending on the design implementation, more than two such elements could be
used.
[0101] Figures 26A-26F show a compression cycle of an embodiment
utilizing a tip seal 620. As the drive shaft 140 turns, the rotor 500 and gate
strut 210
push up gate 600 so that it is timed with the rotor 500. As the rotor 500
turns
clockwise, the gate 600 rises up until the rotor 500 is in the 12 o'clock
position shown
in Figure 26C. As the rotor 500 continues to turn, the gate 600 moves downward
until
it is back at the 6 o'clock position in Figure 26F. The gate 600 separates the
portion
of the cylinder that is not taken up by rotor 500 into two components: an
intake
component 412 and a compression component 414.
[0102] Figures 26A-F depict steady state operation. Accordingly, in Figure
26A, where the rotor 500 is in the 6 o'clock position, the compression volume
414,
which constitutes a subset of the rotor casing volume 410, already has
received fluid.
In Figure 26B, the rotor 500 has turned clockwise and gate 600 has risen so
that the
tip seal 620 makes contact with the rotor 500 to separate the intake volume
412,
which also constitutes a subset of the rotor casing volume 410, from the
compression
volume 414. Embodiments using the roller tip 650 discussed below instead of
tip seal
620 would operate similarly. As the rotor 500 turns, as shown further in
Figures 26C-
E, the intake volume 412 increases, thereby drawing in more fluid from inlet
420,
while the compression volume 414 decreases. As the volume of the compression
volume 414 decreases, the pressure increases. The pressurized fluid is then
expelled
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by way of an outlet 430. At a point in the compression cycle when a desired
high
pressure is reached, the outlet valve opens and the high pressure fluid can
leave the
compression volume 414. In this embodiment, the valve outputs both the
compressed
gas and the liquid injected into the compression chamber.
[0103] Figures 27A ¨ 27F show an embodiment in which the gate 600 does
not use a tip seal. Instead, the gate 600 is timed to be proximate to the
rotor 500 as it
turns. The close proximity of the gate 600 to the rotor 500 leaves only a very
small
path for high pressure fluid to escape. Close proximity in conjunction with
the
presence of liquid (due to the liquid injectors 136 or an injector placed in
the gate
itself) allow the gate 600 to effectively create an intake fluid component 412
and a
compression component 414. Embodiments incorporating notches 640 would operate
similarly.
[0104] Figure 28 shows a cross-sectional perspective view of the rotor casing
400, the rotor 500, and the gate 600. The inlet port 420 shows the path that
gas can
enter. The outlet 430 is comprised of several holes that serve as outlet ports
435 that
lead to outlet valves 440. The gate casing 150 consists of an inlet side 152
and an
outlet side 154. A return pressure path (not shown) may be connected to the
inlet side
152 of the gate casing 150 and the inlet port 420 to ensure that there is no
back
pressure build up against gate 600 due to leakage through the gate seals. As
one of
ordinary skill in the art would appreciate, it is desirable to achieve a
hermetic seal,
although perfect hermetic sealing is not necessary.
[0105] Figure 29 shows an alternative embodiment in which flat spray liquid
injector housings 170 are located on the main casing 110 at approximately the
3
o'clock position. These injectors can be used to inject liquid directly onto
the inlet
side of the gate 600, ensuring that it does not reach high temperatures. These
injectors also help to provide a coating of liquid on the rotor 500, helping
to seal the
compressor.
[0106] As discussed above, the preferred embodiments utilize a rotor that
concentrically rotates within a rotor casing. In the preferred embodiment, the
rotor
500 is a right cylinder with a non-circular cross-section that runs the length
of the
main casing 110. Figure 30 shows a cross-sectional view of the sealing and non-
sealing portions of the rotor 500. The profile of the rotor 500 is comprised
of three
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sections. The radii in sections I and III are defined by a cycloidal curve.
This curve
also represents the rise and fall of the gate and defines an optimum
acceleration
profile for the gate. Other embodiments may use different curve functions to
define
the radius such as a double harmonic function. Section II employs a constant
radius
570, which corresponds to the maximum radius of the rotor. The minimum radius
580 is located at the intersection of sections I and III, at the bottom of
rotor 500. In a
preferred embodiment, LII is 23.8 degrees. In alternative embodiments, other
angles
may be utilized depending on the desired size of the compressor, the desired
acceleration of the gate, and desired sealing area.
[0107] The radii of the rotor 500 in the preferred embodiment can be
calculated using the following functions:
= rnun+ + sin (271-t1)]
r(t) = rir = ax
rm = rmin h[tan + sin (27rt
T T
[0108] In a preferred embodiment, the rotor 500 is symmetrical along one
axis. It may generally resemble a cross-sectional egg shape. The rotor 500
includes a
hole 530 in which the drive shaft 140 and a key 540 may be mounted. The rotor
500
has a sealing section 510, which is the outer surface of the rotor 500
corresponding to
section II, and a non-sealing section 520, which is the outer surface of the
rotor 500
corresponding to sections I and III. The sections I and III have a smaller
radius than
sections II creating a compression volume.
[0109] The sealing portion 510 is shaped to correspond to the curvature of the
rotor casing 400, thereby creating a dwell seal that effectively minimizes
communication between the outlet 430 and inlet 420. Physical contact is not
required
for the dwell seal. Instead, it is sufficient to create a tortuous path that
minimizes the
amount of fluid that can pass through. In a preferred embodiment, the gap
between the
rotor and the casing in this embodiment is less than 0.008 inches. As one of
ordinary
skill in the art would appreciate, this gap may be altered depending on
tolerances,
both in machining the rotor 500 and rotor housing 400, temperature, material
properties, and other specific application requirements.
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[0110] Additionally, as discussed below, liquid is injected into the
compression chamber. By becoming entrained in the gap between the sealing
portion
510 and the rotor casing 400, the liquid can increase the effectiveness of the
dwell
seal.
[0111] As shown in Figure 31A, the rotor 500 is balanced with cut out shapes
and counterweights. Holes, some of which are marked as 550, lighten the rotor
500.
Counterweights, one of which is labeled as 560, are made of a denser material
than
the remainder of the rotor 500. The shapes of the counterweights can vary and
do not
need to cylindrical.
[0112] The rotor design provides several advantages. As shown in the
embodiment of Figure 31A, the rotor 500 includes 7 cutout holes 550 on one
side and
two counterweights 560 on the other side to allow the center of mass to match
the
center of rotation. An opening 530 includes space for the drive shaft and a
key. This
weight distribution is designed to achieve balanced, concentric motion. The
number
and location of cutouts and counterweights may be changed depending on
structural
integrity, weight distribution, and balanced rotation parameters.
[0113] The cross-sectional shape of the rotor 500 allows for concentric
rotation about the drive shaft's axis of rotation, a dwell seal 510 portion,
and open
space on the non-sealing side for increased gas volume for compression.
Concentric
rotation provides for rotation about the drive shaft's principal axis of
rotation and thus
smoother motion and reduced noise.
[0114] An alternative rotor design 502 is shown in Figure 31B. In this
embodiment, a different arc of curvature is implemented utilizing three holes
550 and
a circular opening 530. Another alternative design 504 is shown in Figure 31C.
Here,
a solid rotor shape is used and a larger hole 530 (for a larger drive shaft)
is
implemented. Yet another alternative rotor design 506 is shown in Figure 31D
incorporating an asymmetrical shape, which would smooth the volume reduction
curve, allowing for increased time for heat transfer to occur at higher
pressures.
Alternative rotor shapes may be implemented for different curvatures or needs
for
increased volume in the compression chamber.
[0115] The rotor surface may be smooth in embodiments with contacting tip
seals to minimize wear on the tip seal. In alternative embodiments, it may be
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CA 3014822 2018-08-20
advantageous to put surface texture on the rotor to create turbulence that may
improve
the performance of non-contacting seals. In other embodiments, the rotor
casing's
interior cylindrical wall may further be textured to produce additional
turbulence, both
for sealing and heat transfer benefits. This texturing could be achieved
through
machining of the parts or by utilizing a surface coating. Another method of
achieving
the texture would be through blasting with a waterjet, sandblast, or similar
device to
create an irregular surface.
[0116] The main casing 110 may further utilize a removable cylinder liner.
This liner may feature microsurfacing to induce turbulence for the benefits
noted
above. The liner may also act as a wear surface to increase the reliability of
the rotor
and casing. The removable liner could be replaced at regular intervals as part
of a
recommended maintenance schedule. The rotor may also include a liner.
[0117] The exterior of the main casing 110 may also be modified to meet
application specific parameters. For example, in subsea applications, the
casing may
require to be significantly thickened to withstand exterior pressure, or
placed within a
secondary pressure vessel. Other applications may benefit from the exterior of
the
casing having a rectangular or square profile to facilitate mounting exterior
objects or
stacking multiple compressors. Liquid may be circulated in the casing interior
to
achieve additional heat transfer or to equalize pressure in the case of subsea
applications for example.
[0118] As shown in Figure 32A and B, the combination of the rotor 500 (here
depicted with rotor end caps 590), the gate 600, and drive shaft 140, provide
for a
more efficient manner of compressing fluids in a cylinder. The gate is aligned
along
the length of the rotor to separate and define the inlet portion and
compression portion
as the rotor turns.
[0119] The drive shaft 140 is mounted to endplates 120 in the preferred
embodiment using one spherical roller bearing in each endplate 120. More than
one
bearing may be used in each endplate 120, in order to increase total load
capacity. A
grease pump (not shown) is used to provide lubrication to the bearings.
Various types
of other bearings may be utilized depending on application specific
parameters,
including roller bearings, ball bearings, needle bearings, conical bearings,
cylindrical
bearings, journal bearings, etc. Different lubrication systems using grease,
oil, or
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other lubricants may also be used. Further, dry lubrication systems or
materials may
be used. Additionally, applications in which dynamic imbalance may occur may
benefit from multi-bearing arrangements to support stray axial loads.
[0120] Operation of gates in accordance with embodiments of the present
invention are shown in Figures 8, 17, 22, 24B, 26A-F. 27A-F, 28, 32A-B, and 33-
36.
As shown in Figures 26A-F and 27A-F, gate 600 creates a pressure boundary
between
an intake volume 412 and a compression volume 414. The intake volume 412 is in
communication with the inlet 420. The compression volume 414 is in
communication
with the outlet 430. Resembling a reciprocating, rectangular piston, the gate
600 rises
and falls in time with the turning of the rotor 500.
[0121] The gate 600 may include an optional tip seal 620 that makes contact
with the rotor 500, providing an interface between the rotor 500 and the gate
600. Tip
seal 620 consists of a strip of material at the tip of the gate 600 that rides
against rotor
500. The tip seal 620 could be made of different materials, including
polymers,
graphite, and metal, and could take a variety of geometries, such as a curved,
flat, or
angled surface. The tip seal 620 may be backed by pressurized fluid or a
spring force
provided by springs or elastomers. This provides a return force to keep the
tip seal
620 in sealing contact with the rotor 500.
[0122] Different types of contacting tips may be used with the gate 600. As
shown in Figure 35, a roller tip 650 may be used. The roller tip 650 rotates
as it
makes contact with the turning rotor 500. Also, tips of differing strengths
may be
used. For example, a tip seal 620 or roller tip 650 may be made of softer
metal that
would gradually wear down before the rotor 500 surfaces would wear.
[0123] Alternatively, a non-contacting seal may be used. Accordingly, the tip
seal may be omitted. In these embodiments, the topmost portion of the gate 600
is
placed proximate, but not necessarily in contact with, the rotor 500 as it
turns. The
amount of allowable gap may be adjusted depending on application parameters.
[0124] As shown in Figures 34A and 34B, in an embodiment in which the tip
of the gate 600 does not contact the rotor 500, the tip may include notches
640 that
serve to keep gas pocketed against the tip of the gate 600. The entrained
fluid, in
either gas or liquid form, assists in providing a non-contacting seal. As one
of
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CA 3014822 2018-08-20
ordinary skill in the art would appreciate, the number and size of the notches
is a
matter of design choice dependent on the compressor specifications.
[0125] Alternatively, liquid may be injected from the gate itself. As shown in
Figure 36, a cross-sectional view of a portion of a gate, one or more channels
660
from which a fluid may pass may be built into the gate. In one such
embodiment, a
liquid can pass through a plurality of channels 660 to form a liquid seal
between the
topmost portion of the gate 600 and the rotor 500 as it turns. In another
embodiment,
residual compressed fluid may be inserted through one or more channels 660.
Further
still, the gate 600 may be shaped to match the curvature of portions of the
rotor 500 to
minimize the gap between the gate 600 and the rotor 500.
[0126] Preferred embodiments enclose the gate in a gate casing. As shown in
Figures 8 and 17, the gate 600 is encompassed by the gate casing 150,
including
notches, one of which is shown as item 158. The notches hold the gate seals,
which
ensure that the compressed fluid will not release from the compression volume
414
through the interface between gate 600 and gate casing 150 as gate 600 moves
up and
down. The gate seals may be made of various materials, including polymers,
graphite
or metal. A variety of different geometries may be used for these seals.
Various
embodiments could utilize different notch geometries, including ones in which
the
notches may pass through the gate casing, in part or in full.
[0127] The seals may use energizing forces Provided by springs or elastomers
with the assembly of the gate casing 150 inducing compression on the seals.
Pressurized fluid may also be used to energize the seals.
[0128] A rotor face seal may also be placed on the rotor 500 to provide for an
interface between the rotor 500 and the endplates 120. An outer rotor face
seal is
placed along the exterior edge of the rotor 500, preventing fluid from
escaping past
the end of the rotor 500. A secondary inner rotor face seal is placed on the
rotor face
at a smaller radius to prevent any fluid that escapes past the outer rotor
face seal from
escaping the compressor entirely. This seal may use the same or other
materials as
the gate seal. Various geometries may be used to optimize the effectiveness of
the
seals. These seals may use energizing forces provided by springs, elastomers
or
pressurized fluid.
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CA 3014822 2018-08-20
[0129] Minimizing the possibility of fluids leaking to the exterior of the
main
housing 100 is desirable. Various seals, such as gaskets and o-rings, are used
to seal
external connections between parts. For example, in a preferred embodiment, a
double o-ring seal is used between the main casing 110 and endplates 120.
Further
seals are utilized around the drive shaft 140 to prevent leakage of any fluids
making it
past the rotor face seals. A lip seal is used to seal the drive shaft 140
where it passes
through the endplates 120. Other forms of seals could also be used, such as
mechanical or labyrinth seals.
[0130] It is desirable to achieve near isothermal compression. To provide
cooling during the compression process, liquid injection is used. In preferred
embodiments, the liquid is atomized to provide increased surface area for heat
absorption. In other embodiments, different spray applications or other means
of
injecting liquids may be used.
[0131] Liquid injection is used to cool the fluid as it is compressed,
increasing
the efficiency of the compression process. Cooling allows most of the input
energy to
be used for compression rather than heat generation in the gas. The liquid has
dramatically superior heat absorption characteristics compared to gas,
allowing the
liquid to absorb heat and minimize temperature increase of the working fluid,
achieving near isothermal compression. As shown in Figures 8 and 17, liquid
injector
assemblies 130 are attached to the main casing 110. Liquid injector housings
132
include an adapter for the liquid source 134 (if it is not included with the
nozzle) and
a nozzle 136. Liquid is injected by way of a nozzle 136 directly into the
rotor casing
volume 410.
[0132] The amount and timing of liquid injection may be controlled by a
variety of implements including a computer-based controller capable of
measuring the
liquid drainage rate, liquid levels in the chamber, and/or any rotational
resistance due
to liquid accumulation through a variety of sensors. Valves or solenoids may
be used
in conjunction with the nozzles to selectively control injection timing.
Variable
orifice control may also be used to regulate the amount of liquid injection
and other
characteristics.
[0133] Analytical and experimental results are used to optimize the number,
location, and spray direction of the injectors 136. These injectors 136 may be
located
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in the periphery of the cylinder. Liquid injection may also occur through the
rotor or
gate. The current embodiment of the design has two nozzles located at 12
o'clock and
o'clock. Different application parameters will also influence preferred nozzle
arrays.
5 [0134] The nozzle array is designed for a high flow rate of greater
than 5
gallons per minute and to be capable of extremely small droplet sizes of 150
microns
or less at a low differential pressure of less than 100 psi. Two exemplary
nozzles are
Spraying Systems Co. Part Number: 1/4HHSJ-SS12007 and Bex Spray Nozzles Part
Number: 1/4YS12007. The preferred flow rate and droplet size ranges will vary
with
10 application parameters. Alternative nozzle styles may also be used. For
example, one
embodiment may use micro-perforations in the cylinder through which to inject
liquid, counting on the small size of the holes to create sufficiently small
droplets.
Other embodiments may include various off the shelf or custom designed nozzles
which, when combined into an array, meet the injection requirements necessary
for a
given application.
[0135] As discussed above, the rate of heat transfer is improved by using such
atomizing nozzles to inject very small droplets of liquid into the compression
chamber. Because the rate of heat transfer is proportional to the surface area
of liquid
across which heat transfer can occur, the creation of smaller droplets
improves
cooling. Numerous cooling liquids may be used. For example, water, triethylene
glycol, and various types of oils and other hydrocarbons may be used. Ethylene
glycol, propylene glycol, methanol or other alcohols in case phase change
characteristics are desired may be used. Refrigerant:- such as ammonia and
others
may also be used. Further, various additives may be combined with the cooling
liquid
to achieve desired characteristics. Along with the heat transfer and heat
absorption
properties of the liquid helping to cool the compression process, vaporization
of the
liquid may also be utilized in some embodiments of the design to take
advantage of
the large cooling effect due to phase change.
[0136] The effect of liquid coalescence is also addressed in the preferred
embodiments. Liquid accumulation can provide resistance against the
compressing
mechanism, eventually resulting in hydrolock in which all motion of the
compressor
is stopped, causing potentially irreparable harm. As is shown in the
embodiments of
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Figures 8 and 17, the inlet 420 and outlet 430 are located at the bottom of
the rotor
casing 400 on opposite sides of the gate 600, thus providing an efficient
location for
both intake of fluid to be compressed and exhausting of compressed fluid and
the
injected liquid. A valve is not necessary at the inlet 420. The inclusion of a
dwell
seal allows the inlet 420 to be an open port, simplifying the system and
reducing
inefficiencies associated with inlet valves. However, if desirable, an inlet
valve could
also be incorporated. Additional features may be added at the inlet to induce
turbulence to provide enhanced thermal transfer and other benefits. Hardened
materials may be used at the inlet and other locations of the compressor to
protect
against cavitation when liquid/gas mixtures enter into choke and other
cavitation-
inducing conditions.
[0137] Alternative embodiments may include an inlet located at positions
other than shown in the figures. Additionally, multiple inlets may be located
along
the periphery of the cylinder. These could be utilized in isolation or
combination to
accommodate inlet streams of varying pressures and flow rates. The inlet ports
can
also be enlarged or moved, either automatically or manually, to vary the
displacement
of the compressor.
[0138] In these embodiments, multi-phase compression is utilized, thus the
outlet system allows for the passage of both gas and liquid. Placement of
outlet 430
near the bottom of the rotor casing 400 provides for a drain for the liquid.
This
minimizes the risk of hydrolock found in other liquid injection compressors. A
small
clearance volume allows any liquids that remain within the chamber to be
accommodated. Gravity assists in collecting and eliminating the excess liquid,
preventing liquid accumulation over subsequent cycles. Additionally, the
sweeping
motion of the rotor helps to ensure that most liquid is removed from the
compressor
during each compression cycle.
[0139] Outlet valves allow gas and liquid to flow out of the compressor once
the desired pressure within the compression chamber is reached. Due to the
presence
of liquid in the working fluid, valves that minimize or eliminate changes in
direction
for the outflowing working fluid are desirable. This prevents the hammering
effect of
liquids as they change direction. Additionally, it is desirable to minimize
clearance
volume.
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CA 3014822 2018-08-20
[0140] Reed valves may be desirable as outlet valves. As one of ordinary skill
in the art would appreciate, other types of valves known or as yet unknown may
be
utilized. Hoerbiger type R, CO, and Reed valves may be acceptable.
Additionally,
CT, HDS, CE, CM or Poppet valves may be considered. Other embodiments may use
valves in other locations in the casing that allow gas to exit once the gas
has reached a
given pressure. In such embodiments, various styles of valves may be used.
Passive
or directly-actuated valves may be used and valve controllers may also be
implemented.
[0141] In the presently preferred embodiments, the outlet valves are located
near the bottom of the casing and serve to allow exhausting of liquid and
compressed
gas from the high pressure portion. In other embodiments, it may be useful to
provide
additional outlet valves located along periphery of main casing in locations
other than
near the bottom. Some embodiments may also benefit from outlets placed on the
endplates. In still other embodiments, it may be desirable to separate the
outlet valves
into two types of valves¨ one predominately for high pressured gas, the other
for
liquid drainage. In these embodiments, the two or more types of valves may be
located near each other, or in different locations.
[0142] As shown in Figures 8 and 17, the sealing portion 510 of the rotor
effectively precludes fluid communication between the outlet and inlet ports
by way
of the creation of a dwell seal. The interface between the rotor 500 and gate
600
further precludes fluid communication between the outlet and inlet ports
through use
of a non-contacting seal or tip seal 620. In this way, the compressor is able
to prevent
any return and venting of fluid even when running at low speeds. Existing
rotary
compressors, when running at low speeds, have a leakage path from the outlet
to the
inlet and thus depend on the speed of rotation to minimize venting/leakage
losses
through this flowpath.
[0143] The high pressure working fluid exerts a large horizontal force on the
gate 600. Despite the rigidity of the gate struts 210, this force will cause
the gate 600
to bend and press against the inlet side of the gate casing 152. Specialized
coatings
that are very hard and have low coefficients of friction can coat both
surfaces to
minimize friction and wear from the sliding of the gate 600 against the gate
casing
152. A fluid bearing can also be utilized. Alternatively, pegs (not shown) can
extend
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from the side of the gate 600 into gate casing 150 to help support the gate
600 against
this horizontal force.
[0144] The large horizontal forces encountered by the gate may also require
additional considerations to reduce sliding friction of the gate's
reciprocating motion.
Various types of lubricants, such as greases or oils may be used. These
lubricants
may further be pressurized to help resist the force pressing the gate against
the gate
casing. Components may also provide a passive source of lubrication for
sliding parts
via lubricant-impregnated or self-lubricating materials. In the absence of, or
in
conjunction with, lubrication, replaceable wear elements may be used on
sliding parts
to ensure reliable operation contingent on adherence to maintenance schedules.
As
one of ordinary skill in the art would appreciate, replaceable wear elements
may also
be utilized on various other wear surfaces within the compressor.
[0145] The compressor structure may be comprised of materials such as
aluminum, carbon steel, stainless steel, titanium, tungsten, or brass.
Materials may be
chosen based on corrosion resistance, strength, density, and cost. Seals may
be
comprised of polymers, such as PTFE, HDPE, PEEKTM, acetal copolymer, etc.,
graphite, cast iron, or ceramics. Other materials known or unknown may be
utilized.
Coatings may also be used to enhance material properties.
[0146] As one of ordinary skill in the art can appreciate, various techniques
may be utilized to manufacture and assemble the invention that may affect
specific
features of the design. For example, the main casing 110 may be manufactured
using
a casting process. In this scenario, the nozzle housings 132, gate casing 150,
or other
components may be formed in singularity with the main casing 110. Similarly,
the
rotor 500 and drive shaft 140 may be built as a single piece, either due to
strength
requirements or chosen manufacturing technique.
[0147] Further benefits may be achieved by utilizing elements exterior to the
compressor envelope. A flywheel may be added to the drive shaft 140 to smooth
the
torque curve encountered during the rotation. A flywheel or other exterior
shaft
attachment may also be used to help achieve balanced rotation. Applications
requiring multiple compressors may combine multiple compressors on a single
drive
shaft with rotors mounted out of phase to also achieve a smoothened torque
curve. A
bell housing or other shaft coupling may be used to attach the drive shaft to
a driving
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force such as engine or electric motor to minimize effects of misalignment and
increase torque transfer efficiency. Accessory components such as pumps or
generators may be driven by the drive shaft using belts, direct couplings,
gears, or
other transmission mechanisms. Timing gears or belts may further be utilized
to
synchronize accessory components where appropriate.
[0148] After exiting the valves the mix of liquid and gases may be separated
through any of the following methods or a combination thereof: I. Interception
through the use of a mesh, vanes, intertwined fibers; 2. Inertial impaction
against a
surface; 3. Coalescence against other larger injected droplets; 4. Passing
through a
liquid curtain; 5. Bubbling through a liquid reservoir; 6. Brownian motion to
aid in
coalescence; 7. Change in direction; 8. Centrifugal motion for coalescence
into walls
and other structures; 9. Inertia change by rapid deceleration; and 10.
Dehydration
through the use of adsorbents or absorbents.
[0149] At the outlet of the compressor, a pulsation chamber may consist of
cylindrical bottles or other cavities and elements, may be combined with any
of the
aforementioned separation methods to achieve pulsation dampening and
attenuation
as well as primary or final liquid coalescence. Other methods of separating
the liquid
and gases may be used as well.
[0150] The presently preferred embodiments could be modified to operate as
an expander. Further, although descriptions have been used to describe the top
and
bottom and other directions, the orientation of the elements (e.g. the gate
600 at the
bottom of the rotor casing 400) should not be interpreted as limitations on
the present
invention.
[0151] While the foregoing written description of the invention enables one of
ordinary skill to make and use what is considered presently to be the best
mode
thereof, those of ordinary skill will understand and appreciate the existence
of
variations, combinations, and equivalents of the specific embodiment, method,
and
examples herein. The invention should therefore not be limited by the above
described embodiment, method, and examples, but by all embodiments and methods
within the scope and spirit of the invention.
[0152] It is therefore intended that the foregoing detailed description be
regarded as illustrative rather than limiting, and that it be understood that
it is the
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following claims, including all equivalents, that are intended to define the
spirit and
scope of this invention. To the extent that "at least cne" is used to
highlight the
possibility of a plurality of elements that may satisfy a claim element, this
should not
be interpreted as requiring "a" to mean singular only. "A" or "an" element may
still
be satisfied by a plurality of elements unless otherwise stated.
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