U.S. patent application number 11/749600 was filed with the patent office on 2008-11-20 for submersible pumping systems and methods for deep well applications.
Invention is credited to Joseph L. Leonard, Steven Regalado.
Application Number | 20080286134 11/749600 |
Document ID | / |
Family ID | 40027673 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080286134 |
Kind Code |
A1 |
Regalado; Steven ; et
al. |
November 20, 2008 |
SUBMERSIBLE PUMPING SYSTEMS AND METHODS FOR DEEP WELL
APPLICATIONS
Abstract
Submersible pumping systems, devices and methods for extracting
liquids in deep well applications are disclosed. In the various
embodiments, a submersible pumping system includes a power supply
and a power converter coupled to the power supply. A subsurface
unit may be coupled to the power converter and positioned in the
well. The subsurface unit may include a subsurface controller, a
motor and a pump portion operably coupled to the subsurface
controller. The pump portion may further include a front shroud
having an inlet, and a back shroud sealably coupled to the front
shroud to define a volume. An orifice fluidly communicates with the
volume and an annular fluid discharge space disposed about the
subsurface unit. An impeller operably coupled to the motor and
positioned within the volume may transport a liquid from the inlet
to the annular fluid discharge space.
Inventors: |
Regalado; Steven;
(Westminster, CO) ; Leonard; Joseph L.; (Arvada,
CO) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG & WOESSNER, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Family ID: |
40027673 |
Appl. No.: |
11/749600 |
Filed: |
May 16, 2007 |
Current U.S.
Class: |
417/423.3 ;
166/105; 417/390; 417/409 |
Current CPC
Class: |
F04D 13/10 20130101 |
Class at
Publication: |
417/423.3 ;
166/105; 417/390; 417/409 |
International
Class: |
F04B 23/14 20060101
F04B023/14 |
Claims
1. A submersible pumping system for a well, comprising: a power
supply; a power converter coupled to the power supply; and a
subsurface unit coupled to the power converter and configured to be
positioned in the well remote from the power supply and the power
converter, wherein the subsurface unit includes a subsurface
controller, and a motor and a pump portion operably coupled to the
subsurface controller, the pump portion further comprising: a front
shroud having an inlet; a back shroud sealably coupled to the front
shroud to define a volume there between; an orifice that fluidly
communicates with the volume and an annular fluid discharge space
at least partially disposed about the subsurface unit; and an
impeller operably coupled to the motor and positioned within the
volume to transport a liquid from the inlet to the annular fluid
discharge space.
2. The system of claim 1, wherein the front shroud includes an
axially disposed conical inner portion having a taper angle that
ranges between approximately 45 degrees and approximately 60
degrees.
3. The system of claim 1, wherein the front shroud comprises a
strainer fluidly coupled to the inlet that is configured to
restrict the entry of solid material into the volume.
4. The system of claim 1, wherein the orifice comprises a constant
diameter portion and a tapered portion coupled to the constant
diameter portion, the tapered portion having an included angle that
ranges between approximately five degrees, and approximately 50
degrees.
5. The system of claim 4, wherein the constant diameter portion
comprises a diameter that ranges between approximately 0.030
inches, and approximately 0.120 inches.
6. The system of claim 1, wherein the impeller comprises a planar
and circular disk that supports a plurality of outwardly extending
vanes, and a centrally disposed impeller hub configured to be
coupled to the motor.
7. The system of claim 6, wherein the disk comprises a plurality of
apertures extending through the disk and positioned between the
outwardly extending vanes.
8. The system of claim 6, wherein the outwardly extending vanes are
spaced apart from the front shroud by a clearance distance that
ranges between approximately 0.005 inch and approximately 0.040
inch.
9. The system of claim 6, wherein the outwardly extending vanes are
inclined at an angle that ranges between approximately 45 degrees
and approximately 60 degrees.
10. The system of claim 6, wherein the impeller hub is configured
to fixedly retain a shaft extending from the motor using an
interference fit.
11. The system of claim 1, wherein the motor comprises a polyphase,
brushless and sensor less DC motor.
12. A submersible pumping system for a well, comprising: a power
supply; a power converter coupled to the power supply; and a
subsurface unit coupled to the power converter and configured to be
positioned in the well remote from the power supply and the power
converter, wherein the subsurface unit includes a pump portion and
a motor operably coupled to the pump portion, and a subsurface
controller, the subsurface controller further comprising: a power
compensation circuit operable to receive electrical power from the
power converter configured to reduce at least one of a reactance
introduced by the motor and reactive and resistive effects
introduced by electrical leads coupling the power converter to the
subsurface unit; a motor controller coupled to the power
compensation circuit that is configured to convert electrical power
received from the power compensation circuit to polyphase
electrical power that is communicated to the motor; and a motor
speed controller configured to control a rotational speed of the
motor when the polyphase electrical power is first applied to the
motor.
13. The system of claim 12, wherein the power supply comprises one
of an alternating current (AC) source and a direct current (DC)
source.
14. The system of claim 13, wherein the DC source comprises one of
a storage battery, one or more photovoltaic panels, and a fuel cell
device.
15. The system of claim 13, wherein the power converter comprises a
DC-to DC converter configured to receive a DC voltage at a first
voltage level, and convert the DC voltage to a second voltage
level.
16. The system of claim 15, wherein the DC-to-DC converter
comprises one of a buck-boost converter, a boost converter and a
buck converter.
17. The system of claim 15, wherein the DC-to-DC converter is
coupled to an AC-to-DC converter that receives an AC voltage from
the power supply, and converts the AC voltage to a DC voltage.
18. The system of claim 12, wherein the power compensation circuit
comprises one or more capacitors operably coupled to the power
converter and the motor controller.
19. The system of claim 12, wherein the motor controller comprises
at least one inverter circuit configured to receive a DC voltage,
and to convert the DC voltage to an AC voltage.
20. The system of claim 12, wherein the motor controller comprises
a speed sensing circuit that is operable to sense a back
electromotive force from the motor and to regulate a speed of the
motor based upon the sensed electromotive force.
21. The system of claim 12, wherein the motor speed controller is
configured to provide a motor speed distribution that is
implemented during a time period that extends from a motor start
value to a maximum speed value.
22. The system of claim 21, wherein the time period is
approximately one to three seconds.
23. The system of claim 21, wherein the motor speed distribution
extends linearly during the time period.
24. The system of claim 21, wherein the motor speed distribution
comprises one of a second-degree speed distribution and a
third-degree speed distribution.
25. A submersible pumping system for a well, comprising: a power
supply; a feedback system coupled to the power supply; and a
subsurface unit coupled to the feedback system and configured to be
positioned in the well remote from the power supply and the
feedback system, wherein the subsurface unit includes at least a
pump portion and a motor operably coupled to the pump portion, the
pump portion being operable to transport a volume of a liquid from
the well to a flow meter, the feedback system further comprising: a
control mode unit configured to implement a predetermined control
mode; a power converter coupled to the control mode unit that is
configured to receive electrical power from the power supply, and
to controllably provide electrical power to the subsurface unit
based upon an out\put from the control mode unit; and a comparator
that receives a feedback signal from the flow meter that provides
an error signal to the control mode unit based upon a comparison of
the feedback signal and a desired flow value.
26. The system of claim 25, wherein the control mode unit is
configured to implement one of a proportional (P) control mode, a
derivative (D) control mode, a proportional-derivative (P-D)
control mode, an integral (I) control mode, a proportional-integral
(P-I) control mode, and a proportional-integral-derivative (P-I-D)
control mode.
27. The system of claim 25, wherein the power converter comprises a
DC-to DC converter configured to receive a DC voltage at a first
voltage level, and convert the DC voltage to a second voltage
level.
28. The system of claim 27, wherein the DC-to-DC converter
comprises one of a buck-boost converter, a boost converter and a
buck converter.
29. The system of claim 25, wherein the DC-to-DC converter is
coupled to an AC-to-DC converter that receives an AC voltage from
the power supply, and converts the AC voltage to a DC voltage.
30. The system of claim 29, wherein the AC-to-DC converter
comprises a rectifier circuit.
31. A method of removing a liquid from a well, comprising:
positioning a subsurface unit into a well, the subsurface unit
including at least a pump portion coupled to a motor configured to
impart a rotational motion to the pump portion; coupling the
subsurface unit to a power supply and a power converter configured
to controllably provide electrical power to the subsurface unit;
and starting the motor using a selected motor speed
distribution.
32. The method of claim 31, wherein starting the motor using a
selected motor speed distribution comprises implementing the motor
speed distribution over a time period that ranges between
approximately one to three seconds.
33. The method of claim 31, wherein starting the motor using a
selected motor speed distribution comprises a linear motor speed
distribution.
34. The method of claim 31, wherein starting the motor using a
selected motor speed distribution comprises a parabolic motor speed
distribution.
35. The method of claim 31, wherein starting the motor using a
selected motor speed distribution comprises a motor speed
distribution conforming to a third-order polynomial.
36. The method of claim 31, further comprising: setting a desired
speed for steady-state motor operation; detecting a variation in
the steady-state motor operation by sensing a back electromotive
force from the motor; and correcting at least one of a voltage and
a current delivered to the motor to return the motor to the desired
speed.
37. The method of claim 36, wherein setting a desired speed for
steady-state motor operation comprises providing a control input to
the power converter.
38. A method of removing a liquid from a well, comprising:
positioning a subsurface unit into a well, the subsurface unit
including at least a pump portion and a motor coupled to the pump
portion, the subsurface unit being configured to transport a liquid
from the well to a surface location; coupling the subsurface unit
to a power supply and a feedback system configured to controllably
provide electrical power to the subsurface unit; selecting a
desired flow rate to be delivered by the subsurface unit; setting a
speed for the motor that delivers the desired flow rate; measuring
a delivered flow rate; and if the delivered flow rate differs from
the desired flow rate, then correcting the speed to attain the
desired flow rate.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to fluid transfer
devices and methods, and more particularly, to submersible pumping
systems, devices and methods for extracting liquids in deep well
applications.
BACKGROUND
[0002] Submersible pumps are typically employed in sub-surface
pumping applications where it is desired to remove liquids from
relatively deep well locations. A centrifugal pump is typically
employed in such applications, since it may be readily configured
to provide a relatively high pumping head while providing a desired
liquid flow rate at a surface location. Submersible centrifugal
pumps of conventional design typically include a series of
vertically stacked radial impellers in order to provide the desired
lift from the well. The impeller stack is generally rotationally
coupled to an electric motor that that may be located at the
sub-surface location, and coupled to the centrifugal pump by a
shaft that extends from the centrifugal pump to the motor.
[0003] Submersible pumps are also commonly used in well-sampling
and monitoring applications. In such applications, however, the
submersible pump must be suitably dimensioned to be removably
positioned in a bore hole of relatively small diameter (e.g.,
approximately one to four inches in diameter), while providing
acceptable performance over a wide range of well depths and flow
rates. In selected instances, the submersible pump may be operated
intermittently, so that the well is periodically sampled.
[0004] In the interest of reducing size, complexity and
manufacturing costs, centrifugal pumps in well-sampling and
monitoring applications generally employ a single impeller that is
closely coupled to an electric motor that is positioned with a
sealed enclosure. Accordingly, numerous difficulties are
encountered in the design and operation of well-sampling and
monitoring applications that are not present in larger multi-stage
devices. For example, relatively long electrical lead lengths may
introduce undesired transient electrical loading conditions that
may adversely affect the motor, the power supply, or both.
[0005] Therefore, what is needed in the art are submersible pumping
systems, apparatuses and methods that extracting liquids in deep
well applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The various embodiments of the present invention are
described in detail below with reference to the following
drawings.
[0007] FIG. 1 is a diagrammatic block view of a submersible pumping
system, according to the various embodiments.
[0008] FIG. 2 is a diagrammatic block view of another submersible
pumping system, according to the various embodiments.
[0009] FIG. 3 is a diagrammatic block view of a power converter
according to the various embodiments.
[0010] FIG. 4 is a diagrammatic block view of another power
converter according to the various embodiments.
[0011] FIG. 5 is a diagrammatic block view of a feedback system
according to the various embodiments, which will be used to further
describe the closed feedback loop previously discussed in
connection with FIG. 2.
[0012] FIG. 6 is a diagrammatic block view of a subsurface unit
according to the various embodiments.
[0013] FIG. 7 is a diagrammatic block view of a subsurface
controller according to the various embodiments.
[0014] FIG. 8 is a graphical representation of a motor speed
distribution according to the various embodiments.
[0015] FIG. 9 is a partial cross sectional view of a subsurface
unit according to the various embodiments.
[0016] FIG. 10 is a frontal plan view of the front shroud of the
centrifugal pump of FIG. 9.
[0017] FIG. 11 is a cross sectional view of the front shroud of
FIG. 10.
[0018] FIG. 12 is a rear plan view of the front shroud of FIG.
10.
[0019] FIG. 13 is an expanded, partial cross sectional view of the
front shroud of FIG. 10.
[0020] FIG. 14 is a frontal plan view of the impeller of FIG.
9.
[0021] FIG. 15 is a cross sectional view of the impeller of FIG.
14.
[0022] FIG. 16 is a frontal plan view of the back shroud of FIG.
9.
[0023] FIG. 17 is a cross sectional view of the back shroud of FIG.
16.
[0024] FIG. 18 is a flowchart that describes a method of removing a
liquid from a well, according to the various embodiments.
[0025] FIG. 19 is a flowchart that describes a method of removing a
liquid from a well, according to the various embodiments.
DETAILED DESCRIPTION
[0026] The present invention relates to submersible pumping
systems, devices and methods for extraction of liquids in deep well
applications. Many specific details of the various embodiments are
set forth in the following description and in FIGS. 1 through 19 to
provide a thorough understanding of such embodiments. One skilled
in the art, however, will understand that the present invention may
have additional embodiments, and that many of the various
embodiments may be practiced without several of the details
described in the following description.
[0027] FIG. 1 is a diagrammatic block view of a submersible pumping
system 10, according to the various embodiments. The system 10
includes a subsurface unit 12 that is configured to be lowered into
a bore hole 14 and to be at least partially immersed into a liquid
16 that is present in a lower portion of the bore hole 14. The
subsurface unit 12 further includes a pump portion 18, a motor 20
that is operably coupled to the pump portion 18, and a subsurface
controller 22 that is operable to control the motor 20. Briefly,
and in general terms, the pump portion 18, the motor 20 and the
subsurface controller 22 cooperatively permit the liquid 16 located
in the lower portion of the bore hole 14 to be transferred to a
position proximate to a ground surface location 24 through a liquid
discharge conduit 26. The pump portion 18, the motor 20 and the
subsurface controller 22 will be described in greater detail
below.
[0028] The system 10 further includes a power supply 28 that is
coupled to a power converter 30 that is, in turn, coupled by
electrical leads 29 to the subsurface unit 12 to provide electrical
energy to the unit 12. The power supply 28 may include any suitable
alternating current (AC) or direct current (DC) source. For
example, the power supply 28 may include a DC source, such as a
storage battery, or an AC source, such as a conventional AC power
distribution system. In other of the various embodiments, the power
supply 28 may include an energy source that is suitable to supply
either AC or DC power to the power converter 30 and the subsurface
unit 12 when the system 10 is positioned at a remote location that
disfavors the use of a storage batteries, and where conventional AC
power is not available. For example, the power supply 28 may
include an electrical generator that is coupled to a prime mover,
such as an internal combustion engine, to provide either AC or DC
power to the power converter 30. The power supply 28 may also
include a wind turbine that is structured to generate rotational
motion from atmospheric winds, and to impart the rotational motion
to a generator that provides either AC or DC power. In still other
of the various embodiments, the power supply 28 may include one or
more photovoltaic panels that are structured to receive
illumination (e.g., solar illumination) and convert the received
illumination to an electrical current. In still other embodiments,
power sources based upon electrochemical energy conversion may be
used, such as a fuel cell, or other similar devices.
[0029] Still referring to FIG. 1, the power converter 30 is
suitably configured to receive either AC or DC power from the power
supply 28, and to suitably transform the received power to obtain a
desired performance from the subsurface unit 12. For example, the
power converter 30 may be configured to controllably alter a
voltage or a current transferred to the subsurface unit 12 so that
a desired flow rate is delivered through the liquid discharge
conduit 26. Accordingly, the power converter 30 may be coupled to a
control input 32 that is operable to set a voltage or current so
that the desired flow rate is achieved. The control input 32 may be
provided by an analog input, such as an analog voltage or current
level, which may be manually set (e.g., by altering a potentiometer
setting), or it may be a digital input, that may be provided by an
external digital device (e.g., a digital computer) operably coupled
to the power converter 30. In still another of the various
embodiments, the control input 32 may be configured to control an
operational time for the subsurface unit 12, so that the unit 12
may be intermittently operated. For example, the control input 32
may provide that the unit 12 is operated at predetermined times,
which may be non-periodic, or periodic. Additionally, the control
input 32 may provide for different flow rates during different
operational periods. The power converter 30 will be described in
greater detail below.
[0030] FIG. 2 is a diagrammatic block view of another submersible
pumping system 40, according to the various embodiments. Many of
the details shown in FIG. 2 have been previously described in
detail, and in the interest of brevity, will not be discussed
further. The system 40 includes a feedback system 42 (that includes
a power converter, as previously described) that may be suitably
coupled to a flow meter 44 so that signals received from the flow
meter 44 may be used to at least partially control a flow rate
delivered by the subsurface unit 12. The feedback system 42 and the
flow meter 44 advantageously comprise a closed feedback loop that
may cooperatively provide a relatively uniform flow rate from the
subsurface unit 12. A suitable closed feedback system according to
the various embodiments will be discussed in greater detail
below.
[0031] With reference now to FIG. 3, a power converter 50 according
to the various embodiments will now be discussed in detail. The
power converter 50 includes a DC-to-DC converter 52 that is
configured to be coupled to a DC power supply at input terminals
54, and to provide a selected DC output at output terminals 56. The
DC-to-DC converter 52 may include a "buck-boost" device that is
structured to accept an approximately constant input voltage
V.sub.DC, IN and to provide a variable output voltage V.sub.DC, OUT
that may range above or below the input voltage V.sub.DC, IN. For
example, if the input voltage V.sub.DC, IN is approximately about
12 volts, DC, then the DC-to-DC converter 50 may provide a
V.sub.DC, OUT that ranges between approximately about 0 volts, DC
and approximately about 60 volts, DC. In another of the various
embodiments, the DC-to-DC converter 50 may be a "boost" converter
that is structured to accept an approximately constant input
voltage V.sub.DC, IN and to provide a variable output voltage
V.sub.DC, OUT that is greater than the input voltage V.sub.DC, IN.
For example, if the input voltage V.sub.DC, IN is approximately
about 12 volts, DC, then the DC-to-DC converter 50 may provide a
V.sub.DC, OUT that ranges between approximately about 12 volts, DC
and approximately about 60 volts, DC. In either case, the DC-to-DC
converter 50 may be coupled to an input circuit 58 that is
configured to receive the control input 32 and to provide a
suitable output to the converter 50 so that a desired output
voltage V.sub.DC, OUT is provided.
[0032] The power converter 50 may also include an indication unit
60 that is operable to measure the output voltage V.sub.DC, OUT,
and to display the value on a visual display 62. In another of the
various embodiments, the indication unit may be configured to
measure a current value delivered to the output terminals 56. In
still another of the various embodiments, the indication unit 60
may be configured to measure an electrical power value delivered to
the output terminals 56. In another of the various embodiments, the
indication unit 60 may be configured to display a liquid flow
rate.
[0033] FIG. 4 is a diagrammatic block view of another power
converter 70 according to the various embodiments. Again, many of
the details shown in FIG. 4 have been previously described in
detail, and in the interest of brevity, will not be discussed
further. The power converter 70 is configured to be coupled to an
AC source 72, having an RMS input voltage V.sub.AC, IN. The AC
source 72 may include a single phase source, or it may include a
polyphase source. In either case, the AC source 72 may be coupled
to an AC-to-DC converter 74 that is operable to convert a voltage
received from the AC source 72 to a suitable DC voltage level. The
AC-to-DC converter 74 may include, for example, a rectifier
assembly. Although not shown in FIG. 4, if the AC source 72 is a
polyphase source, the converter 74 may include conversion
components (e.g., a rectifier assembly) that are arranged in
parallel for the conversion of each phase.
[0034] The AC-to-DC converter 74 may be coupled to a DC-to-DC
converter 52, as previously described. When the input voltage
V.sub.AC, IN includes one of a 120 v and a 208 v AC source, the
DC-to-DC converter which may include a "buck" converter, so that
the output voltage V.sub.DC, OUT is reduced to a suitable level. In
other embodiments, a boost converter, or a buck-boost converter may
also be used.
[0035] FIG. 5 is a diagrammatic block view of a feedback system 80
according to the various embodiments, which will be used to further
describe the closed feedback loop previously discussed in
connection with FIG. 2. The system 80 includes a feedback unit 82
that further includes a comparator unit 84 that is coupled to a
control mode unit 86. The comparator 84 is operable to receive the
control input 32 and to receive a feedback input 88, and to
generate an error signal e based upon a comparison of the received
control input 32 and the feedback input 88. The feedback input 88
is received from the flow meter 44, that generates the feedback
input 88 in response to a liquid flow 91 delivered by the
subsurface unit 12 (as shown in FIG. 1 or FIG. 2). The error signal
e may then be transferred to a control mode unit 86 that is
configured to implement a specified control mode for the system 80.
For example, the control mode may include one of a proportional (P)
control mode, a derivative (D) control mode, a
proportional-derivative (P-D) control mode, an integral (I) control
mode, a proportional-integral (P-I) control mode, and a
proportional-integral-derivative (P-I-D) control mode. Accordingly,
the feedback unit 82 is operable to provide a suitably-corrected
input value to a power converter 89, which may include one of the
various embodiments shown in FIG. 3 and FIG. 4. One skilled in the
art will readily appreciate that various components of the feedback
unit 82 (e.g., the comparator 84 and the control mode unit 86) may
be implemented using either analog or digital circuits, and may be
further implemented in firmware, or entirely in software.
[0036] With reference now to FIG. 6, a subsurface unit 90 according
to the various embodiments will now be discussed. The subsurface
unit 90 includes a centrifugal pump 92 that is configured to
fluidly communicate with a liquid 16 (as shown in FIG. 1) which may
be present in the lower portion of the bore hole 14 (also shown in
FIG. 1), and transfer the liquid 16 to the conduit 26 (also shown
in FIG. 1). The centrifugal pump 92 will be discussed in greater
detail below. The centrifugal pump 92 may be mechanically coupled
to a motor 94 to impart a torque 96 to the centrifugal pump 92. In
the various embodiments, the motor 94 may include a brushless,
sensorless, polyphase motor.
[0037] The motor 94 may be conductively coupled to a subsurface
controller 98 by a conductive assembly 100 that is structured to be
removably coupled to at least one of the motor 94 and the
subsurface controller 98. The assembly 100 may accordingly include
a plurality of parallel conductive components that are each
configured to couple a single phase to the polyphase motor 94. The
subsurface controller 98 may, in turn, be coupled to one of the
power converter 50, as shown in FIG. 3, and the power converter 70,
as shown in FIG. 4. The subsurface controller 98 may be configured
to provide polyphase power to the motor 94, provide power
compensation, control a speed of the motor 94, or otherwise
condition the polyphase power delivered to the motor 94. The
subsurface controller will be discussed in greater detail
below.
[0038] FIG. 7 is a diagrammatic block view of a subsurface
controller 110 according to the various embodiments. The subsurface
controller 110 may include a compensation circuit 112 that is
coupled to one of the power converter 50, as shown in FIG. 3, and
the power converter 70, as shown in FIG. 4. The compensation
circuit 112 may include one or more capacitors that are suitably
arranged to provide power compensation that addresses reactive
effects introduced by the polyphase motor 94 and/or reactive and
resistive effects introduced by electrical leads that couple the
power converter 50, as shown in FIG. 3, and the power converter 70,
as shown in FIG. 4, to the subsurface controller 110. Accordingly,
the compensation circuit 112 may advantageously avoid instability
in a polyphase motor controller 114 coupled to the compensation
circuit 112. The polyphase motor controller 114 may include, for
example, suitable inverter circuits to provide one or more AC
phases to the motor 94. Additionally, the motor controller 114 may
be configured to regulate a speed for the motor 94 by sensing a
back electromotive force (EMF) developed by the motor 94 when a
change in an armature speed of the motor 94 occurs. For example,
the controller 114 may be configured to detect the back EMF, and to
controllably alter at least one of a voltage and a current
delivered to the motor 94 to return the motor 94 to a desired
speed. The polyphase motor controller 114 may also be coupled to a
motor speed controller 116 that is configured to control a
rotational speed of the motor 94 when electrical power is initially
applied to the motor 94, and that extends for a period of time
until the motor reaches a full-speed value, as will be discussed in
greater detail below.
[0039] With reference now also to FIG. 8, a motor speed
distribution 120 according to the various embodiments is shown,
which may be implemented by the motor speed controller 116. In one
of the various embodiments, a motor speed distribution 122 is
approximately linear, so that the speed of the motor 94 increases
from stationary to a full speed value at a constant rate.
Accordingly, upon being energized, the motor 94 reaches a maximum
speed at a time T, which in an embodiment, may be approximately one
to three seconds. In another of the various embodiments, a motor
speed distribution 124 is approximately parabolic (e.g., a
polynomial of second degree), so that the speed of the motor 94
increases at a variable rate upon being energized. In still another
of the various embodiments, a motor speed distribution 126 may have
still other shapes, such as a third-degree polynomial, so that the
speed of the motor 94 increases at still another non-constant
rate.
[0040] FIG. 9 is a partial cross sectional view of a subsurface
unit 130 according to the various embodiments. As discussed
previously in connection with FIG. 6, a centrifugal pump 132 may be
mechanically coupled to the motor 94, which, in turn, receives
electrical power from the subsurface controller 110. The
centrifugal pump 132 includes a front shroud 134 and a back shroud
136 that are sealably coupled. The front shroud 134 may include a
strainer 133 that is configured to prevent debris from entering the
centrifugal pump 132, while the back shroud 136 may include a
suitable shaft seal 135 to sealably restrict the liquid from
contacting the motor 94. The front shroud 134 and the back shroud
136 cooperatively define a volume 140 that encloses an impeller 138
that is mechanically coupled to the motor 94. The volume 140
fluidly communicates with an orifice 142 that is configured to
expel a liquid confined within the volume 140 when a torque is
imparted to the impeller 138 by the motor 94. Various details of
the centrifugal pump 132 will be discussed in greater detail
below.
[0041] The subsurface unit 130 further includes a generally
cylindrical inner housing 144 that may be sealably coupled to the
back shroud 136, which may also be sealably coupled to an end cap
146. Accordingly, the back shroud 136, the inner housing 144 and
the end cap 146 may cooperatively form a hermetically-sealed volume
148 that contains the motor 94 and the subsurface controller 110. A
generally cylindrical outer housing 150 may be sealably coupled to
the front shroud 134 and to the end cap 146 to define a generally
annular fluid discharge space 152 between the inner housing 144 and
the outer housing 150. The fluid discharge space 152 fluidly
communicates with a fluid passage 154 formed in the end cap 146,
that may further fluidly communicate with the liquid discharge
conduit 26 through a suitable end fitting 156. The end cap 146 may
also include suitable electrical feedthroughs 158 that permit the
subsurface controller 110 and the motor 94 to be electrically
coupled to one of the converters 50 and 70, as shown in detail in
FIGS. 3 and 4, respectively.
[0042] With reference now to FIG. 10, a frontal plan view of the
front shroud 134 of the centrifugal pump 132 of FIG. 9 is shown,
that will be used to describe the front shroud 134 in greater
detail. The strainer 133 includes a plurality of apertures 170 that
may project through the housing 134 in an axial direction, and may
also project through the front shroud 134 in a radial direction.
Although a plurality of apertures 170 are shown, it is understood
that other configurations are possible, and are also within the
scope of the various embodiments. For example, a screen having a
predetermined mesh size may also provide the strainer 133.
[0043] FIG. 11 is a cross sectional view of the front shroud 134 of
FIG. 10, along the cross section 11-11 of FIG. 10. The plurality of
apertures 170 permit fluid communication between a liquid 16 (see
FIG. 1) and an inlet 172. The front shroud 134 may further include
a conical inner portion 174 that adjoins the inlet 172. In the
various embodiments, the conical inner portion 174 may include a
taper angle .alpha. that may range between approximately about 30
degrees and approximately about 90 degrees. In another of the
various embodiments, the taper angle .alpha. may range between
approximately about 45 degrees and approximately about 60 degrees,
although other values for the taper angle .alpha. may be used. The
front shroud 134 may also include a circumferential land 176 that
receives the outer housing 150 (as shown in FIG. 9), and a
circumferential wall 178 that at least partially receives the back
shroud 136 on an inner peripheral portion.
[0044] Referring now to FIG. 12, and with continuing reference to
FIGS. 10 and 11, a rear plan view of the front shroud 134 is shown.
As discussed briefly in connection with FIG. 9, an orifice 142
projects through the circumferential wall 178 and into the conical
inner portion 174 of the front shroud 134 at a location 180. With
reference now also to FIG. 13, an expanded, partial cross sectional
view of the front shroud of FIG. 10 is shown, that will be used to
describe the orifice 142 at the location 180 in greater detail. The
orifice 142 approximately tangentially extends through the wall
178, and may include a constant diameter portion 182 and a tapered
portion 184. The tapered portion 184 is generally conical in shape,
having an included angle .beta.. In the various embodiments, the
included angle .beta. may range between approximately five degrees,
and approximately 50 degrees. In others of the various embodiments,
the included angle .beta. may range between approximately 15
degrees, and approximately 25 degrees, although other angular
ranges may also be used. The constant diameter portion 182 may have
any suitable diameter d, but in accordance with the various
embodiments, the diameter d may range between approximately about
0.030 inches, and approximately about 0.120 inches.
[0045] FIG. 14 is a frontal plan view of the impeller 138 of FIG.
9, which will be used to describe various details of the impeller
138 in greater detail. The impeller 138 may include a disk 190 that
supports a plurality of vanes 192 that extend outwardly from the
disk 190. Although the impeller 138 shown in FIG. 14 includes six
vanes 192, it is understood that the disk 190 may support more than
six vanes 192, or even less than six vanes 192. Further, although
the vanes 192 shown in FIG. 14 are generally straight, it is
understood that the vanes 192 may include other shapes. For
example, the vanes 192 may be backwardly curved, or even forwardly
curved. The disk 190 may include a plurality of apertures 194 that
project through the disk 190. The impeller 138 may also include an
impeller hub 196 that is coupled to the disk 190 and suitably
dimensioned to receive a shaft coupled to the motor 94 (as shown in
FIG. 9). In the various embodiments, the hub 196 may be suitably
dimensioned to fixably retain the impeller 138 on the shaft of the
motor 94 by an interference fit. In other of the various
embodiments, the impeller 138 may be coupled to a shaft of the
motor 94 using mechanical fasteners, such as set screws, or other
similar elements.
[0046] FIG. 15 is a cross sectional view of the impeller 138 of
FIG. 14, along the cross section 15-15 of FIG. 14. The impeller hub
196 may be positioned on a shaft of the motor 94 so that a
predetermined clearance distance l may be maintained between the
vanes 192 and the front shroud 134. In the various embodiments, the
clearance distance l may range between approximately about 0.005
inches and approximately about 0.040 inches. In other of the
various embodiments, the clearance distance l may range between
approximately about 0.008 inches and approximately about 0.020
inches.
[0047] FIG. 16 is a frontal plan view of the back shroud 136, which
will be used to describe the back shroud 136 in greater detail. The
back shroud 136 includes an inner recess 200 that is suitably
dimensioned to accommodate the impeller hub 196 (as shown in FIG.
15). A shaft hole 202 extends through the back shroud 136 that
permits the shaft portion of the motor 94 (as shown in FIG. 94) to
engagably receive the impeller hub 196. An outer recess 204 extends
into the back shroud 136 that is suitably dimensioned to receive a
corresponding portion of the front shroud 134. Mutually
spaced-apart protrusions 206 may extend outwardly from a peripheral
edge of the back shroud 136 that receive and support the outer
housing 150 as it engages the back shroud 136 to provide flow
passages 208 that permit the orifice 142 (as shown in FIG. 9, and
in greater detail in FIG. 13) to fluidly communicate with the
annular fluid discharge space 152.
[0048] FIG. 17 is a cross sectional view of the back shroud 136 of
FIG. 16, along the cross section 17-17 of FIG. 17. The back shroud
136 may further include a rear recess 210 that extends inwardly
into the back shroud 136, and that is suitably dimensioned to
receive the shaft seal 135 (as shown in FIG. 9) that restricts
liquid movement into the volume 148 (as also shown in FIG. 9). The
back shroud 136 may also include an outwardly extending land 205
that may be received by the front shroud 134 so that the land 205
is adjacent to the wall 178 (as shown in FIG. 11).
[0049] FIG. 18 is a flowchart that will be used to describe a
method 230 of removing a liquid from a well, according to the
various embodiments. With reference also again to FIGS. 1 and 2,
the method 230 includes positioning a subsurface unit 12 in a bore
hole 14, as shown at block 232. At block 234, the subsurface unit
12 is coupled to a power supply 28 and a power converter 30. At
block 236, the motor 20 within the subsurface unit 12 is started
using a selected motor speed distribution 120 (as shown in FIG. 8).
For example, in one of the various embodiments, the motor speed
distribution 120 is a linear distribution, wherein the motor 20 is
accelerated to 100 percent of a desired full speed setting within
approximately four seconds. At block 238, a desired steady state
speed for the motor 20 is set by controlling a control input 32 to
the power converter 30. At block 240, a variation in the
steady-state speed is detected by the subsurface controller 22 by
sensing a back EMF from the motor 20. Based upon the sensed back
EMF, the subsurface controller 22 corrects at least one of a
current and a voltage delivered to the motor 20 to return to the
desired steady state speed.
[0050] FIG. 19 is a flowchart that will be used to describe another
method 250 of removing a liquid from a well, according to the
various embodiments. With reference still also to FIGS. 1 and 2,
the method 250 includes positioning a subsurface unit 12 in a bore
hole 14, as shown at block 252. At block 254, the subsurface unit
12 is coupled to a power supply 28, feedback system 42 and a flow
meter 44. At block 256, a desired flow rate to be delivered by the
subsurface unit 12 is selected. The flow rate may be selected, for
example, by identifying a rate at which liquid must be removed in
order to properly sample the bore hole 14, or by identifying a rate
that will maintain a dewatered state in the bore hole 14. At block
258, a speed for the motor 20 is set that will deliver the desired
flow rate. The speed may be set by controlling a control input 32
to the feedback system 42. As discussed previously, the motor 20
within the subsurface unit 12 may be started using a selected motor
speed distribution 120 (as shown in FIG. 8). At block 260, the flow
rate delivered by the subsurface unit 12 may be measured by the
flow meter 44. At block 270, the measured flow rate is compared to
the set flow rate (from block 258). If the measured flow rate
differs from the desired flow rate, the feedback system 42
appropriately corrects at least one of a voltage and a current
delivered to the motor 20 to attain the desired flow rate, as shown
in block 270. If the measured flow rate does not differ from the
desired flow rate, then the method 250 returns to block 260.
[0051] While the various embodiments of the invention have been
illustrated and described, as noted above, many changes can be made
without departing from the scope of this disclosure. Thus, although
specific embodiments have been illustrated and described herein, it
should be appreciated that any arrangement calculated to achieve
the same purpose may be substituted for the specific embodiments
shown. This disclosure is intended to cover any and all adaptations
or variations of various embodiments. Combinations of the above
embodiments, and other embodiments not specifically described
herein, will be apparent to those of skill in the art upon
reviewing the above description.
[0052] Further, the accompanying drawings that form a part hereof
show by way of illustration and not of limitation, specific
embodiments in which the subject matter may be practiced. The
embodiments illustrated are described in sufficient detail to
enable those skilled in the art to practice the teachings disclosed
herein. Other embodiments may be utilized and derived therefrom,
such that structural and logical substitutions and changes may be
made without departing from the scope of this disclosure. This
Detailed Description, therefore, is not to be taken in a limiting
sense, and the scope of various embodiments is defined only by the
appended claims, along with the full range of equivalents to which
such claims are entitled.
[0053] The Abstract of the Disclosure is provided to comply with 37
C.F.R. .sctn.1.72(b), requiring an abstract that will allow the
reader to quickly ascertain the nature of the technical disclosure.
It is submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. In addition,
in the foregoing Detailed Description, it can be seen that various
features may be grouped together in a single embodiment for the
purpose of streamlining the disclosure. This method of disclosure
is not to be interpreted as reflecting an intention that the
claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter lies in less than all features of a single
disclosed embodiment. Thus the following claims are hereby
incorporated into the Detailed Description, with each claim
standing on its own as a separate embodiment.
* * * * *