U.S. patent application number 15/389128 was filed with the patent office on 2018-06-28 for submergible cryogenic pump with linear electromagnetic motor drive.
This patent application is currently assigned to Electro-Motive Diesel, Inc.. The applicant listed for this patent is Electro-Motive Diesel, Inc.. Invention is credited to Peter O. POPADIUC.
Application Number | 20180180042 15/389128 |
Document ID | / |
Family ID | 62625123 |
Filed Date | 2018-06-28 |
United States Patent
Application |
20180180042 |
Kind Code |
A1 |
POPADIUC; Peter O. |
June 28, 2018 |
SUBMERGIBLE CRYOGENIC PUMP WITH LINEAR ELECTROMAGNETIC MOTOR
DRIVE
Abstract
A fully submergible dual-action cryogenic pump has a housing
configured to receive a liquid into the interior compartment when
submerged in the liquid. The housing includes an interior
compartment having an inner peripheral surface, a first end, and a
second end. A free piston having a first end, a second end, and an
outer peripheral surface is contained within the interior
compartment. A first compression chamber is formed between the
first end of the free piston and the first end of the interior
compartment. A second compression chamber is formed between the
second end of the free piston and the second end of the interior
compartment. An electromagnetic drive is configured to reciprocate
the free piston. A sealing area is formed by the outer peripheral
surface of the free piston sealing with the inner peripheral
surface of the interior compartment.
Inventors: |
POPADIUC; Peter O.;
(Bensenville, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Electro-Motive Diesel, Inc. |
LaGrange |
IL |
US |
|
|
Assignee: |
Electro-Motive Diesel, Inc.
LaGrange
IL
|
Family ID: |
62625123 |
Appl. No.: |
15/389128 |
Filed: |
December 22, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 15/08 20130101;
F04B 19/003 20130101; F04B 53/18 20130101; F04B 19/22 20130101;
F04B 53/10 20130101; F04B 53/143 20130101; F04B 17/044 20130101;
F04B 41/06 20130101 |
International
Class: |
F04B 53/14 20060101
F04B053/14; F04B 19/00 20060101 F04B019/00; F04B 19/22 20060101
F04B019/22; F04B 17/04 20060101 F04B017/04; F04B 1/14 20060101
F04B001/14; F04B 53/10 20060101 F04B053/10; F04B 41/06 20060101
F04B041/06; F04B 53/18 20060101 F04B053/18 |
Claims
1. A fully submergible dual-action cryogenic pump, comprising: a
housing including an interior compartment, the housing configured
to receive a liquid into the interior compartment when submerged in
the liquid, the interior compartment including an inner peripheral
surface, a first end, and a second end; a free piston contained
within the interior compartment of the housing, the free piston
including an axis, a first end, a second end, and an outer
peripheral surface; a first compression chamber formed between the
first end of the free piston and the first end of the interior
compartment; a second compression chamber formed between the second
end of the free piston and the second end of the interior
compartment; an electromagnetic drive configured to reciprocate the
free piston along the axis; and a sealing area formed by the outer
peripheral surface of the free piston sealing with the inner
peripheral surface of the interior compartment between the first
compression chamber and the second compression chamber.
2. The fully submergible dual-action cryogenic pump of claim 1,
wherein the free piston includes a length from the first end to the
second end, and the sealing area is formed along substantially all
of the length of the free piston.
3. The fully submergible dual-action cryogenic pump of claim 1,
wherein the outer peripheral surface of the free piston is
configured to sealing area with the inner peripheral surface of the
interior compartment without a piston sealing ring.
4. The fully submergible dual-action cryogenic pump of claim 1,
wherein no bushings are disposed between the free piston and the
housing.
5. The fully submergible dual-action cryogenic pump of claim 1,
wherein: the housing includes an outer wall; and the
electromagnetic drive includes a plurality of electric coils
disposed within the outer wall of the housing and encircling the
axis of the free piston.
6. The fully submergible dual-action cryogenic pump of claim 1,
further comprising a one-way intake valve fluidly connected to the
liquid when the housing is submerged in the liquid.
7. The fully submergible dual-action cryogenic pump of claim 6,
further comprising a primer pump configured to pump the liquid into
the first compression chamber through the one-way intake valve when
the housing is submerged in the liquid.
8. The fully submergible dual-action cryogenic pump of claim 1,
wherein the electromagnetic drive is also configured to rotate the
free piston about the axis of the free piston.
9. The fully submergible dual-action cryogenic pump of claim 1,
wherein: the outer peripheral surface of the free piston includes a
radius; the inner peripheral surface of the interior compartment
includes a radius; and the radius of the outer peripheral surface
of the free piston is between 0.01 micrometers and 2 micrometers
less than the radius of inner peripheral surface of the interior
compartment.
10. The fully submergible dual-action cryogenic pump of claim 1,
wherein one or more of the outer peripheral surface of the free
piston and the inner peripheral surface of the interior compartment
includes solid dry lubricants including one or more of molybdenum
disulfide and sintered silicon carbide.
11. The fully submergible dual-action cryogenic pump of claim 1,
wherein one or more of the outer peripheral surface of the free
piston and the inner peripheral surface of the interior compartment
includes solid dry lubricants including one or more of tungsten(IV)
sulfide and graphite.
12. The fully submergible dual-action cryogenic pump of claim 1,
further comprising a gas layer disposed between the outer
peripheral surface of the free piston and the inner peripheral
surface of the interior compartment.
13. A fully submergible dual-action cryogenic pump system,
comprising: a housing including an interior compartment, the
housing configured to receive a liquid into the interior
compartment when submerged in the liquid, the interior compartment
including an inner peripheral surface; a piston including an outer
peripheral surface, an axis, and a length along the axis; an
electromagnetic drive configured to reciprocate the piston when the
piston is contained within the interior compartment; and wherein a
sealing area is formed by the outer peripheral surface of the
piston sealing with the inner peripheral surface of the interior
compartment when the piston is contained within the interior
compartment.
14. The fully submergible dual-action cryogenic pump system of
claim 13, wherein the outer peripheral surface is disposed along a
majority of the length of the piston.
15. The fully submergible dual-action cryogenic pump system of
claim 13, wherein the outer peripheral surface of the piston is
configured to seal with the inner peripheral surface of the
interior compartment without a piston sealing ring.
16. The fully submergible dual-action cryogenic pump system of
claim 13, further comprising a one-way intake valve configured to
allow the liquid to flow into the interior compartment when the
housing is submerged in the liquid.
17. The fully submergible dual-action cryogenic pump system of
claim 16, further comprising a primer pump configured to pump the
liquid into the interior compartment of the housing through the
one-way intake valve when the housing is submerged in the
liquid.
18. The fully submergible dual-action cryogenic pump system of
claim 13, wherein the piston includes a magnetic portion disposed
eccentrically with respect to the axis as measured in a plane
orthogonal to the axis.
19. The fully submergible dual-action cryogenic pump system of
claim 13, wherein one or more of the outer peripheral surface of
the piston and the inner peripheral surface of the interior
compartment includes solid dry lubricants, the solid dry lubricants
including one or more of molybdenum disulfide, sintered silicon
carbide, tungsten(IV) sulfide, and graphite.
20. A method of pumping a cryogenic liquid using a pump submerged
in the cryogenic liquid, comprising: electromagnetically
reciprocating a free piston enclosed within a housing of the
submerged pump along an axis of the free piston; allowing the
cryogenic liquid to alternately flow into a first compression
chamber inside the housing and into a second compression chamber
inside the housing; alternating between discharging the cryogenic
liquid from the first compression chamber and from the second
compression chamber; and electromagnetically rotating the free
piston about the axis of the free piston.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to a pump and, more
particularly, to a submergible cryogenic pump having a linear
electromagnetic motor drive.
BACKGROUND
[0002] Gaseous fuel powered engines are common in many
applications. For example, the engine of a locomotive can be
powered by natural gas (or another gaseous fuel) alone or by a
mixture of natural gas and diesel fuel. Stationary equipment may
also use an engine powered by natural gas. Natural gas may be more
abundant and, therefore, less expensive than diesel fuel. In
addition, natural gas may burn cleaner in some applications,
producing less greenhouse gas.
[0003] Natural gas, when used in a mobile application, may be
stored in a liquid state onboard the associated machine. This may
require the natural gas to be stored at cold temperatures,
typically about -100.degree. C. to -162.degree. C. The liquefied
natural gas is then drawn from the tank by gravity and/or by a
boost pump, and directed to a high-pressure pump. The high-pressure
pump further increases a pressure of the fuel and directs the fuel
to the machine's engine. In some applications, the liquid fuel may
be gasified prior to injection into the engine and/or mixed with
diesel fuel (or another fuel) before combustion.
[0004] One problem associated with cryogenic pumps located external
to the tank of liquid natural gas involves cooling the pump down
before it can be started. To achieve this, external cryogenic pumps
use expensive and complicated cool-down circuits and procedures.
Additionally, leakage can cause problems for external pumps.
External pumps require complicated and expensive seals and bearings
to prevent or reduce leakage. External pumps additionally require
expensive and complicated systems for the cold end of the pump
handling the liquid fuel. For example, cold-end systems include
ventilation, purging, and temperature monitoring.
[0005] To reduce cost and complexity, some cryogenic pumps are
installed inside the tank and submerged in the liquid natural gas.
Submerging an electric motor in high pressure liquid natural gas,
however, creates other problems. For example, the pump and motor
generate heat, boiling the immediately surrounding liquid natural
gas. Additionally, the rotating components of electric motors and
rotating pumps present additional problems. For example, rotating
bearings are prone to wear, and because they are submerged in high
pressure liquid at cryogenic temperatures, they are difficult to
access for service or replacement. Rotating pumps also consume
large amounts of energy and have complex and expensive
components.
[0006] To address these issues, some pumping systems have used
linear electromagnetic drives to reciprocate a piston partially
disposed in liquid. An exemplary pump is disclosed in U.S. Pat. No.
6,506,030 which issued to Kottke on Jan. 14, 2003 ("the '030
patent"). The pump includes a piston assembly inside a cylinder.
Bushings support the piston and a linear electromagnetic drive
system forces the piston to reciprocate within the cylinder. At the
cold end of the pump, the piston reciprocates in the dispensing
chamber to pump liquid during the down stroke. At the warm end of
the pump, the piston reciprocates in a reservoir chamber which
stores energy during the upstroke to be used in the next down
stroke. Sealing members fluidly separate the dispensing chamber
from the reservoir chamber. Bushings support and guide the piston.
Friction between the piston and each of the sealing members and
bushings generate heat. To minimize undesirable heat transfer into
the liquid fuel, an adaptive plate insulates the cold end of the
pump submerged in the fluid from the warm end which is not
submerged. Additionally, the cold end is insulated by a thermal
jacket.
[0007] While the pump of the '030 patent may help address some of
the difficulties associated with using a linear electromagnetic
drive to reciprocate a pump piston in a high pressure cryogenic
tank, it presents additional problems. For example, the bushings
and sealing member add undesirable complexity and cost because they
are prone to wear and require frequent and expensive maintenance.
Additionally, they generate unwanted heat, making submerging the
pump completely in the liquid undesirable for this design.
[0008] The disclosed pump is directed to overcoming one or more of
the problems set forth above and/or elsewhere in the prior art.
SUMMARY
[0009] In one aspect, the present disclosure is directed to a fully
submergible dual-action cryogenic pump. The cryogenic pump includes
a housing having an interior compartment, and the interior
compartment has an inner peripheral surface, a first end, and a
second end. The housing is configured to receive a liquid into the
interior compartment when submerged in the liquid. A free piston is
contained within the interior compartment of the housing, and the
free piston includes an axis, a first end, a second end, and an
outer peripheral surface. A first compression chamber is formed
between the first end of the free piston and the first end of the
interior compartment. A second compression chamber is formed
between the second end of the free piston and the second end of the
interior compartment. An electromagnetic drive is configured to
reciprocate the free piston along the axis. A sealing area is
formed by the outer peripheral surface of the free piston sealing
with the inner peripheral surface of the interior compartment
between the first compression chamber and the second compression
chamber.
[0010] In another aspect, the present disclosure is directed to a
fully submergible dual-action cryogenic pump system. The pump
system includes a housing having an interior compartment. The
interior compartment has an inner peripheral surface. The housing
is configured to receive a liquid into the interior compartment
when submerged in the liquid. A piston includes an outer peripheral
surface, an axis, and a length along the axis. An electromagnetic
drive is configured to reciprocate the piston when the piston is
contained within the interior compartment. A sealing area is formed
by the outer peripheral surface of the piston sealing with the
inner peripheral surface of the interior compartment when the
piston is contained within the interior compartment.
[0011] In another aspect, the present disclosure is directed to a
method of pumping a cryogenic liquid using a pump submerged in the
cryogenic liquid. The method includes electromagnetically
reciprocating a free piston enclosed within a housing of the
submerged pump along an axis of the free piston. The method also
includes allowing the cryogenic liquid to alternately flow into a
first compression chamber inside the housing and into a second
compression chamber inside the housing. The method also includes
alternating between discharging the cryogenic liquid from the first
compression chamber and from the second compression chamber. The
method also includes electromagnetically rotating the free piston
about the axis of the free piston.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional and diagrammatic illustration of
one embodiment of the cryogenic pump installed in a locomotive
application;
[0013] FIG. 2 is an enlarged, cross-sectional, and diagrammatic
illustration of one embodiment of the cryogenic pump; and
[0014] FIG. 3 is a cross-sectional and diagrammatic illustration
along section A-A of FIG. 2.
DETAILED DESCRIPTION
[0015] FIG. 1 illustrates one embodiment of the cryogenic pump 10.
In this embodiment, the cryogenic pump 10 is installed in a tank 8
of liquid 6 such as a cryogenic fuel. The cryogenic fuel may be
liquid natural gas, but, alternatively, the cryogenic pump 10 may
be used to pump other liquid cryogenic fuel, such as helium,
hydrogen, nitrogen, or oxygen, etc. The cryogenic pump 10 is fully
submerged within the liquid 6 in the fuel tank 8. In the embodiment
illustrated in FIG. 1, the fuel tank 8 is drawn behind a locomotive
14 and provides fuel to the engine 11 of the locomotive 14. A power
source 13 is electrically connected to the cryogenic pump 10. The
cryogenic pump 10 is fluidly connected to a vaporizer 15, where the
liquid 6 is converted into a gas. The vaporizer 15 is connected
through fuel line 12 to the engine 11 of the locomotive 14, where
the engine 11 burns the gaseous fuel. Alternatively, in other
embodiments, however, the cryogenic pump 10 may be used in
stationary equipment (not shown). The cryogenic pump 10 may be used
in any suitable application for pumping liquid cryogenic fuel.
[0016] In one embodiment, illustrated in FIG. 2, the cryogenic pump
10 is fully submerged within the liquid 6. The cryogenic pump 10
includes a housing 16, and the housing 16 includes an interior
compartment 18 having an inner peripheral surface 20 (best
illustrated in FIG. 3). The interior compartment 18 also has a
first end 22 and a second end 24. The cryogenic pump 10 also
includes a free piston 26 contained within the interior compartment
18 of the housing 16. The free piston 26 has no linkages or rods
attached to it. The free piston 26 has an axis 28, a first end 30,
a second end 32, and an outer peripheral surface 34 (best
illustrated in FIG. 3). A first compression chamber 36 is formed
between the first end 30 of the free piston 26 and the first end 22
of the interior compartment 18. A second compression chamber 38 is
formed between the second end 32 of the free piston 26 and the
second end 24 of the interior compartment 18.
[0017] An electromagnetic drive 40 is configured to reciprocate the
free piston 26 along its axis 28 when the free piston 26 is
contained inside the housing 16. The free piston 26 includes a
magnetic portion 50 responsive to electromagnetic fields. The
electromagnetic drive 40 includes a plurality of electric coils 42
encircling the axis 28 of the free piston 26. The electric coils 42
may be enclosed within a separate structure as shown in FIG. 1.
Alternatively, the coils 42 may be disposed within an outer wall 44
of the housing 16.
[0018] In the embodiment illustrated in FIG. 2, the ends 30, 32 of
the free piston 26 do not contact the respective ends 22, 24 of the
interior compartment 18 at each end of the stroke. Rather, at each
end of the stroke, an over-stroke length 76 is defined as the
distance between the ends 30, 32 of the free piston 26 and the
respective ends 22, 24 of the interior compartment 18. FIG. 2
illustrates the free piston 26 at one end of its stroke, after
having fully compressed the first compression chamber 36. In this
position, the over-stroke length 76 is shown as the distance
between the first end 22 of the interior compartment 18 and first
end 30 of the free piston 26. Similarly, at the other end of the
stroke (position not shown), the over-stroke length 76 is the
distance between the second end 24 of the interior compartment 18
and the second end 32 of the free piston 26. Thus, in this
embodiment the over-stroke length 76 is the same at both ends of
the stroke.
[0019] In another embodiment, however, the over-stroke length 76 at
the first end 22 of the interior compartment 18 may be different
from a second over-stroke length (not shown) at the second end 24
of the interior compartment 18. And alternatively, in another
embodiment, the ends 30, 32 of the free piston 26 may contact the
ends 22, 24 of the interior compartment 18 at each end of the
stroke of the free piston 26. That is, the over-stroke length 76
may effectively be zero.
[0020] Referring again to the embodiment illustrated in FIGS. 2 and
3, the housing 16 is configured to be submerged in liquid 6. The
housing 16 includes a system of one-way valves 52, 56, 58, 60 to
allow fluid to flow into and out of the compression chambers 36,
38. A first one-way intake valve 52 fluidly connects the first
compression chamber 36 to the liquid 6 surrounding the housing 16.
The system of one-way valves 52 includes a second one-way intake
valve 56 fluidly connected to the second compression chamber 38.
The system of one-way valves 52 includes a first one-way exhaust
valve 58 and a second one-way exhaust valve 60 fluidly connected to
the first and second compression chambers 36, 38, respectively. The
one-way exhaust valves 58, 60 are configured to allow fluid to flow
out of their respective compression chambers 36, 38 during
compression.
[0021] The one-way valves 52, 56, 58, 60 may be any suitable type
of one-way valve known in the art. Although the one-way valves 52,
56, 58, 60 are shown as separate valves disposed outside of the
housing 16, alternatively, they may be integrally formed with the
housing 16. And although the intake valves 52, 56 are illustrated
near the ends 22, 24 of the interior compartment 18 of the housing
16, alternatively, the intake valves 52, 56 may be disposed at any
suitable location. Instead of separately formed valves,
alternatively, the intake valves 52, 56 may simply be formed as the
intake fluid line 55 directly connected to the interior compartment
18 of the housing 16 at a location (not shown) that is
intermittently sealed by the free piston 26 as the free piston 26
reciprocates.
[0022] A primer pump 54 fluidly connects the first and second
compression chambers 36, 38 to the liquid 6 surrounding the housing
16. The primer pump 54 is fluidly connected with the first
compression chamber 36 through the first one-way intake valve 52
and an intake line 55. Similarly, the primer pump 54 is fluidly
connected with the second compression chamber 38 through the second
one-way intake valve 56 and the intake line 55. Alternatively, in
another embodiment, the one-way intake valves 52, 56 may be
directly fluidly connected (not shown) to the liquid 6 surrounding
the housing 16 without a primer pump 54 and/or the intake line
55.
[0023] In the embodiment illustrated in FIGS. 2 and 3, the free
piston 26 is configured to create a sealing area 62 along its outer
peripheral surface 34 without using a separate sealing element,
such as a piston sealing ring. Various features may work together
to create a low friction interface along the sealing area 62. For
example, these features may include solid dry lubricants,
precision-manufactured surface smoothness and tolerances, and/or a
gas layer around the free piston 26. Each of these features is
discussed in greater detail below.
[0024] The outer peripheral surface 34 of the free piston 26 is
configured to seal with the inner peripheral surface 20 of the
interior compartment 18 without a piston sealing ring. Other
variations may include the use of sealing elements at other
locations on the cryogenic pump 10.
[0025] To form the sealing area 62, the outer peripheral surface 34
of the free piston 26 and the inner peripheral surface 20 of the
interior compartment 18 are formed to precise tolerances, and the
surfaces 20, 34 have smooth finishes. Preferably, the peripheral
surfaces 20, 34 are machined to have an average roughness
measurement between 0.01 micrometers and 0.1 micrometers. In other
embodiments, the average roughness measurement may be less than
0.01 micrometers. Preferably, the radius 66 of the outer peripheral
surface 34 of the free piston 26 is between 0.01 micrometers and 2
micrometers less than the radius 67 of the inner peripheral surface
20 of the interior compartment 18.
[0026] The sealing area 62 may prevent leakage between the first
compression chamber 36 and the second compression chamber 38 at a
high pressure differential, for example up to around 500 psi or
more. In theory, however, some trace amounts of leakage are
possible. Because the free piston 26 is enclosed within the housing
16, any leakage from one compression chamber flows to the other
compression chamber. For example, any leakage from the first
compression chamber 36 flows to the second compression chamber 38.
Thus, the cryogenic pump 10 may prevent external (to the housing
16) leakage.
[0027] In the embodiment illustrated in FIG. 2, the sealing area 62
is formed along all of the length 64 of the free piston 26,
measured from its first end 30 to its second end 32. Alternatively,
in another embodiment, the continuously smooth portions of the
outer peripheral surface 34 of the free piston 26 may be disposed
on less than the entire length 64 of the free piston 26. In this
embodiment, the sealing area 62 may be formed along less than the
entire length 64 of the free piston 26. For example, the
continuously smooth portions of the outer peripheral surface 34 may
be disposed along a majority of the length 64 of the free piston
26. In addition, the free piston 26 may have various features
interrupting the continuously smooth portions of the outer
peripheral surface 34. The free piston 26 may have one or more
notches or recesses at various spacings and/or intervals along the
outer peripheral surface 34. Additionally or in the alternative,
the free piston 26 may have one or more ends that are not
necessarily flat or that do not necessarily lie in one or more
planes perpendicular to the axis 28 of the free piston 26. For
example, end surfaces of the free piston 26 may be configured with
various profiles resulting in the ends of the free piston 26 having
a semispherical configuration, a frustoconical configuration, a
triangular configuration, or other convex or concave
configurations, and the interior compartment 18 may have
complementary shaped ends (not shown).
[0028] In one embodiment, reciprocation of the free piston 26
within the interior compartment 18 of the housing 16 may cause a
small and controlled amount of friction-generated heat along the
sealing area 62. This heat vaporizes the immediately surrounding
liquid 6, creating a gas layer between the outer peripheral surface
34 of the free piston 26 and the inner peripheral surface 20 of the
interior compartment 18. The gas layer is disposed along the
sealing area 62 and reduces friction thereby facilitating
reciprocation of the free piston 26. In this way, the gas layer may
act like a linear gas bearing along the sealing area 62.
[0029] Alternatively, in another embodiment, solid dry lubricants
are used to reduce friction along the sealing area 62. This may
reduce friction-generated heat and prevent the gas layer from
forming such that the outer peripheral surface 34 of the free
piston 26 directly contacts and slides along the inner peripheral
surface 20 of the interior compartment 18. In this embodiment, one
or more of the outer peripheral surface 34 of the free piston 26
and the inner peripheral surface 20 of the housing 16 may include
solid dry lubricants. The solid dry lubricants may include, for
example, molybdenum disulfide (MoS.sub.2), sintered silicon carbide
(SiC), tungsten(IV) sulfide (WS.sub.2), graphite, or a combination
thereof. The solid dry lubricants may be embedded, fused, or
diffused into the free piston 26 and/or the interior compartment
18. For example, thin film of the solid dry lubricants may be
formed on one or more of the peripheral surfaces 20, 34, using any
suitable technique, for example, conventional sputtering deposition
or ion beam assisted deposition. In this embodiment, the solid dry
lubricants help facilitate low friction reciprocation of the free
piston 26.
[0030] No bushings or separate support structure are necessary
between the free piston 26 and the interior compartment 18 of the
housing 16. Rather, the inner peripheral surface 20 of the interior
compartment 18 supports and guides the free piston 26 along its
axis 28 during reciprocation. As explained above, low friction
between the peripheral surfaces 20, 34 generates minimal heat and
reduces wear.
[0031] In one embodiment, the free piston 26 may be rotated to
reduce wear along the sealing area 62. For example, the
electromagnetic drive 40 may be configured to rotate the free
piston 26 about its axis 28 to reduce wear on the free piston 26
and housing 16 potentially caused by small variations in shape or
surface finish. In the embodiment illustrated in FIG. 2, the free
piston 26 includes a second magnetic portion 68. The
electromagnetic drive 40 may be configured to exert a force on the
second magnetic portion 68 to rotate the free piston 26. The second
magnetic portion 68 may be eccentrically disposed with respect to
the axis 28 as measured in a plane (not shown) orthogonal to the
axis 28.
[0032] Alternatively, the cryogenic pump 10 may use any suitable
configuration to rotate the free piston 26 as known in the art to
electromagnetically rotate a shaft. Although the second magnetic
portion 68 is separate from the magnetic portion 50 in this
embodiment, instead, in other embodiments, magnetic portion 50 and
the second magnetic portion 68 may be formed together as one
continuous magnetic portion. That is, the electromagnetic drive 40
may be configured to both reciprocate and rotate the free piston 26
by acting on the magnetic portion 50.
[0033] In the embodiment illustrated in FIGS. 2 and 3, rotation of
the free piston 26 helps prevent uneven wear. In another
embodiment, rotation of the free piston 26 may also provide an
additional flow of liquid 6 from the housing 16. In this
embodiment, the free piston 26 includes one or more recesses (not
shown) forming rotational pumping chambers (not shown) with the
interior compartment 18 of the housing 16. The housing 16 includes
additional ports and valves (not shown) fluidly connected with the
rotational pumping chambers. The flow from the rotational pumping
chambers provides an additional way to fine tune the total output
of the cryogenic pump 10. For example, the reciprocation rate of
the free piston 26 may be held constant while the rotational rate
is adjusted to fine tune the total output of the cryogenic pump
10.
[0034] The cryogenic pump 10 may be manufactured using any suitable
method. In some embodiments, the housing 16 is manufactured as two
separate parts (not shown). The two parts (not shown) of the
housing 16 are assembled with the free piston 26 disposed in the
interior compartment 18 of the housing 16. The two parts of the
housing 16 may be sealed together using any suitable method. For
example, they may be sealed using fasteners, adhesives, welding,
etc. Alternatively, the housing 16 may be manufactured as a tube
(not shown) with separate end caps (not shown). Once the free
piston 26 is placed within the interior compartment 18 of the
housing 16, the end caps are attached to the tube to seal both ends
of the tube. Any suitable method may be used to attach the end caps
to the tube to enclose the free piston 26 within the housing 16.
For example, the end caps may be sealed to the housing 16 using
fasteners, adhesives, welding etc. Additionally, any other suitable
manufacturing technique for producing a housing 16 with an
internally contained free piston 26 may be used.
[0035] The cryogenic pump 10 may be installed inside a tank 8 of
cryogenic fuel. Installing the cryogenic pump 10 within the tank 8
may include directly mounting the housing 16 to the inside of the
tank 8 to secure it therein. Alternatively, a mounting bracket (not
shown) may be mounted to the tank 8 and the housing 16 may be
mounted to the mounting bracket. The mounting bracket may isolate
vibrations generated from the movement of the locomotive 14 or
other machinery, to reduce wear on the cryogenic pump 10. In some
embodiments, the cryogenic pump 10 may be assembled during
installation. For example, the steps described above for enclosing
the free piston 26 inside the housing 16 may be performed during
installation.
[0036] In the embodiment illustrated in FIG. 2, a single housing 16
has a single interior compartment 18, and a single free piston 26
is disposed therein. Alternatively, a plurality of interior
compartments and free pistons may form the cryogenic pump 10. The
plurality of interior compartments may be formed within one or more
housings (not shown). Each housing may be manufactured as two parts
which are sealed together to create the plurality of interior
compartments with respective free pistons disposed therein.
[0037] In the embodiment illustrated in FIG. 2, the free piston 26
is hollow and has an outer wall 70 defining a cavity 72 inside.
This reduces the weight of the free piston 26. The cavity 72 may be
filled with gas or may be evacuated to create a vacuum.
Alternatively, in another embodiment, however, the free piston 26
may be solid throughout. In the embodiment illustrated in FIG. 2,
the free piston 26, housing 16, and interior compartment 18 are
generally cylindrical in shape. Alternatively, in other
embodiments, free piston 26, housing 16, and interior compartment
18, may have any other suitable shape.
[0038] The magnetic portion 50 of the free piston 26 is disposed
within the outer wall 70 of the free piston 26. Any suitable
material responsive to magnetic fields may be used to form the
magnetic portion 50. For example, the magnetic portion 50 may be a
permanent magnet. The magnetic portion 50 may disposed generally in
the middle of the free piston 26 along the axis 28. Each of the
electromagnetic drive 40 and the magnetic portion 50 has a length
measured along the axis 28. As shown in the embodiment illustrated
in FIG. 2, the lengths of the electromagnetic drive 40 and magnetic
portion 50 may be roughly equal. Alternatively, in another
embodiment, the length of the magnetic portion 50 is approximately
two times the length of the electromagnetic drive 40. This allows
the electromagnetic drive 40 to fully engage the magnetic portion
50 along the entire stroke of the free piston 26. Alternatively,
the magnetic portion 50 may be disposed within the cavity 72 and
attached to the inside of the outer wall 70. The magnetic portion
50 may be disposed along the entire length 64 of the free piston
26. For example, the free piston 26 may be a formed as a cylinder
of metal with a coating forming the outer peripheral surface 34 of
the free piston 26. The coating may be made from ceramic, for
example. The free piston 26 may be formed from any suitable
material, however. For example, the free piston 26 may include a
material that expands and contracts a relatively small amount over
a wide range of temperatures, such as ceramic. That is, the
material may have a low coefficient of thermal expansion.
[0039] The dimensions of the various parts of the cryogenic pump 10
are selected to optimize multiple design considerations. For
example, the volumes of the compression chambers 36, 38 determine
the volume output of the cryogenic pump 10 per reciprocation cycle.
The volumes of the compression chambers 36, 38, in turn, are a
product of the stroke length 74 and the cross sectional area (not
shown) of the free piston 26 in a plane orthogonal to its axis 28.
In one embodiment, the free piston 26 has a diameter between 15 mm
and 25 mm, and the stroke length 74 of the free piston 26 is
between 90 mm and 110 mm.
INDUSTRIAL APPLICABILITY
[0040] The disclosed cryogenic pump 10 finds potential application
in any fluid system where high-pressurization of cryogenic fluids
is required. For example, the disclosed cryogenic pump 10 may be
used in mobile (e.g., locomotive) or stationary (e.g., power
generation) applications having an internal combustion engine that
consumes the fluid pressurized by the disclosed cryogenic pump 10.
Operation of the cryogenic pump 10 will now be explained.
[0041] FIG. 1 illustrates an overview of one embodiment of the
cryogenic pump 10 used in a locomotive application. In this
embodiment, the cryogenic pump 10 provides pressurized cryogenic
fuel in liquid form to the engine 11 of the locomotive 14 for
combustion. The power source 13 provides electricity to the
cryogenic pump 10 and the primer pump 54. The primer pump 54 pumps
the liquid 6 into the cryogenic pump 10, which in turn, pumps the
liquid 6 to the vaporizer 15. The vaporizer 15 then converts the
liquid 6 into a gas. From the vaporizer 15, the gaseous fuel flows
through the fuel line 12 to the engine 11 of the locomotive 14,
where the engine 11 burns the gaseous fuel.
[0042] Detailed operation of the cryogenic pump 10 will now be
explained. In one embodiment illustrated in FIG. 2, the primer pump
54 pumps liquid 6 from the fuel tank 8 into the interior
compartment 18 of the housing 16 of the cryogenic pump 10. The
liquid 6 travels from the primer pump 54 through the intake line 55
and through one-way intake valves 52, 56 into the interior
compartment 18. Thus, the primer pump 54 delivers the liquid 6 into
the interior compartment 18 of the housing 16 at a higher pressure
than the liquid 6 surrounding the housing 16.
[0043] Alternatively, however, in another embodiment, liquid 6
surrounding the housing 16 may flow directly into the interior
compartment 18 without a primer pump 54 (not shown). In this
embodiment, the movement of the free piston 26 draws the liquid 6
directly into the compression chambers 36, 38. Specifically, as the
free piston 26 translates to the left as illustrated in FIG. 2, the
free piston 26 compresses the first compression chamber 36.
Simultaneously, this translation expands the second compression
chamber 28. This pulls the liquid 6 surrounding the housing 16
directly into the second compression chamber 38 (configuration not
shown). Next, the free piston 26 translates to the right as
illustrated in FIG. 2, and compresses the second compression
chamber 38. Simultaneously, this translation expands the first
compression chamber 36. This pulls the liquid 6 surrounding the
housing 16 directly into the first compression chamber 36
(configuration not shown). Thus, in this embodiment, the
reciprocating movement of the free piston 26 causes the liquid 6
surrounding the housing 16 to alternately flow into each of the
compression chambers 26, 28.
[0044] Referring again to the embodiment illustrated in FIG. 2, the
electromagnetic drive 40 reciprocates the free piston 26 inside the
housing 16 to pump the liquid 6. The power source 13 (FIG. 1)
provides an alternating electric current through an electric line 9
(FIG. 1) to the coils 42 (FIG. 2). By alternating the electric
current through the electric coils 42, the electromagnetic drive 40
produces an alternating magnetic field in the interior compartment
18 of the housing 16. This magnetic field acts on the magnetic
portion 50 of the free piston 26, forcing the free piston 26 to
reciprocate. Additionally, the electromagnetic drive 40 may also
electromagnetically rotate the free piston 26 about the axis 28 of
the free piston 26 by acting on the second magnetic portion 68.
[0045] Reciprocation of the free piston 26 will now be explained in
more detail. FIG. 2 illustrates the free piston 26 after fully
compressing the fluid in the first compression chamber 36. In this
position, the first end 30 of the free piston 26 remains the
over-stroke length 76 from the first end 22 of the interior
compartment 18. From this position, the electromagnetic drive 40
forces the free piston 26 towards the second end 24 of the interior
compartment 18. The free piston 26 travels the stroke length 74
towards the second end 24 of the interior compartment 18. This
compresses the fluid in the second compression chamber 38. The free
piston 26 then stops when its second end 32 is the over-stroke
length 76 away from the second end 24 of the interior compartment
18. The electromagnetic drive 40 then forces the free piston 26
towards the first end 22 of the interior compartment 18. The free
piston 26 travels the stroke length 74 towards the first end 22 of
the interior compartment 18. This compresses the fluid in the first
compression chamber 36 and returns the free piston 26 to the
starting position shown in FIG. 2. Thus, alternating current
through the electromagnetic drive 40 forces the free piston 26 to
reciprocate the stroke length 74.
[0046] A system of valves 52, 56, 58, 60 facilitate the flow of
liquid 6 into and out of the interior compartment 18. The intake
valves 52, 56 allow the liquid 6 to alternately flow into the first
compression chamber 36 and the second compression chamber 38 inside
the housing 16. The cryogenic pump 10 alternates between
discharging the liquid 6 from the first compression chamber 36 and
from the second compression chamber 38 through the exhaust valves
58, 60.
[0047] The disclosed cryogenic pump 10 may provide a high-pressure
supply of fuel in a simple, low maintenance, and submergible
configuration. The cryogenic pump 10 creates a sealing area 62
between the outer peripheral surface 34 of the free piston 26 and
the inner peripheral surface 20 of the interior compartment 18 of
the housing 16. This may eliminate the need for piston sealing
rings that are both prone to wear and generate undesirable heat
from friction. Eliminating these sealing members may reduce
maintenance costs, down time, and the amount of heat generated from
friction. Thus, the cryogenic pump 10 may be completely submerged
in a cryogenic fuel without introducing undesirably large amounts
of heat to the liquid fuel. Completely submerging the cryogenic
pump 10 may also eliminate costly and complicated systems
associated with completely and partially external pumps.
[0048] It will be apparent to those skilled in the art that various
modifications and variations can be made to the pump of the present
disclosure. Other embodiments of the pump will be apparent to those
skilled in the art from consideration of the specification and
practice of the pump disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope being indicated by the following claims and their
equivalents.
* * * * *