U.S. patent application number 12/970161 was filed with the patent office on 2012-06-21 for concentric multi-stage centrifugal pump with start stage.
This patent application is currently assigned to EATON CORPORATION. Invention is credited to Martin A. Clements.
Application Number | 20120156066 12/970161 |
Document ID | / |
Family ID | 45370446 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120156066 |
Kind Code |
A1 |
Clements; Martin A. |
June 21, 2012 |
CONCENTRIC MULTI-STAGE CENTRIFUGAL PUMP WITH START STAGE
Abstract
A multi-stage concentric centrifugal pump includes a start
stage. An inner impeller stage is driven by drive shaft while an
electric motor drive is selectively switched on for starting, and
off for normal operation to drive an outer impeller stage. The
electric motor driven outer stage builds required system pressure
and flow at engine starting, and then permits the electric motor to
be switched off and allow the outer stage to act as a free rotating
disk to improve operating efficiency of the pump.
Inventors: |
Clements; Martin A.; (North
Royalton, OH) |
Assignee: |
EATON CORPORATION
|
Family ID: |
45370446 |
Appl. No.: |
12/970161 |
Filed: |
December 16, 2010 |
Current U.S.
Class: |
417/410.1 ;
417/53 |
Current CPC
Class: |
F04D 1/003 20130101 |
Class at
Publication: |
417/410.1 ;
417/53 |
International
Class: |
F04B 35/04 20060101
F04B035/04; F04B 49/06 20060101 F04B049/06 |
Claims
1. A centrifugal pump assembly comprising: a first pump stage; a
second pump stage independently rotatable relative to and disposed
in concentric relation with the first pump stage; and a drive
assembly operatively associated with the first and second pump
stages that rotates the first and second pump stages to a first
rotational speed and then (a) turns off drives the first pump stage
of the first rotational speed or (b) independently drives the first
and second pump stages above the first rotational speed.
2. The centrifugal pump assembly of claim 1 wherein the second pump
stage rotates freely independent of the first rotational speed.
3. The centrifugal pump assembly of claim 2 wherein the first pump
stage is an inner impeller stage and the second pump stage is an
outer impeller stage.
4. The centrifugal pump assembly of claim 2 wherein the drive
assembly includes a main drive shaft connected to and selectively
rotating the first pump stage.
5. The centrifugal pump assembly of claim 4 wherein the drive
assembly includes a separate drive means for rotating the second
pump stage.
6. The centrifugal pump assembly of claim 5 wherein the separate
drive means is an electric motor drive.
7. The centrifugal pump assembly of claim 6 wherein the electric
motor drive is concentrically located about the main drive
shaft.
8. The centrifugal pump assembly of claim 7 wherein the electric
motor drive rotates the second pump stage at a different speed than
the main drive shaft rotates the first pump stage.
9. The centrifugal pump assembly of claim 1 wherein the first pump
stage is an inner impeller stage and the second pump stage is an
outer impeller stage.
10. The centrifugal pump assembly of claim 1 wherein the drive
assembly includes a separate drive motor for rotating the second
pump stage.
11. The centrifugal pump assembly of claim 1 wherein the drive
assembly includes a separate electric motor for rotating the second
pump stage that is concentrically located about a main drive shaft
that rotates the first pump stage.
12. The centrifugal pump assembly of claim 1 wherein the drive
assembly rotates the second pump stage at a different speed than
the first pump stage to obtain desired performance
characteristics.
13. The centrifugal pump assembly of claim 12 wherein the drive
assembly includes a separate electric motor drive for rotating the
second pump stage at a slower speed than a main drive shaft rotates
the first pump stage below the first rotational speed.
14. A method of operating a centrifugal pump assembly comprising:
providing a first pump stage; providing a second pump stage
concentrically mounted around the first pump stage; independently
driving the first and second pump stages; and switching off the
drive for the second pump stage above a preselected rotational
speed.
15. The method of claim 14 further comprising allowing the second
pump stage to rotate freely relative to the first pump stage above
the preselected rotational speed.
16. The method of claim 15 further comprising driving the first and
second pump stages at different speeds.
17. The method of claim 16 wherein the driving step includes using
an electric motor drive for rotating the second pump stage.
18. The method of claim 15 wherein the driving step includes using
an electric motor drive for rotating the second pump stage.
19. The method of claim 14 further comprising driving the first and
second pump stages at different speeds.
20. The method of claim 14 wherein the driving step includes using
an electric motor drive for rotating the second pump stage.
Description
BACKGROUND OF THE DISCLOSURE
[0001] This disclosure relates to a pump, and more particularly to
a high speed centrifugal pump, with the addition of a start stage.
However, selective details may find application in related pump
environments.
[0002] Centrifugal pumps are generally well known in the art.
Generally speaking, an axial inlet provides fluid to a rotating
impeller. A first stage impeller is driven by a rotating drive
shaft so that the first stage impeller imparts energy to the fluid
which exits generally radially from the first stage. Typically,
axially spaced bearings are disposed along an outer surface of the
shaft to support the shaft and impeller within the pump housing.
The impeller is located within a pumping cavity of the housing and
seals are provided on front and rear faces of the impeller so that
the pressure build-up from the rotating impeller is imparted to the
fluid within the pump cavity. A stationary diffuser is provided at
a radial outer location of the impeller and receives the fluid from
the impeller. The diffuser converts high velocity fluid energy into
lower velocity fluid energy thereby increasing the pressure of the
fluid as the fluid is directed to a discharge passage.
[0003] Such centrifugal pumps are used in a wide variety of
applications. One such application is providing high pressure fuel
flow to a jet engine, for example. This environment requires a
minimal pump packaging volume, and also a minimal weight.
Optimizing pump performance and particularly optimizing pump
performance at engine start-up in order to build the desired or
required system pressure and flow is desired. However, once the
start-up pressure and flow is established, it is important to limit
the impact of the starting components on operation of the pump.
[0004] Therefore, a need exists for a compact package of a
high-speed centrifugal pump that also has reduced weight and
satisfies start stage requirements for the system.
SUMMARY OF THE DISCLOSURE
[0005] A centrifugal pump assembly includes a first pump stage, a
second pump stage independently rotatable relative to the first
pump stage, and a drive assembly that rotates the first and second
pump stages to a first speed and then rotates the second pump stage
at a different speed than the first pump stage.
[0006] In one embodiment, the second pump stage becomes freely
rotating at a selectable operating condition.
[0007] The second impeller stage may rotate faster at start-up and
then rotate at approximately one-half of the speed of the first
pump stage speed.
[0008] In one arrangement, the second pump stage rotates at a
slower speed based on a fluidic drive provided by the driven first
stage speed.
[0009] A first pump stage is an inner impeller stage, and the
second pump stage is preferably a concentric, outer impeller
stage.
[0010] The drive assembly includes a main drive shaft connected to
and selectively rotating the first pump stage.
[0011] The drive assembly includes a separate drive member for
rotating the second pump stage independently of the first pump
stage.
[0012] In one arrangement, the separate drive member is an electric
motor drive.
[0013] The electric motor drive many be concentrically located
about the main drive shaft and adapted to rotate the second pump
stage at a different speed than the main drive shaft rotates the
first pump stage.
[0014] Consequently, at start-up, the outer stage may rotate at a
high speed to increase the pressure.
[0015] After start-up, the second, outer stage rotates slower since
the outer impeller stage is only fluidically coupled to the inner
impeller stage.
[0016] A method of operating the centrifugal pump assembly includes
providing first and second pump stages. The method includes
independently driving the first and second pump stages.
[0017] Once start-up speed is attained, a positive drive for the
second pump stage may be turned off and the second pump stage
allowed to freely rotate.
[0018] In another arrangement, the concentric outer stage can be
driven with not only the fluidic drive but also the second, outer
stage drive motor and continue to drive the second pump stage if so
desired.
[0019] The driving step includes using an electric drive motor for
rotating the second pump stage so that the first and second pump
stages may be driven at different speeds.
[0020] A primary benefit is a reduction in disk drag associated
with the high speed centrifugal pump using multiple stages.
[0021] Another benefit is associated with the minimal pump
packaging volume, for example by placing the first and second pump
stages disposed in concentric fashion.
[0022] Still another advantage resides in the reduced weight while
providing for start-up.
[0023] Still other benefits and advantages of the present
disclosure will become apparent upon reading and understanding the
following detailed description.
BRIEF DESCRIPTION OF THE DRAWING
[0024] FIG. 1 is a cross-sectional view of a preferred embodiment
of the present disclosure.
DETAILED DESCRIPTION
[0025] As shown in FIG. 1, a pump assembly, and more particularly a
centrifugal pump assembly 100, includes a housing 102 having an
inlet 104 shown here as an axial inlet that communicates with a
pump cavity or chamber 106. Received in the pump chamber is a
rotary pump 110 and specifically a multi-stage rotary pump provided
by a first or inner impeller stage 112 and a second or outer
impeller stage 114. The first stage is in fluid communication with
the inlet so that an axial passage 116 receives the fluid from the
inlet 104 and through rotation of the inner impeller stage,
provides fluid at a higher pressure to radial outlet 118.
[0026] The inner impeller stage 112 is positively driven by a
portion of the drive assembly 120, and more particularly by drive
shaft 122 that rotates the inner impeller stage at a desired speed.
Preferably the drive shaft 122 is supported and axially spaced
locations by first and second bearings 124, 126 that support the
drive shaft for relative rotation with respect to the housing 102.
In addition, seals 128 are typically provided and extend between
the outer surface of the drive shaft and an inner wall of the
passage in the housing that receives the drive shaft 122. In
addition, a first impeller seal 140 is provided adjacent the inlet
104 and seals between the inner, front surface of the inner
impeller stage 112 and the inlet 104 while a second or rear seal
142 is disposed along a rear surface or rear face of the inner
impeller stage 112 and the housing 102. Thus, as the first impeller
stage 112 is rotated by the drive shaft 122, fluid from the inlet
104 proceeds through passages 116 to the outlets 118.
[0027] Also received within the pump chamber 106 is the second or
outer impeller stage 114. Preferably, the outer impeller stage 114
is concentrically located relative to the inner impeller stage 112.
That is, a radially extending passage 144 receives fluid from the
outlet 118 of the inner impeller stage, and imparts additional
energy from the outer impeller stage 114 before the fluid exits and
communicates with a stationary diffuser 150 that leads to discharge
passage 152. The outer impeller stage 114 includes a recess 154
dimensioned to closely receive the outer radial dimension of the
inner impeller stage 112. An axially extending portion of the outer
impeller stage has a first portion 156 that is received in the pump
chamber in radially spaced location relative to the inlet end of
the inner impeller stage. The first axial portion 156 is supported
by an outer stage bearing 158 that supports the outer impeller
stage for relative rotation with respect to the housing 102. In
addition, seal 160 is interposed between the first axial portion
156 and an inner surface that defines the pump chamber in the
housing. Similarly, a second axial portion 162 extends rearwardly
and is supported by a second outer stage bearing 164 and receives a
seal 166 between the second axial portion and the pump housing
102.
[0028] A second portion of the drive assembly 120 is provided by an
outer stage drive motor 180 which is in this particular instance is
an electric drive motor. This drive motor 180 provides for positive
independent driving movement of the outer impeller stage 114
relative to the inner impeller stage 112. There are situations
where it is desirable to use the drive motor 180 to positively
drive the outer impeller stage 114 at a different speed than the
inner impeller stage. Of course, one skilled in the art will also
appreciate that the inner and outer impeller stages 112, 114 could
be driven at the same speed if so desired. By using an independent
outer stage drive motor 180, the outer stage can be positively
driven or rotated at a fast speed at start-up in order to build a
desired pressure. Once the desired pressure is reached, then one of
two actions can be taken. First, the outer stage drive motor 180
can be turned off so that the outer impeller stage rotates freely
and the drive energy imposed on the outer stage is provided by a
fluid coupling fluidic forces provided by the driven inner impeller
stage 112. Under such an arrangement, the inner impeller stage 112
may be rotating at a first speed N1 while the outer stage may be
rotating at a reduced, second rotational speed N2. Typically, N2 is
approximately one-half the rotational speed of N1. Thus, the
electric motor drive 180 is capable of being switched on for
starting and then turned off for normal operation of the outer
impeller stage 114. During low inner impeller stage drive speed
operation, such as engine starting, the electric drive motor 180
that drives the outer impeller stage 114 builds the required system
pressure and flow. Once sufficient engine speed is attained to
permit the impeller stage to produce the required system pressure,
the electric drive motor 180 may be switched off. Thereafter, the
outer stage 114 is allowed to act as a free rotating disk, and
driven only by the fluidic coupling provided by fluid rotation
caused by the inner impeller stage 112 and thereby improves the
operating efficiency of the pump 100.
[0029] In other instances, it may be desired to control the
rotational speed of the outer stage 114 by using both the fluid
coupling and the outer stage drive motor 180. In such instances,
the outer impeller stage 114 is rotated faster or slower than the
inner impeller stage, however, optimized pump performance can be
controlled through selective, independent drive of the outer
impeller stage.
[0030] By locating the outer impeller stage 114 in concentric
relation with the inner impeller stage 112, the fluid is first
pressurized by the inner impeller stage, exits outlet 118, and is
fed to inlet of the radial passage 144 of the outer impeller stage.
Upon exiting the outer impeller stage, the energized fluid enters
the stationary diffuser and ultimately reaches the discharge or
outlet of the fluid pump.
[0031] The concentric arrangement provides for a compact package of
a high speed centrifugal pump that includes a start stage. In
addition, by independently driving the inner and outer impeller
stages, reduced impeller fluid friction drag due to a free rotating
disk action during normal operation is achieved. Likewise, there is
an increased ability to receive flow at the stationary radial
diffuser and shape the diffuser pressure recovery characteristics
due to lower outer stage rotational speed. As a result, pump
performance can be optimized relative to the ratio of impeller
drive speeds (i.e., N1 vs. N2). Further, pump performance can be
optimized via the ratio of pressure rise from each impeller stage.
All of this is achieved in a pump package volume that is minimized
and a multistage pump that has a reduced weight while still
incorporating a start stage.
[0032] The disclosure has been described with reference to the
preferred embodiments. Modifications and alterations will occur to
others upon reading and understanding this specification. It is
intended to include all such modifications and alterations in so
far as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *