U.S. patent application number 11/601632 was filed with the patent office on 2007-05-10 for rotary pressure exchanger.
This patent application is currently assigned to KSB Aktiengesellschaft. Invention is credited to Stephan Bross, Wolfgang Kochanowski, Christof Schuler.
Application Number | 20070104588 11/601632 |
Document ID | / |
Family ID | 38003913 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070104588 |
Kind Code |
A1 |
Bross; Stephan ; et
al. |
May 10, 2007 |
Rotary pressure exchanger
Abstract
A pressure exchanger for transferring pressure energy from a
liquid flow of one liquid system to a liquid flow of another system
including a housing provided with inlet and outlet lines for liquid
flows having differing pressure states, and a cylindrical rotor
disposed in the housing for rotation about its longitudinal axis.
The rotor has a plurality of passageways located on an annular
plane surrounding the longitudinal axis of the rotor and having an
opening at each axial end face of the rotor. Inlet and outlet ports
for the inlet and outlet lines are arranged in the housing at the
ends opposite the end faces of the rotor, and sealing zones are
arranged between the inlet and outlet ports. Radially extending
sealing webs are disposed on the end faces of the rotor between the
passageway openings. The rotor passageways are adapted to be
connected to the housing inlet and outlet ports so as to
alternately conduct higher pressure liquid and lower pressure
liquid from the respective liquid systems as the rotor rotates. A
pressure surge-reducing afterflow zone is arranged at the
transition between an inlet port and a sealing zone at the end of
the housing, and/or at the transition between the end face openings
of the rotor passageways and the sealing webs arranged on the rotor
ends.
Inventors: |
Bross; Stephan; (Erpolzheim,
DE) ; Kochanowski; Wolfgang; (Windesheim, DE)
; Schuler; Christof; (Frankenthal, DE) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
KSB Aktiengesellschaft
Frankenthal
DE
|
Family ID: |
38003913 |
Appl. No.: |
11/601632 |
Filed: |
November 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP05/04606 |
Apr 29, 2005 |
|
|
|
11601632 |
Nov 20, 2006 |
|
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Current U.S.
Class: |
417/64 |
Current CPC
Class: |
F04F 13/00 20130101 |
Class at
Publication: |
417/064 |
International
Class: |
F04F 11/00 20060101
F04F011/00 |
Claims
1. A pressure exchanger for transferring pressure energy from a
liquid stream of one liquid system to a liquid stream of another
liquid system, comprising a housing with inlet and outlet lines for
liquid streams having different pressure states and a cylindrical
rotor disposed inside the housing so as to be rotatable about its
longitudinal axis; said rotor having a plurality of passageways
disposed in an annular plane surrounding the longitudinal axis of
the rotor and an opening at each axial end face of the rotor;
wherein inlet and outlet ports for the inlet and outlet lines of
the respective liquid streams are disposed in the housing at the
ends of the housing opposite the rotor end faces; sealing zones are
disposed between the inlet and outlet ports of the housing;
radially extending sealing webs are arranged between the openings
of the rotor passageways, and the passageways of the rotor are
adapted for communication with the inlet and outlet ports of the
housing such that they alternately carry liquid under high pressure
and liquid under low pressure from the respective liquid systems
during rotation of the rotor, and a pressure-surge-reducing
afterflow zone is disposed at the transition between an inlet port
of the housing and the sealing zone of the housing at the end of
the housing or at the transition between the end-face openings of
the passageways in the rotor and the sealing webs of the rotor.
2. A pressure exchanger according to claim 1, wherein during
blocking of a passageway opening by a sealing zone and upon
commencement of overlap between the sealing zone and the following
sealing web, the afterflow zone blocks a volumetric flow flowing
into the passageway to be blocked in a time-delayed manner.
3. A pressure exchanger according to claim 1, wherein an afterflow
zone disposed on the housing at the transition between the inlet
port and the sealing zone has a cross section that decreases toward
the sealing zone in the direction of rotation of the rotor.
4. A pressure exchanger according to claim 3, wherein, as viewed in
the direction of rotation of the rotor, an afterflow zone is
arranged adjacent that part of an inlet port which is blocked by
the respective edge of the opening of a rotor passageway at the
latest possible moment of an introduction of a liquid column into
the rotor.
5. A pressure exchanger according to claim 1, wherein an afterflow
zone disposed on the rotor at the transition between adjacent
openings of the passageways and the sealing web has an increasing
cross section in the direction of rotation of the rotor.
6. A pressure exchanger according to claim 5, wherein, as viewed in
the direction of rotation of the rotor, an afterflow zone is
arranged at that part of a sealing web which blocks a liquid column
from the respective edge of the opening of an inlet port at the
latest possible moment of an inflow of liquid into the rotor.
7. A pressure exchanger according to claim 1, wherein the afterflow
zone on the housing side has a volume characteristic that decreases
toward the sealing zone.
8. A pressure exchanger according to claim 1, wherein rotating
afterflow zones have a volume characteristic that increases from
the end face of the rotor toward the passageway.
9. A pressure exchanger according to claim 1, wherein the
measurable width of a sealing zone between an end of the afterflow
zone and a beginning of an outlet port corresponds to at least the
width of an end-face opening of a passageway and the width of a
sealing web.
10. A pressure exchanger according to claim 1, wherein, in the
transition between the inlet and the outlet ports of the housing
and the openings of the passageways formed in the rotor, a
gap-shaped zone is arranged following an outlet edge of the inlet
or outlet port as viewed in the direction of rotation of the rotor,
which zone produces a low-surge blockage between the passageway
opening of the rotor and the respective inlet port or outlet port
of the housing.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of international patent
application no. PCT/EP2005/004606, filed Apr. 29, 2005, designating
the United States of America, and published in German on Dec. 8,
2005 as WO 2005/116456, the entire disclosure of which is
incorporated herein by reference. Priority is claimed based on
Federal Republic of Germany patent application no. DE 10 2004 025
289.0, filed May 19, 2004.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a rotary pressure exchanger
for transferring pressure energy from a liquid flow of one liquid
system to a liquid flow of another system.
[0003] U.S. Pat. No. 3,431,747 discloses the general principle of a
rotary pressure exchanger, the rotor of which is provided with
passageways in the form of cylindrical bores and having a ball
disposed in each passageway. These balls, which act as sealing
members, cause energy losses and are mechanically complex to
manufacture. In addition, the abrupt impact of the balls on their
spherical seats has the disadvantage that it causes damage due to
cavitation. Published German patent application no. DE 37 81 148,
which discloses a pressure exchanger without ball valve function in
the passageways of the rotor, attempts to avoid this.
[0004] U.S. Pat. No. 5,988,993 (=DE 695 12 089 T2) relates to the
hydrostatic bearing principle of the rotating rotor. This solution
avoids the arrangement of a shaft carrying the rotor and the
corresponding bearing within the housing, but the shaftless
configuration of the rotor is quite complex and expensive to
manufacture. The production costs for the precision manufacture of
a ceramic rotor and the associated ceramic bearing shell are
considerable.
[0005] U.S. Pat. No. 6,540,487 attempts to solve the problem of
noise in pressure exchangers of this type caused by the alternating
opening and closing of the passageways and the concurrent
cavitation. Two sealing areas are provided on the housing end faces
opposite the end faces of a rotor and between an inlet and outlet
port on the housing side. During the respective pressure exchange
processes taking place in the passageways of the rotor, these
sealing zones ensure an external blocking of the passageways. They
also prevent a short circuit flow between the inlet and the outlet
port of the housing. As the openings of the passageways travel
across the sealing zones, the alternating opening and closing of
the passageways causes a considerable amount of noise, and
destructive cavitation phenomena occur. The attempt to avoid the
latter through connecting channels that are formed in the sealing
zones to equalize the pressure between two zones of different
pressure levels, however, reduces the efficiency of a pressure
exchanger of this type and has limited effectiveness.
SUMMARY OF THE INVENTION
[0006] It is an object of the invention to provide an improved
pressure exchanger comprising a rotor disposed within a housing and
having a plurality of passageways therethrough.
[0007] Another object of the invention is to provide a rotary
pressure exchanger which operates with greatly reduced force
loading of the rotor.
[0008] A further object of the invention is to provide a rotary
pressure exchanger with improved cavitation characteristics.
[0009] An additional object of the invention is to provide a rotary
pressure exchanger which operates with a reduced noise level.
[0010] These and other objects are achieved in accordance with the
present invention by providing a pressure-surge-reducing secondary
flow zone or afterflow zone at the transition between a
housing-side inlet port and a housing-side sealing zone and/or at
the transition between the end face openings of the passageways
disposed in the rotor and the sealing webs of the rotor arranged
therebetween.
[0011] The sudden loading of a rotor occurs primarily when a column
of liquid flowing into a passage is abruptly cut off. An abrupt
cutoff of a column of liquid flowing into a passage results in
substantial pressure surges. This causes overloading of the rotor
material, usually a ceramic, even to the point of fractures in the
rotor wall. It also causes cavitation phenomena in the flowing
liquid column with the known detrimental effects. This solution is
independent of the driving method used for such a rotor. It works
both in rotors where the rotary movement is produced by a pulse of
the inflowing liquid and in rotors rotated by an external drive via
a shaft.
[0012] One embodiment of the invention provides that while a
passage opening is blocked by the sealing zone or starts to be
covered by the sealing zone and the following sealing web, the
afterflow zone blocks the volumetric flow into the passageway in a
time delayed manner. This prevents abrupt blocking of the
volumetric flow and the resulting disadvantages.
[0013] A closing process of a passageway is commenced when a first
or preceding sealing web of a passageway as seen in moving
direction reaches the edge of a sealing zone. From this point in
time onward the cross section of an opening is progressively
reduced by the sealing zone, which acts as a cover. With continued
rotational movement of the rotor, a second or following sealing web
of this opening approaches the edge of the sealing zone. An end
face opening of a rotor passageway is generally enclosed between
respective preceding and following sealing webs, which as a rule
extend radially. If the following sealing web reaches the edge of
the sealing zone, the flowing liquid column is blocked abruptly in
view of the peripheral speed of the rotor, causing the detrimental
effects. This is prevented by the arrangement of an afterflow zone
in the area of the intersection of the following sealing web and
the start or the edge of the sealing zone. The afterflow zone
causes a gradual reduction of the flowing liquid column over
time.
[0014] According to other embodiments, an afterflow zone disposed
on the housing at the transition between the inlet port and the
sealing zone as viewed in the direction of rotation of the rotor
has a cross section which decreases toward the sealing zone. On the
other hand, an afterflow zone disposed on the rotor at the
transition between adjacent openings of passageways and a sealing
web has an increasing cross section in the direction of rotation of
the rotor. In this solution, afterflow zones disposed at the
sealing webs of the rotor again block the volumetric flows flowing
into the passageways in a time delayed manner. This prevents an
abrupt blocking of the volumetric flow in the form of a flowing
fluid column and the resulting drawbacks.
[0015] Depending on the structural dimensions of a pressure
exchanger, the width of a sealing zone at a housing end face, the
width of the sealing webs at the rotor end face between adjacent
openings of the passageways formed in the rotor, and the
cross-sectional shape of the passageway, the afterflow zone can be
disposed so as to be stationary in the housing, rotating in the
rotor and/or on both components. In combinations of such rotating
afterflow zones, a stationary afterflow zone on the housing may be
used. Depending on the number of inlet ports, a corresponding
number of afterflow zones is also arranged in or on the
housing.
[0016] An advantageous aspect of the invention is the configuration
according to which, as seen in the direction of rotation of the
rotor, an afterflow zone is disposed at that location of the
pressure exchanger which is blocked by the respective opening edge
of a passageway at the latest possible moment of an inflow or
filling process of a liquid column into the rotor.
[0017] The advantage of creating the afterflow zone is the
resulting gradual slowing down of the liquid column flowing into a
passageway of the rotor. This is a very simple way of preventing
overloading of the material of the passageways in the rotor caused
by pressure surges and pressure pulses. Since rotors of this type
are predominantly ceramic components, their structural durability
is substantially improved as a result.
[0018] In accordance with yet another embodiment, the measurable
width of a sealing zone between an end of the afterflow zone and a
beginning of an outlet port corresponds to at least the width of an
end face opening of a passageway and the width of a sealing web.
This solution ensures a reliable seal of a passageway at the
sealing zone in any event by at least one half of the sealing web
width to prevent a type of continuous short circuit line between
the inlet port and the outlet port.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The invention will be described in further detail
hereinafter with reference to illustrative preferred embodiments
shown in the accompanying drawing figures, in which:
[0020] FIG. 1 shows a three-dimensional view of a transition area
between an inlet port and the passageways of a rotor;
[0021] FIGS. 2 and 3 are diagrams of the pressure pattern during a
filling process of a passageway;
[0022] FIGS. 4a to 4c show different cross-sectional shapes of the
afterflow zone in the stator, and
[0023] FIGS. 5a to 5c show different embodiments of the sealing
webs.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0024] FIG. 1 is a perspective view of the end face of a rotor of a
pressure exchanger with passageways arranged therein and opposite
inlet and outlet ports on the housing side. Those surfaces which
are uniformly distributed on one end face of the rotor and around
its axis of rotation in an annular plane enclosing the axis of
rotation between the openings of passageways are referred to as
sealing webs because of their shape. However, they are actually
only a part of the entire sealing surface on the end face of the
rotor, which adjoins an opposite housing surface and forms a
minimal sealing gap.
[0025] The volume of the gap defined by the dotted lines in the
figure does not correspond to the actual volume but was selected in
the shape depicted due to computational considerations.
[0026] The housing surface has an inlet port and an outlet port.
The fluid under pressure flows through the inlet port into the
passageways in the form of a column of liquid. Within the
passageways, the pressure is transferred to the liquid, which then
flows out of the passageways into an outlet port of the housing.
This occurs alternately in the area of the two end faces of the
pressure exchanger.
[0027] A rotor of this type and the opposite housing surfaces are
formed of a ceramic material, which is sensitive to alternating
pressure loading. An afterflow zone, which is depicted here on the
housing side, prevents an abrupt cutoff of a liquid column flowing
into a passageway. According to the invention it was recognized
that an abrupt cutoff of a flowing liquid column causes pressure
peaks or surges and thus peak stresses that are destructive of the
material. The afterflow zone makes it possible, for the completion
of a blocking process of a passageway to be sealed, to gradually
reduce a volumetric flow flowing into a passageway. A
characteristic curve relative to the average flow rate occurring at
the site of the blockage conforms to the zero line over time.
[0028] In the diagram of FIG. 2 along a time axis t, the dotted
line represents a pressure curve p and the solid line a flow
velocity v of a conventional pressure exchanger at the instant when
a passageway in a rotor is blocked. The two lines illustrate how a
fluid column flows into a passageway of a rotor at a constant
velocity v and a constant pressure p. At the instant t.sub.z, the
sealing zone abruptly blocks the opening of the passageway and the
flow velocity v drops almost instantly to zero. This
disadvantageous blocking or closing process generates a pressure
surge that produces a shock front in the blocked passageway of the
rotor. This shock front oscillates in the blocked passageway at a
very high pressure level and thereby causes excessive loading of
the rotor material. In the worst case, this can lead to the
destruction of the rotor.
[0029] FIG. 3 shows a similarly structured diagram illustrating the
effect of an afterflow zone. When the afterflow zone is reached at
instant t.sub.N1, the flow velocity v is gradually reduced over a
time span t.sub.NZ and completed at instant t.sub.N2. Shortly
before instant t.sub.N2 is reached, the solid curve of flow
velocity v reaches a turning point. This has the result that a
fluid column flowing into a passageway is slowed down gently. As a
consequence, when a passageway is fully closed, a pressure
fluctuation still occurs within it but is much smaller than the
aforementioned pressure surge. As a result, the shock front within
a passage way is substantially weakened, as clearly indicated by
the dotted line. Thus, the fatigue loading of a rotor is
significantly reduced, and the operational reliability of the rotor
is increased several fold.
[0030] FIGS. 4a to 4c illustrate different longitudinal sections of
the afterflow zones taken in flow direction. The afterflow zones
NZ, which are stationary here, are distinguished in that they have
a cross-sectional characteristic between the inlet port 1 and the
sealing zone 2 of the housing extending perpendicularly to the
drawing plane which causes a gradual deceleration of a flowing
liquid column. This characteristic can be wedge-shaped, stepped,
rounded, or the like. The important aspect is the resulting gradual
blocking of a passageway that occurs over a time span t.sub.NZ.
[0031] FIGS. 5a to 5c show different longitudinal sections of
afterflow zones NZ taken in flow direction. In this example, the
afterflow zones are disposed on the sealing webs 3 between the
individual passageways 4 of a rotor 5. The arrow indicates the
direction of rotation of the rotor whose end faces are seated
against the housing and its sealing zones 2 so as to form a seal.
These rotatingly disposed afterflow zones NZ are also distinguished
in that they cause a cross-sectional characteristic between the
inlet port 1 and the sealing zone 2 extending perpendicularly to
the drawing plane, such that a gradual deceleration of a flowing
fluid column is obtained. This characteristic can be wedge-shaped,
stepped, rounded, or the like. The important aspect is the
resulting gradual blocking of the passageways to be filled, which
occurs over a time span t.sub.NZ.
[0032] Depending on the flow volumes to be processed and the size
of a pressure exchanger, the afterflow zones can be disposed only
on the housing, only on the rotor, or in combination.
[0033] The foregoing description and examples have been set forth
merely to illustrate the invention and are not intended to be
limiting. Since modifications of the described embodiments
incorporating the spirit and substance of the invention may occur
to persons skilled in the art, the invention should be construed
broadly to include all variations within the scope of the appended
claims and equivalents thereof.
* * * * *