Rotary kinetic fluid motors or pumps – Selectively adjustable vane or working fluid control means – Upstream of runner
Reexamination Certificate
2001-01-31
2003-03-18
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Selectively adjustable vane or working fluid control means
Upstream of runner
C415S151000, C415S191000, C415S208200
Reexamination Certificate
active
06533543
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pump such as a circulating water pump for use in water supply and discharge facilities and power plants, and more particularly to a vortex prevention apparatus for use in a pump pit for preventing an air entrained vortex or a submerged vortex from being produced when water in the pump pit is pumped by a pump.
2. Description of the Related Art
For pumping water from an open channel that is generally used, as shown in
FIGS. 31A and 31B
of the accompanying drawings, it has been customary to install a pump in such a manner that a suction port
14
a
defined in the lower end of a suction bell mouth
14
connected to the lower end of a suction casing (pump casing)
12
is immersed in water in a pump pit
10
. When the pump is operated, water in the pump pit
10
is introduced through the suction port
14
a
into the suction casing
12
. In this case, since water around the suction port
14
a
has a free surface, if the suction port
14
a
is immersed by a small depth S or water in the open channel flows at a large velocity V, then an air entrained vortex (air entraining vortex) A which is connected from the water surface to the suction port
14
a
by a vortex filament L may be generated, or a submerged vortex B which is connected from the bottom of the pump pit
10
to the suction port
14
a
may be generated. The generation of the air entrained vortex A or the submerged vortex B tends to cause vibration and noise which are detrimental to the operation of the pump.
As shown in
FIGS. 32A and 32B
of the accompanying drawings, a water discharge pump is combined with a lateral-suction closed-type channel and has a suction casing
12
having a suction bell mouth
14
placed in a closed-conduit pump pit
10
which has a laterally open inlet port
10
c
. Since water around the suction port
14
a
of the suction bell mouth
14
connected to the lower end of the suction casing
12
has no free surface, generation of an air entrained vortex is suppressed. However, when water in the channel flows at an increased velocity V, an air entrained vortex A which is connected from the free surface in an open channel to the suction port
14
a
by a vortex filament L may be generated, and the construction cost of the closed-type channel is high.
FIGS. 33A and 33B
of the accompanying drawings show still another conventional pump having a suction casing
12
placed in a pump pit
10
. A vortex prevention plate
16
having a semicircular recess
16
a
surrounding the suction casing
12
is horizontally attached to a peripheral wall
10
a
of the pump pit
10
. An L-shaped vortex prevention plate (splitter)
18
is attached to the peripheral wall
10
a
and a bottom wall
10
b
of the pump pit
10
. The L-shaped vortex prevention plate
18
extends along the direction of the water flow from a position laterally of the suction casing
12
to a position below a suction bell mouth
14
connected to the lower end of the suction casing
12
.
FIGS. 34A
,
34
B, and
35
of the accompanying drawings show yet another vortex prevention structure including an annular frame
152
mounted concentrically on the lower end of a suction pipe
150
by support rods
154
. The annular frame
152
has a diameter greater than the diameter of the suction pipe
150
. The annular frame
152
extends across water flows
156
in a water channel which are directed toward a suction port
150
a
defined in the lower end of the suction pipe
150
, for thereby producing a turbulent layer
158
which extends from the frame
152
to the suction port
150
a
to prevent an air entrained vortex from being produced.
FIGS. 36A and 36B
of the accompanying drawings show still another vortex prevention structure. The vortex prevention structure comprises an inlet water channel casing
160
in the form of a rectangular box having a laterally open inlet port
160
a
and an upwardly open connection port
160
b
and defining a closed water channel
162
therein. The inlet water channel casing
160
is placed in an open-type pump pit
10
in such a manner that the inlet port
160
a
is directed upstream, and the connection port
160
b
is joined to the suction port
14
a
of the suction bell mouth
14
.
With the conventional arrangement shown in
FIGS. 33A and 33B
, it is necessary to attach the vortex prevention plate
16
and the splitter
18
to the peripheral wall
10
a
and the bottom wall
10
b
of the pump pit
10
and install them in the pump pit
10
. Therefore, a civil engineering work is needed to install the vortex prevention plate
16
and the splitter
18
, and hence the construction cost of the arrangement shown in
FIGS. 33A and 33B
is very high. Furthermore, it is very difficult to add the vortex prevention plate
16
and the splitter
18
to the peripheral wall and the bottom wall of an existing pump pit.
With the conventional structure shown in
FIGS. 34A
,
34
B and
35
, if a vortex filament extending from the water surface where an air entrained vortex is formed to the suction port passes through a portion near the inside of the frame
152
, like a vortex filament
2
A, the vortex filament
2
A is disturbed by a turbulent layer
158
of wake flow produced by the frame
152
, and hence the air entrained vortex becomes unstable and tends to collapse. However, since the air entrained vortex is produced so as to avoid the frame
152
as an obstacle, a vortex filament
1
A extending from a portion near the suction pipe
150
to the suction port
150
a
and a vortex filament
3
A extending from a portion outside of the frame
152
to the suction port
150
a
are mostly produced at positions away from the frame
152
. Therefore, the vortex filaments
1
A,
3
A are hardly affected by the turbulent layer
158
, and hence the vortex prevention capability is presumably small.
The conventional structure shown in
FIGS. 36A and 36B
can suppress the generation of air entrained vortexes at the free surface to a certain extent because the distance from the suction port
14
a
to the free surface is long and the velocity of water flowing through the inlet port
160
a
is considerably lower than the velocity of water flowing through the suction port
14
a
. If the velocity V of water in the channel increases, then there arises an air entrained vortex A which has a vortex filament L extending from the free surface to the suction port
14
a
through the inlet port
160
a
and the closed water channel
162
.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a vortex prevention apparatus which is capable of preventing air entrained vortexes from being generated in a pump pit with a relatively simple arrangement, without requiring a civil engineering work.
Another object of the present invention is to provide a vortex prevention apparatus which is capable of preventing air entrained vortexes from being generated in a pump pit with a relatively simple arrangement, even if water flows in a water channel at an increased velocity.
According to an aspect of the present invention, there is provided a vortex prevention apparatus comprising: a suction member disposed in an open water channel and having a suction port; and an auxiliary flow-path forming structure disposed substantially concentrically around the suction member with a gap defined between the auxiliary flow-path forming structure and an outer circumferential surface of the suction member, the auxiliary flow-path forming structure defining an auxiliary flow path.
With the above arrangement, a water flow directed from a water surface side toward the suction port is divided into a main flow and an auxiliary flow along the auxiliary flow path, so that locally intense downward flows which is a cause of an air entrained vortex will not be produced. A vortex prevention capability is achieved simply by placing the auxiliary flow-path forming structure or member around the suction member. Therefore, it is not necessary to perform a civil construction work to attach a vortex
Enomoto Takashi
Kato Hiroyuki
Tagomori Masashi
Tomita Tsuyoshi
Armstrong Westerman & Hattori, LLP
Ebara Corporation
Kershteyn Igor
Look Edward K.
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