Suction elbow provided with built-in guide blades

Details Suction elbow provided with built-in guide blades Suction elbow provided with built-in guide blades

1999-05-14

2001-09-18

Luu, Teri Pham (Department: 3627)

Pipe joints or couplings

Connector for conduit housing electromagnetic line:

Having box and connector

C285S179000, C285S179000, C138S039000, C406S191000, C406S195000

Reexamination Certificate

active

06290266

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a suction elbow provided with guide vanes to be disposed in an inlet port of a pipe line, a duct, a range hood, a canopy hood, a suction floor of a clean room, etc.
BACKGROUND ART
A various kinds of measures such as the installation of a flow resistor such as a perforated panel, a baffle plate, etc., the installation of a large number of inlet ports, the installation of a large volume of suction space under the floor, etc. have been taken in order to achieve a uniform distribution of sucked fluid velocity at an inlet port.
Those conventional measures can not actually achieve uniform distribution of sucked fluid velocity and have problems such as increase of pressure loss, increase of equipment cost, etc.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a suction elbow which can achieve uniform distribution of sucked fluid velocity, small pressure loss, simple structure and no increase of equipment cost, and can be equally applied to expansion, normal, and reduction elbows.
According to the present invention, there is provided a suction elbow provided with guide vanes, wherein one or more guide vanes made of a curved plate and flat plates connected to the curved plate are disposed to make the shapes of the sub-channels defined thereby similar to each other based on the following formulas.
p
0
=h/{[f/(f−r)]
m
−1}  {circle around (1)}
a
n
=p
0
r[f/(f−r)]
n
  {circle around (2)}
b
n
=a
n
/f  {circle around (3)}
p
0
: overhang length at the inlet of the elbow
h: outlet breadth of the elbow
f: reduction ratio of the elbow (f=W/h)
W: inlet breadth of the elbow
m: number of sub-channels (m≧2)
a
n
: inlet breadth of n-th sub-channel (a
0
indicates the radius of curvature of the inner side wall and a
m
indicates the radius of curvature of the outer side wall)
r: aspect ratio of the sub-channels
b
n
: outlet breadth of n-th sub-channel
Derivation of formulas {circle around (1)} to {circle around (3)} will be described based on FIG.
1
.
In
FIG. 1
, reference numeral
1
indicates a base elbow B
1
E
2
B
5
E
1
,
2
indicates the outlet of the elbow,
3
indicates the inlet of the elbow,
4
indicates the inner side wall of the elbow,
5
,
6
and
7
indicate No. 1 guide vane, No. 2 guide vane and No. 3 guide vane, and
8
indicates the outer side wall of the elbow. Reference letter W indicates inlet breadth of the elbow, and reference letter h indicates outlet breadth of the elbow.
The sub-channels defined in the elbow are similar to each other. Thus, the reduction ratio f of the elbow is expressed as follows.
f=W/h=(a
1
+a
2
+a
3
+. . . )/(b
1
+b
2
+b
3
+. . . )=a
1
/b
1
=a
2
/b
2
=a
3
/b
3
=. . . =a
n
/b
n
The rectangle lengths p
n
of the sub-channels are expressed as follows.
p
1
=p
0
+b
1
, p
2
=p
0
+b
1
+b
2
, p
3
=p
0
+b
1
+b
2
+b
3
, . . .
p
n
=p
0
+b
1
+b
2
+b
3
+. . . +b
n
The aspect ratio r of the sub-channels is expressed as follows.
r=a
0
/p
0
=a
1
/p
1
=a
2
/p
2
a
3
/p
3
=. . . =a
n
/p
n
From the above equations, the formulas {circle around (1)} to {circle around (3)} are derived for obtaining the overhang length po at the inlet of the elbow, the inlet breadth a
n
of n-th sub-channel, and the outlet breadth b
n
of n-th sub-channel based on given values of the outlet breadth h, the inlet breadth W, the number of sub-channels m and the aspect ratio r of the sub-channels.
Configurations of the guide vanes
5
to
7
, the inner side wall
4
of the elbow and the outer side wall
8
of the elbow can be determined based on the formulas {circle around (1)} to {circle around (3)} as follows.
Based on the overhang length p
0
at the inlet of the elbow, the inlet breadth a
n
of n-th sub-channel, and the outlet breadth b
n
of n-th sub-channel, which are obtained from the formulas {circle around (1)} to {circle around (3)}, rectangles A
0
A
1
B
1
C
0
, A
1
A
2
B
2
C
1
, A
2
A
3
B
3
C
2
, A
3
A
4
B
4
C
3
and A
4
A
5
B
5
C
4
are determined, as shown in FIG.
1
. Circular arcs R
0
, R
1
, R
2
, R
3
and R
4
which respectively touch internally the above rectangles are determined. Circular arcs are determined as follows. R
0
=a
0
, R
1
=a
1
, R
2
=a
2
, R
3
=a
3
and R
4
=a
4
.
The line B
2
C
1
is extended by a length equal to that of the line B
1
C
0
so as to determine a line C
1
D
0
. The line B
3
C
2
is extended by a length equal to that of the line B
2
C
1
so as to determine a line C
2
D
1
. The line B
4
C
3
is extended by a length equal to that of the line B
3
C
2
so as to determine a line C
3
D
2
. The line B
1
C
0
is extended by an appropriate length so as to determine a line C
0
F
1
. The line B
5
E
1
is extended by a length equal to that of the line B
1
F
1
so as to determine a line E
1
F
2
.
Thus, No. 1 guide vane
5
(D
0
C
1
A
2
), No. 2 guide vane
6
(D
1
C
2
A
3
), No. 3 guide vane
7
(D
2
C
3
A
4
), inner side wall
4
(F
1
C
0
A
1
) and outer side wall
8
(F
2
C
4
A
5
) are determined. As a result, there is obtained a suction elbow provided with guide vanes which is divided by No. 1 guide vane
5
(D
0
C
1
A
2
), No. 2 guide vane
6
(D
1
C
2
A
3
) and No. 3 guide vane
7
(D
2
C
3
A
4
) into sub-channels C
0
A
1
A
2
D
0
, C
1
A
2
A
3
D
1
, C
2
A
3
A
4
D
2
and C
3
A
4
A
5
D
3
that are similar to each other.
A reduction elbow is obtained when the reduction ratio f is f>1, a normal elbow is obtained when the reduction ratio f is f=1 and an expansion elbow is obtained when the reduction ratio f is f<1. Usually, a reduction elbow or a normal elbow is used as a suction elbow.
In a bent duct such as an elbow, flow of sucked fluid becomes a free vortex flow. In a free vortex flow, RV=constant (R: radius of flow, V: flow velocity). Thus, the velocity of sucked fluid at the inlet of an elbow increases from the outer side wall to the inner side wall. In the present invention, a suction elbow is divided into a plurality of similarly shaped sub-channels which decrease in size from the sub-channel near the outer side wall of the elbow toward the sub-channel near the inner side wall of the elbow. Thus, the ratio of the side wall length of the sub-channel to the sectional area of the sub-channel increases from that in the sub-channel near the outer side wall of the elbow toward that in the sub-channel near the inner side wall of the elbow. The flow resistance in the sub-channels therefore increases from that in the sub-channel near the outer side wall of the elbow toward that in the sub-channel near the inner side wall of the elbow. Thus, the velocity distribution of a free vortex flow and the flow resistance distribution cancel each other to uniformize the velocity distribution of sucked fluid velocity over the whole width of the inlet of the suction elbow.
Usually, a suction elbow in accordance with the present invention is used as a reduction elbow or a normal elbow. No pressure loss due to a vortex flow is generated when a suction elbow provided with guide vanes in accordance with the present invention is used as a reduction elbow or a normal elbow because a vortex flow is generated in an expansion channel. Thus, a suction elbow in accordance with the present invention generates only a small pressure loss.
A suction elbow provided with guide vanes in accordance with the present invention has a simple structure and does not cause increase of equipment cost.
A suction elbow provided with guide vanes in accordance with the present invention can be applied to a reduction elbow, a normal elbow and an expansion elbow.


REFERENCES:
patent: 2216046 (1940-09-01), Peck
patent: 4209192 (1980-06-01), Knight
patent: 4919170 (1990-04-01), Kallinich et al.
patent: 4974881 (1990-12-01), Engel et al.
patent: 742475 (1943-10-01), None
patent: 0 667 46

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