The present invention relates to a pipe for a driven-type fluid machine and is a pipe devised to enable space-saving.
Petrochemical, chemical, air separation plants and other plants use many centrifugal compressors. One type of such centrifugal compressors is a single-shaft multi-stage centrifugal compressor. The single-shaft multi-stage centrifugal compressor includes a plurality of impellers on a single shaft at a plurality of stages along the axial direction and compresses a fluid in a stepwise manner.
Now, an example of the disposed state of a single-shaft multi-stage centrifugal compressor with a pipe that supplies a fluid thereto will be described with reference to
As illustrated in both figures, a single-shaft multi-stage centrifugal compressor 3 is supported by a mount installed on a base (ground) 1. In other words, the single-shaft multi-stage centrifugal compressor 3 is placed above the base (ground) 1 as viewed from it. A fluid is supplied to this single-shaft multi-stage centrifugal compressor 3 through a supply pipe 11 disposed horizontally along the base 1, a bend (bent pipe) 12, and an inlet pipe 13 disposed vertically. These supply pipe 11, bend 12, and inlet pipe 13 are circular pipes (tubular members whose cross-sectional shapes perpendicular to the tube axis are circular). Note that the inlet pipe 13 is a pipe connected to a suction port provided in a casing of the single-shaft multi-stage centrifugal compressor 3 and extends vertically downward as viewed from the casing.
The fluid supplied through the supply pipe 11 bends the direction of travel by 90° at the bend 12 and then flows through the inlet pipe 13. Since the fluid flows through the bend 12 while bending, a flow speed V1 on an inner periphery side of the bend 12 and a flow speed V2 on an outer periphery side of the bend 12 are different from each other, as illustrated in
As mentioned above, the inlet pipe 13 is provided to weaken the swirling and the like caused by flows through the bend 12. To achieve such an effect, the axial length of the inlet pipe 13 is usually (conventionally) set to satisfy L≥3D, where D is the diameter (inside diameter) of the supply pipe 11 and L is the axial length of the inlet pipe 13.
Note that, if the axial length of the inlet pipe 13 is insufficient, the turbulent fluid with the swirling and the like will be sucked into the single-shaft multi-stage centrifugal compressor 3. This will lower the performance of the compressor and also reduce the operation range. For this reason, the axial length of the inlet pipe 13 must not be insufficient.
As mentioned above, in order to supply the fluid to the single-shaft multi-stage centrifugal compressor 3 after its flow speed is made substantially uniform, the inlet pipe 13 with a long axial length has been conventionally used. This requires for the mount 2 to be tall and leads to a problem that a disposition height H of the single-shaft multi-stage centrifugal compressor 3 is high. There is also a disadvantage that accompanying structural components have to be large.
The above example has been described about a single-shaft multi-stage centrifugal compressor. However, the problem of an inlet pipe's long axial length exists also in the case of supplying a fluid to a driven-type fluid machine such as a compressor, a pump, or an air blower, which converts mechanical work into fluid-dynamic energy, through a supply pipe, a bend, and an inlet pipe.
In view of the above conventional technique, the present invention is characterized by providing a pipe for a driven-type fluid machine devised to be capable of reliably reducing turbulence in a fluid and also shortening the axial length of an inlet pipe, thus allowing space-saving, by devising the shape of the pipe for the driven-type fluid machine.
The present invention for solving the above-described problem is a pipe for a driven-type fluid machine, the pipe including an inlet pipe that is to be connected to a suction port provided in a casing of the driven-type fluid machine, a supply pipe that supplies a fluid, and a bend that connects the supply pipe and the inlet pipe to each other, characterized in that the bend is shaped such that a pipe width in a plane including a pipe axis of the inlet pipe and a pipe axis of the supply pipe gradually decreases from an upstream portion to a bent portion.
Also, the present invention is characterized in that the bend is shaped such that the pipe width in the plane including the pipe axis of the inlet pipe and the pipe axis of the supply pipe gradually decreases from the upstream portion to the bent portion and a pipe width in a plane being perpendicular to the plane including the pipe axis of the inlet pipe and the pipe axis of the supply pipe and including the pipe axis of the inlet pipe gradually increases from the upstream portion to the bent portion.
Also, the present invention is characterized in that a pipe cross-sectional area of the bend remains constant from the upstream portion to the bent portion.
Also, the present invention is characterized in that inside the bend, a plate-shaped flow straightening member is disposed which is disposed along a direction of flow of the fluid to guide the fluid.
Also, the present invention is characterized in that
the driven-type fluid machine is a single-shaft multi-stage centrifugal compressor,
the inlet pipe is disposed vertically, and
the supply pipe is disposed horizontally.
According to the present invention, the bend portion is shaped such that the pipe width in the plane including the pipe axis of the inlet pipe and the pipe axis of the supply pipe gradually decreases from the upstream portion to the bent portion. This reduces turbulence such as swirling occurring at the bent portion. Accordingly, the length of the inlet pipe can be shortened. Hence, space-saving can be achieved.
Now, a pipe for a driven-type fluid machine according to the present invention will be described in detail based on embodiments.
In embodiment 1, an example where a single-shaft multi-stage centrifugal compressor is employed as the driven-type fluid machine will be discussed.
As illustrated in both figures, a single-shaft multi-stage centrifugal compressor 3 is supported by a mount installed on a base (ground) 1. In other words, the single-shaft multi-stage centrifugal compressor 3 is placed above the base (ground) 1 as viewed from it.
A fluid is supplied to the single-shaft multi-stage centrifugal compressor 3 through a supply pipe 111 disposed horizontally along the base 1, a bend (bent pipe) 112, and an inlet pipe 113 being a straight pipe disposed vertically.
The inlet pipe 113 is a pipe connected to a suction port 3b provided in a casing 3a of the single-shaft multi-stage centrifugal compressor 3 and extends vertically downward as viewed from the casing 3a. The supply pipe 111 and the inlet pipe 113 are connected by the bend 112, and the fluid supplied through the supply pipe 111 bends the direction of travel by 90° at the bend 112 and then flows through the inlet pipe 113. The fluid is then sucked into the single-shaft multi-stage centrifugal compressor 3.
The pipe shape of the supply pipe 111 is similar to the conventional one, or a circular pipe (a tubular member whose cross-sectional shape perpendicular to the tube axis is circular). However, the pipe shapes of the bend 112 and the inlet pipe 113 are different from the conventional one.
First, planes necessary to specify the shapes of the bend 112 and the inlet pipe 113 will be described.
(1) A vertical cross-sectional plane in this example is a plane including the pipe axis of the vertically disposed inlet pipe 113 and the pipe axis of the horizontally disposed supply pipe 111.
(2) A horizontal cross-sectional plane in this example is a plane being perpendicular to the plane including the pipe axis of the vertically disposed inlet pipe 113 and the pipe axis of the horizontally disposed supply pipe 111 (vertical cross-sectional plane) and including the pipe axis of the supply pipe 111.
The shape of the bend 112 will be described with reference to
As illustrated in
(1) The pipe width of the bend 112 in the vertical cross-sectional plane gradually decreases from D to d from the upstream portion 112a to the bent portion 112b (see
(2) The pipe width of the bend 112 in pipe width in the horizontal cross-sectional plane gradually increases from H (=D) to h from the upstream portion 112a to the bent portion 112b (see
Moreover, the pipe cross-sectional area of the bend 112 remains constant from the upstream portion 112a to the bent portion 112b (the cross-sectional areas illustrated in
The cross-sectional shape of the downstream portion 112c is as
Thus, the pipe width of the bent portion 112b of the bend 112 in the vertical plane is d, which is narrow. Accordingly, as illustrated in
Meanwhile, in the conventional technique, the pipe width of the bent portion of the bend is D, which is large, as illustrated in
Also, the pipe cross-sectional area of the bend 112 remains constant from the upstream portion 112a to the bent portion 112b and further to the downstream portion 112c. Thus, the flow speed of the fluid flowing from the upstream portion 112a through the bent portion 112b to the downstream portion 112c remains constant from the upstream portion 112a through the bent portion 112b to the downstream portion 112c.
The cross-sectional shape of the inlet pipe 113 (see
Note that L≥3×D in the conventional technique, and the axial length of the inlet pipe is long.
As described above, at the bend 112, the fluid flows at a constant speed and also the occurrence of swirling and separation decreases. The occurrence of the swirling and the like at the downstream portion 112c of the bend 112 is determined by the pipe width d. Then, with the axial length L1 of the inlet pipe 113 satisfying L1≥3×d, it is possible to achieve a flow straightening effect equivalent to that achieved when L≥3×D as in the conventional technique.
As described above, it is possible to achieve a fluid flow straightening effect while also making the axial length L1 of the inlet pipe 113 shorter than that in the conventional technique. Accordingly, a disposition height H1 of the single-shaft multi-stage centrifugal compressor 3 (see
In the above-described example, the pipe cross-sectional area remains constant from the upstream portion 112a to the bent portion 112b and further to the downstream portion 112c. Note, however, that the pipe cross-sectional area may gradually decrease from the upstream portion 112a to the bent portion 112b. In this case, the flow speed of the fluid flowing through the bend 112 is accelerated.
Also, in a case where the inlet pipe 113 is connected to the casing 3a such that h of the inlet pipe 113 (see
Next, further improved versions of the bend 112, employed in embodiment 1, will be described as embodiment 2.
A bend 112 illustrated in
A bend 112 illustrated in
By incorporating the bent plates 112a or the bent plate structure 114 inside the bend 112 as above, the occurrence of the swirling and separation can be reduced further. Since the occurrence of the swirling and the like can be thus reduced further, the axial length of the inlet pipe 113 can be shortened further.
The above-described embodiments are examples in which the supply pipe is disposed horizontally and the inlet pipe is disposed vertically. However, the present invention is also applicable to a pipe with a supply pipe and an inlet pipe both disposed horizontally and a bend connecting the supply pipe and the inlet pipe.
In this case, the bend is shaped such that:
(1) the pipe width in the horizontal cross-sectional plane gradually decreases from the upstream portion to the bent portion; and
(2) the pipe width in the vertical cross-sectional plane gradually increases from the upstream portion to the bent portion.
Also, in the present invention, the bend may just need to be shaped such that the pipe width in the plane including the pipe axis of the inlet pipe and the pipe axis of the supply pipe gradually decreases from the upstream portion to the bent portion.
Further, in the present invention, the bend is preferably shaped such that the pipe width in the plane including the pipe axis of the inlet pipe and the pipe axis of the supply pipe gradually decreases from the upstream portion to the bent portion and the pipe width in the plane being perpendicular to the plane including the pipe axis of the inlet pipe and the pipe axis of the supply pipe and including the pipe axis of the inlet pipe gradually increases from the upstream portion to the bent portion.
Furthermore, in the present invention, the pipe cross-sectional area preferably remains constant from the upstream portion to the bent portion.
The present invention is applicable to pipes that supply fluids to driven-type fluid machines such as a pump and an air blower as well as a compressor, which convert mechanical work into fluid-dynamic energy.
Number | Date | Country | Kind |
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2016-010522 | Jan 2016 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2017/001663 | 1/19/2017 | WO | 00 |