JPS61160695A - Crossed piping structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a loss piping structure such as a header installed in a recirculation system of a boiling water nuclear reactor.

(Technical Background of the Invention) FIG. 6 shows an outline of a general boiling water reactor, in which a reactor core 2 is formed in a reactor pressure vessel 1 slightly below the center position in the vertical direction. There is. A steam separator 3 is installed above the core 2, and the steam separated by the steam separator 3 is passed through a pipe 4 to a turbine (
(not shown). Further, feed water heated by a feed water heater (not shown) is returned into the reactor pressure vessel 1 through a pipe 5.

A plurality of jet pumps 7 are arranged in the reactor pressure vessel 1 so as to surround the reactor core 2, and are configured to circulate the coolant in the reactor pressure vessel 1 so as to pass through the reactor core 2. It has become. For this reason, a pair of recirculation systems 8 are provided outside the reactor pressure vessel 1 for supplying the coolant in this vessel 1 to the jet pumps 7, and each recirculation system 8 is equipped with a recirculation pump. 9 is interposed, and this recirculation pump 9
A header 10 for distributing coolant to each jet pump 7 is provided downstream of the jet pump 7 .

As shown in FIG. 7, this header 10 is symmetrical to the left and right so that the circulating water from the recirculation pump is uniformly supplied to each jet pump, and the cross piping section 17 supplies the circulating water from below. A downstream straight pipe 18 and left and right branch pipes 1 as riser pipes that supply to one jet pump above.
2A and 12B, and branch pipes 19A and 2OA as riser pipes protrude from the branch pipe 12A, respectively.

The header 10 will be described in detail in FIGS. 8 and 9.
As shown in the figure, it has a cylindrical straight pipe 11, and this straight pipe 11
A pair of branch pipes 12A and 12B having a diameter smaller than that of the straight pipe 11 are connected to the same position in the axial direction. The connection positions of both branch pipes 12A and 12B to the straight pipe 11 are such that one branch pipe 12A is offset in the circumferential direction of the straight pipe 11 with respect to the axis of the other branch pipe 12B. That is, as shown in detail in FIG. 8, both branch pipes 12A.

12B ll! L, L8 is the diameter line of straight pipe 11 ^ On the other hand, they are connected so as to be shifted by an angle α in the same direction.

The lower end of the straight pipe 11 is an inlet part 13, and the coolant flows from the bottom to the top.
4 has its diameter gradually reduced by a reducer 15 serving as a throttle tube.

[Problems with background technology]

In a loss piping structure like the header 10 described above, as shown in FIG. 10A, B, and C, the inlet! ! 113,
And, due to the uneven flow a of the coolant at the cross section 16 where both branch pipes 12A and 12B intersect with the straight pipe 11, the cross section 16
A swirling flow of the coolant occurs from there to the branch pipes 12A and 12B. Furthermore, due to changes in the flow of the coolant upstream and downstream, this swirling flow changes to a biased flow C directly below the branch pipes 12A and 12B as shown in the fifth diagram, resulting in a state in which there is no swirling flow.

Therefore, in such a loss piping structure, since the presence or absence of swirling flow is irregularly repeated, the branch pipe 12A
, 12B fluctuates significantly, making it impossible to obtain a stable branched flow rate. Further, there is also a problem in that pressure loss occurs within the branch pipe due to the branch vortex, resulting in a decrease in flow efficiency.

[Purpose of the invention]

The present invention has been developed in view of these circumstances, and it is possible to obtain a stable branch flow rate by eliminating fluctuations in the presence or absence of swirling flow in the branch pipe, and to reduce branch loss by reducing the branch vortex. The purpose is to provide a cross piping structure that can be used.

(Summary of the Invention) In order to achieve the above-mentioned object, the cross piping structure according to the present invention includes a second downstream straight pipe extending in the flow direction on the downstream side of an upstream straight pipe through which fluid flows, and a second downstream straight pipe extending in the flow direction. Multiple small-diameter pipes consisting of branch pipes extending in cross directions,
In the cross piping structure formed by branching and connecting, the upstream straight pipe and the downstream straight pipe are connected via a throttle pipe whose diameter gradually decreases from the upstream side to the downstream side, and the branch pipe is connected to the peripheral wall of the throttle pipe. It is characterized by branching into a section via a connecting section orthogonal thereto. [Embodiments of the Invention] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

In describing this embodiment, the same components as those of the conventional system described above are designated by the same reference numerals in the drawings, and the explanation thereof will be omitted.

1 to 3 show a first embodiment of the present invention, and show a header 2o applied to a recirculation system of a boiling water reactor as an example of a cross piping structure. This header 20 has an upstream straight pipe 21 through which reactor water as a fluid flows from below to above.
A small-diameter downstream straight pipe 22 as a riser pipe is connected to this upstream straight pipe 21 in the flow direction, that is, in the coaxial direction (upward). Further, a pair of small-diameter branch pipes 23A and 23B extending in a cross direction (lateral direction) intersecting the flow are connected to the upstream straight pipe 21.

In this, the upstream straight pipe 21 and the downstream straight pipe 22 are connected by a truncated conical throttle pipe 24 as a reducer whose diameter gradually decreases from the upstream side to the downstream side. The branch pipes 23A and 23B are connected to each other through connection parts 23'A and 23'B that are perpendicular to the peripheral wall of the throttle pipe 24. That is, each branch pipe 23A, 23B extends in the horizontal direction as a whole, and the connecting portions 23'A, 23
' B is perpendicular to the circumferential wall of the throttle pipe 24 via the elbows 23 "A, 23 "B (has an inclined bent shape. Note that each branch pipe 23A, 23B has a riser pipe The branch pipes 25 are arranged one pair at a time in a direction parallel to the downstream straight pipe 22 (
It protrudes upward) at intervals of aJ.

Since five riser pipes are provided in total, the diameters of the downstream straight pipe 22 and each branch pipe 25 as riser pipes are set to 115 of the upstream straight pipe 21, respectively. Thereby, the flow velocity is determined based on the flow rate ratio, and the flow velocity in the branch pipes 23A, 23B is prevented from becoming slower than the flow velocity in the upstream straight pipe 21. In other words, the generation of vortices that impede smooth flow becomes noticeable when the flow velocity is slower at the branch than on the upstream side. Therefore, branch pipe 23
The pipe diameter is set based on the flow rate ratio so that the flow velocity in A and 23B is not lower than the flow on the inlet side of the upstream straight pipe 21, thereby preventing the generation of vortices. For example, since the flow rate of the coolant flowing straight from the upstream straight pipe 21 to the downstream station IF 22 is 115, the downstream straight pipe 22
In order to keep the flow velocity at the connection part of each branch pipe 23A, 23B, that is, the flow velocity at the cross piping part 26 from becoming slow, the area ratio of the pipe diameter at the inlet and outlet part of the throttle pipe 24 is set to 1:5.
It is set to .

With such a configuration, the flow condition in the cross piping section 26 becomes smooth as shown in FIG. 3. That is, the flow of the coolant introduced into the inlet portion 21a of the upstream straight pipe 21 reaches the downstream straight pipe 22 and each branch pipe 23A, 23B via the throttle pipe 24, but the flow path is interrupted by the throttle pipe 24. The area gradually decreases toward the downstream side, and the branch connecting portions 23'A, 23'B of each branch pipe 23A, 23B
Since the direction is perpendicular to the peripheral wall of the throttle pipe 24, that is, close to the flow direction in the upstream straight pipe 21, a reasonable branched flow can be provided, the flow velocity is constant, and turbulence is prevented. This results in a smooth flow with almost no occurrence of.

In addition, each branch pipe 23A, 23B has a connection part 23'A, 23
' Since the curvature along the side wall of the reactor pressure vessel 1 can be imparted to any part of B or the extension part, the throttle pipe 2
Each branch pipe 23A opens to 4.

The angle formed by the connecting parts 23'A and 23'B of 23B may be 180° in a plane, or a predetermined angle α that makes an intersection of 180° or less along the tangential direction of the outer circumference of the reactor pressure vessel 1.
(See FIG. 9).

FIG. 4 shows a second embodiment of the invention.

In this embodiment, each of the branch pipes 23A and 23B extends linearly in a direction perpendicular to the peripheral wall of the throttle pipe 24. Each branch pipe 25 as a riser pipe includes a branch pipe 23A,
23B protrudes so as to become gradually shorter at each tip end side. That is, in order to make the installation height of each riser pipe top in the reactor constant, the length of the rise from the branch pipes 23A and 23B is measured upstream! The further away from 21, the shorter it becomes.

According to such a configuration, the branch pipe 23A rising diagonally,
The branch pipe 25 projects vertically with respect to the branch pipe 23B, and the bending angle at which the coolant flowing from the upstream straight pipe 21 flows out from the branch pipes 23A and 23B to the branch 125 is an obtuse angle. therefore,
The branching angle becomes gentler with respect to the flow, which has the effect of reducing branching loss.

FIG. 5 shows a third embodiment of the present invention (FIG. 5(b)) in comparison with a conventional example (FIG. 5(a)). In this embodiment, for example, the upstream straight pipe 21, the downstream straight pipe 22, and the branch pipe 23A.

23B and the throttle pipe 24 are integrally formed, the outer diameter of the upstream straight pipe 21 and the branch pipe 23A,
The protruding width of the integrally formed portion 23B is made the same. That is, when cutting and forming forged iron with a constant height L as a material, the branch pipes 12A and 12B are configured to protrude from the large diameter portion of the upstream straight pipe 11, as in the conventional example shown in FIG. 5(a). If so, the necessary lengths of the branch pipes 12A and 12B are determined from the diameter of the material, and a large amount of cutting loss A1 is generated in order to cut out the outer diameter d1 of the upstream straight pipe 11. On the other hand, in the case of the present invention, the branch pipes 23A and 23B are made to protrude in a direction perpendicular to the circumferential wall of the throttle pipe 24, which has a small diameter, so that the diameter of the material remains unchanged, as shown in FIG. 5(b). Upstream straight pipe 1
The outer diameter d2 can be set to 1, and the cutting loss A2 is small.

Moreover, since the forged surface can be used as it is as the surface of the molded product, the strength can be improved compared to the conventional case where the cut surface is used as the surface of the molded product.

[Effects of the Invention] As described above, according to the cross piping structure according to the present invention,
The upstream straight pipe and the downstream straight pipe are connected via a constricted pipe whose diameter gradually decreases from the upstream side to the downstream side, and a branch pipe is connected in a direction orthogonal to the peripheral wall of the constricted pipe. While the flow from the side straight pipe is being throttled in the throttle pipe,
It flows in a direction perpendicular to the peripheral wall surface. Therefore, the flow velocity of the branched flow flowing in the direction of the branch pipe is not slowed down, and generation of vortices can be suppressed. In addition, since the branching direction is gentle with respect to the mainstream, the generation of vortices after branching is also prevented, and pressure loss due to the generation of unstable vortices at the cross piping section is prevented.
Smooth branched flow can be obtained.

For example, when applied to the recirculation system of a boiling water reactor, it stabilizes the flow rate of the system, is effective in improving reactor operability, and also reduces the power required for the recirculation pump. , economical efficiency can also be improved.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the first embodiment of the present invention, Fig. 2 is an enlarged view of the main part thereof, Fig. 3 is a sectional view showing the operation, and Fig. 4 is a perspective view showing the second embodiment of the invention. FIG. 5(b) is an explanatory diagram showing the third embodiment of the present invention in comparison with the conventional example (FIG. 5(b)), and FIG. 6 is a perspective view of a general example to which the present invention is applied. A diagram showing a boiling water reactor, Fig. 7 is a perspective view showing a conventional example, Fig. 8 is an enlarged view of its main parts, Fig. 9 is a plan view of Fig. 8, and Fig. 10 is an explanation of the operation in the conventional example. It is a diagram. 21...Upstream straight pipe, 22...Downstream straight pipe, 23A
, 23B...branch pipe, 24...throttle pipe, 23'A
. 23'B...connection part, 25...branch pipe. Figure 2 Figure 4 Figure 5 Figure 6 Figure 7 Figure 10 Procedure correction 8'' (daytime)

Claims (1)

[Claims] 1. A small-diameter pipe consisting of a downstream straight pipe that extends in the flow direction of the upstream straight pipe through which fluid flows, and a branch pipe that extends in the cross direction that intersects the flow. In a cross piping structure formed by branching and connecting a plurality of pipes, the upstream straight pipe and the downstream straight pipe are connected via a throttle pipe whose diameter gradually decreases from the upstream side to the downstream side, and the branch pipe is A cross piping structure characterized in that the throttle pipe is connected to the peripheral wall portion of the throttle pipe via a connecting portion perpendicular thereto. 2. The cross according to claim 1, wherein the diameters of the downstream straight pipe and the branch pipe are set based on a flow rate ratio in which the flow velocity in each pipe is not lower than the flow velocity in the upstream straight pipe. Piping structure. 3. The entire branch pipe extends linearly in a direction perpendicular to the circumferential wall of the throttle pipe, and a plurality of branch pipes parallel to the downstream straight pipe protrude from the branch pipe at intervals. Cross piping structure as described in scope 1. 4. At least each connection portion of the upstream straight pipe, throttle pipe, and branch pipe is integrally formed from the same material, and the outer diameter of the upstream straight pipe and the protruding width of the integrally formed portion of the branch pipe are the same. A cross piping structure according to claim 1.