JP2953812B2 - Bleed tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the Invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bleed pipe which leads to a moisture separator in a bleed system in which steam containing moisture flows in a nuclear power plant.

[0003]

2. Description of the Related Art In a conventional nuclear power plant, an example of application to a moisture separator of an extraction system in which steam containing moisture flows will be described. For example, a boiling water nuclear power plant has a system configuration as shown in FIG. That is, the main steam generated in the reactor 11 is about 68 kg / cm
The saturated steam of ² abs flows into the inlet of the high-pressure turbine 13 through the main steam pipe 12. This high pressure turbine 13
The steam which has been worked in the above becomes wet steam of about 12% to 13% at the time of rated operation, and flows into the cross-around pipe 14 from its outlet. Therefore, this cross-around tube 1
The flow of the fluid in 4 is a gas-liquid two-phase flow, which is a so-called "annular spray flow" in which a liquid film flows on the wall surface of the tube and droplets flow in the tube. Therefore, a moisture separator 15 is connected to the cross-around pipe 14 in order to remove these moisture from the steam, and the gas-liquid two-phase flow flowing into the moisture separator 15 through the cross-around pipe 14 is , Separated into liquid and vapor. Here, the separated steam is introduced into the inlets of the low-pressure turbines 17a and 17b, and the liquid flows into the high-pressure feed water heater 23b through the M / S drain pipe 16, where heat is recovered. I have.

On the other hand, the steam that has been working in the low-pressure turbines 17a and 17b and has driven the generator 18 is supplied to the low-pressure turbine 17a.
The water flows out of the outlets a and 17b and enters the condenser 19 to be condensed and condensed. This condensate is supplied to the condensate pump 20,
Water heaters 21a, 21b, 21c, reactor feed pump 2
2 and high pressure feed water heaters 23a and 23b
Return to 1. Further, steam is supplied from the high-pressure turbine 13 and the low-pressure turbines 17a, 17b to the bleed tubes 24a, 24b, 24.
high pressure feed water heater 2 bleed through c, 24d, 24e
3a, 23b and low pressure feedwater heaters 21a, 21b, 2
1c respectively to heat the condensate and feed water.
The extracted steam from these turbines is wet steam,
The flow of the fluid in the bleed tubes 24a, 24b, 24c, 24d, 24e is a gas-liquid two-phase flow having a wetness of 4% to 40%.

Further, in the nuclear power plant, due to the arrangement of the equipment, the cross-around pipe 14 connected to the moisture separator 15 and the bleed pipes 24a, 2 entering each feed water heater.
4b, 24c, 24d, and 24e may be branched.
FIG. 6 shows an example of a gas-liquid two-phase flow branch pipe.
Here, two moisture separators 15 are provided from the high pressure turbine 13.
The cross-around pipe 14 is bifurcated using a Y-branch pipe 26 in order to distribute the wet steam to the a and 15b. The steam from which the moisture has been separated is supplied to the low-pressure turbines 17a and 17b, and the liquid is subjected to M / S
It is discharged from the drain pipe 16.

[0006]

As described above, the conventional method of branching the gas-liquid two-phase flow by the Y branch pipe 26 uses the same method as the method of distributing a single-phase flow of only steam. The piping configuration is such that the loss after branching is adjusted so that the same amount of steam flows into each moisture separator. However, recent results of steam-water distribution test using a T-junction for gas-liquid two-phase flow (MT Rubel, et al,
"Phase Distribution during Steam-water Flow in a
Horizontal T-junction ", Int. J. Multiphase Flow, V
ol. 14, No. 425-438, 1988), suggests that the distribution ratio of steam and water is not the same, and that the distribution ratio of steam and water after branching varies depending on the humidity and distribution ratio. doing.

FIG. 4A shows a schematic configuration of a test apparatus for measuring a distribution ratio of a steam amount and a water amount in a gas-liquid two-phase flow branch pipe. This test apparatus has a T-joint configuration including an upstream mother pipe 7, a downstream mother pipe 8, and a branch pipe 9 branched from the upstream mother pipe 7 and the downstream mother pipe 8 at right angles. The amount of steam W _G1 flowing through the upstream main pipe 7 as measured by the test apparatus, water W _L1, also branch pipe 9
Steam amount flowing W _G3, before branching from water W _L3 upstream header tube 7
FIG. 4B shows the relationship based on the test results of the steam distribution ratio ( _WG3 / _WG1 ) and the water distribution ratio ( _WL3 / _WL1 ) of the branch pipe 9 after branching. In FIG. 4B, the horizontal axis shows the water amount distribution ratio (W _L3 / W _L1 ), and the vertical axis shows the steam amount distribution ratio (W _G3 / W _G1 ). Here, W _G3 / W _G1 =
When W _L3 / W _L1 = 1, it indicates a case where the entire flow rate flows through the branch pipe 9. In addition, a 45 ° oblique line in FIG. 4B indicates a case where the steam amount and the water amount are separated at the same ratio.

[0008] The test results are for a case where the apparent average flow velocity of the steam is V _Gs = 18.2 m / s. Here, when the wetness of the steam is small (the data indicated by the + mark in FIG. 4B (the apparent average flow velocity of water (droplets) is V _Ls = 0.0054).
4m / s)), the distribution ratio of the steam amount and the water amount almost overlaps the 45 ° oblique line, and both are distributed at substantially the same ratio. However, when the wetness increases (shown in FIG. 4 (b) ◇ indicia (V _Ls = 0.0198m / s) and symbol □ Data _{(V Ls = 0.0342m / s)} ), flows into the branch pipe 9 The amount of water is smaller than the amount of steam. ◇ mark of data (V _Ls = 0.
0198 m / s), when the steam amount distribution ratio is 0.5,
The water volume distribution ratio is 0.22, which indicates that the distribution ratio of the water volume has a considerable deviation as the wetness increases.

[0009] Also, a report on the results of an annular two-phase flow distribution test of another T-branch tube (BJ Azzopardi, et al, "ANNULAR TWO-PHA
SE FLOW SPLIT AT AN IMPACTING T ", Int. J. Multipha
se Flow Vol. 13 No. 5 pp605-614, 1987) shows that the presence of a bend on the upstream side of the T-branch pipe further affects the water distribution ratio and causes considerable deviation.

As described above, the distribution of the gas-liquid two-phase flow by the branch pipe indicates that the distribution of the moisture is not always the same even if the distribution amount of the vapor is the same, unlike the distribution of the single-phase vapor flow. Moreover, the piping route of the nuclear power plant is difficult to secure a sufficient straight pipe distance on the upstream side of the branch pipe due to the layout.Therefore, the bent section is arranged on the upstream side of the branch section. It tends to promote bias. These differences in the distribution ratio of steam and water, especially when the wetness of the steam is high, result in wetness other than the design point of each device of the nuclear power plant, causing a problem in its performance. Further, the deviation due to the distribution of the water amount appears as a deviation in the separated drain amount (water amount) in the moisture separator, and may cause imbalance in the drain system. Further, in the gas-liquid two-phase flow pipe, a problem of wall thickness reduction of the pipe inner wall due to erosion and corrosion has conventionally occurred. This depends on the flow velocity, wetness, temperature, water quality,
This is because the progression rate of wall thinning of the pipe inner wall differs depending on the pipe shape and the like, and particularly with respect to the wetness of steam, when the other conditions are the same, the thinner the wettability, the greater the thinning rate. In order to avoid these problems, the distribution of the gas-liquid two-phase flow through the branch pipe is different from the distribution of the single-phase vapor flow such that the distribution ratio of the vapor and the distribution ratio of the liquid (water) are equal. It is necessary to make a configuration.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a gas-liquid two-phase system in which the amount of steam and the amount of water can be distributed almost equally when a branch pipe is installed due to the arrangement of connected devices. An object of the present invention is to provide a bleed pipe having a flow branch pipe. [Configuration of the Invention]

[0012]

Means for Solving the Problems The present invention, be those in order to achieve the above object, introducing branches into a vapor containing moisture of the steam turbine and the moisture separator and the feed water heater
Connecting the steam turbine and the moisture separator steam
A bleed air pipe and a bent pipe provided in the middle of the bleed air pipe. This
Branching from the back of this bend just downstream of the bend.
A bent pipe provided with a branch pipe connected to the feed water heater;
A guide vane is provided on the
Characterized in that a straight pipe section 3-4 times the length of the inner diameter of the extraction mother tube on the downstream side of the branch pipe bifurcation.

[0013]

[Action] In the extraction pipe comprising a gas-liquid two-phase flow branch pipe constructed as described above, when the gas-liquid two-phase flow introduced from the steam turbine to pass through the song Ri tube, the liquid film and droplets in the tube Since the liquid film and the droplets are biased to the back side of the bent pipe due to the centrifugal force acting on the pipe, a large amount of water can be separated by the branch pipe provided immediately after the bent pipe, and the moisture content of the entire mother pipe after that is reduced, and Since the bent pipe is provided with the guide vane, the subsequent flow is rectified and uniformly flows into the branch pipe, so that the steam amount and the water amount are substantially equally distributed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an extraction pipe including a gas-liquid two-phase flow branch pipe according to one embodiment of the present invention. As shown in FIG. 1, steam containing moisture from the high-pressure turbine 13 is
5 two to extraction header tube 1 for introducing the incoming account 5, the song Ri pipe 2 on the upstream side of the Y branch pipe 3 fitted with a guide vane 6, as shown in FIG. 3, yet this song Ri tube 2 immediately dorsal direction of the high-pressure feed water heater extraction pipe 24b songs Ri pipe 2 branches to 23b immediately after, i.e. in this case, a structure that branches from the lower portion of the bleed mother tube 1, after the branch, about 3~4D (D is extracted
After arranging a straight bleeding mother pipe 1 of the inner diameter of the pneumatic mother pipe 1 ) , Y
A branch pipe 3 is provided and connected to the deposit account 5 of the moisture separator 15 via the branch pipes 4 of the same length.

In the gas-liquid two-phase flow branch pipe of the steam line containing moisture configured as described above, first, the high-pressure turbine 1
The gas-liquid two-phase flow from 3 flows into the bleeding mother pipe 1, and when a steam flow containing moisture flows in the pipe, an annular spray flow with an increased liquid film is formed. Thus the annular mist flow flows into the song Ri tube 2 liquid film by centrifugal force biased to the back side of the bent pipe 2, taken out from the dorsal extraction
The gas flows into the trachea 24b as a gas-liquid two-phase flow with a large amount of liquid, and enters the high-pressure feed water heater 23b. Therefore this bleed tube 24b
Since the subsequent flow in the bleeding mother pipe 1 becomes a gas-liquid two-phase flow having less moisture than the wet steam on the upstream side of the curved pipe 2, if the moisture decreases as described above, the deviation of the water amount with respect to the distribution of the steam amount also decreases. Less. In addition, since the guide vane 6 is provided in the bent pipe 2, an effect of rectifying the turbulent exhaust flow from the high-pressure turbine 13 is obtained. Since 4D is ensured, the deviation of the flow due to the bent pipe 2 can be minimized.

Furthermore, the structure of the Y branch pipe 3 is symmetrical with respect to the upstream flow direction, and the length of the branch pipe from the Y branch pipe 3 to the inlet account 5 of the moisture separator 15 is the same. , The amount of steam and the amount of water can be distributed to the branch pipes almost equally.

In the bleeding tube including the gas-liquid two-phase flow branching tube of the present embodiment, the liquid film deflected by the curved tube can be discharged by the bleeding tube 24b , so that the moisture on the inlet side of the Y-branch tube 3 can be reduced. Can,
In addition, the deviation of the flow due to the bent pipe can be minimized, and the vapor and gas-liquid can be evenly distributed to the equipment, and the design wetness of each equipment is ensured. Secured. Further, since the liquid is evenly distributed to the branch pipe, the balance of the drain system is kept healthy. Further, since the wetness in each branch pipe after the distribution is made uniform, the wall thickness of the pipe inner wall due to erosion and corrosion is prevented as much as possible.

FIG. 2 is a schematic structural view of another embodiment of the present invention. As shown in the figure, the extraction from this example the back side of the horizontal bent pipe 2 bleed mother tube 1 (the side in this case the extraction mother pipe)
This is a piping layout in which the pipe 24b is taken out, and furthermore, each bent pipe 2 is provided with a guide vane (not shown), and a straight pipe distance of about 3 to 4D is provided upstream of the Y branch pipe 3. I have.

In the bleed tube configured as described above, the gas-liquid two-phase flow is equally distributed as in the above embodiment. The extraction pipe according to this embodiment, since the exhaust branch pipe upstream in the liquid film of the curved pipe in front of the Y branch pipe 3, also shorter straight tube length of Y branch pipe 3 and the upstream side bent pipe, installation of the piping Space can be saved, and the nuclear power plant can be made more compact as a whole.

[0020]

As described above, according to the present invention,
Since discharging the gas-liquid two-phase flow to bias the liquid film of the gas-liquid two-phase flow in the song Ri tube containing a large amount of liquid content in branch following this, subsequent wetness is reduced and moreover guide vanes Curved Pipes And Y
Since a straight pipe distance of about 3 to 4D is provided on the branch pipe inlet side, the flow is rectified. For this reason, the steam amount and the water amount can be evenly distributed to each device, and the design wetness of each device is sufficiently ensured. As a result, the performance of each device is guaranteed,
In addition, a remarkable effect is obtained, such as prevention of wall thickness reduction of the inner wall of the pipe due to erosion and corrosion caused by an increase in wetness due to deviation of the amount of water between the branch pipes.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of another embodiment of the present invention.

FIG. 3 is a sectional view of a bent pipe and a branch pipe according to the present invention.

FIG. 4 (a) is a schematic diagram of a test apparatus for measuring a distribution ratio of a steam amount and a water amount of a conventional gas-liquid two-phase flow branch pipe, and FIG. 4 (b) is a diagram measured by the same figure (a). The graph which shows the relationship between the steam distribution ratio (W _G3 / W _G1 ) and the water distribution ratio (W _L3 / W _L1 ) of the branched pipe after the branch.

FIG. 5 is a system configuration diagram of a conventional nuclear power plant.

FIG. 6 is a schematic view showing an example of use of a gas-liquid two-phase flow branch pipe of a conventional nuclear power plant.

[Explanation of symbols]

1 ... bleed substrate tube, 2 ... song Ri tube, 3 ... Y branch pipe, 4,9 ... branch pipe, 5 ... inlet account, 6 ... guide vanes, 7 ... upstream substrate tube, 8
... downstream mother pipe, 13 ... high pressure turbine, 15 ... moisture separator,
23a, 23b ... high pressure feed water heater, 24a, 24b ... extraction
Trachea .

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01K 7/38 102 F01D 25/00 F16L 41/02 F16L 41/08

Claims (1)

(57) [Claims] 1. A be those introducing branches into the steam turbine of moisture vapor the moisture separator including a feed water heater
Connecting the steam turbine and the moisture separator steam
And bleed mother tube, and a bent pipe which is provided in the middle of the extraction mother tube, this
Branching from the back of this bend just downstream of the bend.
A bent pipe provided with a branch pipe connected to the feed water heater;
A guide vane is provided on the
Extraction pipe, characterized in that a straight pipe section 3-4 times the length of the inner diameter of the extraction mother tube on the downstream side of the branch pipe bifurcation.