JPH0411792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature and pressure reducing device for introducing high-temperature, high-pressure steam into a double water tank in an emergency or the like in a power generation plant.

[Prior art]

FIG. 3 is a system diagram of a power generation facility with a steam bypass system extending from a steam generator such as a boiler and an atomic reactor to a condenser. 1 is a steam generator,
2 is a high pressure turbine, 3 is a low pressure turbine, 5 is a low pressure feed water heater, and 6 is a high pressure feed water heater. The bypass system 8 branches before the high-pressure turbine 2, and the bypass steam passes through the pressure reducing valve 7 and is reduced in temperature and pressure by the temperature reduction and pressure reduction device 4 to a pressure and temperature that can be accepted by the condenser 9, and then converted into condensate. It is discharged into the vessel 9.

Next, FIG. 4 shows the basic configuration of the temperature and pressure reducing device. Steam 13 that entered the temperature reduction/decompression device
is reduced in pressure by the first stage nozzle group 10 and introduced into the expansion space 16. In the expansion space 16 , the temperature of the steam 13 is reduced by the reduced-temperature water 14 jetted from the spray nozzle 12 . The steam 13 whose temperature and pressure have been reduced in this manner is again reduced in pressure by the second stage nozzle group 11 and drained into the condenser 9.

In order to reduce the temperature of the steam sufficiently in such temperature reduction and pressure reduction equipment, it is necessary to mix the steam and detemperatured water efficiently, but since the main flow of steam is extremely high, various methods have not been considered in the past. There is.

For example, as shown in Japanese Unexamined Patent Publication No. 54-150507, there is a method of increasing the pressure of the detemperature water injection part and slowing down the steam flow rate as much as possible.

[Problem that the invention seeks to solve]

However, in many cases, there is a limit to the mixing within the expansion space 16, and a portion of the cooled water flows into the condenser in the form of water droplets. The water droplets that flow into the condenser evaporate when mixed with steam, gradually reducing the diameter of the water droplets. However, when these water droplets collide with the internal structure of the condenser in a range where the diameter of the water droplets is large, erosion occurs. This causes erosion of structures.

In addition, in order to prevent this erosion, if steam is concentrated in a narrow space with no structures inside the condenser, the steam in the effluent will not expand sufficiently, and the final impact surface will become large. The condenser body may also rupture.

Therefore, it is necessary to accurately disperse the bypass steam over a wide area inside the condenser.

An object of the present invention is to provide a temperature and pressure reducing device that does not cause erosion inside the condenser by allowing bypass steam to flow out into a safe space within the condenser.

[Means for solving problems]

First, before devising an embodiment of the present invention, in order to accurately predict the outflow direction of steam through a nozzle hole, the relationship between the inflow angle and the outflow angle of steam with respect to a nozzle was experimentally investigated.

In Fig. 5, nozzle plate thickness t, nozzle hole diameter d
When a nozzle plate 20 is prepared, and the inflow angle with respect to the nozzle central axis 21 is φ ₁ and the outflow angle with respect to the nozzle central axis 21 is φ ₂ , the ratio α between φ ₁ and φ ₂ is as shown in FIG. It can be seen that it is mainly determined by t/d.

That is, when t/d<1 and the plate thickness t is small,
α is close to 1, and is not affected much by the orientation of the nozzle hole 19, and the inflow angle is close to φ ₁ and flows out.

On the other hand, if t/d is large and the plate thickness 17 is thick,
α becomes close to 0, and the water flows out in the direction of the nozzle center axis 21.

Therefore, in order to set the outflow direction to the direction of the nozzle center axis 21, it is necessary that t/d>0.7.

By the way, in the actual structure, the nozzle plate 2
0 weight, thermal stress in the nozzle plate 20, and man-hours for drilling the nozzle holes 19, it is advantageous to make the nozzle plate 20 as thin as possible.
If it exceeds twice the hole diameter d, the effectiveness will be poor.

Therefore, if such practical applicability is taken into consideration, setting the value of t/d to 0.7 to 2.0 is effective in directing the outflowing steam in the direction of the central axis of the nozzle hole.

In fact, in order to confirm such effectiveness, t/
A flow visualization test using the Schilleren method was conducted under the conditions of d=1 and Matsuha number 2.2. the result,
As shown in FIG. 7, the steam flowing out of the nozzle holes 19 is directed along the central axis 21 of each nozzle hole.
It is obvious that it will leak. This indicates that similar results can be obtained even if experiments are conducted with different dimensions of t and d.

Next, we conducted an experiment to investigate the erosion caused by jets containing water droplets. In this experiment, as shown in FIG.
The presence or absence of erosion was evaluated by setting erosion test pieces at each part of the wake as the erosion situation position 26. As a result of this experiment, the distance from the nozzle end face was 2
It was found that if 6L ₀ is 300·d or more, no erosion occurs.

Note that this experiment was conducted under the same pressure and temperature conditions as when bypass steam is introduced into the condenser of an actual machine, so it is highly applicable to the actual machine.

Based on the above findings, we have arrived at the present invention.

That is, the gist of the present invention is that, in a nozzle plate having a nozzle hole diameter d and a nozzle plate thickness t, by setting t/d from 0.7 to 2.0, the outflow direction of steam from the nozzle is approximately in the nozzle axial direction, and the steam By not installing the nozzle in an area within 300 d from the nozzle end face that collides with internal structures after the outflow, and by setting the nozzle hole so that the outflow will flow into the other safe internal space, The objective is to obtain a safe temperature and pressure reduction device that does not cause erosion.

〔Example〕

An embodiment of the temperature reduction and pressure reduction apparatus according to the present invention is shown below.

First, the overall configuration of the embodiment will be described. In FIG. 2, the condenser 9 is composed of an upper body 27, a body 28, and a tube nest 29.
A low-pressure feed water heater 5 is installed in the center, and a temperature reduction and depressurization device 4 is placed approximately midway between the low-pressure feed water heater 5 and the end of the upper body 27.

The temperature and pressure reducing device 4 has a structure as shown in FIG. 4 as a whole, and the present invention is applied to the second stage nozzle group 11.

FIG. 1a shows a sectional view thereof, and in this example, the thickness t of the nozzle plate 20 is set to 5 mm so that it can sufficiently withstand the pressure in the expansion space 16 during operation of the apparatus. On the other hand, as shown in FIG. 1b, the nozzle diameter d of the nozzle plate 20 is related to the range of erosion by a relationship of 300d. Since there is a sufficient distance in the central axis direction 49 of the temperature reduction and decompression device 4 to the condenser upper body 27 on the other side, considering only the center part of the nozzle plate 20, the nozzle hole diameter has It is possible to adopt a diameter that is about 2 to 3 times larger. However, in this example,
The same hole diameter d ₀ is adopted over as wide a range as possible, and is set to 6 mm.

In this case, t/d is 0.83, α in FIG. 6 described above is 0, and it can be said that the steam flows in the direction 21 of the center axis of the nozzle as shown in FIG. 7 after flowing out of the nozzle.

In addition, the range on the nozzle plate 20 with enough distance to prevent erosion of the internal structures such as the upper body wall surface 31 and the external surface 32 of the low-pressure water heater is the range indicated by β33, and this range of β33 is entirely the nozzle hole. The diameter d is within the range of 6 mm.

By the way, the total area of the nozzle holes is the expansion space 1
Since the required flow rate is determined to be able to be processed under the pressure and temperature conditions of 6, the number of nozzles that can be provided within the β range 33 does not have enough total area, so additional nozzles must be installed. Therefore, by further expanding the β range symmetrically, the range γ
46 is also provided with a hole. If the hole diameter is set to 6 mm, the internal structures will be eroded, so measure the distance of the internal structures 31 and 32 from the end surface of the nozzle plate 20 in the normal direction on the curved surface of the nozzle plate 20, and
The value must be less than 1/300. To add the nozzle hole 19, in order to increase the opening area with a small number of nozzles within the range γ46, the hole diameter must be changed for each hole, and in order to simplify the structure, a small diameter hole must be added. Either method can be used, such as opening a large amount of water. In this example,
The latter method is used, and the device 4 and internal structures 31 and 32 are
Since the shortest distance 50 is 1000mm, 3mm
The nozzles 19b and 19c are provided in the entire range γ46.

In this case, t/d is 1.7 and α is -0.14
Although the steam outflow direction in the nozzle hole 19 within the γ46 range is slightly different from the nozzle hole central axis direction 21, there is no structure within the erosion ranges 45b and 45c of 900 mm, and the steam can flow out safely.

The above description has been made focusing on only one horizontal plane based on FIGS. 1a and 1b.

Next, in order to explain considering other horizontal planes,
A developed view of the nozzle plate 20 is shown in FIGS. Here, in FIGS. 9 to 11, the intersections of diagonal lines indicate the drilling positions.

If the nozzle plate 20 is cylindrical and the above-mentioned knowledge is not considered, the arrangement of the nozzle holes 19 on the nozzle plate 20 can be rectangular as shown in FIG. Since the distance to the internal structure cannot be 300d (1800mm), this is the nozzle position that causes erosion. Therefore, by applying the present invention, the arrangement of the 6 mm nozzle holes 19a is as follows.
The result is as shown in FIG.

That is, in the portion A 34 of FIG. 10, as shown in FIG.
Reflecting the fact that it is wider than the original, the arrangement extends toward the bottom. Moreover, since the cross section of the low-pressure feed water heater 5 is circular, the B portion 35 has a shape close to a part of a circle. The arrangement shown in FIG. 10 corresponds to the β range 33 in FIG. The arrangement shown in FIG. 10 can be used if the total area can be taken, but in this example, in addition to the above-mentioned region, a 3 mm An arrangement of nozzle holes 19b and 19c is provided.
The 3 mm nozzle holes 19b and 19c have a small area per nozzle, so a pitch smaller than that of the 6 mm nozzle hole 19a is adopted to increase the number of nozzle holes 19b and 19c.

As described above, by adopting this structure, the upper fuselage 27
The wall surface 31 near the temperature reduction and pressure reduction device 4, the outer surface of the low pressure feed water heater 32, or the heat exchanger tubes 39 of the tube nest 29.
bypass steam can be introduced without causing damage to the Moreover, since the ejection range 40 shown in FIG. 2 can be efficiently distributed throughout the condenser internal space 41,
The steam expands sufficiently, and the collision surface pressure on each part becomes sufficiently small, increasing safety.

Further, since there are only two types of diameters of the nozzle holes 19 and all the nozzle holes are opened in the normal direction of the nozzle plate surface, the machining work is extremely easy.

Next, as a second embodiment, a nozzle hole diameter of 18 is shown in FIG. 12. That is,
In order to configure the nozzle plate 20 using only the β range 33 in FIG. 1, the radius of curvature of the curved surface of the nozzle plate 20 may be increased. Further, if the nozzle plate 20 were made semicircular, there would be a lot of unnecessary parts, so a widening part 51 is provided as shown in FIG. 12. In this case, the range of holes required in the nozzle plate 20 has no effect on the diameter of the expansion space 16, so that the size can be sufficiently reduced at the small diameter end of the diverging portion 51. In addition, with this structure, the nozzle hole diameter is one type, making it easier to manufacture the nozzle plate. Furthermore, although the widening portion 51 is added to the overall structure, the diameter 52 at the position that penetrates the condenser pot body 27 is small due to the main structure, and the connection structure can be simplified. .

Furthermore, in other embodiments, as shown in FIG. 13, the nozzle hole center axis 21 may be tilted toward the nozzle plate 20 surface to obtain the above-described effect.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, (1) erosion does not occur inside the condenser, (2) collision surface pressure on various parts of the condenser body can be reduced, and safe reduction can be achieved. It becomes possible to provide a temperature decompression device.

[Brief explanation of drawings]

Figures 1a and b are block diagrams showing the main parts of the temperature reducing and depressurizing device according to the present invention, Figure 2 is a perspective view of the upper part of the condenser to which the temperature reducing and depressurizing device according to the present invention is applied, and Figure 3 is the main part of the present invention. A power generation plant system diagram to which the temperature reduction and pressure reduction device according to the invention is applied, FIG. 4 is a sectional view showing an example of a conventional temperature and pressure reduction device, and FIGS. 5 to 7 show the nozzle that is the cause of the invention of the present invention. An explanatory diagram of the holes, FIG. 8 is a diagram showing the equipment for erosion testing which is the cause of the invention of the present invention, and FIGS. 9 to 11 are developed diagrams of the nozzle plate applied to the present invention, respectively. FIG. 12 and FIG. 13 are explanatory diagrams showing other embodiments of the temperature and pressure reducing apparatus according to the present invention, respectively. 4...Temperature and pressure reduction device, 5...Low pressure feed water heater,
9... Condenser, 12... Spray nozzle, 16...
... Expansion space, 17 ... Nozzle plate thickness, 18 ... Nozzle hole diameter, 19 ... Nozzle hole, 20 ... Nozzle plate,
21...Nozzle hole center axis, 22...Inflow angle, 2
3...Outflow angle, 27...Condenser upper body, 33
... Large hole diameter nozzle hole arrangement range, 45 ... Range of 300d from the nozzle end face, 46 ... Small hole diameter nozzle hole arrangement range.

Claims (1)

[Scope of Claims] 1. A steam pipe provided in a bypass system from a steam generator to a condenser of a thermal nuclear power plant, through which bypass steam flows, a water injection spray nozzle that opens into the steam pipe, and the steam pipe. A temperature reducing and decompressing device constituted by a nozzle plate having a thickness t and having a large number of nozzle holes provided at the end of the condenser, the nozzle plate having a curved surface convex inside the condenser or a flat surface, When the distance from the position on the nozzle plate to the internal structure of the condenser in the direction of steam outflow after passing through the nozzle hole is L, the thickness t of the nozzle plate and the nozzle hole diameter d are The relationship and the distance L
A temperature reducing and depressurizing device characterized in that t/d=0.7 to 2.0 L=300d. 2 In claim 1, the diameter d of all nozzle holes is set to one value d ₀ in the range of t/d from 0.7 to 2.0, and the distance L from the structure is 300d ₀
A temperature reducing and decompressing device characterized in that nozzle holes are provided only in the above-described range on the nozzle plate, and the direction of the center axis of the nozzle hole is the normal direction of the nozzle plate surface at that position. 3 In claim 2, a range on the nozzle plate where the distance L from the structure is less than 300d ₀ is provided with a diameter d that is less than 1/300 of the dimension L at each position. A temperature and pressure reducing device characterized by: 4 In claim 2, when the nozzle plate is cylindrical and the range of holes on the nozzle plate is projected onto a plane perpendicular to the central axis of the decompression device main body, the part where the spray nozzle opens A temperature and pressure reducing device characterized by having a diameter larger than that of a steam pipe.