JPH01196000A - Steam injector - Google Patents

Abstract

PURPOSE:To increase the pressing force of water and prevent pressure loss due to separation of flow by molding a steam jet nozzle in the form of a diffuser. CONSTITUTION:High pressure water injecting steam injector used for supplying water for a boiler or the like consists of a steam jet nozzle 24 with a needle valve 23, a steam and water mixing nozzle 26 and a pressure increasing diffuser 27. The outlet part of the steam jet nozzle 24 is reamed and the needle 31 of the needle valve 23 is tapered so that the diameter thereof reduces gradually in the lower position. Thus the steam jet nozzle 24 takes the form of a diffuser.

Description

[Detailed description of the invention] [Object of the invention] (Field of application in the FFI industry) The present invention relates to a steam injector for jetting high-pressure water used for boiler water supply, etc., and particularly to a water injection device for an emergency core cooling system such as a light water reactor. This invention relates to a steam injector suitable for.

(Prior Art) Steam injectors are used to supply water to boilers such as steam IigA vehicles, and a structure shown in FIG. 10, for example, is conventionally known.

That is, a steam jetting nozzle 4 with a needle valve 3 is arranged in a casing 2 on the right side of the steam intake port 1, and a water suction port 5 is provided adjacently to the natural air jetting nozzle 4. A steam/water mixing nozzle 6 and a pressure increasing diffuser 7 are disposed downstream of the steam jet nozzle 4 and communicate with a discharge port 9 via a check valve 8. Throat part 10 of steam/water joint nozzle 6
An overflow drain hole 12 communicating with an overflow drain pipe 11 opens therein.

For example, when the needle valve 3 is pulled out from the steam jet nozzle 4 by the handle 13 and the steam supplied from the steam intake port 1 is jetted from the steam jet nozzle 4, the pressure in the water suction port 5 becomes negative pressure due to condensation of the steam. The pressure drops below atmospheric pressure, and water is sucked up from the tank. The steam is condensed by low-temperature water (70° C. or lower) sucked in from the water suction port 5 and flows into the steam/water mixing nozzle 6, where it becomes a high-speed water stream at the throat portion 10. That is, since the enthalpy η0 of steam is higher than the enthalpy η1 of saturated water by the amount of heat of the evaporation layer, this latent heat of vaporization is converted into kinetic energy and forms a high-speed water flow. When this high-speed water flow flows through the pressure increasing diffuser 7, the pressure is increased by the pressure Δp as shown by the following equation according to the law of fluid dynamics.

(ρ: density of water, Ut: flow rate of high-speed water flow passing through the nitrogen throat) As a result, the steam injector can obtain a discharge pressure higher than the supply pressure of steam.

When the pressure on the outlet side of the pressure boosting diffuser 7 becomes sufficiently high, the check valve 8 automatically opens and pressurized water is spouted from the discharge port 9.

However, according to the conventional steam injector described above, a discharge pressure of only 7 KW/cdG can be obtained at most. This is the low pressure used in steam locomotive boilers. The reason why such a limit point occurs is considered to be that the cross-sectional shape of the steam jet nozzle 4 only gradually becomes smaller in diameter toward the tip. That is, with such a nozzle shape, the condensation rate within the steam/water mixing nozzle becomes low, as is clear from fluid dynamics, and therefore a sufficient steam ejection velocity cannot be obtained.

By the way, for example, the reactor pressure in the reactor pressure vessel of a boiling water reactor during an emergency is set as 7089/ciG. It is difficult to apply a conventional steam injector as a water injection device for an emergency core cooling system that spouts cooling water under such high pressure.

Therefore, various studies have been conducted to increase the discharge pressure as a steam injector for a nuclear reactor emergency cooling system, and an example of its configuration is shown in FIG.

This steam injector has roughly the same configuration as the one described above, but the steam injection nozzle 4 has a diffuser shape whose diameter gradually increases, so that a supersonic velocity of the steam flow can be obtained. . Further, a second nozzle 14 is provided next to the steam/water mixing nozzle 6, and an overflow drainage hole 12 is formed on the upstream side of the throat 10.

According to this steam injector, the discharge pressure is approximately 6 times that of the steam injector shown in Fig. 10 (approximately 40!F/
cjG>.

However, even with the steam injector shown in FIG. 11, it is difficult to obtain a discharge pressure of 70/9/dG.

In addition, when water is injected from the core cooling system during an emergency, the pressure inside the reactor pressure vessel decreases for a while and eventually reaches atmospheric pressure, but steam is used to adjust the discharge steam pressure in response to such changes. Injectors are still unknown.

In addition, in the past, the cross-sectional shape of the flow path from the inlet part of the steam/water mixing nozzle to the throat part was made conical, and the overflow drainage hole was formed along the entire circumferential direction of the throat part. The pressure loss caused by the peeling off was relatively large, and this was also a factor in the reduction in pressurizing pressure.

(Problems to be Solved by the Invention) In conventional steam injectors, the discharge pressure is relatively low (limited), making it difficult to apply them to emergency core cooling of nuclear reactors.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a steam injector capable of injecting discharge water at a sufficiently high pressure to be applicable as a water injection device for an emergency core cooling system of a nuclear reactor.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a steam jet nozzle with a needle valve in a casing having a steam intake port, and a water suction port is provided adjacently to the steam jet nozzle. In the steam injector for high-pressure water jetting, which has a steam/water mixing nozzle and a pressure boosting diffuser on the downstream side,
The exit part of the steam jet nozzle is expanded in diameter toward the downstream side, and the needle of the needle valve is tapered to have a smaller diameter toward the downstream side of the steam jet nozzle, thereby making the steam jet nozzle into a diffuser shape. It is characterized by the following.

Preferably, the cross-sectional shape of the flow path from the inlet of the steam/water mixing nozzle to a part of the stream 0-1 is a quarter ellipse.

Further, a cross-sectional area variable means for varying the flow passage cross-sectional area of the steam/water mixing nozzle was provided.

The cross-sectional area variable means is preferably a needle inserted from the downstream side of the diffuser so as to be movable back and forth in the axial direction of the flow path.

Further, the needle is desirably driven by a control device that sets the amount of advance and retreat in accordance with the supplied steam pressure.

Furthermore, overflow drainage holes in the form of slits long in the axial direction are provided at intervals in the circumferential direction in the throat portion of the steam/water mixing nozzle.

Furthermore, the steam jetting nozzle is annular, and the water suction port is arranged at the axial center.

Note that the steam injector of the present invention preferably connects the water inlet to the emergency cooling system piping of the nuclear reactor, and connects the pressurized water discharge part to the spray nozzle in the reactor so as to connect the water inlet to the emergency core cooling system of the nuclear reactor. Apply as a purpose.

(Function) By making the steam jet nozzle into a diffuser shape,
Since a supersonic flow of steam is formed, the enthalpy of the steam is effectively converted into kinetic energy, and the pressurizing force of water is significantly increased compared to conventional methods. Moreover, the steam jet function and steam flowffi:l! Since the valve throttling function for J adjustment is performed at the same location, unlike conventional models, problems such as the steam pressure already decreasing on the upstream side of the steam jet nozzle and the steam flow rate not increasing sufficiently occur. do not have.

In addition, if the cross-sectional shape of the flow path from the inlet to the throat of the steam/water mixing nozzle is made into a quarter-ellipse, unlike the conical steam/water mixing nozzle used in conventional steam injectors, pressure loss due to flow separation can be avoided. can be prevented and high-speed water flow can be obtained efficiently.

In addition, when a cross-sectional area variable means is installed to vary the flow passage cross-sectional area of the steam/water mixing nozzle, when the steam supply pressure is high, the flow passage cross-sectional area is reduced and the water flow rate at the throat portion is increased. By doing so, Δp in equation (1) can be increased. On the other hand, when the steam supply pressure is low, the discharge pressure may also be low, so Δp can be made small. Thereby, the discharge water pressure can be arbitrarily set according to the required pressure. Note that if the cross-sectional area variable means is a needle inserted so as to be movable in the axial direction of the flow path, the configuration is simple and the cross-sectional area adjustment function is reliable.

Note that if the needle is driven by a control device that sets the amount of advance and retreat in accordance with the supplied steam pressure, automatic operation becomes possible.

Furthermore, by providing slit-shaped overflow drainage holes along the axial direction at intervals in the circumferential direction in the throat section of the steam/water mixing nozzle, it is possible to reduce the number of locations where flow separation occurs in the circumferential direction. Become.

Furthermore, when the steam jetting nozzle is annular and the water suction port is arranged at the axial center, the steam jetted from around the nozzle sucks in water from the center, making the flow of steam extremely efficient. And it can be done smoothly.

In addition, when the steam injector of the present invention is applied to the emergency core cooling system of a nuclear reactor, it becomes possible to cope with high pressure during an emergency of the nuclear reactor, and also to reduce pressure fluctuations in the reactor due to cooling. Pressurized water discharge can be adjusted accordingly.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

1 to 6 show a first embodiment.

As shown in FIGS. 1 and 2, a steam jet nozzle 24 with a needle valve 23 is provided in the casing 22 on the right side of the steam intake port 21. A water suction port 25 is provided adjacently to this steam jet nozzle 24, and a steam/water mixing nozzle 2 is installed downstream of the water suction port 25.
6 and a pressure increasing diffuser 27, a discharge port 28 is provided.

An overflow drainage hole 30 opens into the throat portion 29 of the steam/water mixing nozzle 26 .

The diameter of the outlet of the steam jet nozzle 24 increases toward the downstream side, and the needle 31 of the needle valve 23 tapers to a smaller diameter toward the downstream side of the steam jet nozzle 24, thereby turning the steam jet nozzle 24 into a diffuser. It has a shape. Note that 33 is a handle for driving the needle 31 forward and backward in the nozzle axial direction.

Then, when steam is supplied into the casing from the steam intake port 21 and the needle 31 is pulled out from the steam jet nozzle 24 by the handle 32, steam is jetted from the steam jet nozzle 24, and low-temperature water is sucked from the water suction port 25. (
70'CJX lower), the steam flows into the steam/water mixing nozzle 26 while being condensed, and becomes a high-speed water flow at the throat 29 section.

In this case, by making the steam jet nozzle 24 into a diffuser shape, a supersonic flow of steam is formed, as has been clarified from hydrodynamics, so that the enthalpy of the steam is effectively converted into kinetic energy. This increases the condensation rate within the steam/water mixing nozzle 26 compared to conventional ones, making it possible to obtain a discharge pressure of 70 kg/d0 or more.

Moreover, since the steam jetting function and the valve throttling function for adjusting the steam flow fa are performed at the same location, the steam pressure already drops on the upstream side of the steam jetting nozzle, making it impossible to increase the steam flow rate sufficiently. There are also more than one problem.

Further, as shown in FIG. 3(a), the cross-sectional shape of the flow path from the inlet portion 26a of the steam/water mixing nozzle 26 to the throat 29 portion is made into a quarter-ellipse shape.

As a result, the flow path has an extremely smooth constricted cross-sectional shape, which is similar to a steam/water mixing nozzle in which tapered and cylindrical cross sections are connected through corners, as in the conventional steam injector shown in Figure 3(b). Unlike this, pressure loss due to flow separation can be prevented, and high-speed water flow can be obtained efficiently.

Further, as shown in FIGS. 4 and 5, the steam/water mixing nozzle 26 is provided with a cross-sectional area variable means 35 for varying the cross-sectional area of the flow path. This cross-sectional area variable means 35 has a tapered needle 36 inserted so as to be movable in the axial direction of the flow path from the downstream side of the pressure-boosting diffuser 27, and a handle 37 for operating the needle 36. A gear 39 is formed on the outer peripheral surface of the handle 37 so that it can be rotated by a geared motor 40. The guard motor 40 is controlled by a control device 41. The control device 41 determines a suitable nozzle opening degree corresponding to the supplied steam pressure, that is, 3! of the needle 37! The flow rate detector 42 is connected to the steam intake port 21, an amplifier 43 that amplifies the detected signal, a motor controller 44, etc.

When the steam pressure supplied to the steam intake port 21 is high, the needle 37 is inserted deeply into the throat 29 to reduce the flow passage cross section of the throat 29 by 8% A Δp in equation (1) is increased by increasing Δp. on the other hand,
When the steam supply pressure is low, the discharge pressure may also be low, so the needle 37 is pulled out from the throat 29 portion in the direction of the flow path cross section of the throat 29! By increasing aA and decreasing the flow rate of water at the throat 29 portion, Δp in equation (1) is made smaller. Thereby, even if the steam supply pressure is low and the water flow velocity U is small, the necessary water flow ωW1 is ensured.

Note that the flow mw is calculated by the following formula.

Wl−ρ,・A1・U■ ・・・・・・・・・(2)
Therefore, according to the steam injector of this embodiment, it is possible to operate in a wide range of steam supply pressures, and the reliability and performance can be greatly improved.Moreover, the needle can be set to advance or retreat in accordance with the supply steam pressure. Since it is driven by a control device, automatic operation is possible.
And the structure is also in the middle of the day.

Furthermore, by providing slit-shaped overflow drainage holes 30 along the axial direction at intervals in the circumferential direction in the throat portion of the steam/water mixing nozzle 26, the number of locations where flow separation occurs can be reduced in the circumferential direction. It becomes possible. Figure 6 (a
), (b) is the flow! The state of IJIII is schematically shown for this actual example and a conventional example, respectively.

As shown in Figure 6(b), in the case of conventional steam injectors, a slit-shaped overflow drainage hole along the circumferential direction is formed in the middle of the throat to take out overflow water, so that the entire inner surface of the throat is Separation of flow W4a occurred over the course of the flow, resulting in a large pressure loss.

On the other hand, in the case of this embodiment, as shown in FIG. 6(a), a plurality of slit-shaped overflow drainage holes 30 along the axial direction are provided at intervals in the circumferential direction in the middle of the throw. Because of this, even if the slit has the same area, flow separation @a' occurs only partially, resulting in very little pressure loss.

In this embodiment, the cross-sectional shape of the boosting diffuser is a partial ellipse or a partial arc having a predetermined radius R, with the inner surface of the throat close to the inner surface of the throat.

The shape of the pressurizing diffuser is shown on the right side of each of FIGS. 3(a) and 3(b). In this embodiment ((a) in the same figure), there are no steps or corners at the connection part with the wrist throat, which is different from the conventional one (circulation (b)), which prevents pressure loss due to separation vortices of the flow, and allows high-speed water flow. can efficiently convert dynamic pressure into hydrostatic pressure.

Next, another embodiment of the present invention will be described with reference to FIGS. 7 and 8.

In this embodiment, the steam jet nozzle 24 is annular, and the water suction port 25 is arranged at the axial center of the nozzle. That is, in this embodiment, the needle 31 of the steam jet nozzle 24 of the previous embodiment has a larger diameter, the outer peripheral side of the needle 31 is the steam jet nozzle 24, and the water suction port 25 is located inside the needle 31 It has a structure with holes.

Low-temperature water is supplied from the rear of the steam injector, and steam is injected in an annular direction toward the center of the nozzle. That is, the steam ejection nozzle 24 has an inner wall in a cylindrical shape parallel to the nozzle axis, and an outer wall in a shape with a smooth convex curved surface that is axially symmetrical.

This outer wall and the inner surface of the casing that constitutes the steam jet nozzle are also shaped to have smooth convex curved surfaces that are axially symmetrical, thereby expanding and contracting the steam flow path area and forming an annular diffuser-shaped nozzle. . This diffuser function easily makes the steam supersonic, so the enthalpy of the steam is effectively converted into kinetic energy.

According to this configuration, since the water injection direction and the nozzle axis are aligned in the same direction, there is little loss of pressure In.
The steam is also annular and ejected toward the negative point, which improves the efficiency of the condensation action.

Note that the other configurations are the same as those of the steam injector of the previous embodiment, so corresponding parts in the figures are denoted by the same reference numerals, and the explanation thereof will be omitted.

FIG. 9 shows a plant structure in which the steam injector of the present invention is applied to an emergency cooling system of a next-generation nuclear reactor where safety is particularly important.

That is, it was placed inside the reactor pressure vessel 45. A discharge port of a steam injector 48 is connected to the head spray 46 via an auxiliary water supply pipe 47, and a water suction port of the steam injector 48 is connected to a condensate storage tank 50k1. It is connected. Steam is introduced from the reactor pressure vessel 45 into the air intake port of the steam injector 48 via a steam introduction pipe 51.

Note that 52 indicates a turbine, and 53 indicates a turbine-generated IFi machine.

In the unlikely event that an accident occurs and the reactor is isolated and the main water supply is stopped, steam is supplied to the steam injector 48, the steam injector is activated, and condensate is supplied to the head spray 46. , used as an auxiliary water supply system or an emergency core cooling system. As time passes, the steam pressure in the reactor pressure vessel 45 decreases,
When the steam injector 48 according to the present invention is used, the pressurized water discharge pressure is changed according to the decrease in the steam pressure in the furnace, and efficient operation can be performed. In addition, it is a static fluid pump that does not require a large-capacity power source like a diesel generator, unlike the commonly used centrifugal pump, and has extremely high reliability in the event of a nuclear reactor accident, improving safety. This will greatly contribute to the

It goes without saying that the steam injector of the present invention is not limited to use in nuclear reactors, but can be widely applied as a device for supplying pressurized water such as water injection to various other boilers.

According to each of the embodiments described above, it is possible to provide a steam injector that can inject extremely high-pressure pressurized water and can adjust the pressure of the discharged water, and the following various effects can be achieved.

By making the steam ejection nozzle 24 into a diffuser shape, a supersonic flow of steam is formed, and the pressurizing force of water is significantly increased compared to the conventional one.

Moreover, since the steam jetting function and the valve throttling function for adjusting the steam flow Im are performed at the same location, problems such as insufficient steam flow velocity on the upstream side of the steam jetting nozzle 24 do not occur.

Further, by making the cross-sectional shape of the flow path from the inlet of the steam/water mixing nozzle 26 to the throat portion 29 into a quarter-ellipse shape, pressure loss due to flow separation can be prevented, and a high-speed water flow can be efficiently obtained.

Further, by providing a cross-sectional area variable means 35 for varying the flow path cross-sectional area of the steam/water mixing nozzle 26, the discharge water pressure can be arbitrarily set according to the required pressure. In addition,
When the cross-sectional area varying means 35 is a needle 36 inserted so as to be movable in the axial direction of the flow path, the configuration is simple and the cross-sectional area: 11 adjustment function is reliable.

f. If the needle 36 is driven by a control device 41 that sets the amount of advance and retreat in accordance with the supplied steam pressure, automatic operation becomes possible.

Furthermore, by providing slit-shaped overflow drainage holes 30 along the axial direction in the throat portion 29 of the steam/water mixing nozzle 26 at intervals of r8 in the circumferential direction, the number of locations where flow separation occurs is reduced in the circumferential direction. becomes possible.

Furthermore, when the steam jet nozzle 24 is annular and the water suction port 25 is arranged at the axial center, the steam jetted from around the nozzle sucks in water from the center, making the flow of steam extremely efficient. Can be done well and smoothly.

In addition, when the steam injector of the present invention is applied to the emergency core cooling system of a nuclear reactor, it becomes possible to cope with high pressure during an emergency of the nuclear reactor, and also to reduce pressure fluctuations in the reactor due to cooling. Pressurized water discharge can be adjusted accordingly.

〔Effect of the invention〕

According to the present invention, by making the steam ejection nozzle into a diffuser shape, a supersonic flow of steam is formed, and the pressurizing force of water is significantly increased compared to the conventional one.

Moreover, since the steam jetting function and the valve throttling function for adjusting the steam flow rate are performed at the same location, problems such as insufficient steam flow velocity on the upstream side of the steam jetting nozzle do not occur.

When the steam injector of the present invention is applied to an emergency core cooling system of a nuclear reactor, it becomes possible to cope with high pressure during an emergency of a nuclear reactor.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the steam injector according to the present invention, Fig. 2 is an enlarged view showing the steam ejection nozzle section of Fig. 1, and Figs. An enlarged explanatory diagram showing the shape of the water mixing nozzle part in comparison with a conventional example,
FIG. 4 is a sectional view showing the structure of the cross-sectional area variable means of the steam/water mixing nozzle, and FIG. 5 is a configuration diagram showing the tIII11 device.
6(a) and 6(b) are explanatory diagrams showing the function of the overflow drainage hole in comparison with a conventional example, FIG. 7 is a sectional view showing another embodiment of the present invention, and FIG. 8 is a diagram similar to that of FIG. FIG. 9 is a configuration diagram showing an example of application to nuclear reactor equipment, FIG. 10 is a sectional view showing a conventional example, and FIG. 11 is a sectional view showing another conventional example. be. 21...Steam intake, 2...Casing, 23...
・Needle valve, 24... Steam jet nozzle, 25...
Water suction port, 26...Steam/water mixing nozzle, 27...
Pressure boosting diffuser, 28...Discharge port, 29...Throat portion, 30...Overflow drainage hole, 31...
- Needle, 32... Handle, 35... Cross-sectional area variable means. Applicant's agent Hisashi Hatano Figure 2 Figure 5 S Figure 8 Figure 1O Figure 14, 11

Claims (1)

[Claims] A steam jet nozzle with a needle valve is installed in a casing with a steam intake port, a water suction port is installed adjacent to the steam jet nozzle, and a steam/water mixing nozzle and a pressure boosting diffuser are installed downstream of the steam jet nozzle for high-pressure water jetting. In the steam injector, the outlet portion of the steam jetting nozzle is expanded in diameter toward the downstream side, and the needle of the needle valve is tapered to have a smaller diameter toward the downstream side of the steam jetting nozzle, so that the steam can be jetted out. A steam injector characterized by a diffuser-shaped nozzle.