JP4801882B2 - Jet pump - Google Patents

Description

  The present invention relates to a jet pump used for circulating coolant in a boiling water reactor, and more particularly to a jet pump that can improve pump efficiency and reduce driving power of a recirculation pump.

  In a boiling water reactor (hereinafter referred to as BWR), the coolant in the reactor pressure vessel is circulated through a jet pump. The jet pump is installed in the downcomer section of the reactor pressure vessel, and the primary coolant in the reactor pressure vessel is forcedly circulated to the core via the jet pump by the recirculation pump of the reactor recirculation system, and the heat generated in the core Is supposed to be taken out.

  The jet pump 1 is configured as shown in FIG. 8, and a high-pressure (total pressure) driving fluid is ejected from the nozzle tip (nozzle port) 2 a of the driving nozzle 2 to the bell mouth 3 at a high speed. Accordingly, the driven fluid (primary cooling material) around the bell mouth 3 is sucked into the bell mouth 3 and is guided to the throat 4 together with the driving fluid.

  The throat 4 is a straight pipe having a circular cross section and constitutes a mixing tube portion. The throat 4 mixes the driving fluid and the driven fluid. The fluid mixed in the throat 4 passes through the diffuser 5 and is sent from the tail pipe 6 to the lower core plenum. While the mixed fluid passes through the diffuser 5, the kinetic energy is converted into pressure energy and discharged from the tail pipe 6 to the lower plenum of the core at a pressure higher than the pressure of the driven fluid (primary coolant) before suction.

  As shown in FIG. 8, the pressure (total pressure) of the fluid is P, the flow rate is Q, the suffixes n, s, and d are the nozzle flow (driving flow), the suction flow (driven flow), and the diffuser flow (discharge flow). As shown, the pump performance of the jet pump 1 can be expressed by a flow rate ratio (hereinafter referred to as M ratio) and a pressure ratio (hereinafter referred to as N ratio).

[Equation 1]
Flow ratio: M ratio = Qs / Qn
Pressure ratio: N ratio = (Pd−Ps) / (Pn−Pd)
Jet pump efficiency η: η = M ratio, N ratio, 100 (%)
In the existing BWR, the jet pump 1 having an M ratio of about 1.2 and a jet pump maximum efficiency of about 35% is used. For this reason, about 1/2 of the flow rate required for circulating the coolant in the reactor pressure vessel flows as a driving fluid for the jet pump 1 in the reactor recirculation system 25 outside the reactor pressure vessel.

  As for the drive nozzle 2, in addition to the one having a single nozzle port 2a, a jet pump 1A having five nozzle ports 7a for the drive nozzle 7 as shown in FIGS. 9A and 9B is also known. (Patent Document 1). The five nozzle ports 7a are circular in any cross section.

This is a jet pump that can increase the M ratio and reduce the flow rate of the reactor recirculation system. As shown in FIG. 10, the jet pump has a single nozzle port 2a and increases the M ratio to about 2 or more. Compared to the above, the jet pump efficiency η is improved. Thus, conventionally, it has been considered that the jet pump efficiency η is improved by using five nozzles.
JP-A 49-1000060

  In the existing BWR, for example, 16 or 20 jet pumps 1 (1A) are provided in the downcomer portion in the reactor pressure vessel.

  However, since the pump efficiency of the jet pump 1 is relatively low, the ratio of the driving power of the recirculation pump necessary for circulating the primary coolant of the BWR to the power generation amount of the nuclear power plant is about 1-1. It corresponds to 5% and is very large.

  In the existing BWR, it is known that if the pump efficiency of the jet pump 1 is improved, the driving power of the recirculation pump is reduced, and the operating cost of the nuclear power plant can be greatly reduced. large.

  Conversely, the improvement in pump efficiency of the jet pump 1 can increase the achievable coolant circulation flow rate at the maximum driving power of the recirculation pump. In the future, if it becomes necessary to increase the coolant circulation flow rate due to changes in the BWR core, etc., it is possible to respond immediately.

  It should be noted that the existing BWR using the jet pump 1 may be replaced with a relatively efficient jet pump 1A, but the overall shape of the jet pump is different from each other. The place welded and joined inside the container is required, and a great deal of work such as cutting and welding is required, and the work is not easy. Moreover, it is necessary to combine with a nuclear reactor recirculation pump that matches the M ratio (about 2.2) of the jet pump 1A, which requires a large amount of work and cost.

  The present invention has been made in consideration of the above-described circumstances, and does not require a large amount of work and cost for cutting work, welding work, and replacement of the reactor recirculation pump, and is economical and achievable for a nuclear power plant. An object of the present invention is to provide a jet pump for improving the coolant circulation flow rate.

  With this configuration, the jet pump increases the flow area of the driven fluid and decreases the fluid velocity, thereby forming a region where the fluid is separated from the inner peripheral surface of the throat straight pipe portion on the upper end side of the throat. The thickness can be reduced, and the thickness (the inner height in the radial direction) separating from the wall surface of the peeling region can be reduced accordingly. In this jet pump, the diameter of the interface shape of the flow with high flow rate and the flow with low flow rate can be increased in the throat straight pipe part, and no large constriction phenomenon occurs at the interface, so the pressure loss of the throat is reduced. I get out.

  In addition, the drive nozzle has one nozzle port, and the throat includes a tapered tube portion having an expansion angle smaller than that of the diffuser at least on the downstream side thereof, while maintaining the mixing function of the driving fluid and the driven fluid, Since pressure loss can be reduced, the pump efficiency of the jet pump can be improved.

In order to solve the above-described problem, a jet pump according to the present invention is entrained by a drive nozzle that ejects a drive fluid from a nozzle port and a drive fluid that is ejected from the drive nozzle as described in claim 1. A peripheral mouth driven fluid, a throat that mixes the driving fluid and the driven fluid from the bell mouth, and a diffuser that is connected to the downstream side of the throat and discharges the mixed fluid. The drive nozzle is provided with a plurality of nozzle legs branched at the nozzle tip in the circumferential direction, and each nozzle leg is radially arranged with a flat cross-sectional outer shape being a streamline or a bullet shape. Is.

In order to solve the above-described problem, according to a jet pump according to the present invention, as described in claim 2, the bell mouth includes an inflow port facing the nozzle port of the drive nozzle, The external shape of the bell mouth in plan view, which is substantially orthogonal to the flow direction of the driving fluid, is formed into a petal shape.

  Since the jet pump according to the present invention can improve the pump efficiency, the driving power of the external pump can be reduced, and even if this driving power is reduced, the coolant circulation flow rate can be sufficiently secured, and the nuclear power generation The operating cost of the plant can be reduced and the economy can be improved.

  Further, the replacement can be carried out in a simplified manner and in a short time without requiring a large amount of work and costs such as cutting work, welding work, and replacement of the reactor recirculation pump.

  Furthermore, the jet pump according to the present invention is suitable for improving the efficiency of the jet pump of an existing nuclear power plant having a relatively small flow rate ratio of about 1.2 and reducing the driving power of the external pump.

  An embodiment of a jet pump according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a longitudinal sectional view showing a boiling water reactor (BWR) 10 equipped with a jet pump according to the present invention, and FIG. 2 is a perspective view of a jet pump assembly 12 provided in a downcomer portion 11 of the BWR 10. Is.

  In the BWR 10, a reactor core 15 is provided in a reactor pressure vessel 13, and a sleeve-like or annular downcomer portion 11 is formed between the reactor core shroud 16 surrounding the reactor core 15 and the reactor pressure vessel 13. A plurality of, for example, 10 or 8 jet pump assemblies 12 are provided in the downcomer portion 11, and the primary coolant in the reactor pressure vessel 13 is transferred from the lower core plenum 17 into the core 15 by the jet pump assembly 12. Forced circulation.

  A shroud head 20 that covers the core upper plenum 18 is provided above the core 15, and a steam / water separator 21 is provided above the shroud head 20 via a stand pipe 22. A steam dryer 23 is provided above the steam separator 21, and the steam separated by the steam separator 21 is dried, and this steam is supplied as main steam to a steam turbine (not shown) through the main steam system. The steam turbine is driven.

  On the other hand, two reactor recirculation systems 25 are provided outside the reactor pressure vessel 13. The reactor recirculation system 25 is an external pump for the primary coolant in the reactor pressure vessel 13. The reactor recirculation pump 26 forcibly circulates to the core 15 via the jet pump 27 and takes out the heat generated in the core 15. The reactor recirculation system 25 controls the pump heat output (amount of generated steam) by controlling the pump speed of the reactor recirculation pump 26 to change the coolant supply flow rate to the core 15.

  A plurality of, for example, 16 or 20 jet pumps 27 are disposed in the downcomer portion 11 in the reactor pressure vessel 13. By disposing a plurality of jet pumps 27 along the circumferential direction outside the core 15, the coolant in the reactor pressure vessel 13 is forcibly circulated.

  The driving fluid of the jet pump 27 is a discharge flow of the recirculation pump 26 as an external pump. This driving fluid is guided to the reactor recirculation pump 26 through the suction pipe 28 from the downcomer portion 11 below the reactor pressure vessel 13 and is pressurized. The driving fluid whose pressure has been increased by the reactor recirculation pump 26 passes through the discharge pipe 29 and is branched into a plurality of header pipes 30, and is guided to each jet pump assembly 12.

  As shown in FIG. 2, the jet pump assembly 12 provided in the BWR 10 includes a riser pipe 32 that rises the downcomer portion 11 from the recirculation inlet nozzle 31, a 180-degree bend 33 provided on the top of the riser pipe 32, The jet pump 27 is connected via a bend 33. In the BWR 10, the jet pump 27 is connected to the riser pipe 32 through a 180-degree vent 33. The 180-degree vent 33 branches the drive fluid that moves up the riser pipe 32 to the left and right sides and guides it to the drive nozzle 35.

  On the other hand, the jet pump 27 includes a drive nozzle 35 connected to the 180-degree vent 33, a bell mouth 36 that guides a driven fluid entrained by the drive fluid ejected from the drive nozzle 35, A throat 37 for mixing the driving fluid and the driven fluid, a diffuser 38 connected to the downstream side of the throat 37, and a tail pipe 39 provided at the lower end of the diffuser 38 are provided.

  The inlet portion of the 180-degree vent 33 of the jet pump assembly 12 and the diffuser 38 are provided with mechanical fitting portions 40, 41. The fitting portions 40, 41 provide the 180-degree vent 33, the drive nozzle 35, the throat 37, and the diffuser. A part of 38 can be removed.

  On the other hand, the mechanical fitting portion 41 to the tail pipe 39 of the diffuser 38 are joined and fixed to the reactor pressure vessel 13 by welding.

  In the jet pump 27 shown in FIG. 3A, when the drive nozzle 35 has one nozzle port 35a, the drive nozzle 35 causes the drive fluid to be ejected from the nozzle port 35a to the bell mouth 36. The driven fluid (primary coolant) is wound around the bell mouth 36 and sucked, and is guided to the throat 37 which is a sleeve-like member together with the driving fluid. The bell mouth 36 is joined to the top of the throat 37, while the throat 37 is detachably joined to the top of the diffuser 38.

  The throat 37 has an upstream mixing tube portion 44 and a downstream tapered tube portion 45 which are straight pipe portions, and the fluid guided to the throat 37 causes a driving fluid and a driven fluid to be separated by the mixing tube portion 44. An initial acceleration force is applied to the driven fluid while mixing. The mixing tube portion 44 has an axial length effective for applying the initial acceleration force necessary for the driven fluid while maintaining the fluid mixing mechanism, and the shaft of the mixing tube portion 44 which is the straight tube portion. The length in the direction is about several to ten times the throat diameter, preferably about 5 times or less and about 3 times. By making the axial direction length of the mixing pipe part (straight pipe part) 44 about several times, it can be made shorter than a conventional jet pump having a mixing pipe part about 10 to 12 times the throat diameter.

  On the downstream side of the straight pipe portion 44 of the throat 37, there is a tapered pipe portion 45 that reduces the pressure loss of the fluid. The taper tube portion 45 expands in a taper shape downward, but the expansion angle θt is set to be several degrees or less, which is significantly smaller than the expansion angle θd of the diffuser 38. The spread angle θd of the diffuser 38 is about 7 to 8 degrees, but the spread angle θt of the tapered tube portion 45 is formed to be, for example, 2 degrees or less, preferably about 1 degree.

  The jet pump 27 is configured such that the upstream side of the throat 37 is a straight pipe part (mixing pipe part) 44 and the downstream side of the throat is a tapered pipe part 45 having a slight expansion angle θt. The average flow velocity of the mixed fluid of the driving fluid and the driven fluid is gradually decreased in the flow direction. Since the pressure loss of the mixed fluid is proportional to the square of the average flow velocity, the pressure loss of the mixed fluid can be greatly reduced to about a fraction, and the pump efficiency of the jet pump 27 can be improved.

  Further, the total axial length of the jet pump 27 shown in FIG. 3A is manufactured to the same dimension as the total axial length of the conventional jet pump, so that the mechanical fit of the existing jet pump is achieved. The 180-degree vent 33, the drive nozzle 35, the throat 37, and a part of the diffuser 38 can be removed and replaced with a new jet pump 27. The replacement work of the jet pump 27 does not require a large amount of work such as a cutting work or a welding work, and can be simplified and performed in a short time.

  In FIG. 2, reference numeral 46 denotes a plate-like support member. The drive nozzle 35 and the bell mouth 36 are joined and integrated by the support member 46.

  According to this jet pump 27, the pressure loss can be greatly reduced by the tapered tubular portion 45 of the throat 37 while maintaining the function as a mixing chamber for mixing the driving fluid and the driven fluid by the throat 37. The pump efficiency of the jet pump 27 can be increased. By improving the pump efficiency of the jet pump 27, the coolant flow rate taken out to the reactor recirculation system 25 can be reduced, and the pump driving power of the reactor recirculation pump 26 can be reduced.

  In addition, as shown in FIG. 3B, the drive nozzle 35 has a nozzle opening 35a spaced upward from the bell mouth 36, and by reducing the length of the drive nozzle 35 in the nozzle axis direction. A space H is formed between the nozzle tip 48 on the downstream side of the nozzle body 47 and the bell mouth 36. This interval H does not include zero on the center axis CL of the jet pump, and is set from a range up to about ½ of the nozzle diameter of the drive nozzle 35. Preferably, an interval H of about 1/10 of the nozzle diameter is selected.

  In the jet pump 27 shown in this embodiment, the nozzle port 35a of the drive nozzle 35 is separated from the inlet surface of the bell mouth 36 by a distance H, for example, about 1/10 of the nozzle diameter, so that the flow path of the driven fluid Increases and the speed of the driven fluid can be reduced.

  By increasing the flow area of the driven fluid and decreasing the fluid velocity, the area A where the fluid separates from the inner peripheral surface of the throat straight pipe portion 44 on the upper end side of the throat 37 can be reduced. Therefore, the thickness (inward radial height) W that is separated from the wall surface of the peeling region A can be reduced.

  In this jet pump 27, the diameter of the interface shape of the flow having a high flow rate and the flow having a low flow rate can be increased in the throat straight pipe portion 44, and a large necking phenomenon does not occur at the interface. The pump efficiency of the jet pump 27 can be improved.

As shown in FIG. 10, in the conventional jet pump, it was thought that the jet pump efficiency η was improved by increasing the number of nozzles to five nozzles. However, like the jet pump 1, the M ratio is as low as about 1.2. As for the jet pump, as shown in FIG. 4, when the number of existing nozzle ports is five nozzle ports of the jet pump 1 rather than one jet pump, and the nozzle port of the jet pump 27 in the first embodiment. Experiments have revealed that the pump efficiency η is reduced in any of the cases where the number is five. The jet pump 27 according to the present invention prevents and improves the decrease in pump efficiency η. Even when the jet pump 27 has one nozzle port, it was confirmed by experiments that the pump efficiency η is improved in the region where the M ratio is low by adjusting the distance between the nozzle port and the bell mouth.
In the case of the jet pump 27 of the first embodiment having five nozzle ports, the pump efficiency is improved as compared with the case of five nozzle ports of the conventional jet pump, but it is effective as a jet pump. This is only a comparative example showing the properties, and a jet pump having five nozzle ports is not used in a region where the flow rate ratio (M ratio) is low.

[Second Embodiment]
FIGS. 5A and 5B show a jet pump according to a second embodiment of the present invention.

  In the jet pump 27A shown in this embodiment, the nozzle tip shape of the drive nozzle 50 is different from the nozzle tip shape of the drive nozzle 35 shown in the first embodiment. Other configurations and operations are not substantially different from those of the jet pump 27 shown in the first embodiment, and thus redundant description is omitted.

  In the jet pump 27A shown in the second embodiment, the nozzle tip 51 of the drive nozzle 50 is configured in a tapered shape that tapers from the nozzle body 52 toward the nozzle port 53, while the nozzle port 53 and its periphery are The cross-sectional shape orthogonal to the flow direction of the driving fluid is formed into a petal shape or a spline shape.

  The nozzle tip 51 of the drive nozzle 50 is formed into a plurality of, for example, five petals, with the tapered side of the nozzle taper portion 54 narrowed down and undulated in the circumferential direction. The concave portion 55 formed in the tapered outer peripheral portion of the nozzle taper portion 54 is drawn so that the depth of the curved groove gradually increases in the axial direction toward the nozzle port 53.

  The shape of the nozzle tip 51 of the drive nozzle 50 is drawn into a shape of five petals toward the nozzle tip of the nozzle taper 54, so that the drive fluid jetted from the nozzle port 53 and the jet flow of this drive fluid Therefore, it is possible to increase the contact area of the driven fluid that is involved, and the mixing of the driving fluid and the driven fluid is promoted, so that the pump efficiency of the jet pump 27A can be significantly increased.

  In the second embodiment, an example in which the shape of the nozzle tip portion is different from that of the jet pump 27 of the first embodiment is shown. However, in the existing jet pump 1 as well, only the drive nozzle may have the shape shown in FIG. Good.

  Even in this case, the jet pump 27A shown in FIG. 5 removes the 180-degree vent 33, the drive nozzle 35, the throat 37, and a part of the diffuser 38 at the mechanical fitting portion of the existing jet pump 1, It can be replaced with a new jet pump 27, and the pump efficiency η can be improved while maintaining the same flow ratio M, so that the replacement work of the jet pump can be performed by cutting, welding, replacing the reactor recirculation pump, etc. A great deal of work is not required, and it can be simplified and performed in a short time.

[Third Embodiment]
FIG. 6 shows a third embodiment of the jet pump according to the present invention.

  The jet pump 27B shown in the third embodiment is basically different from the jet pump 27 shown in the first and second embodiments in the configuration of the nozzle tip of the drive nozzle, and the other configurations and operations are the same. Since they are not substantially different, the same reference numerals are assigned to the same components, and duplicate descriptions are omitted.

  The jet pump 27B shown in the third embodiment is characterized by the shape structure of the nozzle tip 61 of the drive nozzle 60. The driving nozzle 60 has a nozzle tip 61 integrally formed on the downstream side of the nozzle body 62, and the nozzle tip 61 has a tapered nozzle taper 64 that extends from the nozzle body 62 toward the nozzle port 63. A plurality of cutout grooves 65 are formed on the outer peripheral surface tapered tip portion side of 64. The notch groove 65 is formed in the axial direction from the middle of the outer peripheral surface of the nozzle taper portion 64 toward the nozzle tip side, and the notch groove 65 is formed so that the notch depth becomes deeper toward the nozzle tip portion.

  By forming a plurality of notch grooves 65 on the outer peripheral surface of the nozzle tip 61 along the circumferential direction and gradually increasing the groove toward the nozzle tip, the drive nozzle 60 is formed on the nozzle tip 61 on the nozzle tip side. A serrated notch is formed following the groove.

  By forming a serrated notch on the outer peripheral surface of the nozzle tip 61 of the drive nozzle 60, the contact area between the drive fluid and the driven fluid can be increased, and the mixing of both fluids is promoted. Since the mixing of the driving fluid and the driven fluid is promoted, the pump efficiency of the jet pump 27B can be significantly increased.

  In the jet pump 27B shown in this embodiment, the serrated notch is formed in the outer peripheral surface of the nozzle tip portion 61 of the drive nozzle 60 in a groove shape in which the notch depth gradually increases toward the nozzle tip. Mixing of the driving fluid and the driven fluid is promoted, and the pump efficiency of the jet pump 27B can be greatly increased.

  In the third embodiment, an example in which the shape of the nozzle tip portion is different from that of the jet pump 27 of the first embodiment is shown. However, in the existing jet pump 1, only the drive nozzle may have the shape shown in FIG. Good.

  Also in this case, the jet pump 27B shown in FIG. 6 removes a part of the 180-degree vent 33, the drive nozzle 35, the throat 37, and the diffuser 38 at the mechanical fitting portion of the existing jet pump 1, The pump can be replaced with a new jet pump 27B, and the pump efficiency η can be improved while maintaining the same flow rate ratio. Therefore, the replacement of the jet pump includes a great deal of cutting work, welding work, replacement of the reactor recirculation pump, etc. There is no need for construction, which can be simplified and can be done in a short time.

[Fourth Embodiment]
FIGS. 7A and 7B show a jet pump according to a fourth embodiment of the present invention.

  The jet pump 27C shown in this embodiment is an improvement of the drive nozzle 80 and the bell mouth 85, and the drive nozzle 80 includes a plurality of, for example, five nozzle openings. Since it is not substantially different from the jet pump 27 shown in the first embodiment, common portions are denoted by the same reference numerals, and redundant description is omitted.

  In the jet pump 27 </ b> C shown in FIG. 7, the drive nozzle 80 includes a plurality of, for example, five nozzle ports 81. Each nozzle port 81 is formed on the distal end side of the nozzle distal end portion 83 provided on the downstream side of the nozzle main body 82 at intervals in the circumferential direction. The nozzle tip 83 of the drive nozzle 80 is formed in a tapered shape that tapers toward the nozzle tip as a whole. The nozzle tip 83 is branched from the middle into a plurality of nozzle legs 84, and a nozzle port 81 is formed at the tip of each nozzle leg 84. The nozzle ports 81 are arranged at intervals in the circumferential direction of the nozzle tip portion 83.

  Conventionally, as shown in FIG. 9, the jet pump 1A having five nozzle ports increases the flow area required for mixing the driving fluid and the driven fluid, and can promote the mixing of both fluids. It was thought that the pump efficiency η was higher than that of the jet pump 1 having a single nozzle port shown in FIG. However, as shown in FIG. 4, for a jet pump with a low M ratio of about 1.2, a jet pump with five nozzle ports is less efficient than a jet pump with a single nozzle port. Was confirmed by experiments. In order to set the M ratio to about 1.2, the ratio of the total area of the nozzle outlet to the throat cross-sectional area is higher than that of the conventional M ratio of 2.2. A major factor is the flow resistance of the driven fluid that passes through.

  On the other hand, the nozzle leg 84 of the drive nozzle 80 shown in FIG. 7 is provided outside the nozzle leg 84 so that the surrounding driven fluid (primary coolant) can be smoothly and smoothly guided to the bell mouth 85. The surface is a cross-sectional streamlined or bullet-shaped, and is arranged radially on a plane perpendicular to the flow of the driving fluid. Each nozzle leg 84 of the nozzle tip 83 has a taper taper shape from the base to the nozzle tip, and is formed into a cross-sectional streamlined or bullet shape so that the driven fluid passing through the nozzle leg 84 is bellmouth 85. The channel resistance is small and can be guided smoothly.

  On the other hand, as shown in FIG. 7 (B), the bell mouth 85 provided in the throat 37 has a petal-shaped outer peripheral edge in a plan view, and the same number of petal-shaped guides 85a as the nozzle legs 84 correspond. Provided. The circumscribed circle at the tip end of each nozzle leg 84 or the circumscribed circle connecting the outside of each nozzle port 81 is formed smaller than the diameter of the throat 37.

  The nozzle ports 81 of the drive nozzle 80 are provided at intervals in the circumferential direction, and the nozzle legs 84 are arranged radially with a flat cross-sectional outer shape that is streamlined or bullet-shaped. The driving fluid is jetted so that the mouth 81 faces the inside diameter of the throat 37. In addition, when the driving fluid is ejected from each nozzle port 81, the surrounding driven fluid is entrained, and the entrained driven fluid flows between the nozzle legs 84 of the nozzle tip 83 and the petal guide 85 a of the bell mouth 85. To the throat 37 from the bell mouth 85.

  For this reason, the contact area between the driving fluid ejected from each nozzle port 81 of the driving nozzle 80 and the driven fluid wound around the nozzle port 81 is increased, and the mixing is promoted. Therefore, the pump efficiency η of the jet pump 80 can be improved. In addition, since the planar cross-sectional outer shape of each nozzle leg 84 forming the flow path of the driven fluid is formed in a streamline shape or a bullet shape, the bell mouth 85 is further formed into a petal shape in plan view, thereby By increasing the flow path area of the fluid, even in a low M ratio jet pump, it is possible to reduce an increase in pressure loss due to an increase in the number of nozzle legs and the number of nozzles.

  The increase in pressure loss due to the increase in each nozzle port (nozzle number) 81 of the drive nozzle 80 can be reduced by making the outer surface of each nozzle leg 84 streamlined and the bell mouth 85 a petal shape in plan view. Furthermore, by providing each nozzle port 81 of the drive nozzle 80 with a gap G from the entrance surface of the bell mouth 85, the flow path area required for mixing the driving fluid and the driven fluid increases, and both fluids are mixed. The pump efficiency of the jet pump 27C can be improved.

  Reference numeral 86 denotes a support member that joins the bell mouth 85 and the drive nozzle 80. The support member 86 is provided using the petal guide 85a portion of the bell mouth 85 and is attached to the drive nozzle 80 integrally. .

Sectional drawing which shows the boiling water reactor provided with the jet pump which concerns on this invention. The perspective view which shows the installation state which arrange | positions the jet pump which concerns on this invention in the downcomer part in a reactor pressure vessel. (A) is a simplified side view showing a first embodiment of a jet pump according to the present invention, (B) is a partial side view showing a first embodiment. The figure which shows the characteristic of a low flow ratio jet pump. (A) is a partial side view which shows 2nd Embodiment of the jet pump based on this invention, (B) is a figure which follows the VV line | wire of FIG. 5 (A). The partial side view which shows 3rd Embodiment of the jet pump which concerns on this invention. (A) is a partial side view which shows 4th Embodiment of the jet pump based on this invention, (B) is a plane sectional view which follows the VII-VII line of FIG. 7 (A). The simplified side view which shows the conventional jet pump. (A) is a partial side view which shows the other example of the conventional jet pump, (B) is a plane sectional view which follows the IX-IX line of FIG. 8 (A). The figure which shows the characteristic of a high flow ratio jet pump.

Explanation of symbols

10 boiling water reactor 11 downcomer section 12 jet pump assembly 13 reactor pressure vessel 15 core 16 core shroud 17 core lower plenum 18 core upper plenum 20 shroud head 21 steam separator 22 stand pipe 23 steam dryer 25 reactor re- Recirculation system 26 Reactor recirculation pump 27, 27A, 27B, 27C Jet pump 28 Suction pipe 29 Discharge pipe 30 Header pipe 31 Recirculation inlet nozzle 32 Riser pipe 33 180 degree vent 35 Drive nozzle 35a Nozzle port 36 Bell mouth 37 Throat 38 Diffuser 39 Tail pipe 40, 41 Mechanical fitting part 44 Mixing pipe part (straight pipe part)
45 Taper tube portion 46 Support member 47 Nozzle body 48 Nozzle tip portion 50 Drive nozzle 51 Nozzle tip portion 52 Nozzle body 53 Nozzle port 54 Nozzle taper portion 55 Recessed portion 60 Drive nozzle 61 Nozzle tip portion 62 Nozzle body 63 Nozzle port 64 Nozzle taper portion 65 Notch Groove 80 Drive nozzle 81 Nozzle port 82 Nozzle body 83 Nozzle tip 84 Nozzle leg 85 Bell mouth 85a Petal guide 86 Support member

Claims (2)

A drive nozzle that ejects drive fluid from the nozzle opening;
A bell mouth that guides the driven fluid in the surrounding area by the driving fluid ejected from the driving nozzle;
A throat that mixes the driving fluid and the driven fluid from the bell mouth,
A diffuser connected to the downstream side of the throat and discharging the mixed fluid;
The drive nozzle is provided with a plurality of nozzle legs branched at the nozzle tip in the circumferential direction, and each nozzle leg is radially arranged with a flat cross-sectional outer shape being a streamline or a bullet shape. A jet pump characterized by that. The bell mouth is provided with an inlet facing the nozzle opening of the drive nozzle, and the bell mouth outer shape of the bell mouth substantially perpendicular to the flow direction of the drive fluid from the drive nozzle is configured in a petal shape. The jet pump according to claim 1 .

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