JP2006349536A - Jet pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the performance of a jet pump by changing the nozzle geometry of driving water of the jet pump. <P>SOLUTION: The jet pump has a constitution where recirculation water 10 of a boiling water reactor is supplied to a plurality of nozzles 9 of a jet pump as driving water; while the flow is passing the path 22 of the driving water of the nozzles 9, the driving water is guided by spiral projections 25 provided to the inner wall surface in the path and swirls; and the driving water 23, having swirled and flowed out of the nozzles 9, accompanies cooling water 8, existing around the nozzles 9 as water to be driven, and goes inside a bellmouth 24 of a mixer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a jet pump used in a reactor recirculation system of a boiling water reactor.

  In a conventional boiling water reactor (BWR) that uses a jet pump in the system of the reactor recirculation system, the recirculation pump sucks the cooling water in the reactor pressure vessel as recirculation water and boosts the pressure. Recirculated water is supplied as driving water to the jet pump in the reactor pressure vessel. The jet pump includes a nozzle and a mixer. When the driving water is received by the nozzle, the speed of the driving water is increased by the nozzle and discharged to the mixer, the cooling water around the nozzle is driven into the mixer as driven water by the driving water. It flows with water and increases the flow rate, and circulates it as cooling water to the reactor core in the reactor pressure vessel (see, for example, Patent Document 1).

U.S. Pat. No. 3,625,820

  The performance of the jet pump is expressed by the M ratio, N ratio, and efficiency as shown below. The M ratio is a ratio of the flow rate Qb of driven water (cooling water) to the flow rate Qa of driving water (recirculation water).

M ratio = Qb / Qa (1)
N ratio is the total head ratio of driven water to driving water, and is expressed by the following equation.

N ratio = (Hc−Hb) / (Ha−Hc) (2)
Here, Ha is the total head at the driving water inlet of the nozzle, Hb is the total head at the driven water inlet of the jet pump, and Hc is the total head at the jet pump outlet. Efficiency is the ratio of driven water energy to driving water, and is expressed as the product of the M ratio and the N ratio.

Efficiency = M ratio × N ratio As a jet pump, a high M ratio, a high N ratio, and a high efficiency are desirable. If the flow rate at the outlet of the jet pump can be increased efficiently by using a recirculation pump having a small capacity, the facility cost and installation space of the recirculation system can be reduced. This makes it possible to rationalize the new plant and reduce the cost of remodeling the existing plant.

  For example, when increasing the power output of an existing nuclear reactor, the increase in power output can be expanded by increasing the core flow rate to increase the cooling capacity of the core. In addition, by expanding the core flow rate control width during operation, it is possible to increase the void ratio change in the core and adjust the deceleration of neutrons, thereby improving fuel economy. As means for increasing the core flow rate, improvement of recirculation pumps, feed water pumps, and jet pumps can be considered. However, modification of existing reactors requires the use of large equipment such as recirculation pumps and feed water pumps. Compared to remodeling and replacement, the improvement of the jet pump is effective. Since the performance of the jet pump largely depends on the shape of the mixing portion of the driving water and the driven water, the performance may be improved by replacing only the driving water nozzle.

  In general, in a jet pump, the efficiency decreases when the M ratio is increased. Therefore, in order to achieve a high M ratio, a high N ratio, and a high efficiency, it is necessary to add a new function. The present invention provides a new means for achieving a high M ratio, high N ratio, high efficiency jet pump. In particular, by changing only the nozzle shape of the driving water, it is not necessary to modify or replace parts other than the nozzle of the jet pump, equipment such as the recirculation pump and the feed water pump.

  Means for solving the problems of the present invention is a jet pump comprising: a plurality of nozzles; and a mixer whose inlet faces the discharge ports of the plurality of nozzles. A jet pump characterized in that a swirl flow generating structure for swirling the fluid flowing through the nozzle to the mixer is provided, and a horizontal swirling force is applied to the driving fluid by the nozzle and flows into the mixer. The interval between the horizontal cross-sectional areas of each flow of each driving fluid is enlarged to smoothly flow the driven fluid into the mixer.

  Alternatively, in a jet pump comprising a plurality of nozzles and a mixer having an inlet facing the discharge ports of the plurality of nozzles, the discharge ports of the plurality of nozzles are arranged in a row of the plurality of nozzles. The jet pump has a flat structure in which the width of the nozzle outlet is shortened in the direction, and the horizontal cross-sectional shape of the flow of each driving fluid discharged from each nozzle to the mixer is represented by the discharge port of each nozzle. The shape is flattened, and the interval between the horizontal cross-sectional areas of the flow of each driving fluid is enlarged to smoothly flow the driven fluid into the mixer.

  ADVANTAGE OF THE INVENTION According to this invention, the flow loss area of the driven fluid by a driving fluid can be suppressed, the pressure loss of a driven fluid can be reduced, and the performance of a jet pump can be improved.

  A conceptual diagram of a boiling water reactor is shown in FIG. The main feed water 4 fed from the main feed water pipe 3 to the reactor pressure vessel 1 is mixed with the cooling water 5 at the upper part of the reactor pressure vessel 1, and between the shroud 6 on the outer periphery of the reactor core 2 and the reactor pressure vessel 1. Downcomer 7 flows down. The cooling water 8 that has flowed down the downcomer 7 is mixed with the recirculated water 10 from the nozzle 9 provided inside the downcomer 7 inside the mixer 11 to become the cooling water 12, which is sent into the core 2. The cooling water 12 passes through the core 2 to be in a two-phase state of water and steam, and is separated into steam and water by the steam / water separator 13.

  The steam is further dehumidified by the steam dryer 14, flows out from the main steam pipe 15 as main steam 16, and is sent to a downstream steam turbine. The water separated by the steam separator 13 and the steam dryer 14 falls and mixes with the feed water 4 outside the shroud 6. The recirculation system includes a suction pipe 17, a recirculation pump 18, and a discharge pipe 19 as main components. A part of the cooling water 8 flowing down the downcomer 7 is taken into the recirculation system through the suction pipe 17 as recirculation water, and is pressurized by the recirculation pump 18 and supplied to the nozzle 9 from the discharge pipe 19.

  The recirculated water 10 is used to increase the flow rate of the cooling water 12 fed into the core 2. When the momentum of the recirculated water 10 is effectively given to the cooling water 8, the cooling water 8 is driven and the flow rate is increased. Therefore, the flow velocity of the cooling water 8 is increased by increasing the outlet flow velocity of the nozzle 9 so that the momentum of the recirculated water 10 that is driving water is increased, and the flow passage area is reduced at the inlet of the mixer 11. Reduce.

  Thereby, the cooling water 8 can be sucked into the mixer 11. The jet pump 20 having the nozzle 9 and the mixer 11 as main components effectively transmits the power of the recirculation pump 18 from the recirculation water 10 to the cooling water 8, and the jet pump outlet rather than the flow rate of the recirculation water 10. This is a device that can increase the flow rate of the cooling water 12. Thereby, a necessary core flow rate can be secured.

  The nozzle 9 of the jet pump 20 is provided with a swirl flow generating structure that swirls the cooling water flowing through the nozzle 9 to the mixer 11, or the discharge ports of the plurality of nozzles 9 are provided for the plurality of nozzles 9. In the arrangement direction, the structure has a flat structure in which the width of the outlet of the nozzle 9 is shortened, and the interval between the horizontal cross-sectional areas of the flow of the cooling water from each nozzle 9 to the mixer 11 is enlarged to The flow of cooling water into the mixer is smooth.

  The swirl flow generation structure and the flat configuration of the nozzle 9 outlet are as in the following embodiments. In the following embodiments, the above-mentioned contents are common.

  FIG. 1 shows an embodiment of a jet pump according to the present invention. The driving water 10 flows out from the tip of the nozzle 9 through the inside of the flow path 22 provided in the support part 21 of the nozzle 9 and the nozzle 9. The driving water 23 flowing out from the tip of the nozzle 9 flows into the mixer 11 together with the driven water 8. As in the conventional example, a bell mouth 24 is provided at the inlet of the mixer 11 so that the flow can flow smoothly. In the present embodiment, a spiral protrusion 25 is provided inside the flow path 22, and the swirl component is given to the drive water 10, thereby causing the swivel drive water 23 to flow out of the nozzle 9.

  FIG. 2 is an enlarged view of the flow path 22. On the wall surface of the flow path 22, a spiral protrusion 25 is provided so as to protrude inward, and the driving water 10 in the outer peripheral portion flows spirally along the surface of the spiral protrusion 25. Even when the same circumferential flow velocity is given, the fluid in the outer peripheral portion has the largest angular momentum, and therefore the driving water 10 can be effectively swirled by giving a swirling component to the outer peripheral portion.

  FIG. 3 shows the pressure distribution inside the mixer 11. The driving water 23 that has flowed out from the tip of the nozzle 9 flows into the mixer 11 together with the surrounding cooling water 8. A bell mouth 24 is provided at the inlet of the mixer 11, and the flow area of the mixer 11 is gradually narrowed to accelerate the flow. Therefore, the flow is most restricted at the connecting portion between the bell mouth 24 and the mixer 11, the static pressure becomes low, and the static pressure gradually recovers downstream as the flow velocity distribution becomes uniform. Therefore, the form of the flow at the connecting portion (cross section AA in FIG. 3) between the bell mouth 24 and the mixer 11 greatly affects the characteristics of the jet pump such as the M ratio and efficiency.

  FIG. 4 is a diagram schematically showing the result of numerical analysis of the flow in the vicinity of the conventional nozzle 9 without swirling. Here, only the flow path sector of the angle θ occupied by one nozzle 9 in the connecting portion (cross section AA in FIG. 3) of the bell mouth 24 and the mixer 11 is shown in the figure, A plurality of similar nozzles 9 are provided periodically. The driving water 23 that has flowed out of the nozzle 9 generates a flow that entrains the driven water 8 in the direction of the center 26 of the flow path sector. At this time, since the driving water 23 also becomes an obstacle to the driven water 8, a circulating flow of the driven water 8 is generated so as to bypass the driving water 23. This circulating flow causes a flow from the center 26 to the outside, and deforms the cross-sectional shape of the driving water 23. As a result, the cross-sectional shape of the driving water 23 spreads in the circumferential direction of the flow channel sector, and the flow channel area through which the driven water 8 passes becomes narrow. For this reason, the pressure loss of the driven water 8 increases and the efficiency decreases.

  FIG. 5 is a schematic diagram of a numerical analysis result when the present embodiment is applied. In this case, since the swirl 9a is added to the driving water 23 flowing out from the nozzle 9, the cross-sectional shape of the driving water 23 is a shape rotated in the swirling direction as compared with the conventional example. Thereby, the flow path area of the driven water 8 is enlarged in the portion of the driving water 23. Therefore, the pressure loss of the driven water 8 is reduced and the efficiency is improved.

  FIG. 6 is a comparative diagram of the efficiency obtained by the numerical analysis. In this M ratio region, when turning is not given, the efficiency decreases as the M ratio increases. On the other hand, when turning is given, the maximum point of efficiency moves to the higher M ratio side, and the efficiency is greatly improved. When the turning angle is further increased, the spread of the drive water 23 is increased, the pressure loss on the nozzle side is increased, and the efficiency is lowered. If the turning angle is reduced, the effect of turning cannot be obtained.

  Therefore, in order to improve the efficiency, there is an appropriate turning angle, and the efficiency can be improved by selecting the turning angle. The turning angle θ (degrees) is selected so as to satisfy the following relationship.

45r / H <θ <135r / H (1)
Here, r is the outlet (discharge port) radius of the nozzle 9, and H is the distance from the nozzle 9 outlet (discharge port) tip to the minimum flow path area position (AA cross-sectional position in FIG. 3) at the mixer 11 inlet. The time for the driving water 23 to reach the minimum flow path area position at the inlet of the mixer 11 from the outlet tip of the nozzle 9 is H / U, where U is the axial flow velocity at the outlet of the driving water 23. On the other hand, the turning angle per unit time is W / r, where W is the turning flow velocity at the outlet of the driving water 23. Therefore, the angle γ (rad) at which the driving water 23 turns from the nozzle 9 outlet tip to the minimum flow path area position at the inlet of the mixer 11 is H / U × W / r. Since the swivel angle θ (rad) at the outlet of the nozzle 9 can be written approximately as W / U, γ (rad) becomes H / r × θ (rad). Therefore, θ (degrees) is r / H × γ (degrees). By setting γ to about 90 degrees, the cross-sectional shape of the driving water 23 spreading in the circumferential direction of the channel sector is changed in the radial direction of the channel sector so that the channel area through which the driven water 8 passes is narrow. Can be prevented. γ does not need to be exactly 90 degrees, and an optimal value may be obtained within a range of ± 45 degrees so that the cross-sectional shape of the driving water 23 is directed from the circumferential direction of the flow path sector to the radial direction. Expression (1) expresses these relationships. When the turning angle θ is increased, the spread of the driving water 23 becomes larger. Therefore, it is desirable to suppress the turning angle θ to a weak turning of 20 degrees or less so that the backflow of the driving water 23 does not occur.

  As shown in FIG. 7, by rounding the corners of the spiral projection 25, the pressure loss on the nozzle side can be further reduced. By providing the roundness, separation of the flow at the corner of the protrusion 25 is suppressed, and the pressure loss can be reduced. On the other hand, since the turning force is weakened by providing the roundness, the decrease in the turning force can be compensated for by making it larger than the turning angle at which the helical angle α should be given.

  FIG. 8 shows another embodiment of the present invention. In this embodiment, a spiral recess 27 is provided on the wall surface of the flow path 22 instead of the spiral protrusion 25 of the first embodiment, and the driving water 10 in the outer peripheral portion spirals along the recess 27. Flowing into. Also according to the present embodiment, the driving water 10 can be swirled effectively by giving a swirling component to the outer peripheral portion having the largest angular momentum. The other contents are the same as in the first embodiment.

  FIG. 9 shows another embodiment of the present invention. In this embodiment, instead of the spiral projection 25 of the first embodiment, a swirl vane 28 is provided upstream of the flow path 22, and swirling can be applied to the driving water 10. The swirl vane 28 is a propeller-like stationary structure having a support on the central axis of the nozzle 9 and a cylindrical structure on the outer periphery. The support and the outer cylindrical structure are in an annulus space between the support and the outer cylindrical structure. A plurality of blade surfaces with inclinations supported at both ends are attached.

  When the flow is generated along the blade surface, the driving water 10 can be swirled. In order to suppress an increase in the pressure loss of the driving water 10, swirl vanes are installed in the flow path expanding portion where the flow velocity of the driving water 10 becomes low. Also according to the present embodiment, the driving water 10 can be swirled effectively. The other contents are the same as in the first embodiment.

  FIG. 10 shows another embodiment of the present invention. In the present embodiment, an inlet 30 for the driving water 10 is provided at the center of the support portion 21 of the nozzle 9, and the inlet 30 and the flow path 22 are connected by the flow path 31. The flow path 31 is attached with the central axis of the flow path 22 removed, whereby the drive water 10 can be swirled inside the flow path 22. The turning angle can be set by adjusting the angle β formed by the flow path 31 and the flow path 22.

  FIG. 10 shows the case of an even number of 6 nozzles, and the flow path 31 is provided so that the swirling directions of the adjacent nozzles 9 are reversed. For this reason, the flow which came out of the nozzle 9 can flow without canceling a rotation, and loss is reduced. In this case, the number of nozzles 9 is not limited to six, and loss can be reduced if it is an even number such as four or eight. Also according to the present embodiment, the driving water 10 can be swirled effectively.

  FIG. 11 shows another embodiment of the present invention. In the present embodiment, triangular blades 32 are provided on the wall surface of the flow path 22 of the driving water 10 instead of the spiral protrusions 25 of the first embodiment. The triangular wing 32 has two surfaces 33 and 34 having different angles of attack with respect to the flow of the driving water 10, and a static pressure difference is generated between the surfaces 33 and 34. Due to this static pressure difference, the swirl 9b is generated downstream of the triangular blade 32, and the drive water 10 can be swirled.

  Also according to the present embodiment, the driving water 10 can be swirled effectively. In particular, in the present embodiment, the change in the flow path area of the flow path 22 due to the installation of the triangular blades 32 can be reduced, so that the pressure loss of the driving water 10 can be kept low. The other contents are the same as in the first embodiment.

  FIG. 12 shows another embodiment of the present invention. In this embodiment, the driven water 8 is swirled by providing swirl vanes 35 on the outer periphery of the nozzle 9 in place of the spiral projection 25 of the first embodiment. By the swiveling of the driven water 8, the driving water 23 that has flowed out of the nozzle 9 can be swirled.

  Also according to the present embodiment, the driving water 23 can be effectively swirled. In particular, in this embodiment, the pressure loss of the driving water 10 does not increase compared to the conventional example without turning. On the other hand, the pressure loss on the driven water 8 side increases, but the pressure loss increases only in the vicinity of the nozzle 9, and the pressure loss increase of the driven water 8 as a whole is small. Therefore, it is possible to suppress a reduction in efficiency due to turning. The other contents are the same as in the first embodiment.

  FIG. 13 shows another embodiment of the present invention. In this embodiment, the outlet of the nozzle 9 has a flat structure. In particular, the width of the outlet of the nozzle 9 is shortened in the direction in which the plurality of nozzles 9 are arranged. That is, the nozzle outlet in the BB direction in FIG. 13 is narrow, and the nozzle outlet in the CC direction in FIG. 13 is wide. Since the cross-sectional shape of the flow coming out of the nozzle 9 is narrow in the BB direction, it is less likely to be an obstacle to the driven water 8 toward the center 26 direction and the pressure loss of the driven water 8 is reduced compared to a non-flat structure. .

  For this reason, as in the first to seventh embodiments, there is an effect similar to that in the case where the driving water 10 is swirled, and the pressure loss on the driven water 8 side is reduced, and the efficiency can be improved.

  The present invention is applied to a jet pump employed in a boiling water reactor.

It is a principal part longitudinal cross-sectional view of the jet pump of Example 1 of this invention. It is a longitudinal cross-sectional view of the flow path part of the driving water in the nozzle of FIG. It is a figure which shows the pressure distribution in the jet pump of Example 1 of this invention. It is the top view which showed the relationship between the driving water without rotation, and driven water. It is the top view which showed the relationship between the driving water by Example 1 of this invention, and driven water. It is a graph showing the performance of the jet pump by Example 1 of this invention. It is a longitudinal cross-sectional view of the flow-path part of the driving water by the modification of Example 1 of this invention. It is a longitudinal cross-sectional view of the flow-path part of the driving water of the nozzle of Example 2 of this invention. It is a longitudinal cross-sectional view of the nozzle of Example 3 of this invention. FIG. 4A is a configuration diagram of a nozzle according to a fourth embodiment of the present invention, and FIG. 4A is a plan layout diagram of each flow path showing an eccentric state between the flow path of the driving water and the inlet flow path; FIG. FIG. 3 is a longitudinal sectional view of a nozzle. In the configuration diagram of the nozzle of Example 5 of the present invention, (a) is a longitudinal sectional view of the flow path of the driving water, and (b) is a plan sectional view of the flow path of the driving water. It is a longitudinal cross-sectional view of the nozzle of Example 6 of this invention. It is a block diagram of the nozzle of Example 7 of this invention, (a) A figure is a longitudinal cross-sectional view of the discharge outlet of a nozzle, and (b) A figure is a longitudinal cross-sectional view of the other direction of a nozzle discharge outlet. (C) The figure is a plane sectional view showing the relation between the flow path of the drive water of the nozzle and the discharge port. It is a conceptual diagram of a boiling water reactor (BWR).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Core, 3 ... Main feed water piping, 4 ... Main feed water, 5 ... Cooling water of upper part of reactor pressure vessel, 6 ... Shroud, 7 ... Downcomb, 8 ... Cooling water flowing down downcomb ( Driven water), 9 ... nozzle, 9a, 9b ... swirl, 10 ... recirculated water (driving water), 11 ... mixer,
DESCRIPTION OF SYMBOLS 12 ... Cooling water which goes to a reactor core from a mixer, 13 ... Gas-water separator, 14 ... Steam dryer, 15 ... Main steam piping, 16 ... Main steam, 17 ... Suction piping, 18 ... Recirculation pump, 19 ... Discharge piping ,
DESCRIPTION OF SYMBOLS 20 ... Jet pump, 21 ... Nozzle support part, 22 ... Drive water flow path, 23 ... Drive water which flowed out from nozzle, 24 ... Bell mouth, 25 ... Spiral protrusion, 26 ... Center of multiple nozzles,
27 ... spiral recess, 28, 35 ... swirl vane, 30 ... driving water inlet, 31 ... flow path,
32 ... Triangular wing, 33,34 ... Triangular wing surface.

Claims (11)

In a jet pump comprising a plurality of nozzles and a mixer whose inlet faces the discharge ports of the plurality of nozzles,
A jet pump characterized in that a swirl flow generating structure for swirling the fluid flowing through the nozzle to the mixer is provided in the nozzle. In claim 1,
The jet pump according to claim 1, wherein the swirl flow generating structure is a protrusion provided in a spiral shape on an inner wall of the nozzle. In claim 1,
The jet pump according to claim 1, wherein the swirl flow generating structure is a recess provided in a spiral shape on an inner wall of the nozzle. In claim 1,
The jet pump characterized in that the swirl flow generating structure is a swirl vane fixed inside the nozzle. In claim 1,
The swirl flow generating structure is a flow path structure on the inlet side of the nozzle that is eccentrically connected to the flow path from the lateral direction of the flow path so that the fluid flows spirally in the flow path in the nozzle. A jet pump characterized by being. In claim 1,
The jet pump according to claim 1, wherein the swirl flow generating structure is a triangular wing having two surfaces provided on an inner wall of the nozzle and having different angles of attack with respect to the fluid flow in the nozzle. In claim 1,
The jet pump according to claim 1, wherein the swirl flow generating structure is a swirl vane that is provided on an outer periphery of the discharge port of the nozzle and generates a swirl flow on a fluid flowing along the outer periphery.   The swirl according to any one of claims 1 to 7, wherein the symbol r is a radius of the nozzle and the symbol H is a distance from a tip of the nozzle to a minimum flow path area position of the mixer inlet. The jet pump satisfies the formula 45r / H <θ <135r / H and is 20 degrees or less. In any one of Claim 1 to Claim 8,
The jet pump according to claim 1, wherein a swirling direction of the fluid from the adjacent nozzles is opposite. In claim 9,
A jet pump characterized in that the number of nozzles is an even number. In a jet pump comprising a plurality of nozzles and a mixer whose inlet faces the discharge ports of the plurality of nozzles,
The jet pump, wherein the discharge ports of the plurality of nozzles have a flat structure in which a width of the nozzle outlet is shortened in an arrangement direction of the plurality of nozzles.

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