JP2009085864A - Jet pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a jet pump where the suction amount of fluid to be driven is improved, by suppressing the reduction in the speed of driving fluid at throat inlet and the M ratio of the jet pump and the efficiency of the jet pump. <P>SOLUTION: The jet pump comprises a nozzle for blowing out the driving fluid, a bell-mouth for sucking the surrounding fluid to be driven with the driving fluid blown from the nozzle, a throat where the driving fluid mixes with the sucked fluid to be driven, and a diffuser for pressurizing and delivering the mixed fluid. A plurality of nozzles 31a and 31b are arranged concentrically on a nozzle pedestal 20 to which the nozzles are mounted. Each nozzle has nozzle straight pipe sections 32 and 34 and a plurality of nozzle throttle sections 33 and 35, where flow channel is throttled, and the nozzle throttle angle θ2 of the nozzle throttle section 35 close to a nozzle blowout port 40 of the nozzle is set larger than the nozzle throttle angle θ1 of the other nozzle throttle section. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a jet pump installed in a pressure vessel of a boiling water reactor.

  In a boiling water reactor, in order to secure a flow rate of reactor water as cooling water to be circulated in the reactor core with a small driving fluid flow rate, as described in Japanese Patent Application Laid-Open No. 59-188100, A jet pump is installed.

  The driving fluid of the jet pump draws the reactor water from the inside of the pressure vessel through a pipe, pressurizes it with a recirculation pump, and ejects it from the nozzle of the jet pump to the throat on the downstream side.

  The driving fluid ejected from the nozzle reduces the static pressure inside the throat of the jet pump, and the driven fluid around the bell mouth at the top of the throat passes through the bell mouth and is sucked into the throat so that the driving is performed at the throat portion. Mix and exchange fluid and momentum and flow into diffuser at bottom of throat.

  In the diffuser, the flow path area is gradually expanded to the extent that the flow does not separate, and the kinetic energy is converted to pressure while passing through the diffuser, and the pressure is higher than the pressure of the driven fluid before being sucked, and then discharged from the diffuser. Then, the reactor water is supplied to the core.

  Based on the above principle, the jet pump can discharge a larger flow rate than the flow rate of the driving fluid downstream.

  As an example of a jet pump used in a boiling water reactor, the jet pump described in Japanese Patent Laid-Open No. 59-188100 has five nozzles, and each nozzle has a flow path near its tip. A technique is disclosed in which the driving fluid is ejected at a high speed as a shape that is narrowed in one step.

  In the jet pump described in JP-A-7-119700, a long nozzle is attached to the central axis of the jet pump, and a plurality of short nozzles are attached at equal pitches in the circumferential direction so as to surround the long nozzle. A technique for improving the efficiency of a jet pump by smoothly accelerating a driven fluid in two stages of a long nozzle and a short nozzle is disclosed.

JP 59-188100 A JP 7-119700 A

  When the efficiency of the jet pump is improved, the flow rate of the reactor water supplied to the core increases, and the control range of the core flow rate can be expanded to improve the fuel economy.

  In the jet pump, the high-speed driving fluid ejected from the nozzle draws in the surrounding driven fluid by lowering the static pressure in the throat, and the driving fluid is ejected from the nozzle toward the throat at a certain spread angle. The

  When this divergence angle is reduced, the decrease in the jet velocity when the driving fluid reaches the throat portion is suppressed, and the static pressure in the throat portion can be further reduced, so that the driven fluid can be sucked in more.

  As a means for reducing the divergence angle of the driving fluid, there is a method of increasing the throttle angle at the nozzle tip of the jet pump. JP-A-59-188100 discloses a structure in which the flow path of the nozzle of the jet pump is throttled in one step. Technology is disclosed.

  However, in the structure in which the flow path of the nozzle of the jet pump described in Japanese Patent Laid-Open No. 59-188100 is throttled in one step, if the nozzle orifice diameter is kept constant and the nozzle tip angle is increased, The diameter or length must be large, and as a result, the nozzle itself becomes the flow path resistance of the driven fluid, and thus the efficiency of the jet pump is inevitably reduced.

  Further, when the driven fluid is smoothly accelerated, the loss is reduced and the efficiency of the jet pump is improved. However, in the nozzle having a long nozzle and a plurality of short nozzles described in JP-A-7-119700, It is difficult to properly distribute the flow rate of the long nozzle and multiple short nozzles around it, and the flow rate tends to be biased in either direction. If the flow rate distribution is uneven, the driven fluid is not smoothly accelerated and the jet pump It is highly possible that the efficiency of the system cannot be improved.

  An object of the present invention is to provide a jet pump that improves the M ratio of the jet pump and the efficiency of the jet pump by suppressing the speed reduction of the driving fluid at the throat inlet and increasing the suction amount of the driven fluid. It is in.

  The jet pump of the present invention includes a riser pipe that guides the driving fluid to the nozzle, a vent pipe that is installed on the downstream side of the riser pipe and turns the flow of the driving fluid guided from the riser pipe, and a downstream side of the vent pipe A nozzle which ejects the driving fluid which is installed in the vent pipe and is turned by the vent pipe, a bell mouth which is a suction port for the surrounding driven fluid, and a driven which is installed downstream of the bell mouth and sucked from the bell mouth In a jet pump having a throat that mixes a fluid and a driving fluid ejected from the nozzle, and a diffuser that is disposed downstream of the throat and increases the pressure of the mixed fluid and discharges the nozzle, the nozzle is attached to the nozzle A plurality of nozzles are concentrically arranged on a pedestal, and each nozzle has a straight nozzle section with a constant flow path diameter and a flow path downstream of the nozzle straight pipe section. A plurality of nozzle throttle portions each having a reduced nozzle diameter, and the nozzle aperture angle of the nozzle aperture portion close to the nozzle outlet of the nozzle aperture portions is formed to be larger than the nozzle aperture angle of the other nozzle aperture portions. Further, a nozzle lower end portion having a nozzle outlet at the tip thereof and having a constant or gently narrowed passage diameter is provided on the downstream side of the nozzle restrictor close to the nozzle outlet.

  According to the present invention, it is possible to realize a jet pump that improves the M ratio of the jet pump and the efficiency of the jet pump by suppressing the speed reduction of the driving fluid at the throat inlet and increasing the suction amount of the driven fluid.

  A jet pump installed in a boiling water reactor that is an embodiment of the present invention will be described below with reference to the drawings.

  A jet pump according to an embodiment to which the present invention is installed in a boiling water reactor will be described with reference to FIGS. 1 and 2.

  FIG. 2 is a longitudinal sectional view showing a boiling water reactor, and a reactor core 5 whose outer periphery is covered with a shroud 2 is installed in the lower part of the inside of the pressure vessel 3.

  And the steam-water separator 6 is installed in the upper part of the core 5 inside the pressure vessel 3, and it has the structure where the steam dryer 7 was installed in the upper part of this steam-water separator 6. FIG.

  The jet pump 1 that supplies reactor water to the core 5 is installed in a downcomer 4 in a space formed between the outer peripheral side of the shroud 2 that covers the core 5 inside the pressure vessel 3 and the inner peripheral side of the pressure vessel 3. ing.

  Reactor water sent from the downcomer 4 to the core 5 by the jet pump 1 is boiled by nuclear heat, flows into the steam-water separator 6 installed at the upper part of the core 5, and is separated into steam and water. The steam which has flowed into the steam dryer 7 installed on the upper part of the water separator 6 and dried is separated.

  The separated and dried steam is supplied from the inside of the pressure vessel 3 to the steam turbine (not shown) through the main steam pipe 8 disposed on the upper portion of the pressure vessel 3 to drive the steam turbine.

  Further, the reactor water separated by the steam separator 6 inside the pressure vessel 3 is returned to the downcomer 4 again.

  The reactor water that has returned to the downcomer 4 is mixed with the feedwater supplied from the outside of the pressure vessel 3 through the water supply pipe 9 provided in the pressure vessel 3 and sucked into the jet pump 1 installed in the downcomer 4 again, and the core 5 Sent to.

  The driving fluid of the jet pump 1 uses the reactor water of the downcomer 4.

  That is, a pipe 11 for leading the reactor water from the downcomer 4 is disposed outside the pressure vessel 3, and the reactor water of the downcomer 4 drawn through the pipe 11 is boosted by the recirculation pump 12 installed in the pipe 11, The pressurized reactor water is sent as a driving fluid to the jet pump 1 installed in the downcomer 4 through this pipe 11.

  FIG. 3 is an enlarged view of the jet pump 1 installed in the boiling water reactor shown in FIG. 2, and the driving fluid sent from the recirculation pump 12 through the pipe 11 is a riser pipe constituting the jet pump 1. 13, and the supplied driving fluid is changed in the direction of the flow by 180 ° in the vent pipe 14 disposed on the upper part of the jet pump 1 on the downstream side of the riser pipe 13, and then the vent pipe 14 is guided to a nozzle 31 installed on the downstream side.

  Then, the driving fluid is ejected from the nozzle 31 toward the bell mouth 16 and the throat 17 on the downstream side at a high speed.

  A throat 17 having a bell mouth 16 is installed on the lower portion of the nozzle 31, and the bell mouth 16 reduces the static pressure in the throat 17 by ejecting a driving fluid from the nozzle 31 to the throat 17 at a high speed. Then, the lowering of the static pressure is used to suck the peripheral fluid (driven fluid) of the downcomer 4 from the bell mouth 16 and smoothly guide it to the throat 17.

  In an existing nuclear reactor, it is possible to suck in an ambient fluid (driven fluid) that is approximately twice as large as the jetted driving fluid.

  Then, the driving fluid ejected from the nozzle 31 and the driven fluid sucked from the bell mouth 16 are mixed while exchanging the momentum inside the throat 17, and sent to the diffuser 18 disposed below the throat 17.

  The diffuser 18 is formed so that the flow path is gradually enlarged so that the flow does not cause separation, and the kinetic energy is converted into pressure by the diffuser 18.

  In the diffuser 18, the driven fluid has a pressure higher than the pressure at the suction position, and a mixed fluid in which the driving fluid and the driven fluid are mixed is discharged from the diffuser 18, and the reactor water is discharged from the jet pump 1. Is sent to the core 5.

  Thus, since the jet pump 1 can send a large flow rate of reactor water to the core 5 with a small flow rate of driving fluid, the pipe diameter of the recirculation system can be reduced.

  The reactor power is also controlled by the flow rate of the reactor water flowing through the core, but by controlling the power of the recirculation pump 12, the flow rate of the driving fluid ejected from the nozzle 31 of the jet pump 1 is changed, The core flow rate can be controlled.

  By the way, the performance of the jet pump 1 can be indicated by an M ratio, which is a ratio of the driving fluid flow rate to the driven fluid flow rate, and an N ratio, which is a pressure ratio.

  The definition of the M ratio is M = Qs / Qn, and the definition of the N ratio is N = (Pd−Ps) / (Pn−Pd).

  Here, Q is the flow rate, P is the total pressure, and the suffixes n, s, and d indicate the nozzle part 31, the suction part of the bell mouth 16, and the diffuser part 18, respectively.

  The jet pump efficiency η is expressed by the product of M ratio and N ratio η = M × N × 100 (%).

  When the M ratio of the jet pump 1 and the jet pump efficiency η are improved, a predetermined core flow rate can be secured with a smaller driving water flow rate, so that the power of the recirculation pump 12 can be reduced and the running cost can be suppressed. .

  Further, if the core flow rate is increased to expand the control range of the core flow rate, the burnup at the end of the fuel cycle of the nuclear reactor can be improved, so that fuel economy is improved.

  In addition, if a high-M ratio, high-efficiency jet pump is used, there is no need to replace the recirculation pump 12 with a high-performance pump in order to increase the core flow rate.

  Therefore, when the M ratio of the jet pump and the jet pump efficiency are improved, a predetermined core flow rate can be secured with less recirculation pump power, and the running cost of the recirculation pump 12 can be reduced.

  Further, if the core flow rate is increased in response to the increase in the core power, the fuel economy is improved. However, by using a jet pump having an improved M ratio and jet pump efficiency, the recirculation pump 12 can be operated with the same pump power. Since the core flow rate corresponding to the increase in the core power can be secured as it is, it is not necessary to replace the recirculation pump 12 with a high-performance pump, and the cost of equipment replacement accompanying the power improvement can be suppressed.

  1 and 4 show the detailed structure of the nozzle 31 installed in the jet pump of this embodiment shown in FIG.

  1 and 4, the nozzle 31 installed in the jet pump 1 of the present embodiment has a structure in which a total of six substantially cylindrical nozzles 31a extending downward are arranged on the nozzle base 20 in a concentric manner at equal intervals. It has become.

  Details of these nozzles 31a will be further described with reference to FIG.

  As shown in FIG. 5, when the nozzle 31a defines the nozzle inner diameter as a flow path diameter sequentially from D1 to D5 from the upstream side to the downstream side of the nozzle, the size of the nozzle inner diameter is D1> D2 = D3> D4 = D5. It is formed to become.

  That is, in the jet pump 1 of the present embodiment, the nozzle 31a is positioned on the downstream side of the nozzle straight pipe portion 32 having the nozzle inner diameter D1 having a constant flow path diameter on the most upstream side of the nozzle and the nozzle straight pipe portion 32. The first stage nozzle throttling portion 33 having a length L1 that decreases from the nozzle inner diameter D1 to D2 whose flow passage diameter is reduced, and the inner diameter D2 that is located downstream of the nozzle throttling portion 33 and has a constant flow passage diameter. A nozzle straight pipe portion 34 having a nozzle inner diameter D3 having the same diameter as that of the second nozzle, and a second L2 having a length L2 at which the nozzle inner diameter with a flow passage diameter reduced downstream from the nozzle straight pipe portion 34 is reduced from D3 to D4. A nozzle having a nozzle nozzle portion 35 having a nozzle D5 having the same diameter as the inner diameter D4 which is located on the most downstream side which is the downstream side of the nozzle throttle portion 35 and has a constant flow path diameter. It is comprised from the lower end part 36.

  In the nozzle 31a of the jet pump 1 of the present embodiment, the nozzle flow path is narrowed at two locations, the first-stage nozzle throttle section 33 and the second-stage nozzle throttle section 35 described above. .

  As described above, the nozzle straight pipe portion 32 and the nozzle straight pipe portion 34 are provided upstream of the nozzle throttling portion 33 and the nozzle throttling portion 35, respectively.

  In the nozzle 31a of the jet pump 1 of the present embodiment, the aperture angle θ1 of the first stage nozzle aperture section 33 and the aperture angle θ2 of the second stage nozzle aperture section 35 are the following formulas (1) and (2), respectively. It can be calculated with

θ1 = tan ⁻¹ ((D1−D2) / 2 / L1) (1)
θ2 = tan ⁻¹ ((D3−D4) / 2 / L2) (2)
In the nozzle 31a of the jet pump 1 of the present embodiment, the nozzle throttle angles θ1 and θ2 of the first stage nozzle throttle section 33 and the second stage nozzle throttle section 35 are the second stage close to the nozzle ejection section 40. The nozzle aperture angle θ2 of the first nozzle aperture section 35 is formed such that θ2> θ1 so that the angle is larger than the nozzle aperture angle θ1 of the first stage nozzle aperture section 33.

  Further, a nozzle lower end portion 36 is connected to the downstream side of the second stage nozzle restricting portion 35, and a nozzle outlet 40 for ejecting a driving fluid is formed at the tip of the nozzle lower end portion 36.

  As the nozzle lower end portion 36, the nozzle straight pipe portion having an inner diameter D5 having the same diameter as the inner diameter D4 having a constant flow path diameter, or the inner diameter D4 having a gradually reduced flow path diameter slightly decreases toward the nozzle tip. It is formed by the nozzle stop.

  As the nozzle lower end portion 36, it is desirable to use a nozzle straight pipe portion in which a nozzle ejection port 40 for ejecting a driving fluid at the tip is formed with an inner diameter D5 having a constant flow path diameter. In order to improve the flow velocity of the jet of the driving fluid to be ejected, instead of the nozzle straight pipe portion, a nozzle throttle portion in which the flow path diameter is gently throttled and the inner diameter D4 slightly decreases toward the nozzle outlet 40 at the nozzle tip is used. May be.

  In the case where the nozzle restricting portion whose flow path diameter is gently restricted is used as the nozzle lower end portion 36, this nozzle is used to suppress the spread of the driving fluid ejected from the ejection port 40 of the nozzle lower end portion 36 within a desired range. It is desirable to form the nozzle aperture angle θ of the aperture at a small angle of less than about 2 degrees.

  In the nozzle 31a of the jet pump 1 of the present embodiment having the configuration shown in FIG. 5, the driving fluid 10 that has flowed into the nozzle 31a via the riser pipe 13 and the vent pipe 14 shown in FIG. The first stage in which the nozzle inner diameter decreases from D1 to D2 is located downstream of the nozzle straight pipe portion 32 and flows through the nozzle straight pipe portion 32 having the nozzle inner diameter D1 on the most upstream side constituting 31a. It is gradually accelerated by flowing down the nozzle restricting portion 33.

  Thereafter, the driving fluid 10 flows through the nozzle straight pipe portion 34 having the nozzle inner diameter D3 located on the downstream side of the nozzle throttling portion 33, and further located on the downstream side of the nozzle straight pipe portion 34 to change the nozzle inner diameter from D3 to D4. Accelerates by flowing down the second stage nozzle restricting portion 35 having a large restricting angle θ2 that decreases to a minimum.

  The aperture angle θ2 of the second stage nozzle aperture section 35 is configured to have an aperture angle larger than the aperture angle θ1 of the upstream first stage nozzle aperture section 33.

  The driving fluid 10 accelerated by flowing down the nozzle throttle 35 is located downstream of the nozzle throttle 35 and has a nozzle straight pipe having a nozzle inner diameter D5 or a nozzle throttle having a nozzle inner diameter gradually reduced from D5. Is ejected as a jet 21 directed toward the throat 17 on the downstream side from a nozzle jet port 40 provided at the tip of the nozzle lower end portion 36 formed in the above.

  The driving fluid 10 is given a velocity component toward the central axis of the nozzle 31a by the second stage nozzle throttling portion 35. However, since the fluid flows along the wall surface, the nozzle straight pipe is disposed downstream of the nozzle throttling portion 35. By providing the nozzle lower end portion 36 formed from a part or a gently throttled nozzle restricting portion, the nozzle is ejected with a diameter D5 from the nozzle outlet 40 formed at the tip of the nozzle lower end portion 36.

  At this time, since the momentum toward the nozzle central axis remains as the throttle angle θ2 of the second stage nozzle throttle portion 35 increases, the spread of the jet 21a ejected from the nozzle outlet 40 of the nozzle lower end portion 36 is suppressed, The diameter D6 of the jet flow 21a when proceeding downstream from the nozzle jet port L3 can be suppressed within a desired range and can be formed small.

  The diameter D6 of the jet 21a is the flow path width of the jet 21, and the smaller the diameter D6 of the jet 21, the higher the speed of the jet 21.

  When the driving fluid flows from the nozzle 31a into the throat 17 while maintaining the speed while suppressing the spread of the jet 21a, the static pressure inside the throat 17 is further lowered, so that the surrounding driven fluid from the bell mouth 16 above the throat 17 decreases. 22 can be sucked into the throat 17 more.

  If the nozzle lower end portion 36 is not installed on the downstream side of the nozzle restricting portion 35, the jet 21 is moved by the momentum of the driving fluid toward the central axis of the nozzle 31a given by the second stage nozzle restricting portion 35. The diameter becomes smaller after ejection.

  In other words, the diameter D6 of the jet 21 at a distance L3 from the nozzle outlet 40 is desirably smaller than the diameter D5 of the nozzle lower end 36 formed from the nozzle straight pipe portion having the diameter D4 = D5, and the jet velocity is increased. Since the acceleration loss increases, the flow rate of the driving fluid decreases.

  For this reason, the nozzle lower end portion 36 is installed on the downstream side of the nozzle restricting portion 35 so that the diameter of the jet 21a ejected from the nozzle ejection port 40 does not become less than the diameter D5 forming the nozzle straight pipe portion, thereby increasing the acceleration loss. This prevents a decrease in the flow rate of the driving fluid.

  The nozzle lower end portion 36 may be formed of a nozzle throttle portion having a narrower angle than the nozzle throttle portion 35 instead of the nozzle straight pipe portion as described above so that an increase in acceleration loss can be ignored.

  Further, when two or more nozzle throttling portions are provided in the nozzle 31a, the flow path of the driven fluid can be widened while suppressing the pressure loss of the nozzle 31a.

  Next, suppose that the inner diameter of the nozzle outlet 40 is fixed at D5, the inner diameter of D2 is D1 = D2, the nozzle restricting portion 33 is a straight pipe, and the nozzle restricting portion is one place of the nozzle restricting portion 35. .

  When the length L2 of the nozzle restricting portion 35 is not changed, the flow path between the nozzle straight pipe portion 32 and the nozzle restricting portion 33 is narrowed and the flow velocity of the driving fluid 10 flowing inside increases, so that the friction loss increases and the driving is performed. The flow rate of the fluid 10 decreases.

  Further, when the length L2 of the nozzle restricting portion 35 is increased to increase the flow path area upstream of the nozzle restricting portion 35, the outer diameter of the nozzle 31a is increased, and the object formed between the plurality of nozzles 31a is increased. Since the flow passage area of the driving fluid 22 is narrowed, the suction amount of the driven fluid 22 is reduced.

  Therefore, by providing the nozzle 31a with two or more nozzle restricting portions like the nozzle 31a of the jet pump 1 of the present embodiment, the flow path in the nozzle 31a becomes narrow and the flow velocity of the driving fluid 10 flowing inside increases. Thus, it is possible to secure the area of the driven fluid 22 to be sucked by reducing the area where the friction loss increases and reducing the area where the outer diameter of the nozzle 31a is large.

  According to the jet pump 1 of the present embodiment, as shown in FIG. 1, the driving fluid 10 that has flowed into the nozzle pedestal 20 is accelerated through the nozzle 31 a and is jetted to the throat 17 as a jet 21 a.

  As described above, since the spread of the jet 21a can be suppressed, the speed of the jet 21a reaching the throat 17 is increased and the static pressure in the throat 17 is further reduced. As a result, the driven fluid 22 is caused to flow by the throat 17. I can inhale a lot.

  Compared with the nozzle of the jet pump having the conventional structure consisting of the throttle part and the straight pipe part throttled in one stage, the nozzle 31a of the jet pump 1 of the present embodiment is detailed using the embodiment shown in FIG. As described above, by providing two throttle parts, the pressure loss in the nozzle 31a is equivalent to a nozzle having a throttle part that is throttled in one step, and the driven fluid formed between the nozzles It is possible to minimize the reduction of the flow path area.

  FIG. 6 shows the M ratio and the jet pump efficiency, which are the pump characteristics of the jet pump 1 of the present invention shown by the solid line obtained in the experiment, and the throttle part that is throttled by one stage of the conventional example shown by the broken line. It is shown with that of the pump characteristic of the jet pump provided with the nozzle which consists of a straight pipe part.

  In the jet pump 1 of the present embodiment, the flow rate of the driven fluid that can be sucked into the drive fluid of the same flow rate can be increased by the effect of the nozzle 31a having the above-described configuration, and therefore, as shown by the solid line in FIG. In addition to the fact that the pump characteristics of the jet pump are shifted to a higher M ratio, the peak jet pump efficiency is also improved.

  The above-described jet pump of the present embodiment includes a nozzle 31a that ejects driving fluid, a bell mouth 16 that is a suction port for surrounding driven fluid, a throat 17 that mixes the driving fluid and the driven fluid, and the driving fluid. And a diffuser 18 that increases the pressure of the mixed fluid of the driven fluid and discharges it, and a plurality of nozzles 31a are concentrically arranged at equal intervals on a nozzle base 20 to which the nozzles are attached, Each nozzle 31a includes nozzle straight pipe portions 32, 34, and 36 and nozzle restricting portions 33 and 35 each having a restricted flow path, and a plurality of the nozzle restricting portions 33 and 35 are provided. The nozzle aperture angle θ2 of the nozzle aperture portion 35 close to the nozzle outlet port 40 of the other nozzle aperture portion is shaped to be larger than the nozzle aperture angle θ1 of the other nozzle aperture portions 33. It is made.

  By increasing the throttle angle θ2 of the nozzle throttle portion 35, the expansion after the drive fluid is ejected is suppressed to suppress the speed reduction of the drive fluid at the inlet of the throat 17, and downstream of the nozzle throttle portion 35. The nozzle lower end portion 36 that forms the nozzle straight pipe portion having the nozzle jet port 40 at the lower end or the nozzle restricting portion in which the flow path is gently restricted is provided on the side. The pressure loss is prevented from increasing significantly.

  Since the speed of the driving fluid at the throat 17 is maintained, the static pressure inside the throat 17 is further reduced, the suction amount of the driven fluid is increased, and the M ratio and efficiency of the jet pump can be improved. .

  As is apparent from the above description, according to the jet pump of the present embodiment, the flow rate ratio (M) of the jet pump is reduced by suppressing the speed reduction of the driving fluid at the throat inlet and increasing the suction amount of the driven fluid. Ratio) and jet pump efficiency can be realized.

  A jet pump 1 which is another embodiment to which the present invention is installed installed in a boiling water reactor will be described with reference to FIGS.

  The jet pump 1 of the present embodiment has the same basic configuration as the jet pump 1 of the previous embodiment shown in FIGS. 1 and 3 to 6, and therefore the description of the common configuration is omitted. Only the differences will be described.

  In the jet pump 1 of the present embodiment shown in FIGS. 7 and 8, the nozzles constituting the jet pump 1 are provided with two types of long nozzles 31a and short nozzles 31b having different nozzle lengths. A total of six 31 a and three short nozzles 31 b are arranged alternately at equal intervals in a concentric manner.

  Further, the difference between the tip positions of the nozzles at the lower ends of the long nozzle 31a and the short nozzle 31b, which are nozzles constituting the jet pump 1 of the present embodiment, is x.

  Of the first-stage nozzle throttling portion 33b and the second-stage nozzle throttling portion 35b of the short nozzle 31b, the nozzle throttling angle θ2b in the second-stage nozzle throttling portion 35b near the nozzle ejection portion 40b is Θ2b> θ1b is formed so as to be larger than the nozzle aperture angle θ1b in the first stage nozzle aperture 33b.

  Similarly, the nozzle aperture angle θ2a in the second-stage nozzle aperture 35a located near the nozzle ejection portion 40a out of the first-stage nozzle aperture 33a and the second-stage nozzle aperture 35a of the long nozzle 31a is , Θ2a> θ1a is formed so as to be larger than the nozzle aperture angle θ1a in the first stage nozzle aperture 33a.

  Further, the nozzle aperture angle θ2a in the second stage nozzle aperture 35a of the long nozzle 31a constituting the nozzle installed in the jet pump 1 of the present embodiment and the second stage nozzle aperture 35b of the short nozzle 31b. At the nozzle aperture angle θ2b, θ2b is set such that the nozzle aperture angle θ2b at the second stage nozzle aperture 35b of the short nozzle 31b is larger than the nozzle aperture angle θ2a at the second stage nozzle aperture 35a of the long nozzle 31a. > Θ2a.

  Further, a lower end of the nozzle is provided on the downstream side of the second stage nozzle throttling part 35a of the long nozzle 31a and the second stage nozzle throttling part 35b of the short nozzle 31b constituting the nozzle installed in the jet pump 1 of the present embodiment. 36a and 36b are connected to each other, and nozzle ejection ports 40a and 40b for ejecting driving fluid are formed at the tips of the nozzle lower end portions 36a and 36b, respectively.

  As the nozzle lower end portion 36, the nozzle straight pipe portion having an inner diameter D5 having the same diameter as the inner diameter D4 having a constant flow path diameter, or the inner diameter with a gradually narrowed flow path diameter slightly decreases toward the nozzle tip. It is formed by the nozzle stop.

  For these nozzle lower end portions 36a and 36b, it is desirable to use nozzle straight pipe portions in which nozzle diameters 40a and 40b having a constant flow path diameter and ejecting driving fluid at the tip are formed. In order to improve the flow velocity of the jet flow of the driving fluid ejected from the lower end portions 36a and 36b, the diameter of the flow path is gradually reduced instead of the nozzle straight pipe portion, and the inner diameter is slightly increased toward the nozzle outlets 40a and 40b at the nozzle tip. A decreasing nozzle aperture may be used.

  In the case of using a nozzle restricting portion whose flow path diameter is gradually reduced for the nozzle lower end portions 36a and 36b, the spread of the driving fluid ejected from the outlets 40a and 40b of the nozzle lower end portions 36a and 36b is within a desired range. In order to suppress this, it is desirable to form the nozzle aperture angle θ of the nozzle aperture portion at a small angle of less than about 2 degrees.

  In the jet pump configured as described above, the driving fluid 10 that has flowed into the nozzle pedestal 20 is accelerated through a plurality of long nozzles 31a and short nozzles 31b, and is jetted into the throat 17 as a jet 21a and a jet 21b. The

  Since the increase and decrease in pressure loss due to the difference between the nozzle throttle angles θ2a and θ2b and the nozzle lengths at the nozzle throttle portions 35a and 35b installed in the long nozzle 31a and the short nozzle 31b are negligible, they flow into the nozzle base 20. The driving fluid 10 flows through the six nozzles (the three long nozzles 31a and the three short nozzles 31b) with a flow distribution almost evenly.

  The driven fluid 22 sucked into the throat 17 from the bell mouth 16 by the jet 21a and the jet 21b ejected from the long nozzle 31a and the short nozzle 31b into the throat 17 is first of the driving fluid 10 ejected from the short nozzle 31b. It is accelerated by the jet flow 21b having a half flow rate.

  The driven fluid 22 accelerated by the jet 21b ejected from the short nozzle 31b is further accelerated by the jet 21a ejected from the long nozzle 31a at a distance x.

  Thus, when the driven fluid 22 is accelerated in two stages, the driven fluid 22 can be accelerated more smoothly than when the driven fluid 10 is accelerated at the full flow rate at one time.

  Further, since the flow path area of the driven fluid 22 is increased by the distance x, the driven fluid 22 is easily sucked into the throat 17 and the M ratio and the jet pump efficiency are improved.

  Also in the jet pump 1 of this embodiment, although detailed explanation is omitted, the pump characteristics similar to the M ratio and the jet pump efficiency which are the pump characteristics of the jet pump 1 of the present invention shown by the solid line in FIG. 6 can be obtained. it can.

  Further, in the jet pump 1 of the present embodiment, the flow rate of the driven fluid that can be sucked into the driving fluid having the same flow rate can be increased by the effect of the nozzle 31a having the above-described configuration. In addition to the fact that the pump characteristics of the jet pump are shifted to a higher M ratio, the peak jet pump efficiency is also improved.

  By the way, since the jet 21b ejected from the short nozzle 31b exchanges momentum with the driven fluid 22 earlier than the jet 21a by the distance x, the nozzle restricting portion 35a of the long nozzle 31a and the nozzle of the short nozzle 31b. If the nozzle throttle angles θ2a and θ2b of the throttle portion 35b are set to be the same, when the jet velocity is compared at the same position inside the throat 17, the velocity of the jet 21b becomes smaller.

  However, in the jet pump 1 of the present embodiment, the nozzle throttle angle θ2b in the nozzle throttle portion 35b that is directly above the nozzle ejection portion 40b of the short nozzle 31b is set to the nozzle throttle portion that is directly above the nozzle ejection portion 40a of the long nozzle 31a. Since θ2b> θ2a is formed so as to be larger than the nozzle aperture angle θ2a at 35a, the divergence angle of the jet 21b is smaller than the divergence angle of the jet 21a.

  In particular, if the nozzle throttle angles θ2a and θ2b are adjusted so that the velocity of the jet 21a and the velocity of the jet 21b is the same at the same height inside the throat 17, the jet velocity unbalance at the throat 17 is eliminated and energy loss occurs. Since it can be reduced, the jet pump efficiency is improved.

  In the jet pump of this embodiment, the number of nozzles is an even number, the nozzles are arranged at equal intervals on a concentric circle of the nozzle base, the nozzle lengths are two types, and the short nozzles 31b and the long nozzles 31a are alternately arranged. .

  The driven fluid is accelerated to the first stage by the jet from the short nozzle 31b and then accelerated to the second stage by the long nozzle 31a.

  By accelerating in two stages in this way, the driven fluid can be accelerated smoothly, so that the pressure loss can be reduced, and the suction area of the driven fluid is increased, so that the M ratio and efficiency of the jet pump are improved. be able to.

  Further, in the jet pump of the present embodiment, the narrowing angle θ2b of the nozzle throttle portion 35b located immediately above the nozzle jet port 40b of the short nozzle 31b is equal to that of the nozzle throttle portion 35a located just above the nozzle jet port 40a of the long slur 31a. The angle is formed larger than the aperture angle θ2a.

  By forming the nozzle aperture angle θ2b of the nozzle aperture 35a immediately above the nozzle jet port 40b of the short nozzle 31b to be larger than the nozzle aperture angle θ2a of the nozzle aperture 35b just above the nozzle jet port 40a of the long nozzle 31a, The speed difference between the long nozzle 31a and the short nozzle 31b at the inlet of the throat 17 due to the distance between the nozzle tip and the inlet of the throat 17 being longer than that of the long nozzle 31a is reduced, and the target is stably covered. The M ratio and efficiency of the jet pump can be improved by sucking the driving fluid.

  As is apparent from the above description, according to the jet pump of the present embodiment, the flow rate ratio (M) of the jet pump is reduced by suppressing the speed reduction of the driving fluid at the throat inlet and increasing the suction amount of the driven fluid. Ratio) and jet pump efficiency can be realized.

  The present invention is applicable to a jet pump installed in a pressure vessel of a boiling water reactor.

The fragmentary sectional view which expands and shows the nozzle of the jet pump which is one Example of this invention. 1 is a cross-sectional view showing a schematic structure of a boiling water reactor in which a jet pump according to the present invention is installed. The perspective view which shows the whole structure of the jet pump which is the Example of this invention installed in the boiling water reactor. The horizontal cross-section arrangement | positioning figure of the nozzle which shows the condition which installed the nozzle of the jet pump which is the Example of this invention shown in FIG. Sectional drawing which shows the detailed structure of the nozzle of the jet pump which is an Example of this invention shown in FIG. The characteristic view which showed the performance of the jet pump which is an Example of this invention with the comparative example. The fragmentary sectional view which expands and shows the nozzle of the jet pump which is another Example of this invention. The horizontal cross-section arrangement | positioning figure of the nozzle which shows the condition which installed the nozzle of the jet pump which is another Example of this invention shown in FIG.

Explanation of symbols

  1: jet pump, 2: shroud, 3: pressure vessel, 4: downcomer, 5: reactor core, 6: steam separator, 7: steam dryer, 8: main steam pipe, 9: water supply pipe, 10: driving fluid 11: Recirculation system pipe, 12: Recirculation pump, 13: Riser pipe, 14: Vent pipe, 31a, 31b: Nozzle, 16: Bell mouth, 17: Throat, 18: Diffuser, 20: Nozzle base, 21a, 21b: Jet, 22: Driven fluid, 32, 32a, 32b, 34, 34a, 34b: Nozzle straight pipe part, 33, 33a, 33b, 35, 35a, 35b: Nozzle restriction part, 36, 36a, 36b: Nozzle Lower end part, 40, 40a, 40b: Nozzle spout.

Claims (4)

  A riser pipe that guides the driving fluid to the nozzle, a vent pipe that is installed downstream of the riser pipe and redirects the flow of the driving fluid guided from the riser pipe, and a vent pipe installed downstream of the vent pipe A nozzle that ejects the redirected driving fluid, a bell mouth that is a suction port for the surrounding driven fluid, a driven fluid that is installed downstream of the bell mouth and sucked from the bell mouth, and is jetted from the nozzle In a jet pump having a throat that mixes the drive fluid and a diffuser that is installed downstream of the throat and discharges the mixed fluid by increasing the pressure of the mixed fluid, a plurality of nozzles are provided on a nozzle base to which the nozzle is attached. Concentrically arranged, each nozzle has a straight nozzle section with a constant flow path diameter, and a nozzle throttle section with a narrow flow path diameter downstream of the nozzle straight pipe section, A plurality of the nozzle orifices are formed such that the nozzle orifice angle of the nozzle orifice portion close to the nozzle orifice among the nozzle orifice portions is larger than the nozzle orifice angle of the other nozzle orifice portions, and further close to the nozzle orifice portion. A jet pump characterized in that a nozzle lower end portion having a nozzle outlet at a tip thereof and having a fixed or gently narrowed passage diameter is provided downstream of the nozzle restricting portion.   2. The jet pump according to claim 1, wherein the nozzles are arranged at even intervals in a concentric manner on a nozzle base, and the short nozzles having a short length and the long nozzles having a long length are alternately positioned in the nozzle. A jet pump characterized by being arranged as described above.   3. The jet pump according to claim 2, wherein a nozzle throttle angle of a nozzle throttle portion near a nozzle jet port portion of a short nozzle provided in the nozzle is larger than a nozzle throttle angle of a nozzle throttle portion near a nozzle jet port of a long nozzle. A jet pump characterized by being formed to be large.   A boiling water reactor using the jet pump according to any one of claims 1 to 3.

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