JPS5815798A - Jet pump - Google Patents

Abstract

PURPOSE:To make it possible to reduce the leak of a fluid from a slip joint portion by providing the slip joint on a throat portion. CONSTITUTION:Driving water from a recirculating pump rises a riser tube 11, bursts forth from a nozzle 12, and absorbs surrounding water allowing to be mixed at a throat 13. Thereafter, the pressure of said driving water is restored at a diffuser portion 14, and flows into a lower plenum 8. Here the throat 13 has been divided into two members (13a and 13b) on the way, and a slip joint 18 is provided on their divided portions. And providing the slip joint on the throat portion 13 where the pressure witin a jet pump has not been restored causes the abrupt reduction of the leaked flow rate of the fluid.

Description

[Detailed description of the invention] The present invention relates to improvements in jet pumps.

The internal structure of a device equipped with a jet pump will be explained based on FIG. 1, taking the case of a boiling water reactor as an example.

In FIG. 1, steam generated in a reactor core 2 is separated into steam and water by a separator 3, and then converted into superheated steam by a dryer 4.
The turbine is driven through the main steam system 5. Separator 3
The water separated into steam and water is mixed with the water supplied from the water supply system 7 in the downcomer 6, and is supplied to the reactor core 2 via the jet pump 9, passing through the lower blennium 8. jet pump 9
The water in the downcomer 6 is sucked in by the water driven by the recirculation pump 10. When the jet pump 9 is installed in the pressure vessel 1 in this way, the amount of water drawn out of the pressure vessel 1 (the flow rate of the recirculation pump 10) can be reduced.

Here, the internal structure of the conventional jet pump will be explained based on FIGS. 2 and 3. In FIG. 2, the driving water from the recirculation pump rises up the riser pipe 11 and is ejected from the nozzle 12.

The driving water ejected from the nozzle 12 sucks water in the downcomer 6, is mixed at the throat 13, and then flows into the lower plenum 8 through the diffuser 14. The diffuser 14 converts dynamic pressure into static pressure and increases the head of the jet pump. The riser pipe 11 is connected to the riser place 15
The throat 13 is fixed to the riser pipe 11 via a restrainer 16.

The nozzle 12 and the throat 13 are welded together so that their central axes coincide with each other with high precision.

Further, the diffuser 14 includes the jet pump support 1
It is fixed at 7. Therefore, a so-called slip joint 1B is provided between the throat 13 and the diffuser 14, as shown in FIG. 3, to absorb the difference in thermal expansion between the riser pipe 11 and the diffuser 14.

FIG. 4 is a diagram showing the internal and external pressure distribution characteristics of the jet pump shown in FIG. 2. The pressure PD of the driving water ejected from the nozzle 12 drops rapidly, and at the inlet of the throat 13 water is sucked from the downcomer at a pressure lower than the downcomer pressure Poc. The driving water and the suction water gradually increase in pressure while being mixed through the throat, and the pressure is further recovered at the widening portion of the diffuser 14. At the slip joint 18, the pressure PJ in the jet pump is higher than the pressure Pnc in the downcomer, and leakage occurs from the jet pump to the downcomer. The performance of a jet pump is generally expressed by the M ratio, which indicates the ratio between the total flow rate Wx and the driving water flow rate WD.

The total flow rate WJ of the jet pump is the sum of the driving water flow rate WD and the suction water flow rate Ws minus the leakage flow rate WL at the slip joint of 18 m, so it becomes as follows. In other words, reducing the leakage flow rate WL from the slip joint 18 improves the performance of the jet pump. As shown in FIG.
DC) and reaches 2-3% of the jet pump total flow rate WJ during normal operation.

In this way, conventionally used jet pumps have a slip joint between the throat and the diffuser for the purpose of absorbing the difference in thermal expansion between the riser pipe and the diffuser. There was a steep point where 2-3% of the flow rate leaked from the slip joint.

The present invention has been made in consideration of the above points, and includes:
The purpose is to provide a high-performance jet pump that solves the problem of fluid leakage from the slip joint.

In order to achieve the above object, the present invention provides a jet pump comprising a nozzle for ejecting a driving fluid, a throat for mixing the driving fluid and a suction fluid, and a diffuser for converting dynamic pressure into static pressure. It is characterized by a slip joint provided in the throat portion.

Hereinafter, the present invention will be explained in detail based on an embodiment shown in FIGS. 6 and 7. In these figures, the same reference numerals as in FIGS. 2 and 3 indicate the same parts.

In FIG. 6, driving water from the recirculation pump ascends up the riser pipe 11 and is ejected from the nozzle 12, sucks in surrounding water, and is mixed at the throat 13.

Thereafter, the pressure is restored at the diffuser 14 and flows into the lower plenum 8. As shown in FIG. 7, the throat 13 has two members (13a and 1) in the middle.
3b), and a slip joint 18 is provided in the divided portion. The riser pipe 11 is fixed to the pressure vessel via a riser place 15, and the throat 13a above the slider insert 18 is fixed to the riser pipe 11 via a restrainer 16.

The diffuser 14 is fixed to the jet pump support 17 and is connected to the throat 13b below the slip joint 18.
is fixed to the restrainer 19. Note that the restrainer 19 is not fixed to the riser pipe 11.

The present invention has the above-mentioned configuration, and its gist is that the slip joint 18 is provided in the throat 13 portion.Next, the effects obtained by the present invention will be explained based on FIG. As mentioned above, in the conventional jet pump in which the slip joint 18 is provided between the throat 13 and the diffuser 14, 2 to 3% of the jet pump total flow rate WJ leaks. If a slip joint is provided in the throat 13 portion where the pressure within the jet pump has not recovered as in the invention, the leakage flow rate of the fluid decreases rapidly, as is clear from the characteristic diagram in Figure 'a8.

especially,! The next region shown in Figure 4 is a region where the pressure PJ in the jet pump is lower than the downcomer pressure Pnc (
When a slip joint is provided in PJ PDC < 0), external fluid is sucked into the jet pump from the slip joint, so the total flow rate of the jet pump increases by approximately 4% compared to a conventional jet pump. It was confirmed that In addition, since the slip joint is provided approximately at the center of the throat 13, the difference in pressure between the inside and outside of the slip joint can be brought close to zero, so the amount of leakage of the fluid flowing inside the jet pump is also approximately zero. .

As shown in Fig. 9, if a slip joint 18 is provided in the throat 13 along the flow of the fluid, the flow inside the throat 13 is stabilized by the suction flow from the slip joint 18, and the flow vibration is reduced. can be achieved.

As described in detail above, according to the present invention, it is possible to provide a high-performance jet pump in which the problem of fluid leakage from the slip joint portion is improved.

[Brief explanation of drawings]

Figure 1 is a schematic structural explanatory diagram of a boiling water reactor, Figure 2 is a partial longitudinal sectional view of a conventional jet pump installed in the pressure vessel of a boiling water reactor, and Figure 3 is a Figure 4 is an enlarged view of part A (slip joint part) in the figure.
Fig. 5 is a diagram showing the internal and external pressure distribution characteristics of the jet pump shown in Fig. The figure is a partial vertical sectional view of a jet pump showing an embodiment of the present invention, FIG. 7 is an enlarged view of part 8 (slip joint part) of FIG. 6, and FIG. FIG. 9 is a longitudinal cross-sectional view of a main part showing another embodiment of the present invention. 9... Jet pump, 12... Nozzle, 13...
・Slow), 14... Diffuser, 18... Slip Jo (and 1 other person) 1st figure to B 2nd mouth FI! , 4 diagrams ``techniques'', 7 too de nfu phlegm, how n kui t'11shi
Otsu C4 Mata Ribjo 4 nt sending down i'l (,L/1-th)
Skin 9 Figure 3

Claims (1)

[Claims] 1. A jet pump comprising a nozzle for ejecting a driving fluid, a throat for mixing the driving fluid and the suction fluid, and a diffuser for converting dynamic pressure into static pressure, in which the throat portion A jet pump characterized by being equipped with a slip joint. 2. The jet pump according to claim 1, wherein the throat is provided with a slipper at a portion where the internal pressure is negative. The jet pump according to claim 1, wherein a slip joint is provided approximately at the center of the λ throat.