CN106640740B - The Double End fluid dynamic and static pressure mechanical seal of sodium-cooled fast reactor core main pump - Google Patents

Abstract

The present invention proposes a double-end fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump to solve the problem of leakage of circulating working medium in the existing sodium pump and possible leakage of blocking fluid lubricating oil into the pump to pollute the working medium problem, to ensure the safe and stable long-term operation of the fast reactor. It is composed of a moving ring, a static ring forming a self-pumping fluid sealing structure with both ends of the moving ring, a spring, a sealing shell, etc.; the moving ring cooperates with the pins on the shaft sleeve to realize the circumferential and axial positioning of the moving ring; The set screw is set on the shaft sleeve; the limiter is detachably set between the sealing shell or the spring seat and the shaft sleeve to limit the axial relative position of the shaft sleeve and the spring seat, and change the spring force so that the moving ring and the two The pressure between the static rings is the same; when the moving ring rotates, the blocking fluid filled in the outer sealing space surrounded by the moving ring and the sealing shell flows into the end surface of the moving ring through the axial and radial combined channels under the action of the pressure difference. In the back-curved fluid-type tank, a self-pumping cycle is formed again and again.

Description

Double-end fluid dynamic and static pressure mechanical seal for sodium-cooled fast reactor nuclear main pump

technical field

The invention belongs to the technical field of sealing, and in particular relates to a self-pumping mechanical seal with hydrodynamic and static pressure effects, which is suitable for sealing between a sodium-cooled fast reactor nuclear main pump casing and a pump shaft.

Background technique

Nuclear power is ushering in a new round of rapid development worldwide. From the late 1950s to the early 1960s, since the first batch of prototype nuclear power plants were built in the world, the development of nuclear power technology has gone through the first and second generations, and is currently moving towards the third and fourth generations. There are many types of nuclear power plant reactors, which can be divided into light water reactors (including pressurized water reactors and boiling water reactors), heavy water reactors, graphite gas-cooled reactors, and fast breeder reactors. According to the thermal system, there are three types of nuclear power plants: single-circuit, double-circuit and three-circuit systems. In a single-loop system, the working fluid directly enters the steam turbine or gas turbine from the reactor, such as boiling water reactors and high-temperature gas-cooled reactors that use helium turbine direct circulation; The working fluid in the circuit generates steam, and then drives the steam turbine to do work. The pressurized water reactor and the high-temperature gas-cooled reactor using the steam turbine circulation method belong to this type; the three-circuit system is more complicated, and the main reactor type is the fast breeder reactor. No matter what kind of thermal system and reactor type, coolant is needed to take out the heat generated by nuclear fission in the core to cool the core and carry out the subsequent power generation process. This cooling circuit is the primary circuit system, which is the core system of the nuclear power plant reactor.

The coolant circulating in the primary loop system of the reactor often has the characteristics of high temperature, high pressure, and strong radioactivity, and the leakage of the coolant must be strictly controlled. Since there are rotating equipment such as pumps/fans/compressors/steam turbines/gas turbines in the primary loop circulation system, in order to solve the coolant sealing problem caused by them, there are usually two solutions in engineering: one is to use shaft seal equipment, that is, High-reliability nuclear-grade mechanical seal; the second is to place the driving motor of the pump and other equipment in the pressure shell of the primary circuit as a whole, so that the dynamic seal with leakage risk is converted into a static seal with zero leakage, and the external auxiliary system is greatly simplified , but this scheme transfers the technical difficulties to equipment or components such as motors and bearings. For example, for pressurized water reactors, the coolant pump (nuclear main pump) motor must be shielded or wet stator, and the main pump bearings must all use water-lubricated bearings; for high-temperature gas-cooled reactors with steam turbine cycles, helium The main shaft bearing of the fan needs to use oil-free bearings such as electromagnetic bearings. Due to the high technical difficulty and high manufacturing cost of this type of motor and bearing, especially under the conditions of high power and large size, the problems of work efficiency and reliability are difficult to solve, so the primary circuit system using mechanical seals still occupies a dominant position. .

As the fourth-generation reactor, the fast reactor is the fast neutron breeder reactor, which directly uses the fast neutrons produced by fission to trigger the nuclear fission chain reaction without moderator, and can multiply nuclear fuel, make full use of uranium resources, and greatly reduce nuclear waste medium and long-lived nuclides. Fast reactor coolants need to have good heat transfer performance and will not moderate neutrons. At present, they are mainly liquid metal and helium. The primary circuit system of sodium-cooled fast reactor consists of core, main pump (primary sodium pump), heat exchanger, main pipeline and other parts. The difference from the mechanical seals of other reactor primary circuit main circulation pumps is that the working condition of the mechanical seal of the sodium-cooled fast reactor nuclear main pump is low pressure (571kPa) and low temperature (70°C), which is conducive to the realization of the seal. However, due to the strong activity of sodium, it will explode when it meets water or air. Therefore, the reliability of the sodium pump seal is high, and the design must strictly ensure zero leakage of liquid sodium. The export of heat from the core.

Figure 1 is a schematic diagram of the sodium pump in the primary circuit of the prototype sodium-cooled fast reactor (PFBR) (Wang Yuming, Huang Weifeng, Li Yongjian. Mechanical seals for primary circuits of nuclear power plants. Acta Tribology, 2011, 31(4): 408-416). The free liquid surface of liquid sodium in the casing of the sodium pump is filled with argon, and a mechanical seal is set at a certain height from the sodium liquid surface. This design form avoids direct contact between the seal and liquid sodium at a temperature as high as 400-500°C, and eliminates many harsh restrictions on materials and structures, making it possible to use conventional mechanical seal designs.

According to the existing technology, the sodium pump draws lessons from the third-stage seals of light water reactors (including pressurized water reactors and boiling water reactors), heavy water reactors, and graphite gas-cooled reactors, that is, double-end mechanical seals blocked by lubricating oil or dry gas plugged by gas Seal to achieve a seal. For double-end mechanical seals with lubricating oil blocking, the pressure of the blocking lubricating oil is usually kept higher than that of the working gas to prevent the protective argon from leaking into the blocking fluid, and it is installed on the shaft sleeve at the lower part of the mechanical seal on the working gas side The oil throwing ring is used to ensure that when the blocked lubricating oil with high pressure leaks into the pump chamber, it can flow into the liquid collecting barrel through the oil throwing ring and the liquid collecting hole without polluting the sodium liquid. For dry gas seals with gas blocking, the pressure of the blocking gas is usually kept higher than that of the working gas to prevent leakage of protective argon into the blocking gas.

However, when the dry gas seal with gas blocking is used, the auxiliary system needs to provide clean blocking gas to maintain the non-contact operation of the dry gas seal; at the same time, the blocking gas with a pressure higher than that of the working gas will leak in through the gap between the sealing end faces. Pump chamber, causing blocking gas loss and protective argon contamination and pressure rise. In particular, when the sealing end face is disengaged instantly under abnormal axial loads such as earthquakes, when a large amount of lubricating oil leaks into the oil throwing ring, the liquid collecting hole has no time to flow through, and it will flow into the pump cavity along the air channel to form sodium pollution. Serious threat to the safety of sodium-cooled fast reactor.

Contents of the invention

The purpose of the present invention is to propose a double-end surface fluid dynamic and static pressure self-pumping mechanical seal for the main pump of the sodium-cooled fast reactor nuclear pump, so as to solve the leakage of the circulating working medium in the existing sodium pump and the possible leakage of the blocking fluid lubricating oil into the pump. The problem of internal pollution of the working medium is ensured to ensure the safe and stable long-term operation of the fast reactor.

Technical scheme of the present invention is:

A double-end fluid dynamic and static pressure mechanical seal for a sodium-cooled fast reactor nuclear main pump is arranged between the casing of the sodium pump and the pump shaft 2, and consists of a moving ring 10, an O-ring 9 for the moving ring, and static rings 8 and 12 , O-ring 7, 13 for static ring, spring 6, 15, spring seat 5, 14, sealing shell 16, shaft sleeve 1, O-ring 17 for shaft sleeve, limiter 4, pin 11 and set screw 3, etc. composition,

The moving ring 10 and the static rings 8, 12 and spring seats 5, 14 on both sides of the moving ring 10 are all worn on the shaft sleeve 1; the moving ring 10 and the shaft sleeve 1 are sealed and connected with an O-ring 9; The end is the moving ring sealing end face, and each moving ring sealing end face is matched with a static ring, and the outer circular surfaces of the static rings 8 and 12 are connected with the sealing shell 16 with O-rings 7 and 13; the other end face of the static ring More than 3 springs are respectively supported, and the other end of the spring acts on the spring seat 5, 14, and the spring seat 5, 14 is connected to the sealing shell, so that a certain end face specific pressure is obtained between the end face of the moving ring seal and the end face of the static ring; The moving ring 10 cooperates with the pin 11 on the shaft sleeve through the radially closed and axially opened pin hole located at the lower part of the moving ring to realize the circumferential positioning of the moving ring 10 and keep the pin 11 in contact with the bottom of the pin hole while realizing the moving ring Axial positioning of 10; the set screw 3 set on the shaft sleeve is used to fix the relative position of the shaft sleeve 1 and the pump shaft 2; the limiter 4 is detachably set on the sealing shell 16 or the spring seat 5, 14 and the shaft Between the sleeves 1, it is used to define the axial relative position between the shaft sleeve 1 and the sealing shell 16 or the spring seat 5, 14, so as to change the elastic force of the spring supporting the two static rings, so that the sealing end faces at both ends of the moving ring are in contact with the two static rings. The pressure is the same between the rings;

The static ring is surrounded by O-rings 7, 13, the moving ring 10, and the sealing shell 16 to form an outer sealing space, and the outer sealing space is filled with blocking fluid;

The end face of the moving ring seal that cooperates with the static rings 8 and 12 is divided into a groove area and a seal dam 37, the groove area is distributed on the outer part of the end face, and the seal dam 37 is distributed on the inner part of the end face; more than 3 groups of back-curved types are provided in the groove area The fluid-type groove 39 and the sealing end surface between the back-curved fluid-type groove 39 form a sealing weir; the groove area and the sealing dam 37 on the sealing end surface of the moving ring at the upper and lower ends of the moving ring 10 are arranged symmetrically with the middle section M-M of the moving ring;

The back-curved fluid groove 39 includes two parts: a slope groove 32 and a flat groove 33. The slope groove 32 is located at the large radius portion of the end face of the moving ring, and the flat groove 33 is located at the small radius portion of the end face of the moving ring;

The outlet of the backward curved fluid groove 39 is located at the outer diameter of the moving ring sealing end face, the inlet 31 is located in the middle of the sealing surface of the moving ring 10, and the inlet 31 of the backward bending fluid groove 39 passes through the The axial-radial combination channel 30 communicates with the outer sealing space;

On both sides of the back-curved fluid groove 39, one side is the working surface 34, and the other side is the non-working surface 35;

The blocking fluid in the back-curved fluid-type groove 39 is accelerated into a high-speed fluid by the working surface of the backward-curved fluid-type groove 39 when the moving ring rotates, and flows toward the moving ring 10 along the non-working surface 35 under the centrifugal force. The outer diameter side flows and is pumped into the outer sealing space, and a low pressure area is formed at the inlet 31 of the back-curved fluid groove 39, and the blocking fluid in the outer sealing space passes through the moving ring 10 and the outer sealing space under the action of the pressure difference. The spatially connected axial and radial combination channels 30 flow into the back-curved fluid groove 39 to form self-pumping cycles again and again;

The blocked fluid that is accelerated into a high speed by the working surface 34 of the back-curved fluid-type groove 39 is pumped out of the back-curved fluid-type groove 39. As the pressure increases, the flow rate decreases and the pressure increases, forming an opening force that separates the moving ring 10 from the static rings 8 and 12.

The pin 11 is in contact with the bottom of the pin hole to realize the axial positioning of the moving ring 10, so that the weight of the moving ring is supported by the pin, and the weight of the moving ring will not be transferred to the lower static ring, and the upper spring supporting the upper static ring can also be guaranteed There is a certain amount of compression. If there is no pin for axial positioning of the moving ring 10, the lower spring supporting the lower static ring needs to bear the weight of two static rings and one moving ring, and the pressure between the sealing end faces at both ends of the moving ring and the two static rings is not will be the same. This repeated self-pumping cycle process, on the one hand, realizes the self-lubrication of the mechanical seal; The self-flushing of the seal is realized; the effect of centrifugal force increases the power of the fluid flowing to the outside of the sealing surface of the moving ring 10, and reduces the leakage rate of the fluid flowing to the inside of the sealing surface of the moving ring 10; The blocking fluid containing solid particles in the back-curved fluid-type groove 39 can cause the solid particles to separate from the matrix, wherein the solid particles with high density obtain greater centrifugal force, and are re-sent to the outer sealed space along with the fluid being pumped out. Does not enter the 37 area of the seal dam, avoiding abrasive wear between the sealing surfaces.

As a further improvement, the O-ring 17 for the shaft sleeve, the shaft sleeve 1, the lower static ring 12 and the O-ring 13 for the static ring, the moving ring 10, the casing of the sodium pump, and the working medium chamber surrounded by the pump shaft 2, The lower part of the working medium cavity is high-temperature metal sodium liquid, and the upper part is protective argon gas; the blocking fluid in the outer sealed space is also argon gas, and the pressure of the blocking fluid is not less than the pressure of the argon gas in the working medium cavity. Since the pressure of the blocking fluid is not less than the pressure of the argon in the working medium cavity, the argon in the working medium cavity will not leak into the outer sealed space through the sealing end face between the static ring and the moving ring. Even if the dynamic and static rings are disengaged instantaneously under the action of earthquake load, it is only possible that the blocking fluid leaks through the sealing end face between the static ring and the moving ring and enters the working medium cavity, but because the blocking fluid is the same as the upper medium in the working medium cavity , so even if the blocked fluid enters the working medium cavity, it will not affect the work of the nuclear main pump.

As a further improvement, the number and structure of the springs supporting the two static rings are the same, and the spring stiffness is K; the structure of the two static rings is the same, and the weight is GJ; The compression length △x1 of the spring of the static ring on the upper part of the moving ring satisfies: △x2-△x1=2GJ/K, so that the pressure between the sealing end faces at both ends of the moving ring and the two static rings is the same.

When the double-face fluid dynamic and static pressure mechanical seal described in this technology is working, the shaft sleeve is fixed on the pump shaft 2 through the set screw 3, and the moving ring is positioned axially and circumferentially on the shaft sleeve through the pin 11, so the dynamic The position of the ring relative to the pump shaft 2 is fixed.

Because the gravity of the static ring on the upper part of the moving ring stretches its spring, while the gravity of the static ring on the lower part of the moving ring compresses its spring, resulting in different pressures on the sealing end faces of the moving ring from the upper and lower static rings under the same spring compression, causing 2 The wear amount of each seal pair (the contact surface of the moving ring and the static ring) is different, resulting in a shortened life of the double-end seal. Therefore, it is necessary to adjust the elastic force (or compression length) of the upper and lower springs supporting the upper and lower static rings.

For the moving ring, it is subject to the pressure Y1 of the upper static ring, the pressure Y2 of the lower static ring, its own gravity GD, and the support force ZD of the pin; Y1+GD=Y2+ZD. If the pressure Y1 of the upper static ring on the moving ring is equal to the pressure Y2 of the lower static ring on the moving ring, then the supporting force ZD of the pin on the moving ring should be equal to the gravity GD of the moving ring.

For the upper static ring, Y1=K△x1+GJ; for the lower static ring, K△x1=Y2+GJ. If Y1=Y2, namely KΔx1+GJ=KΔx2-GJ, then Δx2-Δx1=2GJ/K.

The groove walls on both sides of the back-curved fluid groove 39 are helical.

The helixes of the groove walls on both sides of the back-curved fluid groove 39 have the same helix angle.

The helix angles of the helixes of the groove walls on both sides of the back-curved fluid groove 39 are different, and the helix angle of the working surface 34 is smaller than that of the non-working surface 35 .

The helix of the groove wall profiles on both sides of the back-curved fluid groove 39 is tangent to the round hole of the inlet 31 .

The cross-section of the joint between the axial and radial combined channels 30 on the moving ring 10 and the outer surface of the moving ring 10 is a wedge-shaped opening. In the above-mentioned double-face hydrodynamic and static pressure mechanical seal, the inlet 31 of the backward curved fluid groove 39 communicates with the outer sealing space through the axial and radial combination channels 30 on the moving ring 10; when the moving ring rotates, the outer The blocking fluid in the sealed space flows into the backward curved fluid groove 39 through the combined axial and radial channels 30 on the moving ring 10 communicating with the outer sealed space under the action of pressure difference, forming self-pumping cycles again and again.

As another technical solution of the present invention, the inlet 31 of the backward curved fluid groove 39 communicates with the circular ring groove 36 arranged in the middle of the sealing surface of the moving ring 10 or the static ring 8, 12, and the circular ring groove 36 communicates with the outer sealing space through the ring located on the moving ring or the static ring; when the moving ring rotates, the blocking fluid in the outer sealing space passes through the axial and radial combination channels on the static ring that communicate with the outer sealing space under the action of pressure difference 30. The circular ring groove 36 flows into the backward curved fluid groove 39 to form a self-pumping cycle again and again.

The circular ring groove 36 has the functions of collecting self-lubricating and self-flushing medium and preventing unevenness of the pumping medium and cavitation if the fluid replenishment at the inlet 31 of the backward curved fluid type groove 39 is not timely.

The grooves and seal dams 37 on the upper and lower ends of the moving ring 10 are symmetrically arranged on the middle section M-M of the moving ring, which also ensures that the two sealing pairs (the contact surface between the moving ring and the static ring) have the same structure, so that the two The wear amount of the sealing pair is the same, prolonging the service life. The middle section M-M of the moving ring refers to the cross section perpendicular to the axis of the moving ring, which divides the moving ring into equal parts in the axial direction.

Beneficial effects of the present invention.

A self-pumping hydrodynamic mechanical seal according to the present invention has the following advantages:

①It has excellent sealing performance and realizes zero leakage, and is suitable for the sealing of the nuclear main pump of sodium-cooled fast reactor. The O-ring 9 for the moving ring, the O-ring 7 and 13 for the static ring, and the O-ring 17 for the shaft sleeve prevent the leakage of argon in the working medium cavity; the pressure of the blocking fluid is not less than the pressure of the argon in the working medium cavity , coupled with the self-pumping cycle of the blocking fluid, effectively prevents the leakage at the sealing end face between the argon driven ring and the static ring in the working medium cavity.

② When the moving ring rotates, particles of different masses produce different centrifugal forces, so that the mechanical seal of the present invention has the function of automatically removing solid particles, which can avoid abrasive wear of the seal dam, and thus does not need to provide an additional auxiliary filtration system.

③Wide range of application, can be used as both gas seal and liquid seal.

④The unique self-lubricating, self-cooling and flushing functions ensure the stability and durability of the sealing work.

⑤ In the static state, the blocking fluid is directly injected between the sealing surfaces of the dynamic and static rings, which eliminates the solid friction between the sealing surfaces of the dynamic and static rings at the moment of starting, and quickly forms a fluid film at the moment of starting.

⑥Cartridge structure, quick and convenient assembly. Since the present invention has a detachable stopper 4, the product (sealed shell 16, moving ring 10, static ring 8, 12, spring seat 5, 14, shaft sleeve 1, pin 11, tightening Screws 3, etc.) are assembled to form a "cartridge" mechanical seal. During installation, put it on the pump shaft together, fix the spring seat 15 of the bottom with the casing of the sodium pump, screw the set screw 3 on the pump shaft, and then remove the stopper 4 to get final product.

Description of drawings

Figure 1 is a schematic diagram of the primary loop sodium pump of the prototype sodium-cooled fast reactor (PFBR).

Fig. 2 is a schematic diagram of the axial cross-sectional structure of a self-pumping hydrodynamic mechanical seal with back-curved fluid grooves and axial-radial combination channels provided on the moving ring before installation.

Fig. 3 is a schematic diagram of the axial cross-section structure of a self-pumping hydrodynamic mechanical seal with back-curved fluid-type grooves and axial-radial combination channels provided on the moving ring after installation.

Fig. 4 is a schematic diagram of the axial cross-sectional structure of a self-pumping hydrodynamic mechanical seal with back-curved fluid grooves on the moving ring and axial and radial combination channels on the static ring before installation. (The circular ring groove can be opened on the moving ring or on the static ring)

Fig. 5 is a schematic diagram of the axial cross-sectional structure of a self-pumping hydrodynamic mechanical seal with a back-curved fluid groove on the moving ring and an axial-radial combination channel on the static ring after installation. (The circular ring groove can be opened on the moving ring or on the static ring)

Fig. 6 is a schematic diagram of the end face of the moving ring provided with back-curved fluid-type grooves and axial and radial combination channels.

Fig. 7 is a schematic diagram of the end face of the moving ring with a back-curved fluid groove and a circular ring groove.

Fig. 8 is a schematic diagram of the end face of the static ring with axial and radial combined holes opening in cooperation with Fig. 7 .

Fig. 9 is a schematic diagram of the end face of the moving ring with a back-curved fluid groove.

Fig. 10 is a schematic diagram of the end face of the static ring with circular ring grooves and axial and radial combination channels matched with Fig. 9 .

in,

R1—the inner radius of the sealing end face between the moving ring and the static ring;

R2—the outer radius of the sealing end face between the moving ring and the static ring;

Rp—groove step radius

Ro—Radius of slot entrance hole position

Rk—the radius of the entrance hole of the groove

R3—Inner radius of the inlet ring groove of the groove

R4—outer radius of the inlet ring groove of the type groove

G—The pumping direction of the fluid groove

w—rotation of the moving ring

Shaft sleeve 1, pump shaft 2, set screw 3, limiter 4, spring seat 5, spring 6, O-ring for static ring 7, static ring 8, O-ring for moving ring 9, moving ring 10, pin 11. Static ring 12, O-ring for static ring 13, spring seat 14, spring 15, sealing shell 16, O-ring for shaft sleeve 17, axial and radial combination channel 30, inlet 31, slope groove 32, flat groove 33 , working surface 34, non-working surface 35, circular ring groove 36, seal dam 37, back-curved fluid groove 39, mechanical seal 40, thrust bearing 41, pump shaft 42, guide bearing 43, impeller 44, moving ring Middle section M-M.

Detailed ways

The implementation of the present invention will be described in detail below in conjunction with the accompanying drawings and three examples.

First, the same configuration of the three embodiments will be described.

Referring to Fig. 2, 3 or Fig. 4, 5, these three embodiments all are double-end face hydrodynamic and static pressure mechanical seals for the sodium-cooled fast reactor nuclear main pump, and are composed of a moving ring 10, an O-ring 9 for a moving ring, and a static ring 8 , 12, O-ring 7, 13 for static ring, spring 6, 15, spring seat 5, 14, sealing shell 16, shaft sleeve 1, O-ring 17 for shaft sleeve, limiter 4, pin 11 and set screw 3 and so on.

Specifically, the moving ring 10 and the static rings 8, 12 and spring seats 5, 14 at both ends of the moving ring 10 are fitted on the shaft sleeve 1; the moving ring 10 and the shaft sleeve 1 are sealed and connected by an O-ring 9; the moving ring The upper and lower ends of 10 are the sealing end faces of the moving ring, and each moving ring sealing end face cooperates with a static ring, and the outer circular surfaces of the static rings 8, 12 and the sealing shell 16 are sealed and connected by O-rings 7, 13; the static rings The other end faces support more than 3 springs respectively, and the other ends of the springs act on the spring seats 5, 14, and the spring seats 5, 14 are fixedly connected to the upper and lower parts of the sealing shell by bolts, so that the sealing end face of the moving ring and the end face of the static ring A certain end surface specific pressure is obtained between them; the moving ring 10 cooperates with the pin 11 on the shaft sleeve through the radially closed and axially opened pin hole located at the lower part of the moving ring to realize the circumferential positioning of the moving ring 10 and keep the pin 11 and The bottom of the pin hole is in contact with the axial positioning of the moving ring 10; the set screw 3 is arranged on the shaft sleeve.

The two stationary rings have the same structure and both weigh GJ. The number of springs 15 supporting the static ring at the lower part of the moving ring is the same as the number of springs 6 supporting the static ring at the upper part of the moving ring, both of which have a stiffness of K, and they are evenly distributed in the circumferential direction of the static ring.

The limiter 4 is a split-type limit ring composed of two semicircular limit half-rings, the limit ring is detachably connected to the upper surface of the upper spring seat 5 by screws, and the inner side of the limit ring extends into the In the limiting groove opened on the shaft sleeve 1, the shaft sleeve 1, the sealing shell 16, and the spring seat 5, 14 are kept at a certain position in the axial direction. In this position, the compression length △x2 of the spring 15 and the compression length △x1 of the spring 6 supporting the static ring on the upper part of the moving ring satisfy: △x2-△x1=2GJ/K, so that the sealing end faces at both ends of the moving ring and the two The pressure between the static rings is the same.

The static ring uses O-rings 7, 13, the moving ring 10, and the sealed shell 16 to enclose an outer sealed space, and the outer sealed space is filled with argon gas as a blocking fluid.

Referring to Figures 6, 7, and 9, the end face of the moving ring seal that cooperates with the static rings 8 and 12 is divided into a groove area and a seal dam 37, the groove area is distributed on the outer part of the end face, and the seal dam 37 is distributed on the inner part of the end face; the groove area More than 3 groups of back-curved fluid grooves 39 are provided, and the sealing end faces between the back-curved fluid grooves 39 form a sealing weir; The axis of the moving ring and the middle section M-M of the moving ring passing through the middle position of the moving ring are arranged symmetrically.

The back-curved fluid groove 39 includes two parts: a slope groove 32 and a flat groove 33. The slope groove 32 is located at the large radius portion of the end face of the moving ring, and the flat groove 33 is located at the small radius portion of the end face of the moving ring;

The outlet of the backward curved fluid groove 39 is located at the outer diameter of the moving ring sealing end face, the inlet 31 is located in the middle of the sealing surface of the moving ring 10, and the inlet 31 of the backward bending fluid groove 39 passes through the The axial-radial combination channel 30 communicates with the outer sealing space;

On both sides of the back-curved fluid groove 39, one side is the working surface 34, and the other side is the non-working surface 35;

The blocking fluid in the back-curved fluid-type groove 39 is accelerated into a high-speed fluid by the working surface of the backward-curved fluid-type groove 39 when the moving ring rotates, and flows toward the moving ring 10 along the non-working surface 35 under the centrifugal force. The outer diameter side flows and is pumped into the outer sealing space, and a low-pressure area is formed at the inlet 31 of the back-curved fluid groove 39, and the blocking fluid in the outer sealing space passes through the moving ring 10 or the static ring 8 under the action of the pressure difference , 12, the axial and radial combination channels 30 and other flow passages connected with the outer sealing space flow into the back-curved fluid groove 39 to form self-pumping cycles again and again;

The blocked fluid that is accelerated into a high speed by the working surface 34 of the back-curved fluid-type groove 39 is pumped out of the back-curved fluid-type groove 39. As the pressure increases, the flow rate decreases and the pressure increases, forming an opening force that separates the moving ring 10 from the static rings 8 and 12.

The above-mentioned double-face hydrodynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump is a cartridge mechanical seal, which can be quickly installed on site after being assembled in the factory. During installation, the shaft sleeve 1 is put on the pump shaft 2 of the sodium pump, the spring seat 15 at the bottom is sealed and fixed with the casing of the sodium pump, and then the set screw 3 is screwed on the pump shaft. At this moment, the positions of the axle sleeve and the spring seat 15 (comprising the sealing shell 16, the spring seat 4, etc.) are all fixed, so removing the stopper 4 will not change the relative position of the axle sleeve and the spring seat, ensuring The compression length △x2 of spring 15 and the compression length △x1 of spring 6 are at the preset lengths when leaving the factory, so that the pressure between the sealing end faces at both ends of the moving ring and the two static rings in operation is the same, prolonging the service life.

When in use, the O-ring 17 for the shaft sleeve, the shaft sleeve 1, the lower static ring 12, the O-ring 13 for the static ring, the moving ring 10, the casing of the sodium pump, and the pump shaft 2 form a working medium cavity, and the working medium cavity The inner and lower parts are high-temperature metal sodium liquid, and the upper part is protective argon; the pressure of argon in the outer sealed space is not less than the pressure of argon in the working medium cavity. Since the pressure of the blocking fluid is not less than the pressure of the argon in the working medium cavity, the argon in the working medium cavity will not leak into the outer sealed space through the sealing end face between the static ring and the moving ring. Even if the dynamic and static rings are disengaged instantaneously under the action of earthquake load, it is only possible that the blocking fluid leaks through the sealing end face between the static ring and the moving ring and enters the working medium cavity, but because the blocking fluid is the same as the upper medium in the working medium cavity , so even if the blocked fluid enters the working medium cavity, it will not affect the work of the nuclear main pump.

The different structures of the various embodiments will be described separately below.

The main differences of the three embodiments are: whether the axial-radial combination channel 30 is opened on the moving ring or the stationary ring, whether there is a circular ring groove, and whether the circular ring groove is opened on the moving ring or the stationary ring. Instructions are given below.

Example 1: A double-end fluid dynamic and static pressure mechanical seal for a sodium-cooled fast reactor nuclear main pump with axial and radial combined channels on the moving ring

Referring to Figures 2, 3 and 6, the inlets 31 of the backward curved fluid grooves 39 located at the upper and lower ends of the moving ring communicate with the outer sealing space through the axial and radial combination channels 30 opened on the moving ring 10 . When the moving ring rotates, the blocking fluid in the outer sealing space, such as argon, flows into the back-curved fluid groove 39 through the axial and radial combined holes 30 on the moving ring 10 under the action of pressure difference, forming a self-pump again and again. send loop.

Example 2: A double-end fluid dynamic and static pressure mechanical seal for a sodium-cooled fast reactor nuclear main pump with circular grooves on the moving ring and axial and radial combined channels on the static ring

Referring to Figures 4, 5, 7 and 8, the inlet 31 of the back-curved fluid groove 39 on the moving ring communicates with the circular ring groove 36 arranged in the middle of the sealing surface of the moving ring 10 . One end of the axial-radial combination hole 30 opened on the static ring communicates with the outer sealing space, and the other end is opposite to the circular ring groove 36 in the axial direction.

When the moving ring rotates, the blocking fluid in the outer sealing space, such as argon, flows into the back-curved fluid type through the axial and radial combination channels 30 on the static ring and the circular ring groove 36 on the moving ring under the action of pressure difference. In the tank 39, a self-pumping cycle is formed time after time.

Example 3: A double-end fluid dynamic and static pressure mechanical seal for a sodium-cooled fast reactor nuclear main pump with circular grooves and axial and radial combined channels on the static ring

Referring to Figures 9 and 10 (refer to Figures 4 and 5), the inlet 31 of the backward curved fluid groove 39 on the moving ring communicates with the circular ring groove 36 opened in the middle of the sealing surface of the static ring, and the circular ring groove 36 communicates with the outer sealing space through the axial and radial combination holes 30 opened on the stationary ring. When the moving ring rotates, the blocking fluid in the outer sealing space, such as argon, flows into the back-curved fluid type through the axial and radial combination channels 30 on the static ring and the circular ring groove 36 on the static ring under the action of pressure difference. In the tank 39, a self-pumping cycle is formed time after time.

Claims (9)

1. The utility model provides a two terminal surface fluid dynamic and static pressure mechanical seal for sodium-cooled fast reactor nuclear main pump sets up between casing and pump shaft (2) of sodium pump, by rotating ring (10), O shape circle (9) for the rotating ring, quiet ring (8, 12), O shape circle (7, 13) for the quiet ring, spring (6, 15), spring holder (5, 14), seal housing (16), axle sleeve (1), O shape circle (17) for the axle sleeve, stopper (4), pin (11) and holding screw (3) etc. constitute characterized by:

the movable ring (10) and the static rings (8, 12) and the spring seats (5, 14) on the two sides of the movable ring are sleeved on the shaft sleeve (1) in a penetrating way; the movable ring (10) is hermetically connected with the shaft sleeve (1) by an O-shaped ring (9); the upper end and the lower end of the movable ring (10) are movable ring sealing end faces, each movable ring sealing end face is matched with 1 static ring, and the outer circular faces of the static rings (8 and 12) are hermetically connected with the sealing shell (16) through O-shaped rings (7 and 13); more than 3 springs are respectively supported on the other end face of the static ring, the other ends of the springs act on spring seats (5 and 14), the spring seats (5 and 14) are connected with the sealing shell, and a certain end face specific pressure is obtained between the sealing end face of the movable ring and the end face of the static ring; the movable ring (10) is matched with a pin (11) on the shaft sleeve through a pin hole which is positioned at the lower part of the movable ring and is radially closed and axially opened, so that the circumferential positioning of the movable ring (10) is realized, and the pin (11) is kept in contact with the bottom of the pin hole while the axial positioning of the movable ring (10) is realized; the set screw (3) arranged on the shaft sleeve is used for fixing the relative position of the shaft sleeve (1) and the pump shaft (2); the limiter (4) is detachably arranged between the sealing shell (16) or the spring seats (5 and 14) and the shaft sleeve (1) and is used for limiting the axial relative position of the shaft sleeve (1) and the sealing shell (16) or the spring seats (5 and 14) so as to change the elastic force of the springs supporting the two static rings, so that the pressure between the sealing end surfaces at the two ends of the movable ring and the pressure between the two static rings are the same;

the static ring is enclosed into an outer sealing space by the O-shaped rings (7, 13), the dynamic ring (10) and the sealing shell (16), and a blocking fluid is filled into the outer sealing space;

the sealing end face of the movable ring matched with the static rings (8 and 12) is divided into a groove area and a sealing dam (37), the groove area is distributed on the outer side part of the end face, and the sealing dam (37) is distributed on the inner side part of the end face; more than 3 groups of backward bending type fluid grooves (39) are arranged in the groove area, and sealing end faces between the backward bending type fluid grooves (39) form a sealing weir; the groove areas on the sealing end surfaces of the movable ring at the upper end and the lower end of the movable ring (10) and the sealing dam (37) are symmetrically arranged by the middle section (M-M) of the movable ring;

the backward bending type fluid type groove (39) comprises a slope groove (32) and a flat groove (33), the slope groove (32) is positioned at the large radius part of the end surface of the moving ring, and the flat groove (33) is positioned at the small radius part of the end surface of the moving ring;

the outlet of the backward bent fluid type groove (39) is positioned at the outer diameter of the sealing end face of the moving ring, the inlet (31) is positioned in the middle of the sealing surface of the moving ring (10), and the inlet (31) of the backward bent fluid type groove (39) is communicated with the outer sealing space through an axial and radial combined pore passage (30) on the moving ring (10);

two side groove walls of the backward bending type fluid type groove (39), one side is a working surface (34), and the other side is a non-working surface (35);

when the moving ring rotates, the blocking fluid in the backward-bent fluid type groove (39) is accelerated into high-speed fluid by the working surface of the backward-bent fluid type groove (39), flows to the outer diameter side of the moving ring (10) along the non-working surface (35) under the action of centrifugal force and is pumped into the outer sealing space, a low-pressure area is formed at the inlet (31) of the backward-bent fluid type groove (39), and the blocking fluid in the outer sealing space flows into the backward-bent fluid type groove (39) through an axial and radial combined pore passage (30) which is arranged on the moving ring (10) and is communicated with the outer sealing space under the action of differential pressure, so that a primary self-pumping circulation is formed;

the working surface (34) accelerated by the backward-bent fluid groove (39) is high-speed blocked fluid, and in the process of being pumped out of the backward-bent fluid groove (39), along with the gradual increase of the flow cross section area of the backward-bent fluid groove (39), the flow speed is reduced, the pressure is increased, and the opening force for separating the movable ring (10) and the static rings (8 and 12) is formed.

2. The double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump as claimed in claim 1, which is characterized in that: the shaft sleeve is provided with an O-shaped ring (17), the shaft sleeve (1), a static ring (12) at the lower part and a working medium cavity enclosed by the O-shaped ring (13), a moving ring (10), a shell of the sodium pump and a pump shaft (2) for the static ring, the lower part in the working medium cavity is high-temperature metal sodium liquid, and the upper part in the working medium cavity is protective argon; the blocking fluid in the outer sealing space is also argon, and the pressure of the blocking fluid is not less than the pressure of the argon in the working medium cavity.

3. the double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump is characterized in that the number and the structure of springs supporting two static rings are the same, the spring stiffness is K, the structures of the two static rings are the same, the weight is GJ, the compression length △ x2 of the spring supporting the static ring positioned at the lower part of the dynamic ring and the compression length △ x1 of the spring supporting the static ring positioned at the upper part of the dynamic ring meet the requirement that △ x2- △ x1 is 2GJ/K, so that the pressure between the sealing end faces at the two ends of the dynamic ring and the two static rings is the same.

4. The double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump as claimed in claim 1, which is characterized in that: the molded lines of the groove walls on the two sides of the backward bending type fluid groove (39) are helical lines.

5. The double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump as claimed in claim 4, which is characterized in that: the spiral lines of the molded lines of the groove walls on the two sides of the backward bending type fluid groove (39) have the same spiral angle.

6. The double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump as claimed in claim 4, which is characterized in that: the spiral angles of the spiral lines of the groove wall molded lines on the two sides of the backward bending type fluid groove (39) are different, and the spiral angle of the working surface (34) is smaller than that of the non-working surface (35).

7. The double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump as claimed in claim 4, which is characterized in that: the spiral lines of the molded lines of the groove walls at the two sides of the backward bending type fluid groove (39) are tangent to the round hole of the inlet (31).

8. The double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump as claimed in claim 5, which is characterized in that: the cross section of the joint of the axial and radial combined pore canal (30) on the moving ring (10) and the outer circular surface of the moving ring (10) is a wedge-shaped opening (38).

9. The double-end-face fluid dynamic and static pressure mechanical seal for the sodium-cooled fast reactor nuclear main pump as claimed in claim 1, which is characterized in that: an inlet (31) of the backward bending type fluid groove (39) is communicated with a circular ring groove (36) arranged in the middle of the sealing surface of the moving ring (10) or the static rings (8, 12), and the circular ring groove (36) is at least communicated with the outer sealing space through the circular ring groove positioned on the static ring; when the rotating ring rotates, blocking fluid in the outer sealing space flows into the backward-bent fluid groove (39) through the axial and radial combined pore canal (30) and the circular ring groove (36) which are arranged on the static ring and communicated with the outer sealing space under the action of pressure difference, and a primary and secondary self-pumping circulation is formed.