CN210343823U

CN210343823U - Combined non-contact double-end-face seal based on magnetic liquid seal and fluid dynamic pressure mechanical seal

Info

Publication number: CN210343823U
Application number: CN201921047622.4U
Authority: CN
Inventors: 葛诚; 倪兴雅; 马琳博; 孙见君; 马晨波; 於秋萍
Original assignee: Nanjing Forestry University
Current assignee: Nanjing Forestry University
Priority date: 2019-07-07
Filing date: 2019-07-07
Publication date: 2020-04-17
Anticipated expiration: 2029-07-07

Abstract

The patent provides a combined non-contact double-end-face seal based on magnetic liquid seal and fluid dynamic pressure mechanical seal to guarantee zero leakage and long-period safe and stable operation of molten salt pump shaft seal. The combined non-contact double-end-face seal is arranged between a shell and a rotating shaft of rotating equipment, and consists of a pumping-in type fluid dynamic pressure mechanical seal and a magnetic liquid seal, the upper end face and the lower end face of a moving ring are moving ring seal end faces, each moving ring seal end face is provided with a groove platform area and a seal dam, and the groove platform area is provided with uniformly distributed spiral grooves; the flow collecting ring groove is positioned on the outer diameter side of the sealing end face, the flow guiding pore passage is used for communicating the flow collecting ring groove with the blocked fluid cavity, and the magnetic force generating mechanism is positioned on the inner diameter side of the sealing end face; when the moving ring and the static ring rotate relatively, the spiral groove pumps blocking fluid to generate end face opening force, the sealing end face is separated, and the end face opening distance delta formed by fluid dynamic pressure is added with the distance d between the pole shoe and the end face of the static ring to form a magnetic liquid sealing gap d + delta in a running state.

Description

Combined non-contact double-end-face seal based on magnetic liquid seal and fluid dynamic pressure mechanical seal

Technical Field

This patent belongs to mechanical seal technical field, relates to from the fluid dynamic pressure mechanical seal of pumping and magnetic liquid sealing technique, and the sealing between the pivot of specially adapted gas protection pump or compressor and the casing.

Background

Since the world-wide shortage of energy and resources has become more serious and the environmental problems such as greenhouse gas effect have become more prominent, the search for sustainable, safe, stable and environmentally friendly energy has been receiving attention from various countries. The fourth generation international forum for nuclear energy (GIF) policy group issued a technical route map in 2002, which proposed 6 reactor types accepted by almost all nuclear energy countries, of which 3 are a sodium-cooled fast reactor, a lead-cooled fast reactor and a gas-cooled fast reactor, and the other 3 are an ultra-high temperature reactor, a supercritical water reactor and a molten salt reactor. Among them, molten salt reactors are receiving attention from various countries in the world due to advantages such as high efficiency, low waste emission, and low pressure in the core region.

Fig. 1 is a schematic diagram of a primary molten salt pump of a molten salt reactor. The upper part of the free liquid level of liquid molten salt in the shell of the molten salt pump is filled with argon, a heat shield is arranged at a certain height away from the liquid level of the molten salt, a mechanical seal is arranged above the heat shield, and the leakage of a medium in a pump cavity along the rotating shaft is stopped. The design form avoids direct contact between the seal and the molten salt with the temperature as high as 700 ℃, and eliminates a plurality of severe limitations of the seal device on materials, structures and the like.

According to the prior art, a molten salt pump references the 3 rd-stage seal of a light water reactor (comprising a pressurized water reactor and a boiling water reactor), a heavy water reactor and a graphite gas cooled reactor, namely, the seal is realized by using lubricating oil as a double-end-face mechanical seal for blocking fluid or using gas as a dry gas seal for blocking fluid. However, the mechanical seal fails due to the end face friction wear caused by the relative rotation between the dynamic ring and the static ring of the mechanical seal and the aging of the auxiliary seal O-shaped ring; in this case, the mechanical seal needs to be replaced or removed for maintenance. Since the existing mechanical seals are all integral, when a wearing part is replaced, a fitting part at the shaft end needs to be disassembled, and the mechanical seals are large in engineering amount, long in time consumption and high in cost, the split mechanical seals are researched since 90 years, and the split mechanical seals are expected to be replaced by the split mechanical seals. However, the split surface of the seal ring and the sealing reliability of the joint of the split O-ring are difficult to be ensured under working conditions. Therefore, fluid dynamic pressure mechanical seals are used to solve the problems of short service life of contact type mechanical seals and low reliability of split type mechanical seals, but the fluid dynamic pressure mechanical seals with the service life replaced by the service life of the seal performance sacrificed cannot meet the requirement of zero leakage of the molten salt reactor nuclear main pump.

US 3782737 reports a low leakage spiral groove seal for a variety of liquids such as water, sodium or oil, where a channel on a stationary ring is used to introduce a working fluid (lubricating fluid) into the land area of a seal face, and when a rotating ring with a spiral groove rotates, the automatic pumping action of the spiral groove causes the fluid to flow to a seal cavity and to be converted into a hydrodynamic pressure increase with a decrease in the fluid velocity at the flow interface of the spiral groove, which seems to overcome the sensitivity of the mechanical seal to the cleanliness of the working fluid, but the stationary ring channel is in clearance communication with the spiral groove, on the one hand, the hydrodynamic pressure is in a pulsating state, which is not conducive to the stable operation of the mechanical seal, and on the other hand, the fluid entering the stationary ring channel flows into the weir area of the seal face in clearance, which causes the seal face; ZL201310201473.3 has proposed a self-pumping fluid dynamic pressure type mechanical seal, circulate between seal face and seal chamber through sealing medium, realized seal face self-lubricating, self-flushing, guaranteed sealed stability and permanence, but during the pump-out type self-pumping fluid dynamic pressure type mechanical seal work, need provide and block liquid in order to form sufficient opening force, reduce the frictional wear between the quiet ring of moving, and pump out the low-pressure area that forms at the root of the profiled groove when blocking the fluid, be unfavorable for realizing the sealed of sealed face internal diameter side argon gas.

The molten salt reactor nuclear main pump is suitable for application of a magnetic liquid sealing technology under the working conditions of low pressure difference and low temperature of the molten salt reactor nuclear main pump seal. The magnetic liquid seal has long service life, high reliability, self-adaptive structure, zero leakage, simple structure and convenient use, but the high sensitivity of the sealing capability to the seal clearance greatly limits the application of the magnetic liquid seal technology to the molten salt reactor nuclear main pump (see figure 1) with the upper end of the rotating shaft 3 being the end face thrust bearing 2 and the lower end being the guide sliding bearing 4; the radial runout of the rotating shaft enables the radial sealing gap of the magnetic liquid to be changed continuously, and the stability and the integrity of the magnetic liquid film are damaged. ZL 201410614383.1 has proposed an axial seal's lubricated mechanical seal device of magnetic current body, the device is moving, quiet ring fitting surface outside is equipped with controllable magnetic field generator, form the magnetic field between sound ring seal interface, change magnetic field size through adjustment voltage, utilize the rotation of seting up the helicla flute on the rotating ring to wedge the magnetic fluid of sealed face external diameter side into the helicla flute and form the dynamic pressure, form controllable magnetic fluid seal liquid film at sealed interface, prevent the leakage of sealing medium on the one hand, on the other hand separation moves, quiet ring, avoid frictional wear, realize long-life operation. However, this structure has several problems: firstly, in the starting and stopping process, particles in the magnetic liquid on the sealing interface can aggravate the abrasion of the sealing end surfaces of the moving ring and the static ring; secondly, in the stable operation process, the magnetic liquid is filled in the whole sealing interface, if the gap of the sealing end surface is suddenly reduced, the magnetic liquid is extruded out of the sealing interface and is suspended at the edge of the inner diameter and the outer diameter of the sealing surface, and even thrown into or directly splashed into a pump cavity, so that a molten salt medium is polluted, and an accident is caused; moreover, the relative motion of the moving and static rings causes friction between the magnetic liquid with a sealing interface and large viscous shearing force to generate heat, and the temperature is concentrated and increased, so that the temperature rise not only causes the deformation of the sealing ring, but also causes the reduction of magnetic force, and the sealing capacity of the magnetic liquid sealing is influenced.

Disclosure of Invention

The patent aims to provide a combined non-contact double-end-face seal based on magnetic liquid seal and fluid dynamic pressure mechanical seal, which is used for sealing between a rotating shaft and a shell of a molten salt reactor nuclear main pump so as to ensure zero leakage and long-period safe and stable operation of a molten salt pump shaft seal.

The technical solution of this patent is: a combined non-contact double-end-face seal based on magnetic liquid seal and fluid dynamic pressure mechanical seal is arranged between a shell and a rotating shaft of rotating equipment and comprises a moving ring 16,

static rings

12 and 19, an O-shaped ring 15 for the moving ring, magnetic

liquid seal rings

11 and 20 for the static rings,

permanent magnets

13 and 17,

pole shoes

14 and 18,

springs

10 and 21, end covers 9 and 22, a shell 23, a shaft sleeve 6 and a set screw 7; the combined non-contact double-end-face seal consists of a pumping type hydrodynamic mechanical seal and a magnetic liquid seal, wherein the magnetic liquid seal is arranged in the middle of a sealing dam of the self-pumping hydrodynamic mechanical seal;

the upper end face and the lower end face of the movable ring 16 are movable ring sealing end faces, each movable ring sealing end face is provided with a groove platform area and a sealing dam, the groove platform areas are distributed on the outer diameter side of the end face, the sealing dams 30 are distributed on the inner diameter side part of the end face, 3 groups or more than 3 groups of uniformly distributed spiral grooves 28 are formed in the groove platform areas, sealing surfaces among the spiral grooves form a sealing weir 29, the groove walls on two sides of the spiral groove 28 are convex 31 on one side, concave 32 on the other side, and the upper end face and the lower end face of the movable ring 16 are symmetrically arranged according to the middle section M-M of the;

the sealing end faces of the

static rings

12 and 19 are provided with a collecting ring groove 34 and a magnetic force generating mechanism, the collecting ring groove 34 is positioned on the outer diameter side of the sealing end face, the collecting ring groove 34 is communicated with the blocked fluid cavity through a drainage channel 33, and the magnetic force generating mechanism is positioned on the inner diameter side of the sealing end face;

the annular

permanent magnets

13 and 17 are embedded into the

pole shoes

14 and 18 to form a magnetic force generating mechanism, the magnetic force generating mechanism is embedded into magnetic force mechanism mounting ring grooves formed in the sealing end faces of the

static rings

12 and 19 to form a whole with the static rings, annular pole teeth and tooth grooves distributed at equal intervals along the radial direction are formed in the end faces of the

pole shoes

14 and 18, all the pole teeth of the pole shoes face the sealing end faces of the

static rings

12 and 19, and the end faces of the pole teeth of the

pole shoes

14 and 18 are 0.05-0.2 mm lower than the sealing end faces of the

static rings

12 and 19 after assembly;

magnetic liquid is injected into the pole teeth of the

pole shoes

14 and 18, the magnetic liquid is adsorbed on the end faces and the peripheries of the pole teeth of the pole shoes under the action of magnetic force, and magnetic liquid sealing rings with different diameters distributed along the radial direction are formed between the pole teeth and the middle part of the movable ring sealing dam;

when the moving ring 16 and the

static rings

12 and 19 are relatively static, under the action of spring force, the moving ring 16 and the

static rings

12 and 19 are tightly attached to each other, and the initial gap d between the pole teeth of the

pole shoes

14 and 18 and the sealing end surfaces of the

static rings

12 and 19 is 0.05-0.2 mm, namely the static magnetic liquid sealing gap d; at the moment, the contact seal formed by the seal end face of the static ring and the seal dam face of the dynamic ring and the magnetic liquid seal jointly act to prevent fluid leakage;

when the moving ring 16 and the

static rings

12 and 19 rotate relatively, the spiral groove 28 on the end surface of the moving ring 16 pumps blocking fluid to generate end surface opening force, the sealing end surface is disengaged, the end surface opening distance delta formed by fluid dynamic pressure is 3-5 mu m at the moment, and the distance d between the pole shoe 14 and the pole shoe 18 and the end surfaces of the

static rings

12 and 19 is 0.05-0.2 mm, so that a magnetic liquid sealing gap d + delta of the sealing end surface in a running state is formed; along with the operation of the pumping type fluid dynamic pressure mechanical seal, fluid is blocked to be continuously pumped and circulated, friction heat of the end face is taken away, the seal end face is effectively cooled, the temperature of magnetic liquid is reduced, and a proper working environment is created for the magnetic liquid seal; and zero leakage of the sealing end face is ensured under the combined action of the pumping-in type fluid dynamic pressure mechanical seal and the magnetic liquid seal.

The shaft sleeve 6, the O-shaped ring 8 for the shaft sleeve, the moving ring 16, the static ring 19, the magnetic liquid sealing ring 20 for the static ring, the shell 23 of the rotating equipment and the rotating shaft 3 form a working medium cavity in a surrounding mode, the lower portion in the working medium cavity is high-temperature molten salt, the upper portion is protective argon, the blocking fluid is also argon, and the setting range of the fluid pressure is blocked: the minimum pressure is the pressure of the sealed medium in the rotating equipment, and the maximum pressure is the sum of the sealing pressure of the magnetic liquid and the pressure of the sealed medium in the rotating equipment.

The

pole shoes

14 and 18 are provided with two sets of pole teeth and tooth grooves which are arranged at intervals along the radial direction on one side facing the sealing end face, each set is provided with 3-5 pole teeth which are arranged along the radial direction, the tooth width is 0.5-2 mm, and the groove width is 0.5-2 mm; the

permanent magnets

13, 17 are magnetized in the radial direction.

The outer diameter of the collecting ring groove 32 on the end face of the static ring 12 or the static ring 19 is larger than the diameter of the groove root circle of the spiral groove 28 on the end face of the dynamic ring 16, the inner diameter is smaller than or equal to the diameter of the groove root circle of the spiral groove 28, and the ring width of the collecting ring groove 34 is equal to the diameter of the drainage pore passage 33;

the outer diameter of the magnetic force generating mechanism is smaller than the inner diameter of the collecting ring groove 34, and the inner diameter of the magnetic force generating mechanism is larger than the inner diameter of the sealing end faces of the

static rings

12 and 19.

The dynamic ring 16, the

static rings

12 and 19 on the two sides of the dynamic ring and the end covers 9 and 22 are sleeved on the shaft sleeve 6 in a penetrating way; the shaft sleeve 6 and the rotating shaft are fixed through a set screw 7, and the shaft sleeve 6 and the rotating shaft are sealed by an O-shaped ring 8; the movable ring 16 and the shaft sleeve 6 are sealed by an O-shaped ring 15; the back of the static ring sealing end face is respectively supported with more than 3

springs

10, 21, the other ends of the springs act on the end covers 9, 22, the end covers 9, 22 are fixedly connected with a shell 23 of the rotary equipment, and the required end face specific pressure is obtained between the dynamic ring sealing end face and the static ring sealing end face.

The movable ring 16 is connected with the shaft sleeve 6 through threads 24, the thread rotating direction is opposite to the rotating direction of the rotating shaft, the movable ring 16 and the shaft sleeve 6 are positioned by adopting an outer cylindrical surface of the shaft sleeve 6 in the radial direction, and are positioned by adopting a shaft shoulder end surface on the shaft sleeve 6 in the axial direction.

The magnetic

liquid sealing rings

11 and 20 for the static rings between the

static rings

12 and 19 and the shell 23 are composed of pole shoe rings 27 and permanent magnet rings 26, and the radial gap between the inner cylindrical surface of the pole shoe rings 27 and the outer cylindrical surface of the static rings is 0.05-0.2 mm.

The

static rings

12 and 19 and the shell 23 are positioned by adopting a static ring outer cylindrical surface in the radial direction, the static rings are positioned by adopting an anti-rotating pin in the circumferential direction, the magnetic

liquid sealing rings

11 and 20 for the static rings are embedded and fixed in the shell 23, and the radial sealing gaps between the

static rings

12 and 19 and the inner cylindrical surfaces of the pole shoe rings 27 of the magnetic

liquid sealing rings

11 and 20 for the static rings are constant.

The working principle of the pumping-in type fluid dynamic pressure mechanical seal is as follows: the pumping-in type fluid dynamic pressure mechanical sealing end surface structure is characterized in that a spiral groove is formed in the sealing end surface of a movable ring, and a flow collecting ring groove and a drainage pore channel are formed in the sealing end surface of a static ring. When the pumping type fluid dynamic pressure mechanical seal runs, the movable ring rotates, blocking fluid is pumped in through the spiral groove and does work through the concave surface of the spiral groove, on one hand, the fluid pressure is improved, meanwhile, the fluid in the spiral groove is accelerated to be high-speed fluid, the fluid flows to the root of the spiral groove along the spiral groove, the number of fluid molecules flowing through a unit flow cross section is increased along with the gradual reduction of the flow cross section of the spiral groove, the fluid pressure is further improved, on the other hand, the fluid in the spiral groove enters the flow collecting ring groove with the wide flow cross section of the fluid on the sealing end surface of the stationary ring after flowing through the root of the spiral groove with the narrowest flow cross section, the fluid speed is suddenly reduced, partial fluid kinetic energy is converted into fluid dynamic pressure energy, and the fluid pressure is improved again, so that opening force; meanwhile, the rotating ring rotates to form circumferential shearing force of fluid between the sealing end faces, and the fluid on one side of the sealing end faces is prevented from flowing to the other side under the action of pressure difference, so that the purpose of sealing is achieved. The fluid wedged into the spiral groove from the blocking fluid cavity flows into the collecting ring groove on the sealing end face of the static ring after flowing through the root of the spiral groove with the narrowest flow cross section, and flows back to the blocking fluid cavity through the drainage hole channel under the action of pressure difference to form a one-time self-pumping cycle. In the self-pumping circulation process, the continuous circulation of the fluid between the sealing end faces takes away the friction heat between the sealing end faces in time, and the self-flushing and the self-cooling of the sealing are realized.

The magnetic liquid sealing working principle is as follows: under the action of a magnetic field generated by a circular permanent magnet of the magnetic mechanism, magnetic fluid between the top end of a pole shoe and the gap of the sealing end face of the moving ring is concentrated between the top end of a pole tooth and the sealing dam face of the moving ring to form O-shaped liquid rings, axial gaps between the sealing end faces of the moving ring and the static ring are divided into a plurality of independent and non-communicated closed annular chambers, and fluid on one side of the sealing end face is prevented from flowing to the other side to achieve the purpose of sealing.

On the annular pole shoe, the pole teeth and the tooth grooves are arranged at intervals along the radial direction, and the sealing pressure difference which can be borne by the single-pole seal is

Δp_max＝M_S(B_max-B_min)

In the formula, M_STo saturation magnetization

Is the maximum magnetic field induction strength value under the teeth,

is the minimum magnetic field induction value under the slot, F_gTo seal the gap magnetic voltage drop, mu₀To initiate permeability, g is the seal gap, β is the tilt angle, and S is the slot width.

For a magnetic liquid seal with N pole teeth, the limit sealing pressure difference is

It can be seen that the sealing pressure of the magnetic fluid and the performance of the permanent magnet, the number of teeth N of the pole shoe, and the saturation magnetization M_SAnd the difference value delta B between the maximum magnetic field intensity and the minimum magnetic field intensity under each stage of pole teeth between the top end of the pole teeth and the sealing dam face of the moving ring_iAre closely related. Saturation magnetization M_SAnd the difference delta B between the maximum magnetic field intensity and the minimum magnetic field intensity under each stage of pole tooth in the sealing gap between the top end of the pole tooth and the sealing dam surface of the moving ring_iThe larger the number of teeth N of the pole shoes, the stronger the pressure resistance of the magnetic fluid seal.

When no pressure difference exists between the inner side and the outer side of the sealing end face, the magnetic liquid between the top end of the pole tooth and the sealing dam face of the movable ring is symmetrically gathered on the circumference of the middle diameter of the top end of the pole tooth to form a liquid ring with a rectangular section; when pressure difference exists in the inner side and the outer side of the sealing end surface, the magnetic liquid is in an arched section liquid ring with a concave surface at the high-pressure side and a convex surface at the low-pressure side, and the generated elastic force of the original state is used for balancing the acting force of the pressure difference; when the pressure difference between the inner side and the outer side of the sealing end surface is increased to exceed the bearing capacity of the magnetic liquid seal, the magnetic liquid ring gathered at the top end of the pole tooth starts to deform and then rapidly perforates, and at the moment, the sealed medium flows to the next stage through the needle hole; along with the increase of the pressure in the next-stage closed annular chamber, the pressure difference between the inner diameter and the outer diameter of the magnetic liquid ring at the top end of the pole tooth is reduced, the magnetic liquid is gathered again under the action of a magnetic field generated by the annular permanent magnet of the magnetic mechanism, and the needle hole is healed and restored to a working state.

The working principle of the combined non-contact double-end-face seal based on magnetic liquid seal and fluid dynamic pressure mechanical seal is as follows: when the moving ring 16 and the

static rings

pole shoes

14 and 18 and the sealing end surfaces of the

static rings

12 and 19 is 0.05-0.2 mm, namely the static magnetic liquid sealing gap d; at the moment, the contact seal formed by the seal end face of the static ring and the seal dam face of the dynamic ring and the magnetic liquid seal jointly act to prevent fluid on one side of the seal end face from flowing to the other side under the action of pressure difference so as to achieve the purpose of sealing;

when the moving ring 16 and the

static rings

12 and 19 rotate relatively, the spiral groove 28 on the end surface of the moving ring 16 pumps blocking fluid to generate end surface opening force, the sealing end surface is separated, the end surface opening distance delta formed by fluid dynamic pressure is 3-5 mu m, and the initial distance d between the pole shoe 14 and the pole shoe 18 and the end surface of the

static rings

12 and 19 is 0.05-0.2 mm, so that a magnetic liquid sealing gap d + delta in a running state is formed; along with the operation of the pumping type fluid dynamic pressure mechanical seal, fluid is blocked to be continuously pumped and circulated, the friction heat of the end face is taken away, the sealing end face is effectively cooled, and the temperature of the magnetic liquid is reduced; under the combined action of shear flow of a pumping type fluid dynamic pressure mechanical seal and an O-shaped liquid ring of a magnetic liquid seal, the fluid on the two sides of the inner diameter and the outer diameter of the sealing end surface is ensured not to leak.

Because the magnetic liquid seal of the combined non-contact double-end-face seal is positioned at the sealing dam surface part of the moving ring and has certain radial width, when the moving ring generates radial displacement under the influence of the jumping of the rotating shaft, the magnetic liquid ring which is attached to the top end of the pole tooth of the static ring and is axially and tightly attached to the sealing dam surface of the moving ring generates micro radial displacement relative to the moving ring, but the width of the sealing dam surface of the moving ring ensures that the magnetic liquid ring can still keep an integral O-shaped liquid ring reliably positioned between the top end of the pole tooth of the static ring and the sealing dam surface of the moving ring, thereby providing sealing capability.

The patent has the advantages and positive effects that:

(1) zero leakage of the medium in the pump is achieved. The leakage of the fluid in the pump cavity is effectively prevented by utilizing the gapless seal of the blocking fluid, which is larger than the pressure of the medium in the pump cavity, and the magnetic liquid.

(2) The radial clearance sensitivity of the magnetic fluid seal is overcome. The permanent magnet and the pole shoe are arranged on the end face of the static ring, the sealing dam of the dynamic ring is matched with the permanent magnet and the pole shoe, when the dynamic ring jumps radially in the running process, although the position of the dynamic ring is deviated from the corresponding position of the pole shoe, the axial distance between the pole shoe and the sealing dam of the dynamic ring is unchanged, and the sealing capacity of magnetic liquid sealing is ensured.

(3) Has the effect of self-cooling the sealing interface. Fluid circulation formed by self-pumping continuously flows between sealing interfaces, heat generated by fluid viscosity shearing friction during working of magnetic liquid sealing and fluid dynamic pressure sealing is taken away, the temperature of the sealing interfaces is reduced, deformation of sealing end faces is reduced, and influence of the temperature on the sealing performance of the magnetic liquid is reduced.

(4) Extremely high sealing reliability. When the magnetic liquid seal in the combined seal is subjected to transient overvoltage breakdown or deflection deformation, the magnetic liquid of the combined seal is quickly self-healed under the action of a magnetic field and is reset between the pole teeth and the sealing dam, and the sealing capacity is formed again.

(5) The sealing interface has no friction and long service life. When the combined seal works, the self-pumping fluid dynamic pressure mechanical seal generates dynamic pressure, separates the dynamic ring and the static ring to form non-contact seal, so that the dynamic ring and the static ring have no friction and wear; the magnetic liquid is sealed, the magnetic liquid between the pole shoe and the sealing dam is used for sealing, the pole shoe is not in contact with the sealing dam, and friction and abrasion are avoided.

Drawings

The patent is further described with reference to the following figures and specific examples

FIG. 1 is a primary loop sodium pump schematic of a sodium cooled fast reactor prototype reactor (PFBR);

FIG. 2 is a cross-sectional view of the seal structure;

FIG. 3 is a view of the end face of the rotating ring;

FIG. 4 is a view of the end face of the stationary ring;

FIG. 5 is a schematic view of a dynamic and static ring structure

FIG. 6 is a perspective view of the magnetic force generating mechanism;

FIG. 7 is a schematic projection view of a magnetic mechanism on the sealing end face of the rotating ring;

FIG. 8 is a schematic view of a magnetic force cycle line of a magnetic mechanism between sealed end faces;

FIG. 9 is a schematic view of a magnetic liquid seal gap with the seal faces closed;

fig. 10 is a perspective view of a magnetic liquid seal ring for a stationary ring;

FIG. 11 is a schematic view of a magnetic force circulation line of a magnetic force mechanism of a magnetic liquid seal ring for a stationary ring;

FIG. 12 is a pole tooth field segmentation model;

fig. 13 is a schematic view of the magnetic liquid seal gap in the open state of the seal end face.

In the figure: 1, mechanical sealing; 2-a thrust bearing; 3-a pump shaft; 4, a guide bearing; 5, an impeller; 6, shaft sleeve; 7-pins; 8, an O-shaped ring is used for the shaft sleeve; 9-end cover; 10-a spring; 11-magnetic liquid sealing ring for stationary ring; 12-stationary ring; 13-a permanent magnet; 14-pole shoe; 15-O-shaped ring for moving ring; 16-a rotating ring; 17-a permanent magnet; 18-pole shoe; 19-stationary ring; 20, sealing the magnetic liquid for the stationary ring; 21-a spring; 22-end cap; 23-a sealed chamber housing; 24-pins; 25-a magnetic liquid; 26-permanent magnet ring; 27-pole shoe ring; 28-helical groove; 29-sealing weir; 30, sealing a dam; 31-spiral groove convexity; 32-concave surface of spiral groove; 33-drainage channel; and 34, collecting ring groove.

Detailed Description

To more clearly describe the above features and advantages of this patent, the following description of specific embodiments of this patent is provided in connection with the accompanying drawings.

Fig. 2 to 7 illustrate a combined non-contact double-end-face seal based on a magnetic liquid seal and a hydrodynamic mechanical seal, which is used for sealing a gap between a rotating shaft and a shell of a molten salt reactor nuclear main pump and can ensure zero leakage and long-period safe and stable operation of a molten salt pump shaft seal.

The upper end surface structure and the lower end surface structure of the moving ring 16 are symmetrically arranged by taking the middle section M-M of the moving ring, each end surface comprises three parts, namely a spiral groove 28, a sealing weir 29 and a sealing dam 30, the spiral grooves 28 are uniformly distributed on the outer diameter side of the end surface of the moving ring, the sealing dam 30 is arranged on the inner diameter side of the end surface of the moving ring, and the sealing surface between the spiral grooves 28 is the sealing weir 29.

The end surfaces of the

static rings

12 and 19 are provided with collecting ring grooves 34 and magnetic force generating mechanisms (consisting of permanent magnets 13, pole shoes 14 or permanent magnets 17 and pole shoes 18), the collecting ring grooves 34 are positioned on the outer diameter side of the end surfaces, the drainage pore channels 33 are uniformly distributed in the collecting ring grooves 34, and the magnetic force generating mechanisms are positioned on the inner diameter side of the end surfaces; the outer diameter of the collecting ring groove 34 is larger than the diameter of the root circle of the spiral groove 28 on the end face of the moving ring, the inner diameter of the collecting ring groove 34 is smaller than or equal to the diameter of the root circle of the spiral groove 28, and the ring width of the collecting ring groove 34 is equal to the diameter of the drainage pore passage 33; the outer diameter of the magnetic force generating mechanism is smaller than the inner diameter of the collecting ring groove 34, and the inner diameter of the magnetic force generating mechanism is larger than the inner diameter of the sealing end faces of the

static rings

12 and 19.

The stationary rings 12, 19 and the housing 23 are sealed with magnetic liquid. The permanent magnet ring 26 is embedded into the pole shoe ring 27 to form a magnetic force generating mechanism, the magnetic force generating mechanism is embedded into the shell 23 to form a whole with the shell 23, two groups of pole teeth and tooth grooves which are distributed at equal intervals along the axial direction are formed in the inner cylindrical surface of the pole shoe ring 27, all the pole teeth of the pole shoe ring face the outer cylindrical surfaces of the

static rings

12 and 19, and the radial gap between the end surface of the pole tooth of the pole shoe ring 27 and the outer cylindrical surface of the static ring is 0.05-0.2 mm after assembly.

Magnetic liquid is injected at the pole teeth of the pole shoe ring 27, the magnetic liquid is adsorbed on the end faces of the pole teeth of the pole shoe ring 27 and the periphery of the pole teeth under the action of magnetic force, and magnetic liquid sealing rings with equal diameters distributed along the axial direction are formed between the pole teeth and the outer cylindrical surface of the stationary ring.

The static rings 12 and 19 and the shell 23 are positioned by adopting a static ring outer cylindrical surface in the radial direction, the static rings are positioned by adopting an anti-rotating pin in the circumferential direction, the magnetic liquid sealing rings 11 and 20 for the static rings are embedded and fixed in the shell 23, and the radial sealing gaps between the

static rings

12 and 19 and the inner cylindrical surfaces of the pole shoe rings 27 of the magnetic liquid sealing rings 11 and 20 for the static rings are constant.

In operation, the rotating ring 16 rotates in a counterclockwise direction as viewed in fig. 3, this combination non-contact double-ended seal, the outer diameter side of the sealing end face of the movable ring is provided with a spiral groove, along with the rotation of the movable ring, blocking fluid, namely argon in the spiral groove 28 is accelerated by a concave surface 32 of the spiral groove to be high-speed fluid, the blocking fluid flows to the root of the spiral groove along the spiral groove, along with the gradual reduction of the circulation section of the spiral groove, the number of fluid molecules flowing on a unit circulation section is increased, the fluid pressure is further improved, on the other hand, the fluid in the spiral groove enters a collecting ring groove with a wide circulation section of the fluid on the sealing end face of the stationary ring after flowing through the root of the spiral groove with the narrowest circulation section, the fluid speed is suddenly reduced, partial, thereby forming opening force between the sealing end surfaces of the dynamic and static rings, separating the dynamic and static rings and avoiding the friction and abrasion caused by the direct contact of the dynamic and static rings; meanwhile, the rotating ring rotates to form circumferential shearing force of fluid between the sealing end faces, and the fluid on one side of the sealing end faces is prevented from flowing to the other side under the action of pressure difference, so that the purpose of sealing is achieved. The fluid wedged into the spiral groove from the blocking fluid cavity flows into the collecting ring groove on the sealing end face of the static ring after flowing through the root of the spiral groove with the narrowest flow cross section, and flows back to the blocking fluid cavity through the drainage hole channel under the action of pressure difference to form a one-time self-pumping cycle.

The magnetic force generating mechanism of the inner diameter side part of the combined non-contact double-end-face seal generates a uniform and stable magnetic field between the two seal rings, and the magnetic liquid 25 is adsorbed on the surface of the pole shoe ring to form a ring of magnetic liquid O-shaped rings which are radially arranged along the end face of the seal ring.

In the self-pumping circulation process, the blocking medium is continuously pumped and circulated, and the circulating fluid can effectively cool the sealing end face and the magnetic liquid, so that a proper working environment is created for the magnetic liquid sealing, the performance of the magnetic liquid is favorably ensured, and the zero-leakage sealing is realized.

Knowing that the high-efficiency operation rotating speed of a certain type of molten salt reactor nuclear main pump is 600r/min, assuming that the blocking fluid pressure is 0.2MPa and the pump cavity sealing medium pressure is 0.05MPa, the sealing end surface of a movable ring is provided with logarithmic spiral grooves, the number of the grooves is 40, the spiral angle is 22 degrees, the groove surface width ratio is 0.5, the groove aspect ratio is 0.5, the spiral groove depth is 40 mu m, and the film thickness is 1.2 mu m; the sealing end face of the static ring is provided with a ring groove and an axial and radial combined hole, the width of the ring groove is 3mm, and the depth of the ring groove is 800 mu m; the self-pumping mechanical seal is operated in a pumping mode, and the pressure at the root of the spiral groove is calculated to be 0.208 MPa.

And selecting a certain type of magnetic force mechanism below to calculate the pressure bearing capacity of the magnetic force mechanism. The permanent magnet is selected to be neodymium iron boron G45EH and residual magnetism B_fthe/T is 1.28-1.36, and the intrinsic coercivity is 2387H_cj/kA·m^-1Coercive force 971H_cB/kA·m^-1Maximum magnetic energy product 318 ~ 358(BH)_max/kA·m^-3(ii) a Magnetic liquid model MF01 (manufactured by Beijing university of transportation, Lidelhi. magnetic liquid sealing theory and application [ M]Beijing: scientific Press 2010), the base fluid was engine oil, the saturation magnetization Ms was 450Gs, and the density was 1.23 (kg/m)³)×10³Viscosity 20(25 ℃ C.)/cP, initial permeability μ₀Is 0.8 m/H; the tooth width a of the pole teeth on the end face of the pole shoe is 1mm, the gap g between the pole teeth and the seal dam face of the movable ring is 0.2mm, and the edge magnetic flux range is 2 g.

Simplifying pole shoes, using a pole tooth magnetic field segmentation model shown in figure 12 to calculate magnetic pressure drop, dividing a magnetic field into 5 magnetic flux tubes according to a graph, wherein the magnetic flux tubes comprise a rectangular magnetic flux tube I, four 1/4 cylinders II, four 1/4 hollow cylinders III, four 1/8 spheres IV and four 1/8 hollow spheres V, and calculating the magnetic pressure drop F of each magnetic flux tube respectively_g。

Rectangular flux tube I:

1/4 Cylinder II:

1/4 hollow cylinder III:

1/8 sphere IV:

1/8 hollow sphere V:

total magnetic pressure drop:

F_g＝F_g1+4×(F_g2+F_g3+F_g4+F_g5)

magnetic field under tooth is strongest

Magnetic field weakest under the bath

The ultimate sealing differential pressure of any stage is Δ P_max＝M_s(B_max-B_min)

Realize according to this scheme moving, quiet ring seal end face radial seal's pole shoe structure, respectively have 4 utmost point teeth about the pole shoe, eight grades of utmost point teeth altogether, tooth width 1mm, utmost point tooth and rotating ring seal dam facing clearance 0.2mm, then:

F_g＝0.0121

ΔP＝NM_s(B_max-B_min)＝0.25MPa

as shown in fig. 6, according to the projection range of the pole shoe on the seal end face of the rotating ring, it can be known that the pressure applied to the inner diameter of the pole shoe is the pump cavity seal medium pressure, i.e., P1 is 0.05MPa, the pressure applied to the outer diameter of the pole shoe is approximately equal to the pressure applied to the root of the spiral groove, i.e., P2 is 0.208MPa, the difference between the inner diameter and the outer diameter of the pole shoe, P1-P2, is 0.158MPa, and the magnetic mechanism at the seal end face of the seal ring can meet the seal pressure requirement because the sealing capacity Δ P of the magnetic mechanism is 0.25MPa > 0.158 MPa; similarly, under the condition of the same pole shoe structure parameters, the sealing pressure of the two magnetic liquid sealing rings for the static ring can also reach 0.25MPa, which is greater than the blocking fluid pressure by 0.2MPa, and the static sealing requirement can be met.

The control equation is a nonlinear partial differential equation, cannot be solved, and can be solved numerically by using FLUENT software, so that the pressure distribution of the end face flow field is obtained. Under the same operation condition, calculating the pressure values of the inner diameter side of the spiral groove corresponding to n different sealing cavity blocking fluid pressures, and obtaining the relation between the blocking fluid pressure y and the pressure x of the inner diameter side of the spiral groove through discrete point quadratic polynomial fitting: y ═ a + b₁x+b₂x²Wherein a is-7952.50798 + -2.32815, b₁＝0.99996±2.42135×10^-5， b₂＝-1.06858×10^-10±5.76379×10^-11。

Analysis shows that when the working pressure of the pump cavity is 0.05MPa, the blocking fluid pressure is considered to be at least larger than the pressure of the sealing medium, so that the combined seal can be ensured to be safe and effective as long as the blocking fluid pressure does not exceed the range of 0.05MPa to 0.292 MPa.

Claims

1. The utility model provides a combined non-contact double end face seals based on magnetic fluid seal and fluid dynamic pressure mechanical seal sets up between rotary equipment's casing and pivot, includes rotating ring (16), quiet ring (12, 19), O shape circle (15) for the rotating ring, magnetic fluid sealing circle (11, 20) for the quiet ring, permanent magnet (13, 17), pole shoe (14, 18), spring (10, 21) and end cover (9, 22), casing (23), axle sleeve (6), holding screw (7), characterized by: the combined non-contact double-end-face seal consists of a pumping type hydrodynamic mechanical seal and a magnetic liquid seal, wherein the magnetic liquid seal is arranged in the middle of a sealing dam of the self-pumping hydrodynamic mechanical seal;

the upper end face and the lower end face of the movable ring (16) are movable ring sealing end faces, each movable ring sealing end face is provided with a groove platform area and a sealing dam, the groove platform areas are distributed on the outer diameter side of the end face, the sealing dams (30) are distributed on the inner diameter side portion of the end face, 3 groups or more than 3 groups of uniformly distributed spiral grooves (28) are formed in the groove platform areas, sealing surfaces among the spiral grooves form a sealing weir (29), the groove walls on the two sides of each spiral groove (28) are convex (31) on one side and concave (32) on the other side, and the upper end face and the lower end face of the movable ring (16) are symmetrically arranged by the middle section M;

the sealing end surfaces of the static rings (12 and 19) are provided with a flow collecting ring groove (34) and a magnetic force generating mechanism, the flow collecting ring groove (34) is positioned on the outer diameter side of the sealing end surface, the flow collecting ring groove (34) is communicated with the blocked fluid cavity through a drainage pore passage (33), and the magnetic force generating mechanism is positioned on the inner diameter side of the sealing end surface;

the annular permanent magnets (13, 17) are embedded into the pole shoes (14, 18) to form a magnetic force generating mechanism, the magnetic force generating mechanism is embedded into a magnetic force mechanism mounting ring groove formed in the sealing end faces of the static rings (12, 19) to form a whole with the static rings, annular pole teeth and tooth grooves distributed at equal intervals along the radial direction are formed in the end faces of the pole shoes (14, 18), all pole teeth of the pole shoes face the sealing end faces of the static rings (12, 19), and the pole tooth end faces of the pole shoes (14, 18) are 0.05-0.2 mm lower than the sealing end faces of the static rings (12, 19) after assembly;

magnetic liquid is injected into the pole teeth of the pole shoes (14, 18), the magnetic liquid is adsorbed on the end faces and the periphery of the pole teeth of the pole shoes under the action of magnetic force, and magnetic liquid sealing rings with different diameters distributed along the radial direction are formed between the pole teeth and the middle part of the movable ring sealing dam;

when the movable ring (16) and the static rings (12 and 19) are relatively static, under the action of spring force, two sealing end faces of the movable ring (16) and the static rings (12 and 19) are tightly attached, and an initial gap d between the pole teeth of the pole shoes (14 and 18) and the sealing end faces of the static rings (12 and 19) is 0.05-0.2 mm, namely a static magnetic liquid sealing gap d; at the moment, the contact seal formed by the seal end face of the static ring and the seal dam face of the dynamic ring and the magnetic liquid seal jointly act to prevent fluid leakage;

when the movable ring (16) and the static rings (12, 19) rotate relatively, the spiral groove (28) on the end surface of the movable ring (16) pumps blocking fluid to generate end surface opening force, the sealing end surfaces are separated, the end surface opening distance delta formed by fluid dynamic pressure is 3-5 mu m at the moment, and the distance d between the pole shoe (14, 18) and the end surface of the static rings (12, 19) is 0.05-0.2 mm, so that a magnetic liquid sealing gap d + delta in a running state is formed; along with the operation of the pumping type fluid dynamic pressure mechanical seal, fluid is blocked to be continuously pumped and circulated, the friction heat of the end face is taken away, the sealing end face is effectively cooled, and the temperature of the magnetic liquid is reduced; and zero leakage of the sealing end face is ensured under the combined action of the pumping-in type fluid dynamic pressure mechanical seal and the magnetic liquid seal.

2. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: axle sleeve (6), O shape circle (8) for the axle sleeve, rotating ring (16), quiet ring (19), quiet ring enclose into the working medium chamber with magnetic liquid sealing washer (20) and rotary equipment's casing (23) and pivot (3), and working medium intracavity lower part is the high temperature fused salt, and upper portion is the protection argon gas, blocks the fluid and also is argon gas, blocks the settlement scope of fluid pressure: the minimum pressure is the pressure of the sealed medium in the rotating equipment, and the maximum pressure is the sum of the sealing pressure of the magnetic liquid and the pressure of the sealed medium in the rotating equipment.

3. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: one side of each pole shoe (14, 18) facing the sealing end face is radially provided with two sets of polar teeth and tooth grooves which are arranged at intervals, each set is provided with 3-5 polar teeth which are arranged in the radial direction, the tooth width is 0.5-2 mm, and the groove width is 0.5-2 mm; the permanent magnets (13, 17) are magnetized in the radial direction.

4. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: the outer diameter of the collecting ring groove (34) is larger than the diameter of the root circle of the spiral groove (28) on the end face of the corresponding movable ring (16), the inner diameter of the collecting ring groove (34) is smaller than or equal to the diameter of the root circle of the spiral groove (28), and the ring width of the collecting ring groove (34) is equal to the diameter of the drainage hole channel (33).

5. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: the outer diameter of the magnetic force generating mechanism is smaller than the inner diameter of the collecting ring groove (34), and the inner diameter of the magnetic force generating mechanism is larger than the inner diameter of the sealing end faces of the static rings (12 and 19).

6. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: the movable ring (16) and the static rings (12, 19) and the end covers (9, 22) on the two sides of the movable ring are sleeved on the shaft sleeve (6) in a penetrating way; the shaft sleeve (6) and the rotating shaft are fixed through a set screw (7), and the shaft sleeve (6) and the rotating shaft are sealed by an O-shaped ring (8); an O-shaped ring (15) is used for sealing between the movable ring (16) and the shaft sleeve (6); the back of the static ring sealing end face is respectively supported with more than 3 springs (10, 21), the other ends of the springs act on end covers (9, 22), the end covers (9, 22) are fixedly connected with a shell (23) of the rotary equipment, and the required end face specific pressure is obtained between the dynamic ring sealing end face and the static ring sealing end face.

7. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: the movable ring (16) is connected with the shaft sleeve (6) through threads (24), the rotation direction of the threads is opposite to the rotation direction of the rotating shaft, the movable ring (16) and the shaft sleeve (6) are positioned by adopting the outer cylindrical surface of the shaft sleeve (6) in the radial direction, and are positioned by adopting the end surface of a shaft shoulder on the shaft sleeve (6) in the axial direction.

8. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: the magnetic liquid sealing rings (11, 20) for the static rings between the static rings (12, 19) and the shell (23) are composed of pole shoe rings (27) and permanent magnet rings (26), and the radial gap between the inner cylindrical surface of each pole shoe ring (27) and the outer cylindrical surface of each static ring is 0.05-0.2 mm.

9. A combined non-contact double end-face seal based on magnetic liquid seal and hydrodynamic mechanical seal, as claimed in claim 1, wherein: the static rings (12 and 19) and the shell (23) are positioned by adopting the outer cylindrical surface of the static ring in the radial direction, the static rings are positioned by adopting the anti-rotating pins in the circumferential direction, the magnetic liquid sealing rings (11 and 20) for the static rings are embedded and fixed in the shell (23), and the radial sealing gap between the outer cylindrical surfaces of the static rings (12 and 19) and the inner cylindrical surface of the pole shoe rings (27) of the magnetic liquid sealing rings (11 and 20) for the static rings is constant.