WO2021004376A1 - 一种用于熔盐堆核主泵的组合型非接触式双端面密封 - Google Patents

一种用于熔盐堆核主泵的组合型非接触式双端面密封 Download PDF

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WO2021004376A1
WO2021004376A1 PCT/CN2020/100010 CN2020100010W WO2021004376A1 WO 2021004376 A1 WO2021004376 A1 WO 2021004376A1 CN 2020100010 W CN2020100010 W CN 2020100010W WO 2021004376 A1 WO2021004376 A1 WO 2021004376A1
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WIPO (PCT)
Prior art keywords
ring
sealing
seal
face
static
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PCT/CN2020/100010
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English (en)
French (fr)
Inventor
孙见君
马晨波
葛诚
全琴
马琳博
於秋萍
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南京林业大学
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Priority claimed from CN201910607393.5A external-priority patent/CN110185653B/zh
Priority claimed from CN201921047622.4U external-priority patent/CN210343823U/zh
Application filed by 南京林业大学 filed Critical 南京林业大学
Publication of WO2021004376A1 publication Critical patent/WO2021004376A1/zh

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/16—Sealings between relatively-moving surfaces
    • F16J15/34—Sealings between relatively-moving surfaces with slip-ring pressed against a more or less radial face on one member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/16—Sealings between relatively-moving surfaces
    • F16J15/40—Sealings between relatively-moving surfaces by means of fluid
    • F16J15/43—Sealings between relatively-moving surfaces by means of fluid kept in sealing position by magnetic force

Definitions

  • This patent belongs to the technical field of mechanical seals, involving self-pumping fluid dynamic pressure mechanical seals and magnetic liquid sealing technologies, and is particularly suitable for sealing between the rotating shaft and the housing of a gas-protected pump or compressor.
  • Figure 1 is a schematic diagram of the primary circuit molten salt pump of the molten salt reactor.
  • the upper part of the free surface of the liquid molten salt in the shell of the molten salt pump is filled with argon gas.
  • a heat shield is installed at a certain height from the molten salt surface, and a mechanical seal is installed above the heat shield to prevent the medium in the pump cavity from leaking along the shaft. This design avoids direct contact between the seal and molten salt with a temperature as high as 700°C, and eliminates many harsh restrictions on the material and structure of the sealing device.
  • the molten salt pump draws on the third-level seal of light water reactors (including pressurized water reactors and boiling water reactors), heavy water reactors, and graphite gas-cooled reactors, that is, using lubricating oil as a double-end mechanical seal for blocking fluid or using gas It is used as a dry gas seal to block fluid to achieve sealing.
  • light water reactors including pressurized water reactors and boiling water reactors
  • heavy water reactors including pressurized water reactors and boiling water reactors
  • graphite gas-cooled reactors that is, using lubricating oil as a double-end mechanical seal for blocking fluid or using gas It is used as a dry gas seal to block fluid to achieve sealing.
  • the end face friction and wear caused by the relative rotation between the moving ring and the static ring of the mechanical seal, as well as the aging of the auxiliary seal O-ring will cause the mechanical seal to fail; in this case, the mechanical seal needs to be replaced or disassembled for maintenance. Since the currently used mechanical seals are all integral, the matching parts of
  • US 3782737 reports a low leakage spiral groove seal that can be used for a variety of liquids such as water, sodium or oil.
  • the channel on the static ring is used to introduce the working fluid (lubricant) to the groove area of the sealing surface.
  • the working fluid lubricant
  • the moving ring rotates, the automatic pumping action of the spiral groove causes the liquid to flow to the sealed cavity, and as the circulation interface of the spiral groove increases, the fluid flow rate decreases and the fluid dynamic pressure increases, which seems to overcome the cleanliness of the working fluid by the mechanical seal
  • the static ring channel is intermittently connected with the spiral groove.
  • the fluid dynamic pressure is in a pulsating state, which is not conducive to the stable operation of the mechanical seal.
  • ZL 201310201473.3 proposes a self-pumping fluid dynamic pressure type mechanical seal, which realizes the self-lubrication and self-washing of the sealing end surface through the circulation of the sealing medium between the sealing end surface and the seal cavity to ensure the seal
  • the stability and longevity of the pump-out self-pumping fluid dynamic pressure type mechanical seal is required to provide blocking liquid in order to form sufficient opening force to reduce the friction and wear between the dynamic and static rings, and when the blocking fluid is pumped out
  • the low-pressure zone formed at the root of the groove is not conducive to sealing the argon on the inner diameter side of the sealing surface.
  • the main pump seal of molten salt reactor core is under the working conditions of low pressure difference and low temperature, which is suitable for the application of magnetic liquid sealing technology.
  • the magnetic liquid seal has a long life, high reliability, self-adaptive structure, zero leakage, simple structure, and convenient use, but its sealing ability is highly sensitive to the sealing gap, which greatly limits the magnetic liquid sealing technology at the upper end of the shaft 3 as an end surface stop.
  • the lower end of the thrust bearing 2 is used on the main pump of the molten salt reactor core with the guide sliding bearing 4 (see Figure 1); the radial beating of the rotating shaft causes the magnetic liquid radial sealing gap to change continuously, which destroys the stability and integrity of the magnetic liquid film Sex.
  • ZL 201410614383.1 proposed an axially sealed magnetic fluid lubrication mechanical seal device.
  • the device is equipped with a controllable magnetic field generator outside the mating surfaces of the moving and static rings to form a magnetic field between the sealing interface of the moving and static rings.
  • the size of the magnetic field is changed by adjusting the voltage.
  • the magnetic liquid on the outer diameter side of the sealing surface is wedged into the spiral groove by the rotation of the spiral groove opened on the moving ring to form a dynamic pressure, and a controllable magnetic liquid sealing liquid film is formed on the sealing interface.
  • Leakage on the other hand, separate the dynamic and static rings to avoid friction and wear and achieve long-life operation.
  • the particles in the magnetic liquid on the sealing interface will increase the wear of the dynamic and static ring seal end faces during the start and stop process; the second is that the magnetic liquid fills the entire sealing interface during stable operation. If the gap between the sealing end faces suddenly decreases, the magnetic fluid will be squeezed out of the sealing interface, suspended on the edge of the inner and outer diameters of the sealing surface, or even thrown or splashed directly into the pump cavity, contaminating the molten salt medium and causing accidents;
  • the relative motion of the static and dynamic rings makes the magnetic fluid at the sealing interface and the viscous shear force friction and heat, and accumulate and heat up. The increase in temperature will not only cause the seal ring to deform, but also cause the magnetic force to drop. , Affect the sealing ability of the magnetic liquid seal.
  • This patent aims to provide a combined non-contact double end seal for the main pump of molten salt reactor nuclear, which is used as the seal between the shaft and shell of the main pump of molten salt reactor to ensure the shaft seal of the molten salt pump. Zero leakage and long-term safe and stable operation.
  • a combined non-contact double end seal for the main pump of the molten salt reactor nuclear which is arranged between the casing of the rotating equipment and the rotating shaft, and includes the moving ring 16, the static ring 12, and 19 , O-ring 15 for moving ring, magnetic liquid sealing ring for static ring 11, 20, permanent magnet 13, 17, pole piece 14, 18, spring 10, 21 and end cover 9, 22, shell 23, sleeve 6 , Set screw 7;
  • the combined non-contact double end face seal is composed of a "pump-in" fluid dynamic pressure mechanical seal and a magnetic fluid seal.
  • the magnetic fluid seal is set in the middle of the sealing dam of the self-pumping fluid dynamic pressure mechanical seal;
  • the upper and lower ends of the moving ring 16 are the sealing end surfaces of the moving ring, and each sealing end surface of the moving ring is provided with a groove platform area and a sealing dam.
  • the groove platform area is distributed on the outer diameter side of the end surface, and the sealing dam 30 is distributed on the inner diameter side of the end surface.
  • the groove platform area is provided with 3 groups or more than 3 groups of spiral grooves 28 evenly distributed.
  • the sealing surface between the spiral grooves constitutes a sealing weir 29.
  • the groove walls on both sides of the spiral groove 28 have a convex surface 31 on one side and the other The side is a concave surface 32, and the upper and lower ends of the movable ring 16 are arranged symmetrically with the cross section M-M of the movable ring;
  • the sealing end faces of the static rings 12 and 19 have a collecting ring groove 34 and a magnetic force generating mechanism.
  • the collecting ring groove 34 is located on the outer diameter side of the sealing end surface.
  • the drainage hole 33 connects the collecting ring groove 34 with the blocking fluid cavity.
  • the magnetic force generating mechanism Located on the inner diameter side of the sealing end face;
  • the annular permanent magnets 13, 17 are embedded in the pole shoes 14, 18 to form a magnetic force generating mechanism, and the magnetic force generating mechanism is embedded in the magnetic mechanism mounting ring groove opened on the sealing end surface of the static ring 12, 19 to form an integral body with the static ring.
  • the end faces of 14, 18 are provided with annular pole teeth and tooth grooves distributed at equal intervals in the radial direction. All the pole teeth of the pole shoes face the sealed end faces of the static rings 12 and 19, and the pole teeth end faces of the pole shoes 14, 18 are lower than the static ring after assembly 12.19
  • the sealing end face is 0.05 ⁇ 0.2mm;
  • the pole teeth of the pole shoes 14 and 18 are filled with magnetic liquid.
  • the magnetic liquid is adsorbed on and around the pole teeth end surface of the pole shoes under the action of magnetic force, forming a radial direction between the pole teeth and the middle of the moving ring seal dam.
  • the initial gap d of the sealing end face is 0.05 ⁇ 0.2mm, that is, the magnetic liquid sealing gap d in the static state; at this time, the contact seal formed by the static ring seal end face and the sealing dam surface of the moving ring and the magnetic fluid seal work together to prevent fluid leakage;
  • the shaft sleeve 6, the O-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 casing 23 of the rotating equipment and the rotating shaft 3 are enclosed to form a working fluid cavity, and the lower part of the working fluid cavity It is a high-temperature molten salt, the upper part is protective argon gas, and the blocking fluid is also argon gas.
  • the setting range of the blocking fluid pressure the minimum pressure is the pressure of the sealed medium in the rotating equipment, and the maximum pressure is the magnetic liquid sealing pressure and the pressure inside the rotating equipment. The sum of the pressure of the sealing medium.
  • the pole shoes 14 and 18 are radially provided with two sets of pole teeth and tooth grooves arranged at intervals on the side facing the sealing end surface, each group has 3 to 5 pole teeth arranged in a radial direction, and the tooth width is 0.5 to 2 mm.
  • the slot width is 0.5-2mm; the permanent magnets 13, 17 are magnetized in the radial direction.
  • the outer diameter of the collecting ring groove 32 on the end surfaces of the stationary rings 12 and 19 is greater than the groove root diameter of the spiral groove 28 on the end surface of the moving ring 16, and the inner diameter is less than or equal to the groove root diameter of the spiral groove 28, and the collecting ring groove 34
  • the ring width of is equal to the diameter of the drainage channel 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 moving ring 16 and the static rings 12, 19, and end caps 9, 22 on both sides of the moving ring 16 are all threaded and sleeved on the shaft sleeve 6; the shaft sleeve 6 and the rotating shaft are fixed by a set screw 7, and the shaft sleeve 6 and the rotating shaft are used between
  • the O-ring 8 is sealed; the moving ring 16 and the shaft sleeve 6 are sealed with an O-ring 15; the back of the static ring seal end surface respectively supports more than 3 springs 10, 21, and the other end of the spring acts on the end cover 9,
  • the end caps 9, 22 are fixedly connected to the housing 23 of the rotating equipment, so that the required end surface pressure can be obtained between the sealing end surface of the moving ring and the sealing end surface of the static ring.
  • the moving ring 16 and the shaft sleeve 6 are connected by a thread 24.
  • the thread rotation direction is opposite to the rotation direction of the shaft.
  • the radial direction of the moving ring 16 and the shaft sleeve 6 is positioned by the outer cylindrical surface of the shaft sleeve 6, and the axial direction is used on the shaft sleeve 6. Positioning of shaft shoulder end face.
  • the magnetic liquid seal rings 11 and 20 between the static rings 12, 19 and the housing 23 are composed of a pole shoe ring 27 and a permanent magnet ring 26.
  • the diameter between the inner cylindrical surface of the pole shoe ring 27 and the outer cylindrical surface of the static ring The gap is 0.05 ⁇ 0.2mm.
  • the static rings 12, 19 and the housing 23 are positioned on the outer cylindrical surface of the static ring in the radial direction, and anti-rotation pins are used in the circumferential direction.
  • the static ring is embedded and fixed in the housing 23 with magnetic liquid sealing rings 11, 20, and the static ring 12
  • the radial sealing gap between the outer cylindrical surface of, 19 and the inner cylindrical surface of the pole shoe ring 27 of the static ring magnetic liquid sealing ring 11, 20 is constant.
  • the working principle of the "pump-in” hydrodynamic mechanical seal is that the end face of the dynamic ring seal is provided with spiral grooves, and the end face of the static ring seal is provided with collecting ring grooves and drainage holes.
  • the moving ring rotates and pumps the blocked fluid through the spiral groove, and performs work through the concave surface of the spiral groove. On the one hand, it raises the fluid pressure and accelerates the fluid in the spiral groove into a high-speed fluid.
  • the spiral groove flows to the root of the spiral groove. As the circulation section of the spiral groove gradually decreases, the number of fluid molecules flowing through the unit circulation section increases, which further increases the fluid pressure.
  • the fluid in the spiral groove flows through the narrowest circulation section
  • the root of the spiral groove enters into the collector ring groove with a wide cross-section of fluid flow on the end face of the static ring seal.
  • the fluid velocity drops sharply, part of the fluid kinetic energy is converted into fluid dynamic pressure energy, and the fluid pressure is raised again, thereby forming an opening force between the dynamic and static ring seal end faces , Separate the dynamic and static rings to avoid friction and wear caused by direct contact between the dynamic and static rings; at the same time, the rotation of the dynamic ring creates a circumferential shear force of the fluid between the seal end faces, preventing the fluid on one side of the seal end face from flowing to the other side under the pressure difference to achieve the seal the goal of.
  • the fluid wedged from the blocked fluid cavity into the spiral groove flows through the root of the spiral groove with the narrowest flow cross section, then enters the collecting ring groove of the static ring seal end surface, and flows back to the blocked fluid cavity through the drainage hole under the action of the pressure difference. , Forming a self-pumping cycle again and again.
  • the continuous circulation of the fluid between the sealing end faces takes away the frictional heat between the sealing end faces in time, realizing the self-washing and self-cooling of the seal.
  • the working principle of the magnetic fluid seal the magnetic mechanism embedded in the sealing end faces of the static rings 12 and 19 and the moving ring form a magnetic circuit. Under the action of the magnetic field generated by the annular permanent magnet of the magnetic mechanism, the gap between the top of the pole shoe and the sealing end face of the moving ring The magnetic fluid is concentrated between the top of the pole tooth and the sealing dam surface of the moving ring to form an "O"-shaped liquid ring, which separates the axial gap between the sealing end surfaces of the moving and static rings into several independent closed annular chambers. , To prevent the fluid from one side of the sealed end face from flowing to the other side to achieve the purpose of sealing.
  • the pole teeth and the tooth grooves are arranged radially alternately, and the sealing pressure difference that the single-pole seal can bear is
  • M S is the saturation magnetization Is the maximum magnetic field induction intensity value under the tooth, Is the minimum magnetic field induction value under the groove, F g is the magnetic pressure drop of the sealing gap, ⁇ 0 is the initial permeability, g is the sealing gap, ⁇ is the inclination angle, and S is the groove width.
  • the magnetic liquid between the top of the pole tooth and the sealing dam surface of the moving ring will symmetrically gather on the middle diameter circumference of the top of the pole tooth to form a rectangular cross-section liquid ring;
  • the magnetic fluid is a liquid ring with an arcuate cross-section with a concave surface on the high pressure side and a convex surface on the low pressure side.
  • the elastic force generated to restore the original shape balances the pressure difference force;
  • the magnetic liquid ring gathered at the tip of the pole tooth begins to deform and then quickly perforates.
  • the sealed medium flows to the next stage through the pinhole; as the next stage
  • the pressure in the closed annular chamber increases, and the pressure difference between the inner and outer diameters of the magnetic liquid ring at the top of the pole tooth decreases.
  • the magnetic liquid reassembles under the action of the magnetic field generated by the annular permanent magnet of the magnetic mechanism, and the pinhole is healed. Return to working condition.
  • the contact seal formed by the static ring seal end face and the seal dam face of the moving ring works together with the magnetic liquid seal to prevent the fluid on one side of the seal end face from flowing to the other side under the action of the pressure difference to achieve the purpose of sealing;
  • the spiral groove 28 on the end surface of the moving ring 16 pumps the blocking fluid, generating an end surface opening force, and the sealing end surface is released.
  • the blocked fluid is constantly being pumped and circulated, taking away the frictional heat of the end face, effectively cooling the end face of the seal and reducing the temperature of the magnetic liquid; in the "pump-in” fluid dynamic pressure mechanical seal, the shear flow and the "O" shape of the magnetic liquid seal
  • the joint action of the liquid ring ensures that the fluid on both sides of the seal end face and the outer diameter does not leak from each other.
  • the magnetic liquid seal of the combined non-contact double end face seal is located on the sealing dam surface of the moving ring with a certain radial width, when the moving ring is affected by the rotation of the rotating shaft and produces radial displacement, it is attached to the top of the static ring pole tooth ,
  • the magnetic liquid ring axially close to the sealing dam surface of the moving ring shows a slight radial displacement relative to the moving ring, but the width of the sealing dam surface of the moving ring makes the magnetic liquid ring still maintain a complete "O"-shaped liquid ring.
  • the ground is located between the top of the pole teeth of the static ring and the sealing dam surface of the moving ring to provide sealing capability.
  • the sealing interface has no friction and has a long service life.
  • the self-pumped fluid dynamic pressure mechanical seal generates dynamic pressure, separates the dynamic ring and the static ring to form a non-contact seal, so that the dynamic and static rings have no friction and wear; the magnetic liquid seal is passed between the pole shoe and the sealing dam The magnetic liquid in the middle is sealed, and the pole shoes are not in contact with the sealing dam, and there is no friction and wear.
  • FIG 1 is a schematic diagram of the primary circuit sodium pump of the prototype sodium-cooled fast reactor (PFBR);
  • Figure 2 is a cross-sectional view of the sealing structure
  • Figure 3 is a structural diagram of the end face of the moving ring
  • Figure 4 is a structural diagram of the end face of the static ring
  • Figure 5 is a schematic diagram of the dynamic and static ring structure
  • Figure 6 is a perspective view of a magnetic force generating mechanism
  • Figure 7 is a schematic projection view of the magnetic mechanism on the sealing end surface of the moving ring
  • Figure 8 is a schematic diagram of the magnetic circulation line of the magnetic mechanism between the sealing end faces
  • Figure 9 is a schematic diagram of the magnetic liquid sealing gap in the closed state of the sealing end surface
  • Figure 10 is a perspective view of a magnetic liquid seal ring for stationary ring
  • Figure 11 is a schematic diagram of the magnetic circulation line of the magnetic mechanism of the magnetic liquid seal ring for the stationary ring;
  • Figure 12 is a pole tooth magnetic field segmentation model
  • Fig. 13 is a schematic diagram of the magnetic liquid sealing gap in an open state of the sealing end surface.
  • Figures 2-7 describe a combined non-contact double end seal based on a magnetic liquid seal and a fluid dynamic pressure type mechanical seal for the main pump of the molten salt reactor core, which is used to seal the main pump of the molten salt reactor core
  • the gap between the rotating shaft and the shell can ensure the zero leakage of the shaft seal of the molten salt pump and the long-term safe and stable operation.
  • the upper and lower end surfaces of the moving ring 16 are symmetrically arranged in the section M-M of the moving ring.
  • Each end surface includes a spiral groove 28, a sealing weir 29 and a sealing dam 30.
  • the spiral grooves 28 are evenly distributed on the outer diameter side of the end surface of the moving ring.
  • the inner diameter side of the end surface of the moving ring is a sealing dam 30, and the sealing surface between the spiral grooves 28 is a sealing dam 29.
  • the end faces of the stationary rings 12 and 19 are provided with a collecting ring groove 34 and a magnetic force generating mechanism (composed of permanent magnet 13, pole shoe 14 or permanent magnet 17, pole shoe 18).
  • the collecting ring groove 34 is located on the outer diameter side of the end surface, and the drainage hole 33 Evenly distributed in the collecting ring groove 34, the magnetic force generating mechanism is located on the inner diameter side of the end surface; wherein the outer diameter of the collecting ring groove 34 is larger than the groove root diameter of the spiral groove 28 of the moving ring end surface, and the inner diameter is less than or equal to the groove of the spiral groove 28
  • the diameter of the root circle, the ring width of the collecting ring groove 34 is equal to the diameter of the drainage hole 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 moving ring 16 and the shaft sleeve 6 are connected by a thread 24.
  • the thread rotation direction is opposite to the rotation direction of the shaft.
  • the radial direction of the moving ring 16 and the shaft sleeve 6 is positioned by the outer cylindrical surface of the shaft sleeve 6, and the axial direction is used on the shaft sleeve 6. Positioning of shaft shoulder end face.
  • the static rings 12, 19 and the housing 23 are sealed with magnetic liquid.
  • the permanent magnet ring 26 is embedded in the pole shoe ring 27 to form a magnetic force generating mechanism.
  • the magnetic force generating mechanism is embedded in the housing 23 to form an integral body with the housing 23.
  • the inner cylindrical surface of the pole shoe ring 27 is provided with two sets of poles distributed at equal intervals along the axial direction. Tooth and tooth grooves, all pole teeth of the pole shoe ring face the outer cylindrical surface of the stationary ring 12, 19, and the radial gap between the pole tooth end surface of the pole shoe ring 27 and the outer cylindrical surface of the stationary ring after assembly is 0.05-0.2mm.
  • the pole tooth of the pole shoe ring 27 is filled with magnetic liquid.
  • the magnetic liquid is adsorbed on the pole tooth end surface of the pole shoe ring 27 and its surroundings under the action of magnetic force, forming an axial distribution between the pole tooth and the outer cylindrical surface of the stationary ring.
  • Magnetic fluid sealing ring of equal diameter.
  • the static rings 12, 19 and the housing 23 are positioned on the outer cylindrical surface of the static ring in the radial direction, and anti-rotation pins are used in the circumferential direction.
  • the static ring is embedded and fixed in the housing 23 with magnetic liquid sealing rings 11, 20, and the static ring 12
  • the radial sealing gap between the outer cylindrical surface of, 19 and the inner cylindrical surface of the pole shoe ring 27 of the static ring magnetic liquid sealing ring 11, 20 is constant.
  • This combined non-contact double end seal has a spiral groove on the outer diameter side of the end surface of the moving ring.
  • the spiral groove 28 The blocked fluid, that is, the argon gas is accelerated by the concave surface 32 of the spiral groove into a high-speed fluid, and flows along the spiral groove to the root of the spiral groove.
  • the circulation section of the spiral groove gradually decreases, the number of fluid molecules flowing through the unit circulation section increases and further increases. Fluid pressure, on the other hand, the fluid in the spiral groove flows through the root of the spiral groove with the narrowest circulation cross section and then enters the collector ring groove on the end face of the static ring seal.
  • the fluid velocity drops sharply, and part of the fluid kinetic energy is converted into fluid motion.
  • the pressure energy increases the fluid pressure again, thereby forming an opening force between the sealing end faces of the dynamic and static rings, separating the dynamic and static rings to avoid friction and wear caused by direct contact between the dynamic and static rings; at the same time, the rotation of the dynamic ring creates a circumferential shear force of the fluid between the sealing end faces to prevent the seal
  • the fluid on one side of the end face flows to the other side under the action of the pressure difference to achieve the purpose of sealing.
  • the fluid wedged from the blocked fluid cavity into the spiral groove flows through the root of the spiral groove with the narrowest flow cross section, then enters the collecting ring groove of the static ring seal end surface, and flows back to the blocked fluid cavity through the drainage hole under the action of the pressure difference. , Forming a self-pumping cycle again and again.
  • the magnetic force generating mechanism on the inner diameter side of the combined non-contact double end face seal generates a uniform and stable magnetic field between the two seal rings.
  • the magnetic fluid 25 is adsorbed on the surface of the pole shoe ring to form a circle arranged radially along the end face of the seal ring Magnetic fluid "O-ring”.
  • the blocking medium is continuously pumped and circulated.
  • the circulating fluid can effectively cool the sealing end face and the magnetic liquid, creating a suitable working environment for the magnetic liquid seal, helping to ensure the performance of the magnetic liquid and achieving "zero "Leak” sealed.
  • the high-efficiency operating speed of a certain type of molten salt reactor nuclear main pump is 600r/min. It is assumed that the blocking fluid pressure is 0.2MPa, the pump chamber sealing medium pressure is 0.05MPa, the sealing end face of the moving ring is provided with logarithmic spiral grooves, the number of grooves is 40, and the helix angle is 22.
  • base fluid is engine oil
  • the saturation magnetization Ms is 450Gs
  • the density is 1.23 (kg/m 3 ) ⁇ 10 3
  • the viscosity is 20 25°C)/cP
  • the magnetic field is divided into 5 types of flux tubes.
  • F g F g1 +4 ⁇ (F g2 +F g3 +F g4 +F g5 )
  • a pole shoe structure with radial sealing of the dynamic and static ring seal end faces is realized.
  • the magnetic mechanism on the end face of the sealing ring can be realized Sealing pressure requirements; in the same way, the sealing pressure of the two static ring magnetic liquid sealing rings can reach 0.25MPa under the same pole shoe structure parameters, which is greater than the blocking fluid pressure 0.2MPa, which can meet the static sealing requirements.

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  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Sealing Using Fluids, Sealing Without Contact, And Removal Of Oil (AREA)

Abstract

一种用于熔盐堆核主泵的组合型非接触式双端面密封，以保证熔盐泵轴封的零泄漏和长周期安全稳定运行。组合型非接触式双端面密封设置于旋转设备的壳体与转轴之间，由"泵入式"流体动压机械密封和磁性液体密封组成，动环（16）的上下两端面为动环密封端面，每一动环密封端面都设有槽台区和密封坝，槽台区开设有均布的螺旋槽（28）；集流环槽（34）位于动环密封端面外径侧，引流孔道（33）将集流环槽（34）与阻塞流体腔连通，磁力发生机构位于动环密封端面内径侧部位；动环（16）与静环（12,19）相对转动时，螺旋槽（28）泵入阻塞流体，产生端面开启力，密封端面脱开，此时流体动压形成的端面开启距离δ加上极靴（14,18）距静环（12,19）端面的距离d，构成运转状态磁性液体密封间隙d+δ。

Description

一种用于熔盐堆核主泵的组合型非接触式双端面密封 技术领域
本专利属于机械密封技术领域，涉及自泵送流体动压机械密封和磁性液体密封技术，特别适用于气体保护泵或压缩机的转轴与壳体之间的密封。
背景技术
本世纪以来，由于世界范围内的能源和资源紧缺程度日趋严重，温室气体效应等相关环境问题日益突出，因此寻求可持续、安全稳定且环境友好的能源受到了各国关注。2002年第四代核能国际论坛(GIF)政策组发布了技术路线图，提出了几乎为所有核能国家所接受的6种堆型，其中3种分别是钠冷快堆、铅冷快堆和气冷快堆，另3种是超高温堆、超临界水堆和熔盐堆。其中，熔盐堆因效率高、废弃物排放少、在堆芯区域压力低等优点备受世界各国关注。
图1为熔盐堆的一回路熔盐泵简图。熔盐泵外壳内液态熔盐的自由液面上部充满氩气，在距离熔盐液面一定高度处设置热屏，在热屏上方安装机械密封，放止泵腔内介质沿转轴而泄漏。这种设计形式避免了密封与温度高达700℃的熔盐直接接触，消除了密封装置对材料、结构等方面的诸多苛刻限制。
按照现有技术，熔盐泵借鉴轻水堆(包括压水堆和沸水堆)、重水堆、石墨气冷堆的第3级密封，即采用润滑油作阻塞流体的双端面机械密封或采用气体作阻塞流体的干气密封来实现密封。然而，机械密封动环、静环之间的相对转动产生的端面摩擦磨损，以及辅助密封O型圈的老化，都会导致机械密封失效；这种情况下，就需要更换或拆卸维修机械密封。由于现行使用的机械密封均为整体式的，在更换易损件时必须拆卸轴端的配合件，工程量大、耗时长、费用高，因此，自90年代就有人开始研究剖分式机械密封，期待以此取而代之。然而，密封环的剖分面和剖分式O形圈的接头的密封可靠性，难以在工作条件下得到保证。为此，人们试图采用流体动压机械密封来解决接触式机械密封的寿命短以及剖分式机械密封的可靠度低的问题，但以牺牲密封性能换取寿命的流体动压机械密封，无法满足熔盐堆核主泵的零泄漏的要求。
US 3782737报道了一种可用于多种液体如水、钠或油的低泄漏螺旋槽密封，利用静环上的通道将工作流体(润滑液)引入至密封面的槽台区，当带有螺旋槽的动环旋转时，螺旋槽的自动泵送作用使得液体流向密封腔，并随着螺旋槽流通界面的增大流体流速降低而转化为流体动压的提升，似乎克服了机械密封对工作流体洁净度的敏感性，但静环通道与 螺旋槽间隙性连通，一方面使得流体动压呈脉动状态，不利于机械密封的稳定运行，另一方面导致静环通道进入的流体间隙性流入密封面的堰区，引发密封面磨损；ZL 201310201473.3提出了一种自泵送流体动压型机械密封，通过密封介质在密封端面和密封腔之间循环，实现了密封端面自润滑、自冲洗，保证了密封的稳定性和长久性，但泵出式自泵送流体动压型机械密封工作时，需要提供阻塞液体以便形成足够的开启力，减小动静环之间的摩擦磨损，而泵出阻塞流体时在型槽根部形成的低压区，不利于实现对密封面内径侧氩气的密封。
熔盐堆核主泵密封所处的压差低、温度不高的工况条件，适合磁性液体密封技术的应用。磁性液体密封寿命长、可靠性高、结构自适应、零泄漏、结构简单、使用方便，但其密封能力对密封间隙的高度敏感性，极大地限制了磁性液体密封技术在转轴3上端为端面止推轴承2下端为导向滑动轴承4的熔盐堆核主泵上的运用(参见图1)；转轴的径向跳动使磁性液体径向密封间隙不断变化，破坏了磁性液膜的稳定性与完整性。ZL 201410614383.1提出了一种轴向密封的磁流体润滑机械密封装置，该装置在动、静环配合面外部设有可控磁场发生器，在动静环密封界面间形成磁场，通过调整电压改变磁场大小，利用开设在动环上的螺旋槽的旋转将密封面外径侧的磁性液体楔入到螺旋槽中形成动压，在密封界面形成可控的磁性液体密封液膜，一方面阻止密封介质的泄漏，另一方面分离动、静环，避免摩擦磨损，实现长寿命运行。但是，这种结构存在几个问题：一是启停过程中，密封界面上的磁性液体中的颗粒会加重动、静环密封端面的磨损；二是稳定运行过程中，磁性液体充满整个密封界面，如果密封端面间隙突然减小，必将导致磁性液体被挤压出密封界面，悬挂于密封面内外径的边缘，甚至被甩入或直接溅入泵腔，污染熔盐介质，引发事故；再者，相对运动的动静环，使得处于密封界面、黏性剪切力较大的磁性液体之间摩擦而生热，并集聚升温，温度的升高不仅会引起密封环变形，还会导致磁力下降，影响磁性液体密封的密封能力。
发明内容
本专利旨在提供一种用于熔盐堆核主泵的组合型非接触式双端面密封，用作熔盐堆核主泵转轴与壳体之间的密封，以保证熔盐泵轴封的零泄漏和长周期安全稳定运行。
本专利的技术解决方案是：一种用于熔盐堆核主泵的组合型非接触式双端面密封，设置于旋转设备的壳体与转轴之间，包括动环16、静环12、19、动环用O形圈15、静环用磁性液体密封圈11、20、永磁体13、17、极靴14、18、弹簧10、21和端盖9、22、壳体 23、轴套6、紧定螺钉7；组合型非接触式双端面密封由“泵入式”流体动压机械密封和磁性液体密封组成，磁性液体密封设置于自泵送流体动压机械密封的密封坝的中部；
所述动环16的上下两端面为动环密封端面，每一动环密封端面都设有槽台区和密封坝，槽台区分布在端面的外径侧，密封坝30分布在端面的内径侧部分，槽台区开设有均布的3组或3组以上的螺旋槽28，螺旋槽之间的密封面构成密封堰29，螺旋槽28的两侧槽壁，一侧为凸面31，另一侧为凹面32，动环16上下两端面结构以动环中截面M‐M对称布置；
所述静环12、19密封端面具有集流环槽34和磁力发生机构，集流环槽34位于密封端面外径侧，引流孔道33将集流环槽34与阻塞流体腔连通，磁力发生机构位于密封端面内径侧部位；
所述圆环形永磁体13、17嵌入极靴14、18内组合成磁力发生机构，磁力发生机构嵌入静环12、19密封端面开设的磁力机构安装环槽内与静环组成一体，极靴14、18端面开设有沿径向等间距分布的环形极齿和齿槽，极靴的所有极齿朝向静环12、19密封端面，并且装配后极靴14、18的极齿端面低于静环12、19密封端面0.05～0.2mm；
所述极靴14、18的极齿处注有磁性液体，磁性液体在磁力作用下吸附在极靴的极齿端面及其周围，在极齿与动环密封坝的中部之间形成沿径向分布的不同直径的磁性液体密封圈；
所述动环16与静环12、19相对静止时，在弹簧力作用下，动环16和静环12、19两密封端面紧密贴合，极靴14、18的极齿与静环12、19密封端面的初始间隙d＝0.05～0.2mm，即静止状态磁性液体密封间隙d；此时，静环密封端面与动环的密封坝面形成的接触密封与磁性液体密封共同作用阻止流体泄漏；
所述动环16与静环12、19相对转动时，动环16端面的螺旋槽28泵入阻塞流体，产生端面开启力，密封端面脱开，此时流体动压形成的端面开启距离δ＝3～5μm加上极靴14、18距静环12、19端面的距离d＝0.05～0.2mm，构成运转状态密封端面磁性液体密封间隙d+δ；随着“泵入式”流体动压机械密封运行，阻塞流体不断被泵送循环，带走端面摩擦热，有效冷却密封端面和降低磁性液体温度，为磁性液体密封创造适宜的工作环境；在“泵入式”流体动压机械密封和磁性液体密封的共同作用下，保证密封端面零泄漏。
所述轴套6、轴套用O形圈8、动环16、静环19、静环用磁性液体密封圈20和旋转设备的壳体23及转轴3围成工质腔，工质腔内下部是高温熔盐，上部为保护氩气，阻塞流体亦为氩气，阻塞流体压力的设定范围：最小压力为旋转设备内被密封介质的压力，最大压力为磁性液体密封压力与旋转设备内被密封介质的压力之和。
所述极靴14、18在朝向密封端面的一侧沿径向开设有两组间隔排列的极齿和齿槽，每组有径向排列的极齿3～5个，齿宽0.5～2mm，槽宽0.5～2mm；永磁体13、17沿径向充磁。
所述静环12、19端面上的集流环槽32的外径大于动环16端面螺旋槽28的槽根圆直径，内径小于或等于螺旋槽28的槽根圆直径，集流环槽34的环宽与引流孔道33的直径相等；
所述磁力发生机构的外径小于集流环槽34的内径，磁力发生机构的内径大于静环12、19密封端面的内径。
所述动环16及其两侧的静环12、19、端盖9、22均穿套在轴套6上；轴套6与转轴通过紧定螺钉7固定，轴套6与转轴之间用O形圈8密封；动环16与轴套6之间用O形圈15密封；静环密封端面的背面分别支撑有3个以上的弹簧10、21，弹簧的另一端作用在端盖9、22上，端盖9、22固定连接于旋转设备的壳体23，使动环密封端面与静环密封端面之间获得所需的端面比压。
动环16与轴套6之间通过螺纹24联接，螺纹旋向与转轴旋转方向相反，动环16与轴套6的径向采用轴套6外圆柱面定位，轴向采用轴套6上的轴肩端面定位。
静环12、19与壳体23之间的静环用磁性液体密封环11、20由极靴环27和永磁体环26组成，极靴环27内圆柱面与静环外圆柱面之间径向间隙0.05～0.2mm。
静环12、19与壳体23的径向采用静环外圆柱面定位，周向采用防转销定位，静环用磁性液体密封环11、20嵌入并固定在壳体23内，静环12、19外圆柱面与静环用磁性液体密封环11、20的极靴环27内圆柱面之间的径向密封间隙恒定。
“泵入式”流体动压机械密封工作原理：“泵入式”流体动压机械密封端面结构为动环密封端面上开设有螺旋槽，静环密封端面开设集流环槽和引流孔道。“泵入式”流体动压机械密封运行时，动环旋转，通过螺旋槽将阻塞流体泵入，并经螺旋槽凹面做功，一方面提升流体压力，同时加速螺旋槽内流体成高速流体，沿螺旋槽流向螺旋槽根部，随着螺旋槽流通截面的逐渐减小，流经单位流通截面上的流体分子数增多，进一步提升流体压力，另一方面，螺旋槽中的流体流经流通截面最窄的螺旋槽根部之后进入静环密封端面流体流通截面宽大的集流环槽，流体速度骤降，部分流体动能转化为流体动压能，再次提升流体压力，从而在动静环密封端面间形成开启力，分离动静环，避免动静环直接接触发生摩擦磨损；同时，动环旋转形成密封端面间流体周向剪切力，阻止密封端面的一侧流体在压差作用下向另一侧流动而达到密封的目的。从阻塞流体腔中楔入螺旋槽中的流体，流经流通截面最窄的螺旋槽根部之后进入静环密封端面的集流环槽，在压差的作用下经由引流孔道重 新流回阻塞流体腔，形成一次次自泵送循环。在自泵送循环过程中，流体在密封端面之间的不断循环把密封端面之间的摩擦热及时带走，实现了密封的自冲洗、自冷却。
磁性液体密封工作原理：嵌入静环12、19密封端面的磁力机构与动环构成磁性回路，在磁力机构的圆环形永磁体产生的磁场作用下，极靴顶端与动环密封端面缝隙间的磁流体被集中到极齿顶端与动环密封坝面间，形成一个个“O”形液环，将动、静环密封端面间的轴向缝隙分隔成几个独立不连通的密闭环形腔室，阻止密封端面的一侧流体向另一侧流动而达到密封的目的。
在环形极靴上，极齿与齿槽沿径向相间排布，单极密封能承受的密封压差为
Δp max＝M S(B max-B min)
式中，M S为饱和磁化强度
Figure PCTCN2020100010-appb-000001
为齿下最大磁场感应强度值，
Figure PCTCN2020100010-appb-000002
为槽下最小磁场感应强度值，F g为密封间隙磁压降，μ 0为起始磁导率，g为密封间隙，β为倾角，S为槽宽。
对于一个拥有N个极齿的磁性液体密封，其极限密封压差为
Figure PCTCN2020100010-appb-000003
可见，磁性液体的密封压力与永磁体的性能、极靴的齿数N、饱和磁化强度M S及极齿顶端与动环密封坝面间各级极齿下的最大磁场强度和最小磁场强度之间的差值ΔB i密切相关。饱和磁化强度M S、极齿顶端与动环密封坝面间的密封间隙中各级极齿下的最大磁场强度和最小磁场强度之间的差值ΔB i越大以及极靴的齿数N越多，磁性液体密封的耐压能力越强。
在密封端面内、外径两侧无压差时，处于极齿顶端与动环密封坝面间的磁性液体，对称聚集在极齿顶端的中径圆周上形成矩形截面液环；当密封端面内、外径两侧有压差时，磁性液体呈凹面在高压侧、凸面在低压侧的弓形截面液环，产生的恢复原状的弹力平衡压差的作用力；当密封端面内、外径两侧压差增大到超过磁性液体密封的承载能力时，聚集在极齿顶端的磁性液环开始变形，然后迅速穿孔，此时被密封的介质通过针孔流到下一级；随着下一级密闭环形腔室内的压力增大，极齿顶端磁性液环内、外径两侧压差减小，磁性液体在磁力机构的圆环形永磁体产生的磁场作用下，重新聚集，针孔愈合，恢复成工作状态。
用于熔盐堆核主泵的基于磁性液体密封与流体动压机械密封的组合型非接触式双端面 密封工作原理：动环16与静环12、19相对静止时，在弹簧力作用下，动环16和静环12、19两密封端面紧密贴合，极靴14、18的极齿与静环12、19密封端面的初始间隙d＝0.05～0.2mm，即静止状态磁性液体密封间隙d；此时，静环密封端面与动环的密封坝面形成的接触密封与磁性液体密封共同作用阻止密封端面的一侧流体在压差作用下向另一侧流动而达到密封的目的；
动环16与静环12、19相对转动时，动环16端面的螺旋槽28泵入阻塞流体，产生端面开启力，密封端面脱开，此时流体动压形成的端面开启距离δ＝3～5μm，加上极靴14、18距静环12、19端面的初始距离d＝0.05～0.2mm，构成运转状态磁性液体密封间隙d+δ；随着“泵入式”流体动压机械密封的运行，阻塞流体不断被泵送循环，带走端面摩擦热，有效冷却密封端面和降低磁性液体温度；在“泵入式”流体动压机械密封的剪切流和磁性液体密封的“O”形液环共同作用下，保证了密封端面内、外径两侧流体互不泄漏。
由于组合型非接触式双端面密封的磁性液体密封处于动环的、具有一定径向宽度的密封坝面部位，当动环受转轴跳动影响产生径向位移时，附着在静环极齿顶端的、轴向紧贴在动环密封坝面的磁性液环相对于动环出现微量径向位移，但动环密封坝面宽度使得磁性液环仍能保持一个个完整的“O”形液环可靠地处于静环极齿顶端与动环密封坝面之间，提供密封能力。
本专利具有的优点和积极效果是：
(1)实现了泵内介质的零泄漏。利用阻塞流体的大于泵腔内介质的压力和磁性液体的无间隙密封，有效阻止了泵腔内流体的外泄。
(2)克服了磁性液体密封的径向间隙敏感性。静环端面上设置永磁铁和极靴，动环的密封坝与其配合，当动环运转过程中出现径向跳动时，虽然与极靴的对应位置有所偏移，但极靴与动环的密封坝的轴向间距不变，保证了磁性液体密封的密封能力。
(3)具有自冷却密封界面的效果。自泵送形成的流体循环在密封界面间不断流动，带走磁性液体密封和流体动压密封工作时各自流体黏性剪切摩擦产生的热量，降低了密封界面温度，减少了密封端面形变，以及温度对磁性液体密封性能的影响。
(4)极高的密封可靠性。组合密封中的磁性液体密封在瞬时过压击穿或发生偏移变形时，其磁性液体很快在磁场作用下自我“愈合”复位至极齿和密封坝之间，重新形成密封能力。
(5)密封界面无摩擦，使用寿命长。组合密封工作时，自泵送流体动压机械密封产生动压，分离动环与静环，形成非接触式密封，使得动、静环无摩擦磨损；磁性液体密封， 通过极靴与密封坝之间的磁性液体实现密封，其极靴与密封坝不接触，无摩擦磨损。
附图说明
下面结合附图和具体实施例对本专利进一步说明
图1是钠冷快堆原型堆(PFBR)的一回路钠泵简图；
图2是密封结构剖面图；
图3是动环端面结构图；
图4是静环端面结构图；
图5是动静环结构示意图
图6是磁力发生机构立体图；
图7是磁力机构在动环密封端面的投影示意图；
图8是密封端面间磁力机构磁力循环线示意图；
图9是密封端面闭合状态磁性液体密封间隙示意图；
图10是静环用磁性液体密封环立体图；
图11是静环用磁性液体密封环磁力机构磁力循环线示意图；
图12是一个极齿磁场分割模型；
图13是密封端面开启状态磁性液体密封间隙示意图。
图中：1—机械密封；2—止推轴承；3—泵轴；4—导向轴承；5—叶轮；6—轴套；7—销钉；8—轴套用O形圈；9—端盖；10—弹簧；11—静环用磁性液体密封环；12—静环；13—永磁体；14—极靴；15—动环用O形圈；16—动环；17—永磁体；18—极靴；19—静环；20—静环用磁性液体密封环；21—弹簧；22—端盖；23—密封腔壳体；24—销钉；25—磁性液体；26—永磁体环；27—极靴环；28—螺旋槽；29—密封堰；30—密封坝；31—螺旋槽凸面；32—螺旋槽凹面；33—引流孔道；34—集流环槽。
具体实施方式
为了更清楚地描述本专利的上述特征和优点，下面结合附图对本专利的具体实施方式进行进一步说明。
图2～图7描述了一种用于熔盐堆核主泵、基于磁性液体密封与流体动压型机械密封的组合型非接触式双端面密封，将其用于密封熔盐堆核主泵转轴与壳体之间的间隙，可以保证熔盐泵轴封的零泄漏和长周期安全稳定运行。
动环16上下两端面结构以动环中截面M‐M对称布置，每个端面包括螺旋槽28、密封堰29和密封坝30三部分，螺旋槽28均布于动环端面的外径侧，动环端面的内径侧为密封坝30，螺旋槽28之间的密封面为密封堰29。
静环12、19端面设置集流环槽34和磁力发生机构(由永磁体13、极靴14或永磁体17、极靴18组成)，集流环槽34位于端面外径侧，引流孔道33均布在集流环槽34内，磁力发生机构位于端面内径侧；其中，集流环槽34的外径大于动环端面螺旋槽28的槽根圆直径，内径小于或等于螺旋槽28的槽根圆直径，集流环槽34的环宽与引流孔道33直径相等；磁力发生机构的外径小于集流环槽34的内径，磁力发生机构的内径大于静环12、19密封端面的内径。
动环16与轴套6之间通过螺纹24联接，螺纹旋向与转轴旋转方向相反，动环16与轴套6的径向采用轴套6外圆柱面定位，轴向采用轴套6上的轴肩端面定位。
静环12、19与壳体23之间用磁性液体密封。永磁体环26嵌入极靴环27内组合成磁力发生机构，磁力发生机构嵌入壳体23内与壳体23组成一体，极靴环27内圆柱面开设有两组沿轴向等间距分布的极齿和齿槽，极靴环的所有极齿朝向静环12、19外圆柱面，并且装配后极靴环27的极齿端面与静环外圆柱面之间径向间隙0.05～0.2mm。
极靴环27的极齿处注有磁性液体，磁性液体在磁力作用下吸附在极靴环27的极齿端面及其周围，在极齿与静环外圆柱面之间形成沿轴向分布的等直径的磁性液体密封圈。
静环12、19与壳体23的径向采用静环外圆柱面定位，周向采用防转销定位，静环用磁性液体密封环11、20嵌入并固定在壳体23内，静环12、19外圆柱面与静环用磁性液体密封环11、20的极靴环27内圆柱面之间的径向密封间隙恒定。
工作时动环16以图3所示的逆时针方向运转，这种组合型非接触式双端面密封，其动环密封端面外径侧开设有螺旋槽，随着动环旋转，螺旋槽28中的阻塞流体即氩气被螺旋槽的凹面32加速成高速流体，沿螺旋槽流向螺旋槽根部，随着螺旋槽流通截面的逐渐减小，流经单位流通截面上的流体分子数增多，进一步提升流体压力，另一方面，螺旋槽中的流体流经流通截面最窄的螺旋槽根部之后进入静环密封端面流体流通截面宽大的集流环槽，流体速度骤降，部分流体动能转化为流体动压能，再次提升流体压力，从而在动静环密封端面间形成开启力，分离动静环，避免动静环直接接触发生摩擦磨损；同时，动环旋转形成密封端面间流体周向剪切力，阻止密封端面的一侧流体在压差作用下向另一侧流动而达到密封的目的。从阻塞流体腔中楔入螺旋槽中的流体，流经流通截面最窄的螺旋槽根部之 后进入静环密封端面的集流环槽，在压差的作用下经由引流孔道重新流回阻塞流体腔，形成一次次自泵送循环。
组合型非接触式双端面密封的内径侧部分的磁力发生机构在两密封环间产生均匀、稳定的磁场，磁性液体25吸附在极靴环表面，形成一圈圈沿密封环端面径向排列的磁性液体“O形圈”。
在自泵送循环过程中，阻塞介质被不断泵送循环，循环的流体能够有效冷却密封端面和磁性液体，为磁性液体密封创造了适宜的工作环境，有利于保证磁性液体的性能，实现“零泄漏”密封。
已知某型熔盐堆核主泵的高效运行转速600r/min，假设阻塞流体压力0.2MPa，泵腔密封介质压力0.05MPa，动环密封端面开设对数螺旋槽，槽数40，螺旋角22°，槽面宽比0.5，槽台宽比0.5，螺旋槽深40μm，膜厚1.2μm；静环密封端面开设环槽和轴向径向组合孔，环槽宽3mm，环槽深800μm；自泵送机械密封“泵入式”运行，计算得螺旋槽槽根处压力为0.208MPa。
下面选取某一型磁力机构，计算其承压能力。选取永磁体为钕铁硼G45EH，剩磁B f/T为1.28～1.36，内禀矫顽力2387H cj/kA·m -1，矫顽力971H cB/kA·m -1，最大磁能积318～358(BH) max/kA·m -3；磁性液体型号MF01(北京交通大学制备，李德才.磁性液体密封理论及应用[M].北京：科学出版社，2010.)，基液为机油，饱和磁化强度Ms为450Gs，密度1.23(kg/m 3)×10 3，黏度20 25℃)/cP，起始磁导率μ 0为0.8m/H；假设极靴端面的极齿齿宽a为1mm，极齿与动环密封坝面间隙g为0.2mm，边缘磁通范围取m＝2g。
将极靴简化，用图12表示一个极齿磁场分割模型来计算磁压降，根据图形将磁场划分为5种磁通管，共有一个矩形磁通管Ⅰ，四个1/4圆柱体Ⅱ，四个1/4空心圆柱体Ⅲ，四个1/8球体Ⅳ，四个1/8空心球体Ⅴ，分别计算各个磁通管的磁压降F g。
矩形磁通管Ⅰ：
Figure PCTCN2020100010-appb-000004
1/4圆柱体Ⅱ：
Figure PCTCN2020100010-appb-000005
1/4空心圆柱体Ⅲ：
Figure PCTCN2020100010-appb-000006
1/8球体Ⅳ：
Figure PCTCN2020100010-appb-000007
1/8空心球体Ⅴ：
Figure PCTCN2020100010-appb-000008
总的磁压降：
F g＝F g1+4×(F g2+F g3+F g4+F g5)
齿下磁场最强
Figure PCTCN2020100010-appb-000009
槽下磁场最弱
Figure PCTCN2020100010-appb-000010
则任一级的极限密封压差为ΔP max＝M s(B max-B min)
根据本方案实现动、静环密封端面径向密封的极靴结构，极靴左右各有4个极齿，共八级极齿，齿宽1mm，极齿与动环密封坝面间隙0.2mm，则：
F g＝0.0121
Figure PCTCN2020100010-appb-000011
Figure PCTCN2020100010-appb-000012
ΔP＝NM s(B max-B min)＝0.25MPa
如图6所示，根据极靴在动环密封端面的投影范围，可知极靴内径处受到的压力为泵腔密封介质压力即P1＝0.05MPa，极靴外径处受到的压力约等于螺旋槽槽根处的压力即P2＝0.208MPa，极靴内外径压力差P＝|P1‐P2|＝0.158MPa，由于磁力机构密封能力ΔP＝0.25MPa＞0.158MPa，则密封环端面的磁力机构能够实现密封压力要求；同理，两个静环用磁性液体密封环在相同极靴结构参数情况下，密封压力也能达到0.25MPa，大于阻塞流体压力0.2MPa，能够满足静密封要求。
控制方程式为非线性偏微分方程，无法求得解析解，可以使用FLUENT软件数值求解，进而获得端面流场的压力分布。在相同运行工况下，计算n个不同的密封腔阻塞流体压力对应的螺旋槽内径侧压力值，通过离散点二次多项式拟合，得到阻塞流体压力y与螺旋槽内径侧压力x的关系：y＝a+b 1x+b 2x 2，其中a＝-7952.50798±2.32815，b 1＝0.99996±2.42135×10 -5，b 2＝-1.06858×10 -10±5.76379×10 -11。
分析发现，当泵腔工作压力为0.05MPa时，考虑到阻塞流体压力至少大于密封介质压力，所以只要阻塞流体压力不超出0.05MPa～0.292MPa区间均能保证组合密封安全有效。

Claims (9)

  1. 一种用于熔盐堆核主泵的组合型非接触式双端面密封，设置于旋转设备的壳体与转轴之间，包括动环(16)、静环(12、19)、动环用O形圈(15)、静环用磁性液体密封圈(11、20)、永磁体(13、17)、极靴(14、18)、弹簧(10、21)和端盖(9、22)、壳体(23)、轴套(6)、紧定螺钉(7)，其特征是：组合型非接触式双端面密封由“泵入式”流体动压机械密封和磁性液体密封组成，磁性液体密封设置于自泵送流体动压机械密封的密封坝的中部；
    动环(16)的上下两端面为动环密封端面，每一动环密封端面都设有槽台区和密封坝，槽台区分布在端面的外径侧，密封坝(30)分布在端面的内径侧部分，槽台区开设有均布的3组或3组以上的螺旋槽(28)，螺旋槽之间的密封面构成密封堰(29)，螺旋槽(28)的两侧槽壁，一侧为凸面(31)，另一侧为凹面(32)，动环(16)上下两端面结构以动环中截面M‐M对称布置；
    静环(12、19)密封端面具有集流环槽(34)和磁力发生机构，集流环槽(34)位于密封端面外径侧，引流孔道(33)将集流环槽(34)与阻塞流体腔连通，磁力发生机构位于密封端面内径侧部位；
    圆环形永磁体(13、17)嵌入极靴(14、18)内组合成磁力发生机构，磁力发生机构嵌入静环(12、19)密封端面开设的磁力机构安装环槽内与静环组成一体，极靴(14、18)端面开设有沿径向等间距分布的环形极齿和齿槽，极靴的所有极齿朝向静环(12、19)密封端面，并且装配后极靴(14、18)的极齿端面低于静环(12、19)密封端面0.05～0.2mm；
    极靴(14、18)的极齿处注有磁性液体，磁性液体在磁力作用下吸附在极靴的极齿端面及其周围，在极齿与动环密封坝的中部之间形成沿径向分布的不同直径的磁性液体密封圈；
    动环(16)与静环(12、19)相对静止时，在弹簧力作用下，动环(16)和静环(12、19)两密封端面紧密贴合，极靴(14、18)的极齿与静环(12、19)密封端面的初始间隙d＝0.05～0.2mm，即静止状态磁性液体密封间隙d；此时，静环密封端面与动环的密封坝面形成的接触密封与磁性液体密封共同作用阻止流体泄漏；
    动环(16)与静环(12、19)相对转动时，动环(16)端面的螺旋槽(28)泵入阻塞流体，产生端面开启力，密封端面脱开，此时流体动压形成的端面开启距离δ＝3～5μm加上极靴(14、18)距静环(12、19)端面的距离d＝0.05～0.2mm，构成运转状态磁性液体密封间隙d+δ；随着“泵入式”流体动压机械密封的运行，阻塞流体不断被泵送循环，带走端面摩擦热，有效冷却密封端面和降低磁性液体温度；在“泵入式”流体动压机械密封和磁性 液体密封的共同作用下，保证密封端面零泄漏。
  2. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征是：轴套(6)、轴套用O形圈(8)、动环(16)、静环(19)、静环用磁性液体密封圈(20)和旋转设备的壳体(23)及转轴(3)围成工质腔，工质腔内下部是高温熔盐，上部为保护氩气，阻塞流体亦为氩气，阻塞流体压力的设定范围：最小压力为旋转设备内被密封介质的压力，最大压力为磁性液体密封压力与旋转设备内被密封介质的压力之和。
  3. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征是：极靴(14、18)朝向密封端面的一侧沿径向开设有两组间隔排列的极齿和齿槽，每组有径向排列的极齿3～5个，齿宽0.5～2mm，槽宽0.5～2mm；永磁体(13、17)沿径向充磁。
  4. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征是：集流环槽(34)的外径大于对应的动环(16)端面螺旋槽(28)的槽根圆直径，内径小于或等于螺旋槽(28)的槽根圆直径，集流环槽(34)的环宽与引流孔道(33)的直径相等。
  5. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征是：磁力发生机构的外径小于集流环槽(34)的内径，磁力发生机构的内径大于静环(12、19)密封端面的内径。
  6. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征是：动环(16)及其两侧的静环(12、19)、端盖(9、22)均穿套在轴套(6)上；轴套(6)与转轴通过紧定螺钉(7)固定，轴套(6)与转轴之间用O形圈(8)密封；动环(16)与轴套(6)之间用O形圈(15)密封；静环密封端面的背面分别支撑有3个以上的弹簧(10、21)，弹簧的另一端作用在端盖(9、22)上，端盖(9、22)固定连接于旋转设备的壳体(23)，使动环密封端面与静环密封端面之间获得所需的端面比压。
  7. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征是：动环(16)与轴套(6)之间通过螺纹(24)联接，螺纹旋向与转轴旋转方向相反，动环(16)与轴套(6)的径向采用轴套(6)外圆柱面定位，轴向采用轴套(6)上的轴肩端面定位。
  8. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征是：静环(12、19)与壳体(23)之间静环用磁性液体密封圈(11、20)由极靴环(27)和永磁体环(26)组成，极靴环(27)内圆柱面与静环外圆柱面之间径向间隙0.05～0.2mm。
  9. 如权利要求1所述的一种用于熔盐堆核主泵的组合型非接触式双端面密封，其特征 是：静环(12、19)与壳体(23)的径向采用静环外圆柱面定位，周向采用防转销定位，静环用磁性液体密封环(11、20)嵌入并固定在壳体(23)内，静环(12、19)外圆柱面与静环用磁性液体密封环(11、20)的极靴环(27)内圆柱面之间的径向密封间隙恒定。
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