CN107355540B - Gap adaptive adjustment sealing structure - Google Patents

Abstract

The invention discloses a clearance self-adaptive adjusting sealing structure, which comprises a plurality of sections of sealing blocks connected into a ring by a circumferential spring, wherein the sealing blocks are embedded in a sealing block mounting groove of a stator, a plurality of rings of sealing teeth are axially arranged on an inner ring of the sealing blocks, a conical slope is arranged on the outer circumference of a rotor matched with the sealing teeth, a conical surface is formed on the outer circumference of the conical slope around the rotor, and the sealing teeth are arranged along a direction parallel to the conical slope; the sealing block is positioned in the sealing block mounting groove through an axial spring which is axially arranged, and an axial yielding space is arranged between the sealing block and the sealing block mounting groove. The sealing structure can adaptively adjust the sealing gap along with the increase of the pressure difference between the upstream and downstream of the seal, and in the adjusting process, the sealing block can act along the axial direction (the fluid flowing direction) and is matched with the slope structure of the surface of the rotor, so that the sealing gap is reduced, and finally the leakage is greatly reduced.

Description

Gap adaptive adjustment sealing structure

technical field

The invention belongs to a sealing structure, in particular to a sealing structure used in a rotating machine, in particular to an adaptively adjustable sealing structure capable of gradually reducing the gap as the pressure difference between upstream and downstream of the seal increases, and the sealing structure can Significantly reduce the leakage of seals in rotating machinery (such as steam turbines, compressors, etc.), and improve energy efficiency.

Background technique

Seals used in rotating machinery reduce fluid leakage by increasing resistance to fluid flow. The idea is to arrange a series of non-contact throttling gaps and vortex chambers on the channel through which the fluid flows. When the fluid flows through the narrow channel formed by the sealing teeth and the corresponding rotor surface, it is continuously throttled and gradually reduced. The pressure and expansion accelerate, and the fluid rotates and frictions in the vortex chamber, dissipating the high-speed fluid kinetic energy through the turbulent vortex into heat energy, which is absorbed by the fluid, and the specific volume of the fluid increases, making the initial velocity of the next gap entrance get smaller. For multi-tooth seals, the pressure difference between the front and rear of each sealing tooth decreases step by step, the lower the flow rate through each sealing tooth, the specific volume of the gas gradually increases, so that the air leakage of the seal is greatly reduced, reaching The role of sealing.

For a long time, the efficiency of internal seals in rotating machinery has been the focus of researchers. The research on sealing efficiency at home and abroad mainly focuses on the following aspects: increased drag of turbulent flow, improved design of blade tip or cylinder structure, and reduced sealing gap. Among them, reducing the sealing gap is the most direct and effective measure to reduce the leakage of the seal and improve the sealing efficiency. The brush seal and the fingertip and blade seals that appeared later are typical representatives. This type of seal is that the seal tooth adopts a flexible structure, which can be given a limited concession when in contact with the rotor. Although this type of seal has a good sealing effect, due to the small gap, or even a negative gap, the friction between the seal and the rotating parts is limited. Inevitably, it will still cause large vibrations in severe cases, and when used for a long time, due to wear and tear on the contact parts, the gap will often be larger than that at the beginning of the installation, and the sealing effect will be greatly reduced.

Another idea to solve the contradiction between leakage and wear resistance is to design the sealing gap as adjustable. The specific method is to change the dynamic and static gap of the seal by directly measuring the sealing gap, or monitoring acoustic emission signals, temperature signals, etc., and applying feedback force through piezoelectric crystals, compressed air, hydraulic oil, electromagnets, etc. This type of seal is represented by an adjustable seal designed by Braden Company in the United States. The Braden seal replaces the flat spring on the back of the traditional seal ring with a coil spring, and allows the fluid upstream of the seal to directly act on the back of the seal ring. Make the seal reach the closed position and maintain the set value of the radial clearance of the seal. The adjustable sealing structure of Braden seal is complex, and it is required that the seal can expand and contract freely in the radial direction. When the sealing body shrinks in the radial direction, it is necessary to reserve a certain shrinkage gap between two adjacent seals. The gap is too large. If the gap is too large, the leakage will increase. If the gap is too small, the sealing block will shrink and jam due to dirt. Therefore, the reliability in actual application is not high. After being introduced into our country, many units have experienced failures of sealing gap imbalance.

Contents of the invention

The technical problem to be solved by the present invention is to provide a self-adaptive adjustment sealing structure that can gradually reduce the gap with the increase of the pressure difference between the upstream and downstream of the seal, aiming at the defect that the existing Braden seal structure is prone to gap imbalance. When the seal is working, the action direction is different from the radial contraction movement of the traditional adjustable seal, but moves along the axial direction (fluid flow direction), and cooperates with the slope treatment of the rotor surface to reduce the seal gap and finally greatly reduce the sealing gap. The role of small leakage.

The present invention specifically adopts following technical solutions to realize:

The gap adaptively adjusts the sealing structure, including several sections of sealing blocks 2 connected by circumferential springs 5 to form a ring. The sealing blocks 2 are embedded in the sealing block installation groove 11 of the stator 1. The inner ring of the sealing block 2 Several rings of sealing teeth 21 are arranged in the axial direction, and the outer circumference of the rotor 4 and the sealing teeth 21 are provided with a conical slope 41. The conical slope 41 forms a conical surface around the outer circumference of the rotor, and the sealing teeth 21 are parallel to the cone. The direction of the slope is set; the seal block 2 is positioned in the seal block installation groove 11 by the axially arranged axial spring 3 , and an axial relief space 12 is provided between the seal block 2 and the seal block installation groove 11 .

Further, the low end of the conical slope 41 is close to the upstream of the sealing fluid, and the high end of the conical slope 41 is close to the downstream of the sealing fluid.

Further, the axial spring 3 is compressed and arranged between the side of the sealing block 2 close to the high end of the conical slope and the sealing block installation groove 11 .

Preferably, the axial spring 3 is a coil spring.

In the gap self-adaptive adjustment sealing structure of the present invention, the conical slope 41 is a conical surface processed on the surface of a cylindrical rotor, or a segment of a rotor adopting an integral conical structure.

Preferably, the inclination angle of the conical slope 41 is 5-10°.

Compared with the prior art, the gap self-adaptive adjustment sealing structure proposed by the present invention has the following beneficial effects:

(1) The sealing structure proposed by the present invention installs an axial spring on the side of the sealing block, and reserves a certain concession space in the sealing block installation groove and the axial direction of the sealing block, and cooperates with the conical slope surface of the rotor to make the sealing The block together with the sealing teeth achieve the purpose of adaptively reducing the sealing gap and reducing the sealing leakage under the action of the upstream and downstream fluid pressure difference between the rotor and the stator and the side axial spring force.

(2) The surface of the rotor with the sealing structure proposed in the present invention has undergone slope treatment. When the sealing teeth of the seal block rub against the rotor surface, the axial component of the friction force will cause the seal to automatically retreat away from the slope surface of the rotor. , to avoid seal tooth wear caused by increased friction;

(3) The type of sealing proposed by the present invention has a simple structure and is easy to manufacture. Most of the seals currently used in the field can be easily improved by modifying the sealing structure and slope treatment of the rotor surface.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a schematic diagram of the assembly of the gap self-adaptive adjustment sealing structure in the embodiment.

Fig. 2 is a schematic diagram of the movement of the gap self-adaptive adjustment sealing structure in the embodiment.

Fig. 3 is a force analysis diagram of the gap self-adaptive adjustment sealing structure in the embodiment.

Symbols in the figure: 1-stator, 11-seal block installation groove, 12-axial relief space, 2-seal block, 21-seal teeth, 3-axial spring, 4-rotor, 41-conical slope, 5-circle to the spring.

Detailed ways

Example

Referring to Fig. 1, the gap self-adaptive adjustment sealing structure shown in the illustration is the preferred solution of the present invention. The sealing structure is installed on the stator 1 where the shaft end or blade top of the rotating machine needs to be sealed, and cooperates with the rotor 4 to achieve sealing. effect.

Specifically, the sealing structure includes a sealing block 2 and an axial spring 3 arranged on the side of the sealing block. The sealing block 2 adopts a comb-tooth sealing structure, and several segments of circumferential springs 5 connect the sealing block 2 of the arc segment into a ring. And the sealing block 2 is embedded in the sealing block installation groove 11 provided on the inner wall of the stator 1, and the sealing teeth 21 which are in contact with the outer circumferential surface of the rotor are arranged on the sealing block 2, and all the sealing blocks 2 are installed along the circumferential direction of the stator 1 One circle, the adjacent sealing blocks are connected by a circumferential spring 5, and a certain radial tension is ensured. The circumferential spring 5 can ensure the elastic setting of the sealing block 2 in the radial direction, so that the sealing block can move in the radial direction. It has a certain elastic margin, and realizes the adjustment of the gap between the sealing teeth 21 on the sealing block and the rotor 4 when dynamic and static rubbing occurs.

In this embodiment, the outer circumference of the rotor 4 in contact with the sealing teeth 21 is provided with a conical slope 41, the conical slope 41 forms a continuous conical surface around the outer circumference of the rotor, and the sealing teeth 21 are arranged in several circles along the axial direction, correspondingly, Several rings of sealing teeth 21 are arranged in a direction parallel to the conical slope, that is, the tip line of the sealing teeth 21 is parallel to the conical slope, and when the seal block moves axially, it can be ensured that all the sealing teeth 21 are consistent with the conical slope.

In practical applications, the conical slope 41 may be a conical surface machined from the surface of a cylindrical rotor, or a segment of a rotor with an integral conical structure.

The sealing block 2 is positioned and fitted in the sealing block installation groove 11 by the axially arranged axial spring 3 , and an axial relief space 12 is provided between the sealing block 2 and the sealing block installation groove 11 . In this embodiment, the low end of the conical slope 41 is set close to the upstream of the sealing fluid, the high end of the conical slope 41 is set close to the downstream of the sealing fluid, and the axial spring 3 is compressed and arranged on the side of the sealing block 2 close to the high end of the conical slope. Between the sealing block installation grooves 11, the axial spring 3 is a coil spring, one end of which is fixedly embedded in the sealing block installation groove of the stator, and the other end is compressed and contacts the end surface of the sealing block 2, and the sealing block 2 is axially pressed and positioned on the In the sealing block installation groove, without the thrust of the sealing fluid, it is ensured that the sealing teeth 21 on the sealing block 2 are far away from the conical slope 41, and the distance between the sealing teeth 21 and the conical slope is the largest at this time.

The axial spring 3 in this embodiment is a compressed spring, which maintains a certain axial preload on the seal block 2 after installation. When working, the fluid pressure difference between the upstream and downstream of the seal block 2 will overcome the axial preload. The axial spring 3 is further compressed, and the elastic force of the axial spring 3 becomes larger, and finally balances with the axial fluid pressure on the sealing block 2. During this process, when the axial retreat of the sealing block 2 under the fluid pressure , the gap between the conical inclined surface 41 on the rotor 4 and the sealing teeth 21 will decrease accordingly, so as to reduce the leakage amount.

Generally speaking, when the sealing structure is working, the upstream pressure P _up of the sealing structure will be greater than the downstream pressure P _down , as shown in Figure 1, if the sealing block is not fixed in the flow direction, the effect of the upstream and downstream pressure difference If the axial displacement is combined with the technical solution of the present invention, the slope treatment on the rotor surface can reduce the sealing gap.

As shown in FIG. 2 , the dotted line indicates the position of the sealing block before moving, and the solid line indicates the position of the sealing block after moving. h ₁ is the gap between the sealing tooth 21 and the conical slope 41 on the rotor surface when the seal does not move; h ₂ is the gap between the sealing tooth 21 and the conical slope 41 on the rotor surface after the seal moves under the action of the upstream and downstream pressure difference; θ is the surface slope angle of the conical slope 41; L is the horizontal displacement of the sealing block 2 retreating under the action of the upstream and downstream pressure difference. It can be obtained that when the sealing block 2 moves axially under the action of pressure difference, the expression of the gap change Δh is as follows:

Δh=h ₁ -h ₂ =L·sinθ

From the above formula, the expression of the gap between the sealing tooth 21 and the conical slope 41 on the rotor surface after the sealing block retreats can be obtained:

h ₂ =h ₁ -L·sinθ

In actual work, when the sealing block moves axially under the action of pressure difference, the sealing gap _h2 depends on the displacement L of the sealing block and the surface slope angle θ of the conical slope on the rotor surface. The horizontal distance L and the slope angle θ of the conical slope of the rotor and the sealing mating surface achieve the ideal matching size.

The adjustable sealing type proposed by the present invention can also effectively avoid the impact of friction between the sealing teeth and the surface of the rotor caused by the reduction of the gap. The specific analysis is as follows:

轴向弹簧(压簧)的弹性力为/>

在达到稳定时，这一对力达到平衡状态，此时密封齿21与转子表面圆锥斜坡41间隙保持一定值。当密封齿21与转子表面圆锥斜坡41发生碰摩时，假设密封齿21所受的碰摩力为/>

该力方向垂直于转子表面圆锥斜坡41方向，由于转子表面圆锥斜坡的坡度角θ，碰摩力/>

可以分解为径向力/>

和轴向力/>

径向力/>

与密封背面径向约束力(周向弹簧提供)平衡，而轴向力/>

会使得密封块发生逆流体流动方向的运动趋势，这一运动会使得密封齿远离转子表面圆锥斜坡，从而避免碰摩的加剧，也就是说，当密封齿与转子表面发生碰摩时，本发明所提出的密封会自动退让消除碰摩。As shown in the force analysis diagram of the sealing body in Figure 3, it is assumed that the resultant force of the fluid under the pressure difference of the upstream fluid under the working condition of the sealing body is

The elastic force of the axial spring (compression spring) is />

When the stability is reached, the pair of forces reaches a balanced state, and at this time, the gap between the sealing teeth 21 and the conical slope 41 on the rotor surface maintains a certain value. When the sealing tooth 21 rubs against the conical slope 41 on the rotor surface, it is assumed that the frictional force on the sealing tooth 21 is />

The force direction is perpendicular to the direction of the conical slope 41 on the rotor surface. Due to the slope angle θ of the conical slope on the rotor surface, the rubbing force/>

can be decomposed into radial force/>

and axial force/>

radial force/>

Balanced with the radial restraint force on the back of the seal (provided by the circumferential spring), while the axial force />

It will cause the sealing block to move against the direction of fluid flow. This movement will make the sealing teeth away from the conical slope of the rotor surface, thereby avoiding the aggravation of rubbing. That is to say, when the sealing teeth rub against the rotor surface, The raised seal will automatically back off eliminating rubbing.

The above embodiment has described the basic principle of the present invention and main feature and the advantage of the present invention, those skilled in the art should understand that the present invention is not limited by the above embodiment, and what described in the above embodiment and description is only to illustrate the present invention The specific working principle, under the premise of not departing from the spirit and scope of the present invention, the present invention also has various changes and improvements, and these changes and improvements all fall within the scope of the claimed invention, and the claimed protection scope of the present invention is defined by the appended The claims and their equivalents are defined.

Claims (6)

1. The gap adaptively adjusts the sealing structure, including several sections of sealing blocks (2) connected into rings by circumferential springs (5), and the sealing blocks (2) are embedded in the sealing block installation groove (11) of the stator (1). ), the inner ring of the sealing block (2) is provided with several rings of sealing teeth (21) along the axial direction, which is characterized in that: A conical slope (41) is provided on the outer circumference of the rotor (4) and the sealing tooth (21), and the conical slope (41) forms a conical surface around the outer circumference of the rotor, and the sealing tooth (21) is parallel to the conical slope. direction setting; The sealing block (2) is positioned in the sealing block installation groove (11) by the axially arranged axial spring (3), and an axial spring is arranged between the sealing block (2) and the sealing block installation groove (11). Give way to space (12). 2. The gap self-adaptive adjustment sealing structure according to claim 1, characterized in that, the low end of the conical slope (41) is close to the upstream of the sealing fluid, and the high end of the conical slope (41) is close to the downstream of the sealing fluid . 3. The gap self-adaptive adjustment sealing structure according to claim 2, characterized in that the axial spring (3) is compressed and arranged on the side of the sealing block (2) close to the high end of the conical slope and the sealing block installation groove (11 )between. 4. The gap self-adaptive adjustment sealing structure according to claim 1, characterized in that the axial spring (3) is a coil spring. 5. The gap self-adaptive adjustment sealing structure according to any one of claims 1-3, characterized in that, the conical slope (41) is a conical surface processed on the surface of a cylindrical rotor, or a rotor with an integral conical structure section of 6. The sealing structure for self-adaptive gap adjustment according to claim 4, characterized in that, the inclination angle of the conical slope (41) is 5-10°.

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