RU2348849C2 - Sealing of turbomachine rotors - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention is related to the field of turbine construction. Groove seal comprises sealing slit concentric to rotor axis and filled by working fluid, and elements that limit this slit - rotor and responsive nonrotational part. Value of sealing slit in working modes is limited by values of 0.15-0.25 mm. Nonrotational part is made in the form of ring, cross section of which is "П"-shaped. Ring is installed strictly concentrically to rotor axis and is flexibly suspended to fixed part with the help of multi-layer packet assembled from thin steel file-hard corrugated tapes of the same thickness, which are connected serially as corrugation top to corrugation top. Tape junctions are evenly located along tops of corrugations, and gap in joints is arranged as minimum possible but at the same time it makes it possible to displace tape ends without overlapping at maximum amplitude of ring precessing. Radial preload along corrugation tops is arranged in process of assembly by displacement of semi-rings fixed to immovable body part to ring axis, and residual curve of corrugations in working modes as a result makes 0.05-0.1 mm. Side wall of ring has fixed protrusion that enters the upper semi-ring with clearance along protrusion perimeter and packet tapes. On internal side of ring side walls there are pockets evenly located along circumference, and guaranteed clearances are available between these walls and response ends of semi-rings. Low residual curve of corrugation (0.05-0.1 mm) in combination with low radial size of slit (0.15-0.25 mm) provide for minor leaks through seal in all working modes.

EFFECT: provision of high efficiency.

8 cl, 12 dwg

Description

The invention relates to the field of turbine construction.

Known seals of rotors of turbomachines are slotted (Martsinkovsky V.A. Non-contact seals of rotor machines. - M .: Mechanical Engineering, - 1980 - 200 p.), Labyrinth (Skubachevsky G. Aircraft gas turbine engines. M .: Mechanical Engineering, - 1969 - 544 p.).

The gap seal is an annular narrow radially narrow gap bounded by the surface of the rotor and the counter surface, for example, the housing or the inner surface of the inner ring of the guide apparatus, etc.

The densified areas of high pressure are separated from the low pressure area by this gap.

The disadvantage of this seal is its lack of effectiveness (high leakage through the seal) with a slot height of more than 0.3 mm.

Moreover, achieving its sufficient efficiency by increasing the length of the gap in the rational range is problematic. Since the mutual displacement of the elements forming the seal (for example, the rotor and the housing), existing seals should have less than the working clearance of the seal, with a mutual displacement of more than 0.3 mm, these seals will be ineffective.

The specified seal by technical nature is closest to the proposed invention and is taken as a prototype.

The task is to create a design of a gap seal for the rotors of turbomachines, effective both for small and large displacements of the rotors (for example, for displacements equal to 0.3-1.0 mm or more).

The problem is solved by applying the seal of the rotor of the turbomachine containing a sealing gap, concentric to the axis of the rotor filled with a working medium, the elements limiting this gap are the rotor and stator, characterized in that the size of the sealing gap in all operating modes of the machine is limited to 0.15 -0.25 mm, the non-rotating part of the seal is made in the form of a ring, the cross section of which is U-shaped, and the ring itself is strictly concentric with the axis of the rotor, resiliently suspended from the stator (for example, to the housing or inner ring of the guide apparatus) using a multilayer bag composed of red-hot steel corrugated tapes of the same thickness (for example, from 0.1 to 0.4 mm) or groups of corrugated tapes connected in a packet sequentially apex to apex of a corrugation, each group consisting of several corrugated tapes assembled by the corrugations into the corrugation without gaps (connected to each other in parallel), and the joints of the tapes are evenly located on the corrugation tops, and the gap at the joints of the tapes is selected as minimal as possible, but such that allows free without "overlap" the displacement of the ends of the tape at the maximum amplitude of the precession of the ring, the preliminary radial interference in the bag was carried out during assembly by displacement to the axis of the ring of the semirings mounted on the outside of the bag, which are mounted on a fixed body part (or the inner ring of the guide apparatus), the residual bend of the corrugation of each of the tapes in operating conditions, it is 0.05-0.1 mm, a protrusion is fixed on the side wall of the ring, which enters the upper half-ring with a gap around the perimeter of the protrusion, and a tape, the size of which is several of larger than the maximum possible amplitude of the precession of the ring, and on the inner side of the side walls of the ring formed pockets equally spaced circumferentially, and between these walls and the ends of half-rings are guaranteed clearance.

The increase in the hydrodynamic resistance of the channels between the corrugated tapes can also be achieved due to the corresponding design of the seal.

For example, the direction of the corrugations of the corrugated tapes in the seal can be performed at an acute angle to the axis of the rotor.

Also, the seal package can be made of two parts (packages), located one after the other along the axis of the rotor, while the vertices of the corrugations of one part are shifted half a step in the circumferential direction relative to the vertices of the corrugations of the other part.

In addition, the seal can be made so that the corrugations on both sides of the packet, making up a pair, form a "chevron", the axis of symmetry of which is perpendicular to the axis of the rotor.

In order to balance the weight of the ring, the joints of all tapes are placed in the upper vertical section and two adjacent to it on the right and left, alternating the joints of the tapes so that the adjacent tapes do not have joints in one section, and the joint of the tape resting on the ring is located in the vertical the plane.

In order to ensure safe possible contact of the side wall of the ring and the ends of the half rings from the higher pressure side and to reduce the wear of the seal, three or more ball stops are pressed into the protrusions of this side wall, consisting of a housing and a hot-rolled ball placed therein with free rotation, between the ball and the end face of the half-ring has a guaranteed clearance.

Ball stops can also be pressed into the second wall of the ring in response to ball stops in the first wall with a guaranteed clearance at the end of the half-ring.

In order to ensure the constancy of the radial size of the sealing gap in all operating modes of the machine, the U-shaped ring is made of material with approximately the same coefficient of linear thermal expansion as the material of the rotor.

In order to avoid wear of the rotor when touching the ring and the rotor, the ring can be made of a softer material than the rotor (for example, carbon fiber or polymer), and smooth red-hot tapes can be inserted between the ring and the package, as well as the half rings and the package, from the same material as the tape of the bag, and on the inner surface of the ring is fixed (soldered, glued, sprayed) produced soft layer.

The figures are shown without scale, with individual elements of the seal on them for a better understanding of the drawing may not be proportionally increased in comparison with other elements. In the transverse and longitudinal sections, the package of tapes is shown conditionally without hatching.

Figure 1 shows the main view of the proposed gap seals with local incisions.

Figure 2 shows a section along aa in figure 1 of this seal.

Figure 3 shows a section along BB in figure 1.

Figure 4 shows a view In figure 3.

Figure 5 shows a fragment of a longitudinal section of a seal with a package in which the corrugated tapes are doubled.

Figure 6 shows the expanded corrugated tapes in the embodiment in which the sealing package is made of two parts located one after the other along the axis of the rotor, and the vertices of the corrugations in one part are shifted half a step in the circumferential direction relative to the vertices of the corrugations of the other part (the latter by front view darkened).

Figure 7 shows the expanded corrugated tape in the embodiment in which the corrugation is performed at an acute angle to the axis of the rotor.

On Fig depicted in the expanded form of the corrugated tape in the embodiment, in which the sealing package is made of two parts, and the corrugations of both parts, comprising a pair, form a "chevron", the axis of symmetry of which is perpendicular to the axis of the rotor.

Fig.9 shows a variant of Fig.8 with a half-step shift in the circumferential direction of the parts of the package relative to each other.

Figure 10 shows a fragment of a longitudinal section of the seal in an embodiment in which a force is created that balances the weight of the inner ring.

Figure 11 shows a variant of the seal with end stops on the protrusions of the side wall from the side of greater pressure.

On Fig shows a fragment of a longitudinal section of the seal with the package, in which smooth tapes are installed outside the package.

The proposed seal of the rotor of the turbomachine (see FIGS. 1, 2) contains a sealing gap 1, a concentric axis of the rotor filled with a working medium, elements restricting this gap — a rotor 2 and a reciprocal non-rotating part 3, and the radial size of the gap in the operating modes is limited by the values 0.15-0.25 mm. Detail 3 is made in the form of a ring, the cross-section of which is U-shaped (see figure 2), and the ring itself is strictly concentric with the axis of the rotor, resiliently suspended from a fixed part 4 (for example, to the casing or inner ring of the guide apparatus) using a multilayer bag 5, assembled from steel red-hot corrugated tapes 6 of the same thickness (for example, from 0.1 to 0.4 mm) connected in series with the top of the corrugation to the top of the corrugation (see figure 1), and the joints of the tapes are evenly spaced corrugated peaks, and a gap of 7 at the joints selected m possible, but such that it allows free displacement of the ends of the tape 6 without overlapping at the maximum amplitude of the precession of the ring 3. The preliminary radial interference in the bag 5 was carried out during assembly by shifting to the axis of the ring 3 of the half rings 8, which are mounted on a fixed case 4 (or the inner ring of the guide apparatus), the residual deflection of the corrugation of each tape 6 as a result is 0.05-0.1 mm. On the side wall of the ring 3, a protrusion 9 is fixedly fixed (see Figs. 3, 4), which enters with a gap 10 around the perimeter of the protrusion 9 into the upper half ring 8, and the tape 6, the value of which is slightly larger than the maximum possible amplitude of the precession of the ring 3.

The fastening of the protrusion 9 can be performed in various ways. As a possible example, the protrusion 9 (see figure 4) has a cylindrical shank 11, which is pressed into the side wall of the ring 3, and the tab 12, bent into the mating groove of the ring 3.

On the inner side of the side walls of the ring 3 there are pockets 13 (see Figs. 2, 4), evenly spaced around the circumference, and between these walls and the ends of the half rings 8 there are guaranteed clearances 14 (see Figs. 3, 4).

The design parameters of the tapes 6 and their number is selected from the following considerations.

The thickness, width, step of the corrugations and the initial interference over the tops of the corrugations are selected from the condition of ensuring the required stiffness of the seal, the strength of the tapes and the absence of shear of the seal parts along its axis due to the differential pressure of the working medium on the seal (see below).

The initial bend of the corrugation of ribbons 6 is selected taking into account the required initial interference over the vertices of the corrugations, thermal expansion of the ring 3 and the displacement of this ring during precessing of the rotor 2, as well as from the condition of ensuring the residual bending of the corrugation in the assembled package 5 (installed in the seal) at operating conditions 0 , 05-0.1 mm and in other modes approximately 0.15-0.2 mm. The number of tapes 6 is selected from the condition of ensuring the maximum possible amplitude of the displacement of the rotor in the seal up to 0.5-1.5 mm while ensuring the above values of the residual deflection of the corrugation.

In addition, the package 5 (see figure 5) can be recruited from a series of connected top to top of the corrugations of packages 15, composed of parallel connected corrugations into corrugation without gaps of the tapes 6.

The package 5 can be composed of two identical parts (packages) 16 (see Fig.6), shifted relative to each other to reduce leaks through the seal on the half-step of the corrugation. Moreover, both packages 16 are independently fixed from rotation by the method described above with the help of protrusions 9 (not shown), and the radial sections in which the protrusions 9 are located are shifted relative to each other in the circumferential direction.

The direction of the corrugations 17 tapes 6 to increase their length and, therefore, reduce leakage through the seal (see Fig.7) can be performed at an acute angle to the axis of the rotor.

To further reduce leakage through the seal, the package 5 can also be made of two packages 16 (see Fig. 8), the corrugations 17 of the tapes 6 of which, comprising a pair, form a "chevron" 18.

Moreover, in this case both packages 16 can be shifted half a step in the circumferential direction relative to each other (see Fig. 9).

To balance the weight of the ring 3, the joints of all the tapes 6 are located in the upper vertical section (see Fig. 10) and two adjacent to it, shifted half a step to the right and left, alternating the joints of the tapes so that the adjacent tapes 6 do not have joints in one section. Moreover, the joint of the tape 6, based on the ring 3, is located in a vertical plane.

To ensure safe possible contact of the side wall of the ring 3 and the ends of the half rings 8 from the higher pressure side and to reduce the wear of the seal, three or more ball stops 19 are pressed into the protrusions of this side wall (see Fig. 11), consisting of a housing 20 and placed in it with the possibility of free rotation of the hot ball 21, and between the ball 21 and the end face of the half ring 8 there is a guaranteed clearance 22.

Ball stops 19 can be pressed into the second wall of the ring 3 in response to ball stops in the first wall with a guaranteed clearance at the end of the half ring 8 (not shown).

Ring 3 can be made of a material with approximately the same coefficient of linear thermal expansion as that of the rotor, while the approximate constancy of the radial size of the gap in all modes of operation of the machine will be ensured.

In the case of manufacturing the ring 3 from a material softer than the material of the tapes 6, on the outside of the bag 5 (see FIG. 12) between the ring 3 and the bag 5, as well as the half rings 8 and the bag 5, smooth steel red tape 23 can be inserted the same material as the tape 6.

On the inner surface of the ring 3 can be fixed (soldered, glued, sprayed) generated soft layer (not shown).

When the rotor 2 is precessed, an additional hydrodynamic (or gasdynamic) pressure develops in the sealing gap 1, which is greater, the greater the amplitude of the precession. This additional pressure creates a force that squeezes the ring 3 in the direction of displacement of the rotor 2 in the slot 1 (at zero viscosity of the working medium) or in a slightly different direction from this direction with a viscous working medium. The parameters of the tapes 6 are selected experimentally so that, firstly, the rotor 2 of the ring 3 does not touch and, secondly, that the natural frequency of the ring 3-packet 5 system is higher than the operating frequency range of the rotor 2.

When the rotor passes through the resonance, its precession amplitude will be maximum and with a further increase in revolutions it will decrease significantly. As a result, the packet 5 will be cyclically precessively loaded with decreasing bias amplitudes of the ring 3, which will facilitate its alignment. It will also happen when the rotor runs to zero revolutions.

The serial connection of the tapes 6 in the package 5 can provide the maximum displacement of the rotor 2 in the slit 1 to 1 mm or more, since the maximum displacement of the ring 3 is equal to the sum of the residual deflections of the corrugations of the tapes 6. Moreover, the proposed seal will be effective at small and large displacements of the rotor, how, firstly, the hydraulic resistance of the channels formed by the residual deflection of the corrugations is large due to its smallness, and, secondly, due to the fact that during the precession of the rotor, ring 3 will track the movement of rotor 2 and will not occur Tel'nykh sealing gap extension 1 during oscillation.

When assembling the ring 3 is installed strictly concentric with the axis of the rotor 2 by cyclic loading of the seal in the direction perpendicular to the axis of the rotor 2 with displacement amplitudes gradually decreasing to zero.

The presence of pockets 13 and gaps 14 at the ends of the semirings 8 leads to the fact that in the axial direction on the ring 3 from the side of the higher pressure acts the resultant, defined as:

where P2 is the greater pressure, P1 is the lower pressure, S is the cross-sectional area of the ring 3, perpendicular to the axis of the rotor.

This force does not exceed the resultant of the friction forces acting on the vertices of the corrugations resting on the ring 3, as a result of which the ring 3 does not shift along the axis of the rotor 2.

When calculating the seal on the axial shift of the ring 3, it should be taken into account that this shift can also occur due to the shift of the tapes 6 of the packet 5 to the side of lower pressure, on which not only force (1) will act, but also force

where S1 is the cross-sectional area perpendicular to the axis of the rotor of the fully extruded package. The axial shift of the ring 3 will not occur if F + F1 is less than the resultant friction forces along the vertices of the corrugations of the belts 6.

In the case of axial shift of the ring 3 with direct contact of the ring 3 with the rotor 2, it can only move until it stops against the side wall of the ring 3.

The most likely shift of the ring 3 towards lower pressure. Therefore, as already indicated, ball stops 19 are pressed into the protrusions of the side wall from the higher pressure side. Their presence allows in some cases to reduce the stiffness of the corrugated tapes 6, which can achieve greater sealing efficiency and its greater service life. The seal does not lose performance when the packet 5 or individual tapes 6 are axially shifted within the guaranteed gaps between the protrusions of the ring 3 and the ends of the half rings 8.

All tapes in package 5 are made of hardened stainless steel and may be silver plated to prevent wear.

When the joints of the tapes 6 are located, as shown in FIG. 5, an elastic force is created that is opposite to the weight of the ring 3 and partially or completely balances it. This is due to the fact that the lower corrugation is significantly stiffer than the upper one due to different boundary conditions - for the two upper corrugations, the end at the junction of the tape can be considered as hinged, and for the opposite lower corrugation, both ends can be considered elastically sealed.

In addition, the main factor that increases the rigidity of the corrugations of the lower half of the package 5 compared with the corrugations of the upper half of the package is the greater accumulation of the action of friction forces on the corrugation tops at the lower half, which prevents the corrugations from deforming during assembly of the seal and its operation. Due to these reasons, with the same deformation of the corrugations during assembly of the seal, an additional force is created, acting vertically upwards (against the force of the weight of the ring).

Among the advantages of the proposed seal should also include its lower wear, provided by the elastic suspension of the ring 3.

Another advantage of the proposed seal is the ability to replace it in case of failure without replacing other parts and components of the machine.

The proposed seal with small structural modifications can be made in the form of a labyrinth or brush seal. For example, the teeth forming expansion chambers at the labyrinth seal can be made on the inner surface of the ring 3 or on the outer surface of the rotor forming a sealing gap with the counter surface of the ring 3. In this case, the radial size of the sealing gap can also be 0.1- 0.5 mm, and the radial displacement of the rotor in the seal is 1-1.5 mm without reducing the effectiveness of the labyrinth seal.

In the case of a brush seal, the brushes can be fixedly attached to the inner surface of the ring 3, while their elastic suspension (due to the corrugated bag 5) will reduce the wear of the brushes and increase the life of the seal.

Claims (8)

1. The seal of the rotors of turbomachines, containing a sealing gap, concentric to the axis of the rotor, filled with a working medium, and elements limiting this gap - a rotor and a reciprocal non-rotating part, characterized in that the size of the sealing gap on the operating modes is limited to 0.15-0.25 mm, the non-rotating part is made in the form of a ring, the cross-section of which is U-shaped, and the ring itself is strictly concentric with the rotor axis and is resiliently suspended from a fixed part (for example, a case or an inner ring of a guide device ) using a multilayer package of thin steel red-hot corrugated tapes of the same thickness (for example, from 0.1 to 0.4 mm) or groups of corrugated tapes connected in series from the top of the corrugation to the top of the corrugation, each group consisting of several corrugated tapes assembled corrugation into corrugation without gaps (connected to each other in parallel), and the joints of the tapes are evenly located on the tops of the corrugations, and the gap at the joints is chosen as minimal as possible, but such that allows the displacement of the ends of the tape without overlap at the maximum amplitude n the ring process, and the preliminary radial tightness along the corrugation vertices was carried out during assembly by shifting to the axis of the ring semirings, which are fixed on a fixed body part (or the inner ring of the guide apparatus), and the residual corrugation bend on the operating modes as a result is 0.05-0.1 mm, and on the side wall of the ring a protrusion is fixedly fixed, which enters with a gap around the perimeter of the protrusion in the upper half-ring and ribbon of the packet, the value of which is greater than the maximum possible amplitude of the precession of the ring, and from the inside at the side walls of the ring formed pockets equally spaced circumferentially, and between these walls and the ends of the mating half-rings are guaranteed clearance, and the direction of corrugations of corrugated strips formed perpendicularly or at an acute angle relative to the rotor axis. 2. The sealing of the rotors of the turbomachines according to claim 1, characterized in that the package is made of two parts (packages) located one after the other along the axis of the rotor, while the corrugated vertices of one part are shifted half a step in the circumferential direction relative to the corrugated vertices of the second part. 3. The seal of the rotors of the turbomachines according to claim 1, characterized in that the package is made of two parts (packages) located one after the other along the axis of the rotor, while the corrugation vertices on each part of the package, comprising a pair, form a “chevron”, the axis of symmetry which is perpendicular to the axis of the rotor. 4. The sealing of the rotors of the turbomachines according to any one of claims 1 to 3, characterized in that three or more ball stops uniformly spaced around the circumference, consisting of a housing, and housed therein, are pressed into the protrusions of the side wall of the U-shaped ring from the higher pressure side the possibility of free rotation of a steel hardened ball, and between the ball and the ends of the half rings there is a guaranteed clearance. 5. The sealing of the rotors of the turbomachines according to claim 4, characterized in that the joints of all the tapes are located in the upper vertical section and two adjacent to it on the right and left, alternating the joints of the tapes so that the adjacent tapes do not have joints in one section, and the tape joint resting on the ring is located in a vertical plane. 6. The sealing of the rotors of the turbomachines according to claim 5, characterized in that a generated soft layer is fixed on the inner surface of the ring. 7. The seal of the rotors of the turbomachines according to claim 6, characterized in that the U-shaped ring is made of a material with the same coefficient of linear temperature elongation as the material of the rotor. 8. The seal of the rotors of the turbomachines according to claim 6, characterized in that the U-shaped ring is made of a softer material than the material of the rotor, for example, of polymer, carbon fiber, and smooth corrugated tapes are installed between the ring and the bag and the half rings and the bag on the outside red tape from the same material as the corrugated tape package.

Images