RU2177572C2 - Contact-free end sealing (variants) - Google Patents

Abstract

FIELD: hydraulic machine engineering, possibly sealing devices of multimode turbomachines. SUBSTANCE: end sealing device includes fixed against rotation axially movable sealing ring and unit for regulating gap. Said ring is fluid-tightly mounted on elastic members by means of secondary rubber sealing in housing and it forms sealing slit together with rotating ring mounted on shaft. Unit for regulating gap is arranged on end sealing surface of sealing ring and it is in the form of double helical gasodynamic grooves joined by means of single inlet with high pressure cavity and oriented in circumferential direction to opposite sides. Duct is branched out from inlet of grooves; said duct is oriented radially downwards and it has depth exceeding that of gasodynamic grooves. In variant duct oriented radially downwards is joined with grooves along their inner diameter by bridges; depth of duct exceeds that of gasodynamic grooves. EFFECT: improved design providing increased carrying capacity and rigidity of gas layer and also possibility for regulating gap at operation of turbomachine at rotation of shaft in any direction. 2 cl, 3 dwg

Description

 The invention relates to the field of hydraulic engineering and can be used in multi-mode turbomachines as mechanical seals.

 A non-contact mechanical seal [1] is known, which consists of a rotary sealing ring that is axially movable and mounted on the elastic elements and sealed on the elastic elements by means of a secondary rubber seal in the housing and forms a sealing gap with a rotating ring mounted on the shaft, and a clearance control device, which is made on the working end surface of the rotating ring in the form of gas-dynamic wedge-shaped grooves connected to the high-pressure cavity with equal sexually-distance from each other. The grooves are located at an angle of at least 10 degrees to the radial line passing through the axis of rotation, directed in the opposite direction to the rotation, create a pumping effect and pump gas into the sealing gap. At the end of the groove, a zone with a high gas pressure is created, from where the gas tends to flow around the circumference and radius. The sealing effect is provided by a smooth gap located below the inner diameter of the grooves. A gas layer of high rigidity is created in the seal, eliminating the contact of the sealing surfaces with possible run-outs and shaft movements.

 The disadvantage of this seal is its limited use due to the dependence on the direction of rotation of the shaft. All turbomachines have a short rotation of the shaft in the opposite direction. With the opposite rotation of the shaft, the grooves begin to pump gas from the sealing gap. The pressure in the gap and the rigidity of the gas layer decreases and the seal closes with the contact of the sealing surfaces. This causes a limited compaction life. In addition, it is necessary for turbomachines, in which it is necessary to seal the working cavity on both sides, to make two identical seals, but with different directions of the gas-dynamic grooves, in order to ensure gas injection into the sealing slots when the shaft rotates. This leads to an increase in the range of manufactured seals.

 The closest in technical essence to the proposed object is a non-contact mechanical seal [1], which consists of a sealing ring fixed in rotation from an axially movable sealing ring mounted on elastic elements through a secondary rubber seal in the housing and forming a sealing gap with a rotating ring mounted on the shaft , and clearance control devices. The clearance control device is made on the sealing end surface of the rotating ring in the form of double spiral-shaped gas-dynamic grooves, which are connected by a single entrance to the high-pressure cavity and are directed in the circumferential direction in opposite directions. In this case, one of the spiral grooves directed against the rotation of the shaft provides gas injection into the sealing gap and creates a zone with high gas pressure. Another groove, directed along the rotation of the shaft, pumps gas from the sealing gap, creating a zone with reduced gas pressure. Gas is sucked into this zone from the sealing gap surrounding the groove. The effect of injection exceeds the effect of pumping and the seal has a positive rigidity of the gas layer. This ensures the reversibility of the seal, that is, the seal is equally operable in both directions of rotation of the shaft, which in turn reduces the risk of wear of the contacting surfaces during operation of the turbomachine.

 A disadvantage of the known device is its low efficiency, since the bearing capacity and rigidity of the gas film is significantly lower than that of seals with traditional single grooves. This is due to the fact that the gas from the high pressure zone intensively flows into the low pressure zone, reducing the gas-dynamic effect. All this can lead to the fact that in some operating modes of the turbomachine the working sealing surfaces will touch. In addition, at low pressures of the medium to be sealed, overflowing into the zone with reduced pressure will be insignificant and a vacuum will form in the pumping grooves, which can lead to destruction of the surfaces of the sealing rings. In particular, the surface of the opposite contact ring, which is usually made of graphite that does not have high strength properties, will experience alternating high-speed impacts from areas with high and very low pressures, which can lead to chipping of the material. This reduces the compaction life.

 The technical problem solved by this invention is to increase the life of the mechanical seal due to the use of a more efficient form of gas-dynamic chambers.

 Option 1. The problem is solved in that in the end contactless seal, consisting of an o-ring fixed in the direction of rotation, mounted on the elastic elements, sealed on the elastic elements by means of a secondary rubber seal in the housing, forming a sealing gap with a rotating ring mounted on the shaft, and devices regulation of the gap located on the sealing end surface of the rotating ring and made in the form of double spiral-shaped gas-dynamic to grooves, which are connected by a single entrance to the high-pressure cavity and directed in the circumferential direction in opposite directions, from the grooves inlet downward in the radial direction, a channel is made whose depth exceeds the depth of the gas-dynamic grooves.

 Option 2. The problem is solved in that in the end contactless seal, consisting of an o-ring fixed in the direction of rotation, mounted on the elastic elements, sealed on the elastic elements by means of a secondary rubber seal in the housing, forming a sealing gap with a rotating ring mounted on the shaft, and devices regulation of the gap located on the sealing end surface of the rotating ring and made in the form of double spiral-shaped gas-dynamic to grooves, which are connected by a single inlet to the high-pressure cavity and directed in the circumferential direction in opposite directions, from the grooves inlet downward in the radial direction, a channel is made that is connected to the grooves by jumpers in the inner diameter of their location, and the channel depth exceeds the depth of the gas-dynamic grooves.

 In FIG. 1 shows a sealing assembly in section; in FIG. 2 - the working end face of the rotating ring with gas-dynamic grooves and a radial channel (option 1); in FIG. 3 - the working end face of the rotating ring with gas-dynamic grooves, a radial channel and jumpers (option 2).

 The non-contact mechanical seal, consisting of non-rotating 1 and rotating 2 rings, which are separated by a thin gas film, is designed to separate the gas (A) and external (B) cavities (Fig. 1). The axially movable sealing ring 1 is fixed from turning by means of protrusions on its outer part entering grooves in the housing 3. It is mounted on the elastic elements 5 hermetically by means of a secondary rubber seal 4 in the housing 3. The sealing ring 1 forms a sealing gap with a rotating ring 2, which is mounted on the sleeve 6. The torque is transmitted using the pin 7. Static seals are carried out by rubber rings 8. The pin 9 fixes the ring 1 from the rotation.

 On the end sealing surface of the rotating ring 2 (Fig. 2) there are double spiral-shaped gas-dynamic grooves 10 and 11, which are connected by a single entrance to the high-pressure cavity and are directed in the circumferential direction in opposite directions. The grooves are located in the annular zone between the outer diameter of the rotating ring and the diameter below which there is a surface that implements the sealing effect.

 Option 1. From the inlet of the grooves down in the radial direction, a channel 12 is made, the depth of which exceeds the depth of the gas-dynamic grooves 10 and 11 (Fig. 2).

 Option 2. From the inlet of the grooves downward in the radial direction, a channel 12 is made, which is connected to the grooves along the inner diameter of their location by jumpers 13 and 14, while the depth of the channel 12 exceeds the depth of the gas-dynamic grooves 10 and 11 (Fig. 3).

 With a certain direction of rotation of the shaft, one of the grooves, for example 10, provides the injection of gas to be sealed into the sealing gap, creating a gas-dynamic force that prevents the contact of rings 1 and 2. In this case, the other groove, in this case 11, pumps gas out of the sealing gap. This gas is pumped back into the sealing cavity and partially enters the inlet of the groove 10.

 The gas injected by the groove 10 creates a zone with increased gas pressure. Gas from this zone tends to leak into the outer and sealed cavities, as well as in the circumferential direction due to the portable movement.

 Option 1. Part of the gas from the groove 10 will flow through the sealing slot in the circumferential direction into the channel 12, but the overflow will be insignificant, since due to the increased depth of the channel 12, pressure will be maintained in it, almost equal to the gas pressure in the cavity being sealed. At the end of the groove 11, a reduced pressure zone is created. This leads to the fact that from the channel 12 through the sealing slot in the circumferential direction will recharge the groove 11, which leads to an increase in the pressure level in the groove 11. Thus, due to the implementation of the channel 12 is a more efficient supply of gas to the zone of reduced pressure, but not by reducing the pressure level in the high pressure zone.

 Option 2. Part of the gas from the groove 10 will flow through the jumper 13 into the channel 12, where there is a gas with a pressure close to the pressure of the medium being sealed. This is because the jumper 13 located between the groove 10 and the channel 12 is shorter than the groove 10, and the injection effect is negligible. That is, the flow from the pressure drop in the jumper 13 exceeds the portable gas flow. This also applies to the identical jumper 14. At the end of the groove 11, a reduced pressure zone is created. This leads to the fact that on the jumper 14 there is a recharge of the groove 11 from the channel 12, which leads to an increase in the pressure level in the groove 11.

 By choosing the shapes of the channel 12 and the jumpers 13 and 14, in particular their width and depth, it is possible to control the amount of flowing gas from the groove 10 to the groove 11. Since the injection effect exceeds the pumping effect, due to a slight decrease in pressure at the end of the groove 10, it can be significantly reduced a pressure drop at the end of the groove 11. This improves the bearing capacity and rigidity of the gas layer of the seal. When changing the direction of rotation of the shaft, the pumping function will be performed by groove 11.

 Thus, the proposed design of the seal will provide increased bearing capacity and rigidity of the gas layer and the ability to control the size of the gap during operation of the turbomachine in any direction of rotation of the shaft, which leads to an increase in the service life of the end contactless seal.

 This seal can be used in multi-mode turbomachines. Especially effective is the application for machines where a change in the direction of rotation of the shaft is possible.

Sources of information
1. The Federal Republic of Germany patent N 3722303 "Face non-contact seal", IPC F 16 J 15/34, 01/19/89.

2. Article I. Goldswain. Enhancing the performance of dry gas seals // Presentation given to the 6 ^th Technical Conference on the Reliability of Centrifugal Machinery (Proceedings of the VI scientific and technical conference "Seals and vibration reliability of centrifugal machines"), Sumy, September 17-20, 1991. - S.295-313., FIG. 1, p. 266, FIG. 16, p. 310k

Claims (2)

 1. A non-contact mechanical seal, consisting of an o-ring fixed from rotation of the o-ring, mounted on the elastic elements tightly by means of a secondary rubber seal in the housing, forming a sealing gap with a rotating ring mounted on the shaft, and a clearance control device located on the end of the sealing surface a rotating ring and made in the form of double spiral-shaped gas-dynamic grooves that are connected by a single input to the floor Stu high pressure and directed in the circumferential direction in opposite directions, characterized in that the entrance flutes down radially formed channel whose depth exceeds the depth of the grooves gasdynamic.  2. A non-contact mechanical seal, consisting of an o-ring fixed from rotation of the axially movable O-ring mounted on the elastic elements hermetically by means of a secondary rubber seal in the housing, forming a sealing gap with a rotating ring mounted on the shaft, and a clearance control device located on the o-ring face a rotating ring and made in the form of double spiral-shaped gas-dynamic grooves that are connected by a single input to the floor Stu high pressure and directed in the circumferential direction in opposite directions, characterized in that the entrance flutes down radially formed channel which is connected with the grooves on the inner diameter of their location by means of bridges, the channel depth exceeds the depth of the grooves gasdynamic.

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