JP4982476B2 - Radial flow type fluid machine - Google Patents

Description

  The present invention relates to a radial flow type fluid machine.

  Radial flow type fluid machines (for example, radial flow type turbines and centrifugal compressors) are widely used for industrial small turbines because of a relatively large pressure ratio in a single stage. In a radial flow type fluid machine, since a bearing that supports the rotating shaft is installed in the vicinity of the impeller, a shaft seal device (seal) that prevents intrusion of bearing lubricant into the impeller side is provided between the impeller and the bearing. It is installed between.

  This type of shaft seal device is usually constituted by a labyrinth seal or the like, and is installed at two locations in the axial direction between the impeller and the bearing. The labyrinth seal on the bearing side is supplied with a first seal fluid (for example, air) for preventing mixing of the bearing lubricant. On the other hand, the labyrinth seal on the impeller side is supplied with a second seal fluid (for example, a working fluid) for preventing the first seal fluid supplied to prevent the bearing lubricant from entering the impeller side. ing. And between these two labyrinth seals, a discharge flow path for exhausting the two seal fluids is connected, and the discharge flow path is connected to a low pressure source such as a condenser (Patent Document). 1 etc.).

JP 2008-57452 A

  Consider the case where the above technique is applied to a radial flow turbine using steam as a working fluid. In this case, steam before expansion on the upstream side of the turbine is used as the second seal fluid. Since this supply steam has a relatively high pressure, it is possible to prevent the bearing lubricant from entering the turbine impeller side. However, part of the supplied steam flows from the labyrinth seal along the rotating shaft toward the turbine impeller, travels radially outward along the rear surface of the turbine impeller, and from the radially outer end of the turbine impeller. It again flows into the turbine flow path.

  Since the steam that has flowed into the turbine flow path again has a pressure higher than the pressure in the turbine flow path section, it is ejected vigorously from the radially outer end of the turbine impeller into the turbine flow path. The seal steam ejected into the turbine flow path in this manner disturbs the flow at the turbine inlet and generates a mixing loss. Moreover, since it interferes with the flow flowing into the turbine, the turbine inflow angle is affected, and the design inflow angle is greatly deflected. These result in increased losses and have a significant effect on turbine performance. In addition, when the supply pressure of the seal steam is high in this way, the amount of exhaust to the discharge flow path also increases and the steam loss increases, so that the turbine performance tends to deteriorate. And since the capacity | capacitance of the vacuum exhaust pump of a condenser increases further, it leads also to the fall of the whole system efficiency by the increase in auxiliary machine capacity | capacitance.

  An object of the present invention is to provide a radial flow type fluid machine that can suppress a performance degradation that occurs when a working fluid is used as a sealing fluid.

(1) In order to achieve the above object, the present invention comprises a radial flow type impeller, a rotating shaft connected to the impeller, a bearing supporting the rotating shaft, and a blade on the impeller. A main flow path through which the working fluid flows, a shaft sealing device provided on the outer peripheral side of the rotating shaft, and a portion where the radially outer end of the impeller is located is connected to the main flow path, and the shaft A working fluid supply channel for guiding the working fluid to the sealing device, and an end of the working fluid supply channel on the shaft sealing device side is opened at an installation position of the shaft sealing device, and the shaft sealing device A part of the working fluid led to is guided to a connecting portion between the main flow path and the working fluid supply flow path along the back surface of the impeller, and the shaft seal device is connected via the working fluid supply flow path. Will be referred to again .

(2) In the above (1), preferably, on the outer peripheral side of the rotating shaft, another shaft sealing device provided closer to the bearing than the shaft sealing device, and air is guided to the other shaft sealing device. It is further provided with an air supply flow path, and an exhaust flow path that is provided between the shaft seal device and the other shaft seal device and exhausts the working fluid and air to the outside.

( 3 ) In the above (1) or (2), preferably, the shaft sealing device is a labyrinth seal provided on an outer periphery of the rotating shaft.

( 4 ) In the above ( 3 ), preferably, the end portion on the shaft seal device side in the working fluid supply flow path is opened between a plurality of teeth forming the labyrinth seal.

( 5 ) In the above (2), preferably, the working fluid flowing through the main flow path is steam, a condenser chamber connected to the exhaust flow path, and the condenser chamber in the exhaust flow path An exhaust pressure adjusting container provided on the upstream side, and a pressure adjusting means provided on the upstream side of the exhaust pressure adjusting container in the exhaust flow path for adjusting the pressure of the exhaust pressure adjusting container are further provided.

In one (6) of (1) through (5), preferably, the in main channel further comprises a stationary blade provided on the radially outer side of the wheel, the working fluid supply passage, said static It is assumed that the main flow path is connected between the blade and the impeller.

( 7 ) In any one of the above (1) to ( 6 ) , the impeller is a turbine impeller rotated by a working fluid.

( 8 ) In any one of the above (1) to ( 6 ) , the impeller is a compressor impeller that compresses a working fluid.

  According to the present invention, even if the working fluid is used as the seal fluid, it is possible to suppress the performance deterioration of the radial flow type fluid machine.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a radial flow steam turbine according to a first embodiment of the present invention.

  The steam turbine shown in this figure includes a turbine impeller 2, a turbine nozzle 1, a rotating shaft 5, a bearing 6, an inner casing 8, an outer casing 9, a seal bracket 10, and a first labyrinth seal (first A shaft seal device) 31, a second labyrinth seal (second shaft seal device) 32, a working fluid supply channel 41, an air supply channel 42, and an exhaust channel 43 are mainly provided.

  The radial-flow turbine impeller 2 includes a plurality of moving blades 35 and is connected to a rotating shaft 5 protruding from the back side of the turbine impeller 2. The rotating shaft 5 is supported by a bearing 6 installed at a distance from the turbine impeller 2. The turbine nozzle (stationary blade) 1 is attached to the inner casing 8 and is covered with an outer casing 9 together with the turbine impeller 2. A moving blade 35 on the turbine impeller 2 is disposed between the inner casing 8 and the outer casing 9, and a main flow path (main flow path) 36 through which steam (working fluid) flows is formed. A seal bracket 10 is installed on the back side of the turbine impeller 2 in the inner casing 8.

  A first labyrinth seal (first shaft seal device) 31, a second labyrinth seal (second shaft seal device) 32, and a discharge groove 13 are provided on the inner peripheral side of the seal bracket 10 (that is, the outer peripheral side of the rotary shaft 5). Is provided.

  The first labyrinth seal (first shaft seal device) 31 is provided on the back side of the turbine wheel 2, and the second labyrinth seal (second shaft seal device) 32 is a bearing 6 rather than the first labyrinth seal 31. On the side. A plurality of teeth 11 protruding in a convex shape are processed on the inner periphery (rotation shaft 5 side) of the seal bracket 10 and the outer periphery of the rotation shaft 5 in the present embodiment. Labyrinth seals 31 and 32 are formed at two locations.

  The seal bracket 10 is provided with a seal steam supply hole 16 that guides the working fluid to the first labyrinth seal 31 along the radial direction of the rotary shaft 5. An upstream end of the seal steam supply hole 16 is connected to an impeller end pressure conduction hole 18 provided in the inner casing 8, and a downstream end of the seal steam supply hole 16 is a first labyrinth seal 31. Open to the installation position. The opening on the downstream side in the seal steam supply hole 16 of the present embodiment opens between a plurality of teeth 11 (interdental) forming the first labyrinth seal 31, and more specifically, the first labyrinth. An opening is formed in the central portion of the seal 31.

  The impeller end pressure conduction hole 18 serves to seal the pressure at the radially outer end 17 of the turbine impeller 2 (hereinafter sometimes referred to as “the radially outer end of the turbine impeller”) with the seal steam supply hole 16. In the portion where the radially outer end 17 of the turbine impeller 2 is located, it is connected to the main flow path 36. As shown in FIG. 1, the connecting portion between the impeller end pressure conduction hole 18 and the main flow path 36 is located between the turbine nozzle 1 and the radially outer end 17 of the turbine impeller 2. The impeller end pressure conduction hole 18 in the present embodiment is located on the outer side in the radial direction of the rotating shaft 5 with respect to the seal steam supply hole 16 and is provided annularly on the inner peripheral side of the inner casing 8.

  A working fluid supply channel 41 that guides the seal steam (working fluid) to the first labyrinth seal 31 is formed by the seal steam supply hole 16 and the impeller end pressure conduction hole 18. By the working fluid supply channel 41, static pressure at the radially outer end 17 of the turbine impeller 2 is guided to the opening of the seal steam supply hole 16 to the first labyrinth seal 31.

  By the way, on the back surface (rotation shaft 5 side) of the turbine impeller 2 during turbine operation, the pressure of the root portion 19 of the turbine impeller is caused to open by the centrifugal steam effect caused by the rotation of the turbine impeller 2. The pressure difference in the axial direction of the rotating shaft 5 is generated. Due to this pressure difference, a part of the seal steam introduced from the radial direction of the rotary shaft 5 into the first labyrinth seal 31 through the seal steam supply hole 16 flows toward the root portion 19 of the turbine impeller 2. . Further, the centrifugal force effect due to the rotation of the turbine impeller 2 lowers the pressure of the root portion 19 of the turbine impeller than the static pressure of the outer end portion 17. For this reason, a flow is generated on the rear surface of the turbine impeller 2 from the root portion 19 toward the outer end portion 17 along the rear surface of the turbine impeller 2.

  That is, by connecting the seal steam supply hole 16 and the impeller end pressure conduction hole 18 as described above, a part of the steam flowing in the main flow path 36 is transferred from the outer end 17 of the turbine impeller 2 to the impeller end. Guided to the partial pressure conduction hole 18, (1) the impeller end pressure conduction hole 18 → (2) the seal steam supply hole 16 → (3) the first labyrinth seal 31 → (4) the root part 19 of the turbine impeller 2. Since (5) the outer end portion 17 of the turbine impeller 2 → (6) the impeller end pressure conduction hole 18 flows in this order, a steam circulation flow is generated. Here, the pressure of the steam that is transmitted back to the outer end 17 (the impeller end pressure conduction hole 18) of the turbine impeller 2 through the back surface of the impeller 2 is connected to the impeller end pressure conduction hole 18. Since it becomes the same as the static pressure of the main flow path 36 in the portion, no steam is ejected to the main flow path 36 through the impeller end pressure conduction hole 18. Further, by circulating and using the seal steam in this way, the amount of steam discharged together with the seal air from the exhaust flow path 43 is reduced, so that it is possible to prevent a decrease in turbine performance due to steam loss. Furthermore, since several teeth 11 of the first labyrinth seal 31 are installed between the seal steam supply hole 16 and the root portion 19 of the turbine impeller 2 in the present embodiment, the labyrinth seal effect causes the seal steam to flow. The flow rate can be further reduced.

  On the other hand, a part of the steam ejected from the seal steam supply hole 16 to the first labyrinth seal 31 is on the side of the bearing 6 that is opposite to the turbine impeller 2 due to a pressure difference with the condenser chamber 21 (described later). And is mixed with seal air in the discharge groove 13 and discharged into the condenser chamber 21. Thus, the seal steam flowing toward the discharge groove 13 prevents the seal air or the lubricant of the bearing 6 (bearing lubricant) mixed in the seal air from entering the turbine impeller 2 side.

  Meanwhile, the seal bracket 10 is provided with a seal air supply hole 12 that guides the seal air held at a pressure equal to or higher than the atmospheric pressure in the bearing 6 to the second labyrinth seal 32. The upstream end of the seal air supply hole 12 is connected to an air source (not shown), and the downstream end of the seal air supply hole 12 is open to the installation position of the second labyrinth seal 32. (In the present embodiment, it opens between the teeth of the second labyrinth seal 32, more specifically, opens in the central portion of the second labyrinth seal 32). In this way, the air supply passage 42 that guides the seal air to the second labyrinth seal 32 is formed by the seal air supply hole 12. Seal air introduced from the seal air supply hole 12 to the second labyrinth seal 32 is ejected toward the rotary shaft 5 to prevent the bearing lubricant from entering the turbine impeller 2 side. From the viewpoint of effectively preventing the bearing lubricant from entering, a plurality of seal steam supply holes 16 and seal air supply holes 12 are preferably provided for the seal bracket 10.

  The discharge groove 13 is a groove dug in an annular shape on the inner peripheral side of the seal bracket 10, and is located between the first labyrinth seal 31 and the second labyrinth seal 32. The discharge groove 13 is a groove provided in the seal bracket 10 and connected to a discharge hole 14 provided downward in the vertical direction. The discharge hole 14 is connected to a discharge flow path 15 provided in the inner casing 8, and is further connected to the condenser chamber 21 via an external exhaust pipe 23. That is, the exhaust groove 43 for discharging the working fluid and air guided to the labyrinth seals 31 and 32 to the outside is formed by the discharge groove 13, the discharge hole 14, the discharge flow path 15, and the external exhaust pipe 23. Yes. A part of the working fluid and air ejected from the seal steam supply hole 16 and the seal air supply hole 12 are exhausted by the pressure difference from the condenser chamber 21 (usually maintained at atmospheric pressure or lower). Through the condenser chamber 21. Thereby, sealing air and bearing lubricant can be prevented from entering the turbine impeller 2 side. Further, a valve 24 is installed on the upstream side of the condensate air chamber 21 in the external exhaust pipe 23. When the turbine is stopped, the communication with the condenser chamber 21 can be cut by the valve 24.

  In the steam turbine configured as described above, steam, which is a turbine working fluid, flows into the upstream of the turbine nozzle 1 from a steam supply source (not shown). The steam that has passed through the turbine nozzle 1 expands between the blades 3 of the turbine impeller 2 to rotate the turbine impeller 2 and flows out to the turbine downstream area 4.

Next, the effect of this embodiment will be described.
As described above, the steam turbine according to the present embodiment is connected to the main flow path 36 at a portion where the radially outer end 17 of the turbine impeller 2 is located, and guides the seal steam to the first labyrinth seal 31. A working fluid supply channel 41 is provided, and an end portion of the working fluid supply channel 41 on the first labyrinth seal 31 side is opened to the installation position of the labyrinth seal 31.

  When the steam turbine is configured in this manner, the seal steam drawn from the outer end portion 17 of the turbine impeller can be circulated through the rear surface of the turbine impeller 2, and further, the turbine is transmitted through the rear surface of the turbine impeller 2 to the turbine. The pressure of the seal steam returned to the outer end 17 of the impeller 2 is the same as the static pressure at the inlet portion of the working fluid supply passage 41 (the connecting portion between the impeller end pressure conduction hole 18 and the main passage 36). Become. Thereby, since the seal steam (return seal steam) returned to the outer end portion 17 is not ejected to the main flow path 36, generation of pressure loss due to mixing of the turbine working fluid and the return seal steam can be suppressed.

  Further, in the present embodiment, the seal steam taken in from the outer end portion 17 of the turbine impeller 2 passes through the first labyrinth seal 31 while circulating through the working fluid supply passage 41, so that the labyrinth seal The circulation amount of the seal steam can be reduced by the effect. As a result, the amount of steam drawn in as a seal can be reduced, and a decrease in turbine efficiency due to steam loss can be prevented. In the first labyrinth seal 31 in the present embodiment, the teeth 11 are provided on both the seal bracket 10 side and the rotary shaft 5 side in order to enhance the sealing effect, but either the rotary shaft 5 side or the seal bracket 10 side. Even if the labyrinth seal is configured by installing the teeth 11 on only one of them, the effect of reducing steam loss can be obtained.

  As described above, according to the present embodiment, it is possible to reduce the loss (mixing loss) caused when the seal steam is mixed into the main flow path 36 and to reduce the amount of the seal steam drawn in. The decrease can be suppressed.

  FIG. 2 is a schematic sectional view of a radial flow steam turbine according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the previous figure, and description is abbreviate | omitted (the following figure is also the same).

  The steam turbine shown in this figure is different from the steam turbine of the first embodiment in that an exhaust pressure adjusting container 22 and a pressure adjusting valve (pressure adjusting means) 25 are provided.

  The exhaust pressure adjusting container 22 is installed on the upstream side of the condenser chamber 21 on the external exhaust pipe 23. The pressure adjustment valve 25 is installed on the external exhaust pipe 23 on the upstream side of the exhaust pressure adjustment container 22 (inlet side of the exhaust pressure adjustment container 22). When the opening degree of the pressure adjustment valve 25 is changed, the pressure in the exhaust pressure adjustment container 22 is changed, so that the discharge pressure of the seal steam and the seal air can be adjusted.

  According to the present embodiment configured as described above, the exhaust pressure of the seal steam and the seal air can be adjusted by the pressure adjustment valve 25. Therefore, for example, the pressure in the exhaust pressure adjustment container 22 is changed to the root portion 19 of the turbine impeller 2. By adjusting the pressure to be equal to the static pressure at, the amount of seal steam discharged from the exhaust passage 43 can be significantly reduced. Thereby, since the amount of steam extracted for sealing can be reduced as compared with the first embodiment, it is possible to further prevent a decrease in turbine performance.

  FIG. 3 is a schematic sectional view of a centrifugal compressor according to the third embodiment of the present invention.

  In the first and second embodiments, an example of a steam turbine that supplies steam to operate a radial flow type impeller has been described. However, in this embodiment, an impeller is used as an impeller of a compressor. The case will be described.

  The centrifugal compressor shown in this figure includes a compressor impeller (blade wheel) 7 and a compressor diffuser (static blade) 26 instead of the turbine impeller 2 and the turbine nozzle 1 in the first embodiment. The flow of the vapor that is the working fluid is opposite to that of the first embodiment. In the compressor configured as described above, when the compressor impeller 7 is rotated by a driving device such as a motor, the steam (working fluid) sucked from the compressor inlet 27 passes through the blade 3 of the compressor impeller 7. Compressed while being decelerated and decelerated by the diffuser 26. The means for drawing the pressure at the radially outer end 17 of the compressor impeller 7 into the labyrinth seal 31 as seal steam, and the circulation state of the seal steam by the means are the same as in the first embodiment.

  As described above, even when the present invention is applied to the compressor, it is possible to suppress the mixing loss of the seal steam at the radially outer end 17 of the compressor impeller 7 and to reduce the amount of the seal steam drawn. Therefore, it is possible to suppress the deterioration of the compressor performance due to the seal steam.

  Also in the present embodiment, if the exhaust pressure adjusting container 22 and the pressure adjusting valve 25 are additionally provided on the external exhaust pipe 23 as in the second embodiment, the pressure control valve 25 causes the seal steam and the seal air to be added. Since the exhaust pressure of can be adjusted, it is possible to further prevent a decrease in turbine performance.

1 is a schematic sectional view of a radial flow steam turbine according to a first embodiment of the present invention. The schematic sectional drawing of the radial flow type steam turbine which is the 2nd Embodiment of this invention. The schematic sectional drawing of the centrifugal compressor which is the 3rd Embodiment of this invention.

Explanation of symbols

1 Turbine nozzle (static blade)
2 Turbine impeller 5 Rotating shaft 6 Bearing 7 Compressor impeller 8 Inner casing 10 Seal bracket 11 Teeth 12 Seal air supply hole 13 Discharge groove 14 Discharge hole 15 Discharge flow path 16 Seal steam supply hole 17 Radial outer end in impeller Part 18 Blade end pressure conduction hole 19 Root part 21 Condenser room 26 Compressor diffuser (static vane)
31 1st labyrinth seal 32 2nd labyrinth seal 35 Rotor blade 36 Main flow path 41 Working fluid supply flow path 42 Air supply flow path 43 Exhaust flow path

Claims (8)

A radial-flow impeller,
A rotating shaft connected to the impeller;
A bearing that supports the rotating shaft;
A main flow path in which a wing on the impeller is arranged and a working fluid flows;
A shaft seal device provided on the outer peripheral side of the rotating shaft;
A working fluid supply channel that is connected to the main channel at a portion where the radially outer end of the impeller is located, and that guides the working fluid to the shaft seal device;
An end portion on the shaft seal device side in the working fluid supply channel is open to an installation position of the shaft seal device ,
A part of the working fluid led to the shaft seal device is led to a connection portion between the main flow path and the working fluid supply flow path along the back surface of the impeller, and via the working fluid supply flow path. A radial flow type fluid machine characterized by being guided again to the shaft seal device . The radial flow fluid machine according to claim 1,
On the outer peripheral side of the rotating shaft, another shaft sealing device provided on the bearing side than the shaft sealing device;
An air supply channel for guiding air to the other shaft seal device;
Provided between the other shaft sealing device and the shaft sealing device, radial flow type fluid machine and further comprising an exhaust passage for discharging the hydraulic fluid and air to the outside. The radial flow type fluid machine according to claim 1 or 2,
The shaft-flow device is a labyrinth seal provided on the outer periphery of the rotating shaft. The radial flow type fluid machine according to claim 3 , wherein
An end portion of the working fluid supply flow path on the shaft seal device side opens between a plurality of teeth forming the labyrinth seal. The radial flow type fluid machine according to claim 2, wherein
The working fluid flowing through the main channel is steam,
A condenser chamber connected to the exhaust flow path;
An exhaust pressure regulating container provided on the upstream side of the condenser chamber in the exhaust passage;
A radial flow type fluid machine, further comprising pressure adjusting means provided on an upstream side of the exhaust pressure adjusting container in the exhaust flow path to adjust the pressure of the exhaust pressure adjusting container. The radial flow type fluid machine according to any one of claims 1 to 5 ,
Further comprising a stationary blade provided on the radially outer side of the impeller in the main flow path,
The radial fluid type fluid machine, wherein the working fluid supply channel is connected to the main channel between the stationary blade and the impeller. The radial flow type fluid machine according to any one of claims 1 to 6 ,
A radial flow type fluid machine, wherein the impeller is a turbine impeller rotated by a working fluid. The radial flow type fluid machine according to any one of claims 1 to 6 ,
The impeller is a compressor impeller that compresses a working fluid, and is a radial flow type fluid machine.

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