Efficient steam turbine last-stage guide vane dehumidification method

Abstract

The invention discloses an efficient steam turbine last-stage guide vane dehumidification method, and relates to a movable vane dehumidification method. The problems that an existing guide vane dehumidification technology is low in efficiency and not suitable for marine steam turbines or industrial steam turbines are solved. Compared with other guide vane dehumidification schemes, the dehumidification efficiency is improved, the seventh end steam seal is additionally arranged at the front end of the steam inlet end of the steam turbine, the pressure of steam leaked from the seventh end steam seal is controlled, the leaked steam is introduced into a main stream to be further utilized, and the efficiency of the steam turbine is improved; the through holes are formed in part of the last-stage guide vane, steam in the seventh-end steam seal is sprayed out of the through holes of the last-stage guide vane and converged into the steam main flow, the average enthalpy value of the steam main flow is increased, and the humidity of the steam main flow is reduced; and large water drops carried by steam flow in a blade runner, large water drops rebounded into the runner from the wall surface and secondary water drops generated by tearing of the rear edge of the movable blade are crushed, so that serious water erosion caused by collision of the large water drops to the movable blade is avoided. The invention belongs to the technical field of steam turbine guide vane dehumidification.

Description

Technical Field

[0001] The invention relates to a method for dehumidifying a last-stage guide vane, in particular to a method for dehumidifying a last-stage guide vane of a steam turbine with high efficiency, and belongs to the technical field of dehumidifying a guide vane of a steam turbine. Background Art

[0002] For fossil, nuclear, and marine steam turbines, the steam working medium will spontaneously condense to form condensation nuclei and wet steam when the pressure decreases during the work process in the flow channel. As the steam expands further in the flow section of the turbine, the condensation nuclei in the wet steam continue to grow, producing primary water droplets. At the same time, some water droplets collide and deposit on the solid wall of the blade to form a water film. When the water film develops to a certain stage, it is torn by the steam shear stress at the trailing edge of the blade to form larger secondary water droplets. The secondary water droplets themselves have a large momentum, and they continuously collide with the leading edge area of ​​the moving blade, causing the surface material of the moving blade to gradually fall off, resulting in water erosion, reducing the strength and vibration characteristics of the moving blade, and may cause the blade to break, causing serious accidents, seriously affecting the safe and reliable operation of the unit, and the harm to the last-stage moving blade is most significant.

[0003] In order to improve the quality of steam in the last stage of the turbine, a variety of structural designs are applied to the flow. Compared with passive protection, active dehumidification of the last stage moving blades is the fundamental solution to the water erosion problem, such as the widely used guide vane dehumidification technology.

[0004] At present, the guide vane dehumidification technology usually adopts suction, purging, heating and other methods. Among them, the suction scheme will inevitably purify part of the steam while removing the water droplets, which reduces the efficiency. The steam source for heating or purging dehumidification is mostly drawn from new steam, which makes it difficult to fully utilize the work capacity of this part of new steam, reducing the overall efficiency of the unit. In addition, the purging method requires a slit at the end of the trailing edge of the guide vane, but this has certain requirements on the thickness of the trailing edge of the guide vane. Marine steam turbines or industrial steam turbines cannot apply this traditional purging scheme because the blade height is relatively small and the trailing edge of the guide vane is very thin.

[0005] In summary, how to propose a method for dehumidifying the last-stage guide vanes in response to the above-mentioned technical problems has become an urgent problem to be solved by technicians in this field. Summary of the invention

[0006] In view of the above-mentioned deficiencies of the prior art, the present invention provides a highly efficient method for dehumidifying the last-stage guide vanes of a steam turbine.

[0007] The technical solution of the present invention is: a high-efficiency dehumidification method for the last-stage guide vane of a steam turbine, the steam turbine having a first end steam seal, a second end steam seal, a third end steam seal, a fourth end steam seal, a fifth end steam seal and a sixth end steam seal arranged in sequence from the steam inlet end to the steam exhaust end; the first end steam seal, the second end steam seal and the third end steam seal are all installed on the cylinder body of the steam inlet end of the steam turbine, and the fourth end steam seal, the fifth end steam seal and the sixth end steam seal are all installed on the cylinder body of the steam exhaust end of the steam turbine.

[0008] Furthermore, the method is specifically carried out according to the following steps:

[0009] Step 1: A first steam pipe is installed on the cylinder body between the second end steam seal and the third end steam seal, and the first steam pipe is connected to one end of the end steam seal balance box.

[0010] A second steam pipe is installed on the cylinder body between the fourth end steam seal and the fifth end steam seal, and the second steam pipe is communicated with the other end of the end steam seal balance box.

[0011] Step 2: A third steam pipe is installed on the cylinder body between the first end steam seal and the second end steam seal, and the third steam pipe is connected to one end of the steam seal vacuum pump.

[0012] A fourth steam pipe is installed on the cylinder body between the fifth end steam seal and the sixth end steam seal, and the fourth steam pipe is communicated with the other end of the steam seal vacuum pump.

[0013] Step 3: Add a seventh end steam seal between the third end steam seal and the regulating stage of the steam turbine

[0014] The steam pressure leaking from the seventh end steam seal is controlled by the steam seal teeth of the seventh end steam seal, and the leaking steam pressure is maintained stable and higher than the working pressure of the steam seal balance box and the last stage guide vane.

[0015] The outer ring of the last stage partition is provided with an annular cavity along the circumferential direction, and the seventh end steam seal is connected with the annular cavity through a steam transmission pipe;

[0016] Step 4: The last-stage guide vane in the cylinder is a hollow guide vane, the inner cavity of the hollow guide vane is connected to the annular cavity, through holes are opened on the pressure surfaces of some hollow guide vanes, and the hollow guide vanes with through holes are evenly distributed in the circumferential direction of the cylinder.

[0017] Compared with the prior art, the present invention has the following effects:

[0018] 1. Compared with other guide vane dehumidification schemes, the present invention improves the dehumidification efficiency of the guide vane. By adding a seventh end steam seal 107 at the front end of the steam inlet end of the steam turbine to control the steam pressure leaking from the regulating stage, the sealing ability of the end steam seal at the steam inlet end of the steam turbine is strengthened, and the utilization efficiency of the end steam seal leakage is improved; and the steam leaked from the regulating stage is introduced into the mainstream for further utilization, thereby improving the efficiency of the steam turbine.

[0019] 2. The present invention opens through holes on part of the hollow guide vanes, and the steam in the seventh end steam seal 107 is ejected from the through holes on the hollow guide vanes and merged into the steam mainstream, thereby increasing the average enthalpy value of the steam mainstream and reducing the humidity of the steam mainstream. In addition, large water droplets entrained by the steam flow in the blade flow channel, large water droplets rebounded from the wall into the flow channel, and secondary water droplets generated by tearing of the trailing edge of the guide vane are crushed, thereby reducing the particle size of water droplets, preventing large water droplets from hitting the moving blades to cause serious water erosion, and playing a positive and proactive role in the anti-erosion design of the last-stage moving blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention;

[0021] Figure 2 is an axonometric view of the hollow guide vane in step 4 of the present invention;

[0022] Figure 3 It is a cross-sectional view of the hollow guide vane in step four of the present invention.

[0023] In the figure: 101, first end steam seal; 102, second end steam seal; 103, third end steam seal; 104, fourth end steam seal; 105, fifth end steam seal; 106, sixth end steam seal; 107, seventh end steam seal; 108, steam pipe; 200, steam seal balance box; 300, steam seal vacuum pump. DETAILED DESCRIPTION

[0024] In order to make the purpose, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0025] Specific implementation method 1: Combination Figures 1 to 3 The present embodiment is described as an efficient method for dehumidifying the last-stage guide vanes of a steam turbine. The steam turbine comprises a first end steam seal 101, a second end steam seal 102, a third end steam seal 103, a fourth end steam seal 104, a fifth end steam seal 105 and a sixth end steam seal 106 which are arranged in sequence from the steam inlet end to the steam exhaust end.

[0026] The first end steam seal 101, the second end steam seal 102 and the third end steam seal 103 are all installed on the cylinder body at the steam inlet end of the steam turbine, and the fourth end steam seal 104, the fifth end steam seal 105 and the sixth end steam seal 106 are all installed on the cylinder body at the steam exhaust end of the steam turbine.

[0027] Furthermore, the method is specifically carried out according to the following steps:

[0028] Step 1: A first steam pipe is installed on the cylinder body between the second end steam seal 102 and the third end steam seal 103 , and the first steam pipe is connected to one end of the end steam seal balance box 200 .

[0029] A second steam pipe is installed on the cylinder body between the fourth end steam seal 104 and the fifth end steam seal 105 , and the second steam pipe is connected to the other end of the end steam seal balance box 200 .

[0030] Step 2: A third steam pipe is installed on the cylinder body between the first end steam seal 101 and the second end steam seal 102 , and the third steam pipe is connected to one end of the steam seal vacuum extractor 300 .

[0031] A fourth steam pipe is installed on the cylinder body between the fifth end steam seal 105 and the sixth end steam seal 106 , and the fourth steam pipe is connected to the other end of the steam seal vacuum extractor 300 .

[0032] Step 3: Add a seventh end steam seal 107 between the third end steam seal 103 and the regulating stage of the steam turbine

[0033] The steam pressure leaking from the seventh end steam seal 107 is controlled by the steam seal teeth of the seventh end steam seal 107, and the leaking steam pressure is maintained stable and higher than the working pressure of the steam seal balance box 200 and the last stage guide vane.

[0034] An annular cavity is provided on the outer ring of the final-stage partition along the circumferential direction, and the seventh-end steam seal 107 is connected to the annular cavity through a steam pipe 108 .

[0035] Step 4: The last-stage guide vane in the cylinder is a hollow guide vane, the inner cavity of the hollow guide vane is connected to the annular cavity, and through holes are opened on the pressure surface of some hollow guide vanes (i.e., the inwardly concave surface of the blade), and the hollow guide vanes with through holes are evenly distributed in the circumferential direction of the cylinder. With this arrangement, the high-quality steam in the seventh-end steam seal 107 enters the inner cavity of the hollow guide vane through the steam pipe 108 and the annular cavity, and then the steam is ejected from the through hole. On the one hand, the ejected steam merges into the mainstream to improve the efficiency of the steam turbine. On the other hand, the average enthalpy value of the mainstream steam is increased, the humidity of the mainstream steam is reduced, and the large water droplets entrained by the steam flow in the blade flow channel, the large water droplets rebounded from the wall to the flow channel, and the secondary water droplets generated by the tearing of the trailing edge of the moving blade are crushed to prevent large water droplets from hitting the moving blades and causing serious water erosion.

[0036] In the present embodiment, the first end steam seal 101, the second end steam seal 102, the third end steam seal 103, the fourth end steam seal 104, the fifth end steam seal 105 and the sixth end steam seal 106 are all comb-tooth end steam seals. The comb-tooth steam seals include a steam seal sleeve and a steam seal ring. The steam seal sleeve is provided with steam extraction holes. The steam leaked from the comb-tooth end steam seals is extracted by the steam pipe and then transported to the steam seal balance box 200 and the steam seal vacuum pump 300, which effectively prevents the steam from flowing into the atmosphere and further enhances the sealing ability.

[0037] Specific implementation method 2: Combination Figure 1To explain this embodiment, the seventh end steam seal 107 in this embodiment is a comb-tooth end steam seal, and the steam pressure leaking from the regulating stage is controlled by controlling the number and gap of the upper end steam seal teeth on the inner circumference of the seventh end steam seal 107. Other components and connection relationships are the same as those in the first embodiment.

[0038] Specific implementation method three: Combination Figure 2 and Figure 3 To illustrate this embodiment, in this embodiment, the through hole on the hollow guide vane is located at the trailing edge of the inner cavity of the hollow guide vane, and the opening direction of the through hole is toward the trailing edge of the hollow guide vane; such an arrangement ensures that the steam flow ejected from the through hole flows out along the trailing edge, avoiding affecting the mainstream direction of the steam.

[0039] The other components and connection relationships are the same as those in the first or second specific implementation.

[0040] Specific implementation method four: Combination Figures 2 to 3 To illustrate this embodiment, in this embodiment, the through hole on the hollow guide vane is a rectangular through hole, and the rectangular through hole is parallel to the steam outlet edge of the hollow guide vane.

[0041] The other components and connection relationships are the same as those of the first, second or third specific implementation modes.

[0042] Specific implementation method five: Combination Figure 2 and Figure 3 This embodiment is described. In this embodiment, the cross-sectional area of ​​the through hole is A1.

[0043] Furthermore, a plurality of steam extraction holes are opened in a circular array on the seventh end steam seal 107, and the plurality of steam extraction holes are all connected to the steam transmission pipe 108, and the sum of the cross-sectional areas of the plurality of steam extraction holes is A2.

[0044] Furthermore, the cross-sectional area of ​​the inner cavity of the steam transmission pipe 108 is A3, and A1=A2=A3.

[0045] The other components and connection relationships are the same as those of the first, second, third or fourth specific implementation modes.

[0046] The present invention has been disclosed as above in the form of a preferred embodiment, but it is not intended to limit the present invention. Any simple modification, equivalent changes and modifications made to the above implementation cases by any professional and technical personnel who do not deviate from the content of the technical solution of the present invention and based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An efficient method for dehumidifying a last-stage guide vane of a steam turbine, wherein the steam turbine comprises a first end steam seal (101), a second end steam seal (102), a third end steam seal (103), a fourth end steam seal (104), a fifth end steam seal (105) and a sixth end steam seal (106) which are arranged in sequence from a steam inlet end to a steam exhaust end; A first end steam seal (101), a second end steam seal (102) and a third end steam seal (103) are all installed on a cylinder body at a steam inlet end of the steam turbine, and a fourth end steam seal (104), a fifth end steam seal (105) and a sixth end steam seal (106) are all installed on a cylinder body at a steam exhaust end of the steam turbine; Features: The method is specifically carried out in the following steps: Step 1: A first steam pipe is installed on the cylinder body between the second end steam seal (102) and the third end steam seal (103), and the first steam pipe is connected to one end of the end steam seal balance box (200); A second steam pipe is installed on the cylinder body between the fourth end steam seal (104) and the fifth end steam seal (105), and the second steam pipe is connected to the other end of the end steam seal balance box (200); Step 2: A third steam pipe is installed on the cylinder body between the first end steam seal (101) and the second end steam seal (102), and the third steam pipe is connected to one end of the steam seal vacuum pump (300); A fourth steam pipe is installed on the cylinder body between the fifth end steam seal (105) and the sixth end steam seal (106), and the fourth steam pipe is connected to the other end of the steam seal vacuum extractor (300); Step 3: Add a seventh end steam seal (107) between the third end steam seal (103) and the regulating stage of the steam turbine The steam pressure leaking from the seventh end steam seal (107) is controlled by the steam seal teeth of the seventh end steam seal (107), and the leaking steam pressure is kept stable and higher than the working pressure of the steam seal balance box (200) and the last stage guide vane; An annular cavity is provided on the outer ring of the final stage partition along the circumferential direction, and the seventh end steam seal (107) is connected to the annular cavity through a steam transmission pipe (108); Step 4: The last-stage guide vane in the cylinder is a hollow guide vane, the inner cavity of the hollow guide vane is connected to the annular cavity, through holes are opened on the pressure surfaces of some hollow guide vanes, and the hollow guide vanes with through holes are evenly distributed in the circumferential direction of the cylinder.

2. The efficient dehumidification method for the last-stage guide vanes of a steam turbine according to claim 1, characterized in that: The seventh end steam seal (107) is a comb-teeth type steam seal.

3. The efficient steam turbine last-stage guide vane dehumidification method according to claim 1, characterized in that: The opening direction of the through hole on the hollow guide vane faces the trailing edge of the hollow guide vane.

4. The efficient steam turbine last-stage guide vane dehumidification method according to claim 3, characterized in that: The through hole on the hollow guide vane is located at the trailing edge of the inner cavity of the hollow guide vane.

5. The efficient steam turbine last-stage guide vane dehumidification method according to claim 1, characterized in that: The through hole on the hollow guide vane is a rectangular through hole.

6. The efficient steam turbine last-stage guide vane dehumidification method according to claim 5, characterized in that: The rectangular through hole is parallel to the steam outlet edge of the hollow guide vane.

7. The efficient steam turbine last-stage guide vane dehumidification method according to claim 1, characterized in that: The cross-sectional area of ​​the through hole is A1; A plurality of steam extraction holes are formed in a circumferential array on the seventh end steam seal (107), and the plurality of steam extraction holes are all connected to the steam transmission pipe (108), and the sum of the cross-sectional areas of the plurality of steam extraction holes is A2; The cross-sectional area of ​​the inner cavity of the steam transmission pipe (108) is A3, and A1=A2=A3.

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