A cooling channel structure in a three-shell steam turbine and a steam turbine

Abstract

The present invention provides a cooling channel structure in a three-layer shell steam turbine and a steam turbine, which are applied to a three-layer shell steam turbine; the three-layer shell steam turbine includes an outer shell, an outer inner shell, an inner shell, a steam inlet chamber, and a rotor, the outer inner shell is wrapped around the outer periphery of the inner shell, and the outer shell is wrapped around the outer periphery of the outer inner shell; the steam inlet chamber is arranged in the inner shell, and a steam flow expansion channel is arranged between the inner shell, the outer inner shell and the rotor on one side of the steam inlet chamber. The present invention has a first, second, third and fourth flow channels, relying on the difference between the steam parameters of the first flow channel (second flow channel) and the third flow channel, reducing the temperature difference and pressure difference loads borne by the inner shell and the outer inner shell, and optimizing the service environment of the high-temperature components of the steam inlet chamber; the fourth flow channel is used to recycle the internally leaked main steam, which has positive significance for ensuring the cylinder efficiency of the steam turbine and avoiding the leakage of high-temperature steam to the end or outside of the outer shell, and ensuring the safe and reliable operation of the steam turbine.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine equipment in a power station, and in particular to a cooling flow channel structure in a three-shell steam turbine and the steam turbine. Background Art

[0002] In order to improve the energy conversion efficiency of steam turbine equipment in power plants, power plants often use technical means to increase steam inlet parameters such as steam temperature and pressure. However, with the increase of steam turbine inlet parameters, the thermal stress level of high-temperature components also increases during the transient process of starting and stopping and the steady-state operation of the unit. Especially for units that participate in deep peak regulation and other frequent load changes, in order to ensure safe, stable and reliable operation throughout their life cycle, the thermal stress and high-temperature creep, fatigue and other damages generated by the above process need to be paid special attention.

[0003] In order to improve the overall efficiency of the unit and meet the requirements of coal consumption control, there are currently three main solutions for the flow modification of the steam turbine: original parameter flow modification, increased parameter flow modification and cross-generation upgrade modification. Among them, the latter two solutions are the most common: such as increasing the steam inlet parameters of the supercritical unit from 24.2MPa(a) / 566℃ / 566℃ to 24.2MPa(a) / 600℃ / 600℃, or upgrading the subcritical unit (16.7MPa(a) / 538℃ / 538℃) to the ultra-supercritical unit parameters (16.7MPa(a) / 600℃ / 600 (or 610, 620)℃). Considering the construction volume of the steam turbine flow modification and the impact on the existing equipment, the high and medium pressure outer shell of the original unit is generally maintained unchanged, and only the high-temperature components related to the internal flow such as the inner shell, rotor and blades are adjusted to maximize the shortening of the construction period and flow modification costs of the steam turbine flow modification.

[0004] For the above-mentioned transformation scheme or the newly developed design with higher parameters, such as: the unit with steam inlet temperature higher than 620℃, there are two main solutions (any one of them can complete the transformation):

[0005] The first method is to develop materials with excellent high-temperature strength properties. Generally, CrMoV steel is used at a temperature level of 566°C, and 12% Cr steel is used at a temperature level of 600°C. The second method is to use steam cooling technology and cooling structure to reduce the service temperature and pressure difference between the internal and external high-temperature components of the turbine, so as to maximize the use limit of ferritic steel.

[0006] For steam turbines with higher steam inlet parameters such as 650℃ and 700℃, it is necessary not only to develop higher temperature resistant alloy steels (such as nickel-based high-temperature alloys), but also to develop advanced cooling technologies to minimize the use of nickel-based high-temperature alloys in turbine components in order to control project costs.

[0007] If the existing steam turbine is to be retrofitted with flow-through parameters, since the high- and medium-pressure outer shells remain unchanged (reuse), when the steam inlet parameters of the unit are greatly improved, the cylinder exhaust parameters will inevitably increase to varying degrees. If the original single-layer inner cylinder or stationary blade holding ring structure is used, the internal high-temperature components can meet the structural strength design requirements by adjusting the component materials because they are new designs. However, due to the increase in the steam inlet temperature, the temperature difference level and thermal stress of the inner and outer walls of the high-temperature components will inevitably increase, which will bring challenges to the assessment of the sealing performance of the cylinder center face; especially for the reused high- and medium-pressure outer cylinders, since they have been in service for several years (generally more than 10 years), the life of the outer shell will inevitably suffer different degrees of loss during the entire life cycle. Therefore, it is necessary to keep the service parameters of the high- and medium-pressure outer shells basically consistent with those before the transformation to the greatest extent possible, so as to ensure the safe, reliable and stable operation of the unit after the parameter upgrade transformation during its entire life cycle. However, the existing single-layer inner shell and other structures cannot meet the above requirements, and there is room for further technical optimization and improvement.

[0008] In order to solve the problem that a single-layer inner shell cannot meet the temperature difference and thermal stress load after the parameter upgrade, the prior art application number CN 201180067356.1 discloses a steam turbine with a three-layer shell, wherein the steam turbine includes a rotor and an inner shell, an outer shell and an outer shell, wherein the steam turbine has a medium-pressure blade group or a low-pressure blade group. Among them, the inner shell is made of a higher quality material than the outer shell; the working medium in the cooling chamber is extracted from the outflow area of ​​the medium-pressure blade group or from the outflow area of ​​the low-pressure blade group through a fluid machine and is cooled through an input-output pipe. This patent improves the internal cooling structure of a steam turbine with a higher steam inlet parameter to a certain extent, but the main limitation of this patent is that it is only for steam turbines with medium and low pressure steam inlet parameters, and the steam inlet pressure is relatively low, so that an external fluid mechanical device (such as a fan, etc.) can be used to provide power to transport the cooling working medium to the cooling chamber, which requires additional cooling pipelines and control adjustments, and the cooling system is complex, and there is a risk of cooling failure caused by fluid mechanical failure. Summary of the invention

[0009] In view of the shortcomings of the prior art mentioned above, the object of the present invention is to provide a cooling channel structure and a steam turbine in a three-layer shell turbine, which is used to solve the problem in the prior art that the pressure mechanical load and thermal stress load on the inner and outer walls of the high-temperature components are difficult to control after the turbine parameter upgrade modification.

[0010] To achieve the above-mentioned purpose and other related purposes, the present invention provides a cooling flow channel structure in a three-layer shell steam turbine, which is applied to the three-layer shell steam turbine; the three-layer shell steam turbine comprises an outer shell, an outer inner shell, an inner shell, a steam inlet chamber, and a rotor, the outer inner shell is wrapped around the outer periphery of the inner shell, and the outer shell is wrapped around the outer periphery of the outer inner shell; the steam inlet chamber is arranged in the inner shell, a steam flow expansion channel is formed between the inner shell, the outer inner shell and the rotor on one side of the steam inlet chamber, and a plurality of sealing rings are arranged between the inner shell, the outer inner shell and the rotor on the other side, and a sealing ring chamber is formed between adjacent sealing rings; a first flow channel is arranged between the inner wall surface of the outer inner shell and the outer wall surface of the inner shell, and one end of the first flow channel is communicated with a certain sealing ring chamber;

[0011] A second flow channel is provided in the inner shell, one end of the second flow channel is connected to the first flow channel, and the other end of the second flow channel is connected to the steam flow expansion channel;

[0012] A third flow channel is provided between the outer wall surface of the outer inner shell and the inner wall surface of the outer shell, and the third flow channel is connected with the steam flow expansion channel and the steam leakage outlet of a sealing ring chamber;

[0013] The steam flow expansion channel communicated with the second flow channel and the steam flow expansion channel communicated with the third flow channel are sequentially arranged along the expansion direction of the steam in the steam inlet chamber.

[0014] Preferably, a fourth flow channel is provided in the inner shell, one end of the fourth flow channel is connected to a sealing ring chamber, and the other end is connected to the steam flow expansion channel; the steam flow expansion channel connected to the fourth flow channel is arranged between the steam flow expansion channel connected to the second flow channel and the steam flow expansion channel connected to the third flow channel; a sealing ring chamber connected to the fourth flow channel, a sealing ring chamber connected to the first flow channel, and a sealing ring chamber connected to the third flow channel are arranged in sequence along the opposite direction of the steam expansion direction in the steam inlet chamber.

[0015] Preferably, the outer shell, the outer inner shell and the inner shell all include an upper half and a lower half, and the upper half and the lower half are fixedly connected on the center dividing plane; the outer shell and the outer inner shell, and the outer inner shell and the inner shell are all circumferentially fixedly connected; an axial seal is also provided between the outer inner shell and the inner shell, and the axial seal is used for axial positioning of the outer inner shell and the inner shell and sealing of the first flow channel.

[0016] Preferably, the axial seal includes a groove circumferentially opened on the inner wall surface of the outer inner shell, and a boss circumferentially arranged on the outer wall surface of the inner shell, and the boss is engaged in the groove and fixed by a plurality of pins; the axial seal divides the chamber between the outer inner shell and the inner shell into two parts, the first flow channel is one part, and the other part is a connecting cavity; the end of the connecting cavity away from the axial seal is connected to the steam flow expansion channel; the end of the fourth flow channel away from the sealing ring is connected to the steam flow expansion channel through the connecting cavity.

[0017] Preferably, a fourth flow channel rectifying chamber is further provided between the fourth flow channel and the connecting chamber, and the fourth flow channel rectifying chamber is opened in the inner shell; the steam inlet of the fourth flow channel rectifying chamber is connected to the fourth flow channel, the steam outlet of the fourth flow channel rectifying chamber is connected to the steam outlet of the connecting chamber, and there is an angle a1 between the steam outlet of the fourth flow channel rectifying chamber and the steam flow expansion channel, and the range of the angle a1 is 90°≤a1<180°.

[0018] Preferably, the cross-sectional shape of the steam outlet channel of the fourth flow channel rectifying cavity can be a constant cross-section, a gradually expanding cross-section, or a gradually contracting cross-section; there is an angle a2 between the cross-sectional profile of the steam outlet channel of the fourth flow channel rectifying cavity and its center line, and the range of the angle a2 is 0°≤a2<5°.

[0019] Preferably, the cooling flow channel structure in the three-shell steam turbine further includes a supplementary steam flow channel, the supplementary steam flow channel simultaneously passes through the outer inner shell and the outer shell, and is connected to the connecting cavity; the supplementary steam flow channel and the third flow channel are not connected to each other; the supplementary steam flow channel is connected to a supplementary steam pipeline device.

[0020] Preferably, a steam extraction chamber is further provided in the outer and inner shells, and the steam extraction chamber is communicated with the steam flow expansion channel.

[0021] Preferably, the high temperature resistance of the inner shell material is not lower than the high temperature resistance of the outer inner shell material.

[0022] To achieve the above-mentioned object and other related objects, the present invention further provides a steam turbine, comprising the cooling channel structure in the above-mentioned three-shell steam turbine.

[0023] As described above, the cooling channel structure in the three-layer shell steam turbine and the steam turbine of the present invention have the following beneficial effects:

[0024] 1. The cooling channel structure in a three-layer shell steam turbine and the steam turbine according to the present invention are provided with a three-layer shell of an inner shell, an outer inner shell and an outer shell, a first channel is provided between the inner wall surface of the outer inner shell and the outer wall surface of the inner shell, a fourth channel and a second channel are provided in the inner shell, the second channel is connected to the first channel, and the steam flow expansion channel connected to the second channel, the steam flow expansion channel connected to the fourth channel, and the steam flow expansion channel connected to the third channel are arranged in sequence along the steam expansion direction in the steam inlet chamber; the sealing ring chamber connected to the fourth channel, the sealing ring chamber connected to the first channel, and the sealing ring chamber connected to the third channel are arranged in sequence along the opposite direction of the steam expansion direction in the steam inlet chamber.

[0025] Because the second flow channel and the steam flow expansion channel are located upstream of the fourth flow channel and the steam flow expansion channel, the pressure of the steam at the second flow channel and the steam flow expansion channel is higher than the pressure of the steam at the fourth flow channel and the steam flow expansion channel; and because the second flow channel is connected to a certain sealing ring chamber after being connected to the first flow channel, and the fourth flow channel is connected to a certain sealing ring chamber, under the natural pressure difference between the second flow channel and the steam flow expansion channel and the fourth flow channel and the steam flow expansion channel, the steam flows from the steam flow expansion channel → the second flow channel → the first flow channel → the sealing ring → the fourth The flow channel → steam flows through the expansion channel for a cycle, so that the inner shell bears the temperature difference and pressure difference load between the main steam and the steam in the second flow channel (the first flow channel), and the outer inner shell bears the temperature difference and pressure difference load between the steam in the second flow channel (the first flow channel) and the third flow channel, which effectively reduces the temperature difference and pressure difference load that the inner shell and the outer inner shell need to bear (the temperature difference and pressure difference load between the main steam and the steam in the third flow channel borne by the single-layer inner shell in the prior art), and has a positive effect on the safe service of the inner shell in the steam turbine that bears the high-temperature and high-pressure steam.

[0026] 2. The cooling flow channel structure and the steam turbine in the three-layer shell steam turbine involved in the present invention are provided with a fourth flow channel. Relying on the pressure difference between the fourth flow channel and the second flow channel, while reducing the temperature difference and pressure difference load borne by the inner shell and the outer inner shell, the main steam leaking inside the steam turbine is also recovered, and merged with the steam flow expansion channel through the fourth flow channel, and then continues to expand and do work, thereby ensuring the cylinder efficiency of the steam turbine and avoiding leakage of high-temperature steam to the outside, thereby ensuring the safe operation of the steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the cooling channel structure in the three-shell steam turbine with supplementary steam channel in the present invention;

[0028] Figure 2 It is a schematic diagram of the cooling channel structure in the three-layer shell steam turbine without supplementary steam channel in the present invention;

[0029] Figure 3 It is a schematic diagram of the cooling flow channel structure in the three-layer steam turbine with a supplementary steam flow channel and a fourth flow channel rectifying cavity in the present invention;

[0030] Figure 4 It is a schematic diagram of the cooling flow channel structure in the three-layer steam turbine without supplementary steam flow channel and having a fourth flow channel rectifying cavity in the present invention;

[0031] Figure 5 It is a schematic diagram showing that the cross-sectional shape of the steam outlet of the rectifying cavity of the fourth flow channel in the present invention is a uniform cross-sectional shape;

[0032] Figure 6 It is a schematic diagram showing that the cross-sectional shape of the steam outlet of the rectifying cavity of the fourth flow channel in the present invention is a gradually expanding cross-sectional shape;

[0033] Figure 7 It is a schematic diagram showing that the cross-sectional shape of the steam outlet of the fourth flow channel rectifying cavity in the present invention is a tapered cross-sectional shape.

[0034] Description of reference numerals:

[0035] 1. Outer shell; 2. Outer and inner shells; 3. Inner shell; 4. Rotor; 5. First flow channel; 6. Fourth flow channel; 7. Second flow channel; 8. Steam inlet chamber; 9. Connecting chamber; 10. Third flow channel; 11. Pin; 20. Moving blades; 21. Stationary blades; 30. Steam flowing through the inner shell; 31. Steam flowing through the outer and inner shells; 32. Internal leakage of main steam; 33. Steam leaking downstream from the first flow channel; 34. Steam leaking upstream from the first flow channel; 40. Supplementary steam pipeline device; 41. Supplementary steam flow channel; 50. Steam extraction chamber; 51. Fourth flow channel rectifying chamber. DETAILED DESCRIPTION

[0036] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0037] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0038] like Figure 1 As shown, the present invention provides a cooling channel structure in a three-layer shell steam turbine. For the convenience of description, the flow direction of the steam through the expansion channel is defined as the downstream, and the opposite direction of the flow direction of the steam through the expansion channel is defined as the upstream. Figure 1 — Figure 4 As shown, the right side of the paper is downstream and the left side of the paper is upstream.

[0039] like Figure 1 — Figure 4 As shown, the present invention provides a cooling channel structure in a three-layer shell steam turbine, which is applied to the three-layer shell steam turbine; the three-layer shell steam turbine includes an outer shell 1, an outer inner shell 2, an inner shell 3, a steam inlet chamber 8, and a rotor 4, the outer inner shell 2 is wrapped around the outer periphery of the inner shell 3, and the outer shell 1 is wrapped around the outer periphery of the outer inner shell 2; the steam inlet chamber 8 is arranged in the inner shell 3, and a steam flow expansion channel is formed between the inner shell 3, the outer inner shell 2 and the rotor 4 downstream of the steam inlet chamber 8, the steam in the steam flow expansion channel between the inner shell 3 and the rotor 4 is the inner shell flow steam 30, and the steam in the steam flow expansion channel between the outer inner shell 2 and the rotor 4 is the outer inner shell flow steam 31. A plurality of sealing rings are arranged between the upstream inner shell 3, the outer inner shell 2 and the rotor 4, and a sealing ring chamber is formed between adjacent sealing rings;

[0040] A first flow channel 5 is provided between the inner wall surface of the outer inner shell 2 and the outer wall surface of the inner shell 3, and the left end of the first flow channel 5 is connected to a sealing ring chamber upstream;

[0041] A second flow channel 7 is provided in the inner shell 3, the left end of the second flow channel 7 is connected to the first flow channel 5, and the right end is connected to the inner shell through-flow steam 30;

[0042] A third flow channel 10 is provided between the outer wall surface of the outer inner shell 2 and the inner wall surface of the outer shell 1, and the third flow channel 10 is connected with the downstream end of the steam flow expansion channel and the steam leakage outlet of a certain upstream sealing ring chamber;

[0043] The steam flow expansion channel connected to the second flow channel 7 and the steam flow expansion channel connected to the third flow channel 10 are sequentially arranged along the steam expansion direction in the steam inlet chamber 8 .

[0044] The cooling channel structure in the three-layer shell steam turbine of the present invention is provided with a second channel 7 in the inner shell 3, and the right end of the second channel 7 is connected with the inner shell through-flow steam 30, the second channel 7 is connected with the first channel 5, and the first channel 5 is arranged between the inner wall surface of the outer inner shell 2 and the outer wall surface of the inner shell 3, so that the main steam will enter the second channel 7 when it expands and flows through the second channel 7, and enter the first channel 5 through the second channel 7, so that the inner shell 3 bears the main steam and the second channel 7 (the first channel 5) ) in the third flow channel 10; when the main steam expands and does work to enter the third flow channel 10, the outer inner shell 2 bears the temperature difference and pressure difference load between the steam in the second flow channel 7 (first flow channel 5) and the third flow channel 10, so that the gradient of the temperature difference and pressure difference between the inner shell 3 and the outer inner shell 2 is reduced, and the temperature difference and pressure difference load that the inner shell 3 and the outer inner shell 2 need to bear is effectively reduced (in the prior art, the single-layer inner shell 3 bears the temperature difference and pressure difference load between the main steam and the steam in the third flow channel 10).

[0045] Preferably, Figure 1 — Figure 4 As shown, in order to recover the steam in the first flow channel 5 and the internal leakage main steam 32, a fourth flow channel 6 is provided in the inner shell 3, the left end of the fourth flow channel 6 is connected to a sealing ring chamber, and the right end is connected to the steam behind a certain stage of moving blades 20 downstream; the downstream position of the steam connected to the fourth flow channel 6 is between the downstream position of the steam connected to the second flow channel 7 and the downstream position of the steam connected to the third flow channel 10, that is, the second flow channel 7, the fourth flow channel 6, and the third flow channel 10 are arranged in sequence from upstream to downstream along the expansion direction of the main steam. A sealing ring chamber connected to the fourth flow channel 6, a sealing ring chamber connected to the first flow channel 5, and a sealing ring chamber connected to the third flow channel 10 are arranged in sequence along the opposite direction of the steam expansion direction in the steam inlet chamber 8.

[0046] In this embodiment, Figure 1 — Figure 4As shown, a plurality of sealing rings are arranged on the left side (upstream) of the steam inlet chamber 8, which are used to block or control the leakage of the main steam on the one hand, and on the other hand, to balance the axial thrust generated by the main steam expansion work flowing downstream on the stationary blades 21 on the inner casing 3 and the outer inner casing 2, so as to realize the thrust self-balancing of the inner casing 3 and the outer inner casing 2. Furthermore, a plurality of sealing rings are far away from the outer casing 1, especially away from the end steam seal area of ​​the outer casing 1. In this embodiment, the internally leaking main steam 32 flows upstream through three sealing ring chambers and enters the fourth flow channel 6 (the several sealing rings of the internally leaking main steam 32 leaking upstream are the first-gear sealing rings); the steam 33 leaking downstream from the first flow channel flows downstream through a sealing ring chamber and enters the fourth flow channel 6 (the several sealing rings of the steam 33 leaking downstream from the first flow channel are the second-gear sealing rings); the steam 33 leaking downstream from the first flow channel flows upstream through four sealing ring chambers and enters the third flow channel 10 (the several sealing rings of the steam 33 leaking upstream from the first flow channel are the third-gear sealing rings).

[0047] Further, such as Figure 1 — Figure 4 As shown, a plurality of circles of stationary blades 21 are installed on the inner shell 3 and the outer inner shell 2 on the right side (downstream) of the steam inlet chamber 8 through grooves, and a plurality of circles of moving blades 20 are installed on the rotor 4 on the right side (downstream) of the steam inlet chamber 8 through grooves. The cavity formed by the interconnection of each circle of stationary blades 21 and moving blades 20 constitutes a steam flow expansion channel. High-temperature, high-pressure, and high-enthalpy steam is introduced into the steam inlet chamber 8 and flows along the steam flow expansion channel. As the steam expands and works, the internal energy of the steam is converted into the mechanical energy of the moving blades 20, thereby driving the rotor 4 to rotate. During the process of steam expansion and work, the pressure and temperature of the steam gradually decrease. In this embodiment, an adjacent circle of stationary blades 21 and moving blades 20 is a blade stage, and the main steam will be depressurized by a blade stage every time it passes through a blade stage. In this embodiment, according to the characteristics of steam flow pressure reduction, there is a natural pressure difference between the steam in the second flow channel 7 and the steam in the fourth flow channel 6, and the magnitude of the pressure difference is the pressure drop of a blade stage.

[0048] Furthermore, in this embodiment, the first flow channel 5 is an interlayer cavity between the inner shell 3 and the outer inner shell 2, the second flow channel 7 is a plurality of cooling holes provided on the inner shell 3, the third flow channel 10 is an interlayer cavity between the outer inner shell 2 and the outer shell 1, and the fourth flow channel 6 is a plurality of leakage steam recovery holes provided on the inner shell 3. The aperture, quantity and position of the cooling holes and the leakage steam recovery holes are determined according to the thermal parameters of the main steam and blades at various levels, the material strength of the inner shell 3, the outer inner shell 2 and the outer shell 1, and the sealing performance of the center plane.

[0049] Preferably, Figure 1 — Figure 4 As shown, Figure 1 — Figure 4 All of them are longitudinal cross-sectional views. The outer shell 1, the outer inner shell 2, and the inner shell 3 all include an upper half and a lower half, and the upper half and the lower half are fastened and connected by bolts on the center plane; the outer shell 1 and the outer inner shell 2, and the outer inner shell 2 and the inner shell 3 are circumferentially fixedly connected by a number of pins 11; an axial seal is also provided between the outer inner shell 2 and the inner shell 3, and the axial seal is used for axial positioning of the outer inner shell 2 and the inner shell 3 and sealing of the first flow channel 5. Further, in this embodiment, the inner shell 3 is vertically supported on the horizontal center plane of the outer shell 1 by means of the bracket of the center plane, and the outer inner shell 2 is vertically supported on the horizontal center plane of the outer shell 1 by means of the bracket of the center plane.

[0050] Further, such as Figure 1 — Figure 4 As shown, in this embodiment, the axial seal includes a groove circumferentially provided on the inner wall surface of the outer inner shell 2, and a boss circumferentially provided on the outer wall surface of the inner shell 3, the boss is engaged in the groove and fixed by a plurality of pins 11; the axial seal divides the sandwich cavity between the outer inner shell 2 and the inner shell 3 into two parts, the first flow channel 5 is one part, and the other part is the connecting cavity 9; the lower end of the connecting cavity 9 is connected to the steam flow expansion channel; the right end of the fourth flow channel 6 is connected to the steam flow expansion channel through the connecting cavity 9. Further, in this embodiment, the lower end of the connecting cavity 9 is at an angle of 90° to the steam flow expansion channel, and in other embodiments, the lower end of the connecting cavity 9 and the steam flow expansion channel may also be at other angles.

[0051] Preferably, Figure 3 , Figure 4 As shown, in order to ensure that when the steam passing through the second flow channel 7 merges into the steam flow expansion channel again, the disturbance to the main steam or the additional unbalanced steam force on the rotor 4 is minimized. A fourth flow channel rectifying chamber 51 is also provided between the fourth flow channel 6 and the connecting chamber 9. The fourth flow channel rectifying chamber 51 is opened in the inner shell 3; the steam inlet of the fourth flow channel rectifying chamber 51 is connected to the right end of the fourth flow channel 6, and the steam outlet of the fourth flow channel rectifying chamber 51 is connected to the steam outlet of the connecting chamber 9, and there is an inclination angle between the steam outlet of the fourth flow channel rectifying chamber 51 and the steam flow expansion channel. Further, as Figure 5 — Figure 7 As shown, the angle a1 between the center line of the steam outlet of the fourth flow channel rectifying cavity 51 and the steam flow expansion channel is 90°≤a1<180, and the preferred angle range of a1 is: 100° <a1<150°。

[0052] Preferably, Figure 5 — Figure 7As shown, the cross-sectional shape of the steam outlet of the fourth flow channel rectifying cavity 51 is a uniform cross-sectional shape, a gradually expanding cross-sectional shape, or a gradually contracting cross-sectional shape. When the cross-sectional shape of the steam outlet of the fourth flow channel rectifying cavity 51 is a uniform cross-sectional shape, as shown in FIG. Figure 5 As shown, the cavity wall of the fourth flow channel rectifying cavity 51 is parallel to the center line of the fourth flow channel rectifying cavity 51, so the angle between the cavity wall of the fourth flow channel rectifying cavity 51 and the center line of the fourth flow channel rectifying cavity 51 is 0°; when the cross-sectional shape of the steam outlet of the fourth flow channel rectifying cavity 51 is a gradually expanding cross-section or a gradually contracting cross-section, as shown in FIG. Figure 6 , Figure 7 As shown, there is an angle a2 between the cavity wall of the fourth flow channel rectifying cavity 51 and the center line of the fourth flow channel rectifying cavity 51, and the angle of the angle a2 is: 0°<a2<5°, preferably 0°<a2<3.5°. Further, in this embodiment, the fourth flow channel rectifying cavity 51 connects all the fourth flow channels 6 within a certain arc range within the circumferential surface of the inner shell 3, and the position of the fourth flow channel rectifying cavity 51 is set according to the position and number of the fourth flow channels 6, and can be set separately in the upper half or lower half of the inner shell 3, or can be arranged symmetrically in the upper half and the lower half.

[0053] Preferably, Figure 1 , Figure 3 As shown, in order to ensure that the rotor 4 can rotate additionally to output mechanical work under some special operating conditions (for example, when the power grid needs to supply power in excess of the load during peak hours), the cooling channel structure in the three-layer shell steam turbine also includes a supplementary steam pipeline device 40 and a supplementary steam channel 41. The supplementary steam channel 41 penetrates both the outer and inner shells 2 and the outer shell 1, and is connected to the connecting cavity 9; the supplementary steam channel 41 is not connected to the third channel 10; the supplementary steam channel 41 is connected to the supplementary steam pipeline device 40, and the operator can introduce an appropriate amount of steam into the supplementary steam channel 41 through the supplementary steam pipeline device 40 and into the connecting cavity 9, and then do work in the steam flow expansion channel.

[0054] Preferably, Figure 1 — Figure 4 As shown, in order to realize the cooling channel structure in the three-layer shell steam turbine has the function of supplying heat to the outside, a steam extraction chamber 50 is also provided in the outer inner shell 2, and the steam extraction chamber 50 is connected to the steam flow expansion channel. Further, in this embodiment, a throttling regulating device is also provided on the port of the steam extraction chamber 50, and the operator can adjust the amount of steam extraction according to the throttling regulating device, thereby realizing external heat supply. In this embodiment, the throttling regulating device adopts a valve or a rotating partition.

[0055] Preferably, in order to reduce the manufacturing cost of the cooling channel structure in the three-layer shell steam turbine, the high temperature resistance of the material of the inner shell 3 is not lower than the high temperature resistance of the material of the outer inner shell 2. In this embodiment, the inner shell 3 bears the pressure difference and temperature difference between the main steam in the steam inlet chamber 8 and the steam in the first flow channel 5; the outer inner shell 2 bears the pressure difference and temperature difference between the steam in the first flow channel 5 and the steam in the third flow channel 10. The material of the inner shell 3 is 12% Cr steel with a temperature grade of 600°C, the outer inner shell 2 is CrMoV steel or CrMo steel with a temperature grade of 566°C, and the material of the outer shell 1 is CrMo steel or carbon steel. In other embodiments, the materials of the outer inner shell 2 and the outer shell 1 can also be the same as those of the inner shell 3, but the cost will be relatively high.

[0056] The present invention relates to a cooling channel structure in a three-shell steam turbine. A set of data is now provided to explain in detail how the inner shell 3 and the inner and outer shells 1 withstand relatively low pressure and temperature differences.

[0057] First, main steam with an inlet pressure of 28 MPa(a) and a temperature of 600°C is introduced into the steam inlet chamber 8. The main steam is divided into two paths, one path expands and does work downstream of the steam flow expansion channel (along the flow direction of the main steam), and the other path flows upstream of the steam flow expansion channel (i.e., internal leakage main steam 32, which passes through the first-stage sealing ring and enters the fourth flow channel 6, and the flow rate of the internal leakage main steam 32 is m3 t / h). When the main steam flows downstream and the inner shell flow steam 30 flows to the second flow channel 7, the steam pressure at this time is reduced to 15MPa(a), the temperature is reduced to 480℃, and the flow rate is m1 t / h; the main steam continues to expand and do work, and when the outer shell flow steam 31 flows through the fourth flow channel 6, the steam pressure at this time is reduced to 13MPa(a), and the flow rate is m2 t / h; because the second flow channel 7 is connected with the sealing ring chamber upstream of the steam flow expansion channel through the first flow channel 5, and the fourth flow channel 6 is connected with the sealing ring chamber upstream of the steam flow expansion channel, the pressure of the steam in the second flow channel 7 is higher than the pressure of the steam in the fourth flow channel 6, so the main steam will be divided into a part from the second flow channel 7→first flow channel 5→sealing ring→fourth flow channel 6 due to the pressure difference, and when the main steam flows from the first flow channel 5 to the sealing ring, it will be divided into two paths, one of which is the steam 33 leaking downstream from the first flow channel into the fourth flow channel 6 through the second gear sealing ring (the flow rate is m4 t / h), one way is the first flow channel upstream leakage steam 34 enters the third flow channel 10 through the third gear sealing ring (flow rate is m5 t / h), so the first flow channel downstream leakage steam 33 merges with the internal leakage main steam 32 and enters the fourth flow channel 6 together, and then gathers into the downstream steam flow expansion channel to continue to do work. Because the temperature of the internal leakage main steam 32 is 600℃, the temperature of the steam at the fourth flow channel 6 rises to 520℃. After the main steam expands and does work, it enters the third flow channel 10. At this time, the pressure of the main steam drops to 5.5MPa(a) and the temperature drops to 400℃.

[0058] Therefore, each steam flow satisfies m1=m4+m5, m2=m3+m4. The original single shell needs to bear the temperature difference and pressure difference of the steam between the main steam and the third flow channel 10. The temperature difference is 200°C (600°C-400°C=200°C), and the pressure difference is 22.5MPa (28-5.5=22.5MPa). After adopting the cooling channel structure in the three-layer shell steam turbine, the inner shell 3 needs to bear the temperature difference and pressure difference between the main steam and the steam in the first flow channel 5, the temperature difference is 120℃ (600℃-480℃=120℃), and the pressure difference is 13MPa (28-15=13MPa), and the outer inner shell 2 needs to bear the temperature difference and pressure difference between the steam in the first flow channel 5 and the steam in the third flow channel 10, the temperature difference is 80℃ (480℃-400℃=80℃), and the pressure difference is 9.5MPa (15-5.5=9.5MPa). After adopting the cooling channel structure in the three-layer shell steam turbine, the temperature difference and pressure difference borne by the inner shell 3 are smaller than the temperature difference and pressure difference borne by the single shell, which can ensure that the inner shell 3 bears a smaller mechanical load and thermal stress load in the service state, and is conducive to the evaluation requirements of the center face sealing performance in the long-term steady-state operation state. In addition, for the transformation of high and medium pressure casings, especially the parameter upgrading of units, the above solution can ensure to the greatest extent that the service environment of the reused casing remains consistent with that before the transformation, thereby ensuring that the structural strength performance and life loss of the reused equipment are controllable.

[0059] The cooling channel structure in the three-layer shell steam turbine according to the present invention provides the following four typical structures according to whether there is a supplementary steam channel 41 and whether there is a fourth channel rectifying cavity 51:

[0060] 1. Cooling channel structure in a three-layer steam turbine with supplementary steam channel 41

[0061] like Figure 1As shown, when the main steam is introduced into the steam inlet chamber 8, the main steam expands and works downstream of the steam flow expansion channel (the flow direction of the main steam), and moves upstream of the steam flow expansion channel (i.e., the internal leakage main steam 32, the internal leakage main steam 32 passes through the first gear sealing ring and enters the fourth flow channel 6, the amount is small). After the main steam flows through the second flow channel 7 and the fourth flow channel 6, due to the natural pressure difference between the second flow channel 7 and the fourth flow channel 6, a part of the main steam will enter the second flow channel 7 → the first flow channel 5 → the sealing ring → the fourth flow channel 6 → the connecting cavity 9 → the steam flow expansion channel. In the process of the first flow channel 5 → the sealing ring → the fourth flow channel 6, the steam of the first flow channel 5 is divided into two paths in the sealing ring, one is the first flow channel downstream leakage steam 33 merges with the internal leakage main steam 32 and enters the fourth flow channel 6, and the other is the first flow channel upstream leakage steam 34 enters the third flow channel 10. The main steam expands and performs work along the steam flow expansion channel and enters the third flow channel 10 at the downstream end. According to actual conditions, the main steam is discharged to the next stage group or returned to the steam generator for reheating and pressurization.

[0062] The operator can also add new high-temperature, high-pressure, and high-enthalpy steam into the supplementary steam flow channel 41 through the supplementary steam pipeline device 40, so that the steam vertically merges with the main steam through the connecting cavity 9 and enters the steam flow expansion channel to continue to do work.

[0063] 2. Cooling channel structure in a three-layer steam turbine without supplementary steam channel 41

[0064] like Figure 2 As shown, when the main steam is introduced into the steam inlet chamber 8, the main steam expands and works downstream of the steam flow expansion channel (the flow direction of the main steam), and moves upstream of the steam flow expansion channel (i.e., the internal leakage main steam 32, the internal leakage main steam 32 passes through the first gear sealing ring and enters the fourth flow channel 6, the amount is small). After the main steam flows through the second flow channel 7 and the fourth flow channel 6, due to the natural pressure difference between the second flow channel 7 and the fourth flow channel 6, a part of the main steam will enter the second flow channel 7 → the first flow channel 5 → the sealing ring → the fourth flow channel 6 → the connecting cavity 9 → the steam flow expansion channel. In the process of the first flow channel 5 → the sealing ring → the fourth flow channel 6, the first flow channel 5 is divided into two paths in the sealing ring, one is the first flow channel downstream leakage steam 33 merges with the internal leakage main steam 32 and enters the fourth flow channel 6, and the other is the first flow channel upstream leakage steam 34 enters the third flow channel 10. The main steam expands and performs work along the steam flow expansion channel and enters the third flow channel 10 at the downstream end. According to actual conditions, the main steam is discharged to the next stage group or returned to the steam generator for reheating and pressurization.

[0065] 3. Cooling channel structure in a three-layer steam turbine with a supplementary steam channel 41 and a fourth channel rectifying cavity 51

[0066] like Figure 3 As shown, when the main steam is introduced into the steam inlet chamber 8, the main steam expands and performs work in the downstream of the steam flow expansion channel (the flow direction of the main steam), and moves in the upstream of the steam flow expansion channel (i.e., the internal leakage main steam 32 passes through the first gear sealing ring and enters the fourth flow channel 6, and the amount is small). After the main steam flows through the second flow channel 7 and the fourth flow channel 6, due to the natural pressure difference between the second flow channel 7 and the fourth flow channel 6, a part of the main steam in the second flow channel 7 will enter the second flow channel 7 → the first flow channel 5 → the sealing ring → the fourth flow channel 6 → the fourth flow channel rectifying chamber 51 → the steam flow expansion channel.

[0067] In the process of the first flow channel 5→seal ring→fourth flow channel 6, the first flow channel 5 is divided into two paths in the seal ring, one path is the first flow channel downstream leakage steam 33 merges with the internal leakage main steam 32 into the fourth flow channel 6, and the other path is the first flow channel upstream leakage steam 34 into the third flow channel 10. The main steam expands and works along the steam flow expansion channel and enters the third flow channel 10 at the downstream end. According to the actual situation, the main steam is discharged to the next stage group or returned to the steam generator for reheating and pressurization.

[0068] The operator can also add new high-temperature, high-pressure, and high-enthalpy steam to the supplementary steam flow channel 41 through the supplementary steam pipeline device 40, so that the steam passes through the connecting chamber 9 and vertically merges with the main steam, and enters the steam flow expansion channel to continue to do work. At this time, the fourth flow channel rectifying chamber 51 allows the steam in the fourth flow channel 6 and the supplementary steam in the connecting chamber 9 to merge into the main steam at a certain angle and shape, so as to minimize the disturbance of the main steam in the steam flow expansion channel or the additional unbalanced steam force on the rotor 4.

[0069] 4. Cooling channel structure in a three-layer steam turbine without supplementary steam channel 41 and having fourth channel rectifying cavity 51

[0070] like Figure 4 As shown, when the main steam is introduced into the steam inlet chamber 8, the main steam expands and performs work in the downstream of the steam flow expansion channel (the flow direction of the main steam), and moves in the upstream of the steam flow expansion channel (i.e., the internal leakage main steam 32 passes through the first gear sealing ring and enters the fourth flow channel 6, and the amount is small). After the main steam flows through the second flow channel 7 and the fourth flow channel 6, due to the natural pressure difference between the second flow channel 7 and the fourth flow channel 6, a part of the main steam in the second flow channel 7 will enter the second flow channel 7 → the first flow channel 5 → the sealing ring → the fourth flow channel 6 → the fourth flow channel rectifying chamber 51 → the steam flow expansion channel.

[0071] In the process of the first flow channel 5→seal ring→fourth flow channel 6, the first flow channel 5 is divided into two paths in the seal ring, one path is the first flow channel downstream leakage steam 33 merges with the internal leakage main steam 32 into the fourth flow channel 6, and the other path is the first flow channel upstream leakage steam 34 into the third flow channel 10. The main steam expands and works along the steam flow expansion channel and enters the third flow channel 10 at the downstream end. According to the actual situation, the main steam is discharged to the next stage group or returned to the steam generator for reheating and pressurization.

[0072] The fourth flow channel rectifying cavity 51 allows the steam in the fourth flow channel 6 to merge into the main steam at a certain angle and shape, thereby minimizing the disturbance of the main steam in the steam flow expansion channel or the additional unbalanced steam force on the rotor 4.

[0073] To achieve the above-mentioned and other objects, the present invention further provides a steam turbine, which includes the cooling channel structure in the above-mentioned three-shell steam turbine.

[0074] The cooling channel structure in the three-layer shell steam turbine and the steam turbine according to the present invention have the following advantages:

[0075] ①. On the basis of a single-layer inner shell, the present invention arranges an outer inner shell 2 and forms a double-layer inner shell structure with the inner shell 3, so that the temperature difference and pressure difference gradient between high-temperature components can be reduced, and the thermal stress level of the high-temperature components can be reduced to the greatest extent, which has a positive effect on the safe service of the inner shell 3 that bears high-temperature and high-pressure steam parameters.

[0076] ② The connecting cavity 9 between the inner casing 3 and the outer inner casing 2 is evenly distributed in the circumferential direction, and has a good rectifying effect on the steam in the supplementary steam flow channel 41 or the steam in the fourth flow channel 6. When merging with the main steam, it can minimize the disturbance caused by the main steam or the additional unbalanced steam force on the rotor 4; the fourth flow channel rectifying cavity 51 is provided, and the outlet of the fourth flow channel rectifying cavity 51 has a certain inclination angle with the main steam, which can minimize the disturbance caused by this part of steam to the main steam or the additional unbalanced steam force on the rotor 4 when it merges. The above structure has a positive effect on the safe, stable and reliable operation of the turbine shaft system.

[0077] ③. The present invention adopts a three-shell steam turbine structure, the first flow channel 5 is arranged in the interlayer cavity of the inner shell 3 and the outer inner shell 2, the second flow channel 7 and the fourth flow channel 6 are arranged in the inner shell 3, the third flow channel 10 is arranged in the interlayer cavity of the outer inner shell 2 and the outer shell 1, and the sealing ring (balance piston) is far away from the shaft sealing area of ​​the outer shell 1, so that part of the high-quality steam leaking inside enters the downstream through the fourth flow channel 6 to continue to expand and do work, and part of the steam leaks upstream through the first flow channel 34 to the third flow channel 10, and enters the next level group to continue to expand and do work, which has a positive effect on ensuring the cylinder efficiency of the steam turbine and avoiding the leakage of high-temperature steam to the outside, and ensuring the safe operation of the unit.

[0078] ④. The present invention is provided with a plurality of sealing rings. By selecting reasonable cooling steam (first flow channel 5 (second flow channel 7)) and supplementary steam parameters (fourth flow channel 6), a plurality of sealing rings (thrust balancing pistons) with equivalent diameters can be provided to achieve self-balancing of the axial thrust of the steam on the inner casing 3 and the outer inner casing 2. This has a positive effect on reducing excessive stress concentration caused by structural discontinuity due to a large change in the diameter of the thrust balancing piston.

[0079] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0080] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A cooling channel structure in a three-layer shell steam turbine, applied to a three-layer shell steam turbine; the three-layer shell steam turbine comprises an outer shell (1), an outer inner shell (2), an inner shell (3), a steam inlet chamber (8), and a rotor (4); the outer inner shell (2) is wrapped around the outer periphery of the inner shell (3), and the outer shell (1) is wrapped around the outer periphery of the outer inner shell (2); the steam inlet chamber (8) is arranged in the inner shell (3); a steam flow expansion channel is formed between the inner shell (3), the outer inner shell (2) and the rotor (4) on one side of the steam inlet chamber (8); a plurality of sealing rings are arranged between the inner shell (3), the outer inner shell (2) and the rotor (4) on the other side; a sealing ring chamber is formed between adjacent sealing rings; characterized in that: A first flow channel (5) is provided between the inner wall surface of the outer inner shell (2) and the outer wall surface of the inner shell (3), and one end of the first flow channel (5) is connected to a sealing ring chamber; A second flow channel (7) is provided in the inner shell (3), one end of the second flow channel (7) is connected to the first flow channel (5), and the other end of the second flow channel is connected to the steam flow expansion channel; A third flow channel (10) is provided between the outer wall surface of the outer inner shell (2) and the inner wall surface of the outer shell (1), and the third flow channel (10) is connected to the steam flow expansion channel and the steam leakage outlet of a sealing ring chamber; The steam flow expansion channel connected to the second flow channel (7) and the steam flow expansion channel connected to the third flow channel (10) are sequentially arranged along the expansion direction of the steam in the steam inlet chamber (8); A fourth flow channel (6) is provided in the inner shell (3), one end of the fourth flow channel (6) is communicated with a sealing ring chamber, and the other end of the fourth flow channel (6) is communicated with a steam flow expansion channel; An axial seal is also provided between the outer inner shell (2) and the inner shell (3), and the axial seal divides the chamber between the outer inner shell (2) and the inner shell (3) into two parts, the first flow channel (5) being one part and the other part being the connecting chamber (9); a fourth flow channel rectifying chamber (51) is also provided between the fourth flow channel (6) and the connecting chamber (9), and the fourth flow channel rectifying chamber (51) is opened in the inner shell (3); a steam inlet of the fourth flow channel rectifying chamber (51) is connected to the fourth flow channel (6), a steam outlet of the fourth flow channel rectifying chamber (51) is connected to a steam outlet of the connecting chamber (9), and an angle a1 is formed between the steam outlet of the fourth flow channel rectifying chamber (51) and the steam flow expansion channel, and the range of the angle a1 is 90°≤a1<180°.

2. The cooling channel structure in the three-layer shell steam turbine according to claim 1, characterized in that: The steam flow expansion channel connected to the fourth flow channel (6) is arranged between the steam flow expansion channel connected to the second flow channel (7) and the steam flow expansion channel connected to the third flow channel (10); a sealing ring chamber connected to the fourth flow channel (6), a sealing ring chamber connected to the first flow channel (5), and a sealing ring chamber connected to the third flow channel (10) are arranged in sequence along the direction opposite to the steam expansion direction in the steam inlet chamber (8).

3. The cooling channel structure in the three-layer shell steam turbine according to claim 2 is characterized in that: The outer shell (1), the outer inner shell (2), and the inner shell (3) all comprise an upper half and a lower half, and the upper half and the lower half are fixedly connected on a mid-section plane; the outer shell (1) and the outer inner shell (2), and the outer inner shell (2) and the inner shell (3) are all circumferentially fixedly connected; the axial seal is used for axial positioning of the outer inner shell (2) and the inner shell (3) and for sealing the first flow channel (5).

4. The cooling channel structure in the three-layer shell steam turbine according to claim 3 is characterized in that: The axial seal comprises a groove circumferentially formed on the inner wall surface of the outer inner shell (2), and a boss circumferentially arranged on the outer wall surface of the inner shell (3), wherein the boss is engaged in the groove and fixed by a plurality of pins (11); the end of the connecting cavity (9) away from the axial seal is connected to the steam flow expansion channel; the end of the fourth flow channel (6) away from the sealing ring is connected to the steam flow expansion channel through the connecting cavity (9).

5. The cooling channel structure in the three-layer shell steam turbine according to claim 1, characterized in that: The cross-sectional shape of the steam outlet channel of the fourth flow channel rectifying cavity (51) is a constant cross-sectional shape, a gradually expanding cross-sectional shape, or a gradually contracting cross-sectional shape; an angle a2 is formed between the cross-sectional profile of the steam outlet channel of the fourth flow channel rectifying cavity (51) and its center line, and the range of the angle a2 is 0°≤a2<5°.

6. The cooling channel structure in a three-layer shell steam turbine according to any one of claims 4 to 5, characterized in that: The invention also comprises a supplementary steam flow passage (41), wherein the supplementary steam flow passage (41) penetrates both the outer inner shell (2) and the outer shell (1) and is connected to the connecting cavity (9); the supplementary steam flow passage (41) is not connected to the third flow passage (10); and a supplementary steam pipeline device (40) is connected to the supplementary steam flow passage (41).

7. The cooling channel structure in the three-layer shell steam turbine according to claim 1, characterized in that: A steam extraction chamber (50) is also provided in the outer inner shell (2), and the steam extraction chamber (50) is communicated with the steam flow expansion channel.

8. The cooling channel structure in the three-layer shell steam turbine according to claim 1, characterized in that: The high temperature resistance performance of the material of the inner shell (3) is not lower than the high temperature resistance performance of the material of the outer inner shell (2).

9. A steam turbine, characterized in that: The invention comprises a cooling channel structure in a three-shell steam turbine as described in any one of claims 1 to 8.

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