A method for transforming an extraction condensing reaction steam turbine into a back pressure unit

Abstract

The present invention provides a method for transforming an extraction condensing reaction steam turbine into a back pressure unit, which utilizes the original rotor to transform, replaces the regulating stage and the pressure stage, removes the original intermediate steam seal, the pressure stage after the original intermediate steam seal and the original low pressure stage; the original intermediate steam seal is changed into a guide vane holding ring type steam seal, which is used as a rear steam seal; the original low pressure stage is changed into a hanging steam seal; and the cylinder interface is changed. The extraction condensing reaction steam turbine can be transformed into a back pressure unit with satisfactory performance requirements and reliable steam seal. It has the advantages of small transformation scope, short transformation period and low transformation cost.

Description

Technical Field

[0001] The invention belongs to the technical field of steam turbines, in particular to a back-pressure transformation technology for an extraction condensing reaction steam turbine, and in particular to a method for transforming an extraction condensing reaction steam turbine into a back-pressure unit. Background Art

[0002] With the increasing requirements of national energy conservation and emission reduction, urban centralized heating and industrial steam use, it has become a trend to transform the original extraction steam turbine of power plants into back-pressure steam turbines.

[0003] The investment cost of dismantling the original extraction-condensing reaction steam turbine and replacing it with a back-pressure reaction steam turbine is huge. If the original extraction-condensing reaction steam turbine is reconstructed according to the needs, it can not only save investment costs but also shorten the construction period, which is a feasible and economical method.

[0004] The patent document with publication number CN112682115A discloses a high back pressure modification method based on an extraction condensing steam turbine, which belongs to the technical field of high back pressure modification based on an extraction condensing steam turbine, and includes the following: (1) according to the back pressure steam parameters, the rotor blades of the corresponding stages on the extraction condensing steam turbine are machined and cut to the intermediate body of the blade; (2) the partition steam seal ring is used as the rear steam seal of the back pressure modification; (3) the low pressure heater is shut down; (4) the original low pressure heater pipeline is used as the front and rear steam seal exhaust pipelines of the back pressure unit; (5) a start-stop emptying system is set up to replenish water to the front of the steam seal cooler; (6) the condenser is shut down, and the cooling water supplied to the oil cooler and the generator air cooler uses temporary cooling water. This modification plan retains the regulating stage and the pressure stage, removes the low pressure stage, and transforms the partition steam seal ring as the rear steam seal of the back pressure modification.

[0005] The patent document with publication number CN108331624A discloses a method for transforming a condensing steam turbine into a back-pressure steam turbine, wherein the condensing steam turbine comprises a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder and a condenser connected in sequence, and a rotor is provided in the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder; the method comprises the following technical measures: the rotor of the condensing steam turbine is transformed, and the part of the rotor located in the low-pressure cylinder is processed into a bare axis rotor; the partition of the low-pressure cylinder is completely removed, and the original water spray cooling device in the low-pressure cylinder is retained; a new low-pressure end steam seal ring is installed, and the low-pressure cylinder steam seal gap is adjusted; the low-pressure cylinder steam cooling system is cancelled, and the exhaust steam of the medium-pressure cylinder is completely led to the heating pipeline and connected to the heat user for heating. This transformation plan also retains the regulating stage and the pressure stage, removes the low-pressure stage, and installs a new partition as the rear steam seal.

[0006] However, the above-mentioned steam turbine back pressure modification scheme abandons the low-pressure stage and retains the original regulating stage and pressure stage. The performance parameters of the unit after modification are also fixed, and the selectivity is small. At the same time, after the steam turbine is modified into a back-pressure steam turbine, the pressure of the new back pressure chamber is increased. The high back pressure puts forward higher requirements on the air tightness of the rear steam seal. Only using the original set modification or simply blocking the airflow cannot meet the requirements. Specifically, there are two reasons why the requirements cannot be met:

[0007] 1. The original blade structure is retained and the turbine performance parameters cannot be changed.

[0008] 2. After the back pressure modification, the position of the cylinder exhaust chamber is advanced, and the exhaust position is in the middle of the cylinder. The diameter of the middle of the cylinder is large, and the length of the required circumferential seal is long. In this case, the existing technology cannot meet the requirements:

[0009] a) The sealing length of the ordinary intermediate steam seal is short, and it cannot ensure the sealing between the rotor and the steam seal after the exhaust pressure is increased. The ordinary original intermediate steam seal is not good at sealing between the circumferential direction and the cylinder, because it only serves as a partition for the airflow inside the cylinder.

[0010] b) The common long steam seal structure used in back-pressure reaction steam turbines (such as the steam seals on the front and rear ends of the cylinder) originally has a small diameter and a small circumferential seal length between the cylinder and the cylinder. However, the diameter, circumferential size, and gap between the cylinder and the required steam seal in the extraction condensing reaction steam turbine are large, and the common long steam seal structure cannot achieve reliable axial sealing and cannot meet the needs of large circumferential size (large diameter) sealing. Summary of the invention

[0011] In order to solve the above technical problems, the purpose of the present invention is to provide a method for transforming an extraction condensing reaction steam turbine into a back-pressure unit. By modifying the original rotor, replacing the regulating stage and the pressure stage, adding steam seals, and changing the use of the cylinder interface, the extraction condensing reaction steam turbine can be transformed into a back-pressure unit with satisfactory performance and reliable steam seals.

[0012] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0013] A method for transforming an extraction condensing reaction steam turbine into a back pressure unit comprises the following steps:

[0014] 1) On the premise of retaining the original regulating stage blade root groove and the original intermediate steam seal front pressure stage blade root groove position on the extraction condensing reaction steam turbine rotor, the new regulating stage, new pressure stage, guide vane ring steam seal, and suspension steam seal are redesigned and determined according to the performance parameters required by the unit;

[0015] 2) According to the design, replace and install the new regulating stage and new pressure stage at the original regulating stage and the pressure stage before the original intermediate steam seal;

[0016] Remove the original intermediate steam seal, the original pressure stage after the intermediate steam seal and the original low-pressure stage;

[0017] 3) Change the original intermediate steam seal to a guide vane holding ring type steam seal, used as the rear steam seal; change the original low-pressure stage to a hanging steam seal;

[0018] 4) Seal the original overflow hole with a flange sealing cover; change the original steam extraction hole into a back pressure exhaust interface, connected to the exhaust pipe; change the original balance hole into a steam seal cooling interface, connected to the steam seal cooler; use the original exhaust cylinder as the rear bearing seat support frame.

[0019] Preferably, in step 3), a groove is formed on the left end face of the guide vane holding ring steam seal mounting groove, and a C-ring sealing ring is provided for circumferential sealing.

[0020] Preferably, pressure and temperature measuring holes and operating holes are provided on the flange sealing cover for measuring pressure and temperature.

[0021] Preferably, in step 1), the blade root groove of the new pressure level can be expanded according to design requirements to add a new blade root groove of the new pressure level.

[0022] Preferably, the original steam extraction hole is connected to the chamber between the new pressure stage and the guide vane holding ring type steam seal for exhausting steam.

[0023] Preferably, the original balancing hole is connected to the chamber between the guide vane holding ring type steam seal and the suspension steam seal for passing cooling water.

[0024] Preferably, the guide vane holding ring type steam seal is fixed on the cylinder, and the guide vane holding ring type steam seal is sealed with the cylinder in the circumferential direction through a C-ring sealing ring at the groove of the steam seal mounting groove, and the steam seal plate on the guide vane holding ring type steam seal and the steam seal plate on the rotor form a labyrinth steam seal.

[0025] Preferably, the hanging steam seal is fixed on the cylinder, and the steam seal sheet on the hanging steam seal and the steam seal sheet on the rotor form a labyrinth steam seal.

[0026] Preferably, the guide vane holding ring type steam seal adopts a long steam seal structure whose sealing length is longer than that of the original intermediate steam seal.

[0027] Due to the adoption of the above technical scheme, the present invention retains the front and rear bearing seats, cylinders, cylinders and other large parts of the steam turbine, and can adjust the original design according to the performance parameters required by the unit. By using the original rotor modification, replacing the regulating stage and pressure stage, adding steam seals, and changing the use of the cylinder interface, the extraction condensing reaction steam turbine can be transformed into a back-pressure unit that meets the performance requirements and has reliable steam seals. It has the advantages of small modification scope, short modification period and low modification cost. Under the premise of reducing the modification scope and shortening the construction period, the scheme can re-plan and modify the unit according to the required unit performance parameters, reduce the leakage of the rear steam seal, and meet the modification requirements of the diversified performance of the steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings in the specification, which constitute a part of the present application, are used to provide a further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute a limitation on the present application.

[0029] Figure 1 It is a schematic diagram of the longitudinal section structure of the extraction condensing reaction steam turbine before transformation according to the present invention.

[0030] Figure 2 The figure is a schematic diagram of the longitudinal section structure of the back-pressure reaction steam turbine after modification according to the present invention.

[0031] Figure 3 It is a schematic diagram of the longitudinal section structure of the guide vane holding ring type steam seal of the present invention.

[0032] Figure 4 for Figure 2 A local enlarged schematic diagram of point A in the middle.

[0033] In the figure:

[0034] 1. Rotor; 1-1. Original regulating stage; 1-1a. Original regulating stage blade root groove; 1-2. Original intermediate steam seal front pressure stage; 1-2a. Original intermediate steam seal front pressure stage blade root groove; 1-3. Original intermediate steam seal; 1-4. Original intermediate steam seal rear pressure stage; 1-5. Original low-pressure stage; 2. Cylinder; 2-1. Original overflow hole; 2-2. Original steam extraction hole; 2-3. Original balance hole; 3. Original exhaust cylinder; 4-1. New regulating stage; 4-2. New pressure stage; 4-2a. New pressure stage newly added blade root groove; 4-3. Guide vane holding ring type steam seal; 4-3a. C-ring seal; 4-4. Suspension steam seal; 5. Flange sealing cover. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of the present invention, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprises" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more, unless otherwise clearly specified.

[0041] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0043] Embodiment 1:

[0044] like Figure 1 As shown, it is an extraction condensing reaction steam turbine before transformation, on which the original regulating stage 1-1, the original pressure stage 1-2 before the intermediate steam seal, the original intermediate steam seal 1-3, the original pressure stage 1-4 after the intermediate steam seal and the original low-pressure stage 1-5 are arranged in sequence, wherein the original regulating stage 1-1, the original pressure stage 1-2 before the intermediate steam seal, the original intermediate steam seal 1-3 and the original pressure stage 1-4 after the intermediate steam seal are located in the cylinder 2, the original low-pressure stage 1-5 is located in the original exhaust cylinder 3, and the cylinder 2 is provided with the original overflow hole 2-1, the original extraction hole 2-2 and the original balance hole 2-3.

[0045] A method for transforming an extraction condensing reaction steam turbine into a back pressure unit comprises the following steps:

[0046] 1) If Figure 1 As shown, under the premise of retaining the positions of the original regulating stage blade root groove 1-1a and the original intermediate steam seal front pressure stage blade root groove 1-2a on the extraction condensing reaction steam turbine rotor 1, according to the performance parameters required by the unit, the following are redesigned and determined: new regulating stage 4-1, new pressure stage 4-2, guide vane holding ring type steam seal 4-3, and hanging steam seal 4-4; among which, the blade root groove of the new pressure stage 4-2 can be expanded according to the design needs, and the new pressure stage has a newly added blade root groove 4-2a.

[0047] 2) If Figure 2 As shown, according to the design, the new regulating stage 4-1 and the new pressure stage 4-2 are replaced and installed at the positions of the original regulating stage 1-1 and the original pressure stage 1-2 before the intermediate steam seal; the original intermediate steam seal 1-3, the original pressure stage 1-4 after the intermediate steam seal and the original low-pressure stage 1-5 are removed.

[0048] 3) If Figure 2 As shown, the original intermediate steam seal 1-3 is changed into a guide vane holding ring type steam seal 4-3, which is used as a rear steam seal. The longitudinal section structure diagram of the guide vane holding ring type steam seal 4-3 is as shown in Figure 3 As shown; the left end face of the guide vane holding ring type steam seal 4-3 installation groove is grooved and provided with a C-ring seal 4-3a for circumferential sealing. The structure of the C-ring seal is as shown Figure 4 As shown; the original low-pressure stage 1-5 is changed to a suspended steam seal 4-4.

[0049] 4) The original overflow hole 2-1 is sealed with a flange sealing cover 5, and pressure and temperature measuring holes and operation holes can be opened on the flange sealing cover 5 for pressure and temperature measurement and other operations.

[0050] 5) Change the original steam extraction hole 2-2 into a back pressure exhaust interface and connect it to the exhaust pipe.

[0051] 6) Change the original balance hole 2-3 into a steam seal cooling interface and connect it to the steam seal cooler.

[0052] 7) Use the original row cylinder 3 as the rear bearing seat support frame.

[0053] like Figure 2 As shown in the figure, it is a back-pressure reaction steam turbine after the transformation of the present invention. A new regulating stage 4-1, a new pressure stage 4-2, a guide vane ring-type steam seal 4-3 and a hanging steam seal 4-4 are sequentially sleeved on the turbine rotor 1. The guide vane ring-type steam seal 4-3 is located at the original intermediate steam seal 1-3 position, and the hanging steam seal 4-4 is located at the original low-pressure stage 1-5 position; the new regulating stage 4-1, the new pressure stage 4-2 and the guide vane ring-type steam seal 4-3 are installed in the cylinder 2, and the hanging steam seal 4-4 seals the steam. The right end of cylinder 2; the original discharge cylinder 3 is used as the rear bearing seat support frame; the original overflow hole 2-1 is sealed with a flange sealing cover 5; the original steam extraction hole 2-2 is connected to the chamber between the new pressure stage 4-2 and the guide vane holding ring type steam seal 4-3, and the original steam extraction hole 2-2 is changed to a back pressure steam exhaust interface, connected to the exhaust pipe; the original balance hole 2-3 is connected to the chamber between the guide vane holding ring type steam seal 4-3 and the suspension steam seal 4-4, and the original balance hole 2-3 is changed to a steam seal cooling interface, connected to the steam seal cooler, and passed cooling water.

[0054] In this embodiment, the guide vane holding ring type steam seal 4-3 is preferably fixed on the cylinder 2, and the guide vane holding ring type steam seal 4-3 is sealed with the cylinder in the circumferential direction through the C-shaped ring seal 4-3a at the groove of the steam seal installation groove. The steam seal sheet on the guide vane holding ring type steam seal 4-3 and the steam seal sheet on the rotor form a labyrinth steam seal (a conventional sealing form with a gap, and the rotor can rotate without hindrance), forming a seal between the steam seal and the rotor.

[0055] Further preferably, the length of the guide vane holding ring type steam seal 4-3 is longer than the length of the original intermediate steam seal 1-3.

[0056] In this embodiment, the suspension steam seal 4-4 is preferably fixed on the cylinder 2. The sealing between the suspension steam seal 4-4 and the rotor and the cylinder is similar to the guide vane holding ring type steam seal 4-3, except that: the structure lacks a C-ring seal. This is because most of the steam turbine exhaust is directed to the back pressure exhaust interface (the original steam extraction hole 2-2), and only part of the chamber behind the guide vane holding ring steam seal leaks through the seal pieces of the guide vane holding ring steam seal, and the pressure is also relatively low. Therefore, the suspension steam seal only needs to be installed on the positioning ring in the cylinder. The seal pieces on the suspension steam seal and the seal pieces on the rotor form a labyrinth steam seal (a conventional sealing form with a gap, so that the rotor can rotate without hindrance), forming a seal between the steam seal and the rotor.

[0057] For example, the existing steam turbine back pressure transformation schemes disclosed in patent documents such as CN112682115A and CN108331624A are all suitable for impulse steam turbines. The low-pressure stage is abandoned, and the original regulating stage and pressure stage blade root groove of the rotor are retained. The blade selection is limited, so the transformation is limited by the original unit parameters and size, and has certain limitations. At the same time, after the steam turbine is transformed into a back-pressure steam turbine, the pressure of the new back-pressure chamber is increased. The high back pressure puts forward higher requirements on the air tightness of the rear steam seal. The sealing performance of the self-sealing steam seal transformed by the original sleeve is not ideal when the back pressure is not established when the machine is started.

[0058] Specifically, the existing transformation plan cannot meet the requirements for the following two reasons:

[0059] 1. The original blade structure is retained and the turbine performance parameters cannot be changed.

[0060] 2. After the back pressure modification, the position of the cylinder exhaust chamber is advanced, and the exhaust position is in the middle of the cylinder. The diameter of the middle of the cylinder is large, and the length of the required circumferential seal is long. In this case, the existing technology cannot meet the requirements:

[0061] a) The sealing length of the ordinary intermediate steam seal is short, and it cannot ensure the sealing between the rotor and the steam seal after the exhaust pressure is increased. The ordinary original intermediate steam seal is not good at sealing between the circumferential direction and the cylinder, because it only serves as a partition for the airflow inside the cylinder.

[0062] b) The common long steam seal structure used in back-pressure reaction steam turbines (such as the steam seals on the front and rear ends of the cylinder) originally has a small diameter and a small circumferential seal length between the cylinder and the cylinder. However, the diameter, circumferential size, and gap between the cylinder and the required steam seal in the extraction condensing reaction steam turbine are large, and the common long steam seal structure cannot achieve reliable axial sealing and cannot meet the needs of large circumferential size (large diameter) sealing.

[0063] In the present invention, for the reaction steam turbine, the regulating stage and the pressure stage are also included in the scope of the modification design, and the regulating stage and the pressure stage are replaced, and the pressure stage blades are added or reduced, so as to expand the performance range that can be selected for the unit modification design. Through the guide vane holding ring type steam seal with a C-ring seal, the C-ring seal is used in the circumferential direction, and the long steam seal in the guide vane holding ring type steam seal is used in the axial direction to achieve reliable sealing of the steam seal after the back pressure modification. The original exhaust port is changed to back pressure exhaust, and the original exhaust cylinder is used as the rear bearing seat support frame, and the original layout is kept unchanged.

[0064] Moreover, under the condition of keeping the original blade root slot position, the turbine can be redesigned according to user needs, and the blades can be replaced, added or reduced to achieve changes in turbine parameters and meet user needs. The cylinder contains a positioning ring for the guide vane holding ring and the intermediate steam seal to install, and the guide vane holding ring steam seal is easy to replace; at the same time, it has the advantage of a long sealing length, which can achieve reliable sealing in the rotor axial direction; the C-ring seal ring at the guide vane holding ring slot is used to achieve a large circumferential size seal, which is highly innovative compared to existing technologies.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "an implementation", "specific implementation", "other implementations", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment, implementation or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described above may also be combined in a suitable manner in any one or more embodiments, implementations or examples. The technical solutions recorded in the present invention also include technical solutions formed by any one or more of the specific features, structures, materials or characteristics described above in a separate or combined manner.

[0066] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Ordinary technicians in the field can change, modify, replace, modify, delete some features, add features or re-combine features to form a technical solution in the above embodiments without departing from the principles and purpose of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the innovative principles of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for transforming an extraction condensing reaction steam turbine into a back pressure unit, characterized in that: The following steps are involved: 1) Under the premise of retaining the original regulating stage blade root groove and the original intermediate steam seal front pressure stage blade root groove position on the extraction condensing reaction steam turbine rotor, the new regulating stage, new pressure stage, guide vane ring type steam seal, and suspension steam seal are redesigned and determined according to the performance parameters required by the unit; 2) According to the design, replace and install the new regulating stage and new pressure stage at the original regulating stage and the pressure stage before the intermediate steam seal; Remove the original intermediate steam seal, the original pressure stage after the intermediate steam seal and the original low-pressure stage; 3) Change the original intermediate steam seal to a guide vane holding ring type steam seal and use it as the rear steam seal; The original low-pressure stage is changed to a hanging steam seal; the left end face of the guide vane holding ring type steam seal installation groove is grooved, and a C-ring seal is provided for circumferential sealing; the guide vane holding ring type steam seal is fixed on the cylinder, and the guide vane holding ring type steam seal is sealed with the cylinder in the circumferential direction through the C-ring seal at the groove of the steam seal installation groove, and the steam seal sheet on the guide vane holding ring type steam seal and the steam seal sheet on the rotor form a labyrinth steam seal; the guide vane holding ring type steam seal adopts a long steam seal structure with a sealing length longer than the original intermediate steam seal; the hanging steam seal is fixed on the cylinder, and the steam seal sheet on the hanging steam seal and the steam seal sheet on the rotor form a labyrinth steam seal; 4) Seal the original overflow hole with a flange sealing cover; change the original steam extraction hole into a back pressure exhaust interface and connect it to the exhaust pipe; change the original balance hole into a steam seal cooling interface and connect it to the steam seal cooler; use the original exhaust cylinder as the rear bearing seat support frame; the original steam extraction hole connects the chamber between the new pressure stage and the guide vane holding ring type steam seal for exhaust; the original balance hole connects the chamber between the guide vane holding ring type steam seal and the suspension steam seal for cooling water.

2. The method for transforming an extraction condensing reaction steam turbine into a back pressure unit according to claim 1, characterized in that: Pressure and temperature measuring holes and operating holes are opened on the flange sealing cover for measuring pressure and temperature.

3. The method for transforming an extraction condensing reaction steam turbine into a back pressure unit according to claim 1, characterized in that: In the step 1), the blade root groove of the new pressure level can be expanded according to the design requirements to add a new blade root groove of the new pressure level.

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