A high-parameter steam turbine deep peak shaving high-pressure front shaft seal structure and cooling method

Abstract

The present invention discloses a high-parameter steam turbine deep peak shaving high-pressure front shaft seal structure and cooling method, belonging to the technical field of steam turbine thermal power generation; the main feature of this structure is that a steam seal ring is further provided at the end of the inner cylinder section of the high-pressure front shaft seal close to the outer cylinder section of the high-pressure front shaft seal, a steam leakage interface is arranged inside the steam seal ring, the steam leakage interface is led out through a bypass pipeline, and a stop valve is arranged on the bypass pipeline; different from the traditional structural design, in the design of this structure, a steam leakage structure is adopted, and the steam leakage is led out through a bypass pipeline. Under the condition of deep peak shaving of a high-parameter steam turbine, the direction of the steam leakage can be effectively adjusted, and the contact between the steam leakage and the high-pressure outer cylinder can be controlled according to the temperature condition, so as to effectively avoid irreversible damage to the high-pressure outer cylinder caused by excessive temperature, and further improve the service life of the high-pressure outer cylinder.

Description

Technical Field

[0001] The present invention relates to a high-parameter steam turbine deep peak shaving high-pressure front shaft seal structure and cooling method, belonging to the technical field of steam turbine thermal power generation. Background Art

[0002] With the accelerating advancement of the "dual carbon" goal, energy transformation is inevitable. The proportion of green energy in the energy consumption market is increasing day by day, which poses higher requirements for the economy and deep peak shaving technology of traditional coal-fired power units. One of the most effective ways to improve the power generation efficiency of coal-fired power units is to increase the inlet steam parameters of the units. With the development of thermal power technology, the inlet steam parameters of coal-fired power units are getting higher and higher, and the leakage steam temperature of the front shaft seal of the high-pressure cylinder (including the ultra-high-pressure cylinder of the secondary reheat unit) is also getting higher and higher. Especially under the deep peak shaving condition, due to the significant decrease in the pressure of the unit's sliding pressure operation while the inlet steam temperature decreases little, the leakage steam temperature of the high-pressure front shaft seal rises sharply, resulting in the rise of the leakage steam temperature of the front shaft seal of the high-pressure inner cylinder, which has a greater impact on the operation of the high-pressure outer cylinder. If the material grade is upgraded with the increase in temperature, the manufacturing cost of the high-pressure outer cylinder will increase significantly.

[0003] Currently, the high-pressure module of coal-fired power units (the ultra-high-pressure module of secondary reheat units) generally adopts a double-cylinder design. The leakage steam from the front shaft seal of the high-pressure inner cylinder enters the interlayer between the high-pressure inner and outer cylinders, and the pressure of this interlayer is established by the exhaust steam of the high-pressure cylinder. The high-pressure inner cylinder is made of high-alloy cast steel, and the high-pressure outer cylinder is made of conventional alloy cast steel with a relatively low temperature adaptation grade (generally Cr-Mo-V steel, with an upper operating temperature limit of about 570°C). If the unit design parameters are increased to above 35 Mpa / 630°C, when the unit is operating at sliding pressure and the load is reduced to less than about 60%-70% THA due to peak shaving requirements, the leakage steam temperature of the high-pressure front shaft seal will exceed 570°C, which exceeds the temperature adaptation range of the high-pressure outer cylinder material. Summary of the Invention

[0004] The invention objective of the present invention is to provide a high-parameter steam turbine deep peak shaving high-pressure front shaft seal structure and cooling method to improve the operation reliability and service life of high-temperature components such as the high-pressure outer cylinder and ultra-high-pressure outer cylinder of the steam turbine in view of the above problems.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A high-parameter steam turbine deep peak shaving high-pressure front shaft seal cooling method includes the following steps:

[0007] S1. A leakage steam interface is arranged inside the end steam seal ring of the high-pressure front shaft seal inner cylinder section, and the leakage steam is led out through a bypass pipeline to the hot reheat section or a regenerative extraction steam pipeline matching the leakage steam temperature, and a stop valve is arranged on the external pipeline where the leakage steam is led out;

[0008] S2. When the steam turbine operates under rated conditions, the stop valve is closed. The steam leakage from the inner cylinder section of the high-pressure front shaft seal directly leaks into the interlayer formed by the high-pressure outer cylinder and the high-pressure inner cylinder, then leaks into the outer cylinder section of the high-pressure front shaft seal, and finally enters the shaft seal header. At this time, the temperature of the steam leakage from the inner cylinder section of the high-pressure front shaft seal is relatively low, and the material properties of the high-pressure outer cylinder can meet the requirements of the steam leakage temperature.

[0009] S3. When the unit operates in deep peak shaving, the unit load decreases and the high-pressure steam inlet chamber pressure drops. Using the parameters of the high-pressure steam inlet chamber and the pressure of the interlayer between the high-pressure inner and outer cylinders, the outlet temperature of the outermost steam seal is calculated according to the equal enthalpy temperature drop; further judge whether the outlet temperature is higher than the allowable temperature of the high-pressure outer cylinder material.

[0010] Furthermore, in step S3, when the outlet temperature is higher than the allowable temperature of the high-pressure outer cylinder material, the stop valve is opened to divert the shaft seal steam leakage to the reheat hot section or the regenerative extraction steam pipeline matching the steam leakage temperature.

[0011] Furthermore, in step S3, during the process of the unit sliding parameter load increase, when the outlet temperature is lower than the allowable temperature of the high-pressure outer cylinder material, the stop valve is closed, and the steam leakage from the inner cylinder section of the high-pressure front shaft seal directly leaks into the interlayer formed by the high-pressure outer cylinder and the high-pressure inner cylinder.

[0012] Furthermore, the allowable temperature of the material of the high-pressure outer cylinder does not exceed 570 °C.

[0013] Furthermore, in step S3, the equal enthalpy temperature drop is calculated using the high-pressure steam inlet pressure, temperature and high-pressure exhaust pressure, and the steam leakage temperature value of the front shaft seal is obtained and applied to the control logic to guide the action of the stop valve.

[0014] Furthermore, to avoid the frequent action of the stop valve at the opening and closing critical points, a time-delay action logic for the stop valve is set.

[0015] Furthermore, the steam turbine is a unit with an inlet steam parameter not less than 35 Mpa / 630 °C or a unit with a steam leakage temperature of the high-pressure front shaft seal higher than the allowable value of the high-pressure outer cylinder material in the full load operation range.

[0016] Furthermore, the steam turbine is a single reheat unit or a double reheat unit.

[0017] A front shaft seal structure for a high-pressure cylinder, which is applied to the above-mentioned deep peak shaving high-pressure front shaft seal cooling method for a high-parameter steam turbine, includes a high-pressure outer cylinder, a high-pressure inner cylinder, and a high-pressure rotor arranged inside the high-pressure inner cylinder. A high-pressure inner-outer cylinder interlayer is formed between the high-pressure outer cylinder and the high-pressure inner cylinder. The high-pressure inner cylinder and the high-pressure rotor are hermetically assembled through a high-pressure front shaft seal inner cylinder section. The high-pressure outer cylinder and the high-pressure rotor are hermetically assembled through a high-pressure front shaft seal outer cylinder section. A steam seal ring is further arranged at the end of the high-pressure front shaft seal inner cylinder section close to the high-pressure front shaft seal outer cylinder section. A steam leakage interface is arranged inside the steam seal ring. The steam leakage interface is led out through a bypass pipeline, and a stop valve is arranged on the bypass pipeline.

[0018] Further, the bypass pipeline is connected to the reheater hot section or a regenerative extraction steam pipeline matching the steam leakage temperature.

[0019] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0020] The high-parameter steam turbine deep peak shaving high-pressure front shaft seal structure and cooling method of the present invention are different from the traditional structure design. In the design of this structure, a steam leakage structure is adopted, and the steam leakage is led out through a bypass pipeline. Under the condition of deep peak shaving of a high-parameter steam turbine, the direction of the steam leakage can be effectively adjusted, and the contact between the steam leakage and the high-pressure outer cylinder can be controlled according to the temperature condition, so as to effectively avoid irreversible damage to the high-pressure outer cylinder caused by excessive temperature, and further improve the service life of the high-pressure outer cylinder. Brief Description of the Drawings

[0021] The present invention will be described by way of examples with reference to the accompanying drawings, where:

[0022] Figure 1 is a schematic structural diagram of the present invention.

[0023] Reference numerals in the figure: 1 - high-pressure outer cylinder, 2 - high-pressure inner cylinder, 3 - high-pressure rotor, 4 - high-pressure front shaft seal inner cylinder section, 5 - steam seal ring, 6 - high-pressure front shaft seal outer cylinder section, 7 - stop valve, T1 - inlet steam temperature, T2 - outlet temperature, P1 - inlet steam pressure, P2 - high-pressure inner-outer cylinder interlayer pressure. Detailed Embodiments

[0024] All the features disclosed in this specification, or all the steps in any method or process disclosed, except for mutually exclusive features and / or steps, can be combined in any way.

[0025] Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features. That is, unless specifically described, each feature is only an example in a series of equivalent or similar features.

[0026] Embodiment 1

[0027] A method for deep peak shaving of the high-pressure front shaft seal cooling of a high-parameter steam turbine is as follows Figure 1 shown, including the following steps:

[0028] S1. A steam leakage interface is arranged inside the steam seal ring 5 at the end of the high-pressure front shaft seal inner cylinder section 4, and the steam leakage is led out through a bypass pipeline to the reheater hot section or the regenerative extraction steam pipeline matching the steam leakage temperature, and a stop valve 7 is arranged on the external pipeline where the steam leakage is led out;

[0029] S2. When the steam turbine operates under the rated condition, the stop valve 7 is closed, and the steam leakage of the high-pressure front shaft seal inner cylinder section 4 directly leaks into the interlayer composed of the high-pressure outer cylinder 1 and the high-pressure inner cylinder 2, and then leaks into the high-pressure front shaft seal outer cylinder section 6 and finally enters the shaft seal main pipe; at this time, the steam leakage temperature of the high-pressure front shaft seal inner cylinder section 4 is relatively low, and the material performance of the high-pressure outer cylinder 1 can meet the requirements of the steam leakage temperature;

[0030] S3. When the unit operates in deep peak shaving, the unit load drops, the high-pressure steam inlet chamber pressure decreases, and the outlet temperature T2 of the outermost steam seal is calculated according to the equal enthalpy temperature drop by using the high-pressure steam inlet chamber parameters (the steam inlet pressure P1 and the steam inlet temperature T1 inside the high-pressure steam inlet) and the high-pressure inner and outer cylinder interlayer pressure P2; further judge whether the outlet temperature T2 is higher than the allowable temperature of the material of the high-pressure outer cylinder 1.

[0031] In this embodiment, as a special explanation, different from the traditional structural design, in this design, a steam leakage interface is arranged inside the steam seal ring 5 at the end of the high-pressure front shaft seal inner cylinder section 4, that is, there is a steam seal ring 5 at the end of the high-pressure front shaft seal inner cylinder section 4, and a steam leakage interface is arranged inside the steam seal ring 5 close to the high-pressure front shaft seal inner cylinder section 4. When the steam leakage temperature is too high, that is, higher than the available temperature of the material of the high-pressure outer cylinder 1, the stop valve 7 is opened, and the internal pressure of the bypass pipeline is smaller than the role of the sealing ring, and the steam leakage will be directly led out through the bypass pipeline, thus effectively solving the problem of damage to the high-pressure outer cylinder 1 caused by too high steam leakage temperature, and further meeting the current use requirements of high-parameter steam turbines, and further controlling the production cost of the high-pressure outer cylinder 1.

[0032] On the basis of the above specific design, for further optimized design, in step S3, when the outlet temperature T2 is higher than the allowable temperature of the material of the high-pressure outer cylinder 1, the stop valve 7 is opened to lead the shaft seal steam leakage to the reheater hot section or the regenerative extraction steam pipeline matching the steam leakage temperature.

[0033] Similarly, as a further step, in step S3, during the process of increasing the load with sliding parameters of the unit, when the outlet temperature T2 is lower than the allowable temperature of the material of the high-pressure outer cylinder 1, the stop valve 7 is closed, and the steam leakage from the inner cylinder section 4 of the high-pressure front shaft seal directly leaks into the interlayer formed by the high-pressure outer cylinder 1 and the high-pressure inner cylinder 2.

[0034] Based on the above specific design basis, for further optimization, the allowable temperature of the material of the high-pressure outer cylinder 1 does not exceed 570 °C. In this design, it is mainly considered that the material of the high-pressure outer cylinder 1 adopts conventional alloy cast steel (generally Cr-Mo-V steel, with an upper operating temperature limit of about 570 °C).

[0035] On the basis of the above specific design, more specifically, in step S3, the isenthalpic temperature drop is calculated using the high-pressure inlet steam pressure P1, temperature, and high-pressure exhaust steam pressure, and the steam leakage temperature value of the front shaft seal is obtained and applied to the control logic to guide the operation of the stop valve 7.

[0036] Furthermore, to avoid the frequent operation of the stop valve 7 at the opening and closing critical points, a time-delay operation logic for the stop valve 7 is set.

[0037] Based on the above specific design, more specifically, the steam turbine is a unit with an inlet steam parameter of not less than 35 Mpa / 630 °C or a unit in which the steam leakage temperature of the high-pressure front shaft seal in the full load operation range is higher than the allowable temperature of the material of the high-pressure outer cylinder 1. As a high-parameter steam turbine, its inlet steam parameter is not less than 35 Mpa / 630 °C.

[0038] As a more specific design, the steam turbine is a single reheat unit or a double reheat unit.

[0039] Embodiment 2

[0040] On the basis of the design of Embodiment 1, as a specific structural design, a high-pressure cylinder front shaft seal structure, as Figure 1 shown, includes a high-pressure outer cylinder 1, a high-pressure inner cylinder 2, and a high-pressure rotor 3 disposed within the high-pressure inner cylinder 2. A high-pressure inner and outer cylinder interlayer is formed between the high-pressure outer cylinder 1 and the high-pressure inner cylinder 2. The high-pressure inner cylinder 2 and the high-pressure rotor 3 are hermetically assembled through a high-pressure front shaft seal inner cylinder section 4. The high-pressure outer cylinder 1 and the high-pressure rotor 3 are hermetically assembled through a high-pressure front shaft seal outer cylinder section 6. A steam seal ring 5 is further provided at the end of the high-pressure front shaft seal inner cylinder section 4 close to the high-pressure front shaft seal outer cylinder section 6. A steam leakage interface is provided inside the steam seal ring 5. The steam leakage interface is led out through a bypass pipeline, and a stop valve 7 is provided on the bypass pipeline.

[0041] In a more specific design, the bypass pipeline is connected to the reheated hot section or a regenerative extraction steam pipeline matching the steam leakage temperature.

[0042] In summary, for the high-parameter steam turbine deep peak shaving high-pressure front shaft seal structure and cooling method of the present invention, different from the traditional structure design, a steam leakage structure is adopted in the design of this structure, and the leaked steam is led out through a bypass pipeline. Under the condition of deep peak shaving of a high-parameter steam turbine, the direction of the leaked steam can be effectively adjusted, and the contact between the leaked steam and the high-pressure outer cylinder can be controlled according to the temperature situation, so as to effectively avoid irreversible damage to the high-pressure outer cylinder caused by excessive temperature, and further improve the service life of the high-pressure outer cylinder.

[0043] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new combination of the steps of any new method or process disclosed.

Claims

1. A method for cooling the high-pressure front shaft seal during deep peak shaving of a high-parameter steam turbine, characterized in that: It includes the following steps: S1. A steam leakage interface is provided inside the steam seal ring at the end of the inner cylinder section of the high-pressure front shaft seal, and the steam leakage is led out through a bypass pipeline to the reheater hot section or a regenerative extraction steam pipeline matching the steam leakage temperature, and a stop valve is provided on the external pipeline where the steam leakage is led out; S2. When the steam turbine operates under rated conditions, the stop valve is closed, and the steam leakage from the inner cylinder section of the high-pressure front shaft seal directly leaks into the interlayer formed by the high-pressure outer cylinder and the high-pressure inner cylinder, and then leaks into the outer cylinder section of the high-pressure front shaft seal and finally enters the shaft seal main pipe; at this time, the steam leakage temperature of the inner cylinder section of the high-pressure front shaft seal is relatively low, and the material performance of the high-pressure outer cylinder can meet the requirements of the steam leakage temperature; S3. When the unit operates in deep peak shaving, the unit load decreases and the high-pressure steam inlet chamber pressure decreases. Using the parameters of the high-pressure steam inlet chamber and the pressure of the interlayer between the high-pressure inner and outer cylinders, the outlet temperature of the outermost steam seal is calculated according to the equal enthalpy temperature drop; further judge whether the outlet temperature is higher than the allowable temperature of the high-pressure outer cylinder material; when the outlet temperature is higher than the allowable temperature of the high-pressure outer cylinder material, open the stop valve to lead the shaft seal steam leakage to the reheater hot section or a regenerative extraction steam pipeline matching the steam leakage temperature; during the process of the unit's sliding parameter load increase, when the outlet temperature is lower than the allowable temperature of the high-pressure outer cylinder material, close the stop valve, and the steam leakage from the inner cylinder section of the high-pressure front shaft seal directly leaks into the interlayer formed by the high-pressure outer cylinder and the high-pressure inner cylinder; the allowable temperature of the material of the high-pressure outer cylinder does not exceed 570 °C; calculate the equal enthalpy temperature drop using the high-pressure steam inlet pressure, temperature and high-pressure exhaust pressure, obtain the value of the front shaft seal steam leakage temperature and apply it to the control logic to guide the action of the stop valve.

2. A method for cooling the high-pressure front shaft seal during deep peak shaving of a high-parameter steam turbine according to claim 1, characterized in that: To avoid frequent actions of the stop valve at the opening and closing critical points, a delay action logic for the stop valve is set.

3. A method for cooling the high-pressure front shaft seal during deep peak shaving of a high-parameter steam turbine according to claim 1, characterized in that: The steam turbine is a unit with an inlet steam parameter not less than 35 Mpa / 630 °C or a unit in which the steam leakage temperature of the high-pressure front shaft seal during the full load operation range is higher than the allowable temperature of the high-pressure outer cylinder material.

4. A method for cooling the high-pressure front shaft seal during deep peak shaving of a high-parameter steam turbine according to claim 1, characterized in that: The steam turbine is a single reheat unit or a double reheat unit.

5. A high-pressure cylinder front shaft seal structure applied to a method for cooling the high-pressure front shaft seal during deep peak shaving of a high-parameter steam turbine according to any one of claims 1-4, characterized in that: It includes a high-pressure outer cylinder, a high-pressure inner cylinder and a high-pressure rotor arranged inside the high-pressure inner cylinder. A high-pressure inner and outer cylinder interlayer is formed between the high-pressure outer cylinder and the high-pressure inner cylinder. The high-pressure inner cylinder and the high-pressure rotor are sealed and assembled through the inner cylinder section of the high-pressure front shaft seal. The high-pressure outer cylinder and the high-pressure rotor are sealed and assembled through the outer cylinder section of the high-pressure front shaft seal. A steam seal ring is also provided at the end of the inner cylinder section of the high-pressure front shaft seal close to the outer cylinder section of the high-pressure front shaft seal. A steam leakage interface is provided inside the steam seal ring. The steam leakage interface is led out through a bypass pipeline, and a stop valve is provided on the bypass pipeline.

6. A front shaft seal structure of a high-pressure cylinder as described in claim 5, characterized in that: the bypass pipeline is connected to the reheater hot section or a regenerative extraction steam pipeline matching the temperature of the leakage steam.

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