Steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation

Abstract

The invention relates to the technical field of steam turbines, and discloses a steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation, which comprises a shaft seal steam supply adjusting valve, a shaft seal steam main pipe, a shaft seal main pipe overflow adjusting valve, a high-pressure shaft seal chamber and a low-pressure shaft seal chamber, the other end of the shaft seal main pipe is connected with the shaft seal steam main pipe and the low-pressure shaft seal chamber, the shaft seal steam main pipe is connected with the shaft seal main pipe overflow adjusting valve and each shaft seal chamber pipeline, and the shaft seal main pipe overflow adjusting valve is connected with the low-pressure shaft seal chamber; the minimum opening degree of the shaft seal steam supply regulating valve is fixed to be a first set opening degree during daily operation of a steam turbine; and when the pressure of the shaft seal steam main pipe is as low as the set numerical value, the shaft seal steam supply regulating valve is directly opened to a second set opening degree. According to the shaft seal steam supply regulating valve, shaft seal supply interruption caused by slow opening speed of the shaft seal steam supply regulating valve can be avoided, and the problem that steam with substandard temperature is supplied into the shaft seal mother pipe in the process of shaft seal steam from self-supply to external supply is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbines, and in particular to a steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation. Background Art

[0002] A shaft seal system is installed in all types of steam turbines for power generation and industrial turbines. During the operation of the steam turbine, steam of a certain temperature and pressure should be supplied to the shaft seal system. The steam of the shaft seal system can be supplied by the steam turbine itself or by an external steam source. When the steam turbine is reduced in load or shut down due to an accident, insufficient self-supply of the shaft seal system will cause steam in the cylinder to leak out from the high-pressure shaft end and air to leak into the cylinder from the low-pressure shaft end of the steam turbine. Air leaking into the cylinder will cause serious accidents such as abnormal vacuum in the condenser and the end shaft seal will be rubbed due to the reduced clearance after cooling. Therefore, it is very important to ensure the reliable supply of steam for the shaft seal during the operation of the steam turbine.

[0003] The existing technical solutions are to gradually adjust the external steam source of the shaft seal when the self-supplied pressure of the shaft seal system is insufficient. This has the disadvantage of slow response speed. It is difficult to restore the steam for the shaft seal in time after the turbine is tripped due to a fault and the self-supplied steam for the shaft seal is lost. At the same time, when the turbine is reduced in load or tripped due to an accident, the steam pressure in the turbine cylinder is low, and the amount of steam overflowing to the shaft seal steam main pipe through the high-pressure shaft seal chamber pipeline is reduced, which will cause the shaft seal main pipe pressure to drop and the low-pressure shaft seal pressure to be insufficient. The conventional design adopts the method of opening the external steam source to supply the shaft seal steam regulating valve to maintain the entire main pipe pressure when the shaft seal main pipe pressure drops to a certain value. The external steam source supplies the shaft seal steam regulating valve which is opened after PID (proportional differential integral) calculation. The valve opening speed after PID calculation is limited. Too slow a valve opening speed makes it difficult to adapt to the sudden drop in shaft seal mother pipe pressure caused by turbine shutdown, which often causes the shaft seal mother pipe pressure to drop to zero for varying lengths of time, and the high and low pressure shaft seal steam is cut off, resulting in accidents such as "air leaking into the turbine shaft end", "abnormal condenser vacuum causing turbine shutdown", and "end shaft seal is damaged due to gap reduction and friction with turbine equipment". Summary of the invention

[0004] The present invention provides a steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation, thereby avoiding the problem of shaft seal supply interruption caused by slow opening speed of the shaft seal steam supply regulating valve and avoiding the problem of steam with substandard temperature being supplied into the shaft seal main pipe during the process of the shaft seal steam being supplied from self-supply to external supply.

[0005] The present invention provides a steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation, comprising a shaft seal steam supply regulating valve, a shaft seal steam main pipe, a shaft seal main pipe overflow regulating valve, a high-pressure shaft seal chamber and a low-pressure shaft seal chamber, wherein one end of the shaft seal steam supply regulating valve is connected to an external steam source for the shaft seal, and the other end is respectively connected to the shaft seal steam main pipe and the low-pressure shaft seal chamber, the shaft seal steam main pipe is respectively connected to the shaft seal main pipe overflow regulating valve and pipelines of each shaft seal chamber, and the shaft seal main pipe overflow regulating valve is connected to the low-pressure shaft seal chamber;

[0006] The pipelines of each shaft seal chamber include a high-pressure exhaust pipeline, a high-pressure inlet pipeline and a medium-low pressure inlet pipeline. The high-pressure exhaust pipeline is connected to the high-pressure cylinder exhaust end shaft seal of the high-pressure shaft seal chamber, the high-pressure inlet pipeline is connected to the high-pressure cylinder inlet end shaft seal of the high-pressure shaft seal chamber, and the medium-low pressure inlet pipeline is connected to the medium-low pressure inlet end shaft seal of the low-pressure shaft seal chamber;

[0007] The shaft seal steam supply regulating valve has the following configuration:

[0008] The minimum opening of the shaft seal steam supply regulating valve during normal turbine operation is fixed to a first set opening;

[0009] When the pressure of the shaft seal steam main pipe is lower than a set value, the shaft seal steam supply regulating valve is directly opened to the second set opening.

[0010] Furthermore, before the steam turbine is started or when the steam turbine is under low load, external steam is supplied as a steam source through the shaft seal steam supply regulating valve, and the steam in the shaft seal steam main pipe is supplied to the high-pressure shaft seal chamber and the low-pressure shaft seal chamber through the high-pressure steam inlet pipeline and the medium- and low-pressure steam inlet pipelines;

[0011] When the steam turbine is running at high load, the steam in the steam turbine overflows to the shaft seal steam main pipe through the steamer in the high-pressure shaft seal chamber, the pipeline connecting the high-pressure shaft seal chamber and the shaft seal main pipe overflow regulating valve, and then is supplied to the low-pressure shaft seal chamber, thereby realizing self-supply of turbine shaft seal steam.

[0012] Furthermore, when external steam is used as the steam source of the shaft seal steam main pipe, the pressure of the shaft seal steam main pipe is regulated by the shaft seal steam supply regulating valve through PID calculation; when the shaft seal is self-supplied, if the pressure of the shaft seal steam main pipe reaches a threshold value, the shaft seal main pipe overflow regulating valve is opened and the excess steam is discharged through PID calculation; when the pressure of the shaft seal steam main pipe is lower than a set value, the shaft seal steam supply regulating valve is directly opened to a second set opening without PID calculation.

[0013] Furthermore, the first set opening is 8% of the maximum opening of the shaft seal steam supply regulating valve.

[0014] Furthermore, the set value is 1kPa, and the second set opening is 35% of the maximum opening of the shaft seal steam supply regulating valve; that is, when the steam turbine is started and stopped normally and operates, the shaft seal steam main pipe pressure is maintained at 6kPa after PID operation. When the shaft seal steam main pipe pressure is as low as 1kPa, the shaft seal steam supply regulating valve opens quickly to 35% without PID calculation.

[0015] The beneficial effects of the present invention are:

[0016] 1. By fixing the minimum opening of the external steam source supplying the shaft seal steam regulating valve at a small opening instead of the conventional zero opening, the external steam supply for the shaft seal can be kept flowing at all times, avoiding the cooling of the steam in front of the valve due to long-term circulation, so that the external steam meets the shaft seal steam temperature requirements at all times and can be safely put into use at any time.

[0017] 2. The external steam source supplies the shaft seal steam regulating valve control to add a setting that directly opens to a certain opening without PID calculation when the "shaft seal steam mother pipe pressure is low to a certain value". This can respond as quickly as possible to the sudden drop in shaft seal mother pipe pressure caused by turbine shutdown, ensure the safe supply of high and low pressure shaft seal steam, and eliminate potential accidents such as "air leakage into the turbine shaft end", "abnormal condenser vacuum causing turbine shutdown", and "end shaft seal is damaged due to gap reduction and friction with turbine equipment". BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the steam supply for the shaft seal of the present invention.

[0019] Figure 2 This is a schematic diagram of shaft seal pressure adjustment optimization according to the present invention.

[0020] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0023] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0025] like Figure 1 As shown, the present invention provides a steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation, comprising a shaft seal steam supply regulating valve, a shaft seal steam main pipe, a shaft seal main pipe overflow regulating valve, a high-pressure shaft seal chamber and a low-pressure shaft seal chamber, wherein one end of the shaft seal steam supply regulating valve is connected to an external steam source for the shaft seal, and the other end is respectively connected to the shaft seal steam main pipe and the low-pressure shaft seal chamber, the shaft seal steam main pipe is respectively connected to the shaft seal main pipe overflow regulating valve and pipelines of each shaft seal chamber, and the shaft seal main pipe overflow regulating valve is connected to the low-pressure shaft seal chamber;

[0026] The pipelines of each shaft seal chamber include a high-pressure exhaust pipeline, a high-pressure inlet pipeline and a medium-low pressure inlet pipeline. The high-pressure exhaust pipeline is connected to the high-pressure cylinder exhaust end shaft seal of the high-pressure shaft seal chamber, the high-pressure inlet pipeline is connected to the high-pressure cylinder inlet end shaft seal of the high-pressure shaft seal chamber, and the medium-low pressure inlet pipeline is connected to the medium-low pressure inlet end shaft seal of the low-pressure shaft seal chamber;

[0027] The shaft seal steam supply regulating valve has the following configuration:

[0028] The minimum opening of the shaft seal steam supply regulating valve during normal turbine operation is fixed to a first set opening, that is, when the turbine is operating normally, the minimum opening of the shaft seal steam supply regulating valve is maintained at 8%.

[0029] When the shaft seal steam main pipe pressure is lower than the set value, the shaft seal steam supply regulating valve is directly opened to the second set opening, that is, during normal start-up and shutdown and operation of the steam turbine, the shaft seal steam main pipe pressure is maintained at 6 kPa after PID operation. When the shaft seal steam main pipe pressure is lower than the set value (1 kPa), the shaft seal steam supply regulating valve is quickly opened to 35% without PID calculation (this opening has been verified by experiments to maintain the shaft seal steam main pipe pressure not less than 6 kPa when the external shaft seal steam supply pressure is not less than 0.2 MPa).

[0030] Before the steam turbine is started or when the steam turbine is at low load, external steam is supplied as a steam source through the shaft seal steam supply regulating valve, and the steam in the shaft seal steam main pipe is supplied to the high-pressure shaft seal chamber and the low-pressure shaft seal chamber through the high-pressure steam inlet pipeline and the medium- and low-pressure steam inlet pipelines; when the steam turbine is running at high load, the steam in the steam turbine overflows to the shaft seal steam main pipe through the steamer in the high-pressure shaft seal chamber, the pipeline connecting the high-pressure shaft seal chamber and the shaft seal main pipe overflow regulating valve, and is then supplied to the low-pressure shaft seal chamber, thereby realizing self-supply of steam for the turbine shaft seal.

[0031] In addition, in the prior art, when the steam turbine is operating normally, the external steam source supplies the shaft seal steam regulating valve (shaft seal steam supply regulating valve) in a closed state, and the steam in front of the valve does not circulate for a long time, which may cause the shaft seal steam temperature to fail to meet the standard during the process of the shaft seal steam being supplied from the self-supply to the external supply, "the end shaft seal is cold and the gap is reduced and rubbed", and "the steam turbine equipment is damaged".

[0032] In the present invention, the shaft seal steam needs to ensure precise control of pressure and temperature. When external steam is used as the steam source of the shaft seal steam main pipe, the pressure of the shaft seal steam main pipe is adjusted by the shaft seal steam supply regulating valve through PID (proportional differential integral) operation; when the shaft seal is self-supplied, if the pressure of the shaft seal steam main pipe reaches a threshold, the shaft seal main pipe overflow regulating valve is opened and the excess steam is discharged through PID (proportional differential integral) operation; when the pressure of the shaft seal steam main pipe is lower than a set value, the shaft seal steam supply regulating valve is directly opened to the second set opening without PID operation.

[0033] The present invention provides two sets of protection measures on the basis of the conventional external steam source supplying the shaft seal steam regulating valve through PID (proportional differential integral) operation regulation:

[0034] 1. During normal turbine operation, the minimum opening of the external steam source supplying shaft seal steam regulating valve (shaft seal steam supply regulating valve) is fixed at a first set opening. By fixing the minimum opening of the external steam source supplying shaft seal steam regulating valve at a first set opening instead of the conventional zero opening, the external steam supplying shaft seal can be kept flowing at all times, avoiding the cooling of the steam in front of the valve due to long-term circulation, so that the external steam meets the shaft seal steam temperature requirements at all times and can be safely put into use at any time.

[0035] 2. To control the shaft seal steam regulating valve (steam supply regulating valve) supplied by the external steam source, add the setting that when the "steam main pipe pressure of the shaft seal drops to a certain value", it will open directly to the second set opening without PID calculation. Figure 2The figure shows the adjustment curve of the shaft seal steam supply regulating valve. It can be seen that the external steam source supplies the shaft seal steam regulating valve to control the increase of the "shaft seal steam mother pipe pressure is low to a certain value" and directly opens to the second set opening without PID calculation. This can respond to the sudden drop in shaft seal mother pipe pressure caused by turbine shutdown as quickly as possible, ensure the safe supply of high and low pressure shaft seal steam, and eliminate potential accidents such as "air leakage into the turbine shaft end", "abnormal condenser vacuum causing turbine shutdown", and "end shaft seal is damaged due to gap reduction and friction after cold shortage, causing damage to turbine equipment".

[0036] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, device, article or method including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, device, article or method. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other identical elements in the process, device, article or method including the element.

[0037] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation, characterized in that: It includes a shaft seal steam supply regulating valve, a shaft seal steam main pipe, a shaft seal main pipe overflow regulating valve, a high-pressure shaft seal chamber and a low-pressure shaft seal chamber. One end of the shaft seal steam supply regulating valve is connected to an external steam source for the shaft seal, and the other end is respectively connected to the shaft seal steam main pipe and the low-pressure shaft seal chamber. The shaft seal steam main pipe is respectively connected to the shaft seal main pipe overflow regulating valve and pipelines of each shaft seal chamber, and the shaft seal main pipe overflow regulating valve is connected to the low-pressure shaft seal chamber. The pipelines of each shaft seal chamber include a high-pressure exhaust pipeline, a high-pressure inlet pipeline and a medium-low pressure inlet pipeline. The high-pressure exhaust pipeline is connected to the high-pressure cylinder exhaust end shaft seal of the high-pressure shaft seal chamber, the high-pressure inlet pipeline is connected to the high-pressure cylinder inlet end shaft seal of the high-pressure shaft seal chamber, and the medium-low pressure inlet pipeline is connected to the medium-low pressure inlet end shaft seal of the low-pressure shaft seal chamber; The shaft seal steam supply regulating valve has the following configuration: The minimum opening of the shaft seal steam supply regulating valve during normal turbine operation is fixed to a first set opening; When the pressure of the shaft seal steam main pipe is lower than a set value, the shaft seal steam supply regulating valve is directly opened to the second set opening.

2. The steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation according to claim 1, characterized in that: Before the steam turbine is started or when the steam turbine is under low load, external steam is supplied as a steam source through the shaft seal steam supply regulating valve, and the steam in the shaft seal steam main pipe is supplied to the high-pressure shaft seal chamber and the low-pressure shaft seal chamber through the high-pressure steam inlet pipeline and the medium- and low-pressure steam inlet pipelines; When the steam turbine is running at high load, the steam in the steam turbine overflows to the shaft seal steam main pipe through the steamer in the high-pressure shaft seal chamber, the pipeline connecting the high-pressure shaft seal chamber and the shaft seal main pipe overflow regulating valve, and then is supplied to the low-pressure shaft seal chamber, thereby realizing self-supply of turbine shaft seal steam.

3. The steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation according to claim 2, characterized in that: When external steam is used as the steam source of the shaft seal steam main pipe, the pressure of the shaft seal steam main pipe is regulated by the shaft seal steam supply regulating valve through PID calculation; when the shaft seal is self-supplied, if the pressure of the shaft seal steam main pipe reaches a threshold value, the shaft seal main pipe overflow regulating valve is opened through PID calculation to discharge excess steam; when the pressure of the shaft seal steam main pipe is lower than a set value, the shaft seal steam supply regulating valve is directly opened to the second set opening without PID calculation.

4. The steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation according to claim 1, characterized in that: The first set opening is 8% of the maximum opening of the shaft seal steam supply regulating valve.

5. The steam turbine shaft seal system based on shaft seal steam pressure adjustment during operation according to claim 3, characterized in that: The set value is 1kPa, and the second set opening is 35% of the maximum opening of the shaft seal steam supply regulating valve; that is, when the turbine is started and stopped normally and operates, the shaft seal steam main pipe pressure is maintained at 6kPa after PID operation. When the shaft seal steam main pipe pressure is as low as 1kPa, the shaft seal steam supply regulating valve opens quickly to 35% without PID calculation.

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