A variable unloading force steam turbine regulating valve and its working method

Abstract

This invention belongs to the field of steam turbine power generation in thermal power units, specifically disclosing a variable unloading force steam turbine regulating valve and its operating method. The aim is to redesign the regulating valve structure to solve the vibration, abnormal noise, and load fluctuation problems caused by valve disc suspension. This invention involves setting a pressure balance hole on the valve sleeve and a control unloading structure on the valve disc in a conventional steam turbine regulating valve structure. This increases the pressure in the chamber between the valve disc and the valve sleeve during valve regulation, increases the downward steam force on the valve disc, and reduces the unloading force under regulation conditions, thus pressing the valve disc firmly against the valve stem and preventing valve disc suspension. This invention solves the defects caused by valve disc suspension, thereby improving the unit's economy and reliability.

Description

Technical Field

[0001] This invention belongs to the field of steam turbine power generation in thermal power units, and specifically relates to a variable unloading force steam turbine regulating valve and its working method. Background Technology

[0002] Modern steam turbine generator sets are equipped with main steam valves and regulating valves to control the operation of the unit. The main steam valve is the first main valve through which main steam enters the turbine. It is a key component ensuring the safe start-up, shutdown, and operation of the unit. Its main function is to quickly and automatically close in emergency situations, cutting off the main steam passage to the turbine and shutting down the unit to prevent excessive overspeed or to avoid the escalation of an accident. The regulating valve is used to adjust the steam flow into the turbine to meet the power requirements of the power grid or maintain the grid frequency. It can also be used to adjust the load distribution among parallel-operating units. When the unit sheds load, it should quickly close to prevent overspeed and maintain stable no-load operation of the unit.

[0003] regulating valve, such as Figure 1 As shown, when the unit starts up and the valve needs to be opened, the oil motor supplies oil and compresses the spring in the control seat to overcome the steam pressure on the valve disc and the weight of the valve stem and valve disc, pulling the valve disc upward and opening the valve. When the unit is adjusted or shut down and the valve needs to be closed, the oil motor releases oil, the spring expands, presses the valve stem down, and drives the valve disc to close quickly.

[0004] When the unit is operating with conventional valves, the throttling effect of the small gap between the valve sleeve and the valve disc is very large. The pressure in the intermediate chamber is lower than that in the upstream chamber, which is 95.2% of the upstream chamber pressure. The pressure in the downstream chamber is 95% of the upstream chamber pressure. The pressure difference between the intermediate chamber and the downstream chamber is 0.2% of the upstream chamber pressure.

[0005] Due to factors such as oxygenation of boiler feedwater, oxide scale commonly accumulates on valve core components such as valve discs, valve stems, and valve sleeves. This causes the clearance between the valve sleeve and the valve disc to decrease, and the wear stroke of the pre-opening valve to increase. At this time, the throttling effect of the small gap between the valve sleeve and the valve disc increases, which can easily lead to a decrease in the pressure of the intermediate chamber. Under certain specific operating conditions, the pressure of the intermediate chamber is the same as that of the downstream chamber, which is 95% of the pressure of the upstream chamber. In this case, the valve disc will be suspended under the blowing of steam. The valve disc will float up and down within the pre-opening stroke range, colliding with the valve stem to generate vibration and abnormal noise. At the same time, it will cause fluctuations in valve flow, resulting in significant fluctuations in unit load. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a variable unloading force turbine regulating valve and its operating method, and redesigns the regulating valve structure to solve the problems of vibration, abnormal noise and load fluctuation caused by valve disc suspension.

[0007] To achieve the objective of this invention, the technical solution adopted is as follows:

[0008] A variable unloading force steam turbine regulating valve includes: a hydraulic actuator 1, an operating seat 2, a valve cover 3, a valve housing 4, a valve seat 5, a valve stem 6, a valve sleeve 7, a valve disc 8, and a pre-opening valve 9; wherein, the valve sleeve 7 is provided with a pressure balance hole, and the valve disc 8 is provided with a control unloading structure.

[0009] Furthermore, the control unloading structure is located on the outer wall of the valve disc 8 and is in the shape of a groove. When the valve stem 6 is pressed into the closed state, the control unloading structure does not participate in the operation of the regulating valve, and the valve sleeve 7 and the valve disc 8 are in contact. When the valve stem 6 is lifted to open the valve, the control unloading structure connects the valve front chamber 10 and the intermediate chamber 11.

[0010] Furthermore, a pressure balance hole is provided on the valve sleeve 7, and the pressure balance hole is through the top and bottom. The upper part of the pressure balance hole is connected to the intermediate chamber 11. When the valve stem 6 is pressed into the closed state, the lower part of the pressure balance hole is tightly fitted with the outer wall of the valve disc 8. When the valve stem 6 is lifted to open the valve, the lower part of the pressure balance hole is connected to the valve front chamber 10.

[0011] Furthermore, there are one or more pressure balancing holes.

[0012] The operating method of the variable unloading force steam turbine regulating valve provided by the present invention includes:

[0013] (1) When the valve is just opened, the valve stem is lifted upwards, and the steam in the front chamber flows into the intermediate chamber through the small gap between the valve sleeve and the valve disc, and further enters the rear chamber through the pre-opening valve. The valve stem continues to open upwards, and the pre-opening valve is fully open. At this time, due to the small gap between the valve sleeve and the valve disc and the large flow area of ​​the pre-opening valve, there is an obvious throttling effect in the small gap between the valve sleeve and the valve disc. At this time, the pressure in the intermediate chamber is 20% of the pressure in the front chamber, the pressure in the rear chamber is 2% of the pressure in the front chamber, and the pressure difference between the intermediate chamber and the rear chamber is 18% of the pressure in the front chamber. At this time, the pressure difference is relatively small, and the valve's hydraulic actuator can easily open the valve disc.

[0014] (2) The valve stem continues to open upward with the valve disc. The control unloading structure of the valve disc connects with the pressure balance hole of the valve sleeve. The steam in the front chamber flows to the middle chamber through the pressure balance hole. The pressure in the middle chamber increases to 99% of the pressure in the front chamber. At this time, the valve disc is open. The pressure in the rear chamber is 95% of the pressure in the front chamber. The pressure difference between the middle chamber and the rear chamber is 4% of the pressure in the front chamber. This pressure difference firmly presses the valve disc onto the valve stem and moves with the valve stem to precisely regulate the steam flow through the valve.

[0015] Among them, such as Figure 5 As shown, the steam in the valve pre-valve chamber passes through the small gap between the valve sleeve and the valve disc at position φA; the control unloading structure is located at position φB; and the pressure balance hole is located at position φC.

[0016] The above technical solution has the following beneficial effects:

[0017] 1. This structure increases the pressure in the intermediate chamber during normal operation after the valve is opened, thereby increasing the steam force acting on the valve disc, reducing the unloading force under valve operating conditions, and pressing the valve disc tightly onto the valve stem, thus preventing the disc from floating.

[0018] 2. The variable unloading force regulating valve provided by the present invention does not change the steam passage when the valve is just opened and the valve disc is not open. Therefore, it does not affect the pressure difference between the intermediate chamber and the valve rear chamber when the large valve disc is opened, nor does it affect the pressure difference between the intermediate chamber and the valve rear chamber when the valve is opened. It does not require a larger hydraulic motor output, so it does not require replacing the spring. It does not increase the impact load when closing, and it does not require redesigning valve disc, valve stem, valve seat and other valve core components.

[0019] 3. The technical solution provided by this invention ensures that when the valve disc is open, the pressure difference between the intermediate chamber and the downstream chamber is still 18% of the pressure in the upstream chamber. After the valve is opened and enters the operation adjustment stage, the pressure difference between the intermediate chamber and the downstream chamber increases to 4% of the pressure in the upstream chamber. When a conventional valve unit is in operation, the pressure difference between the intermediate chamber and the downstream chamber is 0.2% of the pressure in the upstream chamber. Therefore, the problem of valve disc floating is avoided, and the operational stability is effectively improved. Attached Figure Description

[0020] Figure 1 This is a structural diagram of a conventional steam turbine regulating valve core.

[0021] Figure 2 This is a structural diagram of the valve core of a variable unloading force steam turbine regulating valve;

[0022] Figure 3 Diagram showing the fully open state of the pre-opening valve of the variable unloading force steam turbine regulating valve;

[0023] Figure 4 Diagram showing the normal parameter adjustment state of valves in a variable unloading force steam turbine;

[0024] Figure 5 This is a structural diagram of the regulating valve system for a variable unloading force steam turbine.

[0025] Figure 6 This is a structural diagram of the valve sleeve of a variable unloading force steam turbine regulating valve.

[0026] Figure 7 This is a structural diagram of the valve core of a variable unloading force steam turbine regulating valve;

[0027] In the diagram: 1-Hydraulic actuator, 2-Spring, 3-Valve cover, 4-Valve housing, 5-Valve seat, 6-Valve stem, 7-Valve sleeve, 8-Valve disc, 9-Pre-opening valve, 10-Pre-valve chamber, 11-Intermediate chamber, 12-Post-valve chamber. Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] A variable unloading force steam turbine regulating valve includes: a hydraulic actuator 1, an operating seat 2, a valve cover 3, a valve housing 4, a valve seat 5, a valve stem 6, a valve sleeve 7, a valve disc 8, and a pre-opening valve 9; the valve sleeve 7 is provided with a pressure balance hole, and the valve disc 8 is provided with a control unloading structure.

[0031] The control unloading structure is located on the outer wall of the valve disc 8 and is in the shape of a groove. When the valve stem 6 is pressed closed, the control unloading structure does not participate in the operation of the regulating valve, and the valve sleeve 7 and the valve disc 8 are in contact. When the valve stem 6 is lifted to open the valve, the control unloading structure connects the valve front chamber 10 and the intermediate chamber 11.

[0032] The pressure balance hole is located on the valve sleeve 7, and the pressure balance hole is open from top to bottom. The upper part of the pressure balance hole is connected to the intermediate chamber 11. When the valve stem 6 is pressed closed, the lower part of the pressure balance hole is tightly fitted to the outer wall of the valve disc 8. When the valve stem 6 is lifted to open the valve, the lower part of the pressure balance hole is connected to the valve front chamber 10.

[0033] In this embodiment, four pressure balancing holes are provided.

[0034] Example 2

[0035] A method for operating a variable unloading force steam turbine regulating valve includes:

[0036] (1) such as Figure 3 As shown, the pressure in the inlet chamber is 25 MPa. When the valve is first opened, the valve stem is lifted upwards, and the steam in the inlet chamber flows into the intermediate chamber through the small gap between the valve sleeve and the valve disc, and further enters the outlet chamber through the pre-opening valve. As the valve stem continues to open upwards, the pre-opening valve is fully open. At this time, due to the small gap between the valve sleeve and the valve disc and the large flow area of ​​the pre-opening valve, there is a significant throttling effect in the small gap between the valve sleeve and the valve disc. At this time, the pressure in the intermediate chamber is 5 MPa, the pressure in the outlet chamber is 0.5 MPa, and the pressure difference between the intermediate chamber and the outlet chamber is 4.5 MPa. At this time, the pressure difference is relatively small, and the valve's hydraulic actuator can easily open the valve disc.

[0037] (2) The valve stem continues to open upward with the valve disc. The control unloading structure of the valve disc is connected to the pressure balance hole of the valve sleeve. The steam in the front chamber flows directly to the middle chamber through the pressure balance hole without throttling. The pressure in the middle chamber is 24.75 MPa. At this time, the valve disc is open and the pressure in the rear chamber is 23.75 MPa. The pressure difference between the middle chamber and the rear chamber is 1 MPa. This pressure difference firmly presses the valve disc onto the valve stem and moves with the valve stem to accurately regulate the steam flow through the valve.

[0038] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for operating a variable unloading force steam turbine regulating valve, characterized in that: The regulating valve includes a hydraulic actuator (1), a control seat (2), a valve cover (3), a valve housing (4), a valve seat (5), a valve stem (6), a valve sleeve (7), a valve disc (8), and a pre-opening valve (9); the valve sleeve (7) is provided with a pressure balance hole, and the valve disc (8) is provided with a control unloading structure; The control unloading structure is set on the outer wall of the valve disc (8) and is in the shape of a groove. When the valve stem (6) is pressed closed, the valve sleeve (7) and the valve disc (8) are in contact, and the control unloading structure does not participate in the operation of the regulating valve. When the valve stem (6) is lifted to open the operation, the control unloading structure connects the valve front chamber (10) and the intermediate chamber (11). The pressure balance hole is set on the valve sleeve (7), and the pressure balance hole is through the top and bottom. The upper part of the pressure balance hole is connected to the intermediate chamber (11). When the valve stem (6) is pressed closed, the lower part of the pressure balance hole is tightly fitted to the outer wall of the valve disc (8). When the valve stem (6) is lifted to open the valve, the lower part of the pressure balance hole is connected to the valve front chamber (10). The pressure balancing hole may be one or more; The working method includes the following steps: (1) When the valve is just opened, the valve stem is lifted upwards, and the steam in the front chamber flows into the middle chamber through the small gap between the valve sleeve and the valve disc. It then passes through the pre-opening valve and enters the rear chamber. The valve stem continues to open upwards, and the pre-opening valve is fully open. At this time, the pressure difference between the middle chamber and the rear chamber is moderate, and the hydraulic actuator can easily open the valve disc. (2) The valve stem continues to open upward with the valve disc. The control unloading structure of the valve disc connects with the pressure balance hole of the valve sleeve. The steam in the front chamber flows to the middle chamber through the pressure balance hole. The pressure in the middle chamber increases. At this time, the valve disc is open. The pressure difference between the middle chamber and the rear chamber presses the valve disc firmly onto the valve stem. It moves with the valve stem and precisely regulates the steam flow through the valve. The intermediate chamber pressure in step (1) is 20% of the pressure in the pre-valve chamber, the post-valve chamber pressure is 2% of the pressure in the pre-valve chamber, and the pressure difference between the intermediate chamber and the post-valve chamber is 18% of the pressure in the pre-valve chamber.

2. The operating method of the variable unloading force turbine regulating valve according to claim 1, characterized in that: The intermediate chamber pressure in step (2) is 99% of the pressure in the pre-valve chamber, the post-valve chamber pressure is 95% of the pressure in the pre-valve chamber, and the pressure difference between the intermediate chamber and the post-valve chamber is 4% of the pressure in the pre-valve chamber.

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