Main steam valve of supercritical steam turbine

Abstract

The main steam valve of the supercritical steam turbine comprises a valve shell, an inner valve cover is arranged in the valve shell (1), an inner hole of the valve shell (1) is further provided with a whole circle of threads for installation, the main steam valve further comprises a threaded ring (3), and the threaded ring is connected into the valve shell through the threads and axially fixes the inner valve cover and a sealing ring; a temperature measuring hole is formed in the outer circle of the valve shell and used for measuring the temperature of an inner cavity of the valve shell. A valve shell flange cover (2) is arranged on the upper end face of the valve shell and fixed to the end face of the valve shell through bolts. A valve core (9) is arranged at the right end of the inner valve cover and is fixed on the inner valve cover (4) through a positioning pin (13); a valve rod and a valve element connected with the valve rod are arranged in the inner valve cover, and a lining-shaped sealing ring is arranged between the valve rod and the valve element connected with the valve rod and between the valve rod and the inner valve cover. The contact faces of the valve element (9) and the valve seat are made of PVD tungsten metal or alloy coatings.

Description

Technical Field

[0001] This utility model relates to the structure of the main steam valve of a supercritical steam turbine. Background Technology

[0002] As a representative of clean coal power technology in universities, the market prospects of supercritical steam turbine units are influenced by multiple factors, including global energy transition, policy guidance, technological innovation, and regional demand. Supercritical steam turbines will maintain an important market position in the medium term, up to 2030, especially in emerging Asian economies. In the long term, their survival depends on their ability to integrate into low-carbon energy systems through technological innovation.

[0003] Supercritical steam turbine units, by breaking through the limits of traditional thermodynamic cycles, have become a core technology for modern, efficient, and clean coal-fired power generation. They possess irreplaceable advantages in improving energy utilization efficiency and reducing carbon emissions. Supercritical steam turbine units are mainly used in large-scale coal-fired power plants and are suitable for high-load, continuous-operation power demand scenarios (such as industrial areas and urban power supply).

[0004] Traditional valve parts often use integral stainless steel, alloy steel, or alloy overlay on the sealing surface to improve their reliability under high temperature, corrosion and wear conditions. However, the requirements for the valve sealing surface are extremely high, and conventional methods cannot meet the sealing requirements. The sealing surface needs to have high hardness and resistance to corrosion, wear and impact. Some parts also use Stellite alloy overlay on the sealing surface, but Stellite alloy is expensive and is prone to defects such as cracks and porosity during welding.

[0005] The sealing surface now employs a special PVD coating process. The PVD coating has high hardness (up to 2000-3500HV, far exceeding that of the base material), high temperature resistance (maintaining stability above 800℃, suitable for the high-temperature environment of steam turbines), corrosion resistance, and low coefficient of friction. PVD coating technology provides an efficient surface strengthening solution for steam turbine valves, greatly reducing production and maintenance costs, and significantly extending the life of valve parts. Summary of the Invention

[0006] To address the aforementioned problems, the purpose of this invention is to prepare a main steam valve for a supercritical steam turbine, with the sealing surface employing a PVD coating process to solve issues such as easy wear, corrosion, and deformation of the sealing surface.

[0007] The technical solution of this utility model is a main steam valve for a supercritical steam turbine, including a valve housing 1. An inner valve cover 4 is provided inside the valve housing 1. The inner hole of the housing 1 is also provided with a full-circle thread for installation. It also includes a threaded ring 3, which is threadedly connected inside the valve housing 1 and axially fixes the inner valve cover 4 and the bushing-shaped sealing ring 5. Two temperature measuring holes are provided on the outer circumference of the valve housing 1 for measuring the temperature inside the valve housing 1. A valve housing flange cover 2 is provided on the upper end face of the valve housing 1, and the flange cover 2 is fixed to the end face of the valve housing 1 by bolts. A valve core 9 is provided at the right end of the inner valve cover 4, and the valve core 9 is fixed to the inner valve cover 4 by a positioning pin 13. A valve stem 11-1 and a connected valve core 11 are provided inside the inner valve cover 4. Four bushing-shaped sealing rings 5 ​​are provided between the valve stem 11-1, the connected valve core 11, and the inner valve cover 4. The valve stem 11-1 is fixed by a locking nut 7. A positioning sleeve 8 is also provided between the valve stem 11-1, the connected valve core 11, and the inner valve cover 4. The contact surfaces of the valve core 9 and the valve seat are both coated with tungsten metal or alloy PVD coating.

[0008] The valve stem has a valve core 9 at its left end, which is fixed to the right end of the inner valve cover 4 by a positioning pin 13. The valve body 1 also has a valve seat 10 inside, which is interference-fitted with the valve body 1.

[0009] Beneficial effects: The sealing surface is a critical part of a valve, and its quality directly affects the valve's service life. PVD coatings possess excellent high-temperature mechanical properties, corrosion resistance, and wear resistance. Therefore, PVD-coated sealing surfaces exhibit the following superior properties: PVD coatings increase hardness by 5-10 compared to the substrate; PVD coatings extend the sealing surface life by more than 3 times, reducing downtime maintenance frequency; PVD coatings offer 2-3 times better oxidation resistance at high temperatures than uncoated materials; and PVD coatings reduce the valve's corrosion rate by more than 80% in corrosive environments.

[0010] Supercritical steam turbines operate under complex conditions of high temperature, high pressure, high-speed steam erosion, and corrosive media (such as wet steam and sulfides). Traditional valve materials (such as stainless steel and nickel-based alloys) are prone to wear, corrosion, and high-temperature softening. Utilizing PVD coating technology on valve components within the turbine valve housing significantly improves key valve performance without altering the mechanical properties of the base material. The parallel dual-valve structure is also highly significant for controlling high-pressure steam. The dual-seat structure adopted in this application is also suitable for the long service life of supercritical steam turbines. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the main steam valve of the supercritical steam turbine of this utility model;

[0012] Figure 2 This is a schematic diagram of the internal structure of the valve body of this utility model;

[0013] Figure 3 for Figure 2 Enlarged view of point A in the middle. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] like Figure 1 , 2 As shown in Figure 3, the main steam valve of a supercritical steam turbine includes a valve housing 1, an inner valve cover 4 inside the valve housing 1, a sealing ring 5 at the right end of the inner valve cover 4, a full circle of threads in the inner hole of the valve housing 1, and a threaded ring 3. The threaded ring 3 is threadedly connected to the inside of the valve housing 1 and axially fixes the inner valve cover 4 and the sealing ring 5. The outer circle of the valve housing 1 has two temperature measuring holes for measuring the temperature inside the valve housing 1. The upper end face of the valve housing 1 has a valve housing flange cover 2, which is fixed to the end face of the valve housing 1 by bolts. The right end of the inner valve cover 4 has a valve core 9, which is fixed to the inner valve cover 4 by a positioning pin 13. The inner valve cover 4 has a valve stem 11-1 connected to the valve core 11 inside. There are four bushing-shaped sealing rings 5 ​​between the valve stem 11-1 and the inner valve cover 4. The valve stem 11-1 and the connected valve core 11 are fixed by a lock nut 7. A positioning sleeve 8 is also provided between the valve core 11 and the inner valve cover 4. The valve stem has a valve core 9 at its left end, and the valve core 9 (i.e., valve disc) is fixed to the right end of the inner valve cover 4 by a positioning pin 13. The valve body 1 also has a valve seat 10 inside, and the valve seat 10 is interference-fitted with the valve body 1.

[0016] A tungsten metal layer or alloy layer, such as titanium nitride (TiN) or aluminum nitride (AlN), is deposited using PVD physical plating (vacuum ion plating, magnetron sputtering, etc.); the thickness of the metal layer or alloy layer is preferably 50-200 nanometers.

[0017] In the figure, the inner wall of the threaded ring 3 is fixed to the valve body 1 by a sawtooth thread 16, which secures the inner valve cover 4 and the sealing ring.

[0018] The valve housing 1 contains an inner valve cover 4 and a valve core 9. Inside the valve housing 1, two sets of inner valve covers 4, valve cores 9, and valve seats are installed side-by-side. The valve seats contain a control flow channel 12.

[0019] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A main steam valve for a supercritical steam turbine, characterized in that, The valve housing (1) includes an inner valve cover (4) inside the valve housing (1). The inner hole of the valve housing (1) is also provided with a full-circle thread for installation, and a threaded ring (3) is also provided. The threaded ring is connected to the inside of the valve housing by the thread and fixes the inner valve cover and sealing ring axially. The outer circle of the valve housing is provided with a temperature measuring hole for measuring the temperature of the inner cavity of the valve housing. The upper end face of the valve housing is provided with a valve housing flange cover (2), which is fixed to the end face of the valve housing by bolts. The right end of the inner valve cover is provided with a valve core (9), which is fixed to the inner valve cover (4) by a positioning pin (13). The inner valve cover is provided with a valve stem (11-1) and a valve core connected to the valve stem. A bushing-shaped sealing ring (5) is provided between the valve stem, the connected valve core and the inner valve cover. The valve stem (11-1) is fixed by a lock nut (7). A positioning sleeve (8) is also provided between the valve stem, the connected valve core and the inner valve cover. The contact surfaces of the valve core (9) and the valve seat are all coated with PVD tungsten metal or alloy.

2. The main steam valve for a supercritical steam turbine according to claim 1, characterized in that, The valve stem is provided with a valve core at the left end, and the valve core is fixed to the right end of the inner valve cover by a positioning pin; the valve body is provided with a valve seat (10) inside, and the valve seat is interference-fitted with the valve body.

3. The main steam valve for a supercritical steam turbine according to claim 1, characterized in that, The valve housing contains two sets of inner valve covers, valve cores and valve seats installed side by side.

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