Mechanical throttle for regulating the steam pressure in the shaft seal of a steam turbine

Abstract

This invention provides a mechanical throttling mechanism for regulating steam supply pressure at a turbine shaft seal, relating to the field of turbine auxiliary valves. It includes a valve body and a valve stem. A top actuator is located at the upper end of the valve body. One side of the valve body is the inlet air terminal, and the other side is the outlet air terminal. A double-layer diaphragm assembly is located within the top actuator. The double-layer diaphragm assembly includes an upper diaphragm and a lower diaphragm, both positioned in the middle of the top actuator with their outer edges in contact with atmospheric pressure air. A pressure chamber is formed above the upper diaphragm. A heat-insulating interlayer filled with heat-insulating packing is provided between the upper and lower diaphragms. A spring assembly is arranged below the lower diaphragm, and the spring assembly is isolated from the high-temperature steam medium. This mechanical throttling mechanism for regulating steam supply pressure at a turbine shaft seal provides real-time feedback of the downstream pressure to the pressure chamber via a pressure tap. It relies on the diaphragm medium pressure and spring preload to form a self-balancing structure. When the pressure is too high, the valve core moves downward to reduce the throttling area and lower the pressure; when the pressure is too low, the valve core moves upward to open the throttling area and replenish the pressure.

Description

Technical Field

[0001] This invention relates to the field of steam turbine auxiliary valves, specifically a mechanical throttling mechanism for regulating the steam supply pressure of a steam turbine shaft seal. Background Technology

[0002] The steam supply system for turbine shaft seals is used to supply low-pressure, constant-temperature steam to the sealing components of the turbine shaft end, preventing air leakage and high-temperature steam leakage from the unit. The stability of the steam pressure in the shaft seal header directly determines the vacuum and lubricating oil operation safety of the unit. Therefore, a self-operated mechanical throttling and pressure regulating mechanism is required to achieve automatic constant steam supply pressure.

[0003] Currently, most mainstream shaft seal pressure regulating and throttling devices in the industry adopt a single-layer diaphragm and single-spring force balance structure. They generally use an external pressure tap to collect the steam pressure after the valve to drive the diaphragm to complete the throttling opening adjustment. The single-layer metal diaphragm directly contacts the high-temperature steam after the valve, and the heat is continuously conducted downward to the lower spring. The single central spring is prone to creep decay due to long-term exposure to high temperature. Once the pressure of the main pipe increases during operation, the equipment cannot correct itself and requires maintenance personnel to manually readjust it on-site. If manual adjustment is not timely, faults such as shaft seal overpressure and unit vacuum fluctuations may occur, and there is a significant delay in pressure regulation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a mechanical throttling mechanism for regulating the steam supply pressure of the turbine shaft seal, which solves the problem that the delay in regulation can easily lead to unit malfunctions.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a mechanical throttling mechanism for regulating steam supply pressure of a steam turbine shaft seal, comprising a valve body and a valve stem, wherein a top actuator is provided at the upper end of the valve body, one side of the valve body is the inlet end of the valve, and the other side is the outlet end of the valve; The top actuator is equipped with a double-layer diaphragm assembly, which includes an upper diaphragm and a lower diaphragm. Both are located in the middle of the top actuator and their outer edges are in contact with atmospheric pressure air. A pressure chamber is formed above the upper diaphragm, and a heat insulation interlayer filled with heat insulation filler is provided between the upper diaphragm and the lower diaphragm. A spring assembly is arranged below the lower diaphragm, and the spring assembly is isolated from the high-temperature steam medium. The valve stem is rigidly connected to the double-layer diaphragm assembly. The bottom end of the valve stem is provided with an integrally formed valve core. When the pressure at the outlet end of the valve changes, the double-layer diaphragm assembly and the valve stem synchronously adjust the size of the air inlet channel entering the shaft seal.

[0006] Preferably, the heat insulation interlayer is filled with high-temperature resistant heat insulation filler to prevent high temperature from being conducted downwards to the spring assembly.

[0007] Preferably, the spring assembly includes a compression plate, and the bottom surface of the compression plate is provided with a plurality of springs, which are distributed in a circumferential manner.

[0008] Preferably, the top actuator includes an upper cover plate and a lower cover plate, with the double-layer diaphragm assembly located between the upper cover plate and the lower cover plate.

[0009] Preferably, the pressure chamber is connected to an external pressure tapping pipe, and the pressure tapping pipe is connected to the air outlet end of the valve body.

[0010] Preferably, the valve body has an adjusting cylinder inside, the valve core is located inside the adjusting cylinder, and the adjusting cylinder has a throttling hole in the middle.

[0011] Preferably, the inlet end of the valve near the adjusting cylinder is connected to the adjusting cylinder; the outlet end of the valve adjacent to the inlet end of the valve is connected to the adjusting cylinder.

[0012] Preferably, a flange sealing structure is provided between the lower end of the top actuator and the upper end of the valve body for sealing the connection.

[0013] Preferably, the flange sealing structure has a through groove at its upper end, and the through groove contains an elastic element and several sealing elements, with a mounting plate at the upper end of the elastic element.

[0014] Preferably, the flange sealing structure has a positioning ring inside, and the sealing element is limited and assembled inside the positioning ring.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The steam turbine shaft seal steam supply pressure regulating mechanical throttling mechanism, by setting an insulating interlayer filled with heat insulation packing between the double-layer diaphragm, can block the downward transfer of high-temperature steam heat, avoid the spring assembly from heat creep and elasticity attenuation, eliminate the need for frequent manual pressure adjustment, and prevent shaft seal overpressure and unit vacuum fluctuation problems caused by manual adjustment lag.

[0016] 2. The steam turbine shaft seal steam supply pressure regulating mechanical throttling mechanism, by exposing the outer edge of the double-layer diaphragm and allowing it to contact atmospheric air, enables a small amount of leaking steam in the interlayer to dissipate heat and release pressure along the edge of the diaphragm, preventing the medium from accumulating in the interlayer and causing the diaphragm to bulge and tear, thus extending the service life of the diaphragm. At the same time, it facilitates intuitive observation of the leakage status and can utilize the atmospheric environment to continuously dissipate heat from the interlayer.

[0017] 3. The steam turbine shaft seal steam supply pressure regulating mechanical throttling mechanism provides real-time feedback of the downstream pressure to the pressure chamber via the pressure tapping pipe. It relies on the diaphragm medium pressure and spring preload to form a self-balancing structure. When the pressure is too high, the valve core moves down to reduce the throttling area and lower the pressure. When the pressure is too low, the valve core moves up to open the throttling area and replenish the pressure. It can automatically stabilize the pressure under random operating conditions without manual adjustment, and the adjustment response is lag-free, stably maintaining the shaft seal steam supply pressure. Attached Figure Description

[0018] Figure 1 This is a front view of the valve body structure of the present invention; Figure 2 This is a schematic diagram of the front cross-sectional structure of the valve body of the present invention; Figure 3 For the present invention Figure 2 Enlarged schematic diagram of the structure at point A in the middle; Figure 4 This is a schematic diagram of the right-side cross-sectional structure of the valve body of the present invention; Figure 5 This is a schematic diagram of the diaphragm structure of the present invention; Figure 6 This is a schematic diagram of the cross-sectional structure of the diaphragm in this invention; Figure 7 This is a schematic diagram of the upper cover plate structure of the present invention; Figure 8 This is a schematic diagram of the exploded structure of the upper cover plate of the present invention.

[0019] The components are as follows: 1. Valve body; 2. Top actuator; 201. Upper cover plate; 202. Lower cover plate; 3. Inlet valve; 4. Outlet valve; 5. Double diaphragm assembly; 501. Upper diaphragm; 502. Lower diaphragm; 6. Pressure chamber; 7. Thermal insulation layer; 8. Spring assembly; 801. Extrusion plate; 9. Valve stem; 10. Valve core; 11. Pressure tap; 12. Adjusting cylinder; 13. Through hole; 14. Flange sealing structure; 15. Through groove; 16. Elastic element; 17. Mounting plate; 18. Positioning ring. Detailed Implementation

[0020] like Figures 1-8 As shown, a mechanical throttling mechanism for regulating the steam supply pressure of a turbine shaft seal is mainly used in the scenario of stabilizing the steam supply pipeline of a turbine shaft seal. It includes a valve body 1 and a valve stem 9. A top actuator 2 is installed on the upper end of the valve body 1. One side of the valve body 1 is the inlet end 3 and the other side is the outlet end 4. The inlet end 3 is connected to the steam supply header of the unit for introducing high-temperature saturated steam. The outlet end 4 is connected to the turbine shaft seal chamber to continuously supply sealing steam to the shaft seal.

[0021] A double-layer diaphragm assembly 5 is clamped and installed in the middle of the cavity of the top actuator 2. The double-layer diaphragm assembly 5 is composed of an upper diaphragm 501 and a lower diaphragm 502 arranged in layers. The two are located in the middle of the top actuator 2 and their outer edges are in contact with atmospheric pressure air. The edges of the upper diaphragm 501 and the lower diaphragm 502 are simultaneously clamped between the upper cover plate 201 and the lower cover plate 202 of the top actuator 2. The outer edges of the two diaphragms extend completely outward and are directly exposed to the external atmospheric pressure air environment.

[0022] The upper space of the upper diaphragm 501 encloses to form a sealed pressure chamber 6. The pressure chamber 6 is connected to an external pressure tapping pipe 11. The end of the pressure tapping pipe 11 is connected to the valve outlet 4 of the valve body 1. The steam pressure on the valve shaft seal side is collected in real time, and the pressure medium is introduced into the pressure chamber 6 and a uniform force is applied downward to the upper diaphragm 501.

[0023] A heat insulation interlayer 7 filled with heat insulation filler is provided between the upper diaphragm 501 and the lower diaphragm 502. The heat insulation interlayer 7 is filled with high-temperature resistant aerogel heat insulation filler to form a heat insulation layer. The dense heat insulation filler can block the high-temperature steam in the upper pressure chamber 6 from being conducted downward to the lower spring assembly 8. The spring assembly 8 is arranged below the lower diaphragm 502. The spring assembly 8 is isolated from the high-temperature steam medium. The lower diaphragm 502 completely isolates the upper high-temperature steam channel. The cavity where the spring assembly 8 is located is a dry, room-temperature, sealed cavity and will not come into direct contact with salt-containing high-temperature steam, effectively preventing the spring from rusting.

[0024] The spring assembly 8 adopts a structure in which multiple springs are evenly arranged along the circumference. The multiple springs synchronously share the axial load of the diaphragm, and the diaphragm is subjected to uniform force throughout the circumference. There will be no unilateral skew or plastic deformation, and the valve stem 9 will slide smoothly without jamming.

[0025] If a small amount of steam leaks into the insulation interlayer 7, the medium can fully contact the air through the outer edge of the diaphragm for heat exchange and natural dissipation, avoiding the accumulation and pressure rise of steam inside the interlayer, reducing the risk of diaphragm bulging, tearing and failure, and allowing for direct observation of the leakage situation, which is convenient for operation and maintenance inspection.

[0026] The valve stem 9 passes through the center of the double-layer diaphragm assembly 5 vertically from top to bottom. The valve stem 9 is rigidly sealed and fixed to the center of the upper diaphragm 501 and the lower diaphragm 502. When the double-layer diaphragm assembly 5 moves up and down, it can synchronously drive the valve stem 9 to rise and fall as a whole.

[0027] The bottom end of the valve stem 9 is provided with an integrally formed valve core 10. When the pressure at the outlet end 4 after the valve changes, the double-layer diaphragm assembly 5 links the valve stem 9 to synchronously adjust the size of the air inlet channel entering the shaft seal. The inlet end 3 and the outlet end 4 after the valve are respectively connected to the inner cavity of the adjusting cylinder 12. All steam media flow through the adjusting cylinder 12 to complete the throttling and pressure regulation.

[0028] When the steam pressure at the valve outlet 4 increases, the pressure inlet pipe 11 sends the high-pressure medium into the pressure chamber 6. The medium pressure squeezes the upper diaphragm 501 downward, causing the double-layer diaphragm assembly 5 to shift downward as a whole. This simultaneously drives the valve stem 9 and valve core 10 to move downward. The valve core 10 reduces the effective flow area of ​​the throttling orifice 13 in the middle of the adjusting cylinder 12, closing the air inlet channel and reducing the total amount of steam flowing into the shaft seal, thus achieving pressure reduction. When the pressure at the valve outlet 4 is lower than the set standard value, the pre-tightening force of the lower spring assembly 8 pushes the lower diaphragm 502 upward, causing the double-layer diaphragm assembly 5 to reset upward as a whole. The valve stem 9 simultaneously lifts the valve core 10, increasing the flow area of ​​the throttling orifice 13, widening the air inlet channel, increasing steam supply, and raising the shaft seal pressure.

[0029] The intake throttling is automatically adjusted by linking a single valve stem 9 with the valve core 10. The pressure is stabilized by self-balancing the medium pressure and spring force throughout the process. There is no need for manual operation and repeated manual adjustment. There is no lag problem caused by untimely manual adjustment leading to shaft seal overpressure or unit vacuum fluctuation.

[0030] A spring assembly 8 is arranged in the cavity space below the lower diaphragm 502. The spring assembly 8 includes a horizontally arranged extrusion plate 801. The upper surface of the extrusion plate 801 is in contact with the bottom surface of the lower diaphragm 502. Several springs are provided on the bottom surface of the extrusion plate 801, and the springs are distributed in a circumferential manner.

[0031] When in use, the double-layer diaphragm assembly 5 moves downward and presses down on the extrusion plate 801. The extrusion plate 801 simultaneously compresses multiple springs at the bottom. The multiple springs distribute all the axial load along the circumference, so that the extrusion plate 801 and the double-layer diaphragm assembly 5 are subjected to uniform force throughout the process, and there will be no unilateral load tilting, thus avoiding local plastic deformation of the diaphragm.

[0032] The top actuator 2 is assembled by upper cover plate 201 and lower cover plate 202. The double-layer diaphragm assembly 5 is clamped between the mating end faces of upper cover plate 201 and lower cover plate 202. The upper and lower cover plates 202 are locked with bolts to achieve the pressing and positioning of the outer edge of the double-layer diaphragm.

[0033] The upper cover plate 201 and the lower cover plate 202 are assembled together to evenly constrain the edges of the double-layer diaphragm assembly 5. Only the central area of ​​the diaphragm floats up and down synchronously with the valve stem 9, while the outer edge is reliably fixed to prevent the diaphragm from slipping as a whole during pressure regulation. At the same time, the outer edge of the double-layer diaphragm assembly 5 extends outward from the gap between the upper and lower cover plates 202, directly contacting the external atmospheric pressure air. The small amount of leaked steam in the interlayer can be dissipated in time to prevent the diaphragm from being damaged by the pressure inside the interlayer.

[0034] A cylindrical adjusting cylinder 12 is fixedly installed in the inner cavity of the valve body 1. The valve core 10 can be slidably stored inside the adjusting cylinder 12 in the vertical direction. Throttling holes 13 are evenly opened in the middle of the adjusting cylinder 12 in the circumferential direction. All steam media must pass through the throttling holes 13 to complete the throttling and pressure reduction.

[0035] The valve body 1 has an inlet end 3 and an outlet end 4 formed on both sides. The inner channel of the inlet end 3 is directly connected to the side wall of the regulating cylinder 12. High-temperature steam is sent from the inlet end 3 into the inner cavity of the regulating cylinder 12. The outlet end 4 is also connected to the inside of the regulating cylinder 12 through the channel near the inlet end 3. The steam after being throttled and stabilized by the throttling orifice 13 flows from the inside of the regulating cylinder 12 into the outlet end 4 and is then transported to the turbine shaft seal header.

[0036] When the valve stem 9 moves the valve core 10 up and down, the area of ​​the throttling orifice 13 blocked by the outer wall of the valve core 10 changes synchronously. When the downstream pressure increases, the valve core 10 moves downward, blocking the throttling orifice 13, reducing the flow area and decreasing the intake airflow. When the downstream pressure is too low, the valve core 10 moves upward, increasing the exposed area of ​​the throttling orifice 13 and increasing the steam intake, thus achieving automatic balance of the shaft seal steam supply pressure. The entire medium passage is integrated within the adjusting cylinder 12, resulting in centralized throttling, a regular flow path, and fast pressure regulation response, avoiding pressure fluctuations caused by eddies inside the valve body 1.

[0037] A flange sealing structure 14 is provided between the lower end of the top actuator 2 and the upper end of the valve body 1 to seal the assembly gap between the valve body 1 and the top actuator 2, and to prevent high-temperature steam from leaking out from the joint surface.

[0038] The flange sealing structure 14 has a through groove 15 on its upper end. The through groove 15 contains an elastic element 16 and several sealing elements. The upper end of the elastic element 16 is provided with a mounting plate 17. The upper end of the elastic element 16 is pressed against the mounting plate 17. When the equipment is affected by temperature changes, bolt thermal expansion and contraction, and slight vibration of the valve body 1 during operation, the elastic element 16 can automatically elastically compensate for the compression gap, so as to avoid the seal loosening and steam leakage under high temperature conditions.

[0039] The flange sealing structure 14 has a positioning ring 18 inside, and the sealing element is limited and assembled inside the positioning ring 18.

[0040] In operation, the inlet gas end 3 on one side of the valve body 1 is first connected to the unit's steam supply header, and the outlet gas end 4 is connected to the turbine shaft seal system. High-temperature steam enters the valve body 1 through the inlet gas end 3 and flows into the inner cavity of the fixedly assembled adjusting cylinder 12. The inlet gas end 3 and the outlet gas end 4 are respectively connected to the inner cavity of the adjusting cylinder 12. All supplied steam must flow and be pressure regulated through the throttling orifice 13 in the middle of the adjusting cylinder 12. At the same time, the outlet gas end 4 is connected to the pressure chamber 6 above the diaphragm 501 inside the top actuator 2 through the external pressure tap 11, so as to collect the actual working pressure of the shaft seal after the valve in real time and feed it back to the double-layer diaphragm assembly 5.

[0041] During normal steady-state operation of the equipment, the upper cover plate 201 and lower cover plate 202 of the top actuator 2 clamp and limit the double-layer diaphragm assembly 5, with the outer edge of the double-layer diaphragm assembly 5 exposed to contact atmospheric pressure air. The heat insulation interlayer 7 between the upper diaphragm 501 and the lower diaphragm 502 is filled with high-temperature heat-insulating filler, which can effectively block the downward conduction of high-temperature heat from the pressure chamber 6 side, completely avoiding creep, elasticity attenuation, and jamming failures of the lower spring assembly 8 due to high temperature. At the same time, the lower diaphragm 502 completely isolates the cavity where the spring assembly 8 is located from the high-temperature steam, keeping the spring assembly 8 in a dry and normal temperature environment, and preventing spring corrosion, salt accumulation, and scaling problems. At this time, the downward pressure of the medium in the pressure chamber 6 is balanced by the upward pre-tightening force provided by the spring assembly 8 through the circumferentially distributed springs and the extrusion plate 801. The double-layer diaphragm assembly 5, valve stem 9 and valve core 10 remain stationary and fixed. The valve core 10 stably blocks the fixed area of ​​the flow hole 13 of the adjusting cylinder 12, and the flow rate of the channel is constant, thereby continuously outputting stable pressure sealing steam to the turbine shaft sealing system.

[0042] When changes in unit operating conditions cause the steam supply pressure to rise after the valve shaft seal and exceed the set threshold, high-pressure steam after the valve rapidly flows into the pressure chamber 6 through the pressure tap 11, increasing the internal pressure of the pressure chamber 6 and generating a uniform downward thrust on the upper diaphragm 501. Relying on the structural characteristics of the double-layer diaphragm assembly 5, which has a fixed outer edge and a movable center, the entire double-layer diaphragm assembly 5 is pushed vertically downward, simultaneously causing the rigidly connected valve stem 9 and the bottom valve core 10 to move smoothly downward. The downward-moving valve core 10 gradually blocks the throttling orifice 13 in the middle of the adjusting cylinder 12, continuously reducing the effective steam flow area, decreasing the steam supply flow from the inlet end 3 of the valve to the after-valve shaft seal, reducing the amount of steam accumulation in the shaft seal system, and causing the excessively high after-valve pressure to gradually decrease until the medium pressure in the pressure chamber 6 and the spring preload force reach a force balance again, automatically completing the overpressure stabilization regulation. Multiple sets of circumferentially distributed springs evenly distribute the load throughout the process, effectively preventing diaphragm skew and ensuring regulation accuracy.

[0043] When the unit load decreases and the steam supply pressure of the downstream shaft seal falls below the set threshold, the pressure of the medium inside the pressure chamber 6 decreases accordingly, significantly reducing the downward thrust on the upper diaphragm 501. At this time, the pre-tightening force of the bottom spring assembly 8 overcomes the medium pressure, pushing the compression plate 801 and the lower diaphragm 502 upward, driving the double-layer diaphragm assembly 5, valve stem 9, and valve core 10 to accurately reset upward as a whole. The valve core 10 gradually releases the obstruction of the throttling orifice 13, continuously increasing the steam flow area, increasing the upstream steam supply flow, replenishing the shaft seal system with sufficient sealing steam, and rapidly raising the low downstream pressure until the dynamic balance between pressure and spring force is achieved again, completing the low-pressure replenishment and stabilization regulation.

[0044] During the entire reciprocating pressure regulation process of the equipment, the outer edge of the double-layer diaphragm assembly 5 is continuously in contact with atmospheric pressure air. If a small amount of steam leaks from the insulation jacket 7, the medium can be naturally dissipated and depressurized through the edge of the diaphragm, preventing the medium from accumulating inside the jacket and causing the diaphragm to bulge or break, thus significantly extending the service life of the diaphragm. At the same time, the flange sealing structure 14 between the upper end of the valve body 1 and the top actuator 2 forms an elastic compression seal through the elastic element 16 in the through groove 15, the sealing element and the mounting plate 17, and together with the sealing element limited and fixed by the positioning ring 18, it forms a double-layer composite sealing structure, which can compensate for the thermal expansion and contraction of the equipment under high temperature conditions in real time and prevent steam leakage at the joint surface.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A mechanical throttling mechanism for regulating steam supply pressure of a steam turbine shaft seal, comprising a valve body (1) and a valve stem (9), characterized in that: The valve body (1) is provided with a top actuator (2) at the upper end. One side of the valve body (1) is the inlet end (3) and the other side is the outlet end (4). The top actuator (2) is provided with a double-layer diaphragm assembly (5), which includes an upper diaphragm (501) and a lower diaphragm (502), both of which are located in the middle of the top actuator (2) and their outer edges are in contact with atmospheric pressure air; A pressure chamber (6) is formed above the upper diaphragm (501), and a heat insulation interlayer (7) filled with heat insulation filler is provided between the upper diaphragm (501) and the lower diaphragm (502). A spring assembly (8) is arranged below the lower diaphragm (502), and the spring assembly (8) is isolated from the high-temperature steam medium. The valve stem (9) is rigidly connected to the double-layer diaphragm assembly (5). The bottom end of the valve stem (9) is provided with an integrally formed valve core (10). When the pressure at the outlet end (4) after the valve changes, the double-layer diaphragm assembly (5) and the valve stem (9) are linked to adjust the size of the air inlet channel entering the shaft seal synchronously.

2. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 1, characterized in that: The heat insulation interlayer (7) is filled with high-temperature heat insulation filler to block the high temperature from being conducted downward to the spring assembly (8).

3. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 1, characterized in that: The spring assembly (8) includes a compression plate (801), and the bottom surface of the compression plate (801) is provided with a plurality of springs, which are distributed in a circular pattern.

4. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 1, characterized in that: The top actuator (2) includes an upper cover plate (201) and a lower cover plate (202), and the double-layer diaphragm assembly (5) is located between the upper cover plate (201) and the lower cover plate (202).

5. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 1, characterized in that: The pressure chamber (6) is connected to an external pressure tapping pipe (11), and the pressure tapping pipe (11) is connected to the outlet end (4) of the valve body (1).

6. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 1, characterized in that: The valve body (1) is provided with an adjusting cylinder (12) inside, the valve core (10) is located inside the adjusting cylinder (12), and the adjusting cylinder (12) is provided with a throttling flow hole (13) in the middle.

7. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 6, characterized in that: The end of the valve inlet (3) near the adjusting cylinder (12) is connected to the adjusting cylinder (12); the end of the valve outlet (4) adjacent to the valve inlet (3) is connected to the adjusting cylinder (12).

8. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 1, characterized in that: A flange sealing structure (14) is provided between the lower end of the top actuator (2) and the upper end of the valve body (1) for sealing the connection.

9. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 8, characterized in that: The flange sealing structure (14) has a through groove (15) at its upper end. The through groove (15) contains an elastic element (16) and several sealing elements. The elastic element (16) has an mounting plate (17) at its upper end.

10. The mechanical throttling mechanism for regulating steam supply pressure of turbine shaft seal according to claim 8, characterized in that: The flange sealing structure (14) has a positioning ring (18) inside, and the sealing element is limited and assembled inside the positioning ring (18).

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