Symmetrical double-hole steam turbine exhaust steam suction device

Abstract

The application discloses a symmetric double-hole steam turbine exhaust steam suction device and relates to the technical field of steam turbines. The device comprises a steam turbine exhaust chamber, two suction holes symmetrically arranged on the steam turbine exhaust chamber, a suction pipeline connected to each of the suction holes, an exhaust steam recovery system connected to the end portions of the two suction pipelines, a flow stabilizing mechanism arranged on each of the suction pipelines, and two flow stabilizing mechanisms connected in series. The device adopts the main structure of the existing steam turbine exhaust chamber, does not need large-scale reconstruction, reduces the engineering implementation cost, has the same parameters of the two suction holes, and has the hole center and the axis of the steam turbine exhaust chamber coplanar, so that the circumferential suction force is uniformly symmetrical, the flow field distortion caused by the local suction force is offset, and the secondary flow field distortion caused by the uneven flow distribution is avoided.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, and specifically to a symmetrical double-hole steam turbine exhaust steam extraction device. Background Technology

[0002] A steam turbine, also known as a steam engine, is a rotary steam power unit. High-temperature, high-pressure steam passes through a fixed nozzle, becomes an accelerated airflow, and is then injected onto the blades, causing the rotor, which is equipped with rows of blades, to rotate and perform work. For example, it is used in thermal power units. The maximum heat loss of a thermal power unit is the exhaust steam loss, i.e., the latent heat loss of the waste steam. Fully recovering and utilizing the waste steam from the turbine is a key technological path to reduce unit heat consumption and improve energy efficiency. However, during the waste steam extraction and recovery process, the extraction behavior can easily cause severe vibrations in the last-stage blades of the turbine, seriously affecting their service life and even leading to major safety accidents such as blade breakage, thus limiting the engineering application of waste steam recovery technology.

[0003] In existing technologies, turbine exhaust steam extraction mostly employs a single-point, single-hole extraction method, such as... Figure 1 As shown, this is a single-point, single-hole suction structure. This method has the following prominent technical defects, and these defects are interconnected, collectively exacerbating the vibration risk of the last-stage blades: 1) Flow field distortion induces asynchronous blade vibration: The last stage blade of a steam turbine is in a complex flow field environment with diffusion, swirling, and possible swirling flow separation. Single-point single-hole suction will disrupt the originally axially dominant stable flow field, forming lateral suction force, local low-pressure area, steam backflow, and swirling distortion in the exhaust chamber. Flow field distortion directly leads to uneven distribution of aerodynamic loads along the blade height and circumference of the last stage blade, which can easily induce various vibration modes such as asynchronous blade vibration (NSV), flutter, and forced vibration, becoming a typical risk source for last stage blade failure. 2) Fluctuations in suction volume lead to unstable blade stress: Existing single-hole suction systems lack an effective flow stabilization mechanism, and the suction volume is easily affected by factors such as exhaust steam pressure and recovery system resistance, resulting in fluctuations. Transient fluctuations in suction volume can cause abrupt changes in exhaust steam pressure, back pressure, and axial velocity distribution, which in turn cause synchronous changes in blade aerodynamic stiffness, excitation force amplitude, and phase, thus altering the blade's resonance point and vibration response. This vibration risk is particularly prominent when the unit is operating at low load and under varying conditions. 3) Uneven blade stress caused by single-point strong suction: Single-point single-hole suction is a local strong suction mode, which will lead to extremely uneven circumferential distribution of the flow field in the exhaust chamber; during the rotation of the last stage blade, a sudden load will occur when passing through the suction zone, forming periodic impact excitation. Essentially, the uneven circumferential aerodynamic load leads to uneven blade stress, which in turn increases the alternating stress of the blade, significantly increasing the risk of blade vibration and fatigue fracture. 4) The single-orifice design has inherent contradictions: In order to meet the exhaust steam suction flow requirements, the existing single-orifice suction requires a large-diameter orifice. However, the larger the orifice diameter, the more obvious the steam flow deviation, the stronger the flow field disturbance, and the higher the risk of blade vibration. If the single-orifice diameter is reduced, although the flow field disturbance can be reduced, it will lead to insufficient suction flow and fail to meet the exhaust steam recovery requirements, forming a dilemma of "flow rate and vibration". 5) Low suction efficiency and high energy consumption: The effective flow coefficient of single-hole suction is low. Large-diameter single holes are prone to generating eccentric vortices, which increases suction resistance and causes the actual suction flow rate to be lower than the theoretical flow rate. In order to achieve the preset suction effect, additional energy needs to be consumed to overcome the resistance, which further reduces the economic efficiency of exhaust steam recovery. Summary of the Invention

[0004] The purpose of this invention is to provide a symmetrical double-hole steam turbine exhaust steam extraction device, which solves the technical problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution: A symmetrical dual-hole steam turbine exhaust steam extraction device includes a steam turbine exhaust chamber with two symmetrically arranged extraction holes on the exhaust chamber. Each extraction hole is connected to an extraction pipe, and the ends of the two extraction pipes are connected to an exhaust steam recovery system. Each extraction pipe is equipped with a flow stabilization mechanism, and the two flow stabilization mechanisms are connected in series.

[0006] In a preferred embodiment of the present invention, the flow stabilization mechanism includes a flow sensor, a regulating valve, and a controller. The flow sensor is used to detect the exhaust steam flow rate in the suction pipe, and the controller is used to control the opening degree of the regulating valve. Both the regulating valve and the flow sensor are installed inside the suction pipe.

[0007] In a preferred embodiment of the present invention, the suction pipe is sealed to the corresponding suction hole by a flange, and the flange is a raised face flange.

[0008] As a preferred embodiment of the present invention, the suction pipe is sandblasted and polished.

[0009] As a preferred embodiment of the present invention, the included angle formed by the central axes of the two suction holes is 60°.

[0010] As a preferred embodiment of the present invention, the connection between the suction hole and the turbine exhaust chamber is provided with a rounded corner transition.

[0011] As a preferred embodiment of the present invention, the angle formed by the central axis of the suction hole and the tangent of the turbine exhaust chamber is in the range of 30°~45°.

[0012] As a preferred embodiment of the present invention, the radius of the rounded corner transition is 1 / 8 to 1 / 5 of the diameter of the suction hole.

[0013] As a preferred embodiment of the present invention, the surface roughness Ra of the suction pipe is ≤1.6μm.

[0014] The present invention also provides a waste steam heating fluid circulation system, including the aforementioned exhaust steam suction device, and further including a steam turbine, a waste steam suction isolation valve, a waste steam indirect heat exchanger, a vacuum system, a condenser, a waste steam recovery drain pump, a condenser cooling system, a waste steam condensate tank, a waste steam drain tank level gauge, and a waste steam condensate isolation valve. The steam turbine, steam turbine exhaust chamber, condenser, waste steam condensate tank, waste steam indirect heat exchanger, and vacuum system are connected in sequence. The condenser cooling system is connected to the condenser. The steam turbine exhaust chamber, waste steam suction isolation valve, and waste steam indirect heat exchanger are also connected in sequence.

[0015] Compared with the prior art, the present invention has the following advantages: (1) The present invention adopts the main structure of the existing steam turbine exhaust chamber, which does not require large-scale modification, thus reducing the engineering implementation cost. The two suction holes have the same parameters, and the center of the hole is coplanar with the axis of the steam turbine exhaust chamber, ensuring that the circumferential suction force is uniform and symmetrical, offsetting the flow field distortion caused by the local suction force, and avoiding the secondary distortion of the flow field caused by uneven flow distribution. (2) The present invention uses a controller to preset a fixed suction flow threshold and automatically adjusts the opening of the regulating valve according to the detection signal of the flow sensor, so that the suction flow is maintained within the preset threshold range, thereby fundamentally avoiding the blade vibration and fatigue risks caused by variable suction and pulse suction. Attached Figure Description

[0016] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0017] Figure 1 A schematic diagram of the existing single-hole technology is provided for embodiments of the present invention; Figure 2 A schematic diagram of the symmetrical arrangement of the turbine exhaust chamber and suction port is provided for embodiments of the present invention. Figure 1 ; Figure 3 A schematic diagram of a waste steam heating fluid circulation system is provided for an embodiment of the present invention; Figure 4A schematic diagram of the waste steam collection and stabilization process is provided for embodiments of the present invention; Figure 5 A side view of the turbine exhaust chamber and suction port is provided for embodiments of the present invention; Figure 6 A schematic diagram of the symmetrical arrangement of the turbine exhaust chamber and suction port is provided for embodiments of the present invention. Figure 2 .

[0018] The labels in the diagram represent the following: 1. Steam turbine exhaust chamber; 2. Suction port; 3. Suction pipe; 4. Steam turbine inlet section; 5. Steam turbine; 6. Waste steam collection and stabilization structure; 7. Waste steam suction isolation valve; 8. Waste steam indirect heat exchanger; 9. Vacuum system; 10. Condenser; 11. Waste steam recovery drain pump; 12. Condenser cooling system; 13. Waste steam condensate tank; 14. Waste steam drain tank level gauge; 15. Waste steam condensate isolation valve. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figures 1 to 6 As shown, the present invention provides a symmetrical dual-hole turbine exhaust steam suction device, including a turbine exhaust chamber 1, two suction holes 2 symmetrically arranged on the turbine exhaust chamber 1, each suction hole 2 being connected to a suction pipe 3, the ends of the two suction pipes 3 being connected to an exhaust steam recovery system, each suction pipe 3 being provided with a flow stabilizing mechanism, and the two flow stabilizing mechanisms being connected in series.

[0021] The flow stabilization mechanism includes a flow sensor, a regulating valve, and a controller. The flow sensor is used to detect the exhaust steam flow rate in the suction pipe 3, and the controller is used to control the opening degree of the regulating valve. Both the regulating valve and the flow sensor are installed inside the suction pipe 3.

[0022] The core technical principle of this application lies in "symmetrical distributed suction, stable flow control, and optimized resistance design", specifically: By symmetrically setting two suction holes 2 on the turbine exhaust chamber 1, the specific positions of the two suction holes 2 on the turbine exhaust chamber 1 are circumferentially 180°±30° (considering the obstruction caused by other equipment on site, the angle is set to 180°±30°, preferably circumferentially 180°, that is, the included angle around the circumference is 180°, and they are centrally symmetrical), that is, the two suction holes 2 are centrally symmetrical about the axis of the turbine exhaust chamber 1, and the opening center of the two suction holes 2 is coplanar with the axis of the turbine exhaust chamber 1, the existing single-point single-hole local strong suction mode is transformed into a two-point pair. The dispersed suction mode is so named; the symmetrical layout makes the suction forces of the two suction holes 2 cancel each other out, avoiding the formation of local low-pressure areas and strong swirls, significantly reducing flow field distortion, and making the flow field in the turbine exhaust chamber 1 uniformly distributed in the circumferential direction; during the rotation of the last stage blade, the aerodynamic load distribution along the circumferential direction is balanced, avoiding the impact excitation caused by sudden load changes, thereby effectively suppressing asynchronous vibration, flutter and other vibration forms, reducing blade alternating stress, extending the service life of the last stage blade, effectively reducing the occurrence of major safety accidents such as blade breakage, and ensuring the stable operation of the turbine unit.

[0023] In this embodiment, the parameters of the two suction holes 2 are kept consistent (such as hole diameter, length and opening angle) to ensure that the suction flow rate and resistance characteristics of the two suction holes 2 are consistent, and to avoid secondary distortion of the flow field caused by uneven flow distribution.

[0024] Furthermore, the number of suction holes 2 can be set to 4 or 6, or a multiple of 2.

[0025] In this embodiment, the dimensional design parameters of the suction holes 2 are as follows: the total geometric area of ​​the two suction holes 2 is 95% to 100% of the geometric area of ​​a single suction hole 2 on the existing turbine exhaust chamber 1 under the same suction requirements; the diameter of a single suction hole 2 is 65% to 75% of the diameter of a single hole on the existing turbine exhaust chamber 1. For example, when the diameter of a single suction hole 2 is 1000 mm (geometric area 0.7854 m²), the diameters of both suction holes 2 are designed to be 700 mm, and the total geometric area is 0.7697 m², which is approximately the same as the diameter of a single hole. With an area of ​​98%, it not only ensures the suction flow rate requirement but also significantly reduces the diameter of a single orifice, reducing steam flow disturbance. It also solves the dilemma of "flow rate and vibration": the diameter of a single suction orifice is significantly reduced (to 65% to 75% of that of a single orifice), effectively reducing steam flow deviation and flow field disturbance. At the same time, the total geometric area of ​​the two orifices is close to that of a single orifice. Combined with a high effective flow coefficient, it ensures sufficient suction flow rate and completely solves the technical contradiction of "large-diameter single orifice with large vibration and small-diameter single orifice with insufficient flow rate" in the existing technology, achieving the dual satisfaction of vibration suppression and flow rate requirements.

[0026] Secondly, under the same geometric area, the total flow coefficient of the double-hole layout is greater than that of the single-hole layout. This is because when the orifice area is fixed, dividing a single large orifice into two smaller orifices increases the total orifice circumference, resulting in a more reasonable contact area between the steam flow and the orifice wall. This significantly reduces local resistance and frictional resistance, thereby increasing the effective flow coefficient. For example, the effective flow coefficient of a single orifice with a diameter of Φ1000mm is taken as an empirical value of 0.75, and the effective flow area is 0.589m². The effective flow coefficient of the double-hole layout with a diameter of Φ700mm is taken as an empirical value of 0.90, and the total effective flow area is 0.693m². The actual suction flow rate of the dual-orifice system is approximately 117.6% of that of the single-orifice system, achieving the effect of "small orifice diameter, large flow rate". This reduces flow field disturbance and improves suction efficiency. With a total geometric area slightly smaller than that of a single orifice, the actual suction flow rate is 17% to 20% higher than that of a single orifice (e.g., the actual flow rate of a dual-orifice system with a diameter of 700mm is about 17.6% higher than that of a single orifice with a diameter of 1000mm). It can meet the waste steam recovery flow rate requirements without additional energy consumption, reducing the energy consumption of the suction system, improving the waste steam recovery utilization rate, reducing the heat loss of thermal power units, and significantly improving the economic efficiency of the units.

[0027] The waste steam recovery system is used to transport the extracted waste steam to the waste steam recovery system for reuse. After cooling, the condensate returns to the condenser. This is existing technology, and the technical principle will not be elaborated on here.

[0028] Flow stabilization control principle: The flow stabilization structure is connected in series with the suction pipe 3. The flow stabilization mechanism maintains a constant suction flow rate, so that the back pressure, flow field distribution and blade aerodynamic load of the turbine exhaust chamber 1 are kept stable, avoiding blade vibration caused by transient fluctuations. The fixed flow suction mode eliminates the influence of suction fluctuations on blade aerodynamic stiffness and excitation force, ensuring the stability of the blade resonance point and vibration response. It is especially suitable for low load and variable operating condition scenarios of the unit, further improving the safety of blade operation.

[0029] The flow sensor detects the exhaust steam flow in the suction pipe 3 in real time and transmits the detection signal to the controller. The controller presets a fixed suction flow threshold and automatically adjusts the opening of the regulating valve according to the detection signal of the flow sensor to keep the suction flow within the preset threshold range with a fluctuation range of no more than ±5%. It adopts a stable, continuous, controllable, and small-amplitude adjustment steam extraction mode, which fundamentally avoids the blade vibration and fatigue risks caused by variable suction and pulse suction, and meets the safety steam extraction requirements in engineering.

[0030] This application modifies the existing turbine exhaust chamber 1 structure by adding two symmetrical suction holes 2 around the turbine exhaust chamber 1, along with suction pipes 3 and a flow stabilization mechanism. No large-scale modification of the turbine's main structure is required, making the modification simple and cost-effective. All components utilize mature industrial parts, facilitating processing, installation, and maintenance, and promoting engineering application. Furthermore, the dimensions of the two holes can be flexibly adjusted according to the suction requirements of different units and the dimensions of the turbine exhaust chamber 1, adapting to different capacities and models of thermal power turbines. Simultaneously, the fixed flow control mode is suitable for various operating scenarios, including rated load, low load, and variable operating conditions, demonstrating broad engineering application prospects.

[0031] The suction pipe 3 is sealed to the corresponding suction hole 2 by a flange, and the flange is a raised face flange.

[0032] Welding or other methods can also be used for sealing connections. High-temperature resistant gaskets can be placed at the sealing surface to prevent exhaust gas leakage and ensure the sealing of the suction process.

[0033] The inside of the suction pipe 3 is treated with sandblasting and polishing.

[0034] The inner surface roughness Ra of suction pipe 3 is ≤1.6μm.

[0035] The diameter of the suction pipe 3 is matched with the diameter of the suction hole. The inner wall of the suction pipe 3 is smoothed to reduce friction resistance and improve flow capacity.

[0036] The connection between the suction port 2 and the turbine exhaust chamber 1 is provided with a rounded corner transition.

[0037] The radius of the rounded corner transition is 1 / 8 to 1 / 5 of the diameter of suction hole 2.

[0038] This is used to reduce abrupt changes in steam flow at the orifice, suppress vortex generation, and further reduce flow field disturbance.

[0039] The angle between the central axis of the suction hole 2 and the tangent of the turbine exhaust chamber 1 is in the range of 30°~45°.

[0040] To guide the exhaust steam to flow smoothly along the suction direction, reduce local pressure loss, and improve suction efficiency, the lower part of suction hole 2 can be extended by 2 cm to further enhance this effect.

[0041] The present invention also provides a waste steam heating fluid circulation system, including the above-mentioned exhaust steam suction device, and further including a steam turbine 5, a waste steam suction isolation valve 7, a waste steam indirect heat exchanger 8, a vacuum system 9, a condenser 10, a waste steam recovery drain pump 11, a condenser cooling system 12, a waste steam condensate tank 13, a waste steam drain tank level gauge 14, and a waste steam condensate isolation valve 15. The steam turbine 5, the steam turbine exhaust chamber 1, the condenser 10, the waste steam condensate tank 13, the waste steam indirect heat exchanger 8, and the vacuum system 9 are connected in sequence. The condenser cooling system 12 is connected to the condenser 10, and the steam turbine exhaust chamber 1, the waste steam suction isolation valve 7, and the waste steam indirect heat exchanger 8 are connected in sequence.

[0042] Figure 3 This is a schematic diagram of the exhaust steam heating fluid circulation system, where 4 is the turbine inlet section.

[0043] After the exhaust steam performs work in the turbine inlet section 4 to the turbine 5, it is discharged through the turbine exhaust chamber 1 to the condenser. The heat carried away is carried away by the condenser cooling system 12 in the condenser 10, and the condensate re-enters the thermodynamic cycle. Exhaust steam regeneration involves being drawn in by the vacuum system 9 and then entering the exhaust steam indirect heat exchanger 8 through the exhaust steam suction isolation valve 7 to heat the fluid being heated. The heated fluid flows out through the exhaust steam suction isolation valve 7, and the latent heat of the exhaust steam condenses into water after heat exchange with the fluid, entering the exhaust steam condensate tank 13. When the exhaust steam condensate tank level gauge 14 reaches a high level, the exhaust steam recovery condensate pump 11 automatically starts and sends the water to the condenser 10, where it is recovered by the exhaust steam condensate isolation valve 15.

[0044] Figure 4 To illustrate the process of stabilizing exhaust steam extraction, two suction holes 2 are symmetrically opened at 180° angles on the turbine exhaust chamber 1 to extract exhaust steam. This symmetrical extraction cancels out the flow field deflection, vortices, and pressure distortion caused by the transverse steam flow, thereby avoiding the three main types of turbulence effects: last-stage blade vibration, uneven cylinder stress, and vacuum fluctuations. The two suction holes 2 symmetrically extract exhaust steam, which converges at the exhaust steam collection and stabilization structure 6 before being discharged, achieving the purpose of stabilizing exhaust steam extraction.

[0045] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A symmetrical double-hole steam turbine exhaust steam extraction device, comprising a steam turbine exhaust chamber (1), characterized in that, Two suction holes (2) are symmetrically arranged on the turbine exhaust chamber (1). The included angle formed by the central axes of the two suction holes (2) is 60°. A rounded transition is provided at the connection between the suction hole (2) and the turbine exhaust chamber (1). The radius of the rounded transition is 1 / 8 to 1 / 5 of the diameter of the suction hole (2). The included angle formed by the central axis of the suction hole (2) and the tangent of the turbine exhaust chamber (1) is in the range of 30° to 45°. Each suction hole (2) is connected to a suction pipe (3). The ends of the two suction pipes (3) are connected to a waste steam recovery system. Each suction pipe (3) is provided with a flow stabilizing mechanism, and the two flow stabilizing mechanisms are connected in series.

2. The symmetrical double-hole steam turbine exhaust steam extraction device according to claim 1, characterized in that, The flow stabilization mechanism includes a flow sensor, a regulating valve, and a controller. The flow sensor is used to detect the exhaust steam flow in the suction pipe (3), and the controller is used to control the opening of the regulating valve. Both the regulating valve and the flow sensor are installed in the suction pipe (3).

3. The symmetrical double-hole steam turbine exhaust steam extraction device according to claim 2, characterized in that, The suction pipe (3) is sealed to the corresponding suction hole (2) by a flange, and the flange is a raised face flange.

4. The symmetrical double-hole steam turbine exhaust steam extraction device according to claim 3, characterized in that, The suction pipe (3) is treated with sandblasting and polishing.

5. A symmetrical double-hole steam turbine exhaust steam extraction device according to claim 3, characterized in that, The inner surface roughness Ra of the suction pipe (3) is ≤1.6μm.

6. A waste steam heating fluid circulation system, characterized in that, The exhaust steam suction device according to any one of claims 1-5 further includes a steam turbine (5), an exhaust steam suction isolation valve (7), an exhaust steam indirect heat exchanger (8), a vacuum system (9), a condenser (10), an exhaust steam recovery condensate pump (11), a condenser cooling system (12), an exhaust steam condensate tank (13), an exhaust steam condensate tank level gauge (14), and an exhaust steam condensate isolation valve (15). The steam turbine (5), the steam turbine exhaust chamber (1), the condenser (10), the exhaust steam condensate tank (13), the exhaust steam indirect heat exchanger (8), and the vacuum system (9) are connected in sequence. The condenser cooling system (12) is connected to the condenser (10), and the steam turbine exhaust chamber (1), the exhaust steam suction isolation valve (7), and the exhaust steam indirect heat exchanger (8) are connected in sequence.

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