Low-pressure cylinder micro-output communicating pipe bypass system

Abstract

The invention discloses a low-pressure cylinder micro-output communicating pipe bypass system which comprises a basic bypass and an adjusting bypass which are arranged in parallel. The two ends of the basic bypass are connected to middle and low pressure communicating pipes on the two sides of a fully-sealed heat supply butterfly valve respectively, and a throttling orifice plate is arranged on the basic bypass. The two ends of the adjusting bypass are connected to the middle and low pressure communicating pipes on the two sides of the fully-sealed heat supply butterfly valve respectively, and a flow meter and an adjusting valve are sequentially arranged on the adjusting bypass in the steam flowing direction. Under the micro-output operation condition of the low-pressure cylinder, the fully-sealed heat supply butterfly valve is in a closed state, the throttling orifice plate provides a fixed basic cooling steam flow to the low-pressure cylinder, the adjusting valve conducts adjustment according to a flow signal fed back by the flowmeter, and after the steam flow flowing through the adjusting bypass and the basic cooling steam flow are overlapped, the low-pressure cylinder is subjected to heat supply. And the total cooling steam flow required by the low-pressure cylinder in real time is matched. According to the method, the field arrangement difficulty can be effectively reduced, and the operation safety of the unit after deep peak regulation or heat supply transformation is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of deep peak shaving or heating of steam turbine units in thermal power plants, specifically a low-pressure cylinder low-output connecting pipe bypass system. Background Technology

[0002] Low-pressure cylinder output reduction involves lowering the turbine back pressure to reduce the steam flow into the low-pressure cylinder. Taking a 300MW unit as an example, under rated back pressure, the steam flow into the low-pressure cylinder should be no less than 90-120 t / h. By reducing the unit's back pressure, the steam flow into the low-pressure cylinder can be lower than the rated flow, thus reducing the steam flow into the low-pressure cylinder and achieving deep peak shaving or increased heating capacity.

[0003] When operating at low power, the steam intake of the low-pressure cylinder needs to be adjusted in real time according to the back pressure. If the original connecting pipe butterfly valve is used for adjustment, the flow range is very low compared to the adjustment of the connecting pipe. Therefore, the butterfly valve on the connecting pipe will operate in a very small opening range. Due to the characteristics of the butterfly valve, the adjustability is extremely poor. Therefore, when operating at low power, the connecting pipe butterfly valve generally needs to be fully closed (fully sealed), and a bypass is set up to adjust the flow required by the low-pressure cylinder.

[0004] Conventional bypass cooling piping systems typically involve a large bypass to accommodate the required steam flow during low-output operation. For example, in a 300MW unit, the steam flow rate during low-pressure cylinder operation can range from approximately 55 to 90 t / h. Under low-output conditions, if a conventional bypass design is followed, the piping would be quite large, reaching around DN1000. This presents challenges for on-site layout and results in the bypass cooling steam regulating valve having an excessively large diameter, leading to a small actual operating opening and poor regulating performance. Consequently, it becomes difficult to meet the real-time and effective regulation requirements during low-output operation. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a low-pressure cylinder micro-output connecting pipe bypass system that effectively reduces the difficulty of on-site layout, solves the problem of poor bypass adjustment, and has a simple system configuration.

[0006] The technical objective of this invention is achieved through the following technical solution: A low-pressure cylinder low-output bypass system is provided, comprising a low-pressure and medium-pressure bypass pipe between the intermediate-pressure cylinder and the low-pressure cylinder of a steam turbine. The low-pressure and medium-pressure bypass pipe is equipped with a fully shut-off, fully sealed heating butterfly valve. The system includes a basic bypass and a regulating bypass connected in parallel. The two ends of the basic bypass are connected to the low-pressure and medium-pressure bypass pipes on both sides of the fully sealed heating butterfly valve, and a throttling orifice plate is provided on the basic bypass. The two ends of the regulating bypass are connected to the low-pressure and medium-pressure bypass pipes on both sides of the fully sealed heating butterfly valve, and a flow meter and a regulating valve are sequentially arranged along the steam flow direction on the regulating bypass. Under low-pressure cylinder low-output operation, the fully sealed heating butterfly valve is closed, and the throttling orifice plate provides a fixed basic cooling steam flow rate to the low-pressure cylinder. The regulating valve adjusts according to the flow signal fed back by the flow meter, so that the steam flow rate through the regulating bypass is superimposed with the basic cooling steam flow rate to match the total cooling steam flow rate required by the low-pressure cylinder in real time.

[0007] Preferably, the fixed flow rate provided by the orifice plate is configured as a predetermined value between one-third and one-half of the maximum total flow rate of the bypass system under low-pressure cylinder low-output conditions.

[0008] Preferably, the orifice diameter of the throttling orifice plate is determined based on a supercritical flow model, according to the requirement of providing the predetermined fixed flow rate for the basic bypass.

[0009] Preferably, the design range of the flow regulation capability of the regulating valve is determined based on the design minimum total required flow and design maximum total flow of the bypass system, minus the predetermined fixed flow of the basic bypass.

[0010] Preferably, the regulating valve and the flow meter are an electronic regulating valve and an electronic flow meter, respectively.

[0011] When applied to a steam turbine unit containing two low-pressure cylinders, an independent low-pressure cylinder micro-output bypass system, as described above, is configured for the steam inlet connecting pipe of each low-pressure cylinder.

[0012] A steam turbine unit, characterized in that it includes a low-pressure cylinder micro-output connecting pipe bypass system as described above.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention, by setting up parallel bypasses to handle a fixed portion of the flow, significantly reduces the flow range that the regulating bypass needs to handle, allowing for the selection of smaller diameter, higher-precision regulating valves. The smaller diameter regulating valve operates within its optimized operating range, exhibiting more sensitive opening changes, achieving precise, sensitive, and stable control of the cooling steam flow to the low-pressure cylinder. The reduced bypass pipe diameter lowers pipe specifications and valve dimensions, effectively alleviating the difficulty and cost of on-site layout. Precise flow control directly ensures the minimum cooling steam demand of the low-pressure cylinder under ultra-low load (micro-output), preventing rotor overheating and greatly improving the operational safety of the unit after deep peak shaving or heating system retrofitting. This technical measure effectively reduces on-site layout difficulty and significantly improves the operational safety of the unit after deep peak shaving or heating system retrofitting. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention; Attached reference numerals: 1-Intermediate pressure cylinder of steam turbine, 2-Low pressure cylinder of steam turbine, 3-Flow meter, 4-Regulating valve, 5-Throttle orifice plate, 6-Fully sealed heating butterfly valve, 7-Intermediate and low pressure connecting pipe, 8-Basic bypass, 9-Regulating bypass. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0016] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0017] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0018] Example 1 like Figure 1As shown, a low-pressure cylinder low-output connecting pipe bypass system is provided, which is a medium-low pressure connecting pipe 7 bypass between the medium-pressure cylinder 1 and the low-pressure cylinder 2 of the steam turbine. The medium-low pressure connecting pipe 7 is equipped with a fully shut-off, fully sealed heating butterfly valve 6. The system includes a basic bypass 8 and a regulating bypass 9 arranged in parallel: the two ends of the basic bypass 8 are respectively connected to the medium-low pressure connecting pipes 7 on both sides of the fully sealed heating butterfly valve 6, and a throttling orifice plate 5 is provided on the basic bypass 8; the two ends of the regulating bypass 9 are respectively connected to the medium-low pressure connecting pipes 7 on both sides of the fully sealed heating butterfly valve 6, and a flow meter 3 and a regulating valve 4 are arranged sequentially along the steam flow direction on the regulating bypass 9.

[0019] In the case of low-pressure cylinder operating at low output, the fully sealed heating butterfly valve 6 is in the closed state, and the throttling orifice plate 5 provides a fixed basic cooling steam flow to the low-pressure cylinder 2. The regulating valve 4 is adjusted according to the flow signal fed back by the flow meter 3, so that the steam flow through the regulating bypass 9 is superimposed with the basic cooling steam flow to match the total cooling steam flow required by the low-pressure cylinder 2 in real time.

[0020] By setting up a parallel basic bypass 8 to handle a fixed portion of the flow, the flow range that the regulating bypass 9 needs to handle is significantly reduced, allowing for the selection of a smaller diameter, higher precision regulating valve 4. The smaller diameter regulating valve 4 operates within its optimized operating range, exhibiting more sensitive opening changes, achieving precise, sensitive, and stable control of the cooling steam flow to the low-pressure cylinder. The reduced diameter of the regulating bypass 9 lowers pipe specifications and valve dimensions, effectively alleviating the difficulty and cost of on-site layout. Precise flow control directly ensures the minimum cooling steam demand of the low-pressure cylinder under ultra-low load (low output), preventing rotor overheating and greatly improving the operational safety of the unit after deep peak shaving or heating system retrofitting. This technical measure effectively reduces on-site layout difficulty and significantly improves the operational safety of the unit after deep peak shaving or heating system retrofitting.

[0021] In actual use, the regulating valve 4 and the flow meter 3 are respectively an electronic regulating valve and an electronic flow meter.

[0022] In actual use, the fixed flow rate provided by the orifice plate 5 is configured as a predetermined value between one-third and one-half of the maximum total flow rate of the bypass system under the low-pressure cylinder low-output condition.

[0023] The orifice diameter of the throttling orifice plate 5 is determined by calculation based on a supercritical flow model, according to the requirement of providing a predetermined fixed flow rate for the basic bypass 8.

[0024] The design range of the flow regulation capability of regulating valve 4 is determined based on the design minimum total demand flow and design maximum total flow of the bypass system, minus the predetermined fixed flow of the basic bypass 8.

[0025] The implementation of the present invention will be described using a 300MW-class steam turbine generator set as an example.

[0026] First, the total cooling steam demand under low-pressure cylinder low-output conditions is determined. Based on the variation range of turbine back pressure, the design range of total cooling steam flow rate is determined to be 55 t / h to 90 t / h. Among them, 90 t / h is defined as the maximum design total flow rate of this bypass system, and 55 t / h is defined as the minimum design total demand flow rate.

[0027] Next, we will proceed with traffic allocation and equipment design: Basic bypass design: According to the present invention, the design fixed flow rate of the basic bypass 8 is set to a value between one-third and one-half of the aforementioned maximum total design flow rate (90t / h). In this example, it is selected as 40t / h.

[0028] Orifice plate selection: The orifice plate 5 with a fixed flow rate of 40t / h is provided for the basic bypass 8. Its orifice diameter needs to be calculated and selected based on the characteristics of the steam in the supercritical flow state when the output is low.

[0029] Regulating bypass and regulating valve design: The flow regulation range that regulating bypass 9 needs to handle is determined by deducting the basic fixed flow from the total demand range.

[0030] Its maximum design flow rate is: the maximum total design flow rate is 90t / h minus the basic fixed flow rate of 40t / h, which equals 50t / h.

[0031] The minimum flow rate that needs to be adjusted is: the minimum total design flow rate of 55t / h minus the basic fixed flow rate of 40t / h equals 15t / h.

[0032] Therefore, the regulating valve 4 on the regulating bypass 9 should be selected according to the flow regulation range of 15t / h to 50t / h to cover all variable flow requirements under low output conditions.

[0033] Through the above design, the basic bypass 8 provides stable basic cooling steam, while the regulating bypass 9 is responsible for precise regulation on this basis. The two work together to ensure the safe and efficient operation of the low-pressure cylinder.

[0034] Example 2 When used in a steam turbine unit with two low-pressure cylinders, the bypass system for each low-pressure cylinder can be designed in the same manner.

[0035] When applied to a steam turbine unit containing two low-pressure cylinders 2, an independent low-pressure cylinder micro-output connecting pipe bypass system, as shown in Example 1, is configured for the steam inlet connecting pipe of each low-pressure cylinder 2.

[0036] Example 3 A steam turbine unit includes a low-pressure cylinder micro-output connecting pipe bypass system as in Embodiment 1 or Embodiment 2.

[0037] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A low-pressure cylinder low-output connecting pipe bypass system, comprising a low-pressure connecting pipe (7) bypass between the intermediate-pressure cylinder (1) and the low-pressure cylinder (2) of a steam turbine, wherein the low-pressure connecting pipe (7) is provided with a fully shut-off, fully sealed heating butterfly valve (6); characterized in that, The system includes a basic bypass (8) and a regulating bypass (9) connected in parallel: the two ends of the basic bypass (8) are respectively connected to the medium and low pressure connecting pipes (7) on both sides of the fully sealed heating butterfly valve (6), and a throttling orifice plate (5) is provided on the basic bypass (8); the two ends of the regulating bypass (9) are respectively connected to the medium and low pressure connecting pipes (7) on both sides of the fully sealed heating butterfly valve (6), and a flow meter (3) and a regulating valve (4) are sequentially arranged along the steam flow direction on the regulating bypass (9); wherein, under the low-pressure cylinder low-output operation condition, the fully sealed heating butterfly valve (6) is in the closed state, the throttling orifice plate (5) provides a fixed basic cooling steam flow to the low-pressure cylinder (2), and the regulating valve (4) is adjusted according to the flow signal fed back by the flow meter (3), so that the steam flow through the regulating bypass (9) is superimposed with the basic cooling steam flow to match the total cooling steam flow required by the low-pressure cylinder (2) in real time.

2. The low-pressure cylinder micro-output connecting pipe bypass system according to claim 1, characterized in that, The fixed flow rate provided by the orifice plate (5) is configured to be a predetermined value between one-third and one-half of the maximum total flow rate of the bypass system under the low-pressure cylinder low-output condition.

3. The low-pressure cylinder micro-output connecting pipe bypass system according to claim 2, characterized in that, The orifice diameter of the throttling orifice plate (5) is determined based on a supercritical flow model, according to the requirement of providing the predetermined fixed flow rate for the basic bypass (8).

4. The low-pressure cylinder micro-output connecting pipe bypass system according to claim 2 or 3, characterized in that, The design range of the flow regulation capability of the regulating valve (4) is determined based on the design minimum total demand flow and design maximum total flow of the bypass system, minus the predetermined fixed flow of the basic bypass (8).

5. The low-pressure cylinder micro-output connecting pipe bypass system according to claim 1, characterized in that, The regulating valve and the flow meter are respectively an electronic regulating valve and an electronic flow meter.

6. The low-pressure cylinder micro-output connecting pipe bypass system according to claim 1, characterized in that, When applied to a steam turbine unit containing two low-pressure cylinders (2), a low-pressure cylinder micro-output connecting pipe bypass system as described in any one of claims 1 to 5 is independently configured for the steam inlet connecting pipe of each low-pressure cylinder (2).

7. A steam turbine unit, characterized in that, The system includes a low-pressure cylinder micro-output connecting pipe bypass system as described in any one of claims 1 to 6.

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