Adjustable water flow low pressure cylinder water injection device and working method thereof

Abstract

The present application belongs to the field of steam turbine, and discloses a low-pressure cylinder water injection device capable of adjusting water injection flow and a working method thereof, aiming at solving the problem of large water injection amount of the conventional low-pressure cylinder water injection system, which is prone to causing rapid cooling of the low-pressure outer cylinder and the steam seal body due to excessively high flow velocity of the nozzle, thereby causing vibration and other problems. The low-pressure cylinder water injection device capable of adjusting water injection flow comprises a water injection adjusting valve, a switching valve, a large-flow pipeline, a small-flow pipeline, a large-flow nozzle, a small-flow nozzle, a pressure transmitter I, a pressure transmitter II and a thermal resistor. By providing stable atomized small-flow water injection when the low-pressure cylinder is started, switched and under low load, accurate control of the low-pressure cylinder water injection in a wide load range can be realized, the exhaust steam temperature is reduced, the temperature of the last-stage and penultimate-stage blades is accurately controlled, and the last-stage cavitation caused by excessively large water injection flow and the fluctuation caused by inaccurate water injection flow control are avoided.

Description

Technical Field

[0001] This invention belongs to the field of steam turbines, specifically relating to a low-pressure cylinder water spraying device with adjustable water spray flow rate and its working method. Background Technology

[0002] During unit startup and low-load operation, the low-pressure module of the condensing steam turbine will experience blow-out and temperature rise. To prevent excessive temperature from endangering the safety of the terminal blades and to prevent excessive expansion of the low-pressure module caused by high temperature from affecting the safety of the condenser, the steam turbine is equipped with a low-pressure cylinder water spray system.

[0003] The supercooled condensate is pumped through nozzles on the guide ring by a condensate pump to cool the exhaust steam. The flow rate is regulated by a spray control valve. The spray volume is designed to ensure sufficient safety under extreme operating conditions. The nozzles exhibit stable atomization within a certain pressure range and are linear with pressure; the flow rate does not increase with further pressure increases. For nozzles of the same model, the difference between the stable atomization starting flow rate and the maximum flow rate is small. Similarly, to meet the maximum safety margin, nozzles with larger flow rates are selected, but the minimum atomization flow rate of these nozzles will also be relatively large. For heating cylinder-cutting units, only a small amount of cooling steam enters the low-pressure cylinder, requiring a smaller cooling spray volume. For deep peak-shaving units, the low-pressure cylinder flow rate is small, and the required cooling spray volume is also small. Because the subcooled water temperature is low under low back pressure, while the low-pressure outer cylinder may have a higher temperature due to forced draft operation, for low-pressure bearing cylinder-set units, a large low-pressure spray volume will rapidly cool both sides of the low-pressure cylinder. At the same time, the condensate will also cool the low-pressure steam seal, resulting in large low-pressure vibration.

[0004] To meet the requirement of adjustable water spray flow over a wide range, a new low-pressure cylinder water spray device is urgently needed. Compared with conventional water spray systems, the maximum water spray volume can meet the requirements of extreme design conditions, while providing stable atomized small-flow water spray during startup, cylinder cut-off, and low load, thereby achieving precise control of water spray flow. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a low-pressure cylinder water spraying device with adjustable water flow rate and its operating method. The purpose is to solve the problems of conventional low-pressure cylinder water spraying systems, which have large water spray volume and high nozzle velocity, resulting in rapid cooling of the low-pressure outer cylinder and steam seal, and vibration. This invention can provide stable atomized low-flow water spray during startup, cylinder cut-off, and low load, and achieve precise control of water spray flow rate.

[0006] To achieve the objective of this invention, the technical solution adopted is as follows: A low-pressure cylinder water spraying device with adjustable water flow rate includes a water spraying regulating valve 1, a switching valve 2, a high-flow pipeline 3, a low-flow pipeline 4, a high-flow nozzle 5, a low-flow nozzle 6, a pressure transmitter I 7, a pressure transmitter II 8, and a thermal resistor 9. Among them, the low-pressure cylinder water spray header is equipped with a water spray regulating valve 1, and the low-pressure cylinder water spray header is divided into two water spray lines after passing through the water spray regulating valve 1. Among them, one of the two water spray pipes is a high-flow pipe 3 and the other is a low-flow pipe 4; the high-flow pipe 3 is equipped with a high-flow nozzle 5 at the end, and the low-flow pipe 4 is equipped with a low-flow nozzle 6 at the end. The low-pressure cylinder water spray header and two water spray lines are connected by a switching valve 2. A pressure transmitter I 7 is installed on the high-flow line 3, and a pressure transmitter II 8 is installed on the low-flow line 4. A thermal resistor 9 is installed on the low-pressure exhaust cylinder.

[0007] The operating method of the low-pressure cylinder water spray device with adjustable water flow rate is as follows: 1. When the steam turbine is running: In order to reduce the blower temperature, open the water spray regulating valve 1 and at the same time adjust the switching valve 2 to switch the water spray to the low flow pipeline 4. Check the pressure transmitter II 8. The pressure feedback value must be greater than the minimum pressure for stable atomization of the low flow nozzle 6. The minimum pressure of this flow nozzle 6 is determined according to the nozzle parameter characteristics and is 0.1MPa. At the same time, monitor the value of the thermal resistance 9 of the low pressure cylinder exhaust temperature measurement.

[0008] 2. When the turbine is running under load and low load: Monitor the value of the thermal resistance 9 of the low-pressure cylinder exhaust temperature measurement. When the value rises, increase the opening of the water spray regulating valve 1 to increase the water spray flow rate, ensuring that the value of the thermal resistance 9 is lower than the exhaust temperature. When the value of the pressure transmitter II 8 reaches the maximum pressure of 1.1 MPa of the small flow nozzle 6, adjust the switching valve 2 to switch the low-pressure cylinder water spray to the large flow pipeline 3. Monitor the value of the pressure transmitter I 7, which is not lower than the minimum pressure of 0.3 MPa for stable atomization of the large flow nozzle 5. Monitor the value of the thermal resistance 9 of the low-pressure cylinder exhaust temperature measurement; the exhaust temperature is 65℃.

[0009] 3. When the unit begins deep peak shaving and load reduction: Open the water spray regulating valve 1, and simultaneously adjust the switching valve 2 to switch the low-pressure cylinder water spray to the small flow pipeline 4. Check the pressure transmitter II 8; the pressure feedback value must be greater than the minimum pressure for stable atomization of the small flow nozzle 6 by 0.1 MPa. When the load depth is large or the blower is large, the value of the thermal resistance 9, which monitors the exhaust temperature of the low-pressure cylinder, will rise and exceed the back pressure saturation temperature. Increase the opening of the water spray regulating valve 1 to increase the water spray flow rate, ensuring that the value of the thermal resistance 9 is lower than the back pressure saturation stability +5℃. When the value of the pressure transmitter II 8 reaches the maximum pressure value of the small flow nozzle 6 (0.3 MPa), adjust the switching valve 2 to switch the low-pressure cylinder water spray to the large flow pipeline 3. At the same time, monitor the value of the pressure transmitter I 7; its value should not be lower than the minimum pressure for stable atomization of the large flow nozzle 5 (0.3 MPa).

[0010] 4. When the unit switches from heating to cylinder-switching operation: Open the water spray regulating valve 1 and simultaneously adjust the switching valve 2 to switch the water spray to the low-flow pipeline 4. Check the pressure transmitter II 8; the pressure feedback value must be greater than the minimum pressure for stable atomization of the low-flow nozzle 6 by 0.1 MPa. When the value of the thermal resistance 9, which measures the exhaust temperature of the low-pressure cylinder, rises, increase the opening of the water spray regulating valve 1 to increase the water spray flow rate, ensuring that the value of the thermal resistance 9 is lower than the exhaust temperature set value. When the value of the pressure transmitter II 8 reaches the maximum pressure value of the low-flow nozzle 6, adjust the switching valve 2 to switch the water spray of the low-pressure cylinder to the high-flow pipeline 3. Simultaneously monitor the value of the pressure transmitter I 7; its value should not be lower than the minimum pressure for stable atomization of the high-flow nozzle 5. If the value of the thermal resistance 9 is still rising, increase the opening of the water spray regulating valve 1 until the value of the thermal resistance 9 is lower than the exhaust temperature set value.

[0011] The above technical solution has the following beneficial effects: 1. This invention can achieve precise control of low-pressure cylinder water injection within a wide load range, reduce exhaust temperature, accurately control the temperature of the last stage and the second-to-last stage blades, avoid cavitation of the last blade caused by excessive water injection flow, and avoid fluctuations caused by inaccurate water injection flow control.

[0012] 2. Pressure transmitter I and pressure transmitter II can be used to identify the operating water spray pipeline. When low-pressure shaft vibration occurs during water spraying, it can be determined that the water spray volume is too large or the atomization effect is poor. Then, the low-pressure water spray can be switched to a small flow nozzle pipeline through the switching valve, which will have a better atomization effect and reduce the cooling of the low-pressure steam seal by the condensate. Attached Figure Description

[0013] Figure 1 A system diagram of a low-pressure cylinder water spray device with adjustable water flow rate; Figure 2 Schematic diagram of the pipeline and nozzle arrangement for a low-pressure cylinder water spray device with a large flow rate adjustment range; In the diagram: 1-Spray regulating valve, 2-Switching valve, 3-High flow pipeline, 4-Low flow pipeline, 5-High flow nozzle, 6-Low flow nozzle, 7-Pressure transmitter I, 8-Pressure transmitter II, 9-Thermal resistance. Detailed Implementation

[0014] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0015] Example 1 A low-pressure cylinder water spraying device with adjustable water flow rate includes a water spraying regulating valve 1, a switching valve 2, a high-flow pipeline 3, a low-flow pipeline 4, a high-flow nozzle 5, a low-flow nozzle 6, a pressure transmitter I 7, a pressure transmitter II 8, and a thermal resistor 9. The low-pressure cylinder water spraying main pipe is equipped with the water spraying regulating valve 1, which then branches into two water spraying pipelines. One pipeline is the high-flow pipeline 3, and the other is the low-flow pipeline 4. The high-flow pipeline 3 ends with a high-flow nozzle 5, and the low-flow pipeline 4 ends with a low-flow nozzle 6. The low-pressure cylinder water spraying main pipe and the two water spraying pipelines are connected by the switching valve 2. The high-flow pipeline 3 is equipped with the pressure transmitter I 7, and the low-flow pipeline 4 is equipped with the pressure transmitter II 8. The thermal resistor 9 is installed on the low-pressure exhaust cylinder.

[0016] Example 2 The working method of the low-pressure cylinder water spray device with adjustable water flow rate is as follows: When the steam turbine is running: In order to reduce the blower temperature, open the water spray regulating valve and adjust the switching valve to switch the water spray to the low flow pipeline. Check the pressure transmitter II. At this time, the pressure feedback value is greater than the minimum pressure of stable atomization of the low flow nozzle by 0.1MPa. At the same time, monitor the value of the thermal resistance of the low-pressure cylinder exhaust temperature measurement.

[0017] Example 3 The operation method of the adjustable water spray flow rate low-pressure cylinder water spray device is as follows: When the turbine is running under load and low load: monitor the value of the thermal resistance of the low-pressure cylinder exhaust temperature measurement. When the value rises, increase the opening of the water spray regulating valve to increase the water spray flow rate. At this time, the value of the thermal resistance is lower than the back pressure saturation temperature +5℃. When the value of pressure transmitter II reaches the maximum pressure of the small flow nozzle (1.1MPa), adjust the switching valve to switch the low-pressure cylinder water spray to the large flow pipeline. Monitor the value of pressure transmitter I. At this time, the value is not lower than the minimum pressure of stable atomization of the large flow nozzle (0.3MPa). Monitor the value of the thermal resistance of the low-pressure cylinder exhaust temperature measurement.

[0018] Example 4 The operating method of the adjustable low-pressure cylinder water spray device is as follows: When the unit begins deep peak shaving and load reduction: Open the water spray regulating valve and simultaneously adjust the switching valve to switch the low-pressure cylinder water spray to the low-flow pipeline. Check the pressure transmitter II. At this time, the pressure feedback value is greater than the minimum pressure for stable atomization of the low-flow nozzle by 0.1MPa. When the load depth is large or the blower is large, the value of the thermal resistance measured by the low-pressure cylinder exhaust temperature measurement rises above the back pressure saturation temperature. Increase the opening of the water spray regulating valve, and the water spray flow increases. At this time, the value of the thermal resistance decreases and falls below the back pressure saturation temperature +5℃. When the value of the pressure transmitter II reaches the maximum pressure value of the low-flow nozzle (0.3MPa), adjust the switching valve to switch the low-pressure cylinder water spray to the high-flow pipeline. At the same time, monitor the value of the pressure transmitter I. At this time, the value is not lower than the minimum pressure for stable atomization of the high-flow nozzle (0.3MPa).

[0019] Example 5 The operating method of the adjustable low-pressure cylinder water spray device is as follows: When the unit switches from heating to cylinder-switching operation: Open the water spray regulating valve and simultaneously adjust the switching valve to switch the water spray to the low-flow pipeline. Check the pressure transmitter II. At this time, the pressure feedback value is greater than the minimum pressure for stable atomization of the low-flow nozzle (0.1 MPa). When the value of the thermal resistance measured by the monitoring low-pressure cylinder exhaust temperature increases, increase the opening of the water spray regulating valve to increase the water spray flow. At this time, the value of the thermal resistance is lower than the exhaust temperature set value. When the value of pressure transmitter II reaches the maximum pressure value of the low-flow nozzle (0.3 MPa), adjust the switching valve to switch the low-pressure cylinder water spray to the high-flow pipeline. Simultaneously monitor the value of pressure transmitter I. Its value is not lower than the minimum pressure for stable atomization of the high-flow nozzle (0.3 MPa). If the value of the thermal resistance is still rising, increase the opening of the water spray regulating valve until the value of the thermal resistance is lower than the exhaust temperature set value. The exhaust temperature set value is less than the saturation temperature corresponding to the exhaust pressure +5℃.

[0020] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A low-pressure cylinder water spraying device with adjustable water flow rate, characterized in that: Including water spray regulating valve (1), switching valve (2), high flow pipeline (3), low flow pipeline (4), high flow nozzle (5), low flow nozzle (6), pressure transmitter I (7), pressure transmitter II (8), and thermal resistor (9); The water spray regulating valve (1) is installed on the water spray main pipe of the low-pressure cylinder. The water spray main pipe of the low-pressure cylinder is divided into two water spray lines after passing through the water spray regulating valve (1). One of the two water spray pipes is a high-flow pipe (3), and the other is a low-flow pipe (4); the high-flow pipe (3) is equipped with a high-flow nozzle (5) at the end, and the low-flow pipe (4) is equipped with a low-flow nozzle (6) at the end. The low-pressure cylinder water spray header and the two water spray lines are connected by a switching valve (2). A pressure transmitter I (7) is installed on the high-flow line (3), and a pressure transmitter II (8) is installed on the low-flow line (4). The thermal resistor (9) is installed on the low-pressure exhaust cylinder.

2. A method for operating a low-pressure cylinder water spray device with adjustable water flow rate as described in claim 1, characterized in that the steps include... include: (1) When the steam turbine is running: In order to reduce the blower temperature, open the water spray regulating valve and adjust the switching valve to switch the water spray to the low flow pipeline. Check the pressure transmitter II. The pressure feedback value must be greater than the minimum pressure of stable atomization of the low flow nozzle by 0.1MPa. At the same time, monitor the value of the thermal resistance of the low pressure cylinder exhaust temperature measurement. (2) When the turbine is running under load and low load: monitor the value of the thermal resistance of the low-pressure cylinder exhaust temperature measurement. When the value rises, increase the opening of the water spray regulating valve and increase the water spray flow to ensure that the value of the thermal resistance is lower than the exhaust temperature. When the value of pressure transmitter II reaches the maximum pressure of the small flow nozzle of 1.1MPa, adjust the switching valve to switch the water spray of the low-pressure cylinder to the large flow pipeline. Monitor the value of pressure transmitter I. Its value is not lower than the minimum pressure of the large flow nozzle for stable atomization of 0.3MPa. Monitor the value of the thermal resistance of the low-pressure cylinder exhaust temperature measurement. (3) When the unit starts deep peak shaving and load reduction: open the water spray regulating valve and adjust the switching valve at the same time to switch the low-pressure cylinder water spray to the small flow pipeline. Check the pressure transmitter II. The pressure feedback value must be greater than the minimum pressure of stable atomization of the small flow nozzle by 0.1MPa. When the load depth is large or the blower is large, the value of the thermal resistance measured by monitoring the exhaust temperature of the low-pressure cylinder will rise and exceed the back pressure saturation temperature. Increase the opening of the water spray regulating valve and increase the water spray flow. Ensure that the value of the thermal resistance is lower than the exhaust temperature +5℃. When the value of the pressure transmitter II reaches the maximum pressure value of the small flow nozzle of 0.3MPa, adjust the switching valve to switch the low-pressure cylinder water spray to the large flow pipeline. At the same time, monitor the value of the pressure transmitter I. Its value is not lower than the minimum pressure of stable atomization of the large flow nozzle of 0.3MPa. (4) When the unit's heating is switched to cylinder-switching operation: open the water spray regulating valve and simultaneously adjust the switching valve to switch the water spray to the low-flow pipeline. Check the pressure transmitter II. The pressure feedback value must be greater than the minimum pressure for stable atomization of the low-flow nozzle by 0.1 MPa. When the value of the thermal resistance measured by the monitoring low-pressure cylinder exhaust temperature rises, increase the opening of the water spray regulating valve to increase the water spray flow rate and ensure that the value of the thermal resistance is lower than the exhaust temperature setting value. When the value of the pressure transmitter II reaches the maximum pressure value of the low-flow nozzle, adjust the switching valve to switch the low-pressure cylinder water spray to the high-flow pipeline. At the same time, monitor the value of the pressure transmitter I. Its value is not lower than the minimum pressure for stable atomization of the high-flow nozzle. If the value of the thermal resistance is still rising, increase the opening of the water spray regulating valve until the value of the thermal resistance is lower than the exhaust temperature setting value.

3. The operating method of the low-pressure cylinder water spraying device with adjustable water flow rate according to claim 2, characterized in that: The exhaust temperature in step (2) is 65°C.

4. The operating method of the low-pressure cylinder water spraying device with adjustable water flow rate according to claim 2, characterized in that: The back pressure saturation temperature mentioned in step (3) is +5℃.

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