A method and apparatus for controlling the water level of a steam generator

Abstract

This application relates to a method and apparatus for controlling the water level of a steam generator, comprising: calculating a false water level height of the steam generator based on acquired water flow parameters and steam flow parameters; filtering the false water level height to obtain the true water level height of the steam generator; and controlling the water supply flow rate of the steam generator according to the true water level height to maintain the water level of the steam generator at a predetermined value. The method involves calculating the vapor phase volume below the liquid surface based on the water level change caused by the change in the volume of air bubbles below the liquid surface, and then calculating the false water level height. Because the false water level height can be obtained and the false water level band can be filtered to obtain the true water level band, the method avoids operational errors in the water supply rate caused by false water level readings, ensuring accurate water supply and preventing the steam generator from stopping operation due to excessive or insufficient water.

Description

Technical Field

[0001] This application relates to the field of water level control, and more particularly to a water level control method and apparatus for a steam generator. Background Technology

[0002] Water level control in steam generators is crucial for precise water level control in power plants and ships. The control of water level reflects the dynamic balance between feedwater flow and evaporation. When the steam generator load increases suddenly, the steam flow rate increases, the pressure decreases, and the water level rises rapidly. The controller detects this rise and reduces the feedwater flow rate to maintain the water level. However, as the steam flow rate increases again, the feedwater flow rate needs to be increased to maintain the water level. Conversely, when the steam generator load decreases suddenly, the pressure increases, and the water level drops rapidly. During these periods of sudden load increases or decreases, air bubbles can form in the water level. These bubbles, constantly changing with the water level, can cause false water level readings, leading to erroneous feedwater flow control and ultimately affecting the operation of the steam generator. Summary of the Invention

[0003] This application provides a water level control method and apparatus for a steam generator to solve the problem that bubbles are generated in the water level of the steam generator, and the bubbles affect the water level change as the water level changes continuously, which can easily lead to false water level readings and affect the operation of the steam generator.

[0004] In a first aspect, this application provides a water level control method for a steam generator, the method comprising:

[0005] Step S1: Calculate the false water level height of the steam generator based on the obtained water flow rate parameters and steam flow rate parameters, wherein the water flow rate parameter is the water flow rate compensated by the steam generator, and the steam flow rate parameter is the steam flow rate evaporated by the steam generator;

[0006] Step S2: Filter out the false water level height to obtain the true water level height of the steam generator;

[0007] Step S3: Control the water supply flow rate of the steam generator according to the actual water level of the steam generator so that the water level of the steam generator is maintained at a predetermined value;

[0008] Step S1 includes: obtaining the vapor phase volume below the liquid surface based on the water level change caused by the change in the volume of bubbles below the liquid surface in the steam generator, and then calculating the false water level height, which is obtained by the following formula:

[0009]

[0010]

[0011] Where H' is the false water level height, H'(s) is the empirical transfer function, and G... fw (s) represents the change in water flow rate over time, G s (s) represents the change in outlet steam flow rate over time, where s is the expression for the transfer function, and G fw (s)-G s (s) represents the change in feedwater flow rate and / or steam flow rate, a and b are experimental parameters of the steam generator, F is the cross-sectional area of ​​the water chamber of the steam generator, and V″ x Where F is the volume of the vapor phase below the liquid surface, and F is the cross-sectional area of ​​the water chamber in the steam generator. The change in water level caused by the change in the volume of air bubbles below the liquid surface over time is called the false water level height.

[0012] Optionally, step S1 includes:

[0013] Obtain the liquid phase volume and the vapor phase volume, wherein the vapor phase volume includes the vapor phase volume above the liquid surface and the vapor phase volume below the liquid surface;

[0014] The total false water level height is obtained by summing the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume, wherein the total false water level height includes the false water level height, as shown in the following formula:

[0015]

[0016] Among them, G fw For water supply flow rate, G s V' is the steam flow rate, V″ is the liquid volume in the steam generator, and V″ is the liquid volume in the steam generator. x Let P be the vapor volume below the liquid surface, ρ' be the saturated water density, ρ” be the saturated vapor density, and L be the total dummy water level height.

[0017] Optionally, in step S1, calculating the sum of the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume to obtain the total false water level height includes:

[0018] The changes in feedwater flow rate and steam flow rate are calculated using the following formula to confirm the balance between the feedwater and water consumption of the steam generator:

[0019]

[0020] Among them, G fw For water supply flow rate, G sV' is the steam flow rate, ρ' is the saturated water density, ρ” is the saturated steam density, and V″ is the steam density. s Vv is the volume of the vapor phase above the liquid surface. x "Vacuum volume below the liquid surface, Vv" s V″ x That is, the vapor phase volume.

[0021] Optionally, step S1 is followed by:

[0022] The change in water level of the steam generator over time is calculated based on the water flow rate parameter, the steam flow rate parameter, the vapor phase volume, the dummy water level height, and the total dummy water level height, so as to determine the fluctuation of the water level height of the steam generator within a preset time period.

[0023] Secondly, this application also provides a water level control device for a steam generator, comprising:

[0024] The simulation calculation unit is used to calculate the false water level height of the steam generator based on the acquired water flow parameters and steam flow parameters, wherein the water flow parameters are the feed water flow rate consumed by the steam generator to compensate for the loss, and the steam flow parameters are the steam flow rate evaporated by the steam generator.

[0025] A filter is used to filter out the false water level height to obtain the true water level height of the steam generator;

[0026] A water level controller is used to control the water supply flow of the steam generator according to the actual water level of the steam generator, so as to keep the water level of the steam generator at a predetermined value.

[0027] The simulation calculation unit is used to perform the following operations: Based on the change in water level caused by the change in the volume of bubbles below the liquid surface in the steam generator, the volume of the vapor phase below the liquid surface is obtained, and then the false water level height is calculated using the following formula:

[0028]

[0029]

[0030] Where H' is the false water level height, H'(s) is the empirical transfer function, and G... fw (s) represents the change in water flow rate over time, G s (s) represents the change in outlet steam flow rate over time, where s is the expression for the transfer function, and G fw (s)-G s(s) represents the change in feedwater flow rate and / or steam flow rate, a and b are experimental parameters of the steam generator, F is the cross-sectional area of ​​the water chamber of the steam generator, and V″ x The volume of the vapor phase below the liquid surface. The change in water level caused by the change in the volume of air bubbles below the liquid surface over time is called the false water level height.

[0031] Optionally, the simulation calculation unit is also used to obtain the liquid phase volume and the vapor phase volume, wherein the vapor phase volume includes the vapor phase volume above the liquid surface and the vapor phase volume below the liquid surface;

[0032] The total false water level height is obtained by summing the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume, wherein the total false water level height includes the false water level height, as shown in the following formula:

[0033]

[0034] Among them, G fw For water supply flow rate, G s V' is the steam flow rate, V″ is the liquid volume in the steam generator, and V″ is the liquid volume in the steam generator. x Let P be the vapor volume below the liquid surface, ρ' be the saturated water density, ρ” be the saturated vapor density, and L be the total dummy water level height.

[0035] Optionally, in the simulation calculation unit, calculating the sum of the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume to obtain the total false water level height includes:

[0036] The changes in feedwater flow rate and steam flow rate are calculated using the following formula to confirm the balance between the feedwater and water consumption of the steam generator:

[0037]

[0038] Among them, G fw For water supply flow rate, G s V' is the steam flow rate, ρ' is the saturated water density, ρ” is the saturated steam density, and V″ is the steam density. s V″ is the volume of the vapor phase above the liquid surface. x V″ is the volume of the vapor phase below the liquid surface. s +V″ x That is, the vapor phase volume.

[0039] Optionally, the simulation calculation unit is further used for:

[0040] The change in water level of the steam generator over time is calculated based on the water flow rate parameter, the steam flow rate parameter, the vapor phase volume, the dummy water level height, and the total dummy water level height, so as to determine the fluctuation of the water level height of the steam generator within a preset time period.

[0041] This application calculates the false water level height of the steam generator based on the obtained water flow rate and steam flow rate parameters. The water flow rate parameter represents the feedwater flow rate compensated by the steam generator, and the steam flow rate parameter represents the steam flow rate evaporated by the steam generator. The false water level height is filtered to obtain the true water level height of the steam generator. The feedwater flow rate of the steam generator is controlled according to the true water level height to maintain the water level at a predetermined value. The vapor phase volume below the liquid surface is obtained based on the water level change caused by the change in the volume of bubbles below the liquid surface, and the false water level height is then calculated. Because the false water level height can be obtained and the false water level band can be filtered to obtain the true water level band, the control's operation error in water supply caused by false water level is avoided. This ensures accurate water supply, preventing the steam generator from stopping operation due to excessive or insufficient water. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating a water level control method for a steam generator provided in an embodiment of this application. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] like Figure 1 As shown, this application provides a water level control method for a steam generator, the method comprising:

[0047] Step S1: Calculate the false water level height of the steam generator based on the obtained water flow rate parameters and steam flow rate parameters, wherein the water flow rate parameter is the water flow rate compensated by the steam generator, and the steam flow rate parameter is the steam flow rate evaporated by the steam generator.

[0048] In this embodiment, when the load on the steam generator increases or decreases, the water level in the steam generator changes due to the generation of bubbles, resulting in a false water level. The false water level can be calculated by obtaining the water flow rate parameters and steam flow rate parameters. By removing the false water level, the interference of the false water level is avoided, allowing the steam generator to operate normally.

[0049] Step S2: Filter the false water level to obtain the true water level of the steam generator. Specifically, the false water level can be filtered out to obtain the true water level. The true water level of the steam generator is then fed back to the control terminal controlling the water output, achieving accurate water supply to the steam generator and avoiding interference from false water level readings that could cause the steam generator to malfunction.

[0050] Step S3: Control the water supply flow rate of the steam generator according to the actual water level height of the steam generator to maintain the water level of the steam generator at a predetermined value. Because false water level heights can be filtered out to obtain the true water level height, operational errors in the water supply rate caused by false water level readings are avoided, ensuring accurate water supply and preventing the steam generator from stopping operation due to excessive or insufficient water.

[0051] Step S1 includes: obtaining the vapor phase volume below the liquid surface based on the water level change caused by the change in the volume of bubbles below the liquid surface in the steam generator, and then calculating the false water level height, which is obtained by the following formula:

[0052]

[0053]

[0054] Where H' is the spurious water level height, H'(s) is the empirical transfer function, and G... fw (s) represents the change in water flow rate over time, G s (s) represents the change in outlet steam flow rate over time, where s is the expression for the transfer function, and G fw (s)-G s(s) represents the change in feedwater flow rate and / or steam flow rate, a and b are experimental parameters of the steam generator, F is the cross-sectional area of ​​the water chamber of the steam generator, and V″ x The volume of the vapor phase below the liquid surface. The illusory water level height refers to the change in water level caused by the volume of air bubbles below the liquid surface over time. Determining the values ​​of a and b in the transfer function using experimental data not only simplifies the solution to the transfer function but also accurately reflects the changes in the illusory water level height of the steam generator under varying operating conditions, enabling precise control and normal operation of the steam generator's water level height.

[0055] Optionally, step S1 includes:

[0056] Obtain the liquid phase volume and the vapor phase volume, wherein the vapor phase volume includes the vapor phase volume above the liquid surface and the vapor phase volume below the liquid surface;

[0057] The total false water level height is obtained by summing the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume, wherein the total false water level height includes the false water level height, as shown in the following formula:

[0058]

[0059] Among them, G fw For water supply flow rate, G s V' is the steam flow rate, V″ is the liquid volume in the steam generator, and V″ is the liquid volume in the steam generator. x Let be the vapor volume below the liquid surface, P be the saturated pressure, ρ' be the saturated water density, ρ” be the saturated vapor density, and L be the total illusory water level height. It should be noted that in the formula... The change in water level caused by the change in the volume of air bubbles below the liquid surface is also known as the false water level height. As can be seen from the above formula, the influence of the change in water level height is not only related to the air bubbles in the water, but also to parameters such as the pressure inside the steam generator.

[0060] Optionally, in step S1, calculating the sum of the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume to obtain the total false water level height includes:

[0061] The changes in feedwater flow rate and steam flow rate are calculated using the following formula to confirm the balance between the feedwater and water consumption of the steam generator:

[0062]

[0063] Furthermore, before confirming the balance between the water supply and water consumption of the steam generator, the following formula is included:

[0064]

[0065]

[0066]

[0067] The changes in water supply flow rate and steam flow rate are obtained by combining the above formulas, i.e.:

[0068]

[0069] Among them, G fw For water supply flow rate, G s V' is the steam flow rate, ρ' is the saturated water density, ρ” is the saturated steam density, and V″ is the steam density. s V″ is the volume of the vapor phase above the liquid surface. x V″ is the volume of the vapor phase below the liquid surface. s +V″ x That is, the vapor phase volume.

[0070] Optionally, step S1 is followed by:

[0071] The change in water level of the steam generator over time is calculated based on the feedwater flow rate parameters, the steam flow rate parameters, the vapor phase volume, the dummy water level height, and the total dummy water level height to determine the fluctuation of the water level height of the steam generator within a preset time period. Specifically, it is calculated using the following formula:

[0072] V = V” + V’ (1-1)

[0073] V”=V s +V x (1-2)

[0074] Based on the above formula, the changes in water flow rate and steam flow rate are obtained:

[0075]

[0076]

[0077] Based on the above formula, the energy of the feedwater flow rate and steam flow rate during steam generator heating can be obtained:

[0078]

[0079]

[0080] According to equation (1-1), the changes in liquid phase volume and vapor phase volume over time are obtained:

[0081]

[0082] According to equations (1-1) to (1-3) and (1-7), we get:

[0083]

[0084]

[0085] From equations (1-5) to (1-7), we get:

[0086]

[0087] Since the enthalpy and density of saturated water and saturated steam in a steam generator are all single-valued functions of pressure, we have:

[0088]

[0089] Substituting equation (1-8) into equation (1-9) yields the change in steam generator pressure over time:

[0090]

[0091] Based on the illusory water level height, the total illusory water level height, and equations (1-10), (1-18), and (1-19), the change in water level of the steam generator under variable operating conditions over time is obtained, i.e.:

[0092]

[0093] Among them, h fw Here, h' is the feedwater specific enthalpy, h” is the saturated water specific enthalpy, h” is the saturated steam specific enthalpy, Q is the heating quantity, P is the saturated pressure, and k is the unit conversion factor. By observing the change in water level in the steam generator over time, the overall water level variation during operation can be visually represented. By observing the water level variation in each time period, it's possible to determine if the water level fluctuations are consistent. If not, it indicates a false water level situation, allowing for rapid intervention and thus improving the operating efficiency of the steam generator.

[0094] This application also provides a water level control device for a steam generator, comprising:

[0095] The simulation calculation unit is used to calculate the false water level height of the steam generator based on the acquired water flow parameters and steam flow parameters, wherein the water flow parameters are the feed water flow rate consumed by the steam generator to compensate for the loss, and the steam flow parameters are the steam flow rate evaporated by the steam generator.

[0096] A filter is used to filter out the false water level height to obtain the true water level height of the steam generator;

[0097] A water level controller is used to control the water supply flow of the steam generator according to the actual water level of the steam generator, so as to keep the water level of the steam generator at a predetermined value.

[0098] The simulation calculation unit is used to perform the following operations: Based on the change in water level caused by the change in the volume of bubbles below the liquid surface in the steam generator, the volume of the vapor phase below the liquid surface is obtained, and then the false water level height is calculated using the following formula:

[0099]

[0100]

[0101] Where H' is the false water level height, H'(s) is the empirical transfer function, and G... fw (s) represents the change in water flow rate over time, G s (s) represents the change in outlet steam flow rate over time, where s is the expression for the transfer function, and G fw (s)-G s (s) represents the change in feedwater flow rate and / or steam flow rate, a and b are experimental parameters of the steam generator, F is the cross-sectional area of ​​the water chamber of the steam generator, and V” x The volume of the vapor phase below the liquid surface. The change in water level caused by the change in the volume of air bubbles below the liquid surface over time is called the false water level height.

[0102] Optionally, the simulation calculation unit is also used to obtain the liquid phase volume and the vapor phase volume, wherein the vapor phase volume includes the vapor phase volume above the liquid surface and the vapor phase volume below the liquid surface;

[0103] The total false water level height is obtained by summing the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume, wherein the total false water level height includes the false water level height, as shown in the following formula:

[0104]

[0105] Among them, G fw For water supply flow rate, G S V' is the steam flow rate, V″ is the liquid volume in the steam generator, and V″ is the liquid volume in the steam generator. x V' is the vapor volume below the liquid surface, P is the saturated pressure, ρ' is the saturated water density, ρ” is the saturated vapor density, and V″ is the vapor volume below the liquid surface. s V″ represents the vapor volume above the liquid surface, L represents the total illusory water level height, and V″ represents the total illusory water level height. s +V″ x That is, the vapor phase volume.

[0106] Optionally, in the simulation calculation unit, calculating the sum of the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume to obtain the total false water level height includes:

[0107] The changes in feedwater flow rate and steam flow rate are calculated using the following formula to confirm the balance between the feedwater and water consumption of the steam generator:

[0108]

[0109] Among them, G fw For water supply flow rate, G s V' is the steam flow rate, ρ' is the saturated water density, ρ” is the saturated steam density, and V″ is the steam density. s V″ is the volume of the vapor phase above the liquid surface. x V″ is the volume of the vapor phase below the liquid surface. s +V″ x That is, the vapor phase volume.

[0110] Optionally, the simulation calculation unit is further used for:

[0111] The change in water level of the steam generator over time is calculated based on the water flow rate parameter, the steam flow rate parameter, the vapor phase volume, the dummy water level height, and the total dummy water level height, so as to determine the fluctuation of the water level height of the steam generator within a preset time period.

[0112] This device works by adjusting the steam generator's outlet steam flow rate when the load changes. The simulation unit generates a false water level reading, which is then filtered out by a filter. The result is transmitted to the water level controller, which controls the steam generator's feedwater flow rate, thus ensuring the water level remains at a predetermined value. The filter is a commercially available product capable of filtering out false water level readings caused by bubbles.

[0113] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0114] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for controlling the water level in a steam generator, characterized in that, The method includes: Step S1: Calculate the false water level height of the steam generator based on the obtained water flow rate parameters and steam flow rate parameters, wherein the water flow rate parameter is the water flow rate compensated by the steam generator, and the steam flow rate parameter is the steam flow rate evaporated by the steam generator; Step S2: Filter out the false water level height to obtain the true water level height of the steam generator; Step S3: Control the water supply flow rate of the steam generator according to the actual water level of the steam generator so that the water level of the steam generator is maintained at a predetermined value; Step S1 includes: obtaining the vapor phase volume below the liquid surface based on the water level change caused by the change in the volume of bubbles below the liquid surface in the steam generator, and then calculating the false water level height, which is obtained by the following formula: Where H' is the false water level height, H'(s) is the empirical transfer function, and G... fw (s) represents the change in water flow rate over time, G s (s) represents the change in outlet steam flow rate over time, where s is the expression for the transfer function, and G fw (s)-G s (s) represents the change in feedwater flow rate and / or steam flow rate, a and b are experimental parameters of the steam generator, F is the cross-sectional area of ​​the water chamber of the steam generator, and V x "This refers to the volume of the vapor phase below the liquid level." The change in water level caused by the change in the volume of air bubbles below the liquid surface over time, i.e., the false water level height; Obtain the liquid phase volume and the vapor phase volume, wherein the vapor phase volume includes the vapor phase volume above the liquid surface and the vapor phase volume below the liquid surface; The total false water level height is obtained by summing the feedwater flow rate parameter, the steam flow rate parameter, and the vapor phase volume, wherein the total false water level height includes the false water level height, as shown in the following formula: Among them, G fw For water supply flow rate, G s V' is the steam flow rate, V″ is the liquid volume in the steam generator, and V″ is the liquid volume in the steam generator. x Let P be the vapor volume below the liquid surface, ρ' be the saturated water density, ρ” be the saturated vapor density, and L be the total illusory water level height. The changes in feedwater flow rate and steam flow rate are calculated using the following formula to confirm the balance between the feedwater and water consumption of the steam generator: Among them, G fw For water supply flow rate, G s V is the steam flow rate, ρ' is the saturated water density, ρ” is the saturated steam density, and V s "V" represents the volume of the vapor phase above the liquid surface. x "V" represents the volume of the vapor phase below the liquid surface. s +V x This refers to the vapor phase volume.

2. The water level control method for a steam generator according to claim 1, characterized in that, Step S1 is followed by: The change in water level of the steam generator over time is calculated based on the water flow rate parameter, the steam flow rate parameter, the vapor phase volume, the dummy water level height, and the total dummy water level height, so as to determine the fluctuation of the water level height of the steam generator within a preset time period.

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