A method for improving the safety of steam supply to low-pressure shaft seals

Abstract

The present invention provides a method for improving the safety of low-pressure shaft seal steam supply, which relates to the technical field of thermal power generation, and comprises: real-time acquisition of operating parameters of key components, periodic calculation of steam accumulator pressure values, and analysis of theoretical pressure values ​​of gas supply sources affected thereby; based on the theoretical pressure values ​​of gas supply sources and the pressure loss of each connected device, analyzing low-pressure shaft seal steam supply pressure data, and determining pressure deviation data and pressure deviation change rate at the current moment; calculating an ideal regulating valve opening based on the regulating valve opening of the previous cycle and the pressure deviation data and pressure deviation change rate at the current moment; and controlling the regulating action of the regulating valve according to the ideal regulating valve opening; the present invention collects parameters of multiple parts in real time, considers the operating factors of the steam accumulator, accurately calculates the steam supply pressure, and dynamically adjusts the regulating valve opening, so as to solve the problems of unstable steam supply pressure and untimely response of the regulating valve, and sets a normally open bypass for emergency protection, so as to ensure stable operation of the system.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation technology, and in particular to a method for improving the safety of steam supply to low-pressure shaft seals. Background Technology

[0002] In thermal power generation, the turbine shaft sealing system plays a crucial role. Early shaft sealing systems were relatively simple in design, mainly using basic sealing structures to reduce steam leakage. With the continuous development of power generation technology, the requirements for turbine efficiency and safety have become increasingly stringent, and the shaft sealing system has undergone several improvements. From the initial simple packing seals, it has evolved to later forms such as mechanical seals and labyrinth seals, significantly improving the sealing effect. At the same time, in order to better control the steam supply at the shaft seal, the steam supply system has gradually become more complex and precise. With the development of automation technology and control theory, the shaft seal steam supply system has begun to use advanced sensors and controllers, which can monitor and adjust the steam supply parameters in real time to adapt to different operating conditions.

[0003] However, in existing technologies, the steam supply pressure can be affected by various factors, such as changes in the steam generator load and fluctuations in pipeline resistance, leading to unstable steam supply pressure for the low-pressure shaft seal. This instability affects the sealing effect of the shaft seal, increases steam leakage, and reduces turbine efficiency. Furthermore, due to the insufficiently advanced control algorithms of existing regulating valves and their poor dynamic characteristics, they cannot respond accurately and promptly when the steam supply pressure changes. In extreme cases, such as steam supply source failure or regulating valve malfunction, existing technologies often lack effective emergency measures to ensure the safe steam supply to the low-pressure shaft seal. This can result in excessively high or low temperatures at the shaft seal, damaging the seal equipment and even causing safety accidents.

[0004] Therefore, there is an urgent need in this field for a method to improve the safety of steam supply to low-pressure shaft seals in order to solve the above problems. Summary of the Invention

[0005] This invention provides a method to improve the safety of steam supply to low-pressure shaft seals. By collecting parameters from multiple locations in real time, considering the operating factors of the steam accumulator, accurately calculating the steam supply pressure, and dynamically adjusting the opening of the regulating valve, the method solves the problems of unstable steam supply pressure and untimely response of the regulating valve. A normally open bypass is also set up as an emergency backup to ensure stable system operation.

[0006] This invention provides a method for improving the safety of steam supply to low-pressure shaft seals, comprising the following steps:

[0007] Step 1: Real-time acquisition of operating parameters from the steam accumulator, steam source, main steam pipeline, regulating valve, and shaft seal;

[0008] Step 2: Periodically calculate the pressure value of the steam accumulator and analyze the theoretical pressure value of the gas supply source affected by the steam accumulator pressure value.

[0009] Step 3: Analyze the low-pressure shaft seal steam supply pressure data based on the theoretical pressure value of the gas supply source and the pressure loss of each connected device;

[0010] Step 4: Analyze the pressure deviation data and pressure deviation change rate at the current moment based on the low-pressure shaft seal steam supply pressure data under continuous cycle.

[0011] Step 5: Calculate the ideal control valve opening based on the control valve opening of the previous cycle and the pressure deviation data and pressure deviation change rate at the current moment;

[0012] Step 6: Control the regulating valve's regulating action according to the ideal regulating valve opening.

[0013] According to a method for improving the steam supply safety of low-pressure shaft seals provided by the present invention, in step one, the operating parameters include:

[0014] The data collected includes the initial pressure, inlet and outlet steam flow rate, and accumulator capacity of the steam accumulator; the initial pressure of the gas supply source; the current steam flow rate and pipe diameter of the main steam supply pipeline; the current steam flow rate, flow velocity, and current opening of the regulating valve; the current steam flow rate and pressure under standard conditions at the shaft seal; and the fluid density and fluid dynamic viscosity.

[0015] According to a method for improving the safety of steam supply to low-pressure shaft seals provided by the present invention, the process of periodically calculating the pressure value of the steam accumulator and analyzing the theoretical pressure value of the gas supply source affected by the steam accumulator pressure value includes:

[0016] A pre-set periodic time limit t is established, and a steam accumulator pressure simulation model is built based on the initial pressure and capacity of the steam accumulator and the current steam flow rate at the inlet and outlet.

[0017]

[0018] Among them, P st (t) represents the current steam accumulator pressure value, P st0 C is the initial pressure of the steam accumulator. st Q is a capacity factor determined based on the steam accumulator's capacity, reflecting the accumulator's ability to store and release steam. It is determined according to industry standards corresponding to the steam accumulator's capacity. in (t) and Q out (t) represents the inlet and outlet steam flow rates of the steam accumulator, respectively, and t is the period time.

[0019] The current steam accumulator pressure value P is obtained through calculation. st (t);

[0020] Further based on model P suadj (t)=P su +α*P st (t) Adjust the theoretical pressure value of the gas supply source;

[0021] Among them, P suadj (t) represents the theoretical pressure value of the gas supply source, P su α is the initial pressure of the gas supply source; α is the supplementary coefficient, which reflects the degree to which the steam accumulator pressure supplements the steam supply source pressure, and is determined through experimental debugging.

[0022] According to the present invention, a method for improving the safety of steam supply to low-pressure shaft seals includes the following process: analyzing the steam supply pressure data of low-pressure shaft seals based on the theoretical pressure value of the air supply source and the pressure loss of each connected device.

[0023] The current pipeline pressure loss, regulating valve pressure loss, and shaft seal pressure loss are determined based on the current fluid flow rate in the main steam supply pipeline, regulating valve, and shaft seal; the calculation formula is as follows:

[0024] ΔP pipe =K pipe *Q sup (t) 2

[0025] ΔP valve =K valve *Q valve (t) 2

[0026] ΔP seal =K seal *Q seal (t) 2

[0027] Wherein, ΔP pipe For pipeline pressure loss, Q valve (t) represents the current steam supply flow rate of the main steam supply pipeline; K pipe ΔP is the pipe resistance coefficient, used to reflect the magnitude of the resistance encountered by fluid flowing in a pipe. Its value is determined experimentally using the Darcy-Weisbach formula. valve To control the pressure loss of the valve, Q valve (t) represents the current steam supply flow rate of the regulating valve; K valve The resistance coefficient of a control valve, ΔP, reflects the resistance encountered by fluid as it passes through the valve and is provided by the valve manufacturer. seal Q represents the shaft seal pressure loss. seal(t) represents the current steam supply flow rate at the shaft seal; K seal This is the resistance coefficient at the shaft seal, used to reflect the magnitude of the resistance encountered by the fluid flowing at the shaft seal. It is calculated in conjunction with the pipeline resistance coefficient K. valve The same principle determines the numerical value;

[0028] Based on model P seal (t)=P suadj (t)-ΔP pipe -ΔP valve -ΔP seal Calculate the current low-pressure shaft seal steam supply pressure data P seal (t).

[0029] According to the present invention, a method for improving the safety of steam supply to low-pressure shaft seals includes the following process: analyzing the pressure deviation data and pressure deviation change rate at the current moment based on the low-pressure shaft seal steam supply pressure data over a continuous period.

[0030] The pressure deviation data E at the current moment is calculated based on the pressure deviation simulation model. p The pressure deviation simulation model is as follows:

[0031]

[0032] Among them, P set P is the pressure of the shaft seal under standard conditions. range The pressure measurement range is determined based on the sensor specifications;

[0033] Obtain the pressure deviation data E at the current moment. p Then, through the model Calculate the rate of change of pressure deviation C at the current moment. Ep Among them, T sample The sampling time is the periodic time limit t.

[0034] According to the present invention, a method for improving the safety of low-pressure shaft seal steam supply includes the following steps: The process of calculating the ideal control valve opening based on the control valve opening of the previous cycle and the pressure deviation data and pressure deviation change rate at the current moment includes:

[0035] A valve opening simulation model is pre-established. The valve opening of the previous cycle and the pressure deviation data and pressure deviation change rate at the current moment are substituted into the valve opening simulation model to calculate the current ideal valve opening U(t).

[0036] The opening simulation model is as follows:

[0037]

[0038] Where U(t-1) is the valve opening in the previous cycle, and Re is the Reynolds number, specifically... ρ is the fluid density, v is the current steam supply velocity of the regulating valve, μ is the fluid dynamic viscosity, and d is the pipe diameter of the main steam supply pipeline; ω1, ω2, and ω3 are all adjustment coefficients. ω1 reflects the degree of influence of pressure deviation on the opening of the regulating valve, determining the proportional relationship between the adjustment range of the regulating valve opening and the pressure deviation at the current moment to eliminate the pressure deviation. It is determined through experimental debugging or theoretical analysis. ω2 reflects the degree of influence of the rate of change of pressure deviation on the opening of the regulating valve. The opening of the regulating valve is adjusted according to the rate of change of pressure deviation to anticipate the trend of system pressure changes. It is determined through dynamic response analysis or parameter optimization. ω3 reflects the influence of the fluid's physical properties, i.e., the Reynolds number, on the opening of the regulating valve. It is determined through fluid characteristic analysis or empirical methods combined with experiments.

[0039] According to the present invention, a method for improving the safety of low-pressure shaft seal steam supply, wherein the process of controlling the regulating action of the regulating valve according to the ideal regulating valve opening includes:

[0040] The PID controller converts the current ideal valve opening U(t) into a command signal and sends it to the front-end controller, which then controls the valve to perform the adjustment action according to the command signal.

[0041] A method for improving the steam supply safety of low-pressure shaft seals according to the present invention further includes:

[0042] A normally open bypass is provided downstream of the regulating valve. The normally open bypass provides a minimum air supply to the low-pressure cylinder to avoid the impact on the system caused by excessive changes in the opening of the regulating valve.

[0043] Compared with the prior art, the beneficial effects of this application are as follows:

[0044] By analyzing the impact of steam accumulator pressure on the gas supply pressure, as well as the pressure loss of each connected device, the low-pressure shaft seal steam supply pressure can be controlled more accurately; the opening of the regulating valve can be dynamically adjusted to quickly stabilize the steam supply pressure near the set value, reduce steam leakage caused by pressure fluctuations, and improve turbine efficiency.

[0045] Based on pressure deviation data and rate of change analysis, the ideal control valve opening is determined and adjusted in conjunction with the opening of the previous cycle, so that the control valve can respond promptly to changes in steam supply pressure; ensuring the continuity and stability of the shaft seal steam supply and guaranteeing the normal operation of the steam turbine;

[0046] The normally open bypass can provide a minimum air supply to the low-pressure cylinder when the regulating valve opening changes too much or malfunctions; it avoids abnormal temperature at the shaft seal, protects the shaft seal equipment, prevents safety accidents, and improves the safety of the entire low-pressure shaft seal steam supply system.

[0047] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0048] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0049] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0050] Figure 1 This is a flowchart illustrating a method for improving the safety of steam supply to low-pressure shaft seals, provided by an embodiment of the present invention. Detailed Implementation

[0051] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0052] Example 1:

[0053] This invention provides a method for improving the safety of steam supply to low-pressure shaft seals. Please refer to [link / reference]. Figure 1 This includes the following steps:

[0054] Step 1: Real-time acquisition of operating parameters from the steam accumulator, steam source, main steam pipeline, regulating valve, and shaft seal;

[0055] Step 2: Periodically calculate the pressure value of the steam accumulator and analyze the theoretical pressure value of the gas supply source affected by the steam accumulator pressure value.

[0056] Step 3: Analyze the low-pressure shaft seal steam supply pressure data based on the theoretical pressure value of the gas supply source and the pressure loss of each connected device;

[0057] Step 4: Analyze the pressure deviation data and pressure deviation change rate at the current moment based on the low-pressure shaft seal steam supply pressure data under continuous cycle.

[0058] Step 5: Calculate the ideal control valve opening based on the control valve opening of the previous cycle and the pressure deviation data and pressure deviation change rate at the current moment;

[0059] Step 6: Control the regulating valve's regulating action according to the ideal regulating valve opening.

[0060] The principle of the above embodiment is as follows: Operating parameters of multiple key components are collected in real time, covering various operating information such as pressure and flow rate of the steam accumulator, air supply source, main steam pipeline, regulating valve, and shaft seal. Using the collected parameters of the steam accumulator, its pressure value is calculated periodically. Since the steam accumulator can buffer and regulate the steam supply, its pressure value is used to analyze the theoretical pressure value of the air supply source, considering the influence of the steam accumulator on the air supply source pressure to stabilize the air supply source pressure. Based on the theoretical pressure value of the air supply source, and combined with the pressure loss of each connected device, the low-pressure shaft seal steam supply pressure data is calculated using corresponding formulas. Pressure deviation and rate of change are calculated based on the low-pressure shaft seal steam supply pressure data under continuous cycles, providing a dynamic basis for adjusting the regulating valve opening and reflecting the deviation and trend of the steam supply pressure from the set value. Based on the regulating valve opening of the previous cycle and the current pressure deviation and rate of change, the ideal regulating valve opening is calculated using the established model. The regulating valve is controlled according to the ideal opening to achieve dynamic adjustment of the steam supply pressure, stabilizing the steam supply pressure near the set value.

[0061] The beneficial effects of the above embodiments are as follows: through the synergistic effect of the above steps, the steam supply pressure can be controlled more precisely; considering the influence of multiple factors on the steam supply pressure, the opening of the regulating valve is dynamically adjusted to make the low-pressure shaft seal steam supply pressure more stable, reduce steam leakage, and improve turbine efficiency; the ideal opening is calculated based on pressure deviation and rate of change and the regulating valve is controlled, so that the regulating valve can respond to changes in steam supply pressure more promptly and accurately, ensuring the continuity and stability of shaft seal steam supply and guaranteeing the normal operation of the turbine; the overall method improves the safety of the low-pressure shaft seal steam supply system through precise control and adjustment of each link; the stable steam supply pressure and timely response regulating valve reduce the risk of system failure and ensure the normal operation and service life of the equipment.

[0062] To further optimize the above embodiments, the operating parameters in step one include:

[0063] The data collected includes the initial pressure, inlet and outlet steam flow rate, and accumulator capacity of the steam accumulator; the initial pressure of the gas supply source; the current steam flow rate and pipe diameter of the main steam supply pipeline; the current steam flow rate, velocity, and current opening of the regulating valve; the current steam flow rate and pressure under standard conditions at the shaft seal; as well as fluid density and fluid dynamic viscosity.

[0064] It should be noted that collecting the initial pressure, inlet and outlet steam flow rates, and accumulator capacity of the steam accumulator is for the purpose of accurately calculating the pressure changes within the accumulator; the initial pressure is the starting point for the calculation, the inlet and outlet steam flow rates reflect the steam inflow and outflow, and the accumulator capacity determines its ability to store and release steam.

[0065] The purpose of collecting the initial pressure of the gas supply source is to understand the initial state of the gas supply, which serves as the basis for subsequent analysis of changes in the theoretical pressure value of the gas supply source.

[0066] The current steam supply flow rate and pipeline diameter are key parameters for calculating the pressure loss of the main steam supply pipeline. According to fluid mechanics principles, pipeline pressure loss is proportional to the square of the flow rate and is related to factors such as pipeline diameter.

[0067] The current steam supply flow rate, velocity, and opening degree of the control valve are used to analyze the working state and performance of the control valve; the flow rate and velocity can help calculate the pressure loss of the control valve, and the current opening degree is a reference for subsequent calculation of the ideal control valve opening degree, and is also used to analyze the regulating effect of the control valve on the steam supply pressure.

[0068] The current steam supply flow rate and pressure under standard conditions at the shaft seal are used to calculate the pressure loss at the shaft seal and to assess the steam supply situation at the shaft seal. The pressure loss calculation at the shaft seal requires the flow rate at the shaft seal, while the pressure under standard conditions is used for comparison and analysis with the actual steam supply pressure.

[0069] Fluid characteristic parameters include the collected fluid density and fluid dynamic viscosity, because they are factors in the subsequent calculation of the Reynolds number, which is related to the calculation of the control valve opening. At the same time, these parameters are also used in fluid dynamics calculations to analyze the flow characteristics of the fluid in the system.

[0070] For pressure parameters, appropriate pressure sensors can be selected and installed at corresponding locations, such as steam accumulators, gas supply sources, main steam supply pipelines, regulating valves, and shaft seals. Flow parameters can be measured by installing flow meters, such as at the inlet and outlet of steam accumulators, main steam supply pipelines, regulating valves, and shaft seals. For velocity measurement, velocity sensors can be used, or the velocity can be calculated based on the flow rate and the cross-sectional area of ​​the pipeline. The opening degree of regulating valves can be measured by installing opening degree sensors or displacement sensors on the regulating valves. Finally, appropriate data acquisition equipment, such as data acquisition cards, is selected to collect and process the data acquired by the sensors. Data processing algorithms are established to filter and calibrate the acquired data to improve its accuracy and reliability. The processed data is then transmitted to the control system to provide data support for subsequent calculations and analysis.

[0071] To further optimize the above embodiments, the process of periodically calculating the steam accumulator pressure value and analyzing the theoretical pressure value of the gas supply source affected by it based on the steam accumulator pressure value includes:

[0072] A pre-set periodic time limit t is established, and a steam accumulator pressure simulation model is built based on the initial pressure and capacity of the steam accumulator and the current steam flow rate at the inlet and outlet.

[0073]

[0074] Among them, P st (t) represents the current steam accumulator pressure value, P st0 C is the initial pressure of the steam accumulator. st Q is a capacity factor determined based on the steam accumulator's capacity, reflecting the accumulator's ability to store and release steam. It is determined according to industry standards corresponding to the steam accumulator's capacity. in (t) and Q out (t) represents the inlet and outlet steam flow rates of the steam accumulator, respectively, and t is the period time.

[0075] The current steam accumulator pressure value P is obtained through calculation. st (t);

[0076] Further based on model P suadj (t)=P su +α*P st (t) Adjust the theoretical pressure value of the gas supply source;

[0077] Among them, P siadj (t) represents the theoretical pressure value of the gas supply source, P su α is the initial pressure of the gas supply source; α is the supplementary coefficient, which reflects the degree to which the steam accumulator pressure supplements the steam supply source pressure, and is determined through experimental debugging.

[0078] It should be noted that the steam accumulator pressure simulation model is based on the principle of mass conservation and the compressibility of steam. In a closed steam accumulator system, the change in steam mass equals the mass of incoming steam minus the mass of outgoing steam. According to the transformation of the ideal gas law, pressure is related to mass and volume, while the volume of the accumulator is fixed (determined by its capacity). Therefore, the current pressure value can be calculated using the initial pressure, capacity, and inlet and outlet steam flow rates. The capacity coefficient reflects the steam accumulator's ability to store and release steam. Accumulators with different capacities will have different pressure responses to the same change in steam flow rate. Determining the capacity coefficient through industry standards can more accurately simulate the actual performance of the accumulator.

[0079] Since steam accumulators can affect the pressure of the gas supply source, the theoretical pressure value of the gas supply source needs to be adjusted accordingly when the pressure of the steam accumulator changes; the supplementary coefficient is used to quantify the degree of this influence.

[0080] The supplementary coefficient α represents the degree to which the steam accumulator pressure supplements the steam source pressure. It is used to adjust the steam source pressure to account for the role of the steam accumulator in the system. When the supplementary coefficient is zero, it means that the steam accumulator has no supplementary effect on the steam source pressure. As the supplementary coefficient increases, the supplementary effect of the steam accumulator on the steam source pressure is enhanced. The magnitude of the supplementary coefficient determines the weight of the steam accumulator pressure when calculating the adjusted steam source pressure.

[0081] Experimental debugging was conducted in an actual low-pressure shaft seal steam supply system. Starting with an initial supplementary coefficient value, such as α = 0.1, the system's operation under different working conditions was observed. The supplementary coefficient value was gradually adjusted, while monitoring indicators such as the steam supply pressure of the low-pressure shaft seal, the pressure change of the steam accumulator, and the stability of the system. If the steam supply pressure fluctuated significantly or the system was unstable, the supplementary coefficient could be appropriately reduced. If the steam supply pressure could not meet the requirements, the supplementary coefficient could be increased. Through repeated debugging, a supplementary coefficient value that optimizes system performance was found.

[0082] Alternatively, the model can be determined through theoretical analysis and simulation. Based on the principles of fluid mechanics and thermodynamics, a mathematical model of the low-pressure shaft seal steam supply system is established. The model considers factors such as the physical characteristics of the steam accumulator, the characteristics of the steam source, and pipeline resistance. By performing numerical simulations on the model, the impact of different supplementary coefficient values ​​on system performance can be analyzed. For example, the changes in the steam supply pressure of the low-pressure shaft seal, the pressure fluctuations of the steam accumulator, and the energy balance of the system under different supplementary coefficients can be calculated. Based on the simulation results, a suitable range or optimal value of the supplementary coefficient can be determined.

[0083] Alternatively, it can be determined through empirical methods, referring to similar low-pressure shaft seal steam supply systems or related engineering experience to understand the range of values ​​for the supplementary coefficient in similar systems; based on the characteristics and requirements of the current system, the empirical value can be appropriately adjusted to determine a preliminary supplementary coefficient value;

[0084] In actual operation, the supplementary coefficients can be further adjusted according to the actual performance of the system to achieve the best operating effect; however, the specific adjustment process is based on existing methods and will not be elaborated on further.

[0085] To further optimize the above embodiments, the process of analyzing the low-pressure shaft seal steam supply pressure data based on the theoretical pressure value of the air supply source and the pressure loss of each connected device includes:

[0086] The current pipeline pressure loss, regulating valve pressure loss, and shaft seal pressure loss are determined based on the current fluid flow rate in the main steam supply pipeline, regulating valve, and shaft seal; the calculation formula is as follows:

[0087] ΔP pipe =K pipe *Q sup(t) 2

[0088] ΔP valve =K valve *Q valve (t) 2

[0089] ΔP seal =K seal *Q seal (t) 2

[0090] Where, ΔP pipe For pipeline pressure loss, Q valve (t) represents the current steam supply flow rate of the main steam supply pipeline; K pipe ΔP is the pipe resistance coefficient, used to reflect the magnitude of the resistance encountered by fluid flowing in a pipe. Its value is determined experimentally using the Darcy-Weisbach formula principle. valve To control the pressure loss of the valve, Q valve (t) represents the current steam supply flow rate of the regulating valve; K valve The resistance coefficient of a control valve, ΔP, reflects the resistance encountered by fluid as it passes through the valve and is provided by the valve manufacturer. seal Q represents the shaft seal pressure loss. seal (t) represents the current steam supply flow rate at the shaft seal; K seal This is the resistance coefficient at the shaft seal, used to reflect the magnitude of the resistance encountered by the fluid flowing at the shaft seal. It is calculated in conjunction with the pipeline resistance coefficient K. valve The same principle determines the numerical value;

[0091] Based on model P seal (t)=P suadj (t)-ΔP pipe -ΔP valve -ΔP seal Calculate the current low-pressure shaft seal steam supply pressure data P seal (t).

[0092] It should be noted that the pipe resistance coefficient reflects the magnitude of the resistance encountered by the fluid when it flows in the pipe; it is a parameter related to factors such as the geometry and roughness of the pipe, the physical properties of the fluid, and the flow state; the larger the pipe resistance coefficient, the greater the resistance encountered by the fluid when it flows in the pipe, and the greater the pressure loss.

[0093] The pipe resistance coefficient is obtained through experimental testing in actual pipe systems. It can be calculated by measuring the pressure difference across the pipe at different flow rates, as well as parameters such as fluid velocity. A flow meter can be used to measure the flow rate, and a pressure sensor to measure the pressure difference. Then, the Darcy-Weisbach formula can be applied. By performing calculations and taking multiple measurements with varying flow rates, the resistance coefficient under different flow rates can be obtained. Then, averaging or fitting can yield a more accurate value for the pipe resistance coefficient. For some common pipe types and fluids, relevant engineering manuals or empirical formulas can be consulted to estimate the pipe resistance coefficient. These empirical formulas are usually based on a large amount of experimental data and practical engineering experience, and can quickly estimate the pipe resistance coefficient to a certain extent, but they need to be adjusted appropriately according to specific circumstances.

[0094] The resistance coefficient of a control valve indicates the magnitude of the resistance encountered by the fluid when passing through the control valve. It is related to factors such as the structure and opening degree of the control valve, the physical properties of the fluid, and the flow state. The larger the resistance coefficient of the control valve, the greater the pressure loss when the fluid passes through the control valve. The function of the control valve is to regulate the flow rate and pressure of the fluid, and the magnitude of its resistance coefficient directly affects the flow control and pressure regulation performance of the system.

[0095] Control valve manufacturers typically provide resistance coefficient curves or data for different valve opening degrees in their product manuals. These data, obtained through experimental testing, can serve as preliminary reference values. In practical applications, the appropriate resistance coefficient value can be selected from the manufacturer's data based on the actual valve opening degree and operating conditions. The control valve is then installed in the actual system, and experimental testing is conducted. By measuring parameters such as the pressure difference before and after the control valve and the fluid velocity, the resistance coefficient of the control valve can be calculated. Pressure sensors can be used to measure the pressure difference, and flow meters to measure the flow velocity. Then, following calculation methods similar to those used for pipeline resistance coefficients, such as... The West-Weisbach formula can be used for calculation. By changing the opening and flow rate of the control valve and performing multiple measurements, the resistance coefficient under different opening and flow rates can be obtained. Then, fitting or averaging can be performed to obtain a more accurate value for the control valve resistance coefficient. Another method is to use fluid dynamics software to numerically simulate the fluid flow inside the control valve. By establishing a three-dimensional model of the control valve and setting the physical properties and boundary conditions of the fluid, the flow of fluid inside the control valve can be simulated, and the resistance coefficient of the control valve can be calculated. This method can take into account the complex structure and flow details of the control valve, but it requires certain professional knowledge and computational resources.

[0096] The shaft seal resistance coefficient reflects the magnitude of the resistance encountered by the fluid when flowing at the shaft seal. The function of the shaft seal is to prevent fluid leakage while allowing the shaft to rotate. The shaft seal resistance coefficient is related to factors such as the structure of the shaft seal, the sealing material, the rotational speed of the shaft, the physical properties of the fluid, and the flow state. The larger the shaft seal resistance coefficient, the greater the pressure loss of the fluid at the shaft seal, and the greater the impact on the performance of the system.

[0097] Experimental tests are conducted on actual shaft sealing devices. By measuring parameters such as the pressure difference before and after the shaft seal and the fluid velocity, the resistance coefficient of the shaft seal can be calculated. Pressure sensors can be used to measure the pressure difference, and flow meters can be used to measure the flow velocity. Then, the resistance coefficient can be calculated using a similar method. By changing the shaft rotation speed, fluid flow rate, and other conditions, multiple measurements can be taken to obtain the shaft seal resistance coefficient under different conditions. Then, averaging or fitting can be performed to obtain a more accurate shaft seal resistance coefficient value. For some common shaft seal types and fluids, relevant engineering manuals or empirical formulas can be consulted to estimate the shaft seal resistance coefficient. These empirical formulas are usually based on a large amount of experimental data and practical engineering experience, and can quickly estimate the shaft seal resistance coefficient to a certain extent, but may need to be adjusted appropriately according to specific circumstances.

[0098] The low-pressure shaft seal steam supply pressure is equal to the theoretical pressure value of the air supply source minus the pressure loss of each connected device. This is based on the principles of energy conservation and pressure transmission. The pressure provided by the air supply source will gradually decrease as it passes through pipes, regulating valves, and shaft seals due to the resistance of these devices. The pressure that finally reaches the shaft seal is the actual steam supply pressure. By calculating the pressure loss of each device and subtracting it from the theoretical pressure value of the air supply source, the low-pressure shaft seal steam supply pressure data can be obtained.

[0099] To further optimize the above embodiments, the process of analyzing the pressure deviation data and pressure deviation change rate at the current moment based on the low-pressure shaft seal steam supply pressure data under continuous cycles includes:

[0100] The pressure deviation data E at the current moment is calculated based on the pressure deviation simulation model. p The pressure deviation simulation model is as follows:

[0101]

[0102] Among them, P set P is the pressure of the shaft seal under standard conditions. range The pressure measurement range is determined based on the sensor specifications;

[0103] Obtain the pressure deviation data E at the current moment. p Then, through the model Calculate the rate of change of pressure deviation C at the current moment. Ep Among them, T sample The sampling time is the periodic time limit t.

[0104] It should be noted that the pressure deviation data reflects the degree of difference between the current low-pressure shaft seal steam supply pressure and the set standard pressure. The pressure deviation simulation model compares the current low-pressure shaft seal steam supply pressure data with the pressure of the shaft seal under standard conditions, and then normalizes it by dividing by the pressure measurement range. This provides a more intuitive understanding of the deviation of the current steam supply pressure from the standard pressure, facilitating subsequent targeted adjustments. The pressure measurement range is determined based on the sensor specifications, ensuring a unified deviation measurement standard across different sensor measurement systems.

[0105] The pressure deviation change rate refers to the rate at which the pressure deviation changes over time. It can be obtained by differentiating the pressure deviation data (in discrete systems, by calculating the pressure deviation difference between adjacent periods) and multiplying it by the sampling time. A large pressure deviation change rate indicates that the steam supply pressure is rapidly deviating from the set value, requiring timely adjustment of the regulating valve opening to stabilize the steam supply pressure. The sampling time, i.e., the periodic time limit t, determines the frequency of data acquisition and analysis. A suitable sampling time ensures timely capture of pressure changes without increasing the system load due to excessively frequent data acquisition.

[0106] In the pressure deviation calculation formula, the pressure measurement range refers to the difference between the maximum and minimum pressure measurements involved in the low-pressure shaft seal steam supply system; it represents the range of possible pressure variations in the system; for example, if the pressure measurement range is 0-10MPa, then the pressure values ​​measured in the system will theoretically fluctuate within this range; the setting of the pressure measurement range is mainly to normalize the pressure deviation, so that systems with different pressure levels can be compared and analyzed under a relatively uniform standard.

[0107] During the system design phase, the pressure measurement range is determined based on the operating requirements and expected pressure variation range of the low-pressure shaft seal steam supply system. For example, if the maximum pressure of the steam source, the operating pressure range of the steam accumulator, and the required pressure range at the shaft seal are known, a suitable pressure measurement range can be determined by comprehensively considering these factors. Simultaneously, factors such as potential pressure fluctuations, overload conditions, and safety margins in the system should be considered to ensure that the pressure measurement range can cover pressure variations under various operating conditions. Another approach is to examine the specifications and measurement range of the pressure sensors used in the system. The measurement range of a pressure sensor is usually determined by its technical characteristics; when selecting a suitable pressure sensor, its measurement range should meet the system's pressure measurement requirements. The system's pressure measurement range is then determined based on the measurement range of the pressure sensors. If multiple pressure sensors with different measurement ranges are used in the system, a suitable overall pressure measurement range can be determined by comprehensively considering the measurement ranges of these sensors.

[0108] To further optimize the above embodiments, the process of calculating the ideal control valve opening based on the control valve opening of the previous cycle and the pressure deviation data and pressure deviation change rate at the current moment includes:

[0109] A valve opening simulation model is pre-established. The valve opening of the previous cycle and the pressure deviation data and pressure deviation change rate at the current moment are substituted into the valve opening simulation model to calculate the current ideal valve opening U(t).

[0110] The opening simulation model is as follows:

[0111]

[0112] Where U(t-1) is the valve opening in the previous cycle, and Re is the Reynolds number, specifically... ρ is the fluid density, v is the current steam supply velocity of the control valve, μ is the fluid dynamic viscosity, and d is the diameter of the main steam supply pipeline; ω1, ω2, and ω3 are all adjustment coefficients. ω1 reflects the degree of influence of pressure deviation on the control valve opening, determining the proportional relationship between the adjustment range of the control valve opening and the pressure deviation at the current moment to eliminate the pressure deviation. It is determined through experimental debugging or theoretical analysis. ω2 reflects the degree of influence of the rate of change of pressure deviation on the control valve opening. The control valve opening is adjusted according to the rate of change of pressure deviation to anticipate the trend of system pressure changes. It is determined through dynamic response analysis or parameter optimization. ω3 reflects the influence of the fluid's physical properties, i.e., the Reynolds number, on the control valve opening. It is determined through fluid characteristic analysis or empirical methods combined with experiments.

[0113] It should be noted that the coefficient ω1 reflects the degree of influence of pressure deviation on the opening of the control valve; it determines the proportional relationship between the adjustment range of the control valve opening and the pressure deviation at the current moment in order to eliminate the pressure deviation. Its acquisition methods include: Experimental debugging: In an actual system, by gradually changing the pressure deviation, observe the effect of the control valve opening change on the system pressure; starting from an initial ω1 value, gradually adjust its size, and record the system's pressure response and stability at different ω1 values; for example, a smaller ω1 value can be set first to observe whether the system's response to the pressure deviation is too slow; then gradually increase the ω1 value to observe whether the system exhibits over-adjustment; through repeated debugging, find an ω1 value that allows the system to respond quickly and stably to the pressure deviation; Theoretical analysis: Based on the system's physical characteristics and control requirements, conduct theoretical analysis; consider the influence of pressure deviation on system flow and pressure, as well as the characteristics of the control valve, and determine the approximate range of ω1 through derivation and calculation; then combine experimental debugging for further optimization;

[0114] The coefficient ω2 represents the degree of influence of the pressure deviation change rate on the control valve opening. It is used to adjust the control valve opening according to the rate of change of pressure deviation, so as to anticipate the changing trend of system pressure and improve the system stability and response speed. Its acquisition methods include: Dynamic response analysis: analyzing the dynamic response of the system to the pressure deviation change rate; by introducing different magnitudes of pressure deviation change rates into the system, observing the impact of control valve opening changes on system stability; if the system's response to the pressure deviation change rate is too sensitive, the value of ω2 can be appropriately reduced; if the system's response to the pressure deviation change rate is not significant, the value of ω2 can be increased; through repeated adjustments and tests, a suitable value of ω2 is found, enabling the system to adjust the control valve opening in a timely manner when a pressure change trend appears, thereby improving the system's stability and response speed; Parameter optimization method: some parameter optimization algorithms, such as gradient descent and genetic algorithms, can be used to automatically search for the optimal value of ω2. These algorithms can find the parameter value that optimizes system performance by iteratively adjusting the value of ω2 based on the system's performance indicators (such as pressure stability, response time, etc.).

[0115] The coefficient ω3 is related to the Reynolds number and reflects the influence of the fluid's physical properties (represented by the Reynolds number) on the control valve opening. It is used to adjust the control valve opening based on the fluid's flow state (characterized by the Reynolds number) to ensure that the valve opening adjustment can adapt to different fluid flow conditions. Its acquisition methods include: fluid characteristic analysis: analyzing the influence of the fluid on the control valve opening based on its physical properties (such as density and viscosity) and flow state (reflected by the Reynolds number); and determining the relationship between the control valve opening and fluid characteristics at different Reynolds numbers through theoretical calculations or numerical simulations, thereby obtaining ω3. The approximate range of ω3 is determined; then, experimental verification is conducted in the actual system. By changing parameters such as fluid velocity and viscosity, the changes in the opening of the regulating valve are observed, and the value of ω3 is further adjusted to ensure that the adjustment of the regulating valve opening can adapt to different fluid flow conditions. The empirical method is combined with experiments: referring to the empirical data of similar systems, the range of values ​​under different fluid conditions is understood; then, based on the characteristics of the current system and the actual operation, a preliminary value is determined; in actual operation, by monitoring parameters such as system pressure, flow rate, and regulating valve opening, ω3 is adjusted and optimized based on the system performance.

[0116] To further optimize the above embodiments, the process of controlling the regulating valve's regulating action based on the ideal regulating valve opening includes:

[0117] The PID controller converts the current ideal valve opening U(t) into a command signal and sends it to the front-end controller, which then controls the valve to perform the adjustment action according to the command signal.

[0118] It should be noted that using dedicated PID controller hardware modules, which typically have standard interfaces for easy connection to other devices in the system, is an option. When setting up the PID controller, the proportional, integral, and derivative parameters (P, I, D parameters) need to be adjusted according to the system's characteristics and requirements. These parameters can be determined through experimental debugging; generally, the proportional parameter is determined first, and then the integral and derivative parameters are gradually adjusted based on the system's response to achieve the best control effect. Alternatively, a software algorithm can be used to implement the PID controller. This involves writing PID control algorithm code in the control system's software program, collecting data on the ideal valve opening and the current valve opening, performing proportional, integral, and derivative calculations in the program, and generating command signals. This method requires a certain level of software programming skill but offers greater flexibility and allows for customized development based on the specific system requirements.

[0119] A reliable communication connection needs to be established between the front-end controller and the regulating valve. If it is an electric regulating valve, an electrical interface can be used for connection, such as connecting the controller and the motor driver of the regulating valve through a wire, and adjusting the opening of the regulating valve by controlling the rotation of the motor. If it is a pneumatic regulating valve, a pneumatic interface can be used for connection, such as connecting the controller and the pneumatic actuator of the regulating valve through an air pipe, and adjusting the opening of the regulating valve by controlling the pressure and flow of the gas.

[0120] To further optimize the above embodiments, the following are also included:

[0121] A normally open bypass is installed after the regulating valve. The normally open bypass provides the minimum air supply to the low-pressure cylinder to avoid the impact on the system caused by excessive changes in the opening of the regulating valve.

[0122] It should be noted that when the opening of the regulating valve changes too much, it will cause a sharp change in the steam supply flow, which will impact the system. The normally open bypass is set up to provide a relatively stable steam supply channel in this situation, providing a minimum steam supply to the low-pressure cylinder. Even if the opening of the regulating valve changes significantly, the existence of the bypass can ensure a certain amount of steam is continuously supplied to the low-pressure cylinder, avoiding adverse effects such as system pressure fluctuations and equipment vibration caused by sudden changes in the steam supply flow, and preventing the machine from tripping in the event of a sudden failure of the regulating valve.

[0123] The normally open bypass provides a redundant steam supply method for the system. Under normal circumstances, the minimum steam supply provided by the bypass can maintain the basic operating requirements of the low-pressure cylinder, while the regulating valve adjusts the steam flow according to the system requirements. When the regulating valve malfunctions or the opening adjustment is abnormal, the bypass can continue to supply steam to the low-pressure cylinder, ensuring that the system will not be completely interrupted due to the problem of the regulating valve, thereby improving the reliability and stability of the system.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the safety of low-pressure shaft seal steam supply, characterized in that: The following steps are involved: A method for improving the safety of low-pressure shaft seal steam supply, characterized by comprising the following steps: Step 1: real-time collection of operating parameters of the steam accumulator, gas supply source, main steam supply pipeline, regulating valve and shaft seal; Step 2: periodically calculating the steam accumulator pressure value, and analyzing the theoretical pressure value of the gas supply source affected by the steam accumulator pressure value based on the steam accumulator pressure value; Step 3: Analyze the steam supply pressure data of the low-pressure shaft seal based on the theoretical pressure value of the gas supply source and the pressure loss of each connected equipment; Step 4: Analyze the pressure deviation data and pressure deviation change rate at the current moment according to the low-pressure shaft seal steam supply pressure data under continuous cycles; Step 5, calculating the ideal regulating valve opening based on the regulating valve opening of the previous cycle and the pressure deviation data and the pressure deviation change rate at the current moment; Step six, controlling the regulating action of the regulating valve according to the ideal regulating valve opening.

2. A method for improving the safety of low-pressure shaft seal steam supply according to claim 1, characterized in that: In step 1, the operating parameters include: The data collected include the initial pressure of the steam accumulator, the steam flow rates at the inlet and outlet, and the accumulator capacity; the initial pressure of the gas supply source; the current steam flow rate and the pipe diameter of the main steam supply pipeline; the current steam flow rate, flow velocity, and current opening of the regulating valve; the current steam flow rate and the pressure under standard conditions at the shaft seal; and the fluid density and the fluid dynamic viscosity.

3. A method for improving the safety of low-pressure shaft seal steam supply according to claim 2, characterized in that: The process of periodically calculating the steam accumulator pressure value and analyzing the theoretical pressure value of the gas supply source affected by the steam accumulator pressure value based on the steam accumulator pressure value includes: A cycle time limit t is preset, and a steam accumulator pressure simulation model is established according to the initial pressure and capacity of the steam accumulator and the current inlet and outlet steam flows; Among them, P st (t) is the current steam accumulator pressure value, P st0 is the initial pressure of the steam accumulator; C st It is a capacity factor determined based on the capacity of the steam accumulator, which is used to reflect the ability of the steam accumulator to store and release steam and is determined by the industry standard corresponding to the capacity of the steam accumulator; Q in (t) and Q out (t) are the inlet and outlet steam flow rates of the steam accumulator, respectively, and t is the cycle time limit; The current steam accumulator pressure value P is obtained by calculation st (t); Further based on model P suadj (t) = P su +α*P st (t) Adjust the theoretical pressure value of the gas supply source; Among them, P suadj (t) is the theoretical pressure value of the gas supply source, P su is the initial pressure of the gas supply source; α is the supplement coefficient, which is used to reflect the degree of supplementation of the steam accumulator pressure to the steam supply source pressure and is determined by experimental debugging method.

4. A method for improving the safety of low-pressure shaft seal steam supply according to claim 3, characterized in that: The process of analyzing the low-pressure shaft seal steam supply pressure data based on the theoretical pressure value of the gas supply source and the pressure loss of each connected device includes: Based on the current flow rate of the fluid in the main steam supply pipeline, the regulating valve and the shaft seal, the current pipeline pressure loss, the regulating valve pressure loss and the shaft seal pressure loss are determined; the calculation formula is: ΔP pipe =K pipe *Q sup (t) 2 ΔP valve =K valve *Q valve (t) 2 ΔP seal =K seal *Q seal (t) 2 Among them, ΔP pipe is the pipeline pressure loss, Q valve (t) is the current steam supply flow rate of the main steam supply pipeline; K pipe ΔP is the pipeline resistance coefficient, which is used to reflect the resistance encountered by the fluid when it flows in the pipeline. The value is determined by experimental measurement combined with the Darcy-Weisbach formula principle; valve is the pressure loss of the regulating valve, Q valve (t) is the current steam supply flow rate of the regulating valve; K valve ΔP is the resistance coefficient of the regulating valve, which is used to reflect the resistance encountered by the fluid when passing through the regulating valve. It is provided by the regulating valve manufacturer; seal is the shaft seal pressure loss, Q seal (t) is the current steam supply flow at the shaft seal; K seal The resistance coefficient at the shaft seal is used to reflect the resistance encountered by the fluid when it flows at the shaft seal. It is calculated by comparing with the pipeline resistance coefficient K valve The same principle determines the value; Based on the model P seal (t) = P suadj (t)-ΔP pipe -ΔP valve -ΔP seal Calculate the current low-pressure shaft seal steam supply pressure data P seal (t).

5. A method for improving the safety of low-pressure shaft seal steam supply according to claim 4, characterized in that: The process of analyzing the pressure deviation data and the pressure deviation change rate at the current moment according to the low-pressure shaft seal steam supply pressure data under continuous cycles includes: Calculate the current pressure deviation data E based on the pressure deviation simulation model p ; The pressure deviation simulation model is: Among them, P set is the pressure of the shaft seal under standard conditions; p range is the pressure measurement range, determined based on the sensor specifications; Get the current pressure deviation data E p Afterwards, through the model Calculate the pressure deviation change rate C at the current moment Ep ; Among them, T sample is the sampling time, that is, the cycle time limit t.

6. A method for improving the safety of low-pressure shaft seal steam supply according to claim 5, characterized in that: The process of calculating the ideal regulating valve opening based on the regulating valve opening of the previous cycle and the pressure deviation data and the pressure deviation change rate at the current moment includes: Establishing an opening simulation model in advance, substituting the regulating valve opening of the previous cycle and the pressure deviation data and the pressure deviation change rate at the current moment into the opening simulation model, and calculating the current ideal regulating valve opening U(t); The opening simulation model is: Among them, U(t-1) is the opening of the control valve in the previous cycle, and Re is the Reynolds number, which is specifically ρ is the fluid density, v is the current steam supply flow rate of the regulating valve, μ is the fluid dynamic viscosity, and d is the pipe diameter of the main steam supply pipeline; ω1, ω2, and ω3 are all adjustment coefficients, among which ω1 is used to reflect the influence of the pressure deviation on the opening of the regulating valve, and determines the proportional relationship between the amplitude of the regulating valve opening that needs to be adjusted and the pressure deviation in order to eliminate the pressure deviation at the current moment, which is determined by experimental debugging method or theoretical analysis method; ω2 is used to reflect the influence of the pressure deviation change rate on the opening of the regulating valve, and adjusts the regulating valve opening according to the changing speed of the pressure deviation to respond to the changing trend of the system pressure in advance, which is determined by dynamic response analysis method or parameter optimization method; ω3 is used to reflect the physical properties of the fluid, that is, the influence of the Reynolds number on the opening of the regulating valve, which is determined by analyzing the fluid properties or combining empirical method with experiments.

7. A method for improving the safety of low-pressure shaft seal steam supply according to claim 6, characterized in that: The process of controlling the regulating action of the regulating valve according to the ideal regulating valve opening comprises: The PID controller converts the current ideal regulating valve opening U(t) into a command signal and sends it to the front-end controller, which controls the regulating valve to complete the regulating action according to the command signal.

8. A method for improving the safety of low-pressure shaft seal steam supply according to claim 7, characterized in that: Also includes: A normally open bypass is arranged behind the regulating valve, and the normally open bypass provides a minimum air supply to the low-pressure cylinder to avoid the impact of excessive changes in the opening of the regulating valve on the system.

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