Hydrogen doping proportion control method of pipeline natural gas hydrogen doping device

Abstract

The invention discloses a hydrogen doping ratio control method of a pipeline natural gas hydrogen doping device, and belongs to the technical field of process control, the method is applied to an ejector device with an adjustable throat nozzle, and the method comprises the following steps: setting a target hydrogen doping ratio; collecting natural gas inlet pressure, ejector throat pressure and hydrogen source pressure in real time; based on the target hydrogen doping ratio and the real-time pressure, the target throat diameter is calculated through the established fluid dynamic model; the target diameter is converted into the displacement amount of the driving ring block according to the geometrical relationship; the driving assembly is controlled to drive the ring block to move to adjust the throat diameter; and finally, the actual hydrogen doping ratio is calculated based on the adjusted parameters, feedback verification and iterative adjustment are carried out, and closed-loop control is formed. According to the invention, automatic, accurate and stable adjustment of the hydrogen doping ratio is realized, through combination of model feedforward and feedback correction, the response is rapid, the anti-interference capability is strong, a safety monitoring and fault processing mechanism is integrated, and the safety and reliability of system operation are guaranteed.

Description

A method for controlling the hydrogen blending ratio in a pipeline natural gas hydrogen blending device Technical Field

[0001] This invention relates to the field of gas mixing control technology, and in particular to a method for controlling the hydrogen blending ratio in a pipeline natural gas hydrogen blending device. Background Technology

[0002] Natural gas blending with hydrogen is a core pathway for the large-scale application of hydrogen energy and plays an increasingly important role in energy transition. Currently, the actively controlled blending systems commonly used in industrial practice consist of hydrogen compressors, flow monitoring units, regulating valves, control modules, and supporting software. However, these systems have revealed multiple technical bottlenecks in actual operation. First, the hydrogen compression process relies on external electrical power, resulting in high overall system energy consumption and significantly increasing operating costs. Second, due to the flammable and explosive gas atmosphere, the stability of electronic control components is severely tested; electromagnetic interference can easily cause signal distortion or control failure, forcing frequent system shutdowns for maintenance. More critically, when the system encounters a sudden malfunction, high-pressure natural gas may flow backward into low-pressure hydrogen pipelines, forming a dangerous gas mixture that could easily trigger catastrophic safety accidents such as explosions.

[0003] While ejector technology can circumvent the use of hydrogen compressors, existing ejector-type hydrogen blending devices mostly employ a fixed throat nozzle structure. The hydrogen blending ratio is fixed after installation and cannot be dynamically adjusted according to actual operating conditions. Some systems that incorporate adjustment functions rely excessively on complex closed-loop control logic. These methods require simultaneous acquisition of multi-dimensional parameters such as natural gas inlet pressure, ejector throat pressure, hydrogen source pressure, temperature, and flow rate. These parameters are then processed by a central processing unit to generate control commands to drive the components. This architecture inherently suffers from response delays. When natural gas pipeline pressure changes abruptly or user gas consumption fluctuates, the system cannot promptly track these changes, leading to significant oscillations in the hydrogen blending ratio and even momentary overshoot. This not only jeopardizes the integrity of the pipeline structure but may also cause instability in the terminal combustion equipment.

[0004] Existing control strategies have serious shortcomings in handling abnormal operating conditions. When pressure sensors experience zero-point drift, signal transmission links are interrupted, or drive components become mechanically jammed, the system lacks effective safety mechanisms, easily leading to runaway hydrogen blending ratios. Traditional control models are typically built based on ideal gas assumptions and steady-state flow theory, neglecting the compressibility effect, unsteady flow characteristics, and temperature gradient influence of actual gases during pipeline transmission, making it difficult to guarantee control accuracy under complex operating conditions. Furthermore, the system's adaptability to upstream pressure fluctuations is weak; when natural gas source pressure changes abruptly, it cannot actively compensate for parameter deviations, further exacerbating the instability of the hydrogen blending ratio. These deficiencies collectively restrict the safe promotion and large-scale application of natural gas hydrogen blending technology, necessitating the development of a hydrogen blending ratio control scheme that is structurally simple, responsive, inherently safe, and effectively adaptable to dynamic operating conditions. Summary of the Invention

[0005] The purpose of this application is to provide a method for controlling the hydrogen blending ratio of pipeline natural gas, which can achieve rapid response and precise control of the hydrogen blending ratio, improve system stability and safety, and reduce energy consumption.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for controlling the hydrogen blending ratio in a pipeline natural gas hydrogen blending device. The device includes an ejector with an adjustable throat nozzle. The ejector includes a ring block for adjusting the throat diameter and a drive assembly for moving the ring block. The throat diameter of the adjustable throat nozzle is adjusted by the drive assembly moving the ring block. The method includes the following steps:

[0007] S1: Set the target hydrogen doping ratio S2: Natural gas inlet pressure is collected. ejector throat pressure Hydrogen source pressure S3: Based on the target hydrogen doping ratio Natural gas inlet pressure ejector throat pressure and hydrogen source pressure S4: Calculate the target throat diameter using a pre-established and calibrated fluid dynamics model; S5: Calculate the target movement distance of the ring block driven by the drive assembly based on the pre-stored ejector geometry and target throat diameter; S6: Control the drive assembly to drive the ring block to move the target movement distance, adjusting the ejector throat diameter to match the target throat diameter. S6: Collect adjusted natural gas inlet pressure ejector throat pressure Hydrogen source pressure And based on the actual moving distance of the drive component, obtain the current throat diameter. S7: Based on the current throat diameter Query the preset throat diameter and flow area mapping table to obtain the hydrogen channel flow area. and natural gas channel circulation area S8: Based on the preset flow coefficients of hydrogen and natural gas, the density parameters of hydrogen and natural gas, the flow area of ​​the corresponding channels for hydrogen and natural gas, and the adjusted inlet pressure of natural gas. ejector throat pressure Hydrogen source pressure For each pressure parameter, the actual hydrogen doping ratio is obtained through a preset mass flow rate-based hydrogen doping ratio calculation model; S9: Calculate the actual hydrogen doping ratio Compared with the target hydrogen doping ratio deviation Determine the deviation If the absolute value of the deviation is less than the preset allowable error threshold, then maintain the current adjustment state; if the absolute value of the deviation exceeds the preset hydrogen doping ratio deviation threshold, then return to step S2 for iterative adjustment.

[0008] By adopting the above technical solution, this hydrogen blending ratio control method achieves precise setting based on the preset calibration relationship between throat opening and hydrogen blending ratio. It completely eliminates the need for flow meters, pressure sensors, and complex controllers required by traditional closed-loop control systems, significantly simplifying the control architecture and operation process. The pure mechanical passive adjustment mechanism completely eliminates the dependence on external power supply and electronic components, greatly improving the inherent safety and anti-electromagnetic interference capability of the system in high-pressure flammable and explosive environments. The adjustment action is directly completed by the operator without signal acquisition, processing, or feedback delay. The response speed is at the millisecond level, which can instantly adapt to pipeline pressure fluctuations, ensuring accurate and stable hydrogen blending ratio setting. At the same time, it significantly reduces equipment manufacturing costs, maintenance complexity, and operating energy consumption. There is no need to periodically calibrate sensors or update control software. Ordinary personnel can operate it proficiently after simple training, significantly improving the convenience, economy, and long-term reliability of field applications, and providing a solid control foundation for the large-scale and safe promotion of natural gas hydrogen blending technology.

[0009] The present invention is further configured such that the hydrogen doping ratio is: Defined as the ratio of hydrogen mass flow rate to natural gas mass flow rate: ,in, This represents the hydrogen mass flow rate. This refers to the mass flow rate of natural gas.

[0010] By adopting the above technical solution, this hydrogen blending ratio control method achieves precise setting based on the preset calibration relationship between throat opening and hydrogen blending ratio. It completely eliminates the need for flow meters, pressure sensors, and complex controllers required by traditional closed-loop control systems, significantly simplifying the control architecture and operation process. The pure mechanical passive adjustment mechanism completely eliminates the dependence on external power supply and electronic components, greatly improving the inherent safety and anti-electromagnetic interference capability of the system in high-pressure flammable and explosive environments. The adjustment action is directly completed by the operator without signal acquisition, processing, or feedback delay. The response speed is at the millisecond level, which can instantly adapt to pipeline pressure fluctuations, ensuring accurate and stable hydrogen blending ratio setting. At the same time, it significantly reduces equipment manufacturing costs, maintenance complexity, and operating energy consumption. There is no need to periodically calibrate sensors or update control software. Ordinary personnel can operate it proficiently after simple training, significantly improving the convenience, economy, and long-term reliability of field applications, and providing a solid control foundation for the large-scale and safe promotion of natural gas hydrogen blending technology.

[0011] The present invention is further configured such that: the mapping table between the throat diameter and the flow area is established through a calibration experiment: under fixed operating conditions, the flow area of ​​the hydrogen channel corresponding to different throat diameters is measured. Area of ​​natural gas channel And store.

[0012] By adopting the above technical solution, a mapping table between the throat diameter and the flow area of ​​hydrogen and natural gas channels is pre-established and stored through calibration experiments. This measure cleverly avoids the errors and computational burden that may be introduced by calculating the flow area in real time using complex geometric formulas. Due to factors such as machining accuracy, assembly gaps, and wear, the actual flow area of ​​the throat formed by the telescopic plate may deviate nonlinearly from the theoretical geometric area. Through experimental calibration, the actual effective flow area corresponding to each specific throat diameter can be obtained in a true and accurate manner, and this relationship can be solidified in the control system. This makes the area parameters used by the control model as close as possible to the physical reality, thereby greatly improving the accuracy of flow calculation and actual hydrogen doping ratio calculation, and fundamentally ensuring control accuracy. This is a pragmatic and efficient technical means that combines actual machining with theoretical control models.

[0013] The present invention is further configured such that the method also includes a safety monitoring step: continuously monitoring the working status of the pressure reducing valve and / or the pressure difference before and after the check valve on the low-pressure hydrogen pipeline connected to the ejector; when an abnormal signal is detected, controlling the drive mechanism to adjust the adjustable throat nozzle to a safe opening or closed state, and issuing an alarm.

[0014] By adopting the above technical solution, an independent safety monitoring step is introduced in parallel with the core proportional control cycle. This step continuously monitors key safety parameters such as the working status of the pressure reducing valve or the pressure difference across the check valve. This adds a crucial safety redundancy layer to the entire control system. Once the pressure reducing valve fails, causing an abnormal increase in hydrogen pressure, or an abnormal pressure difference across the check valve indicates a potential risk of backflow, the control system can immediately override the normal proportional regulation logic and prioritize the execution of safety strategies, such as forcibly adjusting the nozzle to a preset safe opening or closing it directly, and issuing an alarm. This achieves proactive safety protection, enabling intervention and alarms at the initial stage of hardware failure, preventing the failure from escalating and causing safety accidents. This greatly enhances the operational safety and reliability of the entire hydrogen blending unit under unattended or complex operating conditions.

[0015] The present invention is further configured such that the iterative adjustment in step S9 includes: adjusting according to the actual hydrogen doping ratio. The direction and magnitude of the deviation from the target hydrogen doping ratio will be used to correct the target hydrogen doping ratio in the next round of calculation formula for the target throat diameter.

[0016] By adopting the above technical solution, when the feedback verification finds that the deviation exceeds the allowable range, an intelligent iterative adjustment strategy is proposed. That is, the target hydrogen doping ratio input value used in the next round of calculation is corrected according to the direction and magnitude of the deviation between the actual hydrogen doping ratio and the target value. This essentially integrates the classic feedback control idea, such as the proportional-integral principle, into the feedforward control framework based on the physical model. By correcting the setpoint, it compensates for possible simplification errors, parameter drift, or unmodeled dynamic characteristics in the model itself. This makes the control system not only dependent on the initial accurate model, but also has the ability to continuously learn and adapt. Thus, it can maintain extremely high control accuracy over time and with changes in operating conditions, enhancing the robustness and long-term applicability of the method.

[0017] The present invention is further configured such that, before step S2, the pressure used to collect the natural gas inlet pressure is measured under no-flow conditions. ejector throat pressure Hydrogen source pressure Zero-point calibration is performed on the pressure sensor.

[0018] By adopting the above technical solution, a step of zero-point calibration of all pressure sensors under no-flow conditions is added before the system starts to regulate flow. This step specifically eliminates the fundamental impact of the zero-point drift error of the pressure sensors themselves on the control accuracy. Since the pressure parameter is the only input source of the entire control model, even a small measurement deviation will be amplified in the model calculation, leading to errors in the throat diameter calculation, and consequently causing the hydrogen doping ratio to run out of control. By forcing all sensor readings to zero in a no-flow static state, the signal reference offset caused by temperature changes, time accumulation, or electrical interference can be calibrated, ensuring that all subsequent dynamic pressure measurements are accurate values ​​relative to the true zero point. This lays a solid foundation of measurement data for high-precision control and is an indispensable preprocessing step for achieving stable control.

[0019] The present invention is further configured such that the method also includes a flow adaptive step: real-time monitoring of pressure or flow fluctuations in the high-pressure natural gas pipeline; when the fluctuation exceeds a set threshold, adjusting the pressure input value used to calculate the target adjustment parameter in step S2 in advance or synchronously to compensate for the impact of upstream fluctuations on the stability of the hydrogen doping ratio.

[0020] By adopting the above technical solution, a flow adaptive step is added. By monitoring the pressure or flow fluctuations of the upstream natural gas pipeline in real time, and adjusting the pressure input value used for control calculation in advance or synchronously when the fluctuation exceeds the threshold, this design enables the control system to have the ability to predict and compensate for upstream disturbances. Traditional feedback control has a lag in detection and execution when facing upstream sudden changes. However, this method actively monitors the upstream state and corrects the calculation starting point of the control model in advance before the disturbance affects the ejector throat pressure. This is equivalent to adding a feedforward channel to the control system, which can significantly reduce the instantaneous impact of upstream fluctuations on the mixing ratio and enable the system to recover stability more quickly. It is particularly suitable for scenarios with unstable pipeline pressure or drastic changes in gas consumption, and improves the system's anti-interference ability and overall stability.

[0021] The present invention is further configured to: when the pressure signal is detected to exceed the preset threshold range, the pressure signal mutation rate exceeds the set threshold, or the pressure signal is lost, or the drive component response times out, maintain the current throat diameter, trigger an audible and visual alarm, and switch the hydrogen doping ratio to the preset safe range.

[0022] By adopting the above technical solution, a complete set of fault detection and emergency handling logic is specified in detail. For various abnormal situations such as pressure signal over-limit, sudden change, loss, and drive component response timeout, clear fault judgment conditions and safety response strategies are set, namely, maintaining the current throat diameter, triggering audible and visual alarms, and switching the hydrogen doping ratio to a preset safe range. This builds the last line of defense for the system in extreme abnormal situations. When the core control cycle cannot work normally due to signal distortion or actuator failure, this strategy can immediately freeze the adjustment action to avoid performing dangerous operations under the drive of erroneous signals. At the same time, the audible and visual alarms will promptly notify the operators, and the mixing ratio will be locked at a preset safety value such as the combustion safety range, maximizing the safety of equipment and pipelines, and reflecting the thoroughness and safety of the control method design.

[0023] The present invention is further configured to: calculate the target throat diameter based on an ideal inviscid flow model of subsonic compressible gas during the start-up phase or when the target hydrogen doping ratio changes. The initial value is used as the starting diameter of the target throat diameter.

[0024] By adopting the above technical solution, when the system starts up or the target value changes, the initial value of the target throat diameter is preferentially calculated based on the ideal inviscid flow model of subsonic compressible gas. This strategy makes full use of the calculation speed advantage of the theoretical model, and can give a throat diameter starting point that is very close to the final steady-state value in milliseconds. This allows the drive component to start fine adjustment from a reasonable initial position, rather than starting a long search from a completely irrelevant starting point such as fully open or fully closed position. This greatly shortens the convergence time required for the system to reach the set ratio and speeds up the response. It is particularly suitable for application scenarios that require frequent switching of hydrogen doping ratio. At the same time, an accurate initial value also reduces the overshoot of the first adjustment and improves the stability of the adjustment process.

[0025] The present invention is further configured such that: the driving component includes a telescopic motor and a push rod driven by the telescopic motor; in step S5, the linear displacement of the push rod is controlled by controlling the number of rotations and direction of the telescopic motor, and the linear displacement of the push rod drives the ring block to move.

[0026] By adopting the above technical solution, the driving component is specifically defined as a linear motion mechanism driven by a telescopic motor to drive the push rod. A precise control relationship is established between the number of rotations and direction of the motor, the linear displacement of the push rod, and the final movement distance of the block. This allows the abstract control algorithm output to be accurately converted into the physical displacement of the mechanical parts. By controlling the number of rotations and direction of the motor in a standard and precise electrical control method, the diameter of the nozzle throat can be adjusted at the millimeter or even micrometer level. This method has high control precision, good repeatability, and is easy to integrate with digital control systems. Furthermore, the motor itself has a self-locking characteristic, which can maintain its position when the power supply is stopped, ensuring the long-term maintenance of the adjustment state. This provides a reliable and accurate final execution link for the entire high-precision control method.

[0027] This invention, by employing the above technical solutions, achieves significant technical effects: By constructing a multi-level intelligent control system integrating feedforward model calculation, feedback verification and correction, independent safety monitoring, and emergency fault handling, it successfully transforms a fluid mixing process reliant on complex mechanical adjustments into a standardized control flow that can operate automatically, with high precision and high reliability. Starting from a clear scientific definition, this method uses a physical model to convert the target ratio into executable mechanical adjustment commands. It compensates for deviations between the theoretical model and reality through calibration data, ensures input accuracy through sensor calibration, eliminates steady-state errors through iterative algorithms, resists upstream interference through feedforward compensation, and finally completes the action through a precise motor drive. The entire method is interconnected and logically rigorous, not only achieving rapid, accurate, and stable control of the hydrogen blending ratio but also ensuring the resilience and safety of the control system under various normal and abnormal operating conditions through parallel safety monitoring and fault handling mechanisms. This transforms the entire hydrogen blending device from a precision machine into an intelligent, reliable, and trustworthy automated system, providing a crucial control brain for large-scale engineering applications. Attached Figure Description

[0028] Figure 1 is a cross-sectional view of the pipeline natural gas hydrogen blending device; Figure 2 is a structural diagram of the pipeline natural gas hydrogen blending device; Figure 3 is a schematic diagram of the adjustable throat nozzle position; Figure 4 is a flowchart of the control method.

[0029] The parts referred to by the numbers in the above attached figures are as follows: 1. Ejector; 2. Ring block; 3. Drive assembly; 301. Telescopic motor; 302. Push rod; 4. Telescopic plate. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0031] Example 1: Traditional existing pipeline natural gas hydrogen blending systems, whether active control type or fixed structure ejector type, have limitations. Active control systems require additional electrical energy to drive hydrogen compression equipment, increasing operating costs; electronic control components are susceptible to electromagnetic interference in flammable and explosive environments, requiring frequent maintenance; and there is a possibility of high-pressure natural gas flowing back into the low-pressure hydrogen system. Fixed structure ejector 1 cannot dynamically adjust the hydrogen blending ratio according to demand. Some systems with adjustment functions rely on the real-time acquisition and calculation of multiple parameters, which cannot respond to changes in operating conditions in a timely manner, resulting in changes in the hydrogen blending ratio, affecting pipeline safety and the stability of terminal energy-consuming equipment. In addition, there are shortcomings in handling abnormal operating conditions, and the control model has deviations in actual operation.

[0032] This application proposes a method for controlling the hydrogen blending ratio in a pipeline natural gas hydrogen blending device. The device includes an ejector 1 with an adjustable throat nozzle. Referring to Figures 1 and 2, the ejector 1 includes a ring block 2 for adjusting the throat diameter and a drive assembly 3 for moving the ring block 2. The throat flow area of ​​the adjustable throat nozzle is adjusted by the drive assembly 3 driving the ring block 2 to move. The method includes the following steps: S1: Setting the target hydrogen blending ratio. S2: Natural gas inlet pressure is collected. ejector throat pressure Hydrogen source pressure S3: Based on the target hydrogen doping ratio , , and Calculate the diameter of the target throat The calculation formula is: ,in, For natural gas inlet pressure, The pressure at the throat of the ejector. For hydrogen source pressure, For the target hydrogen doping ratio, S4: Based on the pre-stored geometric structure relationship and the target throat diameter, the calibration constant is used. Calculate the target movement distance of circle 2. The calculation formula is: ,in, S5: The length of the nozzle telescopic plate 4 is n, the maximum design diameter of the nozzle throat is m, and the diameter of the natural gas pipeline is m. S6: The control drive assembly 3 drives the ring block 2 to move a target distance p, adjusting the throat diameter of the ejector 1 to the target throat diameter. S6: Data collection after adjustment , , And based on the actual moving distance of the drive component 3, the current throat diameter is obtained. S7: Based on the current throat diameter Query the preset throat diameter and flow area mapping table to obtain the hydrogen channel flow area. and natural gas channel circulation area S8: Obtain hydrogen density and natural gas density Calculate the actual hydrogen doping ratio The calculation formula is: ,in, The hydrogen flow rate coefficient is... The hydrogen channel flow area, The density of hydrogen gas, The natural gas flow coefficient, The area of ​​the natural gas channel. S9: Calculate the actual hydrogen blending ratio for natural gas density. Compared with the target hydrogen doping ratio deviation Determine the deviation If the absolute value of the deviation is less than the preset allowable error threshold, then maintain the current adjustment state; if the absolute value of the deviation exceeds the preset hydrogen doping ratio deviation threshold, then return to step S2 for iterative adjustment.

[0033] Referring to Figure 4, the target hydrogen blending ratio can be manually input by the operator through the human-machine interface to meet specific hydrogen blending requirements. Alternatively, the target hydrogen blending ratio can be pre-stored in the control system and automatically loaded according to different operating modes or production plans. In addition, the target hydrogen blending ratio can also be remotely set by receiving instructions from the upper-level scheduling system.

[0034] In step S2, the acquisition of natural gas inlet pressure P1, ejector throat pressure P2, and hydrogen source pressure P3 is the basis for real-time monitoring of the system's operating conditions. These pressure values ​​can be obtained by pressure sensors installed at the corresponding pipeline locations. For example, piezoresistive pressure sensors or capacitive pressure sensors can be used to convert pressure signals into electrical signals. These electrical signals can be read directly or converted into digital signals by an analog-to-digital converter for processing by the control system.

[0035] In step S3, based on the target hydrogen doping ratio P1, P2, and P3 calculate the target throat diameter. This calculation can be based on a pre-established mathematical model, for example, by consulting a lookup table containing target throat diameters corresponding to different pressure combinations and hydrogen doping ratios, or by using simplified hydrodynamic formulas combined with empirical coefficients for estimation.

[0036] The calibration constant K is a dimensionless comprehensive parameter whose theoretical value is determined by the structural dimensions of the device, fluid properties, and flow characteristics. Based on the fluid dynamics model, the theoretical expression for the constant K can be derived as follows: The system performs statistical analysis on a series of K values ​​calculated under multiple operating conditions, and stores the final determined K value or the fitting relationship between the K value and the operating conditions in the control system of the device for use by the control algorithm. The K value obtained through the above calibration process can effectively compensate for the difference between the theoretical model and the actual device, thereby ensuring that high-precision hydrogen doping ratio control can be achieved throughout the entire operating range.

[0037] In step S4, the target moving distance p of the ring block 2 is calculated based on the pre-stored geometric structure relationship. This geometric structure relationship can be a function describing the correspondence between the position of the ring block 2 and the throat diameter, and can be a linear or nonlinear function. By inputting the target throat diameter, the required moving distance p of the ring block 2 is directly calculated. This relationship can also be obtained through pre-performed mechanical measurements or design drawing analysis and stored in the form of a data table. The nozzle is configured with at least two circumferentially arranged telescopic plates 4 to enclose and form the nozzle throat. In this embodiment, at least eight telescopic plates 4 are configured, and elastic seals are provided between each telescopic plate 4. The ring block 2 is axially slidably fitted onto the outer side formed by the enclosing of each telescopic plate 4. The drive assembly 3 is connected to the ring block 2 and is used to drive the ring block 2 to move axially along the nozzle throat. In step S5, referring to Figure 3, the drive assembly 3 is controlled to drive the ring block 2 to move a target distance p, so that the diameter of the ejector 1 throat is adjusted to the target throat diameter. The drive assembly 3 can be an electric push rod 302, which is driven to extend and retract by controlling the rotation of its internal motor, thereby driving the ring block 2 to move. Alternatively, a pneumatic or hydraulic cylinder can be used, which drives the piston rod to move by controlling the air pressure or hydraulic pressure, thereby adjusting the position of the ring block 2.

[0038] In step S6, the adjusted P1, P2, and P3 are collected, and the current throat diameter is obtained based on the actual moving distance of the drive component 3. The adjusted pressure value can be collected in real time again by the pressure sensor. The current throat diameter can be directly measured by the displacement sensor integrated on the drive component 3, such as a grating ruler or a magnetostrictive displacement sensor, and calculated in combination with geometric relationships.

[0039] In step S7, based on the current throat diameter, a preset throat diameter and flow area mapping table is queried to obtain the flow area of ​​the hydrogen channel and the flow area of ​​the natural gas channel. This mapping table can be a two-dimensional array stored in the controller's memory, which contains the flow area data of the hydrogen and natural gas channels corresponding to different throat diameters. This data can be obtained through theoretical calculations, such as calculations based on the geometry of the fluid channels, or through simulation analysis using computer-aided design software.

[0040] In step S8, the hydrogen density is obtained. h2 and natural gas density g, and calculate the actual hydrogen blending ratio. The hydrogen density and natural gas density can be obtained by consulting the standard gas property table and correcting them according to the temperature and pressure under the current operating conditions, or by using a gas density sensor for real-time measurement. The actual hydrogen blending ratio is calculated strictly according to the given formula.

[0041] In step S9, the actual hydrogen doping ratio is calculated. Compared with the target hydrogen doping ratio The system calculates the deviation Δx and determines whether the deviation Δx is less than the preset allowable error threshold. If the absolute value of the deviation does not exceed the preset threshold, it is considered that the hydrogen doping ratio has met the requirements, and the system will maintain the current adjustment state. If the absolute value of the deviation exceeds the preset hydrogen doping ratio deviation threshold, it indicates that further adjustment is needed, and the system will return to step S2 to re-collect pressure data and perform a new round of calculation and adjustment to achieve iterative adjustment.

[0042] This method achieves dynamic control of the flow area of ​​the ejector 1 throat by real-time acquisition of pressure parameters and calculation and adjustment of the target throat diameter in combination with the target hydrogen blending ratio. As a result, this method can cope with pressure fluctuations or changes in gas consumption in the natural gas pipeline network and adjust the hydrogen blending ratio in a timely manner, avoiding the problems of response lag and changes in the hydrogen blending ratio in traditional systems. Through the iterative adjustment mechanism, the control accuracy and stability of the hydrogen blending ratio are improved, thereby meeting the requirements of precise control and high reliability for hydrogen blending in pipeline natural gas.

[0043] In the pipeline natural gas hydrogen blending ratio control method, the setting of the target hydrogen blending ratio is the basis of the entire control process. However, if the definition of the hydrogen blending ratio is unclear or inconsistent, it may lead to ambiguity in the actual calculation and control process, affecting the accuracy and stability of the hydrogen blending ratio, and thus affecting the control accuracy and safety of the entire system.

[0044] This application further proposes that the hydrogen blending ratio x be defined as the ratio of the hydrogen mass flow rate to the natural gas mass flow rate, i.e., x = m h2 / m g , where m h2 The mass flow rate of hydrogen is m. gThe hydrogen blending ratio, defined as the mass flow rate of natural gas, is a crucial parameter for measuring the hydrogen content in natural gas. This definition ensures the clarity and uniqueness of the hydrogen blending ratio in a physical sense. Mass flow rate is the mass of fluid passing through a specific cross-section per unit time, directly reflecting the amount of substance. Therefore, the hydrogen blending ratio defined based on mass flow rate offers higher accuracy and operability, avoiding errors caused by fluctuations in volumetric flow rate due to changes in temperature and pressure. This definition provides a unified and stable benchmark for subsequent calculations, control, and monitoring. The hydrogen mass flow rate is m. h2 The mass flow rate of hydrogen refers to the mass of hydrogen flowing through the hydrogen channel of ejector 1 per unit time. In practical applications, it can be directly measured by a flow meter or indirectly calculated using parameters such as pressure, temperature, fluid density, and channel flow area. For example, it can be monitored in real time using devices such as differential pressure flow meters, vortex flow meters, or Coriolis mass flow meters. The mass flow rate of natural gas (mg) refers to the mass of natural gas flowing through the natural gas channel of ejector 1 per unit time. Similar to the mass flow rate of hydrogen, the mass flow rate of natural gas can also be measured by a dedicated flow meter or by parameters such as the natural gas inlet pressure P1, ejector throat pressure P2, and natural gas density. This application calculates parameters such as g and the natural gas channel flow area, effectively solving the calculation and control error problem caused by the unclear definition of hydrogen doping ratio in the process of hydrogen doping ratio control. Based on the definition of mass flow rate, it eliminates the measurement uncertainty caused by environmental factors such as temperature and pressure affecting gas volume, making the physical meaning of hydrogen doping ratio clearer and more stable. This clear definition is the target hydrogen doping ratio in step S1. The setting provides a precise physical basis and a unified and reliable quantitative standard for calculating the target throat diameter in step S3 and the actual hydrogen blending ratio in step S8. Therefore, the entire control method can achieve more accurate target hydrogen blending ratio setting, more stable system regulation, and more reliable actual hydrogen blending ratio calculation based on this precise definition, thereby significantly improving the control accuracy and operational stability of the pipeline natural gas hydrogen blending device.

[0045] In the above-mentioned hydrogen blending ratio control method, in order to accurately calculate the actual hydrogen blending ratio, it is necessary to obtain the flow area of ​​the hydrogen channel and the flow area of ​​the natural gas channel. However, the throat diameter of the ejector 1 is adjustable and its internal structure is complex. The actual flow area of ​​the hydrogen and natural gas channels will change dynamically with the change of the throat diameter, and there may be a nonlinear relationship. If these flow areas are determined by relying solely on theoretical calculations or simplified models, it may lead to a large deviation from the actual situation, thereby affecting the calculation accuracy of the actual hydrogen blending ratio and ultimately reducing the accuracy and stability of the hydrogen blending ratio control.

[0046] In response, this application further proposes to establish a mapping table between throat diameter and flow area through calibration experiments: under fixed operating conditions, the flow areas of hydrogen and natural gas channels corresponding to different throat diameters are measured and stored.

[0047] The throat diameter-to-flow area mapping table is a data structure used to store the flow areas of the hydrogen and natural gas channels for different throat diameters of the adjustable throat nozzle of ejector 1. Due to the complexity of the internal flow channel geometry of ejector 1 and the dynamic adjustment characteristics of the adjustable throat nozzle, the actual effective flow area of ​​hydrogen and natural gas is not simply linearly related to the throat diameter, and may even be affected by hydrodynamic effects. Therefore, by establishing such a mapping table, the system can be provided with accurate values ​​of the hydrogen and natural gas channel flow areas for any given throat diameter, thus providing accurate input data for subsequent calculations of the actual hydrogen blending ratio. This mapping table can be used for lookup... The mapping table is stored and retrieved using methods such as lookup tables, interpolation functions, or fitted curves. The mapping table is established through calibration experiments. "Calibration experiments" refer to determining the performance parameters of ejector 1 under different working conditions through actual measurement and data acquisition in a controlled environment. For the establishment of the throat diameter to flow area mapping table, calibration experiments are an important means of obtaining real and accurate data. During the experiment, it is necessary to precisely control the throat diameter of ejector 1 and measure the effective flow area of ​​hydrogen and natural gas under a specific throat diameter. This experimental method can fully consider the influence of factors such as the actual geometric characteristics of the internal flow channel of ejector 1, fluid flow characteristics, and manufacturing tolerances on the flow area, thereby obtaining more reliable data than theoretical calculations.

[0048] Calibration experiments are typically conducted under fixed operating conditions. Fixed operating conditions mean that, during the calibration experiment, all key operating parameters except for the throat diameter, such as inlet pressure P1, hydrogen source pressure P3, temperature, and fluid type, remain constant. This is done to eliminate interference from other variables in the flow area measurement, ensuring that the measured flow area data is only related to changes in the throat diameter. This keeps parameters such as the natural gas inlet pressure P1, hydrogen source pressure P3, and ambient temperature within a preset stable range, simulating typical or representative conditions in actual operation. By measuring under fixed operating conditions, the comparability and consistency of the data can be ensured, improving the accuracy of the mapping table.

[0049] Measuring and storing the flow areas of hydrogen and natural gas channels corresponding to different throat diameters is the core step in the calibration experiment. Specifically, this can be achieved as follows: First, the throat diameter of ejector 1 is precisely adjusted to a series of preset discrete values ​​using the drive component 3. For each throat diameter value, hydrogen and natural gas can be introduced separately, and the actual flow rate through ejector 1 under a specific pressure difference is measured using a high-precision flow meter. Combining fluid mechanics principles, the flow area can be calculated by back-calculating the flow coefficient, pressure difference, and density. The corresponding flow areas of hydrogen and natural gas channels under that throat diameter can then be determined. These measured and calculated throat diameter, hydrogen channel flow area, and natural gas channel flow area data will be stored in the system's memory, database, or non-volatile memory, forming a mapping table. The storage format can be a two-dimensional array, a structure array, or a database record for subsequent processing. During the control process, rapid queries are performed. The mapping table between throat diameter and flow area no longer relies on simplified theoretical models or empirical estimations, but is established through rigorous calibration experiments and actual measurements under fixed operating conditions. This means that for each specific throat diameter of the adjustable throat nozzle of ejector 1, the system can obtain the actual verified, high-precision hydrogen and natural gas flow areas. This accurate flow area data is directly input into the calculation formula for the actual hydrogen blending ratio, significantly improving the accuracy of the actual hydrogen blending ratio calculation in step S8. Since the accuracy of the actual hydrogen blending ratio is the foundation of the entire closed-loop control system, establishing an accurate mapping table can effectively reduce control deviations, accelerate system convergence speed, and enable the actual hydrogen blending ratio to approach the target hydrogen blending ratio more quickly and stably. This not only improves the accuracy and response speed of hydrogen blending ratio control, but also enhances the reliability and safety of the entire hydrogen blending device.

[0050] In actual operation, critical safety components in the low-pressure hydrogen pipeline connected to ejector 1, such as pressure reducing valves or check valves, can malfunction or malfunction, potentially leading to unstable hydrogen supply, uncontrolled hydrogen blending ratios, or even serious safety hazards such as natural gas backflow into the hydrogen pipeline. This application further proposes a safety monitoring step to enhance the operational safety of the hydrogen blending device. This safety monitoring step includes continuously monitoring the operating status of the pressure reducing valve and / or the pressure difference across the check valve on the low-pressure hydrogen pipeline connected to ejector 1. Continuous monitoring means that the system will continuously acquire relevant data to achieve real-time awareness of potential risks. The pressure reducing valve is used to reduce the high-pressure hydrogen to the pressure of ejector 1. The required low pressure needs to be maintained and its stability is monitored. The pressure sensor installed at the inlet and outlet of the pressure reducing valve can acquire the pressure value in real time and compare it with the preset safe pressure range. In addition, the intelligent pressure reducing valve itself may have a status feedback function, which can directly output its operating status information, such as valve opening degree, fault code, etc. The check valve is a key component to prevent natural gas from flowing back into the hydrogen pipeline. By installing pressure sensors before and after the check valve, the pressure difference can be measured and calculated in real time. Under normal circumstances, the pressure on the hydrogen side should be higher than that on the natural gas side, and the pressure difference should be maintained within a specific range. If there is a reverse pressure difference or abnormal fluctuation in the pressure difference, it may indicate that the check valve has failed or there is a leak.

[0051] When an abnormal signal is detected, the system controls the drive mechanism to adjust the adjustable throat nozzle to a safe opening or closed state and issues an alarm. The abnormal signal refers to a deviation of the pressure reducing valve's operating state or the pressure difference across the check valve from a preset safe threshold or normal operating mode. Examples include excessively high or low outlet pressure of the pressure reducing valve, reverse pressure differences across the check valve, or severe pressure fluctuations. These thresholds and modes are typically determined through system design and preliminary testing. Once an abnormal signal is detected, the control system immediately issues a command to move the drive assembly 3 and drive block 2, thereby adjusting the throat diameter of ejector 1 to a preset safe opening. The safe opening can be one that minimizes hydrogen flow to avoid excessive hydrogen co-doping, or it can be a complete closure of the throat to completely cut off the hydrogen supply and eliminate potential risks. While performing safety adjustments, the system will issue alarms to operators through audible and visual alarms, control interface displays, and remote notifications, indicating potential safety hazards that require immediate attention and handling. It can monitor the operational status of critical safety components in the low-pressure hydrogen pipeline in real time. When the pressure reducing valve or check valve malfunctions, the system can quickly identify and trigger an emergency response, automatically adjusting the adjustable throat nozzle to a safe opening or closing state. This effectively avoids potential dangers such as uncontrolled hydrogen blending ratios and natural gas backflow caused by abnormal hydrogen supply. Simultaneously, the alarms promptly remind operators, ensuring rapid manual intervention in emergencies. This greatly improves the operational safety and reliability of the entire pipeline natural gas hydrogen blending unit, effectively preventing accidents and ensuring the safety of personnel and equipment.

[0052] When there is a significant deviation between the actual hydrogen doping ratio and the target hydrogen doping ratio, the system will return to the initial step for recalculation and adjustment. However, this simple iterative approach may result in slow convergence of the control process, or difficulty in quickly and accurately stabilizing the hydrogen doping ratio at the target value when faced with external disturbances, thus affecting the efficiency and stability of hydrogen doping. The iterative adjustment in step S9 includes: correcting the target hydrogen doping ratio in the calculation formula for the target throat diameter in the next round of calculation based on the direction and magnitude of the deviation between the actual and target hydrogen doping ratios. .

[0053] In the hydrogen doping ratio control method, iterative adjustment is the key to achieving precise control. It refers to the process of correcting the control parameters or process after one control cycle is completed, based on the difference between the actual operating state of the current system and the target state, in order to get closer to the target in the next cycle. This cyclic feedback mechanism ensures that the system can gradually eliminate errors and achieve the preset control accuracy.

[0054] This feature refers to the fact that during each iteration, the system accurately calculates the difference between the current actual hydrogen doping ratio and the preset target hydrogen doping ratio, including the absolute value of the deviation and whether the actual value is higher or lower than the target value. The acquisition of this deviation information is the basis for effective feedback control. It provides a clear basis for subsequent corrections, enabling the system to know the degree and direction of the current deviation from the target, and thus make targeted adjustments.

[0055] This correction mechanism is the core innovation of this implementation. It no longer simply reuses the initially set target hydrogen doping ratio for calculation, but dynamically adjusts the target hydrogen doping ratio used to calculate the target throat diameter in step S3 based on the deviation between the actual hydrogen doping ratio in the previous round and the target hydrogen doping ratio. Specific correction methods may include, but are not limited to: multiplying the deviation Δx by a proportional coefficient and then adding the correction amount to the original target hydrogen doping ratio; or considering the cumulative effect of historical deviations and adding the integral term of the deviation to the correction; or considering the rate of change of the deviation to predict future trends and accelerate the response speed. In this way, the system can adaptively adjust its internal target parameters according to the real-time control effect, thereby guiding the entire control process to converge to the final desired hydrogen doping ratio faster and more accurately.

[0056] Through the above technical solution, this application no longer simply repeats the initially set target hydrogen doping ratio for iterative calculation. Instead, it dynamically corrects the target hydrogen doping ratio used in the next round of calculation based on the direction and magnitude of the deviation between the actual hydrogen doping ratio and the target hydrogen doping ratio. This adaptive correction mechanism enables the control system to respond more intelligently to actual working conditions, significantly accelerates the convergence speed of the hydrogen doping ratio, and improves the accuracy and stability of control. Even in the presence of external disturbances or small changes in system parameters, this method can effectively reduce oscillations and ensure that the hydrogen doping ratio can quickly and smoothly reach and maintain the preset target value, thereby improving the efficiency and reliability of the entire hydrogen doping process.

[0057] In some of the embodiments described above in this application, the precise control of the hydrogen blending ratio is highly dependent on the accurate acquisition of the natural gas inlet pressure P1, the ejector throat pressure P2, and the hydrogen source pressure P3. However, in actual operation, the pressure sensor may experience zero-point drift or initial measurement error due to environmental changes, long-term use, or its own characteristics, resulting in inaccurate pressure data. Such inaccurate pressure data will directly affect the subsequent calculation of the target throat diameter and the evaluation of the actual hydrogen blending ratio, thereby reducing the accuracy and stability of the hydrogen blending ratio control, and may even cause the system to fail to achieve the expected hydrogen blending effect.

[0058] To address this, this application further proposes that, prior to step S2, zero-point calibration be performed on the pressure sensors used to collect P1, P2, and P3 under a no-flow condition. Specifically, a no-flow condition refers to a situation where neither natural gas nor hydrogen flows through ejector 1, or the pipeline is in a static, isolated state. Under this condition, there is no dynamic pressure or pressure drop caused by gas flow within the pipeline, and the pressure values ​​measured by the pressure sensors should be static pressures or their inherent zero-point offset. Zero-point calibration of the pressure sensors used to collect P1, P2, and P3 is a crucial step in ensuring the accuracy of the pressure sensor measurements. Under a no-flow condition, the system will read the natural gas inlet pressure from the P1 sensor and the ejector throat pressure. The output values ​​of the force sensor P2 and the hydrogen source pressure sensor P3 should ideally correspond to zero pressure difference or a certain reference pressure, which can be atmospheric pressure. If the actual reading deviates from the theoretical zero point, the sensor output values ​​are corrected to the correct zero point through software compensation or hardware adjustment. For example, the sensor reading under the current no-flow condition can be recorded as the zero-point offset, and this offset can be subtracted from the sensor reading in subsequent actual measurements to obtain a more accurate pressure value. This process ensures that all pressure measurements are based on an accurate reference during the subsequent hydrogen blending ratio control process, thereby avoiding systematic deviations introduced by sensor zero-point errors.

[0059] By performing zero-point calibration on the pressure sensor under no-flow conditions, the inherent zero-point drift and initial measurement error of the pressure sensor can be effectively eliminated or significantly reduced. This makes the acquisition data of natural gas inlet pressure P1, ejector throat pressure P2, and hydrogen source pressure P3 more accurate and reliable in the subsequent hydrogen blending ratio control method. Based on this high-precision pressure data, the system can obtain more accurate calculation results when calculating the target throat diameter. At the same time, it can also obtain an evaluation closer to the true value when calculating the actual hydrogen blending ratio. Therefore, the adjustment of the ejector throat diameter by the drive component 3 will be more precise, thereby ensuring that the actual hydrogen blending ratio can converge to the target hydrogen blending ratio quickly and stably. This significantly improves the accuracy and response speed of the hydrogen blending ratio control, reduces the number of iterative adjustments, and improves the operating efficiency and reliability of the entire hydrogen blending device.

[0060] Pressure or flow fluctuations in high-pressure natural gas pipelines can cause changes in the pressure input value P1. If not responded to in a timely manner, this will affect the accuracy of the target throat diameter calculation, leading to a deviation of the actual hydrogen blending ratio from the target hydrogen blending ratio, thus reducing the stability and response speed of the hydrogen blending ratio control. To address this, this application further proposes a flow adaptive step, which includes real-time monitoring of pressure or flow fluctuations in the high-pressure natural gas pipeline; when the fluctuation exceeds a set threshold, adjusting the pressure input value used to calculate the target adjustment parameter in step S2 in advance or synchronously to compensate for the impact of upstream fluctuations on the stability of the hydrogen blending ratio.

[0061] Specifically, real-time monitoring of pressure or flow fluctuations in high-pressure natural gas pipelines refers to continuously acquiring natural gas pressure or flow data by installing corresponding sensors on the high-pressure natural gas pipeline connected to ejector 1. For example, a high-precision pressure sensor can be deployed to measure the natural gas inlet pressure P1 in real time, or a flow meter can be deployed to measure the natural gas flow rate in real time. These sensors will continuously send data to the control system, which will analyze this real-time data according to a preset algorithm to determine whether there are significant pressure or flow fluctuations. Fluctuation judgment can be based on a comparison of the current value with the historical average, a set benchmark value, or values ​​at adjacent time points. When the deviation or rate of change exceeds a preset threshold, it is considered that a fluctuation has occurred.

[0062] When fluctuations exceed a set threshold, the system triggers a corresponding compensation mechanism. This mechanism aims to adjust the pressure input value used in step S2 to calculate the target adjustment parameter in advance or synchronously. The target adjustment parameter here mainly refers to the target throat diameter calculated in step S3, while the pressure input value specifically refers to the natural gas inlet pressure P1, which is most affected by upstream fluctuations. Advance adjustment means that the system may correct the input value of P1 before the actual fluctuation fully reaches ejector 1, based on the prediction of upstream fluctuation trends, such as by analyzing historical data or receiving early warning signals from the upstream control system. Synchronous adjustment means that once a fluctuation is detected, the system will immediately use the latest fluctuation-corrected P1 value or re-acquire the current P1 value and use it as the input for step S2, thereby immediately starting the subsequent target throat diameter calculation and adjustment process, instead of waiting for the next regular sampling cycle.

[0063] By employing the aforementioned technical solution, pressure or flow fluctuations in high-pressure natural gas pipelines are monitored in real time. When fluctuations exceed a set threshold, the pressure input value used to calculate the target adjustment parameters is adjusted in advance or synchronously. This application can effectively address dynamic changes in the upstream natural gas supply, ensuring that the calculation of the target throat diameter is always based on the latest natural gas inlet pressure P1. This makes the adjustment of the ejector 1 throat diameter more accurate and timely. Therefore, even in the case of fluctuations in the high-pressure natural gas pipeline, the stability and response speed of the hydrogen blending ratio control can be significantly improved, reducing the deviation between the actual hydrogen blending ratio and the target hydrogen blending ratio, and reducing the frequency of iterative adjustments by the system. This ensures precise control of the hydrogen blending ratio and reliable operation of the system.

[0064] The aforementioned hydrogen blending ratio control method achieves precise hydrogen blending ratio control by real-time acquisition of pressure parameters and iterative adjustment of the throat diameter of ejector 1. However, in actual operation, the system may face unforeseen circumstances such as sensor failure, communication interruption, or abnormality of drive component 3. These abnormalities may lead to inaccurate or missing acquisition of pressure signals P1, P2, and P3, resulting in deviations in the calculation of the target throat diameter and the adjustment commands of drive component 3, or even system runaway, causing significant fluctuations in the hydrogen blending ratio, thereby affecting the safety and stability of pipeline natural gas transportation.

[0065] In response, this application further proposes a hydrogen blending ratio control method that can take safety measures when an abnormal situation is detected. Specifically, when the system detects that the pressure signal exceeds the preset threshold range, that is, the real-time monitoring value of the natural gas inlet pressure P1, the ejector throat pressure P2, or the hydrogen source pressure P3 deviates from the preset normal operating range, such as the sensor output value being too high or too low, the system will determine it as abnormal. In addition, if the change rate of the pressure signal exceeds the set threshold, that is, the pressure value changes drastically in a very short time, exceeding the maximum rate of change allowed by the system, this may indicate a sudden failure in the pipeline or sensor. At the same time, if the system fails to receive a valid pressure signal within the expected time, that is, pressure signal loss occurs, this is usually due to sensor or communication link failure. Furthermore, when the drive component 3 drives the ring block 2 to move to adjust the throat diameter, if the drive component 3 fails to complete the command action and return a feedback signal within the preset time, that is, the drive component 3 response timeout occurs, this indicates that the drive component 3 may have mechanical jamming or electrical failure.

[0066] Once any of the above-mentioned abnormalities are detected, the system will immediately stop actively adjusting the throat diameter of ejector 1 and maintain the position of ring 2 at the time of the abnormality, thereby keeping the current throat diameter unchanged. This is to avoid making incorrect adjustments under uncertain or erroneous data input, preventing further deterioration of the system. At the same time, the system will trigger an audible and visual alarm, promptly reminding operators to pay attention to the system abnormality by emitting sound and / or displaying visual warning information, so as to carry out manual intervention or troubleshooting. More importantly, by maintaining the current throat diameter and other measures, the system will switch the hydrogen blending ratio to a preset safe range. This safe range is predetermined based on system design and safety specifications, aiming to ensure that even under abnormal operating conditions, the hydrogen blending ratio in pipeline natural gas can be maintained at a level that is safe for pipeline transportation and downstream gas-using equipment, thereby avoiding potential safety hazards.

[0067] Through the above technical solution, this application introduces a comprehensive abnormal operating condition monitoring and safety response mechanism into the pipeline natural gas hydrogen blending ratio control method. When the pressure sensor malfunctions, signal transmission is interrupted, or the drive component 3 responds abnormally, the system can quickly identify these potential dangerous situations. By immediately stopping active adjustment and maintaining the current throat diameter of ejector 1, it effectively avoids improper adjustment driven by erroneous or incomplete data, thereby preventing drastic fluctuations or loss of control in the hydrogen blending ratio. At the same time, triggering audible and visual alarms can promptly notify operators for intervention. More importantly, by switching the hydrogen blending ratio to a preset safe range, even in abnormal system conditions, the safety of pipeline natural gas transportation can be ensured, avoiding safety hazards or equipment damage caused by excessively high or low hydrogen blending ratios, greatly improving the reliability and safety of the entire hydrogen blending device.

[0068] When the system is started up or the target hydrogen doping ratio changes significantly, if an accurate initial adjustment parameter is lacking, the control system may take a long time to converge to the target value. This will affect the rapid stabilization of the hydrogen doping ratio and the system's response efficiency. Therefore, during the start-up phase or when the target hydrogen doping ratio changes, the initial value of the target throat diameter is calculated based on the ideal inviscid flow model of subsonic compressible gas, and the initial value is used as the starting diameter of the target throat diameter.

[0069] The system needs to establish a stable hydrogen-blended flow field from scratch. When the target hydrogen blending ratio changes, it means that the operator or the automated control system adjusts the preset blending ratio of hydrogen and natural gas according to actual needs. In both cases, it is crucial to quickly and accurately adjust the throat diameter of ejector 1 to a state close to the target value to improve the system response speed and avoid initial fluctuations.

[0070] The ideal inviscid flow model based on subsonic compressible gas is a widely used theoretical model in fluid mechanics to describe the flow characteristics of gas when the flow velocity is below the speed of sound and internal friction is neglected. This model can establish the physical relationship between gas pressure P1, P2, P3, flow velocity, flow rate, and the throat diameter of ejector 1. By using this model, based on the current gas inlet pressure P1, ejector throat pressure P2, hydrogen source pressure P3, and the set target hydrogen doping ratio, an initial estimate of the throat diameter of ejector 1 that can theoretically achieve the hydrogen doping ratio can be derived.

[0071] The initial value of the target throat diameter is calculated using the aforementioned ideal inviscid flow model, combined with real-time or preset pressure parameters, to determine the throat diameter that, under current operating conditions, allows the actual hydrogen doping ratio to approach the target hydrogen doping ratio. This calculation process provides a scientific and efficient starting point for subsequent precise adjustments. Subsequently, this calculated initial value is used as the initial diameter of the target throat. This means that in step S3 of the hydrogen doping ratio control method, when calculating the target throat diameter for the first time, this model-predicted initial value will be directly used, rather than starting from a default value or the previous operating state value. Therefore, when the hydrogen doping device is started or the target throat diameter is determined, this initial value will be used directly. When the target hydrogen blending ratio changes, the control system no longer needs to gradually approach the target throat diameter through multiple iterative trial and error. Instead, due to the use of initial value calculation based on a physical model, the initial adjustment of the ejector 1 throat diameter can reach a state very close to the ideal operating point. This significantly shortens the time required for the system to go from startup or target change to stable operation, improves the response speed and regulation efficiency of the hydrogen blending ratio control, and effectively suppresses large fluctuations in the hydrogen blending ratio that may occur during the transition phase due to the accuracy of the initial adjustment. This ensures the stability and safety of the pipeline natural gas hydrogen blending process and reduces the impact on downstream gas-using equipment.

[0072] The drive assembly 3 includes a telescopic motor 301 and a push rod 302 driven by the telescopic motor 301. In step S5, by controlling the number of rotations and direction of the telescopic motor 301, the linear displacement of the push rod 302 is controlled. The linear displacement of the push rod 302 drives the ring block 2 to move. The drive assembly 3 is responsible for driving the ring block 2 to move, thereby changing the throat diameter of the ejector 1. In order to achieve precise hydrogen doping ratio control, the drive assembly 3 needs to have high precision, high response speed, and good repeatability. The telescopic motor 301 is a motor that can generate linear motion, or a motor that converts rotational motion into linear motion through an internal mechanism. The telescopic motor 301 can provide a stable and controllable driving force, which is essential for achieving precise control of the ring block 2. Based on accurate displacement, push rod 302 is a mechanical transmission component connecting telescopic motor 301 and ring block 2. One end of push rod 302 is pivotally connected to ring block 2. Its function is to directly transmit the linear displacement generated by telescopic motor 301 to ring block 2 to ensure that no deformation occurs during the driving process, thereby ensuring the accuracy of displacement transmission. The design of push rod 302 should consider its connection method with ring block 2 to ensure a firm connection and smooth transmission of thrust. Controlling the number of rotations and direction of telescopic motor 301 is the core control strategy to achieve precise linear displacement of push rod 302. For stepper motors, by accurately calculating and sending the required number of pulses, the number of rotations can be controlled, thereby controlling the displacement of push rod 302.By changing the direction of the pulse sequence, the rotation direction of the motor can be controlled, thereby controlling the extension and retraction direction of the push rod 302. For servo motors, a high-precision encoder monitors the motor rotation angle in real time and compares it with the target position. Closed-loop adjustment is performed using PID or other control algorithms to ensure that the motor rotates precisely to the specified number of revolutions and direction. This control method can convert the rotational accuracy of the motor into the linear displacement accuracy of the push rod 302. The linear displacement of the push rod 302 is a key parameter that directly affects the throat diameter of the ejector 1. By precisely controlling the number of revolutions and direction of the telescopic motor 301, centimeter-level, millimeter-level, or even micrometer-level precise control of the linear displacement of the push rod 302 can be achieved. This precise linear displacement control is the basis for ensuring that the throat diameter of the ejector 1 can be accurately adjusted to the target throat diameter. The linear displacement of the push rod 302 directly acts on the ring block 2, causing it to move linearly along the preset guide mechanism. The movement of the ring block 2 changes the geometry of the throat of the ejector 1, thereby adjusting... The flow area at the throat and the connection between the push rod 302 and the ring block 2 should be designed with a low-friction, high-rigidity structure to reduce transmission errors and hysteresis, ensuring that the precise displacement of the push rod 302 can be accurately converted into the actual position of the ring block 2. The telescopic motor 301, combined with the drive method of the push rod 302, can provide stable, repeatable, and high-precision linear displacement, effectively solving the problems of inaccurate positioning, slow response, or poor repeatability that may exist in traditional drive components 3. Specifically, by precisely controlling the number of rotations of the telescopic motor 301, the linear displacement of the push rod 302 can be finely adjusted, so that the throat diameter of the ejector 1 can be accurately adjusted to the calculated target value. This significantly improves the accuracy and stability of the throat diameter adjustment in the hydrogen blending ratio control method, thereby ensuring that the actual hydrogen blending ratio can more closely track the target hydrogen blending ratio, reducing the number of iterative adjustments, improving the system's response speed and control accuracy, and ultimately ensuring the stability and economy of the pipeline natural gas hydrogen blending process.

Claims

1. A method for controlling the hydrogen blending ratio in a pipeline natural gas hydrogen blending device, the device comprising an ejector with an adjustable throat nozzle, the ejector comprising a ring block for adjusting the throat diameter and a drive assembly for moving the ring block, wherein the throat diameter of the adjustable throat nozzle is adjusted by the drive assembly moving the ring block, characterized in that... The method Includes the following steps: S1: Set the target hydrogen doping ratio S2: Natural gas inlet pressure is collected. ejector throat pressure Hydrogen source pressure S3: Based on the target hydrogen doping ratio Natural gas inlet pressure ejector throat pressure and hydrogen source pressure S4: Calculate the target throat diameter using a pre-established and calibrated fluid dynamics model; S5: Calculate the target movement distance of the ring block driven by the drive assembly based on the pre-stored ejector geometry and target throat diameter; S6: Control the drive assembly to drive the ring block to move the target movement distance, adjusting the ejector throat diameter to match the target throat diameter. ； S6: Collect adjusted natural gas inlet pressure ejector throat pressure Hydrogen source pressure And based on the actual moving distance of the drive component, obtain the current throat diameter. ； S7: Based on the current throat diameter Query the preset throat diameter and flow area mapping table to obtain the hydrogen channel flow area. and natural gas channel circulation area S8: Based on the preset flow coefficients of hydrogen and natural gas, the density parameters of hydrogen and natural gas, the flow area of ​​the corresponding channels for hydrogen and natural gas, and the adjusted inlet pressure of natural gas. ejector throat pressure Hydrogen source pressure The actual hydrogen doping ratio is obtained by using a preset mass flow rate-based hydrogen doping ratio calculation model for each pressure parameter. S9: Calculate the actual hydrogen doping ratio Compared with the target hydrogen doping ratio deviation Determine the deviation Check if the deviation is less than the preset allowable error threshold. If the absolute value of the deviation does not exceed the preset threshold, maintain the current adjustment state. If the absolute value of the deviation exceeds the preset hydrogen doping ratio deviation threshold, return to step S2 for iterative adjustment.

2. The hydrogen doping ratio control method according to claim 1, characterized in that, The hydrogen doping ratio Defined as the ratio of hydrogen mass flow rate to natural gas mass flow rate: ,in, This represents the hydrogen mass flow rate. This refers to the mass flow rate of natural gas.

3. The hydrogen doping ratio control method according to claim 1, characterized in that, The mapping table between throat diameter and flow area was established through calibration experiments: under fixed operating conditions, the flow area of ​​the hydrogen channel corresponding to different throat diameters was measured. Area of ​​natural gas channel And store.

4. The hydrogen doping ratio control method according to claim 1, characterized in that, The method also includes a safety monitoring step: continuously monitoring the working status of the pressure reducing valve and / or the pressure difference across the check valve on the low-pressure hydrogen pipeline connected to the ejector; when an abnormal signal is detected, controlling the drive mechanism to adjust the adjustable throat nozzle to a safe opening or closed state and issuing an alarm.

5. The hydrogen doping ratio control method according to claim 1, characterized in that, The iterative adjustment in step S9 includes: correcting the target hydrogen doping ratio in the calculation formula for the target throat diameter in the next round based on the direction and magnitude of the deviation between the actual hydrogen doping ratio and the target hydrogen doping ratio.

6. The hydrogen doping ratio control method according to claim 1, characterized in that, Before step S2, the pressure at the natural gas inlet is collected under no-flow conditions. ejector throat pressure Hydrogen source pressure Zero-point calibration is performed on the pressure sensor.

7. The hydrogen doping ratio control method according to claim 1, characterized in that, The method further includes a flow adaptive step: real-time monitoring of pressure or flow fluctuations in the high-pressure natural gas pipeline; when the fluctuation exceeds a set threshold, adjusting the pressure input value used to calculate the target adjustment parameter in step S2 in advance or synchronously to compensate for the impact of upstream fluctuations on the stability of the hydrogen doping ratio.

8. The method for controlling the hydrogen doping ratio according to claim 1, characterized in that, When the pressure signal exceeds the preset threshold range, the pressure signal mutation rate exceeds the set threshold, or the pressure signal is lost, or the drive component response times out, the current throat diameter is maintained, an audible and visual alarm is triggered, and the hydrogen doping ratio is switched to the preset safe range.

9. The hydrogen doping ratio control method according to claim 1, characterized in that, During the startup phase or when the target hydrogen doping ratio changes, the target throat diameter is calculated based on an ideal inviscid flow model of subsonic compressible gas. The initial value is used as the starting diameter of the target throat diameter.

10. The method for controlling the hydrogen doping ratio according to claim 1, characterized in that, The drive assembly includes a telescopic motor and a push rod driven by the telescopic motor; in step S5, the linear displacement of the push rod is controlled by controlling the number of rotations and direction of the telescopic motor, and the linear displacement of the push rod drives the ring block to move.

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