Flow distribution system and method for water-cooled wall intermediate header of ultra-supercritical coal-fired unit

Abstract

The invention discloses a water-cooled wall intermediate header flow distribution system of an ultra-supercritical coal-fired unit, which comprises an intermediate header and a collection header, a three-stage adjustable throttling orifice plate is arranged in an inlet pipeline of the intermediate header, a plurality of groups of cyclone flow deflectors are arranged in the intermediate header, the intermediate header is communicated with the collection header through a plurality of branch pipes, and the branch pipes are communicated with the collection header. The inlet of each branch pipe is provided with a Venturi pipe, and the outlet of each branch pipe is provided with a sensor probe of the control unit; the three-stage adjustable throttling orifice plate and the cyclone flow deflector are respectively in transmission connection with respective actuating mechanisms, and all the actuating mechanisms are in signal connection with the control unit. The invention further discloses a water-cooled wall intermediate header flow distribution method of the ultra-supercritical coal-fired unit. The invention belongs to the technical field of ultra-supercritical coal-fired power generation, and solves the problem that in the prior art, due to the limitation of structural design, the wide load range adjustment requirement cannot be met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultra-supercritical coal-fired power generation, and relates to a water-cooled wall intermediate header flow distribution system of an ultra-supercritical coal-fired unit. BACKGROUND

[0002] When an ultra-supercritical coal-fired power generation unit is deeply regulated to a low load, for example, to below 30% THA, the water-cooled wall working fluid flow is reduced, and the pressure difference is lowered, which easily leads to serious imbalance of working fluid distribution between parallel branch pipes of the intermediate header. This phenomenon not only causes local thermal deviation and heat transfer deterioration, but also may cause film boiling risk due to working fluid phase change, directly threatening the safety and economy of the unit. Although the currently widely used fixed throttle ring or distributor can achieve balanced flow distribution under the design condition (high load), the distribution effect is deteriorated under the low load condition due to the obvious change in flow-pressure difference characteristics, and cannot be self-adaptively adjusted. At the same time, the two-phase flow pattern in the intermediate header changes (such as stratified flow) under the low flow speed condition, further destroying the flow uniformity between branch pipes. Therefore, the core defect of the prior art is that it cannot adapt to the regulation requirement in a wide load range, lacks active regulation ability for the complex flow field in the header, and cannot dynamically compensate in combination with real-time thermal load distribution feedback, finally forming a vicious cycle of "flow distribution imbalance-thermal deviation accumulation-heat transfer deterioration".

[0003] Therefore, it is urgent to develop a water-cooled wall intermediate header flow distribution optimization system and method which has wide load adaptability and active intervention ability. SUMMARY

[0004] The application aims to provide a water-cooled wall intermediate header flow distribution system of an ultra-supercritical coal-fired unit, and solves the problem in the prior art that the structural design limitation leads to the inability to adapt to the regulation requirement in a wide load range.

[0005] Another object of the application is to provide a water-cooled wall intermediate header flow distribution method of an ultra-supercritical coal-fired unit, and solves the problem in the prior art that it cannot adapt to the regulation requirement in a wide load range, lacks active regulation ability for the complex flow field in the header, and cannot dynamically compensate in combination with real-time thermal load distribution feedback.

[0006] The technical solution adopted in this invention is a water-cooled wall intermediate header flow distribution system for ultra-supercritical coal-fired power units, comprising an intermediate header and a converging header. A three-stage adjustable orifice plate is installed in the inlet pipe of the intermediate header. Multiple sets of swirling guide vanes are installed inside the intermediate header. The intermediate header is connected to the converging header via multiple branch pipes. A Venturi tube is installed at the inlet of each branch pipe, and a sensor probe for the control unit is arranged at the outlet of each branch pipe. The three-stage adjustable orifice plate and the swirling guide vanes are respectively connected to their respective actuators via transmission. All actuators are signal-connected to the control unit.

[0007] Another technical solution adopted in this invention is a method for distributing the flow of the intermediate header of the water-cooled wall in an ultra-supercritical coal-fired power unit, which is implemented according to the following steps: Step 1: Collect data in real time. Step 2: The fuzzy PID controller in the control unit calculates the deviation based on the data collected in real time in Step 1 and determines whether to adjust it. When the flow deviation index △ Q If the percentage is ≤5%, the fuzzy PID controller confirms that no adjustment is needed and returns to step 1 to implement a new round of data acquisition. When the flow deviation index △ Q When the percentage is >5%, proceed to step 3; Step 3: The fuzzy PID controller determines the magnitude of the adjustment. Step 4: After receiving the adjustment command from the control unit, the actuator performs the adjustment operation. Step 5: The control unit re-acquires relevant data until △ Q ≤5%, completing one cycle of optimization and adjustment.

[0008] The beneficial effect of this invention is that, through the synergistic mechanism of "active structural intervention + dynamic closed-loop control", it solves the technical bottlenecks of poor wide-load adaptability, two-phase flow pattern instability and thermal feedback lag of traditional fixed throttling devices, and significantly improves the flow uniformity and operational safety of ultra-supercritical units under low-load conditions. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the overall process of the method of the present invention; Figure 2 This is a schematic diagram of the structure of two primary orifice plates in the three-stage adjustable flow orifice plate system of the present invention; Figure 3 This is a schematic diagram of the structure of two secondary orifice plates in the three-stage adjustable flow orifice plate system of the present invention; Figure 4 This is a schematic diagram of the structure of two final-stage orifice plates in the three-stage adjustable orifice plate system of the present invention; Figure 5This is a schematic diagram of the rotating shaft assembly of the three-stage adjustable flow orifice plate in the system of the present invention; Figure 6 This is a schematic diagram of the assembly of the swirl guide vane and the rotating shaft in the system of the present invention; Figure 7 This is a schematic diagram of the Venturi tube in the system of the present invention; Figure 8 This is a flowchart of the control unit logic in the method of the present invention.

[0010] In the diagram, 1. Three-stage adjustable flow orifice plate, 2. Swirl guide vane, 3. Venturi tube, 4. Branch pipe, 5. Control unit, 6. Intermediate header, 7. Collecting header, 8. V-shaped guide channel, 11. First-stage orifice plate, 12. Second-stage orifice plate, 13. Last-stage orifice plate, 14. Rotating shaft one, 15. Inlet pipe, 16. Rotating shaft two. Detailed Implementation

[0011] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0012] The structural improvements of the system of the present invention include the following aspects: 1) A honeycomb-shaped three-stage adjustable flow perforation plate 1 is arranged in the inlet section of the intermediate header 6. Each stage of the perforation plate consists of two parts: the first part is a fixed perforation plate, and the second part is a rotatable rotating perforation plate (fixed on the rotating shaft). It is driven by a rotating motor. The number and diameter of the holes on the two perforation plates of the same stage are completely consistent, and the influence of inertial force under low flow rate is compensated in combination with load changes. 2) A swirl guide vane 2 is added inside the intermediate header 6. The tilt angle of the swirl guide vane 2 is adjusted by using a stepper motor to generate a controllable swirl to suppress the working fluid stratification and enhance mixing. 3) The inlet of branch pipe 4 adopts a venturi-type pipe 3 with a gradually narrowing-expanding structure, which improves flow stability through boundary layer reconstruction.

[0013] Reference Figure 1 The overall structure of the water-cooled wall intermediate header flow distribution system for ultra-supercritical coal-fired power units of the present invention includes an intermediate header 6 and a converging header 7. A three-stage adjustable flow orifice plate 1 is installed in the inlet pipe 15 of the intermediate header 6. Multiple sets of swirling guide vanes 2 are installed inside the intermediate header 6. The intermediate header 6 is connected to the converging header 7 through multiple branch pipes 4. A Venturi tube 3 is installed at the inlet of each branch pipe 4, and a sensor probe of the control unit 5 is arranged at the outlet of each branch pipe 4. The working fluid of the spiral water-cooled wall enters from the inlet pipe 15 of the intermediate header 6, passes through the aforementioned components, and enters the converging header 7. The three-stage adjustable flow orifice plate 1 and the swirling guide vanes 2 are respectively connected to their respective actuators, and all actuators are respectively connected to the control unit 5 via signals.

[0014] ReferenceFigure 2 , Figure 3 , Figure 4 , Figure 5 The three-stage adjustable flow orifice plate 1 consists of two primary orifice plates 11, two secondary orifice plates 12, and two final orifice plates 13. Each orifice plate consists of a fixed orifice plate and a rotating orifice plate, with identical structural specifications. The primary orifice plates 11, 12, and 13 are connected in series from inlet to outlet in the inlet pipe 15 of the intermediate header 6. The orifice diameters on the two primary orifice plates 11 range from 8 to 10 mm, with 36 orifices evenly distributed in this embodiment for basic flow distribution. The orifice diameters on the two secondary orifice plates 12 range from 6 to 8 mm, with 48 orifices evenly distributed in this embodiment for transitional rectification. The orifice diameters on the two final orifice plates 13 range from 4 to 6 mm, with 72 orifices evenly distributed in this embodiment for fine resistance control. The actuator achieves a gradient decrease in orifice diameter by rotating each rotating orifice plate (primary to final stage), forming multi-stage throttling resistance.

[0015] Reference Figure 5 Each of the first-stage orifice plate 11, the second-stage orifice plate 12, and the final-stage orifice plate 13 is individually fixed with a rotating shaft 14. Each rotating shaft 14 is individually connected to a rotating motor, and each rotating motor has its own driver. All drivers are signal-connected to the control unit 5. When the actuator receives the adjustment command from the control unit 5, the three drivers control their respective rotating motors, and the three rotating motors control the rotation of their respective first-stage rotating orifice plates. This achieves the staggered rotation of the rotating orifice plates in the three-stage orifice plates relative to the fixed orifice plates. That is, the two orifice plates in each stage are staggered, and the flow opening is controlled according to the degree of overlap, thereby achieving continuous flow control in the inlet pipe 15 of the intermediate header 6.

[0016] Reference Figure 6 The intermediate header 6 is equipped with a swirling guide vane 2 with an adjustable helix angle, ranging from 15° to 60°. The swirling guide vane 2 is mounted inside the intermediate header 6 via a rotating shaft 16. A stepper motor is mounted outside the intermediate header 6, and the rotating shaft 16 is connected to the output shaft of the stepper motor via a coupling. The stepper motor is signal-connected to the control unit 5. The surface of the swirling guide vane 2 has V-shaped guide grooves 8, with a depth of at least 3mm, which force the working fluid to form a swirling flow and suppress stratification. The control unit 5 (fuzzy PID controller) adjusts the flow rate deviation based on real-time monitoring. ΔQ and temperature gradient ΔT The required angle adjustment of the swirl guide vane 2 is calculated and then sent to the stepper motor driver in the form of an analog signal (current) to complete the actual adjustment.

[0017] Reference Figure 7Each intermediate header 6 has a branch outlet connected to the inlet of each corresponding branch pipe 4 via a Venturi tube 3. All Venturi tubes 3 have a tapered-expanding Venturi structure. The tapering angle of all Venturi tubes 3 is not less than 30° (if the tapering angle is ≥30°, the length of the tapering section should be shortened as much as possible to make the structure more compact, while ensuring that the flow does not separate severely). The expanding angle is not greater than 15° (if the expanding angle is ≤15°, flow separation is prevented to ensure stability. This is the golden rule of Venturi tube design. 15° is the upper limit, which aims to control the length of the expanding section while absolutely ensuring that the flow adheres to the wall, avoiding energy loss and vibration). This can enhance the boundary layer disturbance of the fluid, maintain the annular flow state, and suppress flow separation.

[0018] Reference Figure 8 The control unit 5 consists of multiple distributed fiber optic temperature sensors, multiple ultrasonic flow meters, a fuzzy PID controller, and an actuator. The distributed fiber optic temperature sensors and ultrasonic flow meters are all located at the outlet positions of each branch pipe 4 in the connecting collection box 7. The actuator is used to drive the three-stage adjustable flow orifice plate 1 and the swirl guide vane 2, and control the flow rate adjustment of the three-stage adjustable flow orifice plate 1 and the deflection angle adjustment of the swirl guide vane 2.

[0019] The working principle of this invention is: Each orifice plate consists of a fixed orifice plate and a rotating orifice plate (with perfectly matched orifice diameter and number). The orifice overlap is changed by adjusting the angle of the rotating orifice plate, which dynamically changes the flow area (the higher the overlap, the larger the flow area). The three orifice plates respectively undertake the functions of basic distribution, transition rectification, and fine control, adapting to the throttling resistance requirements under different loads.

[0020] The angle θ of the swirl guide vane 2 satisfies the following relationship with the main steam pressure P: , k =0.8~1.2.

[0021] The fuzzy PID controller employs enhanced parameters when the load is ≤30% THA: K p =1.0~1.5; K i =0.03~0.08; K d =0.2~0.5. When Δ Q When the value is >5%, the fuzzy PID controller synchronously generates the orifice opening command and the swirl guide vane angle command; the actuator completes the adjustment within 5 seconds until Δ Q ≤5%.

[0022] The system and method of this invention, through dynamic adjustment of throttling opening and guide angle, have been verified in a 660MW unit, reducing the minimum stable combustion load to 23% THA. Under the 23% THA load, the branch pipe flow deviation is ≤5% and the wall temperature deviation is within ±14℃, thereby improving the unit's peak-shaving safety.

[0023] The method for distributing the flow rate of the intermediate header of the water-cooled wall in an ultra-supercritical coal-fired power unit according to the present invention is implemented according to the following steps: Step 1: Real-time data acquisition. The control unit 5 uses all the distributed fiber optic temperature sensors and ultrasonic flow meters to monitor the working fluid temperature (acquired by distributed fiber optic temperature sensors) and flow rate (acquired by ultrasonic flow meters) at the outlet of each branch pipe 4 in real time. Step 2: The fuzzy PID controller in control unit 5 calculates the deviation based on the data collected in real time in step 1 and determines whether to adjust it. Define the flow deviation index △ Q The fuzzy PID controller calculates the flow deviation index in real time, and the flow deviation index Δ Q The expression is: , , In the formula, and For the maximum and minimum flow rates collected, n This indicates the total number of branch pipes 4. This is the average value of all collected traffic. When the flow deviation index △ Q If the percentage is ≤5%, the fuzzy PID controller confirms that no adjustment is needed and returns to step 1 to implement a new round of data acquisition. When the flow deviation index △ Q When the percentage is >5%, proceed to step 3; Step 3: The fuzzy PID controller determines the magnitude of the adjustment. The specific process is as follows: 1) Define the input parameters in the fuzzy PID controller K p , K i and K d , K p The proportional gain coefficient represents the strength of the system's response to the current error. K p Increasing the response speed will speed up the response, but too much of it will lead to overshoot and oscillation. K p Reduced response sluggishness leads to increased steady-state error; Under different loads Kp The correspondence between the scope and the target of action is shown in Table 1.

[0024] Table 1. Under different loads K p Scope and Objectives

[0025] K i The integral coefficient represents the ability to eliminate historical accumulated errors; K i Increasing the speed of steady-state deviation elimination can easily lead to integral saturation; K i Reducing residual steady-state error decreases adjustment accuracy; Under different loads K i The scope and technical objectives are shown in Table 2.

[0026] Table 2. Under different loads K i Scope and technical objectives

[0027] K d The differential coefficient represents the damping effect on the trend of future error changes in prediction. K d It increases overshoot suppression and improves stability, but is sensitive to noise. K d Reduce system oscillations and prolong settling time; Under different loads K d The scope and functional objectives are shown in Table 3.

[0028] Table 3. Under different loads K d Scope and functional objectives

[0029] In conclusion, K p , K i and K d These are the three core parameters of a fuzzy PID controller (proportional-integral-derivative controller). The input variable of a fuzzy PID controller is: Δ Q Temperature gradient Δ T, K p , K i and K dThe parameter settings for the fuzzy PID controller are shown in Table 4.

[0030] Table 4. Parameter settings of fuzzy PID controller under different loads

[0031] 2) The fuzzy PID controller determines the output variable of the regulating parameter: orifice opening increment Δ K , Guide angle increment △ θ , Automatically match preset values ​​based on the current load. K p , K i and K d It determines the control's response strength, error correction capability, and stability; The preprocessed input variables are converted into fuzzy sets, as shown in the expression: △ Q ∈{ NB, NM, NS, ZO, PS, PM, PB}, △ T ∈{ L, M, H}; in, NB, NM, NS, ZO, PS, PM, PB All are load types, representing negative large, negative medium, negative small, zero, positive small, positive medium, and positive large, respectively, and corresponding to the "excessive", "moderate", and "excessive" deviation states; L, M, H These represent low, medium, and high, corresponding to the "slight," "moderate," and "severe" levels of thermal deviation, respectively. Based on pre-defined expert experience rules, an adjustment strategy for the output variable is defined for different combinations of input states, initially obtaining a "fuzzy output"; for example: if △Q For "Zhengda ( PB )"and △T For "high ( H () (large flow deviation and severe thermal deviation), then △ K For "Zhengda ( PB () (significantly increase orifice opening to increase flow rate), △ θ For "the center ( PM (Increase the angle of the guide vanes to enhance the suppression of stratification of swirl).

[0032] Convert the "fuzzy output" result into precise control command values ​​△ K and △ θ The calculation is performed using the "center of gravity method": For △ K The fuzzy set of the fuzzy output variables is △ K total This is the fuzzy set generated by all triggered rules, and its membership function is:μ △Ktotal ( k Then we have: , For △ θ The fuzzy set of the fuzzy output variables is △ θ total Similarly, the fuzzy set generated by all triggered rules has the following membership function: μ △θtotal ( θ Then we have: , The above PID parameters ( K p , K i and K d They do not directly participate in the aforementioned fuzzy calculations; their role is to scale the final output or the intensity of the scaling rule trigger, thereby changing the "strength" of the control. The fuzzy PID controller outputs a precise Δ... K and △ θ It uses analog signals (current / pulse) to send to the actuator.

[0033] Step 4: After receiving the adjustment instruction, the actuator performs the adjustment operation. On the one hand, after receiving the adjustment command, the actuator controlling the three-stage adjustable flow orifice plate 1 increases the orifice plate opening by Δ. K The command is sent to the driver of the rotating motor in the form of an analog signal (current). The rotation of the motor shaft directly drives the rotating shaft 14 of the three-stage adjustable flow orifice plate 1 to rotate through the coupling, thereby realizing the operation of the three-stage adjustable flow orifice plate 1. In the initial position, the holes of the two orifice plates of the same stage are completely aligned, and the flow area is maximized. After the adjustment begins, the degree of hole misalignment determines the effective flow area. The more misaligned the holes are, the smaller the effective flow orifice is, the greater the flow resistance, and the smaller the flow rate. On the other hand, after receiving the adjustment command, the actuator controlling the swirl guide vane 2 will increase the guide angle increment Δ. θ The command is sent to the stepper motor driver in the form of an analog signal (pulse). The output shaft of the stepper motor is directly connected to the rotating shaft on the swirl guide vane 2 through a coupling. Since the swirl guide vane 2 is fixedly installed on the rotating shaft, the output shaft of the stepper motor drives the swirl guide vane 2 to rotate through the rotating shaft 16, changing the tilt angle (helix angle) of the swirl guide vane 2 relative to the fluid flow direction.

[0034] Step 5: After the adjustment in Step 4, Control Unit 5 uses all distributed fiber optic temperature sensors and ultrasonic flow meters to re-collect relevant data until △ Q≤5%, completing one cycle of optimization and adjustment.

[0035] The method of this invention has an adaptive wide load range of 20%-100% THA, achieving a branch pipe flow deviation of ≤5% under low load; eliminating steam-water stratification and maintaining stable annular flow; and improving the unit's peak-shaving response speed and safe operating lower limit.

[0036] Example 1 Unit #1 of a power plant, a 660MW ultra-supercritical unit (main steam pressure 29.3MPa), burns bituminous coal. Its application scenario involves frequent participation in deep grid peak shaving, with load fluctuating between 30% and 100% THA. The method of this invention is used to modify the flow distribution control of the water-cooled wall intermediate header of the unit.

[0037] Three-stage adjustable orifice plate coordinated control, guide vane angle range: 15°-60°, control parameter k is set to 1.0, and enhancement parameter is used at low load (≤30% THA). K p =1.2, K i =0.05, K d =0.3), and after the modification, it ran continuously for 168 hours.

[0038] After the system was put into operation, it was able to quickly suppress the flow deviation ΔQ to below 5% under various loads (adjustment action completion time < 5s). Specific data comparison is shown in Table 5 below.

[0039] Table 5. Comparison of evaluation indicators before and after the modification in Example 1

[0040] The system and method described in this invention can extend the lower limit of safe and stable operation load for 660MW units from 30% THA to 23% THA, and significantly improve the uniformity of flow distribution across the entire load range. △Q <5%) and temperature distribution (the standard deviation of wall temperature is greatly reduced), which fully meets the requirements for deep peak shaving.

[0041] Example 2 The same unit as in Example 1 is used, but only the first and last stage orifice plates are used for adjustment. The second stage transition rectifier orifice plate is omitted. The remaining components and control strategies are the same as in Example 1.

[0042] The system can still function normally, but the dynamic quality of the regulation process deteriorates during sudden load changes (such as a rapid drop from 50% THA to 35% THA). Specific data comparisons are shown in Table 6 below.

[0043] Table 6. Comparison of evaluation indicators before and after the modification in Example 2

[0044] Example 2 shows that the three-stage orifice plate structure (first-middle-last) has better dynamic response speed and stability under transition conditions compared to the two-stage structure. Although it can still work without the intermediate stage, its performance is reduced.

[0045] Example 3 Unit #2 of a power plant, a 600MW ultra-supercritical unit, burns low-quality lignite, making it more prone to flow instability at low loads. A three-stage adjustable orifice plate coordinated control system is used. In this modification, the guide vane angle adjustment range is 15°-45°, while other parameters remain unchanged.

[0046] At loads above 50% THA, the effect is comparable to that of Example 1. However, at extremely low loads (25% THA), the effect of suppressing stratification is slightly worse due to the limited agitation capability of the guide vanes. Specific data comparisons are shown in Table 7 below.

[0047] Table 7. Comparison of evaluation indicators before and after the modification in Example 3

[0048] Setting the upper limit of the guide vane angle to 60° compared to 45° offers significant advantages when dealing with extremely low loads and stratification conditions. This indicates that the 15-60° adjustable range selected in this invention is an optimized choice and not a conventional one in the art.

[0049] Example 4 A 300MW subcritical unit (main steam pressure 17.5MPa) will undergo flexibility modification, with the target minimum stable combustion load reduced to 35% THA (105MW).

[0050] A three-stage adjustable orifice plate coordinated control is adopted. Since the main steam pressure P < 25 MPa, the guide vane angle is set according to a formula. θ =22.5°, and can be dynamically adjusted by fuzzy PID within ±15°. Due to the difference in hydrodynamic characteristics of subcritical units, the parameters are adopted at low loads. K p =0.9, K i =0.04, K d =0.25.

[0051] After the modification, the lower limit of the stable combustion load of the subcritical unit was successfully reduced to 35% THA, and the low-load performance was significantly improved. Specific data comparison is shown in Table 8 below.

[0052] Table 8. Comparison of evaluation indicators before and after the modification in Example 4

[0053] This embodiment demonstrates that the system and method described in this invention have good universality and scalability. They are not only applicable to ultra-supercritical units, but also, after appropriate parameter adaptation, can effectively improve the peak-shaving capacity and operational safety of subcritical units.

[0054] Example 5 The example is a 1000MW ultra-supercritical double reheat unit, which has extremely high requirements for peak-shaving performance and operational safety, and aims to achieve stable combustion at ultra-low load with 20% THA.

[0055] Three-stage adjustable orifice plate coordinated control, guide vane angle range: 15°-60°, control parameter k is set to 1.0, and enhancement parameter is used at low load (≤30% THA). K p =1.2, K i =0.05, K d =0.3), the unit operated safely and continuously for 4 hours at 20% THA load, and all parameters remained stable. Specific data comparisons are shown in Table 9 below.

[0056] Table 9. Comparison of evaluation indicators before and after the modification in Example 5

[0057] This embodiment applies the invention to the current largest capacity 1000MW unit and successfully achieves safe operation at ultra-low load with 20% THA. Example 6 The example described is a 350MW supercritical coal-fired unit that burns bituminous coal and operates under frequent peak-shaving conditions, requiring safe operation under low loads. The system and method of this invention are used to modify the unit.

[0058] Three-stage adjustable orifice plate coordinated control, guide vane angle range: 15°-60°, control parameter k is set to 1.0, and enhancement parameter is used at low load (≤30% THA). K p =1.2, K i =0.05, K d =0.3).

[0059] The specific data comparison under various loads before and after the system was put into operation is shown in Table 10 below.

[0060] Table 10. Comparison of evaluation indicators before and after the modification in Example 6

[0061] It significantly improves the uniformity of flow distribution (ΔQ<5%) and the standard deviation of wall temperature across the entire load range, making it suitable for safe operation under frequent peak shaving requirements.

Claims

1. A water-cooled wall intermediate header flow distribution system for an ultra-supercritical coal-fired unit, comprising an intermediate header (6) and a collection header (7), characterized in that: A three-stage adjustable flow orifice plate (1) is installed in the inlet pipe (15) of the intermediate header (6). Multiple sets of swirling guide vanes (2) are installed inside the intermediate header (6). The intermediate header (6) is connected to the collection header (7) through multiple branch pipes (4). A venturi tube (3) is installed at the inlet of each branch pipe (4). A sensor probe of the control unit (5) is arranged at the outlet of each branch pipe (4). The three-stage adjustable flow orifice plate (1) and the swirling guide vanes (2) are respectively connected to their respective actuators. All actuators are connected to the control unit (5) via signals.

2. The water-cooled wall intermediate header flow distribution system for ultra-supercritical coal-fired power units according to claim 1, characterized in that, The three-stage adjustable flow orifice plate (1) is divided into two first-stage orifice plates (11), two second-stage orifice plates (12) and two last-stage orifice plates (13). Each orifice plate consists of a fixed orifice plate and a rotating orifice plate. The fixed orifice plate and the rotating orifice plate in each orifice plate have the same structural specifications. The first-stage orifice plate (11), the second-stage orifice plate (12) and the last-stage orifice plate (13) are connected in series from the inlet to the outlet in the inlet pipe (15) of the intermediate header (6). Each of the first-stage orifice plate (11), the second-stage orifice plate (12) and the final-stage orifice plate (13) is individually fixed with a rotating shaft (14), and each rotating shaft (14) is individually connected to a rotary motor, and each rotary motor is equipped with its own driver.

3. The water-cooled wall intermediate header flow distribution system for ultra-supercritical coal-fired units according to claim 1, characterized in that, The intermediate header (6) is provided with a swirling guide vane (2), and the surface of the swirling guide vane (2) has a V-shaped guide groove (8). The swirling guide vane (2) is installed inside the intermediate header (6) through a rotating shaft 16. The stepper motor is installed outside the intermediate header (6). The rotating shaft 16 is driven and connected to the output shaft of the stepper motor through a coupling. The stepper motor is signal connected to the control unit (5).

4. The water-cooled wall intermediate header flow distribution system for ultra-supercritical coal-fired units according to claim 1, characterized in that, The control unit (5) consists of multiple distributed fiber optic temperature sensors, multiple ultrasonic flow meters, a fuzzy PID controller and an actuator; the distributed fiber optic temperature sensors and ultrasonic flow meters are all located at the outlet of each branch pipe (4) of the connecting collection box (7); the actuator is used to drive the three-stage adjustable flow orifice plate (1) and the swirl guide plate (2).

5. A method for distributing the flow rate of the intermediate header of the water-cooled wall in an ultra-supercritical coal-fired power unit, characterized in that, Follow these steps: Step 1: Collect data in real time. Step 2: The fuzzy PID controller in the control unit (5) calculates the deviation based on the data collected in real time in step 1 and determines whether to adjust. When the flow deviation index △ Q If the percentage is ≤5%, the fuzzy PID controller confirms that no adjustment is needed and returns to step 1 to implement a new round of data acquisition. When the flow deviation index △ Q When the percentage is >5%, proceed to step 3; Step 3: The fuzzy PID controller determines the magnitude of the adjustment. Step 4: After receiving the adjustment command from the control unit (5), the actuator performs the adjustment operation. Step 5: The control unit (5) re-acquires relevant data until △ Q ≤5%, completing one cycle of optimization and adjustment.

6. The method for distributing the flow rate of the intermediate header of the water-cooled wall in an ultra-supercritical coal-fired unit according to claim 5, characterized in that, In step 1, the specific process is as follows: The control unit (5) uses all distributed fiber optic temperature sensors and ultrasonic flow meters to monitor the working fluid temperature and flow rate at the outlet of each branch pipe (4) in real time.

7. The method for distributing the flow rate of the intermediate header of the water-cooled wall in an ultra-supercritical coal-fired unit according to claim 5, characterized in that, Step 2, the specific process is as follows: Define the flow deviation index △ Q The fuzzy PID controller calculates the value of the flow deviation index in real time, and the flow deviation index Δ Q The expression is: ， ， In the formula, and For the maximum and minimum flow rates collected, n This indicates the total number of branch pipes (4). This is the average value of all collected traffic.

8. The method for distributing the flow rate of the intermediate header of the water-cooled wall in an ultra-supercritical coal-fired unit according to claim 5, characterized in that, Step 3, the specific process is as follows: 1) Define the input parameters in the fuzzy PID controller K p , K i and K d , K p The proportional gain coefficient represents the strength of the system's response to the current error. K i The integral coefficient represents the ability to eliminate historical accumulated errors; K d The differential coefficient represents the damping effect on the trend of future error changes in prediction; 2) The fuzzy PID controller determines the output variable of the regulating parameter: orifice opening increment Δ K , Guide angle increment △ θ , The preprocessed input variables are converted into fuzzy sets, as shown in the expression: △ Q ∈{ NB, NM, NS, ZO, PS, PM, PB}， △ T ∈{ L, M, H}； in, NB, NM, NS, ZO, PS, PM, PB All are load types, representing negative large, negative medium, negative small, zero, positive small, positive medium, and positive large, respectively, and corresponding to the "excessive", "moderate", and "excessive" deviation states; L, M, H These represent low, medium, and high, corresponding to "slight," "moderate," and "severe" levels of thermal deviation, respectively. Based on preset rules, an adjustment strategy for the output variable is defined for different combinations of input states, initially obtaining a "fuzzy output"; the result of the "fuzzy output" is then converted into a precise control command value Δ. K and △ θ The calculation is performed using the "center of gravity method": For △ K The fuzzy set of the fuzzy output variables is △ K total This is the fuzzy set generated by all triggered rules, and its membership function is: μ △Ktotal ( k Then we have: ， For △ θ The fuzzy set of the fuzzy output variables is △ θ total Similarly, the fuzzy set generated by all triggered rules has the following membership function: μ △θtotal ( θ Then we have: 。 9. The method for distributing the flow rate of the intermediate header of the water-cooled wall in an ultra-supercritical coal-fired unit according to claim 5, characterized in that, Step 4, the specific process is as follows: On the one hand, after receiving the adjustment command, the actuator controlling the three-stage adjustable flow orifice plate (1) increases the orifice plate opening by Δ K The command is sent to the driver of the three rotating motors in the form of analog signal or current. The motor shaft drives the rotating shaft (14) of the three-stage adjustable flow orifice plate (1) to rotate through the coupling, thereby realizing the operation of the three-stage adjustable flow orifice plate (1). On the other hand, after receiving the adjustment command, the actuator controlling the swirl guide vane (2) will increase the guide angle increment Δ θ The instruction is sent to the stepper motor driver in the form of analog signal or pulse. The output shaft of the stepper motor drives the swirling guide vane (2) to rotate through the rotating shaft 16, changing the tilt angle of the swirling guide vane (2) relative to the fluid flow direction.

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