Method and system for predicting water flow angle of high-pressure side inlet of pump turbine

Abstract

The invention provides a prediction method and system for a water flow angle of a high-pressure side inlet of a pump turbine, and belongs to the technical field of hydraulic machinery. The technical problems that in the prior art, a high-pressure side inlet water flow angle cannot be directly measured, consumed time is too long by depending on CFD simulation calculation, and online monitoring is difficult to achieve can be at least partially solved. According to the method, flow field characteristic constants representing current flow field characteristics are calculated by obtaining external operation parameters such as the rotating speed and the flow of the pump turbine and geometric structure parameters such as the diameter of a rotating wheel; meanwhile, the actual opening degree of the movable guide vane is collected in real time; a preset flow field parameter coupling relation model is utilized, the opening degree of the movable guide vane and the flow field characteristic constant serve as input, and the high-pressure side inlet water flow angle is obtained through calculation. According to the method, the internal key flow field parameters can be quickly deduced by using the external data which is easy to obtain, and real-time data support is provided for safe and stable operation of a unit.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic machinery technology, specifically relating to a method and system for predicting the flow angle at the high-pressure side inlet of a water pump turbine. Background Technology

[0002] In pumped-storage power stations, the pump-turbine, as the core energy conversion device, directly determines the unit's operating efficiency and stability through its internal flow field characteristics. In the hydraulic design and operational analysis of the pump-turbine, the high-pressure side inlet flow angle (β1) is a crucial internal flow field parameter. This parameter directly affects the impact loss when water enters the runner, thus influencing the unit's hydraulic efficiency and cavitation characteristics. If the inlet flow angle does not match the blade inlet installation angle, significant flow separation and vortices will occur, leading to increased energy loss and even vibration.

[0003] However, in existing technologies, the high-pressure side inlet flow angle β1 is a typical intrinsic parameter that is difficult to measure directly using physical sensors. Currently, the main method used in the industry to obtain this parameter is computational fluid dynamics (CFD) simulation. Although CFD simulation can provide relatively detailed flow field information, its modeling is complex, mesh generation is cumbersome, and the calculation cycle is long, requiring significant computational resources and time. This makes CFD methods difficult to apply to real-time engineering monitoring or rapid performance evaluation.

[0004] Therefore, existing technologies lack a method to quickly and accurately infer the critical internal flow angle β1 based on easily measurable external operating parameters. This limits the real-time perception and refined control of the pump-turbine operating status. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art, and provides a method for predicting the inlet flow angle of a water pump turbine at the high pressure side.

[0006] A method for predicting the flow angle at the high-pressure side inlet of a water pump turbine, the prediction method comprising: Obtain the external operating parameters and preset geometric parameters of the water pump turbine under the current operating conditions; Using the external operating parameters and the geometric parameters, the flow field characteristic constants characterizing the flow field properties under the current operating conditions are calculated. ; The opening degree of the movable guide vanes of the water pump turbine is collected in real time by sensors. ; The preset flow field parameter coupling model is invoked, based on the opening degree of the active guide vane. and the flow field characteristic constant Calculate the inlet flow angle at the high-pressure side. ; The flow field parameter coupling model is constructed based on the triangular relationship between the inlet and outlet velocities of the water pump and turbine.

[0007] Furthermore, the coupling relationship model of the flow field parameters satisfies the following relationship: ; in, The opening degree of the movable guide vane, The inlet water flow angle of the high-pressure side is... is the characteristic constant of the flow field.

[0008] Furthermore, the external operating parameters include the real-time rotational speed of the pump-turbine. and real-time traffic ; The geometric parameters include the diameter of the high-pressure side of the impeller. and rotor blade height .

[0009] Furthermore, the flow field characteristic constant The calculation steps are as follows: ; in, This represents the real-time flow rate of the water pump turbine. This refers to the real-time rotational speed of the water pump turbine. For the height of the rotor blades, The diameter of the high-pressure side of the rotor. Pi is the mathematical constant of a circle.

[0010] Furthermore, the flow field parameter coupling model is derived based on the velocity triangle sine theorem for a water pump turbine under turbine operating conditions. The velocity triangle sine theorem is characterized as follows: .

[0011] Furthermore, the impeller height in the geometric parameters... Relative leaf height With respect to the diameter of the high pressure side of the rotor The product of.

[0012] Furthermore, the prediction method also includes: The calculated high-pressure side inlet water flow angle Transmitted to the control system of the water pump turbine via industrial communication protocols; The control system will adjust the high-pressure side inlet water flow angle. The impact angle deviation is calculated by comparing it with the preset blade inlet geometry. When the deviation exceeds the safety threshold, an adjustment command is issued to change the guide vane opening of the pump turbine.

[0013] A system for predicting the flow angle at the high-pressure side inlet of a water pump turbine includes: The parameter acquisition module is configured to receive the real-time speed of the water pump and turbine from the sensor. and real-time traffic And read the preset high-pressure side diameter of the rotor from the memory. and rotor blade height ; The status monitoring module is configured to collect the opening degree of the moving guide vanes of the water pump turbine. ; The calculation and processing module is configured to first calculate based on the rotational speed. ,flow High-pressure side diameter of the impeller and rotor blade height Calculate the characteristic constants of the flow field Then, based on the preset relation: Calculate the inlet flow angle at the high-pressure side. ; The output module is configured to output the inlet water flow angle of the high-pressure side. To external monitoring equipment.

[0014] Furthermore, the parameter acquisition module includes a speed signal acquisition unit and a flow signal acquisition unit. The speed signal acquisition unit is connected to a geared disc speed sensor mounted on the main shaft of the water pump turbine, and is configured to acquire pulse signals at a preset high-frequency sampling rate and analyze them into real-time speed. The flow signal acquisition unit is connected to an ultrasonic flow meter and an electromagnetic flow meter installed on the pressure steel pipe, and is configured to acquire real-time flow. ; The status monitoring module includes a guide vane displacement acquisition unit, which is connected to a magnetostrictive displacement sensor mounted on the piston rod of the guide vane servo drive, and is configured to acquire guide vane displacement signals and convert them into angle values. ; The calculation and processing module receives the rotation speed via an industrial fieldbus. ,flow and angle value .

[0015] Furthermore, the output module is communicatively connected to the speed governor control unit of the water pump turbine; The speed controller control unit stores an optimal water flow angle reference table, which contains the corresponding ideal water flow angle values ​​without impact under different operating conditions. The speed controller control unit is configured to receive the calculated values ​​output by the calculation processing module. Calculate this value The difference between the current operating condition and the ideal non-impact flow angle is used to send a correction command to the guide vane relay to fine-tune the opening of the active guide vane when the difference indicates a risk of flow separation.

[0016] The beneficial effects of this invention are as follows: This invention, through in-depth analysis of the geometric relationship between the inlet and outlet velocity triangles of a water pump turbine, derives for the first time the precise cotangential coupling relationship between the opening of the movable guide vane and the flow angle at the high-pressure side inlet. This mathematical model reveals the intrinsic physical connection between externally measurable parameters and internally unmeasurable flow field parameters.

[0017] Based on this method, engineers can calculate the critical internal flow angle in seconds using only the rotational speed, flow rate, and guide vane opening data that can be obtained from conventional monitoring systems, without having to perform expensive and time-consuming CFD simulations. This greatly improves the efficiency of parameter acquisition, making real-time online monitoring of the internal flow state of the pump turbine possible, and providing important data support for the optimized operation and fault early warning of the unit. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the basic process of the method for predicting the inlet flow angle of a water pump turbine according to an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0020] Example 1: Hardware Architecture and Data Processing Flow of the Prediction System This embodiment provides a pump-turbine high-pressure side inlet flow angle prediction system integrated into a modern large-scale pumped storage power station computer monitoring system. The system adopts a modular design, achieving "transparent" monitoring of the internal flow field state of the unit through the collaborative work of a high-precision sensor network, industrial-grade data acquisition units, and high-performance computing processing units.

[0021] The prediction system mainly consists of four core components: a parameter acquisition module, a status monitoring module, a calculation and processing module, and an output module. These modules are deployed in the local control unit (LCU) cabinet of the power plant and exchange data at high speed via a backplane bus or industrial Ethernet.

[0022] like Figure 1 As shown, this method is implemented through the following steps based on the above module deployment: Step S1: Collect and parse external operating parameters and geometric structure parameters.

[0023] The parameter acquisition module is responsible for capturing the unit's fluid dynamics and mechanical motion parameters in real time. For speed signal acquisition, this module connects to a geared disc speed sensor mounted on the top of the pump turbine's main shaft. This sensor uses an oil-resistant, electromagnetic interference-resistant magnetic induction probe. The geared disc on the main shaft typically has 60 or more teeth; as the main shaft rotates, the sensor outputs a high-frequency pulse sequence. The acquisition card counts the pulses at a sampling frequency up to 10kHz and calculates the real-time speed signal with a resolution better than 0.01Hz using a periodic frequency measurement method. The unit is revolutions per minute (r / min). To prevent signal interference, shielded twisted-pair cable is used for the acquisition line, and an opto-isolation circuit is installed at the input end. For flow signal acquisition, this module connects to an ultrasonic flow meter installed on a straight section of a pressure steel pipe via Modbus TCP or a 4-20mA analog interface. This flow meter uses the multi-channel time-of-flight measurement principle and can provide real-time flow data with an accuracy better than 0.5% under large-diameter, high-velocity conditions. The unit is cubic meters per second (m³ / s). For the geometric parameters, the system has a pre-configured parameter table in non-volatile flash memory. During the system debugging phase, engineers write the high-pressure side diameter of the impeller into the system via a handheld terminal or host computer software. (e.g., 4200mm) and impeller height (e.g., 450mm). These parameters are write-protected to prevent accidental tampering.

[0024] Step S2: Monitor and switch the opening of the active guide vane in real time.

[0025] The condition monitoring module focuses on the precise measurement of the position of the moving guide vanes. This module connects to a magnetostrictive displacement sensor mounted on the piston rod of the guide vane servo drive via an SSI synchronous serial interface. This sensor outputs a digital signal representing the servo drive stroke with micron-level accuracy. The system internally stores the data as "servo drive stroke L - guide vane angle". The nonlinear characteristic curve is derived from a 10th-order polynomial equation fitted based on measured data from the unit's installation and commissioning phase. The condition monitoring module uses this equation to map linear displacement to physical angles in real time. Ensure that the angle error is less than 0.1 degrees. This angle is defined as the angle between the tangent line of the guide vane outlet edge and the tangent line of the unit's central circumference, and the unit is degrees (°).

[0026] To smooth out data fluctuations caused by mechanical vibrations, the module integrates a moving average filtering algorithm to preprocess the collected raw angle data.

[0027] Step S3: Solve for the flow field characteristic constants and flow angle based on the coupled model.

[0028] The computation processing module is the logical core of this system. It runs on a real-time operating system (RTOS) to ensure deterministic task scheduling. The computation tasks are set as high-priority periodic tasks with a period of 20ms.

[0029] Phase 1: Calculation of flow field characteristic constants. The processor first reads the current time slice... And fixed To ensure computational precision, all floating-point operations are performed using the IEEE 754 double-precision format. The processor executes the formula... .

[0030] To prevent division by zero errors, the program sets the rotation speed. Dead zone judgment, when When the speed is less than 5% of the rated speed (i.e., stopped or at extremely low speed), directly... Set to the preset initial value or stop the calculation. This constant It dynamically reflects the constraints on the motion characteristics of fluid particles at the inlet of the impeller under the current operating conditions, and serves as a bridge connecting external macroscopic parameters and internal microscopic flow fields.

[0031] Second stage: Flow angle calculation. The processor receives the guide vane opening. First, a validity check is performed (e.g., Subsequently, mathematical library functions are used to calculate... Next, using the pre-defined analytical model... Perform the core solution. Finally, call the inverse cotangent function to calculate... The radian value is then converted to an angle value. The processor outputs... Similarly, after amplitude limiting filtering, invalid values ​​caused by transient disturbances are removed.

[0032] Step S4: Output the prediction results and execute closed-loop control interaction.

[0033] The output module is equipped with dual redundant industrial Ethernet interfaces, supporting IEC 60870-5-104 or OPC UA protocols. It will calculate... The data stream is pushed to the plant-wide monitoring system (SCADA) and the speed controller control unit.

[0034] Monitoring-side application: On the screen in the central control room, It is displayed as a dynamic dashboard. When Deviation from the design optimum (e.g.) )Exceed At that time, the dashboard on the screen turns red and flashes, alerting operators to the risk of incoming flow impact.

[0035] Control-side application: The governor internally operates "coordination optimization" logic. Traditional coordination relationships are based solely on head and power lookup tables, while this system introduces... As a correction factor. When detected. In case of an anomaly, the speed controller will automatically generate a guide vane position correction command while maintaining constant power, driving the electro-hydraulic servo valve to fine-tune the guide vane opening. Search The optimal operating point is close to the design value, thereby enabling active optimization control based on the flow field state.

[0036] The method and system provided by this invention ingeniously utilize the physical law between the guide vane opening and the cotangent of the water flow angle, solving the problem of the difficulty in obtaining internal flow field parameters in real time, and providing technical means for the intelligent operation of water pump turbines.

[0037] In summary, the embodiments disclosed herein have at least the following technical effects: By deeply analyzing the geometric relationship between the inlet and outlet velocity triangles of a water pump turbine, a precise cotangential coupling relationship between the opening of the movable guide vane and the flow angle at the high-pressure side inlet was derived for the first time. This mathematical model reveals the intrinsic physical connection between externally measurable parameters and internally unmeasurable flow field parameters.

[0038] Based on this method, engineers can calculate the critical internal flow angle in seconds using only the rotational speed, flow rate, and guide vane opening data that can be obtained from conventional monitoring systems, without having to perform expensive and time-consuming CFD simulations. This greatly improves the efficiency of parameter acquisition, making real-time online monitoring of the internal flow state of the pump turbine possible, and providing important data support for the optimized operation and fault early warning of the unit.

[0039] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for predicting the inlet flow angle of a water pump turbine at the high-pressure side, characterized in that, The prediction method includes: Obtain the external operating parameters and preset geometric parameters of the water pump turbine under the current operating conditions; Using the external operating parameters and the geometric parameters, the flow field characteristic constants characterizing the flow field properties under the current operating conditions are calculated. ; The opening degree of the movable guide vanes of the water pump turbine is collected in real time by sensors. ; The preset flow field parameter coupling model is invoked, based on the opening degree of the active guide vane. and the flow field characteristic constant Calculate the inlet flow angle at the high-pressure side. ; The flow field parameter coupling model is constructed based on the triangular relationship between the inlet and outlet velocities of the water pump and turbine.

2. The method for predicting the inlet flow angle of a water pump turbine at the high pressure side according to claim 1, characterized in that, The coupling relationship model of the flow field parameters satisfies the following equation: ; in, The opening degree of the movable guide vane, The inlet water flow angle of the high-pressure side is... is the characteristic constant of the flow field.

3. The method for predicting the inlet flow angle of a water pump turbine at the high pressure side according to claim 1, characterized in that, The external operating parameters include the real-time speed of the water pump and turbine. and real-time traffic ; The geometric parameters include the diameter of the high-pressure side of the impeller. and rotor blade height .

4. The method for predicting the inlet flow angle of a water pump turbine at the high pressure side according to claim 3, characterized in that, The flow field characteristic constant The calculation steps are as follows: ; in, This represents the real-time flow rate of the water pump turbine. This refers to the real-time rotational speed of the water pump turbine. For the height of the rotor blades, The diameter of the high-pressure side of the rotor. Pi is the mathematical constant of a circle.

5. The method for predicting the inlet flow angle of a water pump turbine at the high pressure side according to claim 1, characterized in that, The flow field parameter coupling model is derived based on the velocity triangle sine theorem for a water pump turbine under turbine operating conditions. The velocity triangle sine theorem is characterized as follows: .

6. The method for predicting the inlet flow angle of a water pump turbine at the high pressure side according to claim 1, characterized in that, The impeller height in the geometric parameters Relative leaf height With respect to the diameter of the high pressure side of the rotor The product of.

7. The method for predicting the inlet flow angle of a water pump turbine at the high pressure side according to claim 1, characterized in that, The prediction method further includes: The calculated high-pressure side inlet water flow angle Transmitted to the control system of the water pump turbine via industrial communication protocols; The control system will adjust the high-pressure side inlet water flow angle. The impact angle deviation is calculated by comparing it with the preset blade inlet geometry. When the deviation exceeds the safety threshold, an adjustment command is issued to change the guide vane opening of the pump turbine.

8. A prediction system for the high-pressure side inlet water flow angle of a water pump turbine, characterized in that, include: The parameter acquisition module is configured to receive the real-time speed of the water pump and turbine from the sensor. and real-time traffic And read the preset high-pressure side diameter of the rotor from the memory. and rotor blade height ; The status monitoring module is configured to collect the opening degree of the moving guide vanes of the water pump turbine. ; The calculation and processing module is configured to first calculate based on the rotational speed. ,flow High-pressure side diameter of the impeller and rotor blade height Calculate the characteristic constants of the flow field Then, based on the preset relation: Calculate the inlet flow angle at the high-pressure side. ; The output module is configured to output the inlet water flow angle of the high-pressure side. To external monitoring equipment.

9. The prediction system for the high-pressure side inlet water flow angle of a water pump turbine according to claim 8, characterized in that, The parameter acquisition module includes a speed signal acquisition unit and a flow rate signal acquisition unit. The speed signal acquisition unit is connected to a geared disc speed sensor installed on the main shaft of the water pump turbine, and is configured to acquire pulse signals at a preset high-frequency sampling rate and analyze them into real-time speed. The flow signal acquisition unit is connected to an ultrasonic flow meter and an electromagnetic flow meter installed on the pressure steel pipe, and is configured to acquire real-time flow. ; The status monitoring module includes a guide vane displacement acquisition unit, which is connected to a magnetostrictive displacement sensor mounted on the piston rod of the guide vane servo drive, and is configured to acquire guide vane displacement signals and convert them into angle values. ; The calculation and processing module receives the rotation speed via an industrial fieldbus. ,flow and angle value .

10. The prediction system for the high-pressure side inlet water flow angle of a water pump turbine according to claim 8, characterized in that, The output module is communicatively connected to the governor control unit of the water pump turbine; The speed controller control unit stores an optimal water flow angle reference table, which contains the corresponding ideal water flow angle values ​​without impact under different operating conditions. The speed controller control unit is configured to receive the calculated values ​​output by the calculation processing module. Calculate this value The difference between the current operating condition and the ideal non-impact flow angle is used to send a correction command to the guide vane relay to fine-tune the opening of the active guide vane when the difference indicates a risk of flow separation.

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