Water turbine flow measurement method based on digital twin technology

Abstract

The invention discloses a water turbine flow measurement method based on a digital twinning technology and belongs to the technical field of water turbine measurement. The method comprises the following steps: firstly, establishing a three-dimensional digital twin model of the water turbine, carrying out fluid simulation calculation based on a fluid mechanics principle, simulating a pressure difference delta p between two fixed pressure measuring holes at the inner edge and the outer edge of a volute of the water turbine under different working conditions and a corresponding simulation flow Q1, obtaining a corresponding flow relation curve and a flow coefficient of the Q1 and the delta p, and storing the curve and the coefficient in a memory bank; delta H is measured in real time through a pressure measuring device installed in the volute of the water turbine; and calculating the corresponding actual flow Q according to the K value in the memory bank. According to the method, high-precision and dynamic monitoring of the volute flow of the water turbine is achieved. The method not only improves the measurement precision and reliability, but also adapts to the structure change possibly occurring in the long-term operation process of the water turbine, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of water turbine measurement, and in particular relates to a water turbine flow measurement method based on digital twin technology. Background Art

[0002] Turbine flow measurement is a key technology for the economic operation and efficiency assessment of hydropower stations. Existing measurement methods primarily include turbine volute differential pressure, velocity meter, water hammer, and ultrasonic methods. The turbine volute differential pressure method, due to its simplicity, cost-effectiveness, and lack of complex equipment, is widely used for real-time monitoring of large and medium-sized units.

[0003] The turbine volute differential pressure method measures the pressure difference ΔH between the two fixed pressure measuring holes on the inner and outer edges of the turbine volute, and calculates the flow rate Q through the turbine in combination with the flow coefficient K. The formula is: Q = K√ΔH, However, the calibration of the flow coefficient K presents several challenges in actual measurement and calculation. First, it requires turbine prototype efficiency testing, a process that requires downtime, impacting power plant operating revenue and resulting in high costs. Furthermore, after long-term operation, changes in the turbine volute structure can cause the K value to drift, necessitating regular recalibration. Summary of the Invention

[0004] The present invention provides a turbine flow measurement method based on digital twin technology, which realizes accurate calibration of the flow coefficient K without stopping the machine and performing efficiency tests, solves the problem of K value drift caused by changes in the turbine volute structure, and realizes high-precision and real-time turbine flow measurement.

[0005] The method for measuring flow of a hydraulic turbine based on digital twin technology is characterized by comprising the following steps: S1: Measure the actual external dimensions of the turbine volute, subtract the volute wall thickness, and inversely calculate the internal flow path dimensions. Simultaneously, measure the specific locations of the pressure measuring points. Establish a 3D digital twin model of the turbine based on the internal flow path dimensions and the specific locations of the pressure measuring points. Use GAMBIT, STAR-CCM+, or FLUENT Meshing to model and numerically mesh the model. Divide the fluid region of the 3D digital twin model into the volute inlet straight pipe section, the volute section, and the fixed guide vane section. The fixed guide vane section uses an unstructured hybrid tetrahedral mesh with strong adaptability to complex boundary models and is encrypted. S2, in the digital twin model, fluid simulation calculation is performed based on the principles of fluid mechanics to simulate the pressure values ​​p at two fixed pressure measuring points on the inner edge A and outer edge B of the turbine volute. A and p B And the simulated flow Q1 between the two pressure measuring points, the fluid simulation calculation method is as follows: , in: is the fluid density, is the local acceleration of the velocity field that varies with time, is the convective acceleration caused by the spatial variation of the velocity field, It is the pressure gradient force that drives the fluid to flow from high pressure to low pressure area. is the viscous force, μ is the dynamic viscosity, which reflects the momentum diffusion caused by the internal friction of the fluid, f is the volume force, the external force per unit volume; S3, using the Spalart-Allmaras single equation model, the inlet section of the volute inlet straight pipe section and the fixed guide vane outlet section are set as the calculated pressure inlet and pressure outlet, respectively. The solid wall adopts the side wall no-slip condition, and the wall function is used in the area near the solid boundary. Combined with the SIMPLE algorithm, the separated pressure correction method is selected as the numerical solution method of the flow field. The diffusion term and the original term are discretized using the second-order central difference format, and the convection term is discretized using the second-order upwind difference format. The flow field distribution of the turbine volute under different operating conditions is simulated. The flow state under different operating conditions is simulated: under the condition of constant inlet pressure, the inlet flow rate is changed at the rated head, and the pressure difference Δp between the inner edge A and the outer edge B of the turbine volute under different flow rates is calculated. Δp=p A -p B S4, obtain the flow relationship curve of the simulated flow Q1 and the pressure difference Δp, and calculate the flow coefficient, , and storing the flow relationship curve or flow coefficient in a memory bank; S4, when the unit is running, the actual pressure difference ΔH of the turbine is measured in real time by the pressure measuring device installed in the turbine volute; the corresponding actual flow Q is calculated according to the flow relationship curve or flow coefficient in the memory bank. , S5. After the turbine has been running for a long time, if the flow pattern changes, re-measure the actual dimensions inside the turbine volute, update the digital twin model according to S1 based on the new measured data, and re-calculate the fluid simulation and discharge coefficient.

[0006] The beneficial effects of the present invention are as follows: through fluid mechanics simulation calculations, the corresponding relationship between the pressure difference ΔH and the flow rate Q through the machine is accurately established, which greatly improves the accuracy of flow measurement. During the operation of the turbine, ΔH data is collected in real time and calculated in combination with the digital twin model to achieve real-time monitoring of the flow. The flow relationship curve or function expression of Δp and Q1 in the digital twin model is regularly updated to effectively adapt to the structural changes of the turbine volute due to factors such as wear, ensuring that the measurement results are always accurate and reliable. The measurement and calculation process does not rely on the shutdown and efficiency test of the turbine, and the flow monitoring can be continuously performed in the operating state, which greatly reduces the capital cost and downtime. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 Schematic diagram of the turbine structure in Example 1.

[0008] Figure 2 This is a flow chart of the turbine flow measurement method based on digital twin technology.

[0009] Figure 3 1 is a curve diagram showing the relationship between the pressure difference ΔH and the flow rate Q in Example 1.

[0010] Among them: 1-pressure measuring device. DETAILED DESCRIPTION

[0011] Example 1: A method for measuring the flow rate of a hydraulic turbine based on digital twin technology. The implementation steps are as follows: S1: Measure the actual external dimensions of the turbine volute, subtract the volute wall thickness, and inversely calculate the internal flow path dimensions. Simultaneously, measure the specific locations of the pressure measuring points. Establish a 3D digital twin model of the turbine based on the internal flow path dimensions and the specific locations of the pressure measuring points. Use GAMBIT, STAR-CCM+, or FLUENT Meshing to model and numerically mesh the model. Divide the fluid region of the 3D digital twin model into the volute inlet straight pipe section, the volute section, and the fixed guide vane section. The fixed guide vane section uses an unstructured hybrid tetrahedral mesh with strong adaptability to complex boundary models and is encrypted. S2, in the digital twin model, fluid simulation calculation is performed based on the principles of fluid mechanics to simulate the pressure values ​​p at two fixed pressure measuring points on the inner edge A and outer edge B of the turbine volute. A and p B And the simulated flow Q1 between the two pressure measuring points, the fluid simulation calculation method is as follows: , in: is the fluid density, is the local acceleration of the velocity field that varies with time, is the convective acceleration caused by the spatial variation of the velocity field, It is the pressure gradient force that drives the fluid to flow from high pressure to low pressure area. is the viscous force, μ is the dynamic viscosity, which reflects the momentum diffusion caused by the internal friction of the fluid, f is the volume force, the external force per unit volume; S3, using the Spalart-Allmaras single equation model, the inlet section of the volute inlet straight pipe section and the fixed guide vane outlet section are set as the calculated pressure inlet and pressure outlet, respectively. The solid wall adopts the side wall no-slip condition, and the wall function is used in the area near the solid boundary. Combined with the SIMPLE algorithm, the separated pressure correction method is selected as the numerical solution method of the flow field. The diffusion term and the original term are discretized using the second-order central difference format, and the convection term is discretized using the second-order upwind difference format. The flow field distribution of the turbine volute under different operating conditions is simulated. The flow state under different operating conditions is simulated: under the condition of constant inlet pressure, the inlet flow rate is changed at the rated head, and the pressure difference Δp between the inner edge A and the outer edge B of the turbine volute under different flow rates is calculated. Δp=p A -p B S4, obtain the flow relationship curve of the simulated flow Q1 and the pressure difference Δp, and calculate the flow coefficient, , and storing the flow relationship curve or flow coefficient in a memory bank; S4, when the unit is running, the actual pressure difference ΔH of the turbine is measured in real time by the pressure measuring device 1 installed in the turbine volute; the corresponding flow rate Q is calculated according to the flow relationship curve or flow coefficient in the memory bank, , S5. After the turbine has been running for a long time, if the flow pattern changes, re-measure the actual dimensions inside the turbine volute, update the digital twin model according to S1 based on the new measured data, and re-calculate the fluid simulation and discharge coefficient.

Claims

1. The hydraulic turbine flow measurement method based on digital twin technology is characterized by The following steps are involved: S1: Measure the actual external dimensions of the turbine volute, subtract the volute wall thickness, and inversely calculate the internal flow path dimensions. Simultaneously, measure the specific locations of the pressure measuring points. Establish a 3D digital twin model of the turbine based on the internal flow path dimensions and the specific locations of the pressure measuring points. Use GAMBIT, STAR-CCM+, or FLUENT Meshing to model and numerically mesh the model. Divide the fluid region of the 3D digital twin model into the volute inlet straight pipe section, the volute section, and the fixed guide vane section. The fixed guide vane section uses an unstructured hybrid tetrahedral mesh with strong adaptability to complex boundary models and is encrypted. S2, in the digital twin model, fluid simulation calculation is performed based on the principles of fluid mechanics to simulate the pressure values ​​p at two fixed pressure measuring points on the inner edge A and outer edge B of the turbine volute. A and p B And the simulated flow Q1 between the two pressure measuring points, the fluid simulation calculation method is as follows: , in: is the fluid density, is the local acceleration of the velocity field that varies with time, is the convective acceleration caused by the spatial variation of the velocity field, It is the pressure gradient force that drives the fluid to flow from high pressure to low pressure area. is the viscous force, μ is the dynamic viscosity, which reflects the momentum diffusion caused by the internal friction of the fluid, f is the volume force, the external force per unit volume; S3, using the Spalart-Allmaras single equation model, the inlet section of the volute inlet straight pipe section and the fixed guide vane outlet section are set as the calculated pressure inlet and pressure outlet, respectively. The solid wall adopts the side wall no-slip condition, and the wall function is used in the area near the solid boundary. Combined with the SIMPLE algorithm, the separated pressure correction method is selected as the numerical solution method of the flow field. The diffusion term and the original term are discretized using the second-order central difference format, and the convection term is discretized using the second-order upwind difference format. The flow field distribution of the turbine volute under different operating conditions is simulated. The flow state under different operating conditions is simulated: under the condition of constant inlet pressure, the inlet flow rate is changed at the rated head, and the pressure difference Δp between the inner edge A and the outer edge B of the turbine volute under different flow rates is calculated. Δp=p A -p B， S4, obtain the flow relationship curve of the simulated flow Q1 and the pressure difference Δp, and calculate the flow coefficient, ， and storing the flow relationship curve or flow coefficient in a memory bank; S4, when the unit is running, the actual pressure difference ΔH of the turbine is measured in real time by the pressure measuring device installed in the turbine volute; the corresponding actual flow Q is calculated according to the flow relationship curve or flow coefficient in the memory bank. ， S5. After the turbine has been running for a long time, if the flow pattern changes, re-measure the actual dimensions inside the turbine volute, update the digital twin model according to S1 based on the new measured data, and re-calculate the fluid simulation and discharge coefficient.

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