Pressure stress and dynamic response testing and analyzing system for open steel pipe of load shedding of pumped storage power station

Abstract

The invention relates to a pumped storage power station load shedding open steel pipe pressure stress and dynamic response test analysis system. The method is suitable for the technical field of pumped storage transition process pressure pulsation test and analysis. According to the technical scheme, the system comprises a strain gauge which is arranged at a volute inlet in the pumped storage power station and used for collecting structural stress and pressure pulsation data at the volute inlet; the data processor is connected with the strain gauge through a data collector, and the data processor is configured to obtain structural stress and pressure pulsation data at the volute inlet of the pumped storage power station transited from the stable working condition to the 100% load shedding working condition; determining a structural stress process line at the moment of load shedding based on the structural stress and pressure pulsation data at the inlet of the volute, and determining the maximum value of the structural stress based on the structural stress process line; and judging the structural safety of the open steel pipe based on the maximum value of the structural stress and the yield strength of the volute inlet open steel pipe.

Description

Technical Field

[0001] The invention relates to a pressure stress and dynamic response test and analysis system for an exposed steel pipe of a pumped storage power station for load rejection, which is applicable to the technical field of pressure pulsation test and analysis during the transition process of pumped storage. Background Art

[0002] Pumped storage power generation technology has gradually taken on the role of "regulator" and "stabilizer" in new power systems with its excellent functions such as peak-frequency regulation, phase-shifting energy storage and emergency standby. Due to its rapid increase and decrease in load and its important role in peak-to-valley shifting in the power grid, in order to cope with power supply fluctuations, the operating conditions of pumped storage units change frequently during power station operation. When the operating conditions are changed, if a load shedding transition occurs in the water transmission and power generation system, accompanied by severe high-amplitude pressure pulsations, the amplitude of which is large and may even exceed the water hammer pressure, it will affect the structural safety of the unit's flow channel and the volute, runner, and tailwater pipe flow components. In severe cases, it may even cause resonance in the plant, affecting the safe, stable, efficient and flexible operation of the power station.

[0003] However, there are still many deficiencies in the understanding of the generation mechanism of pressure pulsation and its impact on structure, mainly due to:

[0004] 1) The mechanism of pressure pulsation is unknown. Measured data have shown that the transient process of the unit will produce violent and high-frequency pressure pulsation, but the mechanism of pressure pulsation and whether there is randomness or uncertainty in pressure pulsation are unknown.

[0005] 2) Model test results show that the pressure pulsation of a pumped-storage power station is generally most intense under load shedding conditions. At this time, the instantaneous extreme pressure generated by the pressure pulsation exceeds the design pressure of the unit flow path and components in a relatively short period of time. There is no research result on whether this will have a destructive effect on its structure.

[0006] 3) Although the model test can simulate the pressure pulsation under certain test conditions, due to the differences in boundary conditions such as unit size and water supply system characteristics, the model test cannot accurately simulate the actual situation of the real machine pressure pulsation, and there is generally a large deviation from the real machine pressure pulsation data.

[0007] 4) The strength calculation of the unit flow channel and components currently mainly includes classical calculation method and finite element calculation method. The calculation results are closely related to the boundary conditions and the division of the finite element mesh. There is a certain deviation between the theoretical calculation and the actual stress.

[0008] At present, there is a lack of effective quantitative evaluation methods for the impact of pressure pulsation on the structural safety of key flow-through components. Therefore, it is necessary to determine a complete and scientific test and analysis method for the pressure stress and dynamic response of the exposed steel pipe at the inlet of the volute of a pumped-storage power station under load rejection. This has important theoretical and practical reference significance for the safe and efficient operation of pumped-storage power stations under various operating conditions. Summary of the invention

[0009] The technical problem to be solved by the present invention is: in view of the above-mentioned problems, a system for testing and analyzing the pressure stress and dynamic response of the exposed steel pipes of a pumped storage power station under load shedding is provided.

[0010] The technical solution adopted by the present invention is: a test and analysis system for pressure stress and dynamic response of exposed steel pipes of a pumped storage power station under load rejection, characterized in that it includes:

[0011] The strain gauge is installed at the volute inlet of the pumped storage power station to collect the structural stress and pressure pulsation data at the volute inlet;

[0012] A data processor is connected to the strain gauge via a data acquisition device, and the data processor is configured as follows:

[0013] Obtain the structural stress and pressure pulsation data at the volute inlet of the pumped storage power station when it transitions from stable operating conditions to 100% load rejection conditions;

[0014] Based on the structural stress and pressure pulsation data at the volute inlet, the structural stress process line at the moment of load rejection is determined, and the maximum structural stress value is determined based on the structural stress process line;

[0015] The structural safety of the exposed steel pipe is judged based on the maximum structural stress and the yield strength of the exposed steel pipe at the volute inlet.

[0016] The strain gauge is arranged on a first test section and a second test section, wherein the first test section is selected at the upstream side of the volute inlet weld downstream of the unit's water inlet ball valve, and the second test section is selected at the downstream side of the volute inlet weld downstream of the unit's water inlet ball valve.

[0017] The strain gauge includes a unidirectional resistance strain gauge and a bidirectional resistance strain gauge;

[0018] The first test section and the second test section are each provided with at least one bidirectional resistance strain gauge, wherein the 0° direction of the bidirectional resistance strain gauge is the axial direction and the 90° direction of the gauge is the circumferential direction.

[0019] The installation positions of the first test section and the second test section corresponding to the strain gauges are polished and have smooth surfaces.

[0020] The first test section is selected at 20 mm upstream of the volute inlet weld downstream of the unit's water inlet ball valve, and the second test section is selected at 20 mm downstream of the volute inlet weld downstream of the unit's water inlet ball valve.

[0021] A method for testing and analyzing pressure stress and dynamic response of exposed steel pipes in a pumped storage power station under load rejection, characterized by comprising:

[0022] Obtain the structural stress and pressure pulsation data at the volute inlet of the pumped storage power station when it transitions from stable operating conditions to 100% load rejection conditions;

[0023] Based on the structural stress and pressure pulsation data at the volute inlet, the structural stress process line at the moment of load rejection is determined, and the maximum structural stress value is determined based on the structural stress process line;

[0024] The structural safety of the exposed steel pipe is judged based on the maximum structural stress and the yield strength of the exposed steel pipe at the volute inlet.

[0025] A storage medium stores a computer program executable by a processor, wherein the computer program implements the steps of the test analysis method when executed.

[0026] A data processor comprises a memory and a processor, wherein the memory stores a computer program executable by the processor, and wherein the computer program implements the steps of the test and analysis method when executed.

[0027] The beneficial effects of the present invention are as follows: the present invention collects the pressure stress and pressure pulsation data at the volute inlet when the pumped-storage power station transitions from a stable operating condition to a load rejection condition, can scientifically and effectively determine the pressure pulsation intensity under the load rejection condition, and quantitatively analyze its influence on the structural safety of key flow-through components, fully utilizes the actual measurement data and converts it into a control index for the structural safety of key flow-through components, and provides important theoretical and practical reference significance for the safe and efficient operation of the pumped-storage power station under multi-operating condition conversion.

[0028] In the present invention, by comparing the pressure pulsation at each measuring point with the structural stress change process, the influence of pressure pulsation on structural stress can be determined, which can further deepen the understanding of the relationship between pressure pulsation and structural safety, and provide a new method for quantitative evaluation of the influence of pressure pulsation on structural safety.

[0029] The present invention compares the deviations between the measured results and the dynamic stress calculation results, modifies the deviations of the dynamic stress calculation results, predicts the stress level of the extreme working condition, and summarizes the main pressure pulsation types that have an adverse effect on the structure, thereby ensuring the safe operation of the hydropower unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of an embodiment.

[0031] Figure 2 It is a flow chart of installation test and analysis of the test and analysis system in the embodiment.

[0032] Figure 3 Schematic diagram of the test cross-section arrangement in the embodiment.

[0033] Figure 4 and Figure 5 Schematic diagram of measuring point arrangement in the embodiment.

[0034] Figure 6 The stress process lines of each measuring point of Unit 1 with 100% load rejection in the embodiment are shown.

[0035] Figure 7 The stress process lines of each measuring point of Unit 2 with 100% load rejection in the embodiment are shown.

[0036] Figure 8 It is the stress process line of the maximum stress measuring point of each test section at the moment of load rejection in the embodiment.

[0037] Explanation of the reference numerals: 1. volute inlet; 2. tailwater cone; 3. tailwater elbow; 4. tailwater diffusion section; 5. unidirectional resistance strain gauge; 6. bidirectional resistance strain gauge; 7. data acquisition device; 8. data processor; 9. display. DETAILED DESCRIPTION

[0038] Embodiment 1: This embodiment is a test and analysis system for the pressure stress and dynamic response of an exposed steel pipe of a pumped-storage power station under load shedding, including equipment such as a strain gauge, a data collector, a data processor and a display, wherein the data processor is connected to the strain gauge via the data collector, and the display is connected to the data processor.

[0039] In this embodiment, the strain gauge is set at the volute inlet of the pumped storage power station to collect the structural stress and pressure pulsation data at the volute inlet. Two test sections and 10 measuring points are arranged on each unit under test, which are the first and second test sections, 1# to 10# measuring points, and a strain gauge is set corresponding to each measuring point.

[0040] In this example, the test sections include a first test section (1-1 test section) and a second test section (2-2 test section), wherein the first test section is selected at 20mm on the upstream side of the volute inlet weld downstream of the water inlet ball valve of each unit, and the second test section is selected at 20mm on the downstream side of the volute inlet weld downstream of the water inlet ball valve of each unit.

[0041] In this embodiment, measuring points 1# to 4# are set on the first test section, among which measuring point 1# is located at the three o'clock position of the test section (viewed clockwise along the water flow, the same below), measuring point 2# is located at the six o'clock position of the test section, measuring point 3# is located at the nine o'clock position of the test section, and measuring point 4# is located at the twelve o'clock position of the test section.

[0042] In this example, measuring points 5#-8# are set on the second test section, among which measuring point 5# is located at the three o'clock position of the test section (viewed clockwise along the water flow, the same below), measuring point 6# is located at the six o'clock position of the test section, measuring point 7# is located at the nine o'clock position of the test section, and measuring point 8# is located at the twelve o'clock position of the test section.

[0043] In this embodiment, the 9# measuring point is located on the vertical rib plate of the unit top cover (-Y direction) close to the inner ring plate, and the 10# measuring point is located on the vertical rib plate of the unit top cover (-X direction) close to the inner ring plate.

[0044] In this embodiment, unidirectional resistance strain gauges are set at 1#, 2#, 5#, and 6# measuring points, and the direction of the unidirectional resistance strain gauge is circumferential (perpendicular to the water flow direction); bidirectional resistance strain gauges are set at the remaining measuring points, among which the 0° direction of the strain gauges at 3#, 4#, 7#, and 8# measuring points is axial (parallel to the water flow direction), and the 90° direction of the strain gauge is circumferential (perpendicular to the water flow direction), and all measuring points are located on the outer wall of the exposed steel pipe; the 0° direction of the strain gauges at 9# and 10# measuring points is horizontal, and the 90° direction of the strain gauge is vertical.

[0045] In this case, the measuring point positions are determined according to the measuring point arrangement plan, and the surface of the exposed steel pipe is polished to ensure the smoothness of the steel pipe surface, avoid the adverse effects of impurities on the stress monitoring results on the steel pipe surface, and improve the measurement accuracy. Then the strain gauge is installed, and after completion, it is checked whether it is stable, and the drift or swing of the strain gauge is avoided as much as possible.

[0046] In this embodiment, the data processor is connected to the strain gauge via the data collector, and the data processor is configured as follows:

[0047] Obtain the structural stress and pressure pulsation data at the volute inlet of the pumped storage power station when it transitions from stable operating conditions to 100% load rejection conditions;

[0048] Based on the structural stress and pressure pulsation data at the volute inlet, the structural stress process line at the moment of load rejection is determined, and the maximum structural stress value is determined based on the structural stress process line;

[0049] The structural safety of the exposed steel pipe is judged based on the maximum structural stress and the yield strength of the exposed steel pipe at the volute inlet.

[0050] The following is a specific implementation case to illustrate the installation test and analysis method of the test and analysis system in this embodiment.

[0051] Take a pumped storage power station as an example. The pumped storage power station adopts a one-hole two-turbine layout. The rated power of a single turbine is 375MW, the rated head is 447m, the rated speed is 375.0r / min, the rated flow is 98.8m3 / s, and the rated output is 382.7MW. The pressure stress and pressure pulsation at the volute inlet are tested under the 100% load rejection condition of the 1# and 2# units, and the influence of the pressure pulsation on the structure is quantitatively evaluated.

[0052] Step 1: Extract the test conditions and process. Extract the dual-machine 100% load shedding transition process under power generation conditions as the test condition. In the initial state, both 1# and 2# units are in a stable operating state. The units perform dual-machine 100% load shedding and the ball valves are closed.

[0053] Step 2: Select the test equipment. Select the DH5922N dynamic signal acquisition system and the DH3810N-1 strain adapter. The strain gauge models are: BE120-4BB (11) bidirectional resistance strain gauge, BE120-4AA (11) unidirectional resistance strain gauge.

[0054] Step 3: Select the test section and arrange the measuring points. For Unit 1# and Unit 2#, select the 20mm position on the upstream side and the 20mm position on the downstream side of the volute inlet weld of the unit as the test section, and arrange 10 measuring points on each side.

[0055] For Unit 1, measuring points 1#-4# are arranged at the 3 o'clock, 6 o'clock, 9 o'clock and 12 o'clock positions of the 1-1 test section (20mm upstream of the volute inlet weld of Unit 1#) (seen in the clockwise direction of the water flow, the same below), and measuring points 5#-8# are arranged at the 3 o'clock, 6 o'clock, 9 o'clock and 12 o'clock positions of the 2-2 test section (20mm downstream of the volute inlet weld of Unit 1#). Measuring points 9#-10# are located in the (-Y and -X) directions of the vertical ribs of the top cover of Unit 1#, close to the inner ring plate.

[0056] The 1#, 2#, 5#, and 6# measuring points use unidirectional resistance strain gauges with annular direction (perpendicular to the water flow direction), and the other measuring points use bidirectional resistance strain gauges. Among them, the 0° direction of the strain gauges at the 3#, 4#, 7#, and 8# measuring points is axial (parallel to the water flow direction), and the 90° direction of the strain gauges is annular (perpendicular to the water flow direction). All measuring points are located on the outer wall of the exposed steel pipe; the 0° direction of the strain gauges at the 9# and 10# measuring points is horizontal, and the 90° direction of the strain gauges is vertical.

[0057] According to the same layout principle, two test sections (3-3 test section and 4-4 test section) and 10 measuring points (11#-20# measuring points) of Unit 2 were arranged in sequence.

[0058] Step 4: Preliminary preparation and debugging. Paste the strain gauge according to the measurement point layout plan. Polish the steel pipe surface to ensure smoothness before pasting. Check whether it is stable after pasting to avoid drift or swing of the strain gauge. After checking that the resistance value of the strain gauge at each measurement point is normal, connect each measurement point to the DH3810N-1 strain adapter through the test wire, and then connect each adapter to the corresponding channel of the DH5922N dynamic signal acquisition system. Turn on the instrument and test software, set the parameters, and the system enters the acquisition state and preheats for 30 minutes.

[0059] Step 5: Test data acquisition. After preheating is completed, balance each acquisition channel and clear it to zero, enter the continuous sampling state, and end the sampling after the 100% load shedding of the 1# and 2# units is completed and the stress value is stable. During the 100% load shedding process of the two units, there is obvious stress pulsation. Select an appropriate sampling frequency to fully record the stress pulsation process line of the 100% load shedding process of the two units.

[0060] Step 6: Data verification and processing. From the complete record of all units’ 100% load rejection stress pulsation process lines, intercept the process lines of the stress obvious change stage. See the stress process lines of each measuring point of Unit 1# for details. Figure 5 , the stress process lines of each measuring point of Unit 2# are shown in Figure 7 .

[0061] Step 7: Data analysis (performed by the data processor).

[0062] 1) From the entire stress process line of the 100% load shedding stress test of the 1# and 2# units, the 1# and 2# units have the same stress change trend. In the process of transitioning from the stable operation state of the unit to the 100% load shedding state of the unit and the ball valve closing state, the stress at the volute inlet (1# unit 1-1 test section, 2# unit 3-3 test section) increases, and the stress at the volute water inlet (1# unit 2-2 test section, 2# unit 4-4 test section) decreases. At the moment of 100% load shedding of the unit, the stress values ​​of each measuring point fluctuate significantly, and the maximum value appears in the stress process line of the measuring point at this time. During the entire test process, the measured stress change trends of the exposed steel pipes at the volute inlets of units 1# and 2# are consistent with the theoretical stress change trends;

[0063] 2) During the 100% load rejection process of the 1# and 2# units, the maximum circumferential stress of the 1-1 test section of the 1# unit is located at the 2# measuring point, and the stress value is 29.17MPa (relative to the initial zero value, the same below). The maximum circumferential stress of the 2-2 test section is located at the 7# measuring point, and the stress value is 29.901MPa; the stress value of the top cover measuring point is relatively small. The maximum circumferential stress of the 3-3 test section of the 2# unit is located at the 12# measuring point, and the stress value is 25.295MPa (relative to the initial zero value, the same below); the maximum circumferential stress of the 4-4 test section is located at the 17# measuring point, and the stress value is 24.873MPa; the stress value of the top cover measuring point is relatively small.

[0064] 3) The exposed steel pipes (made of B610CF, with a thickness of 70 mm, an inner diameter of 2600 mm, and a yield strength of 490 MPa) at the inlet of the volute case of units 1# and 2# had initial stress values ​​applied by water pressure during the stable operation of the two units before 100% load rejection. The initial water pressure of the 1-1 test section was 5.212 MPa, and the initial circumferential stress value was calculated to be 96.794 MPa; the initial water pressure of the 2-2 test section was 5.206 MPa, and the initial circumferential stress value was calculated to be 96.683 MPa; the initial water pressure of the 3-3 test section was 5.212 MPa, and the initial circumferential stress value was calculated to be 96.794 MPa; the initial water pressure of the 4-4 test section was 5.206 MPa. The actual stress value is the superposition of the initial stress value and the operating state stress value. The calculation results are shown in Table 1. During the entire test process, the maximum stress value of the 1-1 test section is located at the 2# measuring point, and the stress value is 126.964MPa (circumferential stress); the maximum stress value of the 2-2 test section is located at the 7# measuring point, and the stress value is 121.584MPa (circumferential stress); the maximum stress value of the 3-3 test section is located at the 12# measuring point, and the stress value is 122.089Mpa (circumferential pressure); the maximum stress value of the 4-4 test section is located at the 17# measuring point, and the stress value is 121.556Mpa (circumferential pressure). The maximum stress values ​​of the two units both appeared when the dual units were 100% load-shedding. The stress process lines of the maximum stress measuring points of the four test sections at the instant of load-shedding are as follows: Figure 8 shown.

[0065] Table 1 Calculation of maximum stress on the volute inlet of 1# and 2# units when both units are shut down and 100% load rejection

[0066]

[0067] Step 8: Test summary (performed by the data processor).

[0068] Tests and calculations show that the maximum value of the comprehensive stress at each measuring point on the volute inlet during the 100% load rejection process of the 1# and 2# units of the pumped-storage power station is located at the 7# measuring point of the 2-2 test section of unit 1. The stress value is 126.584MPa (circumferential stress), which is much lower than the yield strength of the exposed steel pipe material (490MPa) and lower than the design allowable stress value. The safety margin is large and will not have a destructive effect on the exposed steel pipe structure, meeting the safe operation requirements of the unit.

[0069] Embodiment 2: This embodiment is a method for testing and analyzing the pressure stress and dynamic response of an exposed steel pipe of a pumped storage power station for load shedding, which specifically includes the following steps:

[0070] Obtain the structural stress and pressure pulsation data at the volute inlet of the pumped storage power station when it transitions from stable operating conditions to 100% load rejection conditions;

[0071] Based on the structural stress and pressure pulsation data at the volute inlet, the structural stress process line at the moment of load rejection is determined, and the maximum structural stress value is determined based on the structural stress process line;

[0072] The structural safety of the exposed steel pipe is judged based on the maximum structural stress and the yield strength of the exposed steel pipe at the volute inlet.

[0073] Embodiment 3: This embodiment is a storage medium on which a computer program that can be executed by a processor is stored. When the computer program is executed, the steps of the test analysis method in Embodiment 2 are implemented.

[0074] Embodiment 4: This embodiment is a data processor having a memory and a processor. The memory stores a computer program that can be executed by the processor. When the computer program is executed, the steps of the test analysis method in Embodiment 2 are implemented.

Claims

1. A pumped storage power station load rejection exposed steel pipe pressure stress and dynamic response test and analysis system, characterized in that: include: The strain gauge is installed at the volute inlet of the pumped storage power station to collect the structural stress and pressure pulsation data at the volute inlet; A data processor is connected to the strain gauge via a data acquisition device, and the data processor is configured as follows: Obtain the structural stress and pressure pulsation data at the volute inlet of the pumped storage power station when it transitions from stable operating conditions to 100% load rejection conditions; Based on the structural stress and pressure pulsation data at the volute inlet, the structural stress process line at the moment of load rejection is determined, and the maximum structural stress value is determined based on the structural stress process line; The structural safety of the exposed steel pipe is judged based on the maximum structural stress and the yield strength of the exposed steel pipe at the volute inlet.

2. The pumped storage power station load rejection exposed steel pipe pressure stress and dynamic response test and analysis system according to claim 1 is characterized by: The strain gauge is arranged on a first test section and a second test section, wherein the first test section is selected at the upstream side of the volute inlet weld downstream of the unit's water inlet ball valve, and the second test section is selected at the downstream side of the volute inlet weld downstream of the unit's water inlet ball valve.

3. The pumped storage power station load rejection exposed steel pipe pressure stress and dynamic response test and analysis system according to claim 2 is characterized by: The strain gauge includes a unidirectional resistance strain gauge and a bidirectional resistance strain gauge; The first test section and the second test section are each provided with at least one bidirectional resistance strain gauge, wherein the 0° direction of the bidirectional resistance strain gauge is the axial direction and the 90° direction of the gauge is the circumferential direction.

4. The pumped storage power station load rejection exposed steel pipe pressure stress and dynamic response test and analysis system according to claim 2 is characterized by: The installation positions of the first test section and the second test section corresponding to the strain gauges are polished and have smooth surfaces.

5. The pumped storage power station load rejection exposed steel pipe pressure stress and dynamic response test and analysis system according to claim 2 is characterized by: The first test section is selected at 20 mm upstream of the volute inlet weld downstream of the unit's water inlet ball valve, and the second test section is selected at 20 mm downstream of the volute inlet weld downstream of the unit's water inlet ball valve.

6. A method for testing and analyzing the pressure stress and dynamic response of exposed steel pipes in a pumped storage power station, characterized in that: include: Obtain the structural stress and pressure pulsation data at the volute inlet of the pumped storage power station when it transitions from stable operating conditions to 100% load rejection conditions; Based on the structural stress and pressure pulsation data at the volute inlet, the structural stress process line at the moment of load rejection is determined, and the maximum structural stress value is determined based on the structural stress process line; The structural safety of the exposed steel pipe is judged based on the maximum structural stress and the yield strength of the exposed steel pipe at the volute inlet.

7. A storage medium having stored thereon a computer program executable by a processor, characterized in that: When the computer program is executed, the steps of the test analysis method according to claim 6 are implemented.

8. A data processor comprising a memory and a processor, wherein the memory stores a computer program executable by the processor, wherein: When the computer program is executed, the steps of the test analysis method according to claim 6 are implemented.

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