Backpressure adjusting method of water tunnel experiment device

Abstract

The invention relates to the technical field of water tunnel experiment devices, in particular to a backpressure adjusting method of a water tunnel experiment device. An impeller assembly and a pressure sensor are arranged in the water tunnel experiment device, the impeller assembly rotates under the impact effect of water flow and converts kinetic energy of the water flow into mechanical energy, and the pressure sensor is in signal connection with the control system. The pressure sensor monitors the backpressure in the water tunnel experiment device in real time, the control system adjusts the rotating speed of the impeller assembly to achieve stepless adjustment of the backpressure and slow response speed according to the positive and negative values of the difference value between the target backpressure value and the real-time backpressure value and the absolute value, the backpressure is monitored in real time, and the rotating speed of the impeller assembly is adjusted in real time. The dynamic adjustment requirement of experimental parameters can be rapidly met, high-precision and stable adjustment of the back pressure is achieved, and the effectiveness of the experimental process and data is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of water tunnel experimental devices, and particularly to a method for adjusting the back pressure of a water tunnel experimental device. Background Art

[0002] As a key experimental equipment for fluid mechanics research, the energy utilization efficiency and flow field control accuracy of a water tunnel directly affect the scientific research cost and experimental reliability. At present, there are significant technical bottlenecks in energy recovery and back pressure regulation for conventional water tunnel facilities.

[0003] In the existing design of water tunnel facilities, energy recovery devices are generally lacking, resulting in most of the energy contained in the end water flow not being effectively utilized. The end water flow often only undergoes simple energy dissipation treatment or is directly discharged, and the kinetic energy it carries cannot be converted into other available energy forms. This not only causes significant energy waste but also leads to low overall energy utilization efficiency of the water tunnel facility and high operating costs.

[0004] In addition, there are many drawbacks in the back pressure regulation of current water tunnel facilities, which have become the key factors restricting the improvement of water tunnel experimental effects and efficiency. The specific manifestations are as follows: (1) Function deficiency: Many water tunnel facilities are not equipped with a back pressure regulation device, or although such a device is provided, it cannot achieve stepless regulation of the back pressure, making it difficult to meet the flexible adjustment requirements of the back pressure for diverse experiments; some water tunnel facilities use a mechanical regulating valve for back pressure regulation, which only supports discrete pressure gear switching and cannot achieve continuous back pressure regulation required for cavitation experiments; (2) Insufficient control accuracy: Existing mechanical regulating valves have problems with poor pressure control accuracy. Due to factors such as the friction between the valve core and the valve seat and the pulsating interference of the fluid, it is difficult to accurately adjust to the required back pressure value according to different experimental conditions, thereby resulting in poor cavitation control effects and affecting the accuracy and reliability of experimental data; at the same time, the wear of the valve core after long-term use will further exacerbate the problem of decreased control accuracy and shorten the service life of the equipment; (3) Slow response speed: When the experimental conditions change, the existing back pressure regulating valve has a slow response speed and cannot quickly adapt to the dynamic adjustment requirements of experimental parameters, resulting in a significant reduction in experimental efficiency and seriously affecting the experimental process and the validity of data; Therefore, it is necessary to develop a method that can effectively prevent cavitation from occurring and achieve stepless regulation of the back pressure of a water tunnel experimental device. Summary of the Invention

[0005] In view of the deficiencies in the above-mentioned existing technologies, the present invention provides a method for adjusting the back pressure of a water tunnel experimental device that can achieve stepless regulation.

[0006] The present invention provides a method for adjusting the back pressure of a water tunnel experimental device. An impeller assembly and a pressure sensor are arranged inside the water tunnel experimental device. The impeller assembly rotates under the impact of water flow, converting the kinetic energy of water flow into mechanical energy. The pressure sensor is signal-connected to a control system; The back pressure adjustment method includes the following steps: Obtain the target back pressure value: The control system sets the required back pressure value under different experimental conditions as the target back pressure value P T ; Calculate the pressure difference: The pressure sensor monitors the real-time back pressure value P of the water tunnel experimental device in real time i , and the difference between the target back pressure value and the real-time back pressure value is used as the calculated pressure difference ΔP i : ΔP i =P T -P i ; Adjust the rotational speed of the impeller assembly: The control system adjusts the rotational speed of the impeller assembly according to the positive or negative and the absolute value size of ΔP i : When the real-time back pressure value P i is greater than the target back pressure value P T , increase the rotational speed of the impeller assembly, so that the resistance generated by the impeller assembly on the water flow decreases. At this time, the real-time back pressure value P i decreases until the real-time back pressure value is equal to the target back pressure value P T , and maintain the rotational speed of the impeller assembly at this time; When the real-time back pressure value P i is less than the target back pressure value P T , decrease the rotational speed of the impeller assembly, so that the resistance to the water flow passing through the impeller assembly increases. At this time, the real-time back pressure value P i increases until the real-time back pressure value is equal to the target back pressure value P T , and maintain the rotational speed of the impeller assembly at this time; The pressure sensor monitors the adjusted back pressure value in real time, feeds it back to the control system, and adjusts the back pressure value in real time, so that the real-time back pressure value is always stable near the target back pressure value.

[0007] In this technical solution, an impeller assembly is arranged inside the water tunnel experimental device. The pressure sensor monitors the back pressure inside the water tunnel experimental device in real time. The control system adjusts the rotational speed of the impeller assembly to achieve stepless adjustment of the back pressure. The response speed is slow. And it monitors the back pressure in real time and adjusts the rotational speed of the impeller assembly in real time, which can quickly adapt to the dynamic adjustment requirements of experimental parameters, achieve high-precision and stable adjustment of the back pressure, and ensure the effectiveness of the experimental process and data.

[0008] In some embodiments of the present application, the impeller assembly is connected to a speed regulating device through a transmission shaft, the speed regulating device is signal-connected to the control system, the control system controls the speed regulating device, and the speed regulating device adjusts the speed of the impeller assembly through the transmission shaft.

[0009] In some embodiments of the present application, the speed regulating device is a generator, the generator is arranged outside the end of the water tunnel experimental device, and the mechanical energy generated by the rotation of the impeller assembly is converted into electrical energy by the generator. The arrangement of the generator converts the kinetic energy of the water flow at the end of the water tunnel experimental device into electrical energy, which not only realizes the recovery of energy but also can adjust the back pressure of the water tunnel experimental device.

[0010] In some embodiments of the present application, the generator includes a stator, a rotor and an excitation system. The impeller assembly is connected to the rotor through a transmission shaft. The rotation of the impeller assembly drives the rotation of the rotor. The rotation of the rotor cuts the magnetic induction lines generated by the energization of the stator, and an induced current is generated in the rotor; The excitation system is used to adjust the magnitude of the excitation current, adjust the magnetic field strength generated by the stator, and thus adjust the output power of the generator.

[0011] In some embodiments of the present application, when adjusting the speed of the impeller assembly: When the real-time back pressure value P i is greater than the target back pressure value P T , the control system sends an instruction, the excitation system reduces the excitation current, the magnetic field strength decreases accordingly, the resistance of the impeller assembly to rotate decreases accordingly, the speed of the impeller assembly increases, the resistance generated by the impeller assembly to the water flow decreases, and the real-time back pressure value P i decreases. When the real-time back pressure value decreases to be equal to the target back pressure value P T , the excitation current value of the excitation system at this time is maintained; When the real-time back pressure value P i is less than the target back pressure value P T , the control system sends an instruction, the excitation system increases the excitation current, the magnetic field strength increases accordingly, the resistance of the impeller assembly to rotate increases accordingly, the speed of the impeller assembly decreases, the resistance generated by the impeller assembly to the water flow increases, and the real-time back pressure value P i increases. When the real-time back pressure value increases to be equal to the target back pressure value P T , the excitation current value of the excitation system at this time is maintained.

[0012] In some embodiments of the present application, the pressure sensor monitors the back pressure value of the adjusted water tunnel experimental device in real time, feeds it back to the control system, and adjusts the back pressure value in real time by adjusting the output power of the generator, so that the real-time back pressure value is always stable near the target back pressure value.

[0013] In some embodiments of the present application, the impeller assembly is arranged at the end of the diffuser section of the water tunnel experimental device for collecting the kinetic energy at the end of the water tunnel experimental device; The pressure sensor is arranged in front of the impeller assembly along the water flow direction. After the control system adjusts the output power of the generator, the pressure sensor can monitor the real-time back pressure value of the adjusted diffuser section in real time.

[0014] In some embodiments of the present application, part of the transmission shaft is located in the diffuser section of the water tunnel experimental device, and the end of the transmission shaft located in the diffuser section fixes the impeller assembly; the remaining part of the transmission shaft passes through the wall of the diffuser section and extends axially to the outside, and the end of the transmission shaft located outside the diffuser section is fixed with the generator.

[0015] In some embodiments of the present application, a coupling is arranged at the end of the outer transmission shaft. The coupling is used to connect the transmission shaft and the generator, and is used to transmit the torque of the impeller assembly to the main shaft of the generator. The coupling is also used to compensate for the axial deviation generated by the installation of the transmission shaft and the main shaft of the generator, and plays a role in buffering and vibration reduction during operation to reduce vibration and impact. In addition, the coupling also has an overload protection function to prevent damage to the equipment after overload; A bearing pedestal is arranged on the wall of the diffuser section, and a bearing is arranged at the corresponding position of the transmission shaft. The bearing is fixed on the bearing pedestal so that the transmission shaft can be stably transmitted when passing through the wall of the diffuser section.

[0016] In some embodiments of the present application, the control system is an industrial control computer. The industrial control computer collects the pressure data of the pressure sensor, the rotation speed of the impeller assembly, the excitation current data of the excitation system, and the output power data of the generator, calculates the excitation current value required for back pressure adjustment through the real-time pressure data fed back by the pressure sensor, and sends a control command to the excitation system to realize the output of different powers of the generator.

[0017] Based on the above technical solution, an impeller assembly is arranged in the water tunnel experimental device. The pressure sensor monitors the back pressure inside the water tunnel experimental device in real time. The control system adjusts the rotation speed of the impeller assembly to achieve stepless adjustment of the back pressure. The response speed is slow. Moreover, by monitoring the back pressure in real time and adjusting the rotation speed of the impeller assembly in real time, it can quickly adapt to the dynamic adjustment requirements of experimental parameters, achieve high-precision and stable adjustment of the back pressure, and ensure the effectiveness of the experimental process and data. The setting of the generator enables the kinetic energy of the water flow to be converted into electrical energy by the generator during the process of adjusting the back pressure, realizing the recycling of the kinetic energy of the water flow, significantly improving the energy utilization efficiency of the water tunnel facility, and reducing the operating cost. Through the interlocking control of the pressure signal of the pressure sensor and the excitation current of the generator, stepless and precise control of the back pressure is achieved. It can not only accurately control the cavitation number of the fluid in the test section to ensure the accuracy of experimental data, but also realize the dual functions of automatic adjustment of the back pressure and energy recovery through a closed-loop control system, with the dual advantages of energy conservation, environmental protection and efficient experiments, providing an innovative solution for the sustainable development of the water tunnel device. The present invention not only fills the technical gaps in energy recovery and back pressure adjustment of existing water tunnel experimental facilities, but also provides a more efficient and reliable experimental platform for fields such as underwater equipment research and development and fluid dynamics experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present invention, and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 It is a schematic diagram of the positional relationship between the water tunnel experimental device and the generator according to an embodiment of the present invention. In the figure: 10. Water tunnel experimental device; 11. Diffusion section; 20. Pressure sensor; 30. Impeller assembly; 40. Transmission shaft; 50. Industrial control computer; 60. Coupling; 70. Generator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Next, the technical solutions in the embodiments will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0021] The terms "first", "second", "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third" may explicitly or implicitly include one or more of such features.

[0022] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] As shown in the Figure 1 accompanying drawings, for the backpressure adjustment method of the water tunnel experiment device of this embodiment, a partial structure at the end of the water tunnel experiment device 10 is a diffuser section 11. A pressure sensor 20 is arranged inside the diffuser section 11. An impeller assembly 30 is arranged at the end of the diffuser section 11. The impeller assembly 30 is used to collect the kinetic energy at the end of the diffuser section 11. The impeller assembly 30 rotates under the impact of the water flow, converting the kinetic energy of the water flow at the end of the diffuser section 11 into mechanical energy; the pressure sensor 20 is arranged on the inner wall of the diffuser section 11, close to the impeller assembly 30, and the pressure sensor 20 is located in front of the impeller assembly 30 in the water flow direction. Figure 1 In the figure, the arrow direction is the direction of the water flow. The water flow first passes through the pressure sensor 20 and then passes through the impeller assembly 30. The pressure sensor 20 can accurately monitor the backpressure of the water flow inside the diffuser section 11 and feedback the monitored pressure data to the industrial control computer 50.

[0024] The impeller assembly 30 is connected to a speed adjustment device outside the water tunnel experiment device through a transmission shaft 40. The speed adjustment device is signal-connected to the industrial control computer 50. The industrial control computer can issue an instruction to the speed adjustment device to enable the speed adjustment device to adjust the speed of the impeller assembly 30 through the transmission shaft 40. In some embodiments, the rotational speed regulating device is a motor. The impeller assembly 30 is fixed to the output shaft of the motor through a transmission shaft 40. The motor is signal-connected to an industrial control computer. By adjusting the rotational speed of the output shaft of the motor, the rotational speed of the impeller assembly 30 can be adjusted. At this time, the backpressure regulating method includes the following steps: Obtain the target backpressure value: The industrial control computer 50 sets the required backpressure value under different experimental conditions as the target backpressure value P T ; Calculate the pressure difference: The pressure sensor 20 continuously monitors the real-time backpressure value P of the diffuser section 11 i , and the difference between the target backpressure value and the real-time backpressure value is used as the calculated pressure difference ΔP i : ΔP i =P T -P i ; Adjust the rotational speed of the impeller assembly 30: The industrial control computer 50 adjusts the rotational speed of the impeller assembly 30 according to the positive or negative and the absolute value size of ΔP i , specifically: When the real-time backpressure value P i is greater than the target backpressure value P T , ΔP i >0. The industrial control computer calculates the rotational speed required to adjust the backpressure according to the value of ΔP i , and sends a control command to the motor. The rotational speed output by the motor increases, and the rotational speed of the impeller assembly 30 increases accordingly, so that the resistance generated by the impeller assembly 30 on the water flow decreases, and the real-time backpressure value P i will decrease. When the real-time backpressure value is equal to the target backpressure value P T , maintain the rotational speed of the motor at this time; When the real-time backpressure value P i is less than the target backpressure value P T , ΔP i <0. The industrial control computer 50 calculates the rotational speed required to adjust the backpressure according to the absolute value of ΔP i , and sends a control command to the motor. The rotational speed output by the motor decreases, and the rotational speed of the impeller assembly 30 decreases accordingly, so that the resistance generated by the impeller assembly 30 on the water flow increases, and the real-time backpressure value P i will increase. When the real-time backpressure value is equal to the target backpressure value P T , maintain the rotational speed of the motor at this time; The pressure sensor 20 continuously monitors the backpressure value of the adjusted diffuser section 11 and feeds it back to the industrial control computer 50. When the backpressure value deviates from the target backpressure value, the rotational speed of the output shaft of the motor is adjusted in time to perform real-time adjustment on the backpressure value, so that the real-time backpressure value is always stabilized near the target backpressure value.

[0025] In some embodiments, the rotational speed adjusting device is a generator 70. As shown Figure 1 in the figure, the generator 70 is arranged outside the diffuser section 11. The mechanical energy generated by the rotation of the impeller assembly 30 is converted into electrical energy by the generator 70. The arrangement of the generator 70 converts the kinetic energy of the water flow at the end of the diffuser section 11 of the water tunnel experimental device into electrical energy, achieving energy recovery.

[0026] The generator 70 includes a stator, a rotor, and an excitation system. The stator is a fixed coil, and the rotor is a rotating coil. The impeller assembly 30 is connected to the rotor through a transmission shaft 40. The rotation of the impeller assembly 30 drives the rotation of the rotor. The rotor rotates to cut the magnetic induction lines, generating an induced current in the rotor. The stator generates fixed magnetic induction lines through the excitation current, and the excitation system is used to adjust the magnitude of the excitation current, adjust the magnetic field strength generated by the stator, and thus adjust the output power of the generator.

[0027] According to the principle of electromagnetic induction, when the rotor cuts the magnetic induction lines, an induced current is generated in the rotor coil, thereby converting mechanical energy into electrical energy. By controlling the magnitude of the excitation current in the stator, the rotational speed of the rotor can be adjusted. The rotational speed of the rotor affects the rotational speed of the impeller assembly 30, and thus the water flow pressure at the end diffuser section is adjusted, thereby controlling the back pressure.

[0028] In some embodiments, a part of the transmission shaft 40 is located inside the diffuser section 11, and the end of the transmission shaft located inside the diffuser section 11 fixes the impeller assembly 30; the remaining part of the transmission shaft 40 passes through the pipe wall at the position where the diffuser section 11 exits and extends axially along the transmission shaft 40 to the outside. The end of the transmission shaft 40 located outside the diffuser section 11 is connected to the rotor of the generator 70.

[0029] In order to stably transmit the torque of the impeller assembly 30, a coupling 60 is provided at the end of the transmission shaft 40 located on the outside. The coupling 60 is used to connect the transmission shaft 40 and the rotor of the generator 70. The coupling 60 transmits the torque of the impeller assembly 30 to the rotor of the generator. The coupling 60 can also compensate for the axial deviation between the transmission shaft 40 and the main shaft of the generator rotor due to installation, and play a role in buffering and vibration reduction during operation to reduce vibration and impact. In addition, the coupling 60 also has an overload protection function to prevent damage to the equipment after overload; A bearing pedestal (not shown in the figure) is provided on the pipe wall of the diffuser section 11. A bearing is provided at the corresponding position where the transmission shaft 40 passes through the pipe wall, and the bearing is fixed on the bearing pedestal, enabling the transmission shaft to transmit stably when passing through the pipe wall of the diffuser section 11. When the rotational speed adjusting device is the generator 70, the back pressure of the diffuser section 11 is also adjusted by adjusting the rotational speed of the impeller assembly 30. Specifically: When the real-time back pressure value P i is greater than the target back pressure value P TWhen ΔP i > 0, the industrial control computer calculates the exciting current required to adjust the back pressure according to the value of ΔP i . The industrial control computer 50 sends an instruction, and the excitation system reduces the exciting current to the required magnitude. The magnetic field strength decreases accordingly, the resistance to the rotation of the rotor decreases, and the resistance to the rotation of the impeller assembly 30 decreases accordingly. The rotational speed of the impeller assembly 30 increases, the resistance generated by the impeller assembly to the water flow decreases, and the real-time back pressure value P i decreases. When the real-time back pressure value decreases to be equal to the target back pressure value P T , the exciting current value of the excitation system at this time is maintained; When the real-time back pressure value P i is less than the target back pressure value P T , ΔP i < 0. The industrial control computer calculates the exciting current required to adjust the back pressure according to the absolute value of ΔP i . The industrial control computer 50 sends an instruction, and the excitation system increases the exciting current to the required magnitude. The magnetic field strength increases accordingly, the resistance to the rotation of the rotor increases, and the resistance to the rotation of the impeller assembly 30 increases accordingly. The rotational speed of the impeller assembly 30 decreases, the resistance generated by the impeller assembly 30 to the water flow increases, and the real-time back pressure value P i increases. When the real-time back pressure value increases to be equal to the target back pressure value P T , the exciting current value of the excitation system at this time is maintained.

[0030] The pressure sensor 20 monitors the back pressure value of the adjusted diffuser section in real time, feeds it back to the industrial control computer 50, and adjusts the back pressure value in real time by adjusting the magnitude of the exciting current, so that the real-time back pressure value is always stable near the target back pressure value.

[0031] In this embodiment, the industrial control computer 50 collects the pressure data of the pressure sensor 20, the rotational speed of the impeller assembly 30, the exciting current data of the excitation system, and the output power data of the generator, calculates the exciting current value required for back pressure adjustment through the real-time pressure data fed back by the pressure sensor 20, and sends a control instruction to the excitation system to achieve the output of different powers of the generator.

[0032] Based on the above technical solution, an impeller assembly is arranged in the water tunnel experimental device. The pressure sensor monitors the back pressure inside the water tunnel experimental device in real time. The control system adjusts the rotational speed of the impeller assembly to achieve stepless adjustment of the back pressure. The response speed is slow, and the back pressure is monitored in real time and the rotational speed of the impeller assembly is adjusted in real time, which can quickly adapt to the dynamic adjustment requirements of experimental parameters, achieve high-precision and stable adjustment of the back pressure, and ensure the effectiveness of the experimental process and data; The generator is configured such that during the process of adjusting the back pressure, the kinetic energy of the water flow is converted into electrical energy by the generator, realizing the recycling of the kinetic energy of water flow, significantly improving the energy utilization efficiency of the water tunnel facility, and reducing the operating cost; Through the linkage control of the pressure signal of the pressure sensor and the excitation current of the generator, the stepless and precise regulation of the back pressure is achieved. It can not only accurately control the cavitation number of the fluid in the test section to ensure the accuracy of experimental data, but also realize the dual functions of automatic regulation of the back pressure and energy recovery through the closed-loop control system, with the dual advantages of energy conservation, environmental protection and efficient experiments, providing an innovative solution for the sustainable development of the water tunnel device; The present invention not only fills the technical gaps in energy recovery and back pressure regulation of existing water tunnel experimental facilities, but also provides a more efficient and reliable experimental platform for fields such as the research and development of underwater equipment and fluid dynamics experiments.

[0033] Finally, it should be noted that the embodiments in this specification are described in a progressive manner, and the key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications can still be made to the specific implementation manners of the present invention or equivalent replacements can be made to some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A back pressure adjustment method for a water tunnel experiment device, characterized in that: An impeller assembly and a pressure sensor are arranged inside the water tunnel experimental device. The impeller assembly rotates under the impact of water flow, converting the kinetic energy of water flow into mechanical energy. The pressure sensor is signal-connected to a control system; The backpressure adjustment method includes the following steps: Obtain the target backpressure value: The control system sets the required back pressure value under different experimental conditions as the target back pressure value P T ; Calculate the pressure difference: The pressure sensor monitors the real-time back pressure value P of the water tunnel experimental device in real time i , and the difference between the target back pressure value and the real-time back pressure value is used as the calculated pressure difference ΔP i : ΔP i =P T -P i ; Adjust the rotational speed of the impeller assembly: The control system adjusts the rotational speed of the impeller assembly according to the positive or negative value and the absolute value of ΔP i : When the real-time back pressure value P i is greater than the target back pressure value P T , the rotational speed of the impeller assembly is increased, so that the resistance generated by the impeller assembly on the water flow decreases. At this time, the real-time back pressure value P i decreases until the real-time back pressure value is equal to the target back pressure value P T , and the rotational speed of the impeller assembly at this time is maintained; When the real-time back pressure value P i is less than the target back pressure value P T , reduce the rotational speed of the impeller assembly, so that the resistance of the impeller assembly to the flowing water increases. At this time, the real-time back pressure value P i rises until the real-time back pressure value is equal to the target back pressure value P T , and maintain the rotational speed of the impeller assembly at this time; The pressure sensor monitors the adjusted backpressure value in real time, feeds it back to the control system, and adjusts the backpressure value in real time, so that the real-time backpressure value is always stable near the target backpressure value.

2. The backpressure adjustment method of the water tunnel experiment device according to claim 1, characterized in that, The impeller assembly is connected to a rotational speed adjustment device through a transmission shaft. The rotational speed adjustment device is signal-connected to the control system. The control system controls the rotational speed adjustment device, and the rotational speed adjustment device adjusts the rotational speed of the impeller assembly through the transmission shaft.

3. The backpressure adjustment method of the water tunnel experiment device according to claim 2, characterized in that, The rotational speed adjustment device is a generator. The generator is arranged outside the end of the water tunnel experimental device. The mechanical energy generated by the rotation of the impeller assembly is converted into electrical energy by the generator. The setting of the generator converts the kinetic energy of the water flow at the end of the water tunnel experimental device into electrical energy, which not only realizes the recovery of energy but also can adjust the backpressure of the water tunnel experimental device.

4. The backpressure adjustment method of the water tunnel experiment device according to claim 3, characterized in that, The generator includes a stator, a rotor, and an excitation system. The impeller assembly is connected to the rotor through a transmission shaft. The rotation of the impeller assembly drives the rotation of the rotor. The rotation of the rotor cuts the magnetic induction lines generated by the energization of the stator, generating an induced current in the rotor; The excitation system is used to adjust the magnitude of the excitation current, adjust the magnetic field strength generated by the stator, and thus adjust the output power of the generator.

5. The back pressure adjustment method of the water tunnel experiment device according to claim 4, characterized in that, When adjusting the rotational speed of the impeller assembly: When the real-time backpressure value P i is greater than the target backpressure value P T , the control system sends an instruction, the excitation system reduces the excitation current, the magnetic field strength decreases accordingly, the resistance of the impeller assembly to rotation decreases accordingly, the rotational speed of the impeller assembly increases, the resistance generated by the impeller assembly on the water flow decreases, and the real-time backpressure value P i decreases. When the real-time backpressure value decreases to be equal to the target backpressure value P T , the excitation current value of the excitation system at this time is maintained; When the real-time back pressure value P i is less than the target back pressure value P T , the control system sends an instruction, the excitation system increases the excitation current, the magnetic field strength increases accordingly, the resistance of the impeller assembly to rotation increases accordingly, the rotational speed of the impeller assembly decreases, the resistance of the impeller assembly to the water flow increases, and the real-time back pressure value P i increases. When the real-time back pressure value increases to be equal to the target back pressure value P T , the excitation current value of the excitation system at this time is maintained.

6. The backpressure adjustment method of the water tunnel experiment device according to claim 5, characterized in that The pressure sensor monitors the adjusted backpressure value of the water tunnel experimental device in real time, feeds it back to the control system, and adjusts the backpressure value in real time by adjusting the output power of the generator, so that the real-time backpressure value is always stable near the target backpressure value.

7. The back pressure adjustment method of the water tunnel experiment device according to claim 3, characterized in that The impeller assembly is arranged at the end of the diffuser section of the water tunnel experimental device, and is used to collect the kinetic energy at the end of the water tunnel experimental device; The pressure sensor is arranged in front of the impeller assembly along the water flow direction. After the control system adjusts the output power of the generator, the pressure sensor can monitor the real-time backpressure value of the adjusted diffuser section in real time.

8. The back pressure adjustment method of the water tunnel experiment device according to claim 7, characterized in that Part of the transmission shaft is located inside the diffuser section of the water tunnel experimental device, and the end of the transmission shaft located inside the diffuser section fixes the impeller assembly; the remaining part of the transmission shaft passes through the wall of the diffuser section and extends axially to the outside. The end of the transmission shaft located outside the diffuser section is fixed with the generator.

9. The back pressure adjustment method of the water tunnel experiment device according to claim 8, characterized in that, A coupling is arranged at the end of the transmission shaft located on the outside. The coupling is used to connect the transmission shaft and the generator. The coupling is used to transmit the torque of the impeller assembly to the main shaft of the generator. The coupling is also used to compensate for the axial deviation generated by the installation of the transmission shaft and the main shaft of the generator, and plays a role in buffering and vibration reduction during operation to reduce vibration and impact. In addition, the coupling also has an overload protection function to prevent damage to the equipment after overload; A bearing base is provided on the tube wall of the diffuser section, and bearings are provided at corresponding positions of the transmission shaft. The bearings are fixed on the bearing base so that the transmission shaft can stably transmit power when passing through the tube wall of the diffuser section.

10. The back pressure adjustment method of the water tunnel experiment device according to claim 4, characterized in that, The control system is an industrial control computer. The industrial control computer collects the pressure data of the pressure sensor, the rotation speed of the impeller assembly, the excitation current data of the excitation system, and the output power data of the generator. It calculates the excitation current value required for backpressure regulation based on the real-time pressure data fed back by the pressure sensor, and sends control instructions to the excitation system to achieve the output of different powers of the generator.

Images