Method and system for drawing pressure pulsation equivalent strength of draft tube of axial flow water turbine

Abstract

The invention relates to an axial flow water turbine draft tube pressure pulsation equivalent strength drawing method and system, and the method comprises the following steps: determining the position and number of pressure pulsation monitoring points in an axial flow water turbine draft tube, and arranging a pressure sensor at each point, so as to obtain a pressure signal in an acquisition period, and form a time domain signal of pressure pulsation. And determining a pressure pulsation equivalent strength weighting factor of the draft tube, and calculating the pressure pulsation strength of each monitoring point on the tube wall. And establishing a mathematical model of the pressure pulsation equivalent strength of the draft tube by using the data, so as to obtain the pressure pulsation equivalent strength of the draft tube of the axial flow water turbine. And drawing a draft tube pressure pulsation equivalent strength contour map according to the equivalent strength. According to the method, the whole pressure pulsation equivalent strength of the draft tube is accurately calculated by constructing the model and combining the pressure pulsation strength and the weighting factor of each monitoring point. The method not only improves the calculation accuracy, but also provides theoretical support for optimization and improvement.

Description

Technical Field

[0001] The present invention relates to a method and system for drawing the equivalent intensity of pressure pulsation in the draft tube of an axial-flow turbine, belonging to the technical fields of mechanical engineering and fluid dynamics. Background Technique

[0002] As a kind of hydraulic power generation equipment widely used in low-head and large-flow hydropower stations, the operation stability of an axial-flow turbine is crucial for the economy and safety of the power station. During the operation of the turbine, the pressure pulsation in the draft tube is an important technical problem. The pressure pulsation will not only cause the vibration and noise of the unit to increase, but may also lead to fatigue damage of the equipment, affecting the operation efficiency and service life of the turbine. The pressure pulsation in the draft tube is mainly caused by the tail water vortex band, cavitation phenomenon and complex flow states. The traditional pressure pulsation monitoring method mainly relies on single-point pressure sensors and cannot comprehensively reflect the complex flow state inside the draft tube. This method can only obtain local pressure pulsation information and is difficult to capture the overall pressure distribution law of the draft tube, resulting in inaccurate evaluation of the pressure pulsation. When dealing with pressure pulsation signals, the traditional method often adopts simple time-domain or frequency-domain analysis and is difficult to effectively extract the dynamic characteristics in the signals. For example, the traditional Fourier transform method cannot process non-linear and non-stationary signals, resulting in inaccurate analysis results.

[0003] The patent document with the patent number "CN109185211A" discloses a method for predicting the pressure pulsation of a pump station unit based on instantaneous calculation of computational fluid dynamics. Although this method can predict pressure pulsation through CFD simulation and time-frequency analysis, when dealing with complex flow phenomena (such as vortex bands, cavitation, etc.) inside the draft tube, it may not be able to accurately capture their dynamic changes. This is because its analysis method is mainly based on empirical mode decomposition and instantaneous calculation, and has limited understanding of the physical essence of complex flows. Although the main frequency and amplitude of pressure pulsation can be analyzed through the time-frequency spectrum diagram, this analysis result is relatively abstract and it is difficult to intuitively display the spatial distribution of pressure pulsation inside the draft tube. Engineers need to conduct complex spectrum analysis to understand the distribution law of pressure pulsation, which increases the analysis difficulty and time cost. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention proposes a method and system for drawing the equivalent intensity of pressure pulsation in the draft tube of an axial-flow turbine.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, the present invention provides a method for drawing the equivalent intensity of pressure pulsation in the draft tube of an axial-flow turbine, including the following steps:

[0007] Determine the deployment positions and quantities of the internal pressure pulsation monitoring points of the draft tube of the axial-flow turbine, and arrange pressure sensors at each monitoring point;

[0008] Obtain the pressure signals collected by each pressure sensor during the acquisition period to form the time-domain signals of the pressure pulsation;

[0009] Determine the equivalent intensity weighting factor of the pressure pulsation of the draft tube of the axial-flow turbine;

[0010] Calculate the pressure pulsation intensity at each monitoring point on the draft tube wall of the axial-flow turbine;

[0011] Establish a mathematical model of the equivalent intensity of the draft tube pressure pulsation based on the equivalent intensity weighting factor of the draft tube pressure pulsation of the axial-flow turbine and the pressure pulsation intensity at each monitoring point, and obtain the equivalent intensity of the draft tube pressure pulsation of the axial-flow turbine through the mathematical model of the equivalent intensity of the draft tube pressure pulsation;

[0012] Draw an isogram of the equivalent intensity of the draft tube pressure pulsation according to the equivalent intensity of the draft tube pressure pulsation of the axial-flow turbine.

[0013] As a preferred implementation method, the internal pressure pulsation monitoring points of the draft tube are deployed on the draft tube wall surface at a distance of 1.0 times the runner diameter from the inlet of the draft tube, and are arranged at the same interval angle around the cross-section of the draft tube;

[0014] The interval angle between each monitoring point is expressed as:

[0015]

[0016] where ω represents the rotational angular velocity of the runner;

[0017] The number of monitoring points is pieces.

[0018] As a preferred implementation method, each pressure sensor collects 180x pressure signals during a single acquisition period, where x is an integer in the interval [1, 10];

[0019] The number of acquisition periods is not less than 3 times, and the maximum value P max and the minimum value P min of the pressure pulsation are recorded during the last three acquisition periods.

[0020] As a preferred implementation method, the equivalent intensity weighting factor C of the draft tube pressure pulsation is expressed as:

[0021]

[0022] where C represents the equivalent intensity weighting factor of the draft tube pressure pulsation.

[0023] As a preferred embodiment, the calculation method of the pressure pulsation intensity is as follows:

[0024]

[0025] where represents the pressure pulsation intensity at the i-th monitoring point, ρ represents the density of water, g represents the acceleration due to gravity, and H 净 represents the net head of the axial flow turbine, represents the square of the maximum value P max of the pressure pulsation, represents the square of the minimum value P min of the pressure pulsation.

[0026] As a preferred embodiment, the mathematical model of the equivalent intensity of the draft tube pressure pulsation is expressed as:

[0027]

[0028] where P ei represents the equivalent intensity of the draft tube pressure pulsation of the axial flow turbine.

[0029] On the other hand, the present invention also provides a system for plotting the equivalent intensity of the draft tube pressure pulsation of an axial flow turbine, including:

[0030] Pressure sensor module: Determine the deployment positions and quantities of the internal pressure pulsation monitoring points of the draft tube of the axial flow turbine, and arrange pressure sensors at each monitoring point;

[0031] Data acquisition module: Obtain the pressure signals collected by each pressure sensor during the acquisition period to form a time-domain signal of the pressure pulsation;

[0032] Equivalent intensity weighting factor module of the pressure pulsation: Determine the equivalent intensity weighting factor of the draft tube pressure pulsation of the axial flow turbine;

[0033] Pressure pulsation intensity module: Calculate the pressure pulsation intensity at each monitoring point on the wall of the draft tube of the axial flow turbine;

[0034] Mathematical model module of the equivalent intensity of the draft tube pressure pulsation: Establish a mathematical model of the equivalent intensity of the draft tube pressure pulsation according to the equivalent intensity weighting factor of the draft tube pressure pulsation of the axial flow turbine and the pressure pulsation intensity at each monitoring point, and obtain the equivalent intensity of the draft tube pressure pulsation of the axial flow turbine through the mathematical model of the equivalent intensity of the draft tube pressure pulsation;

[0035] Contour map module of the equivalent intensity of the draft tube pressure pulsation: Plot a contour map of the equivalent intensity of the draft tube pressure pulsation according to the equivalent intensity of the draft tube pressure pulsation of the axial flow turbine.

[0036] The present invention has the following beneficial effects:

[0037] By reasonably deploying pressure pulsation monitoring points inside the draft tube, the present invention can accurately capture the pressure changes inside the draft tube. The monitoring points are deployed on the draft tube wall surface at a distance of 1.0 times the runner diameter from the inlet of the draft tube and are arranged at the same interval angle. This layout method can comprehensively cover the key areas of the draft tube, ensuring the comprehensiveness and representativeness of data collection. Pressure signals are obtained through pressure sensors during the acquisition period to form the time-domain signal of pressure pulsation. This method can monitor the dynamic changes of pressure pulsation in real time and provide high-precision original data for subsequent analysis. The equivalent intensity weighting factor of the draft tube pressure pulsation is introduced, which can comprehensively consider the influence of the pressure pulsation intensity at different monitoring points on the overall draft tube. This weighted processing method makes the evaluation results more scientific and reasonable, avoiding the errors that may be brought by simple average processing. By establishing a mathematical model of the equivalent intensity of the draft tube pressure pulsation and combining the pressure pulsation intensity at each monitoring point with the weighting factor, the overall equivalent intensity of the draft tube pressure pulsation can be accurately calculated. This model-based method not only improves the calculation accuracy but also provides a theoretical basis for subsequent optimization and improvement. Finally, by drawing the contour map of the equivalent intensity of the draft tube pressure pulsation, the complex pressure pulsation data is presented in an intuitive way. This visualization means can help engineers quickly identify the distribution law of pressure pulsation, high-risk areas, and potential flow problems, facilitating targeted optimization design. Brief Description of the Drawings

[0038] Figure 1 It is a flowchart of the implementation of the method of the present invention.

[0039] Figure 2 It is a schematic diagram of the layout position of the longitudinal section of the axial-flow turbine of the present invention.

[0040] Figure 3 It is a schematic diagram of the layout position of the cross-section of the draft tube of the axial-flow turbine of the present invention.

[0041] Figure 4 It is a sample drawing of the contour map of the equivalent intensity of the draft tube pressure pulsation of the present invention. Detailed Embodiment

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying 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 making creative efforts belong to the protection scope of the present invention.

[0043] It should be understood that the step numbers used in the text are only for convenience of description and do not limit the order of execution of the steps.

[0044] It should be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0045] The terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0046] The term "and / or" refers to any combination and all possible combinations of one or more of the associated listed items and includes these combinations.

[0047] Embodiment 1:

[0048] See Figure 1 , the present invention provides a method for drawing the equivalent intensity of pressure pulsation of the draft tube of an axial flow turbine, including the following steps:

[0049] Determine the deployment positions and quantities of the internal pressure pulsation monitoring points of the draft tube of the axial flow turbine, and arrange pressure sensors at each monitoring point;

[0050] Obtain the time-domain signals of the pressure pulsations formed by the pressure signals collected by each pressure sensor during the acquisition period;

[0051] Determine the equivalent intensity weighting factor of the pressure pulsation of the draft tube of the axial flow turbine;

[0052] Calculate the pressure pulsation intensity at each monitoring point on the draft tube wall of the axial flow turbine;

[0053] Establish a mathematical model of the equivalent intensity of pressure pulsation of the draft tube according to the equivalent intensity weighting factor of the pressure pulsation of the draft tube of the axial flow turbine and the pressure pulsation intensity at each monitoring point, and obtain the equivalent intensity of pressure pulsation of the draft tube of the axial flow turbine through the mathematical model of the equivalent intensity of pressure pulsation of the draft tube;

[0054] See Figure 4 , draw an isogram of the equivalent intensity of pressure pulsation of the draft tube according to the equivalent intensity of pressure pulsation of the draft tube of the axial flow turbine.

[0055] Figure 4 In

[0056] SeeFigures 2-3 , as a preferred embodiment, the internal pressure pulsation monitoring points of the draft tube are deployed on the draft tube wall surface at a distance of 1.0 times the runner diameter from the draft tube inlet, and are arranged at the same interval angle around the cross-section of the draft tube;

[0057] The interval angle between each monitoring point is expressed as:

[0058]

[0059] where ω represents the rotational angular velocity of the runner;

[0060] The number of monitoring points is pieces.

[0061] , as a preferred embodiment, each pressure sensor collects 180x pressure signals in a single acquisition cycle, where x is an integer in the interval [1, 10];

[0062] The number of acquisition cycles is not less than 3 times, and the maximum value P max and the minimum value P min of the pressure pulsation are recorded in the last three acquisition cycles.

[0063] Fully considering that the influence of the low-frequency vortex band generated in the draft tube under off-design conditions on the pressure fluctuation around the draft tube wall is different, the equivalent intensity weighting factor C of the draft tube pressure pulsation fully relates to the azimuth problem between the positions of different monitoring points on the wall and the draft tube outlet, optimizes the weighted intensity of the pressure pulsation, and makes the single pressure pulsation weighting factor scientific for engineering applications.

[0064] , as a preferred embodiment, the equivalent intensity weighting factor C of the draft tube pressure pulsation is expressed as:

[0065]

[0066] where C represents the equivalent intensity weighting factor of the draft tube pressure pulsation.

[0067] Combining the maximum and minimum values of the pressure pulsation in the last three cycles collected at each point, and the density ρ of the concentrated water flow in the mathematical model of the pressure pulsation intensity at a single point, calculate the pressure pulsation intensity P i * at each monitoring point on the draft tube wall of the axial flow turbine.

[0068] , as a preferred embodiment, the calculation method of the pressure pulsation intensity is:

[0069]

[0070] where, It represents the pressure pulsation intensity at the i-th monitoring point, ρ represents the density of water, g represents the acceleration due to gravity, and H 净 represents the net head of the unit. The net head refers to the differential head between the inlet of the water turbine and the outlet of the draft tube. It represents the square of the maximum value P max of the pressure pulsation. It represents the square of the minimum value P min of the pressure pulsation.

[0071] By comprehensively considering the pressure pulsation intensity of the vortex band at different positions in the draft tube, the pressure pulsation intensity and characteristics caused by the vortex band in the draft tube under different off-design conditions are calculated and summarized.

[0072] As a preferred embodiment, the mathematical model of the equivalent intensity of the draft tube pressure pulsation is expressed as:

[0073]

[0074] where P ei represents the equivalent intensity of the draft tube pressure pulsation of the axial flow water turbine.

[0075] Embodiment 2:

[0076] The present invention also provides a system for drawing the equivalent intensity of the draft tube pressure pulsation of an axial flow water turbine, including:

[0077] Pressure sensor module: Determine the deployment positions and quantities of the internal pressure pulsation monitoring points of the draft tube of the axial flow water turbine, and arrange pressure sensors at each monitoring point;

[0078] Data acquisition module: Obtain the pressure signals collected by each pressure sensor during the acquisition period to form the time-domain signal of the pressure pulsation;

[0079] Equivalent intensity weighting factor module of the pressure pulsation: Determine the equivalent intensity weighting factor of the draft tube pressure pulsation of the axial flow water turbine;

[0080] Pressure pulsation intensity module: Calculate the pressure pulsation intensity at each monitoring point on the draft tube wall of the axial flow water turbine;

[0081] Mathematical model module of the equivalent intensity of the draft tube pressure pulsation: Establish a mathematical model of the equivalent intensity of the draft tube pressure pulsation according to the equivalent intensity weighting factor of the draft tube pressure pulsation of the axial flow water turbine and the pressure pulsation intensity at each monitoring point, and obtain the equivalent intensity of the draft tube pressure pulsation of the axial flow water turbine through the mathematical model of the equivalent intensity of the draft tube pressure pulsation;

[0082] Contour map module of the equivalent intensity of the draft tube pressure pulsation: Draw a contour map of the equivalent intensity of the draft tube pressure pulsation according to the equivalent intensity of the draft tube pressure pulsation of the axial flow water turbine.

[0083] This system is used to implement the method in the first embodiment, which will not be elaborated here.

[0084] In the embodiments of the present application, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent the situation where A exists alone, A and B exist simultaneously, or B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. "At least one of the following" and its similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0085] Those of ordinary skill in the art can realize that the various units and algorithm steps described in the embodiments disclosed herein can be implemented by a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. A professional technician can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0086] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the system, device, and unit described above can refer to the corresponding processes in the foregoing method embodiments, which will not be elaborated here.

[0087] In several embodiments provided by the present application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (hereinafter referred to as ROM), random access memories (hereinafter referred to as RAM), magnetic disks, or optical discs that can store program codes.

[0088] The above are only embodiments of the present invention, and do not thus limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall similarly be included within the patent protection scope of the present invention.

Claims

1. A method for drawing the equivalent intensity of pressure pulsation in the tail tube of an axial flow turbine, characterized in that: The following steps are involved: Determine the deployment location and number of pressure pulsation monitoring points inside the draft tube of the axial flow turbine, and arrange pressure sensors at each monitoring point; Obtaining a time domain signal of pressure pulsation formed by pressure signals collected by each pressure sensor during a collection period; Determine the equivalent intensity weighting factor of the pressure pulsation in the draft tube of an axial flow turbine; Calculate the pressure pulsation intensity at each monitoring point on the draft tube wall of an axial flow turbine; According to the weighted factor of the pressure pulsation equivalent intensity of the draft tube of the axial flow turbine and the pressure pulsation intensity of each monitoring point, a mathematical model of the pressure pulsation equivalent intensity of the draft tube of the axial flow turbine is established, and the pressure pulsation equivalent intensity of the draft tube of the axial flow turbine is obtained through the mathematical model of the pressure pulsation equivalent intensity of the draft tube of the axial flow turbine; According to the equivalent intensity of pressure pulsation in the tailwater tube of the axial flow turbine, a contour diagram of the equivalent intensity of pressure pulsation in the tailwater tube is drawn.

2. The method for drawing equivalent intensity of pressure pulsation of axial flow turbine tail tube according to claim 1, characterized in that: The tailwater pipe internal pressure pulsation monitoring points are deployed at the tailwater pipe wall surface 1.0 times the runner diameter away from the tailwater pipe inlet, and are arranged at the same interval angle around the tailwater pipe cross section; The interval angle between each monitoring point It is expressed as: Where ω represents the angular velocity of the wheel; The number of monitoring points is indivual.

3. The method for drawing equivalent intensity of pressure pulsation of axial flow turbine tail tube according to claim 2, characterized in that: Each pressure sensor collects 180x pressure signals in a single collection cycle, where x is an integer in the interval [1,10]; The number of acquisition cycles is not less than 3 times, and the maximum value P of the pressure pulsation is recorded in the last three acquisition cycles. max and the minimum value P min .

4. The method for drawing equivalent intensity of pressure pulsation of axial flow turbine tail tube according to claim 3, characterized in that: The equivalent intensity weighting factor C of the tailwater pressure pulsation is expressed as: Wherein, C represents the equivalent intensity weighting factor of the tailwater pressure pulsation.

5. The method for drawing equivalent intensity of pressure pulsation of axial flow turbine tail tube according to claim 4, characterized in that: The calculation method of the pressure pulsation intensity is: in, represents the pressure pulsation intensity of the ith monitoring point, ρ represents the density of water, g represents the acceleration of gravity, Hnet represents the net water head of the axial flow turbine, Indicates the maximum value of pressure pulsation P max The square of Indicates the minimum value of pressure pulsation P min The square of .

6. The method for drawing equivalent intensity of pressure pulsation of axial flow turbine tail tube according to claim 5, characterized in that: The mathematical model of equivalent strength of tailwater pressure pulsation is expressed as: Among them, P ei It represents the equivalent intensity of pressure pulsation in the tailwater tube of an axial flow turbine.

7. Axial flow turbine tailwater tube pressure pulsation equivalent intensity drawing system, characterized in that: include: Pressure sensor module: determine the deployment location and number of pressure pulsation monitoring points inside the draft tube of the axial flow turbine, and arrange pressure sensors at each monitoring point; Data acquisition module: obtains the pressure signal collected by each pressure sensor during the collection period to form a time domain signal of pressure pulsation; Pressure pulsation equivalent intensity weighting factor module: determines the pressure pulsation equivalent intensity weighting factor of the draft tube of the axial flow turbine; Pressure pulsation intensity module: calculates the pressure pulsation intensity of each monitoring point on the wall of the tailwater tube of the axial flow turbine; Draft tube pressure pulsation equivalent strength mathematical model module: a draft tube pressure pulsation equivalent strength mathematical model is established based on the pressure pulsation equivalent strength weighting factor of the axial flow turbine draft tube and the pressure pulsation strength of each monitoring point. The pressure pulsation equivalent strength of the axial flow turbine draft tube is obtained through the draft tube pressure pulsation equivalent strength mathematical model; Draft tube pressure pulsation equivalent intensity contour map module: Draw the draft tube pressure pulsation equivalent intensity contour map according to the pressure pulsation equivalent intensity of the axial flow turbine draft tube.

8. The axial flow turbine tail tube pressure pulsation equivalent intensity drawing system according to claim 7, characterized in that: The tailwater pipe internal pressure pulsation monitoring points are deployed at the tailwater pipe wall surface 1.0 times the runner diameter away from the tailwater pipe inlet, and are arranged at the same interval angle around the tailwater pipe cross section; The interval angle between each monitoring point It is expressed as: Where ω represents the angular velocity of the wheel; The number of monitoring points is indivual.

9. The axial flow turbine tail tube pressure pulsation equivalent intensity drawing system according to claim 7, characterized in that: Each pressure sensor collects 180*x pressure signals in a single collection cycle, where x is an integer in the interval [1,10]; The number of acquisition cycles is not less than 3 times, and the maximum value P of the pressure pulsation is recorded in the last three acquisition cycles. max and the minimum value P min .

10. The axial flow turbine tail tube pressure pulsation equivalent intensity drawing system according to claim 8, characterized in that: The equivalent intensity weighting factor C of the tailwater pressure pulsation is expressed as: Wherein, C represents the equivalent intensity weighting factor of the tailwater pressure pulsation.

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