Waveguide rod design method for assisting sound signal acquisition of drain valve of power plant

Abstract

The invention discloses a waveguide rod design method for assisting in power plant drain valve sound signal acquisition, and relates to the technical field of power plant equipment monitoring and acoustic sensing, and the method comprises the following steps: S1, determining the shape, material and size parameters of a waveguide rod; s2, performing thermal simulation on the waveguide rod with the determined shape, material and size parameters to obtain an axial temperature response curve of the waveguide rod, and determining the lowest rod length of the waveguide rod based on the axial temperature response curve of the waveguide rod and the working environment temperature of the sonic sensor; and S3, performing energy distribution characteristic analysis on the waveguide rod meeting the lowest rod length, analyzing the energy distribution characteristic of the waveguide rod in the sound frequency band of the drain valve, obtaining the sound wave energy loss of the sound signal in the transmission process of the waveguide rod, and judging whether the waveguide rod meets the design requirement or not based on the sound wave energy loss. The wave guide rod designed by the invention causes little sound intensity loss in the process of transmitting sound wave signals, does not influence the collected sound signals, and is a reliable wave guide tool.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power plant equipment monitoring and acoustic sensing technology, more particularly to a waveguide rod design method for assisting power plant drain valve sound signal collection, which can efficiently conduct acoustic signals during the operation of the drain valve and adapt to high-temperature, high-pressure and high-noise industrial environments, and is suitable for valve state monitoring and fault diagnosis systems based on acoustic characteristics. BACKGROUND

[0002] The main function of the sound waveguide rod is to transmit sound signals from one end of the rod to the other end of the rod, while minimizing signal attenuation. The shape, material and size of the waveguide rod are studied in terms of heat dissipation, and the signal transmission characteristics of the waveguide rod are analyzed.

[0003] The power plant drain valve produces specific acoustic signals (such as leakage sound, cavitation noise, mechanical vibration sound) during operation, but the on-site environment is noisy (such as steam flow, pipe vibration), making signal collection difficult. Direct installation of acoustic sensors is easily affected by high temperature (>100℃) and high pressure environment, and it is difficult to accurately locate the sound source. Ordinary waveguide rods are prone to thermal deformation at high temperatures, resulting in distortion of sound wave transmission, and lack of optimization design for specific frequency bands (100Hz~15kHz) of the drain valve. SUMMARY

[0004] In order to overcome the defects existing in the prior art, the present application discloses a waveguide rod design method for assisting power plant drain valve sound signal collection. The purpose of the present application is to solve the problem of ordinary waveguide rods in the prior art, which are prone to thermal deformation at high temperatures, resulting in distortion of sound wave transmission, and lack of optimization design for specific frequency bands of the drain valve. The shape, material and size parameters of the waveguide rod are determined, and the waveguide rod is subjected to thermal simulation to determine the minimum rod length of the waveguide rod. The energy distribution characteristics of the waveguide rod are analyzed to analyze the energy distribution characteristics of the waveguide rod in the frequency band of the drain valve. The waveguide rod designed by the design method of the present application can provide a temperature buffer medium between the power plant drain valve and the acoustic sensor, solving the problem that the surface temperature of the power plant drain valve is too high to directly use a normal temperature acoustic sensor to collect signals. At the same time, the sound intensity loss caused by the waveguide rod during the transmission of the sound wave signal is very small, and it will not affect the collected sound signal, which is a reliable waveguide tool.

[0005] In the power plant drain valve sound monitoring, when there is a temperature incompatibility problem between the acoustic sensor and the drain valve (the working temperature of the drain valve can reach 400℃, and the working environment of the acoustic sensor is at most 100℃), using a waveguide probe as a transition structure is a solution.

[0006] The primary function of a waveguide is thermal isolation. By using materials with low thermal conductivity (such as ceramics and stainless steel) to isolate high-temperature areas, it protects the acoustic sensor that acquires signals from thermal damage. The secondary function of a waveguide is signal transmission. A key issue in this process is addressing signal attenuation and distortion, and reducing acoustic energy loss caused by long-distance waveguide travel.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A waveguide rod design method for assisting in the acquisition of sound signals from power plant steam traps, wherein one end of the waveguide rod is connected to the power plant steam trap, and the other end is connected to a sound wave sensor, transmitting the sound signal from the power plant steam trap to the sound wave sensor for acquisition, while simultaneously isolating the sound wave sensor from high-temperature areas. The waveguide rod design method includes the following steps: I. Determine the parameters of the waveguide rod S1. Determine the shape, material, and dimensional parameters of the waveguide rod; Preferably, in step S1, the waveguide rod is cylindrical in shape, and the contact end between the waveguide rod and the drain valve is a truncated cone.

[0008] Preferably, in step S1, the waveguide rod is made of SS316L stainless steel.

[0009] Preferably, in step S1, the waveguide rod has the following dimensions: a bottom radius of 5mm, a top radius of 10mm, and a height of 8mm for the truncated cone portion.

[0010] II. Thermal Simulation of Waveguide Rods S2. Perform thermal simulation on the waveguide rod with determined shape, material and size parameters to obtain the axial temperature response curve of the waveguide rod, and determine the minimum rod length of the waveguide rod based on the axial temperature response curve of the waveguide rod and the ambient temperature of the acoustic sensor. Preferably, in step S2, the thermal simulation includes: setting the steam trap as... A constant-temperature heat source; the steam trap is simplified to a volumetric block measuring 50mm in length, 50mm in width, and 10mm in height; the ambient temperature around the waveguide rod... At 25°C and an ambient pressure of 1 atm, the waveguide rod undergoes natural convection heat transfer with the environment.

[0011] Preferably, in the thermal simulation of step S2, the waveguide rod temperature distribution equation is:

[0012] in, In the direction of waveguide rod length The temperature at that location The heat transfer coefficient of the waveguide rod is... Let be the heat transfer coefficient between the waveguide rod and the air. The cross-sectional area of ​​the waveguide rod is... Let be the perimeter of the waveguide rod's cross-section. The ambient temperature around the waveguide rod.

[0013] Preferably, in step S2, the thermal simulation includes: adding boundary conditions. The waveguide rod is in contact with a constant-temperature heat source at this point, and the temperature of the waveguide rod at this point is equal to the temperature of the constant-temperature heat source. The waveguide rod undergoes natural convection heat transfer with the surrounding air, yielding a temperature distribution expression along the length of the waveguide rod. This distribution expression is then used to obtain the axial temperature response curve of the waveguide rod. From the axial temperature response curve of the waveguide rod, the waveguide rod length corresponding to the ambient temperature of the acoustic sensor is found and taken as the minimum length of the waveguide rod.

[0014] Preferably, in step S2, the temperature distribution expression of the waveguide rod along its length is:

[0015]

[0016]

[0017] in, In the direction of waveguide rod length Temperature at that location; The ambient temperature around the waveguide rod; The temperature of the constant-temperature heat source; The heat transfer coefficient between the waveguide rod and the air; It is a constant; The length of the waveguide rod; This refers to a specific position along the length of the waveguide rod. The perimeter of the waveguide rod's cross-section; The heat transfer coefficient of the waveguide rod; The cross-sectional area of ​​the waveguide rod; The radius of the waveguide rod cross section; In the direction of waveguide rod length Temperature at that location; It is a hyperbolic cosine function.

[0018] III. Energy Distribution Characteristics of Waveguide Rods S3. Perform energy distribution characteristic analysis on the waveguide rod that meets the minimum rod length, analyze the energy distribution characteristics of the waveguide rod in the acoustic frequency band of the steam trap, obtain the acoustic energy loss of the sound signal during the transmission process of the sound signal in the waveguide rod, and determine whether the waveguide rod meets the design requirements based on the acoustic energy loss.

[0019] Preferably, the S3 step comprises: performing acoustic simulation on the waveguide rod, using the pressure acoustic module of the acoustic part of COMSOL Multiphysics, and using a hard sound field boundary for the air contact surface of the waveguide rod to simulate sound rigid reflection; using an acoustic equation to describe the propagation characteristics of sound waves in the waveguide rod, and analyzing in combination with the elastic wave theory in a solid.

[0020] Preferably, the S3 step comprises: setting the axial displacement of the waveguide rod as , the strain , the stress , and the waveguide rod motion equation as:

[0021] wherein, is the axial displacement of the waveguide rod; is time; is the longitudinal wave speed in the waveguide rod; is a position in the length direction of the waveguide rod; is the Young's modulus of the waveguide rod; is the density of the waveguide rod.

[0022] Preferably, the S3 step comprises: the sound pressure in the waveguide rod is related to the displacement gradient, and comprises:

[0023] wherein, is the sound pressure in the waveguide rod; is the Young's modulus of the waveguide rod; is the axial displacement of the waveguide rod; is a position in the length direction of the waveguide rod.

[0024] Preferably, the S3 step comprises: setting the solving step length based on the sound signal generated by the operation of the hydrophobic valve, obtaining sound pressure level visualization under different frequencies, and converting the sound pressure amplitude into an energy level through a logarithmic form to describe the energy strength of the sound wave propagation in the medium.

[0025] Preferably, in the S2 step, the working environment temperature of the sound wave sensor is ≤100℃; and in the S3 step, the sound frequency band of the hydrophobic valve is 100Hz-15kHz.

[0026] The beneficial effects of the present application are: 1. The application is a waveguide rod design for assisting power plant drain valve sound signal collection. This waveguide rod can provide a temperature buffer medium between the power plant drain valve and the acoustic sensor, solving the problem of high surface temperature of the power plant drain valve that cannot directly use normal temperature sensors to collect signals. At the same time, the waveguide rod causes little loss of sound intensity during the transmission of sound signals, and has little effect on the collected sound signals, making it a reliable waveguide tool.

[0027] 2. In terms of shape, this waveguide rod uses a conical frustum at the incident end to reduce the contact area between the waveguide rod and the drain valve, reducing the heat entering the waveguide rod, which helps to shorten the length of the waveguide rod and further reduce the loss of sound energy.

[0028] 3. In terms of use, this is a waveguide rod for assisting power plant drain valve sound signal collection, and the transmitted sound waves are of uncertain frequency and uncertain time, so the waveguide rod can transmit a wider frequency band of sound signals.

[0029] 4. The waveguide rod end is equipped with an acoustic sensor to collect sound signals, which can be combined with machine learning algorithms to establish a mapping database of sound signals and valve fault types (such as leakage, blockage, and mechanical wear). BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The waveguide rod design method flowchart of the application; Figure 2 The waveguide rod schematic diagram of the application; Figure 3 The conical frustum part of the waveguide rod of the application; Figure 4 The waveguide rod temperature simulation visualization of the application; Figure 5 The waveguide rod temperature changes with the axial direction of the application; Figure 6 The sound pressure level of the application is 100Hz; Figure 7 The sound pressure level of the application is 1kHz; Figure 8 The sound pressure level of the application is 8kHz; Figure 9 The sound pressure level of the application is 15kHz; Figure 10 The 15kHz sound pressure level incident end local of the application. DETAILED DESCRIPTION

[0031] The concept, specific structure and technical effects of the application will be described clearly and completely in the following embodiments and drawings, so as to fully understand the purpose, features and effects of the application.

[0032] Embodiment 1 A waveguide rod design method for assisting power plant drain valve sound signal collection, one end of the waveguide rod is connected to the power plant drain valve, the other end is connected to the acoustic wave sensor, and the sound signal of the power plant drain valve is transmitted to the acoustic wave sensor for collection, while isolating the high temperature area to protect the acoustic wave sensor, as shown in Figure 1 The design method of the waveguide rod comprises the following steps: S1, determining the shape, material and size parameters of the waveguide rod; S2, thermal simulation is performed on the waveguide rod with the determined shape, material and size parameters, an axial temperature response curve of the waveguide rod is obtained, and the minimum rod length of the waveguide rod is determined based on the axial temperature response curve of the waveguide rod and the working environment temperature of the acoustic wave sensor; S3, energy distribution characteristic analysis is performed on the waveguide rod satisfying the minimum rod length, the energy distribution characteristic of the waveguide rod in the sound frequency band of the drain valve is analyzed, the acoustic energy loss of the sound signal in the transmission process of the waveguide rod is obtained, and whether the waveguide rod meets the design requirements is judged based on the acoustic energy loss.

[0033] Embodiment 2 This embodiment is further described on the basis of the above-mentioned embodiment, and S1 step is further described as follows: For the study of sound waveguide rod, the cooling effect and acoustic energy attenuation should be studied from three aspects of waveguide rod shape, material and size. Considering the stability of installation and the efficiency of sound transmission, a cylindrical waveguide rod is selected. Considering the heat dissipation effect, a conical frustum is selected at the contact end of the drain valve to reduce the contact area with the drain valve and reduce the heat flux flowing through the waveguide rod, and the specific shape is as shown in Figure 2 The material selected is SS316L stainless steel, and its main parameters are shown in Table 1. The specific size of the waveguide rod can be customized according to the working requirements, and the following size is taken as an example for subsequent research. The bottom radius of the conical frustum part is 5mm, the top radius is 10mm, and the frustum height is 8mm, as shown in Figure 3 .

[0034] Table 1 Material parameters and bulk wave velocity of SS316L stainless steel

[0035] Embodiment 3 This embodiment is further described on the basis of the above-mentioned embodiment, and S2 step is further described as follows: The heat dissipation analysis is performed on the waveguide rod shown in Figure 2 The conical frustum end of the waveguide rod is in contact with the surface of the drain valve, and the drain valve is set as The constant-temperature heat source is simplified in shape to a volumetric block with a length of 50mm, a width of 50mm, and a height of 10mm. Ambient temperature. At 25℃ and an ambient pressure of 1 atm, the waveguide rod undergoes natural convection heat transfer with the environment. Its temperature distribution equation is:

[0036] in, In the direction of waveguide rod length The temperature at that location The heat transfer coefficient of the waveguide rod is... Let be the heat transfer coefficient between the waveguide rod and the air. The cross-sectional area of ​​the waveguide rod is... Let be the perimeter of the waveguide rod's cross-section. The ambient temperature around the waveguide rod.

[0037] Add boundary conditions. The waveguide rod is in contact with a constant-temperature heat source, so the two temperatures are equal at this point. The waveguide rod undergoes natural convection heat transfer with the surrounding air, and the expression for the temperature distribution of the waveguide rod along its length can be obtained:

[0038]

[0039]

[0040] in, In the direction of waveguide rod length Temperature at that location; The ambient temperature around the waveguide rod; The temperature of the constant-temperature heat source; The heat transfer coefficient between the waveguide rod and the air; It is a constant; The length of the waveguide rod; This refers to a position along the length of the waveguide rod; The perimeter of the waveguide rod's cross-section; The heat transfer coefficient of the waveguide rod; The cross-sectional area of ​​the waveguide rod; The radius of the waveguide rod cross section; In the direction of waveguide rod length Temperature at that location; It is a hyperbolic cosine function.

[0041] Temperature simulation visualization, such as Figure 4 As shown.

[0042] Under these simulation conditions, the axial temperature response of the waveguide rod is obtained as follows:Figure 5 It can be seen that when the temperature in the rod drops to 100°C, the rod length needs to be at least 270 mm. Figure 5

[0043] Example 4 This embodiment is based on the above-mentioned embodiments, and further describes the S3 step, which is the energy distribution characteristic analysis of the waveguide rod, as follows: The acoustic simulation of the waveguide rod with a length of 300 mm was performed using the pressure acoustic module of the COMSOL Multiphysics acoustic part, and the hard sound field boundary was used for the contact surface between the rod and the air to simulate the rigid reflection of sound. The acoustic equation was used to describe the propagation characteristics of sound waves in the rod, and the elastic wave theory in solids was used for analysis.

[0044] Let the axial displacement of the waveguide rod be , the strain , and the stress (E is the Young's modulus). The motion equation can be simplified as:

[0045] wherein, is the axial displacement of the waveguide rod; is the time; is the longitudinal wave speed in the waveguide rod; is a certain position in the length direction of the waveguide rod; is the Young's modulus of the waveguide rod; is the density of the waveguide rod.

[0046] The axial displacement of the waveguide rod is the mechanical vibration displacement of the material particles of the waveguide rod along the axial direction (z direction) of the rod, which is caused by the propagation of sound waves in solids.

[0047] The sound pressure in the waveguide rod is related to the displacement gradient:

[0048] wherein, is the sound pressure in the waveguide rod; is the Young's modulus of the waveguide rod; is the axial displacement of the waveguide rod; is a certain position in the length direction of the waveguide rod.

[0049] ​The sound signal generated by the hydrophobic valve is a low-frequency signal, so the solving step is set to range (100, 100, 15000) Hz, and the sound pressure level visualization at different frequencies is obtained. The sound pressure level is converted from the sound pressure amplitude to the energy level in logarithmic form (decibel, dB), which describes the energy strength of the sound wave in the medium during propagation. The following shows the waveguide rod sound pressure level visualization for several characteristic frequencies, which are 100Hz ( Figure 6 ), 1kHz ( Figure 7 ), 8kHz ( Figure 8 ), and 15kHz ( Figure 9 ).

[0050] Overall, the frequency ranges from 100Hz to 15kHz, and the sound signal has a very small sound pressure change in the waveguide rod, which meets the design requirements. At the selected frequencies, the sound signal is constant at 83.010dB from the incident end to the exit end at 100Hz, the sound pressure level decreases from 83.012dB at the incident end to 83.010dB at the exit end at 1kHz, the sound pressure level decreases from 83.106dB at the incident end to 83.011dB at the exit end at 8kHz, and the sound pressure level decreases from 83.337dB at the incident end to 83.013dB at the exit end at 15kHz. Moreover, in the entire frequency band, the sound pressure level in the rod almost does not attenuate, and when the frequency reaches 8kHz, a part of the sound energy near the incident surface is lost, resulting in a significant attenuation of the sound pressure level near the incident surface, which can be referred to Figure 10 .

[0051] The above describes the embodiments of the present application, but the present application is not limited to the above-mentioned embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A waveguide pole design method for assisting power plant drain valve sound signal acquisition, characterized by, One end of the waveguide rod is connected with the power plant drain valve, and the other end is connected with the sound wave sensor, the sound signal of the power plant drain valve is transmitted to the sound wave sensor for collection, and the high temperature area is isolated to protect the sound wave sensor, the design method of the waveguide rod comprises the following steps: S1, determine the shape, material and size parameters of the waveguide rod; S2, heat simulation is carried out on the waveguide rod with determined shape, material and size parameters, the axial temperature response curve of the waveguide rod is obtained, and the minimum rod length of the waveguide rod is determined based on the axial temperature response curve of the waveguide rod and the working environment temperature of the sound wave sensor; S3, energy distribution characteristic analysis is carried out on the waveguide rod meeting the minimum rod length, the energy distribution characteristic of the waveguide rod in the sound frequency band of the drain valve is analyzed, the sound wave energy loss of the sound signal in the transmission process of the waveguide rod is obtained, and whether the waveguide rod meets the design requirements is judged based on the sound wave energy loss.

2. A waveguide pole design method for assisting power plant drain valve sound signal acquisition according to claim 1, characterized in that, In S1, the shape of the waveguide rod is cylindrical, and the contact end of the waveguide rod with the drain valve is a conical frustum.

3. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as claimed in claim 2, characterized in that, In S1, the material of the waveguide rod is SS316L stainless steel; the size of the waveguide rod is that the bottom radius of the conical frustum part is 5mm, the top radius is 10mm, and the frustum height is 8mm.

4. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as claimed in claim 1, characterized by, In the S2 step, the thermal simulation comprises: setting the hydrophobic valve as The constant temperature heat source, the hydrophobic valve is simplified as a volume block with a length of 50 mm, a width of 50 mm, and a height of 10 mm; the ambient temperature around the waveguide rod is 25℃, the ambient pressure is 1atm, and the waveguide rod and the ambient environment exchange heat by natural convection. The constant temperature heat source, the hydrophobic valve is simplified as a volume block with a length of 50 mm, a width of 50 mm, and a height of 10 mm; the ambient temperature around the waveguide rod is 25℃, the ambient pressure is 1atm, and the waveguide rod and the ambient environment exchange heat by natural convection.

5. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as claimed in claim 1, characterized in that, In the heat simulation of S2, the temperature distribution equation of the waveguide rod is: wherein, T is the temperature at the waveguide rod length direction T is the temperature at the waveguide rod length direction K is the waveguide rod heat transfer coefficient, K is the waveguide rod heat transfer coefficient, A is the waveguide rod cross-sectional area, P is the waveguide rod cross-sectional perimeter, T is the waveguide rod ambient temperature.

6. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as claimed in claim 1, characterized by, In the S2 step, the thermal simulation comprises: adding a boundary condition, At the position where the waveguide rod is in contact with the constant temperature heat source, the temperature of the waveguide rod is equal to the temperature of the constant temperature heat source; At the position where the waveguide rod is in natural convection heat exchange with the surrounding air, a distribution expression of the temperature of the waveguide rod along the length direction is obtained, and an axial temperature response curve of the waveguide rod is obtained by using the distribution expression; in the axial temperature response curve of the waveguide rod, the waveguide rod length corresponding to the working environment temperature of the acoustic wave sensor is found as the minimum length of the waveguide rod.

7. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as claimed in claim 6, characterized by, In S2, the distribution expression of the waveguide rod temperature along the length direction is: wherein, is the temperature at the waveguide rod length direction ; is the ambient temperature of the waveguide rod; is the constant temperature heat source temperature; is the heat transfer coefficient of the waveguide rod and air; is a constant; is the length of the waveguide rod; is a position in the waveguide rod length direction; is the waveguide rod cross-sectional perimeter; is the waveguide rod heat transfer coefficient; is the waveguide rod cross-sectional area; is the waveguide rod cross-sectional radius; is the temperature at the waveguide rod length direction ; is the hyperbolic cosine function.

8. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as defined in claim 1, wherein, S3 includes: acoustic simulation of the waveguide rod, using the pressure acoustic module of the acoustic part of COMSOL Multiphysics, the waveguide rod and the air contact surface adopt hard sound field boundary, and the sound rigid reflection is simulated; the propagation characteristics of sound wave in the waveguide rod are described by using acoustic equation, and the analysis is carried out in combination with the elastic wave theory in solid.

9. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as defined in claim 1, wherein, S3 step includes: set axial displacement as , strain , stress , waveguide rod motion equation is: wherein, is the axial displacement of the waveguide rod; is time; is the longitudinal wave speed in the waveguide rod; is a position along the length of the waveguide rod; is the Young's modulus of the waveguide rod; is the density of the waveguide rod; The S3 step comprises: sound pressure in the waveguide rod Related to the displacement gradient, comprising: wherein is the sound pressure in the waveguide rod; is the Young's modulus of the waveguide rod; is the axial displacement of the waveguide rod; is a position in the length direction of the waveguide rod.

10. A waveguide pole design method for assisting power plant drain valve sound signal acquisition as defined in claim 1, wherein, S3 includes: setting the solution step length based on the sound signal generated by the drain valve working is a low frequency signal, obtaining the sound pressure level visualization under different frequencies, the sound pressure level is converted into energy level by logarithmic form, and the energy strength of sound wave in medium is described when the sound wave propagates.

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