Nuclear main pump double-cone sealing leakage detection method based on bolt load and sealing contact model

Abstract

A nuclear main pump double-cone sealing leakage detection method based on a bolt load and a sealing contact model relates to the technical field of double-cone sealing leakage detection.The method comprises the steps that firstly, the bolt load is substituted into a mapping model of the bolt load and gasket sealing surface contact pressure, and the sealing surface contact pressure is obtained; dividing calculation units for the sealing contact surface, and completing the construction of a gasket sealing rough contact surface model of a single calculation unit; a finite element simulation method is used for obtaining a sealing contact surface entity after compression deformation; the deformed sealing contact surface entity is subjected to micro fluid leakage calculation in Fluent fluid simulation software, and the leakage rate of a single calculation unit is obtained; finally, the leakage rate of the whole double-cone sealing structure is obtained according to division of the calculation units. By acquiring the king bolt load and the sealing contact model, tiny leakage detection of the double-cone sealing structure is achieved, and the method has the advantages of being high in accuracy, simple in test, high in environmental adaptability and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of double-cone seal leakage detection, and in particular to a double-cone seal leakage detection method for a nuclear main pump based on bolt load and seal contact model. Background Art

[0002] The double cone seal is a semi-self-tightening sealing structure with radial self-tightening effect. It has a simple structure and is easy to install and disassemble. It is suitable for occasions with pressure and temperature fluctuations. It is a high-pressure sealing structure commonly used in nuclear equipment, process industry equipment and pressure vessels.

[0003] The double-cone seal structure is a crucial component of the pressure boundary of a shielded main pump (also known as a "nuclear main pump"). It connects the main pump motor and hydraulic components, ensuring the integrity of the pressure boundary and preventing coolant leakage. However, because nuclear main pumps are often subjected to alternating loads such as high temperatures (250°C to 300°C) and high pressures (~15 MPa), the double-cone seal is susceptible to interfacial leakage failure due to gaps between the gasket and the flange sealing surface, causing harm to industrial production and economic losses. Therefore, accurately monitoring and obtaining information on the leakage rate of the sealing surface is key to predicting double-cone seal failure in main pumps.

[0004] Currently, most existing leak detection methods focus on acoustic emission, noise signals, image signals, and vibration signals. Considering the characteristics of the nuclear main pump double-cone seal structure with small leakage, complex working environment, and high background noise, the leak detection method based on acoustic emission, such as the patent application entitled "A method for online detection of metal pressure vessel leakage based on acoustic emission signals" (publication number CN110044554A), has poor experimental results and low detection efficiency during the experimental simulation acquisition process. The leak detection method based on image signals, such as the patent application entitled "A method for detecting small leak targets of seals based on low-resolution infrared images" (publication number CN115994893B), has poor image signal quality. Since shielded main pumps usually operate in a strong radiation environment, which is not only harmful to the human body but also causes interference or damage to the image acquisition equipment, resulting in a decrease in image signal quality, which in turn affects the accuracy and reliability of leak detection. Therefore, the existing detection methods are difficult to apply to the micro-leak detection of the double-cone seal structure. Therefore, it is necessary to explore a new and highly accurate leak detection method to achieve 1.0×10 -4 ~1.0×10 -6 Small leaks at the g / s level can be detected to evaluate the operating status of the main pump. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for detecting leakage of nuclear main pump double cone seals based on bolt load and seal contact model, which can realize the 1.0×10-4 ~1.0×10 -6 Micro-leakage monitoring at the g / s level.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A nuclear main pump double-cone seal leakage detection method based on bolt load and seal contact model is proposed. The bolt working load is obtained through the mapping relationship between bolt load and sealing surface contact pressure, and the leakage rate calculation model of the measured double-cone seal contact surface morphology is combined to obtain the leakage rate data of the main pump double-cone seal.

[0008] A nuclear main pump double-cone seal leakage detection method based on bolt load and seal contact model includes the following steps:

[0009] Step 1: Place a gasket-type pressure sensor between the main bolt and flange of the double-cone seal structure to obtain the bolt working load W2;

[0010] Step 2: Substitute the bolt working load W2 measured in step 1 into the mapping model of bolt load and sealing surface contact pressure to obtain the contact pressure P of the double-cone sealing gasket surface. F ;

[0011] Step 3: Process the annular contact area of the double-cone seal and divide it into N calculation units of equal size. Then, obtain a sealing gasket sample and establish a leakage rate calculation model based on the measured double-cone seal contact surface morphology of a single calculation unit of the sealing gasket sample.

[0012] Step 4: Import the leakage rate calculation model of the measured double-cone seal contact surface morphology of a single calculation unit obtained in step 3 into the static structure module of Ansys for contact simulation to obtain the measured rough surface contact model after contact simulation calculation; export the measured rough surface contact model in Ansys through an Stl file, and reconstruct the model in the modeling software to obtain the sealing contact surface solid model after compression deformation;

[0013] Step 5: Import the solid model of the sealing contact surface under compression deformation obtained in step 4 into the Fluent fluid finite element software, set the working parameters of the medium pressure and ambient temperature, and perform microfluid leakage simulation in the fluid domain to obtain the mass flow rate Q0 of the microfluid domain model at the pressure outlet;

[0014] Step 6: Based on the N calculation units divided in step 3, the leakage rate Q of the entire double-cone sealing structure is calculated using the leakage rate formula Q=4NQ0 of the fluid domain of a single calculation unit.

[0015] The mapping model of bolt load and sealing surface contact pressure in step 2 is:

[0016]

[0017] Where D G is the average sealing diameter of the double cone ring:

[0018]

[0019] b is the width of the gasket:

[0020]

[0021] Where W2 is the working load of the bolt; p c is the medium pressure in the sealing chamber; ρ is the friction angle of the sealing surface; α is the cone angle of the double-cone ring; A is the height of the double-cone ring, in mm; B is the thickness of the double-cone ring, in mm; C is the height of the outer surface of the double-cone ring, in mm; n is the number of bolts.

[0022] The method for establishing the leakage rate calculation model of the measured double-cone seal contact surface morphology in step 3 is as follows:

[0023] 3.1) First, partially cut the double-cone sealing gasket to obtain a sealing gasket sample;

[0024] 3.2) According to the following formula, the annular contact area of the double cone seal is divided into N calculation units of equal size. A single calculation unit is a rectangular area of l×h. If the contact pressure, surface morphology, and medium pressure load parameters of each calculation unit are the same, then the calculated leakage rate is also the same. The leakage rate of the N calculation units is used to replace the leakage rate of the entire contact area.

[0025]

[0026] Among them, R c is the average diameter of the double cone ring; h is the length of the calculation unit;

[0027] 3.3) Using a laser confocal roughness measurement system, randomly select m rectangular areas of the sealing gasket sample for rough surface morphology scanning, and then splice the m areas into a single calculation unit to obtain the surface morphology parameters of the single calculation unit; the surface morphology parameters of the single calculation unit after scanning are converted into a rectangular digital rough surface, and then the rectangular digital rough surface is converted into a height matrix H m (x,y,z);

[0028] 3.4) The height matrix H is interpolated in MATLAB software using the surface spline interpolation algorithm based on Green's function. m (x, y, z) is used for surface fitting to obtain the fitted height matrix H n (x,y,z) digital surface topography;

[0029] 3.5) The height matrix H is fitted by a finite triangle patch data fitting algorithm. n The digital surface topography drawn by (x, y, z) is used to fit the three-dimensional topography data and complete the construction of the three-dimensional model of the rough contact surface topography of the gasket of a single computing unit.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This method uses a mapping model between bolt load and sealing surface contact pressure to obtain sealing surface contact pressure, reducing the difficulty of detecting gasket sealing surface contact pressure. Furthermore, through scanning, 3D model construction, compression deformation processing, and fluid domain simulation of the double-cone sealing gasket, the leakage rate of the gasket sealing contact surface is measured. Compared with the low detection efficiency and unclear results of acoustic emission and image signal methods, this method has a smaller overall error range, reaching 1.0×10 -4 ~1.0×10 -6 The leakage detection requirement is small, which is on the order of g / s. Therefore, this leakage detection method can achieve the leakage detection of the nuclear safety level required by the main pump, and has the advantages of strong environmental adaptability, high measurement accuracy, and reliable results. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Flowchart of a method according to an embodiment of the present invention.

[0033] Figure 2 Schematic diagram of the installation position of the double-cone sealing structure gasket pressure sensor according to an embodiment of the present invention.

[0034] Figure 3 Schematic diagram of the processing of the annular contact area of the double-cone sealing structure according to an embodiment of the present invention.

[0035] Figure 4 This is a two-dimensional surface topography diagram of a partial scan area in the annular contact area of the double-cone sealing structure according to an embodiment of the present invention.

[0036] Figure 5 This is a digital rough surface topography image of a single computing unit in the contact area of the double-cone sealing structure according to an embodiment of the present invention.

[0037] Figure 6 This is a flow chart of the modeling of the leakage rate calculation model for the measured double-cone seal contact surface morphology according to an embodiment of the present invention.

[0038] Figure 7 This is a microscopic contact model diagram of the measured rough contact surface morphology of a single computing unit in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0040] Example: Figure 1 As shown, a nuclear main pump double-cone seal leakage detection method based on bolt load and seal contact model includes the following steps:

[0041] Step 1: Place a gasket-type pressure sensor between the main bolt and flange of the double-cone seal structure. The installation position of the gasket-type pressure sensor is as follows: Figure 2 As shown, the double-cone sealing structure consists of a double-cone ring structure 1, a pump casing flange 2 of the main pump, a cylinder 3, a sealing gasket 4 between the double-cone ring and the flange and cylinder, a nut 5, a main bolt 6, and a high-strength gasket 8. A washer-type pressure sensor 7 is connected to the main bolt 6 and is located between the pump casing flange 2 and the nut 5 of the main pump. The signal received by the washer-type pressure sensor 7 is amplified by a signal amplifier, then collected by a data acquisition device and transmitted to a host computer to obtain the main bolt working load W2.

[0042] The bolt working load W2 measured in this embodiment is 65.35KN;

[0043] Step 2: Substitute the bolt working load W2 measured in step 1 into the mapping model of bolt load and sealing surface contact pressure to obtain the contact pressure P of the double-cone sealing gasket surface. F ;

[0044] The mapping model of bolt load and sealing surface contact pressure is as follows:

[0045]

[0046] Where D G is the average sealing diameter of the double cone ring:

[0047]

[0048] b is the width of the gasket:

[0049]

[0050] Where W2 is the working load of the bolt; p c is the medium pressure of the sealing chamber, D1 is the inner diameter of the double-cone ring, in mm; ρ is the friction angle of the sealing surface; α is the cone angle of the double-cone ring; A is the height of the double-cone ring, in mm; B is the thickness of the double-cone ring, in mm; C is the height of the outer surface of the double-cone ring, in mm; n is the number of bolts;

[0051] In this embodiment, W2=65.35KN, p c=3Mpa, ρ=10°, α=30°, D1=400mm, A=54mm, B=13mm, C=27mm, n=8, so the final calculated average seal diameter D G =418.21mm, contact pressure P F =2.38Mpa;

[0052] Step 3: Given the difficulty in modeling the microscopic contact and fluid leakage of the entire double-cone seal structure, the annular contact area of the double-cone seal is processed and divided into N calculation units of equal size. Then, a sealing gasket sample is obtained, and a leakage rate calculation model is established based on the measured double-cone seal contact surface morphology of a single calculation unit of the sealing gasket sample.

[0053] In this embodiment, the gasket is a copper gasket. A leakage rate calculation model is established based on the measured double-cone seal contact surface morphology of a single calculation unit of the copper gasket sample. The specific method is as follows:

[0054] 3.1) To obtain three-dimensional topographic data reflecting the actual rough surface topography, firstly, a double-cone sealing copper gasket is partially cut to obtain a copper gasket sample;

[0055] 3.2) According to the following formula, the annular contact area of the double cone seal is processed into N calculation units of the same size. The division area is shown as follows: Figure 3 As shown in the figure, a single calculation unit is a rectangular area of l×h. If the load parameters such as contact pressure, surface morphology, and medium pressure of each calculation unit are the same, then the calculated leakage rate is also the same. The leakage rate of the double-cone seal structure uses the leakage rate of N calculation units instead of the leakage rate of the entire contact area.

[0056]

[0057] Among them, R c is the average diameter of the double cone ring; h is the length of the calculation unit;

[0058] The annular contact area of the double-cone sealing structure in this embodiment has a circumference of 1281.8 mm and an area of 20804.6 mm. 2 , radial contact width is 16.1mm; R c = 203.987 mm, h is the length of the minimum scanning area, that is, h = 2.5 mm, so N = 513;

[0059] 3.3) Using the Lecia DCM8 laser confocal roughness measurement system, m rectangular areas of the sealing gasket sample were scanned for rough surface morphology. Then, the surface morphology of the m blocks of the scanned area is spliced into a single calculation unit to obtain the surface morphology parameters of the single calculation unit; the surface morphology parameters of the single calculation unit after scanning are converted into a rectangular digital rough surface, and then the rectangular digital rough surface is converted into a height matrix H m (x,y,z), for surface fitting;

[0060] In this embodiment, the area S of the sample scanning area of the measurement system is measured. 矩形区域 =2.5×3mm, the area of a single computing unit is S 单个计算单元 =2.5×16.1mm, so m is 5, and the results of partial area scanning are as follows Figure 4 As shown, it can be seen that the overall surface morphology profile height of area 1 is between 0-25μm, and the maximum profile height is 24.864μm. After calculation, the surface arithmetic average height Sa of this area is 2.1835μm; the overall surface morphology profile height of area 2 is between 0-32μm, and the maximum profile height is 31.431μm. After calculation, the surface arithmetic average height Sa of this area is 3.1019μm; the overall surface morphology profile height of area 3 is between 0-31μm, and the maximum profile height is 30.096μm. After calculation, the surface arithmetic average height Sa of this area is 4.1454μm. The scanning results of the three areas show that when the sample surface roughness is Ra = 3.2μm, the surface topography and the arithmetic mean deviation of the profile obtained by scanning the local surface topography have certain fluctuations. Therefore, in the subsequent 3D topography reconstruction, the 3D topography of the scanned area needs to be considered. The ideal result is to scan and reconstruct the 3D topography of the entire sample. However, considering the limitation of the scanning area of the measurement system, m randomly selected areas are spliced to reduce the impact of the fluctuation of the surface topography and the surface arithmetic mean height deviation results.

[0061] 3.4) The height matrix H is interpolated in MATLAB software using the surface spline interpolation algorithm based on Green's function. m (x, y, z) is used for surface fitting to obtain the fitted height matrix H n (x, y, z) digital surface morphology drawn, so the digital surface morphology of the double cone sealing gasket scanning area after fitting processing is as shown in the attached figure. Figure 5 As shown;

[0062] 3.5) The height matrix H is fitted by a finite triangle patch data fitting algorithm. n The digital surface topography drawn by (x, y, z) is used to perform three-dimensional topography data fitting to complete the construction of a three-dimensional model of the rough contact surface topography of the gasket of a single calculation unit;

[0063] The 3D shape data fitting process is as follows: 3.5.1) Generate a triangular patch with vertices a, b, and c to obtain a 1×3 triangular patch matrix; 3.5.2) Combine the two triangular faces into a quadrilateral, and use the lower left corner of the quadrilateral as the sampling point of the surface; 3.5.3) Use the height matrix H after surface fitting n (x,y,z), generate a surface stl model with XY as the network and Z as the corresponding height;

[0064] In summary, the actual rough surface morphology of the sealing gasket of a single calculation unit is modeled in three dimensions. The modeling process is as follows: Figure 6 As shown, the above operations can complete the reconstruction modeling of the actual rough surface morphology;

[0065] Step 4: The leakage rate calculation model of the measured double-cone seal contact surface morphology of a single calculation unit obtained in step 3 is transferred to HyperMesh for solid tetrahedron meshing, and then imported into the static structure module of Ansys for contact simulation with the simplified rectangular solid plane of the pump casing flange, as shown in the figure. Figure 7 As shown, the pump casing flange entity is on top and the sealing gasket entity is on the bottom. A fixed support constraint is added to the bottom surface of the sealing gasket entity, and a uniformly distributed pressure load is added to the upper side of the pump casing flange entity. Its magnitude is equal to the contact pressure measured in step 2 to simulate the contact between the sealing gasket and the pump casing flange entity. At the same time, frictionless supports are added to the eight side surfaces of the pump casing flange entity and the sealing gasket entity, and their displacement is limited to the normal direction of the contact surface, thereby obtaining the measured rough surface contact model after contact simulation calculation. The model is then reconstructed through the Stl file to obtain the sealing contact surface entity model after compression deformation;

[0066] Step 5: Import the solid model of the sealing contact surface under compression deformation obtained in step 4 into the Fluent fluid finite element software, and use the fluid numerical simulation, i.e., the fluid dynamics (CFD) method, to simulate the leakage of the constructed microscopic fluid domain model;

[0067] Set the following conditions: the surface connecting to the inner side of the pump chamber is set as the pressure inlet, the medium pressure is set as the inlet pressure, the surface connecting to the outside atmosphere is set as the pressure outlet, the pressure is equal to atmospheric pressure, and the ambient temperature and other operating parameters are set. In this embodiment, the medium pressure P = 3 MPa and the ambient temperature T = 20°C. Perform a microfluid leakage simulation in the fluid domain to obtain the mass flow rate Q0 at the pressure outlet of the microfluid domain model.

[0068] The mass flow rate calculated in this embodiment is Q0=1.73×10 -7 g / s;

[0069] Step 6: Based on the N calculation units divided in step 3, the leakage rate Q of the entire double-cone seal structure is calculated using the leakage rate formula of the fluid domain of a single calculation unit Q = 4NQ0;

[0070] The final calculated leakage rate in this embodiment is Q = 4NQ0 = 3.55 × 10 -4 g / s, and the leakage rate Q under the same working conditions was measured experimentally. 实 =4.67×10 -4 g / s, the relative error is 24%; in the other tests, the overall error range is between 15% and 40%, with an average error of 23%. -4 ~1.0×10 -6 In terms of the leakage level of g / s, the error is within the acceptable range.

[0071] In summary, the leakage detection method of nuclear main pump double cone seal based on bolt load and seal contact model can achieve the double cone seal leakage detection of main pump within 1.0×10 -4 ~1.0×10 -6 Micro-leak detection at the g / S level has the advantages of simple testing, reliable results, and strong environmental adaptability. It can also evaluate the leakage status of double-cone sealing structures in other industrial equipment.

Claims

1. A nuclear main pump double-cone seal leakage detection method based on bolt load and seal contact model, characterized by: The bolt working load is obtained through the mapping relationship between the bolt load and the sealing surface contact pressure. Combined with the leakage rate calculation model of the measured double-cone seal contact surface morphology, the leakage rate data of the main pump double-cone seal is obtained.

2. A nuclear main pump double-cone seal leakage detection method based on bolt load and seal contact model according to claim 1, characterized in that: The following steps are involved: Step 1: Place a gasket-type pressure sensor between the main bolt and flange of the double-cone seal structure to obtain the bolt working load W2; Step 2: Substitute the bolt working load W2 measured in step 1 into the mapping model of bolt load and sealing surface contact pressure to obtain the contact pressure P of the double-cone sealing gasket surface. F ; Step 3: Process the annular contact area of the double-cone seal and divide it into N calculation units of equal size. Then, obtain a sealing gasket sample and establish a leakage rate calculation model based on the measured double-cone seal contact surface morphology of a single calculation unit of the sealing gasket sample. Step 4: Import the leakage rate calculation model of the measured double-cone seal contact surface morphology of a single calculation unit obtained in step 3 into the static structure module of Ansys for contact simulation to obtain the measured rough surface contact model after contact simulation calculation; export the measured rough surface contact model in Ansys through an Stl file, and reconstruct the model in the modeling software to obtain the sealing contact surface solid model after compression deformation; Step 5: Import the solid model of the sealing contact surface under compression deformation obtained in step 4 into the Fluent fluid finite element software, set the working parameters of the medium pressure and ambient temperature, and perform microfluid leakage simulation in the fluid domain to obtain the mass flow rate Q0 of the microfluid domain model at the pressure outlet; Step 6: Based on the N calculation units divided in step 3, the leakage rate Q of the entire double-cone sealing structure is calculated using the leakage rate formula Q=4NQ0 of the fluid domain of a single calculation unit.

3. The method according to claim 2, wherein: The mapping model of bolt load and sealing surface contact pressure in step 2 is: Where D G is the average sealing diameter of the double cone ring: b is the width of the gasket: Where W2 is the working load of the bolt; p c is the medium pressure in the sealing chamber; ρ is the friction angle of the sealing surface; α is the cone angle of the double-cone ring; A is the height of the double-cone ring, in mm; B is the thickness of the double-cone ring, in mm; C is the height of the outer surface of the double-cone ring, in mm; n is the number of bolts.

4. The method according to claim 2, wherein: The method for establishing the leakage rate calculation model of the measured double-cone seal contact surface morphology in step 3 is as follows: 3.1) First, partially cut the double-cone sealing gasket to obtain a sealing gasket sample; 3.2) According to the following formula, the annular contact area of the double cone seal is divided into N calculation units of equal size. A single calculation unit is a rectangular area of l×h. If the contact pressure, surface morphology, and medium pressure load parameters of each calculation unit are the same, then the calculated leakage rate is also the same. The leakage rate of the N calculation units is used to replace the leakage rate of the entire contact area. Among them, R c is the average diameter of the double cone ring; h is the length of the calculation unit; 3.3) Using a laser confocal roughness measurement system, randomly select m rectangular areas of the sealing gasket sample for rough surface morphology scanning, and then splice the m areas into a single calculation unit to obtain the surface morphology parameters of the single calculation unit; the surface morphology parameters of the single calculation unit after scanning are converted into a rectangular digital rough surface, and then the rectangular digital rough surface is converted into a height matrix H m (x,y,z); 3.4) The height matrix H is interpolated in MATLAB software using the surface spline interpolation algorithm based on Green's function. m (x, y, z) is used for surface fitting to obtain the fitted height matrix H n (x,y,z) digital surface topography; 3.5) The height matrix H is fitted by a finite triangle patch data fitting algorithm. n The digital surface topography drawn by (x, y, z) is used to fit the three-dimensional topography data to complete the construction of the three-dimensional model of the rough contact surface topography of the gasket of a single computing unit.

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