Test method and test device for Taylor-Kutet flow under different working conditions

Abstract

The invention relates to the technical field of fluid tests, in particular to a Taylor-Kutet flow test method and test device under different working conditions. A plurality of monitoring points are arranged on the axial section of an annular flow channel, temperature and speed distribution data are obtained, and the fluid state is judged in combination with Taylor number. For the laminar flow working condition, analyzing the correlation between the viscosity change caused by temperature fluctuation and the flow velocity, constructing a temperature-flow velocity correlation factor, carrying out dynamic correction fusion according to the temperature difference and the flow velocity difference of the monitoring points, and quantifying the flow resistance influence; for a non-laminar flow working condition, a correction weight is calculated based on a ratio of an actual Taylor number to a critical value and a flow velocity fluctuation characteristic. And finally, establishing a mapping model of the motor rotating speed and the correction weight, and forming a feedback adjustment mechanism for adjusting the motor rotating speed in the current test process. The strategy can significantly improve the dynamic adaptability and control precision of working condition simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid testing, and in particular to a test method and a test device for Taylor-Couette flow under different working conditions. Background Art

[0002] When the rotational speed of the inner cylinder increases in the flowing fluid between two cylinders, the complexity of the fluid state will increase significantly. Its complex and changeable flow patterns are collectively referred to as Taylor-Couette flow. As a typical flow form in industrial scenarios such as rotating machinery, chemical reactors, and nuclear energy systems, the research on the flow stability, transition mechanism, and heat transfer characteristics of Taylor-Couette flow is of great significance for engineering optimization.

[0003] Taylor-Couette flow will cause severe temperature fluctuations. Long-term temperature changes will lead to thermal fatigue of materials, and finally cracks may form on the surfaces of the shaft and the shell. At the same time, the existence of Taylor-Couette flow will affect the flow stability of the fluid inside the nuclear main pump. This unstable flow state may cause an increase in the vibration and noise of the pump, affecting its normal operation and performance. Therefore, computer-aided tests on Taylor-Couette flow under different working conditions are required.

[0004] The flow characteristics of Taylor-Couette flow (such as laminar stability, turbulent transition, and vortex structure evolution) are significantly affected by the coupling effects of multiple physical fields such as fluid viscosity, rotation speed ratio, and temperature field; when simulating different actual working conditions, the temperature loss phenomena exhibited by different device structures and different fluids are different, resulting in uneven distribution of fluid viscosity, forming complex flow resistance, and destroying the preset rotational speed-flow velocity model. However, existing test devices and methods often ignore this influencing factor of temperature loss. Therefore, there are certain errors when simulating the parameters corresponding to different working conditions, resulting in deviations in the final working condition simulation. Summary of the Invention

[0005] In order to solve the technical problem that when simulating different actual working conditions, the temperature loss phenomena exhibited by different device structures and different fluids are different, resulting in uneven distribution of fluid viscosity, forming complex flow resistance, and destroying the preset rotational speed-flow velocity model. However, existing test devices and methods often ignore this influencing factor of temperature loss. Therefore, there are certain errors when simulating the parameters corresponding to different working conditions, resulting in deviations in the final working condition simulation, the object of the present invention is to provide a test method and a test device for Taylor-Couette flow under different working conditions, and the specific technical solutions adopted are as follows: A test method for Taylor-Couette flow under different working conditions, comprising: At each motor speed during the historical test process, multiple monitoring positions are set along the radial direction of the outer cylinder on the same axial section of the inner and outer cylindrical annular spaces, and the temperature and flow rate of the fluid at the monitoring positions are obtained within a preset time period. If the Taylor number corresponding to the motor speed is less than or equal to the critical Taylor number; determine the target time. Under each laminar flow, analyze the correlation between the temperature values and flow rate values among the monitoring positions at the target time, and determine the correlation factor; according to the difference in temperature values and the difference in flow rate values among the monitoring positions at the target time, adjust and fuse the correlation factors under each laminar flow to obtain the rotational speed correction weight at this motor speed. If the Taylor number corresponding to the motor speed is greater than the critical Taylor number; obtain the rotational speed correction weight at this motor speed according to the numerical difference between the Taylor number and the critical Taylor number at the motor speed, and the change fluctuation of the flow rate value at the monitoring position within the preset time period. During the current test process, adjust the motor speed based on the rotational speed correction weight corresponding to the motor speed to obtain the adjusted rotational speed; under the adjusted rotational speed, change various parameters in the test process to simulate different working conditions.

[0006] Further, the method for obtaining the correlation factor includes: Under each laminar flow, arrange the monitoring positions in an orderly manner along the central axis direction of the outer cylinder to obtain a sorting sequence; Under the sorting sequence, calculate the Pearson correlation coefficient between the temperature value sequence and the flow rate scalar sequence of the fluid at all monitoring positions at the target time, and normalize the Pearson correlation coefficient to obtain the correlation factor.

[0007] Further, the rotational speed correction weight when the Taylor number corresponding to the motor speed is less than or equal to the critical Taylor number is used as the first rotational speed correction weight, and the rotational speed correction weight when the Taylor number corresponding to the motor speed is greater than the critical Taylor number is used as the second rotational speed correction weight.

[0008] Further, the method for obtaining the first rotational speed correction weight includes: Under all laminar flows, along the radial direction of the outer cylinder, all monitoring positions at the same height are regarded as the same type of monitoring positions, and clustering analysis is performed on each type of monitoring positions based on the K-means clustering algorithm and the preset K value to obtain the clustering clusters corresponding to each type of monitoring positions, where the distance metric is the absolute value of the difference in the temperature values of the fluid between the monitoring positions at the target time. Optionally select one laminar flow as the target laminar flow and other laminar flows as the comparison laminar flows. Under the target laminar flow, in each clustering cluster to which the monitoring positions belong, analyze the difference characteristics of the temperature values and the difference characteristics of the flow velocity values of the fluid between the monitoring positions belonging to the target laminar flow and the monitoring positions belonging to the comparison laminar flows, and determine the influence factors for each monitoring position under the target laminar flow; Based on the numerical characteristics and fluctuation conditions of the influence factors of the monitoring positions under each laminar flow, correct the relevant factors to obtain the viscosity correction factor for each laminar flow; Under each laminar flow, fuse the difference characteristics of the flow velocity values of the fluid between adjacent monitoring positions to determine the flow velocity similarity factor, where the value of the flow velocity similarity factor is a normalized value; Use the flow velocity similarity factor of the laminar flow to perform weighted averaging on the viscosity correction factor, and take the obtained weighted result as the first rotational speed correction weight at the motor rotational speed.

[0009] Furthermore, the method for obtaining the influence factor includes: Under the target laminar flow, in each clustering cluster to which the monitoring positions belong; At the target moment, calculate the absolute value of the difference between the mean value of the temperature values of the fluid at the monitoring positions belonging to the target laminar flow and the mean value of the temperature values of the fluid at the monitoring positions belonging to the comparison laminar flow to obtain the temperature difference factor; At the target moment, calculate the absolute value of the difference between the mean value of the flow velocity value scalars of the fluid at the monitoring positions belonging to the target laminar flow and the mean value of the flow velocity value scalars of the fluid at the monitoring positions belonging to the comparison laminar flow to obtain the flow velocity difference factor; Take the normalized value of the product of the temperature difference factor and the flow velocity difference factor corresponding to each monitoring position under the target laminar flow as the influence factor for each monitoring position under the target laminar flow.

[0010] Furthermore, the method for obtaining the viscosity correction factor includes: Under each laminar flow, add the standard deviation of the influence factors of all monitoring positions to the mean value of the influence factors of all monitoring positions, and take the value obtained after performing negative correlation mapping on the sum value as the correction coefficient; Take the product of the correction coefficient corresponding to each laminar flow and the relevant factor as the viscosity correction factor for each laminar flow.

[0011] Furthermore, the method for obtaining the flow velocity similarity factor includes: Under each laminar flow, arrange the monitoring positions in an orderly manner along the outer cylinder central axis direction to obtain a sorting sequence; Under the sorting sequence, calculate the absolute value of the difference between the flow velocity value scalars of the fluid between every two adjacent monitoring positions at the target moment as the flow velocity difference parameter; The value obtained by performing negative correlation mapping and normalization on the mean of all flow velocity difference parameters corresponding to the sorting sequence is used as the flow velocity similarity factor for each laminar flow.

[0012] Further, the method for obtaining the second rotational speed correction weight includes: In the flow velocity data at each monitoring position, the magnitude of the absolute value of the difference between the velocity vectors at every two adjacent moments is used as the flow velocity difference coefficient; The value obtained by normalizing the mean of all flow velocity difference coefficients corresponding to all monitoring positions is used as the first rotational speed adjustment factor; The difference between the actual Taylor number and the critical Taylor number is used as the second rotational speed adjustment factor; The value obtained by performing negative correlation mapping and normalization on the product of the first rotational speed adjustment factor and the second rotational speed adjustment factor is used as the second rotational speed correction weight at the motor rotational speed.

[0013] Further, the method for obtaining the adjusted rotational speed includes: The sum value of the value obtained by normalizing the rotational speed correction weight corresponding to the motor rotational speed in the current test process and a preset parameter is used as the rotational speed adjustment factor; The product of the rotational speed adjustment factor and the motor rotational speed in the current test process is used as the adjusted rotational speed in the current test process.

[0014] An experimental device for Taylor-Couette flow under different working conditions, the experimental device includes a radially grooved housing and a rotating shaft, the radially grooved housing and the rotating shaft form an inner and outer cylindrical annular space, on the same axial section of the inner and outer cylindrical annular space, a plurality of monitoring positions are arranged along the outer cylindrical radius direction, an infrared thermometer and a laser Doppler velocimeter are installed on the radially grooved housing, used to obtain the temperature data and flow velocity data of the fluid at each monitoring position during each Taylor-Couette flow test process, the experimental device is also provided with a control module, the control module is used to adjust the motor rotational speed of the variable frequency motor in the current test process according to the rotational speed correction weight of the motor rotational speed in the historical test process, so as to implement the steps of an experimental method for Taylor-Couette flow under different working conditions.

[0015] The present invention has the following beneficial effects: By arranging multiple monitoring positions along the radial direction of the outer cylinder on the same axial section of the inner and outer cylindrical annular space, the distribution characteristics of fluid temperature and flow velocity can be accurately captured, providing high-resolution data for subsequent analysis. The fluid states corresponding to different motor speeds are different, so the historical test processes can be classified. If the Taylor number corresponding to the motor speed is less than or equal to the critical Taylor number, the fluid is considered to be in a laminar flow state. Given that temperature differences will cause differences in the flow velocities of the fluid at each monitoring position, the variation relationship between the temperature value and the flow velocity value is analyzed under each laminar flow, and a correlation factor is obtained to quantify the influence of the viscosity dynamic change caused by temperature fluctuations on the flow resistance. Further, the temperature difference between different laminar flows will lead to instability between adjacent laminar flows, inducing fluctuations in the local flow velocity. Therefore, there may be certain errors in the variation correlation relationship used to calculate the correlation factor. So, the correlation factors under each laminar flow are adjusted and fused according to the temperature value differences and flow velocity value differences between the monitoring positions to obtain the rotational speed correction weight at the motor speed, improving the flow prediction accuracy. When the Taylor number corresponding to the motor speed is greater than the critical Taylor number, the flow velocity of the fluid becomes more complex. Given that the Taylor number is the most important parameter in fluid mechanics, used to quantify the relative magnitudes of inertial forces and viscous forces in fluid flow, the rotational speed correction weight at the motor speed is obtained through the dynamic ratio of the actual Taylor number to the critical Taylor number and the variation fluctuations of the flow velocity values at the monitoring positions. Finally, a mapping relationship between the motor speed and the rotational speed correction weight is established, and the rotational speed correction weight is used to adjust the motor speed in the current test process, forming a closed-loop feedback control strategy, enabling the rotational speed adjustment to better respond to the changes in the flow state, effectively improving the dynamic adaptability of the working condition simulation, and thus improving the accuracy of the working condition simulation. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the accompanying drawings required for use in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a device structure diagram of a Taylor-Couette flow test device under different working conditions provided by an embodiment of the present invention; Figure 2 It is a structural schematic diagram of a control module provided by an embodiment of the present invention; Figure 3 It is a method flowchart of a Taylor-Couette flow test method under different working conditions provided by an embodiment of the present invention; Figure 4The flowchart of a method for obtaining a first rotational speed correction weight provided by an embodiment of the present invention; Reference numerals: 1 - medium inlet; 2 - induction heater, 3 - infrared thermometer, 4 - variable frequency motor, 5 - laser Doppler velocimeter, 6 - flow meter, 7 - lower heat insulation plate, 8 - rotating shaft, 9 - housing with radial grooves, 10 - upper heat insulation plate, 11 - medium outlet; 200 - processor, 201 - memory, 202 - bus, 203 - communication interface. Detailed implementation manners

[0018] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines the drawings and preferred embodiments to detail the specific implementation manners, structures, features and effects of a Taylor - Couette flow test method and test device under different working conditions according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0020] The following specifically describes the specific solutions of a Taylor - Couette flow test method and test device provided by the present invention with reference to the drawings.

[0021] Please refer to Figure 1 , which shows the device structure diagram of a Taylor - Couette flow test device provided by an embodiment of the present invention.

[0022] The fluid enters the test device from the medium inlet 1 via the flow meter 6, and the flow meter 6 ensures that the fluid enters at a predetermined flow rate; the inner and outer cylindrical annular space formed between the housing 9 with radial grooves and the rotating shaft 8 in the test device is the Taylor - Couette flow fluid region, serving as the flow test region. An infrared thermometer 3 and a laser Doppler velocimeter 5 are installed on the housing 9 with radial grooves to obtain the temperature data and flow velocity data of the fluid at each monitoring position on the same axial section of the inner and outer cylindrical annular space during each Taylor - Couette flow test, where the monitoring positions are evenly distributed along the outer cylindrical radius direction on the axial section. Two heat insulation plates, namely the lower heat insulation plate 7 and the upper heat insulation plate 10, are also added to the test device, so that the flow state of the fluid in actual operation can be maximally simulated during the test, and the fluid medium can be evenly distributed into the cavity. The induction heater 2 further processes the fluid, used to heat the fluid or perform some form of treatment on the fluid; the variable frequency motor 4 is used to control the fluid flow in the test device, and the fluid flows out through the medium outlet 11.

[0023] In view of the different temperature loss phenomena exhibited by the fluid during the Taylor-Cooter flow test, which will lead to uneven distribution of fluid viscosity and destroy the preset speed-flow rate model, in an embodiment of the present invention, a control module (not shown in the figure) is also provided in the test device. The control module can be used to adjust the motor speed of the variable frequency motor 4, so that the speed adjustment during the test process can better respond to changes in the flow state and improve the accuracy of the working condition simulation.

[0024] The control module includes at least a memory and a processor. Figure 2 , which shows a schematic diagram of the structure of a control module provided in one embodiment of the present invention, including a processor 200, a memory 201, a bus 202 and a communication interface 203, wherein the processor 200, the communication interface 203 and the memory 201 are connected via the bus 202; wherein the memory 201 may include a high-speed random access memory, the bus 202 may be an ISA bus, a PCI bus or an EISA bus, etc., and the processor 200 may be an integrated circuit chip with signal processing capabilities; the memory 201 stores at least one instruction, at least one program, a code set or an instruction set, and when the at least one instruction, at least one program, a code set or an instruction set is loaded and executed by the processor, the steps in a test method for Taylor-Cooter flow under different working conditions are implemented.

[0025] See also Figure 3 , which shows a method flow chart of a test method of Taylor-Cooter flow under different working conditions provided by an embodiment of the present invention, the method comprising the following steps: Step S1: at each motor speed in the historical test process, multiple monitoring positions are set along the radial direction of the outer cylinder on the same axial section of the inner and outer cylindrical annular spaces to obtain the temperature and flow rate of the fluid at the monitoring positions within a preset time period.

[0026] The Taylor-Coutt flow experiment aims to analyze the transformation law of flow field structure (such as laminar flow, Taylor vortex, spiral flow, turbulence), as well as angular momentum transmission efficiency and torque characteristics by changing the rotation speed of the inner / outer cylinder, gap width and other parameters. When the rotation speed of the inner cylinder is low, the fluid presents a stable laminar state (Couette laminar flow), the velocity distribution is linear, and there is no vortex structure. At this time, the flow is dominated by viscosity and the energy dissipation is uniform. In this embodiment of the present invention, the outer cylinder is stationary.

[0027] According to prior knowledge, laminar flow is a basic flow state in fluid mechanics to describe fluid motion. Its characteristic is that the fluid flows in a smooth and orderly stratified form, and the exchange of matter or energy only occurs between layers through molecular diffusion. However, due to the limited heat preservation effect of the actual test device on the flowing liquid, and as the liquid flows and contacts the device, the liquid itself has temperature loss. When simulating different actual working conditions, the temperature loss phenomena of the fluid at different positions are different. For example, in the high-shear region, heat is generated due to viscous dissipation, while the temperature of the pipe wall is relatively low due to heat dissipation, resulting in uneven distribution of fluid viscosity, forming complex flow resistance and destroying the preset rotational speed - flow velocity model.

[0028] Therefore, in this embodiment of the present invention, by analyzing the temperature data and flow velocity data of the fluid at each motor rotational speed in the historical test process, the motor rotational speed in the current test process is adjusted. Specifically, at each motor rotational speed in the historical test process, multiple monitoring positions are set along the outer cylinder radius direction on the same axial section of the inner and outer cylindrical annular spaces under each laminar flow. Based on the infrared thermometer 3 and the laser Doppler velocimeter 5, the temperature data and flow velocity data of the fluid at each monitoring position are obtained.

[0029] It should be noted that in the embodiment of the present invention, the acquisition moments of the temperature data and flow velocity data of the fluid at all monitoring positions need to be consistent. Specifically, the temperature data and flow velocity data within the 3rd minute after the start of the test can be collected, that is, the preset time period is within the third minute after the start of the test. The selection of the specific time period can be adjusted according to the implementation scenario and is not limited here; and in the embodiment of the present invention, the acquisition of the flow velocity data is a vector, having magnitude and direction.

[0030] According to prior knowledge, the Taylor number is the most important dimensionless parameter in fluid mechanics, used to quantify the relative magnitude of the inertial force and viscous force in fluid flow. Through the Taylor number, laminar flow, turbulent flow or transitional state can be predicted. In the test device, the liquid changes from laminar flow to turbulent flow according to the actual inner cylinder rotational speed. In this process, at low Taylor numbers, the viscous force dominates and the flow is laminar; at high Taylor numbers, the inertial force dominates and the flow transitions to Taylor - Couette flow. In all historical test processes, the actual Taylor number under the motor rotational speed can be compared with the critical Taylor number to determine different states of the fluid, and then analyzed case by case to determine the corresponding rotational speed correction weight under the motor rotational speed, which represents the degree of adjustment of the motor rotational speed; and in this embodiment of the present invention, the rotational speed correction weight when the Taylor number corresponding to the motor rotational speed is less than or equal to the critical Taylor number is used as the first motor rotational speed correction weight, and the rotational speed correction weight when the Taylor number corresponding to the motor rotational speed is greater than the critical Taylor number is used as the second rotational speed correction weight.

[0031] In this embodiment of the present invention, the critical Taylor number is set to 1780.

[0032] Step S2: If the Taylor number corresponding to the motor speed is less than or equal to the critical Taylor number, determine the target time. Under each laminar flow, analyze the correlation between the temperature values and the flow velocity values at the monitoring positions at the target time to determine the correlation factor. According to the difference in temperature values and the difference in flow velocity values between the monitoring positions at the target time, adjust and fuse the correlation factors under each laminar flow to obtain the rotational speed correction weight at this motor speed.

[0033] When the actual Taylor number at the motor speed is less than or equal to the critical Taylor number, the viscous force dominates, and the fluid state mainly exhibits a laminar flow phenomenon. In the test device in the embodiment of the present invention, the induction heater 2 will further process the fluid. At this time, the heat loss of the fluid closer to the inner cylinder is slower than that of the fluid closer to the outer cylinder. According to prior knowledge, if the fluid velocities corresponding to different positions are different, it is mainly affected by the combined action of centrifugal force and liquid viscosity. At this time, due to the influence of temperature, the temperature difference at different positions will cause differences in the liquid flow velocities at each position point; therefore, under each laminar flow, the reason for the flow velocity difference is also affected by the temperature difference; when the temperature rises, the fluid viscosity decreases, and the flow resistance decreases, resulting in an increase in the flow velocity at the same motor speed, and vice versa.

[0034] Because the laminar flow state is relatively stable, first randomly select a time as the target time in the preset time period (for example, select the middle time as the target time in this embodiment of the present invention), and then analyze the correlation between the temperature values and the flow velocity values at the monitoring positions at the target time to determine the correlation factor, which is used to initially reflect the influence of the viscosity dynamic change caused by temperature fluctuations on the flow velocity.

[0035] Preferably, in an embodiment of the present invention, the method for obtaining the correlation factor includes: Under each laminar flow, arrange the monitoring positions (randomly select one under each laminar flow) in an orderly manner along the central axis direction of the outer cylinder to obtain a sorting sequence.

[0036] Under the sorting sequence, calculate the Pearson correlation coefficient between the temperature value sequence and the flow velocity scalar sequence (only discuss the magnitude of the flow velocity value) of the fluid at all monitoring positions at the target time. The value range of the Pearson correlation coefficient is -1 to 1. The closer it is to 1, it indicates that the changes in the temperature value sequence and the flow velocity value sequence show a more positive correlation relationship. Then, based on the foregoing analysis, it can be regarded that the greater the influence of temperature on the flow velocity. Therefore, normalize the Pearson correlation coefficient to obtain the correlation factor. The greater the correlation factor, the greater the influence of temperature on the flow velocity of the fluid. In view of the fact that the value of the Pearson correlation coefficient may be positive or negative, the normalization process here can adopt Function.

[0037] It should be noted that the calculation process of the Pearson correlation coefficient is well-known technology and will not be elaborated here.

[0038] Under laminar flow conditions, most of the fluid flow is in a stable state. However, the uneven distribution of temperature and flow velocity between adjacent laminar flows will induce fluctuations in the local flow velocity, that is, the boundary layer effect. Therefore, there may be certain errors in calculating the correlation relationship of the change of relevant factors based on the temperature values and flow velocity values under each laminar flow. Therefore, the relevant factors under each laminar flow are adjusted and fused according to the difference in temperature values and the difference in flow velocity values between all laminar flow monitoring positions at the target moment, and the rotational speed correction weight at the motor rotational speed during each historical test process is obtained, improving the flow prediction accuracy and significantly reducing the error of fluid state simulation under complex working conditions.

[0039] Preferably, in one embodiment of the present invention, the method for obtaining the first rotational speed correction weight includes: Please refer to Figure 4 , which shows the method flow chart of the method for obtaining the first rotational speed correction weight in one embodiment of the present invention. The method includes the following steps: Step S201: Under all laminar flows, perform cluster analysis on the monitoring positions according to the difference in temperature values of the fluid between the monitoring positions to obtain cluster clusters.

[0040] When the laminar flow phenomenon occurs, the flow velocity of the liquid between adjacent two layers of liquid will be different, and the temperature will also be different. Then it will lead to instability between adjacent laminar flows and induce local fluctuations. The calculation of the aforementioned relevant factors is to analyze the difference in temperature values and flow velocity values between different monitoring positions in each laminar flow. At the same position (same height) in different laminar flows, when the temperature difference is large and the flow velocity also has a large difference, then it is considered that the influence of the boundary layer effect between different laminar flows on the relevant factors is large, and then the confidence level of the relevant factors should be reduced.

[0041] First, cluster analysis can be performed based on the difference in temperature values between the monitoring positions to obtain cluster clusters.

[0042] Under all laminar flows, in the direction of the outer cylinder radius, all monitoring positions at the same height are regarded as the same type of monitoring positions, and all monitoring positions are preliminarily classified in this way.

[0043] Then, perform cluster analysis on each type of monitoring position based on the K-means clustering algorithm and the preset K value to obtain the cluster clusters corresponding to each type of monitoring position.

[0044] Among them, the distance metric is the absolute value of the difference in temperature values of the fluid between the monitoring positions at the target moment, and the optimal K value obtained based on the elbow method is used as the preset K value.

[0045] At this point, clustering analysis can be performed on all monitoring positions, such that under all laminar flows, among all monitoring positions at the same height, the monitoring positions with a high similarity in temperature values are grouped into a clustering cluster, thereby obtaining several clustering clusters with the same or approximate temperature distributions.

[0046] It should be noted that both the K-means clustering algorithm and the elbow method are well-known technologies, and the specific processes will not be elaborated here.

[0047] Step S202: Arbitrarily select one laminar flow as the target laminar flow and other laminar flows as the comparison laminar flows. Under the target laminar flow, in each clustering cluster to which a monitoring position belongs, analyze the difference characteristics of the temperature values and the difference characteristics of the flow velocity values of the fluid between the monitoring positions belonging to the target laminar flow and the monitoring positions belonging to the comparison laminar flows, and determine the influencing factors for each monitoring position under the target laminar flow.

[0048] In the foregoing clustering analysis, the monitoring positions at the same height under all laminar flows are clustered based on temperature values. Therefore, the monitoring positions in some clustering clusters may span multiple laminar flows. Thus, in this step, the boundary layer effect can be further analyzed on this basis for a preliminary correction of relevant factors in the subsequent process.

[0049] For the convenience of explanation and illustration, arbitrarily select one laminar flow as the target laminar flow and the other laminar flows as the comparison laminar flows. Under the target laminar flow, in each clustering cluster to which a monitoring position belongs, at the target moment, calculate the absolute value of the difference between the mean temperature value of the fluid of the monitoring positions belonging to the target laminar flow and the mean temperature value of the fluid of the monitoring positions belonging to the comparison laminar flows to obtain the temperature difference factor. The larger the temperature difference factor, the greater the difference in temperature values among the monitoring positions at the same height. Using the same method, at the target moment, calculate the absolute value of the difference between the mean scalar of the flow velocity values of the fluid of the monitoring positions belonging to the target laminar flow and the mean scalar of the flow velocity values of the fluid of the monitoring positions belonging to the comparison laminar flows to obtain the flow velocity difference factor. The larger the flow velocity difference factor, the greater the difference in flow velocity values among the monitoring positions at the same height.

[0050] When both the temperature difference factor and the flow velocity difference factor are larger, it indicates that the influence of temperature on fluid velocity is greater and the boundary layer effect is more obvious. Therefore, the value obtained by normalizing the product of the temperature difference factor and the flow velocity difference factor corresponding to each monitoring position under the target laminar flow is used as the influencing factor for each monitoring position under the target laminar flow. The larger the influencing factor, the greater the local fluctuation suffered by the target laminar flow, and then the lower the confidence level of the corresponding relevant factor.

[0051] Step S203: Based on the numerical characteristics and fluctuation conditions of the influence factors at the monitoring positions under each laminar flow, preliminarily correct the relevant factors to obtain the viscous correction factor under each laminar flow.

[0052] Based on the foregoing steps, the influence factor corresponding to each monitoring position under each laminar flow can be obtained. The larger the influence factor, the lower the confidence level of the relevant factor corresponding to the laminar flow. Here, under each laminar flow, the standard deviation of the influence factors of all monitoring positions can be calculated. The smaller the standard deviation, the smaller the fluctuation of the influence factors of all monitoring positions under this laminar flow, and the more concentrated the distribution. Then, add the standard deviation to the mean value of the influence factors of all monitoring positions. The smaller the obtained sum value, the smaller the local fluctuation of the monitoring positions under this laminar flow, and the more concentrated the distribution. Therefore, the confidence level of the relevant factor corresponding to this laminar flow is higher. Therefore, perform a negative correlation mapping process on the foregoing sum value to correct the logical relationship and obtain a correction coefficient. The larger the correction coefficient, the higher the confidence level of the relevant factor. The negative correlation mapping here can adopt the formula , where represents the exponential function with the natural constant e as the base, and x represents the independent variable.

[0053] Finally, take the product of the correction coefficient corresponding to each laminar flow and the relevant factor as the viscous correction factor under each laminar flow. At this time, the larger the viscous correction factor, the greater the influence of temperature on the fluid flow rate.

[0054] Step S204: Under each laminar flow, fuse the difference characteristics of the fluid flow rate values between adjacent monitoring positions to determine the flow rate similarity factor.

[0055] When the rotational speed of the inner cylinder is greater, the viscosity between the liquids decreases, and the fluid flow rate difference between different monitoring positions corresponding to the same laminar flow gradually increases; the greater the fluid flow rate difference, the lower the dominant weight of viscosity, and the lower the reference weight of the viscous correction factor.

[0056] Therefore, under each laminar flow, arrange the monitoring positions in an orderly manner along the direction of the outer cylinder central axis to obtain a sorting sequence.

[0057] Under the sorting sequence, calculate the absolute value of the difference between the scalar values of the fluid flow rates at the target moment between every two adjacent monitoring positions as the flow rate difference parameter. The larger the flow rate difference parameter, the greater the deviation of the fluid flow rate values between two adjacent monitoring positions, and then the dominant weight of viscosity needs to be reduced.

[0058] The value obtained by performing negative correlation mapping and normalization on the mean of all flow velocity difference parameters corresponding to the sorting sequence is used as the flow velocity similarity factor for each laminar flow. It can be understood that the larger the flow velocity similarity factor at this time, the higher the similarity of the flow velocity values of the fluid between the monitoring positions under each laminar flow, and then the higher the reference weight of the viscosity correction factor. The negative correlation mapping and normalization process here can be carried out using the formula , where represents the exponential function with the natural constant e as the base, and x represents the independent variable.

[0059] Step S205: Integrate the flow velocity similarity factor and the viscosity correction factor of the laminar flow to obtain the first rotational speed correction weight at the motor rotational speed during each historical test.

[0060] Based on the foregoing steps, the flow velocity similarity factor and the viscosity correction factor of each laminar flow can be obtained. And when the actual Taylor number at the motor rotational speed is less than or equal to the critical Taylor number, the viscous force dominates and the laminar flow is stable. Therefore, here, the viscosity correction factor is weighted and averaged using the flow velocity similarity factor of the laminar flow, and the obtained weighted result is directly used as the first rotational speed correction weight at the motor rotational speed during each historical test. At this time, the motor rotational speed correction weight incorporates the influence of temperature on the flow velocity, and thus can more accurately reflect the change characteristics of the fluid viscosity generated with the change of temperature. Moreover, the larger the first rotational speed correction weight, the greater the fluid viscosity, and the variable-frequency motor needs to output a larger torque to maintain the rotational speed. On the contrary, the smaller the first rotational speed correction weight, the smaller the fluid viscosity, and the state is closer to the critical state, and the rotational speed can be appropriately reduced to maintain the laminar flow stability.

[0061] Step S3: If the Taylor number corresponding to the motor rotational speed is greater than the critical Taylor number; based on the numerical difference between the Taylor number and the critical Taylor number at the motor rotational speed, and the change fluctuation of the flow velocity value at the monitoring position within the preset time period, obtain the rotational speed correction weight at the motor rotational speed.

[0062] When the critical Taylor number is reached and the liquid is in the range between the critical Taylor number and the critical threshold of turbulence, the state of the liquid changes from laminar flow to Taylor-Couette flow. The fluid is no longer a simple circumferential laminar flow, but forms pairs of reverse rotating vortex rings. These vortex rings are periodically arranged alternately along the axial direction of the cylinder. In the laminar flow state, theoretically, the directions of the flow velocity values at each detection position are parallel to each other. However, at this time, the direction of the flow velocity also changes, and the flow is axisymmetric about the rotation axis (that is, in any circumferential direction at the same axial position, the flow pattern is exactly the same). According to the analysis, when near the critical conditions and with good parameter control, the position, size, and intensity of the vortex cells do not change with time, which is one of the most fundamental differences from the subsequent wavy eddy currents and turbulence. Therefore, based on the numerical difference characteristics between the Taylor number at the motor speed and the critical Taylor number, as well as the variation fluctuations of the flow velocity values at the monitoring positions within a preset period, the rotational speed correction weight (the second rotational speed correction weight) at the motor speed can be obtained.

[0063] Preferably, in an embodiment of the present invention, the method for obtaining the second rotational speed correction weight includes: In the flow velocity data at each monitoring position, the modulus of the absolute value of the difference between the flow velocity vectors at every two adjacent moments is used as the flow velocity difference coefficient. The smaller the flow velocity difference coefficient, the lower the complexity of the change in the flow velocity values at the monitoring position at different moments under the current rotational speed, indicating that the fluid state is more stable and the need to lower the feedback of the motor rotational speed is lower. Therefore, the mean value of all the flow velocity difference coefficients corresponding to all the monitoring positions is normalized and used as the first rotational speed adjustment factor. The larger the first rotational speed adjustment factor, the greater the need to lower the motor rotational speed.

[0064] The difference between the actual Taylor number and the critical Taylor number is used as the second rotational speed adjustment factor. The larger the second rotational speed adjustment factor, the greater the degree of exceeding the critical state. At this time, the possibility of changes in the position, size, and intensity of the vortex cells is greater. Therefore, in order to maintain stability, it is necessary to lower the motor rotational speed.

[0065] Finally, the value obtained by performing negative correlation mapping normalization on the product of the first rotational speed adjustment factor and the second rotational speed adjustment factor is used as the second rotational speed correction weight at the motor speed. The larger the second rotational speed correction weight, the greater the need to increase the motor rotational speed. On the contrary, the smaller the second rotational speed correction weight, the more chaotic the fluid state, and the rotational speed can be appropriately lowered to maintain fluid stability. The negative correlation mapping and normalization can be performed using the formula , where represents the exponential function with the natural constant e as the base, and x represents the independent variable.

[0066] Step S4: During the current test process, adjust the motor speed based on the speed correction weight corresponding to the motor speed to obtain an adjusted speed; under the adjusted speed, change various parameters in the test process to simulate different working conditions.

[0067] Based on the foregoing steps, the speed correction weight corresponding to each motor speed can be obtained. Then, during the current test process, the motor speed can be adjusted based on the speed correction weight corresponding to the motor speed to obtain an adjusted speed.

[0068] Preferably, in an embodiment of the present invention, the method for obtaining the adjusted speed includes: Take the sum value of the normalized value of the speed correction weight corresponding to the motor speed in the current test process and a preset parameter as the speed adjustment factor. Based on the analysis in Steps S2 and S3, the larger the speed correction weight, the higher the speed of the variable-frequency motor can be appropriately increased. Conversely, the smaller the speed correction weight, the lower the speed of the variable-frequency motor can be appropriately decreased. Therefore, here, the speed correction weight corresponding to the motor speed in the current test process is normalized so that its value range is between 0 and 1. Then, take the sum value of the normalized value and the preset parameter as the speed adjustment factor. In this embodiment of the present invention, the preset parameter is set to 0.5. At this time, the speed adjustment factor is greater than 1, and the speed can be increased. Conversely, if the speed adjustment factor is still less than 1, the speed can be decreased. Normalization is a well-known technical means to those skilled in the art. The selection of the normalization function can be linear normalization or standard normalization, etc. The specific normalization method is not limited herein.

[0069] Finally, take the product of the speed adjustment factor and the motor speed in the current test process as the adjusted speed in the current test process.

[0070] So far, by analyzing the influence of temperature change on fluid flow rate, the motor speed of the variable-frequency motor 4 in the test process can be adjusted, so that it can better respond to the flow change of the fluid. Furthermore, through the control variable method, by changing various parameters in the test process, such as the gap width, the ratio of the inner and outer cylinder radii, etc., simulations under various working conditions can be carried out, improving the dynamic adaptability and accuracy of the working condition simulation.

[0071] In summary, by arranging multiple monitoring positions along the radial direction of the outer cylinder on the same axial section of the inner and outer cylindrical annular spaces, the distribution characteristics of the fluid temperature and flow rate can be accurately captured, providing high-resolution data for subsequent analysis. Different fluid states correspond to different motor speeds, so the historical test processes can be classified. If the Taylor number corresponding to the motor speed is less than or equal to the critical Taylor number, the fluid is considered to be in a laminar flow state. Given that temperature differences will cause differences in the flow rates of the fluid at each monitoring position, the variation relationship between the temperature value and the flow rate value is analyzed under each laminar flow, and relevant factors are obtained to quantify the influence of the viscosity dynamic change caused by temperature fluctuations on the flow resistance. Further, the temperature difference between different laminar flows will lead to instability between adjacent laminar flows, inducing fluctuations in the local flow rate. Therefore, there may be certain errors in the variation relationship used to calculate the relevant factors. So, according to the temperature value differences and flow rate value differences between the monitoring positions, the relevant factors under each laminar flow are adjusted and fused to obtain the rotational speed correction weight at the motor speed, improving the flow prediction accuracy. When the Taylor number corresponding to the motor speed is greater than the critical Taylor number, the flow rate of the fluid becomes more complex. Since the Taylor number is the most important parameter in fluid mechanics, used to quantify the relative magnitudes of inertial forces and viscous forces in fluid flow, the rotational speed correction weight at the motor speed is obtained through the dynamic ratio of the actual Taylor number to the critical Taylor number and the variation fluctuations of the flow rate values at the monitoring positions. Finally, a mapping relationship between the motor speed and the rotational speed correction weight is established, and the rotational speed correction weight is used to adjust the motor speed in the current test process, forming a closed-loop feedback control strategy, enabling the rotational speed adjustment to better respond to changes in the flow state, effectively improving the dynamic adaptability of the working condition simulation, and thus enhancing the accuracy of the working condition simulation.

[0072] It should be noted that the above sequence of the embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0073] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. An experimental method for Taylor-Couette flow under different working conditions, characterized in that, The method includes: At each motor speed during the historical test process, on the same axial section of the inner and outer cylindrical annular space, a plurality of monitoring positions are set along the radial direction of the outer cylinder, and the temperature and flow rate of the fluid at the monitoring positions within a preset time period are obtained; If the Taylor number corresponding to the motor speed is less than or equal to the critical Taylor number; determine the target time, under each laminar flow, analyze the correlation between the temperature values and flow rate values between the monitoring positions at the target time, and determine the correlation factor; according to the difference in temperature values and the difference in flow rate values between the monitoring positions at the target time, adjust and fuse the correlation factors under each laminar flow to obtain the rotational speed correction weight at this motor speed; If the Taylor number corresponding to the motor speed is greater than the critical Taylor number; according to the numerical difference between the Taylor number and the critical Taylor number at the motor speed, and the change fluctuation of the flow rate value of the monitoring position within a preset time period, obtain the rotational speed correction weight at this motor speed; During the current test process, adjust the motor speed based on the rotational speed correction weight corresponding to the motor speed to obtain the adjusted rotational speed; under the adjusted rotational speed, change various parameters in the test process to simulate different working conditions.

2. The experimental method of Taylor-Couette flow under different working conditions according to claim 1, characterized in that The method for obtaining the correlation factor includes: Under each laminar flow, arrange the monitoring positions in an orderly manner along the central axis direction of the outer cylinder to obtain a sorting sequence; Under the sorting sequence, calculate the Pearson correlation coefficient between the temperature value sequence and the flow rate value scalar sequence of the fluid at all monitoring positions at the target time, and normalize the Pearson correlation coefficient to obtain the correlation factor.

3. The experimental method of Taylor-Couette flow under different working conditions according to claim 1, characterized in that, Take the rotational speed correction weight when the Taylor number corresponding to the motor speed is less than or equal to the critical Taylor number as the first rotational speed correction weight, and take the rotational speed correction weight when the Taylor number corresponding to the motor speed is greater than the critical Taylor number as the second rotational speed correction weight.

4. The experimental method of Taylor-Couette flow under different working conditions according to claim 3, characterized in that, The method for obtaining the first rotational speed correction weight includes: Under all laminar flows, along the radial direction of the outer cylinder, take all monitoring positions at the same height as the same type of monitoring positions, and perform clustering analysis on each type of monitoring position based on the K-means clustering algorithm and a preset K value to obtain the clustering clusters corresponding to each type of monitoring position, where the distance metric is the absolute value of the difference in temperature values of the fluid between the monitoring positions at the target time; Optionally select one laminar flow as the target laminar flow and other laminar flows as the comparison laminar flows. Under the target laminar flow, in the clustering cluster to which each monitoring position belongs, analyze the difference characteristics of the temperature value and the difference characteristics of the flow rate value of the fluid between the monitoring positions belonging to the target laminar flow and the monitoring positions belonging to the comparison laminar flows, and determine the influence factor of each monitoring position under the target laminar flow; Based on the numerical characteristics and fluctuation conditions of the influence factors of the monitoring positions under each laminar flow, correct the correlation factors to obtain the viscous correction factors under each laminar flow; Under each laminar flow, fuse the difference characteristics of the flow rate values between adjacent monitoring positions to determine the flow rate similarity factor, where the value of the flow rate similarity factor is a normalized value; Use the flow rate similarity factor of the laminar flow to perform weighted averaging on the viscous correction factor, and take the obtained weighted result as the first rotational speed correction weight at the motor speed.

5. The experimental method for Taylor-Couette flow under different working conditions according to claim 4, wherein The method for obtaining the influence factor includes: Under the target laminar flow, within the clustering cluster to which each monitoring position belongs; At the target moment, calculate the absolute value of the difference between the mean value of the temperature values of the fluid at the monitoring positions belonging to the target laminar flow and the mean value of the temperature values of the fluid at the monitoring positions belonging to the comparison laminar flow, to obtain the temperature difference factor; At the target moment, calculate the absolute value of the difference between the mean value of the scalar values of the flow velocities of the fluid at the monitoring positions belonging to the target laminar flow and the mean value of the scalar values of the flow velocities of the fluid at the monitoring positions belonging to the comparison laminar flow, to obtain the flow velocity difference factor; The value obtained by normalizing the product of the temperature difference factor and the flow velocity difference factor corresponding to each monitoring position under the target laminar flow is used as the influence factor for each monitoring position under the target laminar flow.

6. The experimental method of Taylor-Couette flow under different working conditions according to claim 4, characterized in that The method for obtaining the viscosity correction factor includes: Under each laminar flow, add the standard deviation of the influence factors of all monitoring positions to the mean value of the influence factors of all monitoring positions, and use the value obtained by performing a negative correlation mapping on the obtained sum value as the correction coefficient; The product of the correction coefficient corresponding to each laminar flow and the correlation factor is used as the viscosity correction factor for each laminar flow.

7. A test method for Taylor-Couette flow under different working conditions according to claim 4, characterized in that The method for obtaining the flow velocity similarity factor includes: Under each laminar flow, arrange the monitoring positions in an orderly manner along the central axis direction of the outer cylinder to obtain a sorting sequence; Under the sorting sequence, calculate the absolute value of the difference between the scalar values of the flow velocities of the fluid at every two adjacent monitoring positions at the target moment as the flow velocity difference parameter; The value obtained by performing a negative correlation mapping and normalizing the mean value of all the flow velocity difference parameters corresponding to the sorting sequence is used as the flow velocity similarity factor for each laminar flow.

8. A test method for Taylor-Couette flow under different working conditions according to claim 3, characterized in that, The method for obtaining the second rotational speed correction weight includes: In the flow velocity data of each monitoring position, take the modulus of the absolute value of the difference between the flow velocity vectors at every two adjacent moments as the flow velocity difference coefficient; The value obtained by normalizing the mean value of all the flow velocity difference coefficients corresponding to all monitoring positions is used as the first rotational speed adjustment factor; Take the difference between the actual Taylor number and the critical Taylor number as the second rotational speed adjustment factor; The value obtained by performing a negative correlation mapping and normalizing the product of the first rotational speed adjustment factor and the second rotational speed adjustment factor is used as the second rotational speed correction weight at the motor rotational speed.

9. The experimental method for Taylor-Couette flow under different working conditions according to claim 1, wherein, The method for obtaining the adjusted rotational speed includes: Use the sum value of the value obtained by normalizing the rotational speed correction weight corresponding to the motor rotational speed in the current test process and the preset parameter as the rotational speed adjustment factor; The product of the rotational speed adjustment factor and the motor rotational speed in the current test process is used as the adjusted rotational speed in the current test process.

10. An experimental device for Taylor-Couette flow under different working conditions, characterized in that, The test device includes a housing with radial grooves and a rotating shaft. The housing with radial grooves and the rotating shaft form an inner and outer cylindrical annular space. On the same axial section of the inner and outer cylindrical annular space, a plurality of monitoring positions are arranged along the radial direction of the outer cylinder radius. An infrared thermometer and a laser Doppler velocimeter are installed on the housing with radial grooves, and are used to obtain the temperature data and flow velocity data of the fluid at each monitoring position during each Taylor-Couette flow test process. The test device is also provided with a control module, and the control module is used to adjust the motor speed of the variable-frequency motor during the current test process according to the speed correction weight of the motor speed in the historical test process, so as to implement the steps of the test method of Taylor-Couette flow under different working conditions according to any one of claims 1 to 9.

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