Experimental method and device for testing shear degradation rule of polymer solution

Abstract

The invention discloses an experimental method and device for testing the shear degradation rule of a polymer solution, and belongs to the technical field of liquid transmission. Building an experimental device, wherein the experimental device is a pipeline circulating system for measuring the influence of pump shearing on the characteristic change of the measured working medium; the tested pump is started, and the device is preheated by running for set time at the maximum power; discharging the preheated working medium, and injecting the measured working medium; adjusting the power of the tested pump to an experimental working condition, measuring the pressure difference of the tested working medium before and after the test pipeline according to a set period, and calculating to obtain the drag reduction rate of the tested working medium; and all variables in a pipeline circulation system are adjusted, the change condition of the drag reduction rate along with time is obtained, and the influence rule of pump shearing on high polymer degradation is obtained. The invention solves the problem that the current test equipment only pays attention to the influence of the working medium on the pump efficiency and does not monitor the change of the working medium after the shearing action of the pump.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid transmission, and in particular relates to an experimental method and a device for testing the shear degradation law of a polymer solution. Background Art

[0002] Pipeline transportation is a conventional mode of transportation for transporting liquids and gases. It is widely used in production and life, such as oil pipelines, heating pipelines, etc. It has the characteristics of large transportation volume, low cost, safety and reliability. In pipeline transportation, the loss caused by pipe wall friction accounts for the vast majority of the total transportation loss. Therefore, reducing the friction resistance of the pipe wall can effectively improve efficiency, save energy and protect the environment. Polymers have a long chain structure, which can significantly inhibit the development of turbulent vortex structures in the flow field, weaken flow energy dissipation, and greatly reduce flow resistance. It is a drag reducer with a very wide range of applications. At present, polymer drag reducers have been used in the flow of pipelines such as oil pipelines and fire hoses and have achieved good drag reduction effects.

[0003] As the main driving component, the pump is indispensable in the pipeline system. However, while driving the liquid in the pipeline, it will also produce a large shear on the liquid, which may cause shear degradation of the polymer, thus affecting its drag reduction ability to a certain extent. The different speeds of the pump, the different types and concentrations of drag reducers, etc. will affect the degradation. Therefore, quantitative testing of the changes in the shear degradation rate of different drag reducers for different pumps under different working conditions will help to select the driving pump with the least damage to the drag reducer and the optimal working environment. The current pipeline system experimental equipment for drag reducing additives is relatively diverse. However, there are still the following shortcomings:

[0004] 1. The experimental device has a complex structure, is difficult to build and debug, has high construction costs, and is inconvenient to disassemble and assemble components;

[0005] 2. Only focus on the impact of the working fluid on pump efficiency, and do not monitor the changes in the working fluid after being sheared by the pump.

[0006] 3. The pipes in the experimental device are opaque or the observation section is short, so pipeline cavitation cannot be discovered in time, affecting the accuracy of the measurement results and the range of measurable parameters. Summary of the invention

[0007] Technical issues to be solved:

[0008] In order to avoid the shortcomings of the prior art, the present invention provides an experimental method and device for testing the shear degradation law of polymer solutions. The device is a pipeline circulation system that can measure the influence of pump shear on the change of polymer solution characteristics. The differential pressure transmitter collects the pressure difference between the inlet and outlet of the drag reduction test pipeline, and then calculates the drag reduction rate of the measured working fluid, and reflects the performance of the measured working fluid through the drag reduction rate. In the experiment, the pump speed, pipeline pressure, action time, measured working fluid and solution concentration are variables. After the pipeline is fully circulated, the pump is kept running stably, and the differential pressure transmitter data is collected at the same time interval and the drag reduction rate in the pipeline is calculated to obtain the change of the drag reduction rate over time, and the influence of pump shear on polymer degradation is analyzed, so as to achieve the balance of pump efficiency improvement and working fluid characteristic stability, and at the same time quantitatively evaluate the parameter hazard degree k of the pump's hazard to the drag reducer. The present invention solves the problem that the current testing equipment only focuses on the influence of the working fluid on the pump efficiency, and does not monitor the changes of the working fluid after the pump shear effect.

[0009] The technical solution of the present invention is: an experimental method for testing the shear degradation law of a polymer solution, and the specific steps are as follows:

[0010] Building an experimental device, wherein the experimental device is a pipeline circulation system for measuring the effect of pump shear on the change of the measured working fluid characteristics;

[0011] Start the pump under test and run it at maximum power for a set time to preheat the device;

[0012] Discharge the preheated working fluid and inject the working fluid to be tested;

[0013] Adjust the power of the pump under test to the experimental working condition, measure the pressure difference of the working fluid under test before and after the test pipeline according to the set period, and obtain the drag reduction rate of the working fluid under test by calculation;

[0014] By adjusting the variables in the pipeline circulation system, the variation of drag reduction rate over time was obtained, and the influence of pump shear on polymer degradation was obtained.

[0015] A further technical solution of the present invention is: the operation of preheating the device is to first add a sufficient amount of clean water to the filling container of the experimental device before the first experiment of each round, and adjust the frequency converter to make the pump under test run at maximum power for half an hour to preheat the device, so as to avoid the influence of the temperature of the internal components of the pump on the results due to the large changes over time during the experiment.

[0016] A further technical solution of the present invention is: the measurement period of the measured working medium is set as:

[0017] When the working fluid to be measured is a flexible polymer, one point is sampled every minute in the first ten minutes after the start of the experiment; after ten minutes, a measurement is taken every five minutes; each measurement lasts 15 seconds, and the pressure difference at the start of the measurement is taken as the average of four measurements in the first ten minutes, and the pressure difference at the start of the measurement is taken as the average of five measurements after ten minutes. The sampling frequency is 1kHz;

[0018] When the working fluid to be measured is a rigid polymer, a measurement is performed every five minutes from the beginning to the end of the experiment; each measurement lasts 15 seconds, and the average of every five measurements is used as the pressure difference at the start of the measurement. The sampling frequency is 1 kHz.

[0019] A further technical solution of the present invention is: the calculation formula of the drag reduction rate is as follows:

[0020] DR=[(P0-P1)÷P0]×100%

[0021] Wherein, P0 is the average pressure difference obtained by multiple measurements of pure water working fluid, and P1 is the average pressure difference of the working fluid being measured, and both are measured at the same operating frequency.

[0022] A further technical solution of the present invention is: the variables are the measured pump speed, the test pipeline pressure, the action time, the measured working fluid type and the measured working fluid solution concentration.

[0023] An experimental device for testing the shear degradation law of a polymer solution comprises a filling container, a pump to be tested, a test pipeline and a flow meter which are sequentially connected in a closed loop through a pipeline. Ball valves are arranged on both sides of the pump to be tested, and the pressure in the pipeline is adjusted and cavitation is avoided by the ball valves, thereby expanding the testable range. The test pipeline is connected to a differential pressure transmitter to measure the pressure difference of the tested working fluid in the test pipeline.

[0024] A further technical solution of the present invention is that the filling container is a water tank with an opening at the top, in which a cooling pipe is arranged for maintaining a constant temperature of the working medium in the device.

[0025] A further technical solution of the present invention is: the test pipeline is a stainless steel pipe with a length of one meter, and pneumatic joint installation holes are respectively opened on it at 25 centimeters away from both ends. The pneumatic joints installed at both ends are respectively connected to the positive and negative electrodes of the differential pressure transmitter through hoses; a flow meter is connected downstream of the stainless steel pipe to display the flow rate in the pipeline in real time; the differential pressure transmitter and the flow meter are connected to the host computer for data collection and processing.

[0026] A further technical solution of the present invention is: the connecting pipeline of the experimental device is a metal wire hose, which is connected to each component through a trapezoidal groove flange; one end of the trapezoidal groove flange is a sleeve with an internal thread, which is installed at the inlet or outlet of each component through a thread; the other end is a slit circular tube, and the end of the metal wire hose is installed in the slit circular tube through a rubber sleeve and is clamped and fixed by a clamp.

[0027] An application of an experimental method for testing the shear degradation law of a polymer solution, wherein the experimental method for testing the shear degradation law of a polymer solution is used to evaluate the parameter hazard degree k of the pump's hazard to a drag reducer, and the drag reduction rate variation curve of a flexible / rigid working fluid under test is fitted with a quartic polynomial and a linear fit respectively, to obtain a fitting curve f(t)=b+a1t+a2t 2 +a3t 3 +a4t 4 or b+at, the absolute value of the derivative of the fitting curve at a certain point a is defined as the hazard k, that is, k = f'(t a )=a1+a2t+a3t 2 +a4t 3 or a, where a, a1, a2, a3, a4, and b are all constants whose values ​​depend on the specific fitting situation, and t represents the time;

[0028] When k is larger, it indicates that the pump is more harmful to the drag reducer. After completing the data processing, replace the new pump and repeat the above process.

[0029] Beneficial Effects

[0030] The beneficial effect of the present invention is that when the experimental device of the present invention is used to analyze the influence of pump shear on polymer degradation, it is only necessary to adjust the variables such as the speed of the tested pump, the test pipeline pressure, the action time, the type of the tested working fluid and the concentration of the tested working fluid solution. The variable adjustment is convenient and there is no need to replace the device. The test under different variables can be completed in the same device. The device of the present invention can not only obtain the influence of pump shear on polymer degradation through experiments, but also evaluate the parameter hazard degree k of the tested pump's hazard to the drag reducer. It also includes the following advantages:

[0031] 1. The present invention uses steel hoses as much as possible to replace stainless steel or PVC pipes, so that the flow conditions in the device can be intuitively seen, the construction and debugging are simple, and the construction cost is low.

[0032] 2. The present invention adopts quick connectors (trapezoidal groove flanges) and clamps to connect various components, which is convenient for installation and disassembly, and is conducive to the replacement of device components and working fluids according to different experimental purposes.

[0033] 3. Ball valves are installed at both upstream and downstream of the pump of the present invention, and the flow rate can be stabilized by adjusting the opening of the two valves and cavitation in the pipeline can be effectively avoided, thereby affecting the measurement accuracy and reducing the life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the connection of an experimental device for measuring the shear rate of a pump on a drag reducer in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of a trapezoidal groove flange connection in an embodiment of the present invention;

[0036] Figure 3 It is a schematic diagram of the structure of a trapezoidal groove flange in an embodiment of the present invention;

[0037] Figure 4 The operation flow of the experimental method in the embodiment of the present invention;

[0038] Figure 5 This is a repeatability test of the device at different operating frequencies in the embodiment of the present invention;

[0039] Figure 6 The drag reduction rate changes with time in the embodiment of the present invention; (a) 25hz500ppmPEO,

[0040] (b) 30hz200ppmPAM, (c) 30hz100ppmXG, (d) 30hz200ppmDG.

[0041] Explanation of the reference numerals: 1-centrifugal pump, 2-trapezoidal groove flange, 3-ball valve, 4-stainless steel pipe, 5-differential pressure transmitter, 6-flow meter, 7-water tank, 8-cooling pipe. DETAILED DESCRIPTION

[0042] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0043] Based on the problem that the current testing equipment only focuses on the influence of the working fluid on the pump efficiency, but does not monitor the changes of the working fluid after being sheared by the pump, the present invention provides an experimental method for testing the shear degradation law of polymer solution, and the specific steps are as follows:

[0044] Step 1: Build an experimental device, which is a pipeline circulation system for measuring the effect of pump shear on the change of the measured working fluid characteristics, including a filling container, a measured pump, a test pipeline, and a flow meter connected in a closed loop through a pipeline sequence. Ball valves are provided on both sides of the measured pump to adjust the pressure in the pipeline and avoid cavitation, thereby expanding the testable range; the test pipeline is connected to a differential pressure transmitter to measure the pressure difference of the measured working fluid in the test pipeline;

[0045] Specifically, the filling container is a water tank with an opening at the top, in which a cooling pipe is arranged for maintaining a constant temperature of the working medium in the device.

[0046] Specifically, the test pipeline is a stainless steel pipe with a length of one meter, on which pneumatic joint installation holes are opened 25 cm away from both ends. The pneumatic joints installed at both ends are respectively connected to the positive and negative poles of the differential pressure transmitter through hoses; a flow meter is connected downstream of the stainless steel pipe to display the flow rate in the pipeline in real time; the differential pressure transmitter and flow meter are connected to the host computer for data collection and processing.

[0047] Specifically, the connecting pipeline of the experimental device is a metal wire hose, which is connected to each component through a trapezoidal groove flange; one end of the trapezoidal groove flange is a sleeve with an internal thread, which is installed at the inlet or outlet of each component through a thread; the other end is a slit circular tube, and the end of the metal wire hose is installed in the slit circular tube through a rubber sleeve and is clamped and fixed by a clamp.

[0048] Step 2: Start the pump under test and run it at maximum power for a set time to preheat the device;

[0049] Specifically, the operation of preheating the device is as follows: before the first experiment of each round, first add a sufficient amount of clean water to the filling container of the experimental device, and adjust the frequency converter to make the pump under test run at maximum power for half an hour to preheat the device, so as to avoid the influence of the temperature of the internal components of the pump over time on the results during the experiment.

[0050] Step 3: discharge the preheated working fluid and inject the working fluid to be tested;

[0051] Step 4: Adjust the power of the pump under test to the experimental working condition, measure the pressure difference of the working fluid under test before and after the test pipeline according to the set period, and obtain the drag reduction rate of the working fluid under test by calculation;

[0052] Specifically, the measurement period of the measured working fluid is set as:

[0053] When the working fluid to be measured is a flexible polymer, one point is sampled every minute in the first ten minutes after the start of the experiment; after ten minutes, a measurement is taken every five minutes; each measurement lasts 15 seconds, and the pressure difference at the start of the measurement is taken as the average of four measurements in the first ten minutes, and the pressure difference at the start of the measurement is taken as the average of five measurements after ten minutes. The sampling frequency is 1kHz;

[0054] When the working fluid to be measured is a rigid polymer, a measurement is performed every five minutes from the beginning to the end of the experiment; each measurement lasts 15 seconds, and the average of every five measurements is used as the pressure difference at the start of the measurement. The sampling frequency is 1 kHz.

[0055] Specifically, the calculation formula of the drag reduction rate is as follows:

[0056] DR=[(P0-P1)÷P0]×100%

[0057] Wherein, P0 is the average pressure difference obtained by multiple measurements of pure water working fluid, and P1 is the average pressure difference of the working fluid being measured, and both are measured at the same operating frequency.

[0058] Step 5: Adjust the variables in the pipeline circulation system to obtain the change of drag reduction rate over time and the influence of pump shear on polymer degradation. The variables are the measured pump speed, test pipeline pressure, action time, measured working fluid type and measured working fluid solution concentration.

[0059] The present invention discloses an experimental method for testing the shear degradation law of a polymer solution. The experimental method for testing the shear degradation law of a polymer solution is used to evaluate the parameter hazard degree k of the pump's hazard to a drag reducer. The drag reduction rate of a flexible / rigid working fluid under test is fitted with a quartic polynomial and a linear fit over time to obtain a fitting curve f(t)=b+a1t+a2t 2 +a3t 3 +a4t 4 or b+at, the absolute value of the derivative of the fitting curve at a certain point a is defined as the hazard k, that is, k = f'(t a )=a1+a2t+a3t 2 +a4t 3 or a, where a, a1, a2, a3, a4, and b are all constants whose values ​​depend on the specific fitting situation, and t represents the time;

[0060] When k is larger, it indicates that the pump is more harmful to the drag reducer. After completing the data processing, replace the new pump and repeat the above process.

[0061] The above technical solution is further described below in conjunction with the accompanying drawings:

[0062] Reference Figure 1 As shown, this embodiment is an experimental device for testing the shear degradation law of a polymer solution, comprising a water tank, a ball valve, a centrifugal pump, a ball valve, a stainless steel pipe, and a flow meter connected in sequence along a pipeline;

[0063] The water tank is a common open structure, serving as the addition port for the working fluid used in the experiment. A cooling pipe is provided inside the water tank to maintain a constant temperature in the device. The water tank is directly placed at the water tank position and has no fixed connection with the experimental device.

[0064] The centrifugal pump is used to drive the liquid to circulate in the device and serve as a shear source for the drag reducer. Its model and speed are experimental variables and it is connected to the steel hose in the device through a threaded pipe. The centrifugal pump is connected to a frequency converter, which is used to adjust the pump speed to change the shear strength and is connected to the centrifugal pump.

[0065] The flow meter is used to accurately measure the circulation speed of the working medium in the device, and is connected to the steel wire hose in the device through a clamp and a trapezoidal groove flange; the trapezoidal groove flange, specification DN50, is used for connecting and sealing the pump inlet and outlet and the pipeline.

[0066] The stainless steel pipe is used to measure the drag reduction rate of the working fluid. It is one meter long and is connected to the steel wire hose in the device through a clamp. The circumference of the stainless steel pipe is connected to the differential pressure transmitter through a pneumatic joint. The differential pressure transmitter is used to measure the pressure drop at the stainless steel pipe and is connected to the pneumatic joint on the stainless steel pipe through a hose.

[0067] The ball valve is used to adjust the pressure in the pipe and avoid cavitation, expand the testable range, and is connected to the steel wire hose in the device through a quick connector.

[0068] Reference Figure 2 As shown, the inlet and outlet of the centrifugal pump 1 are connected to the pipeline through a trapezoidal groove flange, and the ball valve 3 is downstream of the outlet. A steel hose is connected to the ball valve 3, and the solution flows through the steel hose into the stainless steel pipe section 4. The stainless steel pipe section is 1 meter long, and small holes are opened 25 cm away from both ends to install pneumatic joints. Two hoses are led out from the two joints and connected to the positive and negative poles of the differential pressure transmitter 5. The flow meter 6 is connected to the rear of the stainless steel pipe section 4 to display the flow rate in the pipeline in real time. The differential pressure transmitter 5 and the flow meter 6 are connected to the computer for data acquisition and processing. The open water tank 7 is downstream of the flow meter, and a cooling coil 8 is placed in the water tank, in which the cooling water used forms another loop. The ball valve is connected to the pump inlet downstream of the water tank to form a loop. Figure 1 The black straight line in the middle represents the steel hose. In order to facilitate the disassembly and assembly of the experimental device and reduce the loss of the solution caused by the joint structure, the connecting components are designed as follows Figure 3 As shown, the steel hose is connected to the other parts of the experimental device through Figure 3 The components shown are connected. Figure 3 The left end of the component is a DN50 internal threaded hole, which is used to connect various components such as stainless steel pipes and water tanks. The right end is a 67mm inner diameter slotted round tube, which can be inserted into a steel hose after a 3mm thick rubber sleeve is placed in it. It can be sealed after being clamped with a clamp. The arrow indicates the direction of solution flow during the experiment.

[0069] The principle of the experimental device is as follows: the centrifugal pump 1 provides power for the entire circulation system. When the pump is started, the pump shaft drives the impeller to rotate at high speed. Under the action of rotation, the liquid moves radially from the center of the impeller to the periphery. The liquid gains energy in the process of flowing through the impeller, the static pressure energy increases, and the flow rate increases. When the liquid leaves the impeller and enters the pump casing, it slows down due to the gradual expansion of the flow channel in the casing, and part of the kinetic energy is converted into static pressure energy, and finally flows into the discharge pipe tangentially. The liquid in the pipeline flows through the pump and the stainless steel measuring section and then flows into the water tank, and then re-enters the pump after being cooled by the cooling pipe in the water tank. The cooling pipe is used to control the temperature of the liquid in the pipe to eliminate the influence of temperature changes on the change law of polymer with running time. The measurement of polymer degradation consists of a stainless steel pipe section, a differential pressure transmitter and a flow meter. The drag reduction rate reflects the drag reduction performance of the polymer, with time, polymer type and solution concentration as variables. During the experiment, the pump is kept running stably after the pipeline is fully circulated. The pressure differential transmitter data is collected at the same time interval and the drag reduction rate in the pipeline is calculated to obtain the change of drag reduction rate over time, and analyze the influence of pump shear on polymer degradation.

[0070] Reference Figure 4 As shown in the figure, the specific operation process of the experiment is that before the first experiment of each round, 54L of clean water is first added to the water tank, and the frequency converter is adjusted to make the pump run at maximum power for half an hour to preheat the device to avoid the influence of the temperature change of the internal parts of the pump over time during the experiment. Then the frequency converter is adjusted to stop the centrifugal pump, and the water tank is emptied with a water pump and the prepared polymer solution is added. The frequency converter is re-adjusted to the experimental working condition to start measuring the pressure difference before and after the stainless steel experimental section pipeline. Each group of experiments is measured for half an hour. According to the different properties of polymers, the specific measurement method is as follows: for flexible polymers, because they are more affected by shear, one point is sampled every minute in the first ten minutes, and a measurement is performed every five minutes after ten minutes; for rigid polymers, the measurement points in the early stage of the experiment are no longer encrypted, and a measurement is performed every five minutes from the beginning to the end of the experiment. Each measurement time is 15s, and every 5 measurements (4 measurements in the first ten minutes of flexible polymers) are averaged as the pressure difference at the start of the measurement, and the sampling frequency is 1kHz. The obtained pressure difference P1 and the average pressure difference P0 obtained by three measurements of pure water working fluid at the same working frequency of the pump are calculated by DR = [(P0-P1)÷P0] × 100% to obtain the drag reduction rate of the solution. The drag reduction rate curves of the flexible and rigid polymers over time are fitted by the fourth-order polynomial and linear fitting, that is, the curve f(t) = b+a1t+a2t 2 +a3t 3 +a4t 4 or b+at, the absolute value of the derivative of the fitting curve at a certain point a is defined as the hazard k, that is, k = f'(t a )=a1+a2t+a3t 2 +a4t 3Or a, where a, a1, a2, a3, a4, and b are all constants whose values ​​depend on the specific fitting situation. t represents the time. The larger the k, the greater the harm of the pump to the drag reducer. After completing the data processing, replace the new experimental pump by disassembling the trapezoidal groove flange and repeat the above process.

[0071] In this experiment, a bucket with a volume of 18L was used to prepare the solution. First, three portions of polymer powder were weighed according to the calculated results. They were slowly poured into three buckets filled with water while being stirred at a uniform speed by a stirrer. The stirring time was controlled to be the same. After the preparation was completed, the solution was poured into an open water tank.

[0072] Test results:

[0073] The experiment was conducted using the centrifugal pump SGR10-15-60 as an example. The first step is to verify the repeatability of the device. In this part, the pump operating frequency was adjusted to 25Hz, 30Hz and 35Hz respectively, and the experiment was repeated four times under pure water conditions. The first measurement at each frequency was preheating. The results are shown in the figure. Figure 5 As shown in the figure, it can be seen that except for the first measurement of each frequency, the pressure differences obtained in the other three experiments are basically the same. Therefore, the experimental device can operate stably after preheating.

[0074] The experiment was conducted by adjusting the pump operating frequency through a frequency converter, and four polymers, polyethylene oxide (PEO), polyacrylamide (PAM), xanthan gum (XG) and diutan gum (DG), were used to prepare solutions of different concentrations, of which the first two were flexible polymers and the latter two were rigid polymers. Figure 6 shown.

[0075] Fitting the above figures separately yields: a:38.51-10.30t+1.13t 2 -0.05t 3 +0.00113t 4 , b:f(t)=42.41-6.00t+0.68t 2 -0.04t 3 +0.00116t 4 , c:f(t)=13.16-0.37t, d:f(t)=23.40-0.062t. Taking time 0 as an example, the criticality of the four working conditions are k=10.30, 6.00, 0.37, 0.062 respectively.

[0076] It can be seen that Figure 6 The hazard degree k in (c) and (d) is ≈ 0, that is, the shear resistance of rigid polymers is much stronger than that of flexible polymers. Figure 6 The general rule of the hazard degree of (a) and (b) is k a >k bThat is, the shear resistance of PEO in flexible polymers is weaker than that of PAM, so it is not suitable for drag reduction in pipeline transportation. It is suitable for fire hose drag reduction and other fields that do not require long-term shearing. Xanthan gum and dimethoate are not easily damaged by pump shearing and can effectively reduce drag at low concentrations, so they can be used for long-distance pipeline transportation.

[0077] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. An experimental method for testing the shear degradation law of polymer solutions, characterized in that The specific steps are as follows: Building an experimental device, wherein the experimental device is a pipeline circulation system for measuring the effect of pump shear on the change of the measured working fluid characteristics; Start the pump under test and run it at maximum power for a set time to preheat the device; Discharge the preheated working fluid and inject the working fluid to be tested; Adjust the power of the pump under test to the experimental working condition, measure the pressure difference of the working fluid under test before and after the test pipeline according to the set period, and obtain the drag reduction rate of the working fluid under test by calculation; By adjusting the variables in the pipeline circulation system, the variation of drag reduction rate over time was obtained, and the influence of pump shear on polymer degradation was obtained.

2. The experimental method for testing the shear degradation law of a polymer solution according to claim 1, characterized in that: The operation of preheating the device is as follows: before the first experiment of each round, first add a sufficient amount of clean water to the filling container of the experimental device, and adjust the frequency converter to make the pump under test run at maximum power for half an hour to preheat the device, so as to avoid the influence of the temperature of the internal components of the pump on the results due to large changes over time during the experiment.

3. The experimental method for testing the shear degradation law of a polymer solution according to claim 1, characterized in that: The measurement cycle of the measured working fluid is set as: When the working fluid to be measured is a flexible polymer, one point is sampled every minute in the first ten minutes after the start of the experiment; after ten minutes, a measurement is taken every five minutes; each measurement lasts 15 seconds, and the pressure difference at the start of the measurement is taken as the average of four measurements in the first ten minutes, and the pressure difference at the start of the measurement is taken as the average of five measurements after ten minutes. The sampling frequency is 1kHz; When the working fluid to be measured is a rigid polymer, a measurement is performed every five minutes from the beginning to the end of the experiment; each measurement lasts 15 seconds, and the average of every five measurements is used as the pressure difference at the start of the measurement. The sampling frequency is 1 kHz.

4. The experimental method for testing the shear degradation law of a polymer solution according to claim 1, characterized in that: The calculation formula of the drag reduction rate is as follows: DR=[(P0-P1)÷P0]×100% Wherein, P0 is the average pressure difference obtained by multiple measurements of pure water working fluid, and P1 is the average pressure difference of the working fluid being measured, and both are measured at the same operating frequency.

5. The experimental method for testing the shear degradation law of a polymer solution according to claim 1, characterized in that: The variables are the measured pump speed, the test pipeline pressure, the action time, the measured working fluid type and the measured working fluid solution concentration.

6. An experimental device for testing the shear degradation law of a polymer solution, used to implement the experimental method according to any one of claims 1 to 5; characterized in that: It includes a filling container, a pump to be tested, a test pipeline, and a flow meter which are connected in a closed loop through a pipeline sequence. Ball valves are provided on both sides of the pump to be tested. The pressure in the pipeline is adjusted and cavitation is avoided through the ball valves, thereby expanding the testable range. The test pipeline is connected to a differential pressure transmitter to measure the pressure difference of the tested working fluid in the test pipeline.

7. An experimental device for testing the shear degradation law of a polymer solution according to claim 6, characterized in that: The filling container is a water tank with an opening at the top, in which a cooling pipe is arranged for keeping the working medium temperature in the device constant.

8. An experimental device for testing the shear degradation law of a polymer solution according to claim 6, characterized in that: The test pipeline is a stainless steel pipe with a length of one meter. Pneumatic joint installation holes are opened on it 25 cm away from both ends. The pneumatic joints installed at both ends are connected to the positive and negative poles of the differential pressure transmitter through hoses respectively; a flow meter is connected downstream of the stainless steel pipe to display the flow rate in the pipeline in real time; the differential pressure transmitter and flow meter are connected to the host computer for data collection and processing.

9. The experimental device for testing the shear degradation law of polymer solution according to claim 6, characterized in that: The connecting pipeline of the experimental device is a metal wire hose, which is connected to each component through a trapezoidal groove flange; one end of the trapezoidal groove flange is a sleeve with an internal thread, which is installed at the inlet or outlet of each component through threads; the other end is a slit circular tube, and the end of the metal wire hose is installed in the slit circular tube through a rubber sleeve and is clamped and fixed by a clamp.

10. Application of an experimental method for testing the shear degradation law of a polymer solution, characterized in that: The experimental method for testing the shear degradation law of polymer solution is used to evaluate the parameter hazard k of the pump to the drag reducer. The drag reduction rate of the flexible / rigid working fluid under test is fitted with the time curve by the fourth-order polynomial and linear fitting, respectively, to obtain the fitting curve f(t)=b+a1t+a2t 2 +a3t 3 +a4t 4 or b+at, the absolute value of the derivative of the fitting curve at a certain point a is defined as the hazard k, that is, k = f'(t a )=a1+a2t+a3t 2 +a4t 3 or a, where a, a1, a2, a3, a4, b are all constants, and t represents the time; When k is larger, it indicates that the pump is more harmful to the drag reducer. After completing the data processing, replace the new pump and repeat the above process.

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