A device and method for testing multi-parameter drag reduction effect of pipeline with small aspect ratio

Abstract

The present invention provides a device and method for testing the multi-parameter drag reduction effect of a small aspect ratio pipeline, which relates to the field of drag reduction testing technology. The device comprises a water tank, an annular test pipeline connected to the water tank at both ends, and a pipeline to be tested; a temperature control component for adjusting the temperature of the liquid in the water tank is arranged in the water tank; the pipeline to be tested is detachably arranged on the annular test pipeline, and pressure sensors are arranged at both ends of the annular test pipeline; an injection device is also arranged on the annular test pipeline, and the injection device is arranged in front of the pipeline to be tested, including a first injection device for injecting an acid solution into the annular test pipeline, a second injection device for injecting an alkaline solution into the annular test pipeline, and a third injection device for injecting gas into the annular test pipeline. The present invention can realize the integration of the preparation of a polymer brush drag reduction coating in a pipeline with a small aspect ratio and the drag reduction effect test.

Description

Technical Field

[0001] The invention relates to the technical field of drag reduction testing, and in particular to a device and method for testing multi-parameter drag reduction effects of a small aspect ratio pipeline. Background Art

[0002] The drag reduction problem at the interface between solid and fluid has always been a hot topic in current research. In the fields of long-distance pipelines, industrial process pipelines, and circulating cooling pipelines, due to the interaction between the inner wall and the liquid inside the pipeline, a turbulent boundary layer will be generated on the surface, thereby generating friction resistance and pressure pulsation, forming fluid resistance. The increase in resistance will lead to a decrease in the flow velocity of the internal liquid, an increase in energy consumption, and a certain amount of noise and vibration, reducing the stability of the transportation system. By preparing a drag-reducing coating on the inner surface of the pipeline, the fluid resistance can be effectively reduced and energy consumption can be reduced.

[0003] The drag reduction effect of the drag reduction coating will change with the operating conditions. For example, under different pH values, temperatures, salt concentrations, Reynolds numbers and other conditions, the drag reduction rate of the coating will change accordingly. Therefore, it is necessary to test and study the changes in the drag reduction effect under different parameters.

[0004] Some large-scale water circulation cooling systems use multiple thin tubes in key locations to ensure sufficient contact area for adequate heat exchange. The aspect ratio of such thin pipes is very small. How to prepare polymer brush drag reduction coatings on the inner wall of small aspect ratio pipes and test the drag reduction effect is a major difficulty. Limited by the small inner diameter of the pipe, it is difficult to use spraying, photo-initiated polymerization, and coating with a solution containing an initiator to coat the inner wall of a small aspect ratio pipe. Redox initiation is more complicated and requires two or more initiators. Therefore, the best way is to use a thermal initiation preparation method. The preparation of polymer brushes adopts the grafting-from method, which can obtain polymer brush coatings with higher chain lengths and higher grafting densities. This method requires the substrate to be placed in a reacting solution and in contact with the solution to react until the polymer is grafted to the surface. However, if the entire pipeline is immersed in a liquid pool for reaction, it will result in a huge consumption of expensive zwitterion precursor solution, and the liquid pool needs to be customized according to different lengths and pipe diameters; and if the pipeline is filled with zwitterion precursor solution and both ends are sealed for reaction, it is difficult to achieve quantitative adjustment of parameters such as temperature and pH value during the reaction process, and there is a problem of insufficient solution dosage, resulting in the inability to fully prepare the required amount of coating. Summary of the invention

[0005] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a multi-parameter drag reduction effect testing device and method for a small aspect ratio pipeline, so as to integrate the preparation of a polymer brush drag reduction coating in a small aspect ratio pipeline with the drag reduction effect testing, thereby improving the testing efficiency.

[0006] In order to achieve the above-mentioned purpose, according to some embodiments, a first aspect of the present invention provides a multi-parameter drag reduction effect testing device for a small aspect ratio pipeline, comprising: a water tank, an annular test pipeline connected to the water tank at both ends, and a pipeline to be tested; a temperature control component for adjusting the temperature of the liquid in the water tank is arranged in the water tank; the pipeline to be tested is detachably arranged on the annular test pipeline, and pressure sensors are arranged at both ends of the annular test pipeline; an injection device is also arranged on the annular test pipeline, and the injection device is arranged in front of the pipeline to be tested, comprising a first injection device for injecting an acidic solution into the annular test pipeline, a second injection device for injecting an alkaline solution into the annular test pipeline, and a third injection device for injecting gas into the annular test pipeline.

[0007] The second aspect of the present invention, based on the small aspect ratio pipeline multi-parameter drag reduction effect testing device provided in the first aspect, further provides a small aspect ratio pipeline multi-parameter drag reduction effect testing method, comprising:

[0008] Select two pipes to be tested with the same size, and prepare a drag-reducing coating on the inner wall of one of the pipes to be tested;

[0009] Different test parameters were set to test the pressure drops at both ends of the test pipe with and without drag-reducing coating when the liquid flowed through the test pipe, and the corresponding drag reduction rate was calculated.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The present invention provides a device and method for testing the multi-parameter drag reduction effect of a small aspect ratio pipeline. An injection device is arranged on the annular test pipeline. On the one hand, it can realize the on-demand adjustment of the pH value, air introduction rate, etc. during the test to realize the multi-parameter drag reduction effect test. On the other hand, it can also realize the integration of the preparation of the polymer brush drag reduction coating in the small aspect ratio pipeline and the drag reduction effect test. Through the cooperation of the temperature control component in the water tank and the injection device on the annular test pipeline, the efficient preparation of the polymer brush drag reduction coating in the small aspect ratio pipeline with controllable reaction conditions is realized, and the problem of the difficulty in preparing the polymer brush drag reduction coating in the small aspect ratio pipeline is solved. In addition, considering that the flow field stability and uniformity of the liquid in the annular test pipeline will change when it flows through the bend, the flow velocity changes, and is injected by the injection device, thereby affecting the test accuracy and stability, the present invention arranges a contraction pipe section and a buffer pipe section in front of the pipeline to be tested to stabilize the flow field flowing into the pipeline to be tested, so as to ensure the stability and repeatability of the test results.

[0012] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0014] Figure 1 A schematic diagram of a multi-parameter drag reduction effect test device for a small aspect ratio pipeline provided in Example 1 of the present invention;

[0015] Figure 2 This is a schematic diagram of the changes of the polymer brush drag reduction coating before and after being affected;

[0016] Figure 3 This is a logical diagram of temperature, pH value, and flow rate control in the drag reduction effect test.

[0017] Among them, 1. water tank; 2. annular test pipeline; 3. centrifugal pump; 4. elbow; 5. electric control throttle valve; 6. three-way joint; 7. injection device; 8. contraction pipe section; 9. equal diameter joint; 10. buffer pipe section; 11. ferrule three-way joint; 12. pressure sensor; 13. pipeline to be tested; 14. temperature sensor; 15. connecting line; 16. flow sensor; 17. pH sensor; 18. salinity sensor; 19. computer; 20. driver; 21. one-way valve; 22. temperature control component; 23. hose section. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] Embodiment 1

[0020] Embodiment 1 of the present invention, as Figure 1-Figure 3 As shown, a multi-parameter drag reduction effect test device for a pipeline with a small aspect ratio is provided, comprising: a water tank 1, an annular test pipeline 2 connected to the water tank 1 at both ends, and a pipeline to be tested 13. A temperature control component 22 for adjusting the temperature of the liquid in the water tank is arranged in the water tank 1; the pipeline to be tested 13 is detachably arranged on the annular test pipeline 2, and a pressure sensor 12 is arranged at both ends of the annular test pipeline 13; an injection device 7 is also arranged on the annular test pipeline, and the injection device 7 is arranged in front of the pipeline to be tested 13, including a first injection device for injecting an acid solution into the annular test pipeline, a second injection device for injecting an alkaline solution into the annular test pipeline, and a third injection device for injecting gas into the annular test pipeline.

[0021] The test device provided in this embodiment realizes the test of drag reduction effect based on the pressure difference method, that is, by measuring the pressure drop of the pipeline to be tested with and without the drag reduction coating, and comparing the difference between the two pressures to obtain the drag reduction rate. The pressure sensor 12 is connected to both ends of the pipeline to be tested through the ferrule three-way connector 11 to obtain the pressure drop of the liquid after it flows through the pipeline to be tested. The difference between the measurement data of the two pressure sensors before and after is the pressure drop of the pipeline to be tested, which characterizes the resistance inside the pipeline to be tested, and the drag reduction rate of the drag reduction coating under the corresponding working conditions is calculated accordingly.

[0022] In some embodiments, the overall annular test pipeline uses a standard PVC six-point pipe with a total length of about 10m, the length of the pipe to be tested is 1m, and the water tank can store up to 40kg of water.

[0023] The annular test pipeline is also provided with sensors for monitoring the state of the liquid in the annular test pipeline, including a temperature sensor 14, a flow sensor 16, a pH sensor 17 and a salinity sensor 18, which are respectively used to monitor the temperature, flow, pH value and salinity of the liquid in the annular test pipeline. The pressure sensor 12, the temperature sensor 14, the pH sensor 17 and the salinity sensor 18 are all corrosion-resistant sensors, which are respectively connected to the annular test pipeline through a three-way joint, and the three-way joint is threadedly connected to the annular test pipeline. The connection is sealed with a sealing ring and a raw tape to prevent leakage. The flow sensor 16 adopts an ultrasonic flow sensor, which is fixed to the outer wall of the annular test pipeline to obtain the liquid flow data in the annular test pipeline.

[0024] The water outlet and water inlet of the water tank 1 are both connected to the annular test pipeline through threads to achieve water storage, water delivery and water return. In some embodiments, the water tank is further connected to a tap water pipe and a sewer pipe to facilitate the addition of water and the discharge of wastewater or waste liquid.

[0025] The main body of the annular test pipeline 2 is a six-point pipe made of PVC material, which is connected to the water tank at both ends, and is connected to the pipeline to be tested 13 and various components such as the injection device 7 and the sensor through connectors to form a circulation system of the test device. The PVC pipe is not affected by corrosion caused by changes in pH and salinity, and can provide sufficient support and facilitate the installation of connectors, thereby achieving stable installation of components such as the injection device and the sensor.

[0026] A centrifugal pump 3 and an electrically controlled throttle valve 5 are also provided on the annular test pipeline 2 to change the flow rate of the liquid in the annular test pipeline. Among them, the centrifugal pump 3 is a corrosion-resistant centrifugal pump to avoid corrosion caused by changes in the pH and salinity of the liquid. The centrifugal pump 3 is arranged at the water outlet of the water tank 1 to provide power for water circulation. The speed of the centrifugal pump directly determines the flow rate of the liquid in the pipeline and can be controlled by a frequency regulator. The frequency regulator is connected to the centrifugal pump and cooperates with the flow sensor 16 to realize control. The frequency regulator receives the flow value monitored by the flow sensor and determines whether the flow value is equal to the set value. When the flow value exceeds or is lower than the set value, the frequency of the centrifugal pump input voltage is adjusted by the PID algorithm to change its speed, thereby changing the flow rate and Reynolds number of the liquid in the pipeline. In this embodiment, the flow rate adjustment range of the liquid in the pipeline is 0m / s-15m / s.

[0027] The electric control throttle valve 5 is arranged after the centrifugal pump 3 to achieve further fine adjustment of the flow rate of the liquid in the pipeline. A one-way valve 21 is further arranged on the annular test pipeline to prevent liquid reflux and ensure a single flow direction.

[0028] In this embodiment, three groups of injection devices are provided, including a first injection device for injecting an acidic solution into the annular test pipeline, a second injection device for injecting an alkaline solution into the annular test pipeline, and a third injection device for injecting gas into the annular test pipeline. The injection device is connected by a syringe and a syringe pump, wherein the syringe is connected to the annular test pipeline through a three-way connector 6, and an electric switch valve is also provided on the syringe to prevent the liquid in the annular test pipeline from mixing with the liquid or gas in the syringe in a non-operating state. The syringe adopts a 1.5L large-scale filler to ensure that the content of the internal liquid or gas is sufficient to meet the test requirements; the syringe pump is connected to the syringe to control the rate of entry of the liquid or gas in the syringe into the annular test pipeline.

[0029] The drag reduction effect of the drag reduction coating will be affected by the pH value of the liquid, so it is of great significance to study the effect of the pH value on the drag reduction effect. In this embodiment, the pH value of the liquid in the annular test pipeline is adjusted by adding acid and alkali. The first injection device is filled with hydrochloric acid, and the second injection device is filled with a high concentration of sodium hydroxide solution. The first injection device and the second injection device are used in conjunction with the pH sensor 17. When the pH value monitored by the pH sensor is lower than the set value, the second injection device is operated to pass an alkaline solution into the annular test pipeline to increase the pH value; when the pH value monitored by the pH sensor is higher than the set value, the first injection device is operated to pass an acidic solution into the annular test pipeline to lower the pH value. The adjustment range of the pH value in this embodiment is 3-11. The third injection device is filled with air to simulate non-ideal working conditions when there are bubbles in the liquid, so that the drag reduction rate of drag reduction technologies such as drag reduction coatings at different ventilation rates can be studied.

[0030] The test device in this embodiment also includes a control system, which includes a computer 19 and a driver 20 connected to the computer 19. The computer 19 is connected to the pressure sensor 12, the temperature sensor 14, the flow sensor 16, the pH sensor 17 and the salinity sensor 18 through a connecting line 15, and is used to receive the parameter data collected by each sensor; at the same time, the computer is also used to obtain the set value (preset parameter) corresponding to each parameter data through human-computer interaction, so as to issue a control instruction to control the action of the temperature control component 22, the centrifugal pump 3, the electric control throttle valve 5, and the injection device 7, and adjust the parameters of the liquid in the annular test pipeline to meet the test requirements. The driver 20 is connected to the computer 19 and is connected to the temperature control component 22, the centrifugal pump 3, the electric control throttle valve 5, and the injection device 7 for communication, so as to realize the control of each component.

[0031] The drag reduction effect of the drag reduction coating is also affected by temperature. Therefore, in this embodiment, the temperature of the liquid is adjusted by a temperature control component 22 arranged in the water tank. The temperature control component 22 includes a refrigeration element and a heating element. The temperature control component 22 is connected to the temperature sensor 14 and the control system. The temperature sensor 14 collects the temperature information of the liquid in the annular test pipeline and feeds it back to the control system. The control system controls the operating state of the temperature control component 22 according to the received temperature information, thereby controlling the temperature of the liquid in the annular test pipeline. The temperature controllable range is -20℃-80℃.

[0032] The drag reduction effect of the drag reduction coating is also affected by salinity. In this embodiment, the salinity can be changed by directly adding salt (such as sodium chloride) and fresh water into the water tank, and the salinity of the liquid is monitored in real time by a salinity sensor.

[0033] The pipeline 13 to be tested is connected to the annular test pipeline through the ferrule tee joints 11 at both ends. The interface of the ferrule tee joint is connected to the annular test pipeline at both ends through a ferrule joint. The ferrule joint has a variety of sizes with an outer diameter of 6mm-25mm. The ferrule joints with different outer diameters can be selected according to actual needs to meet the test of pipelines with different diameters.

[0034] The annular test pipeline is connected by a PVC pipe and an elbow 4 to form an annular circulation structure. A contraction pipe section 8 and a buffer pipe section 10 are provided on the annular test pipeline in front of the pipeline to be tested, and the contraction pipe section, the buffer pipe section and the pipeline to be tested are coaxially arranged. Considering that the liquid in the annular test pipeline flows through the bend, the flow velocity changes, and is injected by the injection device, the flow field stability and uniformity will change, thereby affecting the test accuracy and stability. In this embodiment, a certain length of contraction pipe section 8 and buffer pipe section 10 are additionally provided in front of the pipeline to be tested 13, so that the flow field of the liquid flowing into the pipeline to be tested 13 remains stable. The contraction pipe section 8 is a truncated cone-shaped structure as a whole, which is arranged after the elbow 4 of the annular test pipeline and after the connection position between the injection device 7 and the annular test pipeline. The end with a large inner diameter of the contraction pipe section is connected to the elbow 4 of the annular test pipeline, and the end with a small inner diameter is connected to the equal-diameter joint 9, which can stabilize the instability of the flow field caused by factors such as bends, flow velocity changes, and injections; one end of the buffer pipe section 10 is connected to the contraction pipe section through the equal-diameter joint 9, and the other end is connected to the pipeline to be tested 13 through the ferrule three-way joint 11, and the inner diameter and outer diameter of the buffer pipe section are consistent with the inner diameter and outer diameter of the pipeline to be tested, so as to stabilize the instability of the flow field caused by the change in diameter of the contraction pipe section.

[0035] In some embodiments, the optimal lengths of the contraction tube section and the buffer tube section are obtained through simulation, so as to ensure that the length is as short as possible while the flow field flowing into the pipeline to be tested and the sensor is the most stable. According to simulation research, when the contraction tube section 8 and the buffer tube section 10 are set, and the length ratio of the contraction tube section 8 and the buffer tube section 10 is 3:1, the velocity uniformity of the flow field is the highest, which is conducive to the stability of the test and the uniform preparation of the coating when the polymer brush drag reduction coating is prepared on the inner wall of the pipeline to be tested. In this embodiment, the length of the contraction tube section is designed to be 30 cm, and the length of the buffer tube section is designed to be 10 cm.

[0036] In addition, the contraction pipe section and the buffer pipe section are designed at the same time. Under the same conditions (consistent total length and boundary conditions), the stability is further improved compared with the solution of using a reducer for reducing the diameter and only setting up one buffer pipe section for buffering. The principle is that the contraction pipe section can promote the adjustment of fluid flow and streamline rearrangement, help eliminate the irregularity of upstream flow conditions, reduce the formation of turbulence and eddy currents, and make the fluid in a relatively stable flow state before entering the buffer pipe section, thereby further reducing the interference with the pipeline to be tested, and can more accurately measure the drag reduction effect of the polymer brush coating, ensuring the accuracy and reliability of the test.

[0037] In some embodiments, the annular test pipeline is parallel to the position of the pipeline to be tested and further has a hose section 23, which is convenient for adjusting the distance between the two ferrule tee joints 11, so that pipelines of different lengths can be connected to the pipelines to be tested. In this embodiment, the length of the pipeline to be tested ranges from 0.2m to 5m. The hose section 23 can be used to cooperate with the design of the pipeline to be tested 13 and the shrink pipe section 8 and the buffer pipe section 10, so as to realize the preparation of the internal drag reduction coating of the pipeline to be tested under different lengths and different pipe diameters and the test of the drag reduction rate of the pipeline to be tested, and adjust the length of the shrink pipe section 8 and the buffer pipe section 10 according to the simulation results to ensure the uniformity of the liquid flow field in the test device.

[0038] Embodiment 2

[0039] This embodiment is based on a multi-parameter drag reduction effect test device for a small aspect ratio pipeline provided in the first embodiment, and further provides a multi-parameter drag reduction effect test method for a small aspect ratio pipeline, including:

[0040] Select two pipes to be tested with the same size, and prepare a drag-reducing coating on the inner wall of one of the pipes to be tested;

[0041] Different test parameters were set to test the pressure drops at both ends of the test pipe with and without drag-reducing coating when the liquid flowed through the test pipe, and the corresponding drag reduction rate was calculated.

[0042] Due to the influence of wall friction and other factors, the fluid will generate pressure loss along the way after flowing through the pipeline, that is, pressure drop. The greater the pressure drop, the greater the fluid resistance. Based on the test device provided in Example 1, when testing the drag reduction effect, after setting parameters such as temperature, pH value, flow rate, etc., the pressure drop P1 and P2 of the fluid flowing through the pipeline to be tested before and after the drag reduction technology is used are respectively collected through the pressure sensor, and then the drag reduction rate of the drag reduction technology is calculated by the following formula:

[0043] Dr = (P1-P2) / P1×100%;

[0044] Where Dr represents the drag reduction rate.

[0045] The test device provided in the first embodiment can realize the test of the drag reduction rate after adding drag reducing agent or preparing drag reducing coating in the pipeline to be tested, and can also realize the integration of preparation and drag reduction effect test of polymer brush drag reducing coating in pipeline with small aspect ratio. The drag reduction effect of polymer brush drag reducing coating will be affected by many factors such as salinity, temperature, pH value and Reynolds number, such as Figure 2 As shown, when the salinity, temperature, pH value and / or Reynolds number change, the morphology of the polymer brush will change, resulting in a change in the drag reduction effect.

[0046] The following is a detailed description of the preparation of a zwitterionic polymer brush drag reduction coating in a pipeline to be tested and the drag reduction test.

[0047] First, a pipe to be tested is selected, and an intermediate layer with grafting sites is prepared on the inner wall of the pipe to be tested. Subsequently, according to the diameter of the selected pipe to be tested, the corresponding size of the shrink pipe section 8, the equal diameter joint 9, the buffer pipe section 10, and the ferrule three-way joint 11 are selected to install the pipe to be tested 13 on the annular test pipeline. The acid, alkaline solution and air are respectively loaded into the injection device 7; the prepared precursor solution of the polymer brush is added into the water tank 1. After the solution is filled, the temperature and pH value required for the reaction are set in the computer 19, the liquid flow rate in the pipe is set to 0.2m / s, the air introduction rate of the third injection device is set to 10μL / min, the device is started, and the centrifugal pump 3 is operated to circulate the precursor solution in the device. In an aerobic environment and at a specific pH value and temperature, the monomer molecules in the precursor solution begin to polymerize from the grafting sites on the surface of the pipe, thereby growing into a polymer brush drag reduction coating covering the inner surface of the pipe to be tested, while other untreated parts of the pipe do not have grafting sites and no polymer brushes will grow.

[0048] After the chemical reaction of coating preparation is completed, the waste liquid is discharged and cleaned. After the waste liquid is discharged, clean water is introduced into the water tank 1, and the centrifugal pump is started and operated for a period of time until the pH sensor 17 reads about 7, and the pipeline cleaning is considered to be completed. Then the cleaning water is discharged and further drag reduction effect test is carried out.

[0049] When testing the drag reduction effect, clean water is introduced into the water tank, and acid, alkaline solution and air are loaded into the injection device 7. First, the pipeline to be tested without the polymer brush drag reduction coating is installed at the corresponding position. If necessary, NaCl is added to the water tank to adjust the salinity. Set the required pH value, temperature, and flow rate, start the centrifugal pump, so that the water circulates in the annular test pipeline and flows according to the set working conditions. After stabilization, record the pressure difference value P1 of the pressure sensor (preferably the average value over a period of time).

[0050] Turn off the device, dismantle the pipe to be tested without polymer brush drag reducing coating, install the pipe to be tested with polymer brush drag reducing coating of the same diameter, repeat the above operation, and record the pressure difference value P2 of the pressure sensor after stabilization (preferably using the average value over a period of time).

[0051] Finally, the corresponding drag reduction rate can be calculated according to the formula Dr=(P1-P2) / P1×100%.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-parameter drag reduction effect test device for a small aspect ratio pipeline, characterized in that: include: A water tank, an annular test pipeline connected to the water tank at both ends, and a pipeline to be tested; a temperature control component for adjusting the temperature of the liquid in the water tank is arranged in the water tank; the pipeline to be tested is detachably arranged on the annular test pipeline, and pressure sensors are arranged at both ends of the annular test pipeline; an injection device is also arranged on the annular test pipeline, and the injection device is arranged in front of the pipeline to be tested, including a first injection device for injecting an acidic solution into the annular test pipeline, a second injection device for injecting an alkaline solution into the annular test pipeline, and a third injection device for injecting gas into the annular test pipeline; The testing device also includes a shrinkage pipe section and a buffer pipe section, which are arranged on an annular test pipeline and located in front of the pipeline to be tested. The shrinkage pipe section, the buffer pipe section and the pipeline to be tested are coaxially arranged. The shrinkage pipe section is a truncated cone structure. One end of the buffer pipe section is connected to an end with a small inner diameter of the shrinkage pipe section, and the other end is connected to the pipeline to be tested. The inner diameter and outer diameter of the buffer pipe section are consistent with the inner diameter and outer diameter of the pipeline to be tested.

2. A multi-parameter drag reduction effect test device for a small aspect ratio pipeline as claimed in claim 1, characterized in that: The length ratio of the contraction tube section to the buffer tube section is 3:

1.

3. The multi-parameter drag reduction effect testing device for a small aspect ratio pipeline according to claim 1, characterized in that: It also includes sensors arranged on the annular test pipeline for monitoring the state of liquid in the annular test pipeline, including a temperature sensor, a flow sensor, a pH sensor and a salinity sensor.

4. A multi-parameter drag reduction effect testing device for a small aspect ratio pipeline as claimed in claim 3, characterized in that: It also includes a control system, which is electrically connected to the sensor on the annular test pipeline and adjusts the parameters of the liquid in the annular test pipeline according to preset parameters and monitoring data of the sensor.

5. The multi-parameter drag reduction effect testing device for a small aspect ratio pipeline according to claim 4, characterized in that: It also includes a centrifugal pump and an electronically controlled throttle valve, which are both arranged on the annular test pipeline and are communicatively connected to the control system for changing the flow rate of the liquid in the annular test pipeline according to the control instructions issued by the control system.

6. The multi-parameter drag reduction effect testing device for a small aspect ratio pipeline according to claim 4, characterized in that: The injection device is communicatively connected with the control system, and is used to change the pH value and / or ventilation rate of the liquid in the annular test pipeline according to the control instructions issued by the control system.

7. The multi-parameter drag reduction effect testing device for a small aspect ratio pipeline according to claim 1, characterized in that: The annular test pipeline has a hose section at a position parallel to the pipeline to be tested.

8. A method for testing the multi-parameter drag reduction effect of a pipeline with a small aspect ratio, characterized in that: A multi-parameter drag reduction effect testing device for a small aspect ratio pipeline according to any one of claims 1 to 7, comprising: Select two pipes to be tested with the same size, and prepare a drag-reducing coating on the inner wall of one of the pipes to be tested; Different test parameters were set to test the pressure drops at both ends of the test pipe with and without drag reduction coating when the liquid flowed through the test pipe, and the corresponding drag reduction rate was calculated.

9. A method for testing the multi-parameter drag reduction effect of a pipeline with a small aspect ratio as claimed in claim 8, characterized in that: The method of preparing a drag-reducing coating on the inner wall of one of the pipelines to be tested comprises: An intermediate layer with grafting sites is prepared on the inner wall of the pipe to be tested; Connect the pipeline to be tested with the annular test pipeline; Add the precursor solution prepared by the polymer brush into the water tank, set the reaction temperature, pH value, liquid flow rate in the pipeline and air introduction rate, start the device, and make the precursor solution circulate in the annular test pipeline to form a polymer brush drag reduction coating on the inner wall of the pipeline to be tested.

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