Device and method for measuring pressure in stirring process

Abstract

The invention discloses a stirring process pressure measuring device and method, and relates to the technical field of pressure measurement. The device comprises an experiment barrel, a digital acquisition instrument and a computer, the experiment barrel comprises a stirring barrel body and a pressure conduction cavity which are separated by a partition plate, and the bottom of the pressure conduction cavity is further connected with a pressure transmitter used for measuring the pressure of a set measuring hole; the digital acquisition instrument is connected with the pressure transmitter and is used for acquiring the pressure of the plurality of measuring holes; and the computer is connected with the digital acquisition instrument, and is used for carrying out flow velocity calculation on the pressure in the stirring process according to the pressure of each measuring hole, and drawing pressure field distribution and velocity field distribution in the stirring barrel main body based on a calculation result. According to the invention, pressure signals can be acquired by using the side wall of the cylinder and the bottom transmitter, and pressure measurement at any position in a three-dimensional space is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure measurement, and in particular to a device and method for measuring pressure during a stirring process. Background Art

[0002] At present, mixing equipment is an indispensable key equipment in many industries such as chemical, construction, and medicine, and its performance is directly related to production efficiency and product quality. In traditional mixing equipment, the design of the impeller mostly adopts a classic structure, which has a certain gap in mixing efficiency and energy consumption compared with the new impeller. Therefore, it is necessary to measure the pressure at different positions to analyze the single-phase and two-phase flow conditions inside the mixing device.

[0003] However, the existing technologies for measuring pressure distribution during the mixing process are relatively limited, mostly relying on empirical estimation or simple sensor configuration. These methods often fail to accurately capture the complex three-dimensional fluid pressure and velocity field distribution inside the mixing equipment. In particular, the lack of precise pressure measurement point arrangement at key locations such as the sidewall and bottom results in insufficiently comprehensive and in-depth monitoring and analysis of the fluid flow state. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for measuring the pressure during a stirring process, which can utilize transmitters at the side wall and bottom of a cylinder to collect pressure signals and realize pressure measurement at any position in a three-dimensional space.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A device for measuring pressure during a stirring process, comprising:

[0007] The test cylinder comprises a stirring barrel body and a pressure transmission cavity separated by a partition, and the bottom of the pressure transmission cavity is also connected to a pressure transmitter for measuring the pressure of a set measuring hole;

[0008] A digital data collector, connected to the pressure transmitter, for collecting pressures of multiple measuring holes;

[0009] The computer is connected to the digital acquisition instrument and is used to calculate the flow rate of the pressure in the stirring process according to the pressure of each measuring hole, and to draw the pressure field distribution and velocity field distribution in the stirring barrel body based on the calculation results.

[0010] Optionally, a rubber ring is provided between the stirring barrel body and the pressure conduction cavity for sealing, and the stirring barrel body on the upper layer and the pressure conduction cavity on the lower layer are combined with the partition through a flange.

[0011] Optionally, the mixing barrel body specifically includes: a barrel, a speed regulating motor, a baffle, a stirring shaft and an impeller connected to the stirring shaft; the stirring shaft and the impeller are arranged inside the barrel, and a plurality of baffles are also arranged on the side wall of the barrel; the stirring shaft is also connected to the speed regulating motor.

[0012] Optionally, the pressure transmitter is also connected to a 24V DC power supply.

[0013] Optionally, the measuring holes include a first measuring hole group and a second measuring hole group; the first measuring hole group is arranged on the partition plate, and the second measuring hole group is arranged on the side wall of the cylinder wall.

[0014] The present invention also provides a method for measuring pressure during a stirring process, based on the above-mentioned device, comprising:

[0015] Check the measuring devices and calibrate the pressure transmitters;

[0016] After the inspection and the calibration are completed, the pressures of the multiple measuring holes are measured respectively to obtain multiple groups of data, and the flow rate is calculated based on each group of data, and the pressure field distribution and velocity field distribution in the mixing barrel body are plotted based on the calculation results.

[0017] Optionally, the inspection process specifically includes:

[0018] Check the sealing of the diaphragm in the cylinder and the upper and lower rubber rings, check whether there is water leakage at the bottom transmitter connection, and check whether there is liquid leakage at the valve connection and downstream of the valve when the drain pipe valve is closed;

[0019] After draining the water, place a bubble level on the partition inside the drum, adjust the height of the four corners of the mixing drum bracket to keep the mixing drum body horizontal. After filling the drum with water, place the scale on the four baffles respectively to check that the liquid height readings are equal to verify that the drum is placed horizontally.

[0020] Connect the impeller, stirring shaft and speed regulating motor and install them in the mixing drum. Place a bubble level on the top of the motor to adjust the stirring shaft to be perpendicular to the liquid surface. Measure the distance between the stirring shaft and the drum wall in four directions. Adjust the motor bracket so that the stirring shaft is located in the center of the drum as much as possible.

[0021] Before the experiment, water was added to the bottom cavity. To avoid bubbles in the cavity, the baffle and the upper cylinder were removed first, and water was added to the pressure-conducting cavity at the lower layer until the liquid level overflowed from the lower rubber ring. Then the baffle was tilted and covered from one side, so that the air was completely discharged from the other side.

[0022] Connect the pressure transmitter to the DC power supply and the digital data logger, then add water to the cylinder, observe the change in voltage reading, and then calibrate the pressure transmitter.

[0023] Optionally, the calibration process specifically includes:

[0024] First, fill the cylinder with water to a specific height h. Since the cylinder is an open container, the theoretical hydrostatic pressure caused by the liquid level is calculated, and the slope and intercept values ​​of the actual performance curve of the pressure transmitter are fitted to complete the calibration.

[0025] Optionally, the measuring process specifically includes:

[0026] Step 1: Use hot melt adhesive to seal measuring points 2 to 5, open measuring point 1, add water to the cylinder, read the liquid level horizontally, add water to the liquid level until the liquid level is 270 mm, and record the data logger reading at this time as the liquid level reference;

[0027] Step 2: Set the speed of the speed regulating motor to 300rpm, the digital sampling interval to 0.1s, and set the automatic stop after 1200 samplings, that is, the sampling time is 120s; set the sampling start time, according to the computer stopwatch, manually start the stirring motor when the set time is reached, and sampling will start automatically at this time. After sampling, turn off the motor and export the pressure data;

[0028] Step 3: Wait for 1 minute until the liquid surface returns to calm, then repeat step 2 and measure each measuring point 3 times;

[0029] Step 4: After measuring point 1 is completed, open the drain valve to drain the water in the upper cylinder, open measuring point 2, and close the remaining measuring points. After changing the measuring point, check whether there are bubbles in the cavity, keep the cavity fully filled with water, and fill water into the upper cylinder. After the water filling reaches 270mm, observe the data acquisition instrument reading and fine-tune the liquid level to the liquid height reference in step 1; repeat steps 2 to 3, and finally complete the measurement of all 5 measuring points;

[0030] Step 5: Process the pressure fluctuation data of the five measuring points, select measuring point 3 with the smallest fluctuation, open measuring point 3, close the other measuring points, and measure the pressure at different speeds in single phase. Since the speed regulating motor needs a certain startup time from starting to reaching the set speed, which is about 35s at 300rpm, about 45s at 400rpm, and about 55s at 500rpm, the sampling time is extended to 150s, so that the effective sampling time after reaching the set speed is greater than 90s at all speeds;

[0031] Step 6: Set the speed to 300rpm, 400rpm, and 500rpm respectively, repeat steps 2 to 3, and measure 3 times at each speed;

[0032] Step 7: Replace the assembled impeller and check the installation height of the impeller, keeping the net distance from the bottom at 90mm unchanged, repeat steps 2 to 6, and finally obtain multiple sets of data for different impellers.

[0033] Optionally, the flow rate calculation formula is:

[0034]

[0035] In the formula, v i is the total velocity at the measuring point i, m / s; p i-底 is the pressure of the measuring point at the bottom corresponding to measuring point i, Pa; p i-静 is the pressure at measuring point i, Pa; h i is the vertical distance from the measuring point i to the bottom, m; ρ is the fluid density, kg / m 3 .

[0036] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0037] The present invention discloses a device and method for measuring the pressure of a stirring process, wherein the device comprises an experimental cylinder, a digital acquisition instrument and a computer, wherein the experimental cylinder comprises a stirring barrel body and a pressure conduction cavity separated by a partition, and the bottom of the pressure conduction cavity is also connected to a pressure transmitter for measuring the pressure of a set measuring hole; the digital acquisition instrument is connected to the pressure transmitter for collecting the pressure of multiple measuring holes; the computer is connected to the digital acquisition instrument for calculating the flow rate of the pressure of the stirring process according to the pressure of each measuring hole, and drawing the pressure field distribution and velocity field distribution in the stirring barrel body based on the calculation results. The present invention can collect pressure signals by using the cylinder side wall and the bottom transmitter to realize pressure measurement at any position in three-dimensional space. The present invention can obtain the three-dimensional fluid velocity field and pressure field distribution inside the stirring device by arranging pressure measurement points on the side wall and the bottom of the stirring device and establishing the relationship between pressure and fluid flow rate, thereby providing a reference for the two-phase mixing degree analysis and the stirring device performance evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0039] Figure 1 It is a structural schematic diagram of the stirring process pressure measuring device of the present invention;

[0040] Figure 2 Schematic diagram of the mixing drum structure dimensions and the opening positions of the measuring points in this embodiment; wherein, part (a) is a schematic diagram of the drum opening; part (b) is a schematic diagram of the partition measurement point positions and the drum dimensions;

[0041] Figure 3 It is a logical schematic diagram of the method for measuring pressure during the stirring process of the present invention.

[0042] Figure numerals: 1. speed regulating motor; 2. baffle; 3. stirring shaft; 4. impeller; 5. cylinder; 6. partition; 7. pressure transmission cavity; 8. pressure transmitter; 9. measuring hole; 10. DC power supply; 11. digital data acquisition instrument; 12. computer. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The purpose of the present invention is to provide a device and method for measuring the pressure during a stirring process, which can utilize transmitters at the side wall and bottom of a cylinder to collect pressure signals and realize pressure measurement at any position in a three-dimensional space.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] like Figure 1 As shown, the present invention provides a device for measuring pressure during a stirring process, comprising:

[0047] The experimental cylinder 5 includes a stirring barrel body and a pressure transmission cavity 7 separated by a partition 6, and a pressure transmitter 8 is also connected to the bottom of the pressure transmission cavity 7 for measuring the pressure of the set measuring hole 9.

[0048] The digital data collector 11 is connected to the pressure transmitter 8 and is used to collect the pressure of the multiple measuring holes 9 .

[0049] The computer 12 is connected to the digital data collector 11 and is used to calculate the flow rate of the pressure during the mixing process according to the pressure of each measuring hole 9, and to draw the pressure field distribution and velocity field distribution in the mixing barrel body based on the calculation results.

[0050] Among them, the impeller 4 is connected to the speed regulating motor 1 through the stirring shaft 3, and the pressure transmitter 8 is installed at the bottom of the cylinder 5. A cavity is set at the bottom of the cylinder 5 to transmit the pressure from the measuring point to the bottom transmitter, so that there is no need to disassemble and move the transmitter when changing the measuring point, thereby ensuring the sealing of the interface. When measuring the pressure of a certain measuring point, the remaining measuring points are blocked. When the measuring point needs to be changed, the closed point can be changed. A DC power supply 10 is set to output 24V DC to power the pressure transmitter 8. The transmitter converts the measured pressure signal into a voltage signal, which is collected by a digital acquisition instrument 11, and recorded and displayed in real time in the computer 12 software.

[0051] The upper layer of the experimental cylinder 5 is the mixing cylinder body, and the lower layer is the pressure transmission cavity 7, which is separated by a partition 6 in the middle. A rubber ring is set between the upper and lower layers, and the upper and lower layers and the partition 6 are combined by a flange. The holes on the bottom plate are measuring points 1 to 5, and the holes on the side of the cylinder wall are measuring points 6 to 10, for a total of 10 measuring points. The upper fluid pressure is transmitted to the cavity by opening a certain measuring point, and then transmitted to the pressure transmitter 8. When replacing the measuring point, the remaining measuring points are sealed with hot melt adhesive. The size of the cylinder 5 and the position of the hole opening at the measuring point on the partition 6 are as follows Figure 2 shown.

[0052] Then the pressure of the measuring points is collected respectively. According to the relationship between the dynamic pressure and static pressure of the measuring points, it can be obtained:

[0053] p i-静 +p i-动 +ρgh i =p i-底

[0054] further:

[0055] p i-动 =p i-底 -p i-静 -ρgh i

[0056] Also because:

[0057]

[0058] Finally, the velocity at the intersection of the horizontal plane at the measuring point i in the mixing drum and the vertical plane at the bottom measuring point can be calculated:

[0059]

[0060] In the formula, v i is the total velocity at the measuring point i, m / s; p i-底 is the pressure of the measuring point at the bottom corresponding to measuring point i, Pa; p i-静 is the pressure at measuring point i, Pa; h i is the vertical distance from the measuring point i to the bottom, m; ρ is the fluid density, kg / m 3 .

[0061] Therefore, through the above formula, the fluid velocity at multiple points in the mixing drum can be obtained in three dimensions, and then the velocity field distribution and pressure field distribution in the mixing drum can be plotted, which can provide data support for the complex flow field analysis during the mixing process. Figure 3 shown.

[0062] 1. Experimental Preparation

[0063] (1) Check the sealing of the cylinder 5 partition 6 and the upper and lower rubber rings, and check whether there is any leakage at the bottom transmitter connection. Check that when the drain pipe valve is closed, there is no liquid leakage at the valve connection and downstream of the valve.

[0064] (2) After draining the water, place a bubble level on the inner baffle 6 of the cylinder and adjust the height of the four corners of the mixing cylinder support to keep the cylinder as horizontal as possible. After filling the cylinder with water, place the scale at the four baffles 2 to check that the liquid height readings are equal and verify that the cylinder 5 is placed horizontally.

[0065] (3) Connect the impeller 4, the stirring shaft 3 and the motor and install them in the mixing drum. Place a bubble level on the top of the motor to adjust the stirring shaft 3 to be perpendicular to the liquid surface. Measure the distance between the stirring shaft 3 and the drum wall in four directions and adjust the motor bracket so that the stirring shaft 3 is located as close to the center of the drum 5 as possible.

[0066] (4) Before the experiment, water was added to the bottom cavity. To avoid bubbles in the cavity, the baffle 6 and the upper cylinder 5 were first removed, and water was added to the bottom. Water was added until the liquid level overflowed from the lower rubber ring, and then the baffle 6 was tilted from one side to cover it, so that the air was completely discharged from the other side.

[0067] (5) Connect the pressure transmitter 8 to the power supply and digital data acquisition instrument 11, then add water into the cylinder, and observe the change in the voltage reading. Then calibrate the pressure transmitter 8.

[0068] 2. Pressure transmitter 8 calibration

[0069] The water pressure at the bottom of the mixing drum is converted into a voltage signal by the pressure transmitter 8, and is restored to a pressure signal after being collected and processed by the computer 12. The pressure range of the transmitter is 0-5kPa, and the sensor outputs a voltage signal of 0-10V under pressure. Ideally, the conversion between the voltage signal and the pressure signal is a linear relationship, that is, the pressure signal can be restored with P=1 / 2V. However, in actual applications, due to the influence of ambient temperature, gravity acceleration, etc., the transmitter may have zero point offset, so it is necessary to calibrate the transmitter to eliminate this error.

[0070] First, fill the mixing drum with water to a specific height h. Since the drum 5 is an open container, the theoretical hydrostatic pressure brought by the liquid level at this time can be expressed by P i=ρgh. Assuming the actual performance curve of the transmitter is V=aP+s, the slope a and intercept value s in the formula can be fitted by calculating the values ​​at multiple heights. The fitting results are: a=1.9854, s=0.18034.

[0071] Table 1 Pressure transmitter 8 calibration points

[0072]

[0073]

[0074] The Pearson correlation coefficient of the fitted straight line is r = 0.99933, R2 = 0.99866. As shown in Table 1, after calibration, the measurement error when the upper cylinder is filled with water is less than 2%.

[0075] 3. Experimental Operation

[0076] (1) Use hot melt adhesive to seal measuring points 2 to 5 and open measuring point 1. Add water to the cylinder and read the liquid level horizontally until the liquid level reaches 270 mm. Record the data logger reading at this time as the liquid level reference.

[0077] (2) Set the speed of the speed regulating motor 1 to 300 rpm and the digital sampling interval to 0.1 s. Set the sampling to stop automatically after 1200 times, that is, the sampling time is 120 s. Set the sampling start time to an appropriate time. According to the computer 12-second watch, manually start the stirring motor when the set time is reached. At this time, sampling automatically starts. After sampling, turn off the motor and export the pressure data.

[0078] (3) Wait for 1 minute until the liquid surface returns to calm, then repeat step 2. Measure each measuring point 3 times.

[0079] (4) After measuring point 1, open the drain valve to drain the water in the upper cylinder. Open measuring point 2 and close the remaining measuring points. After changing the measuring point, check whether there are bubbles in the cavity and keep the cavity fully filled with water. Fill the upper cylinder with water. When the water filling reaches 270mm, observe the data acquisition instrument reading and fine-tune the liquid level to the liquid height reference in step 1. Repeat steps 2 to 3. Finally, complete the measurement of all 5 measuring points.

[0080] (5) Process the pressure fluctuation data of the five measuring points and select the measuring point 3 with the smallest fluctuation. Open measuring point 3 and close the other measuring points to measure the pressure at different speeds in single phase. Since the speed regulating motor 1 needs a certain startup time from starting to reaching the set speed, it is about 35s at 300rpm, about 45s at 400rpm, and about 55s at 500rpm. Extend the sampling time to 150s so that the effective sampling time after reaching the set speed is greater than 90s at all speeds.

[0081] (6) Set the speed to 300 rpm, 400 rpm, and 500 rpm respectively, repeat steps 2 to 3, and measure three times at each speed.

[0082] (7) Replace and assemble the impeller 4, and check the installation height of the impeller 4, keeping the net distance from the bottom at 90 mm. Repeat steps 2 to 6. Finally, multiple sets of data are obtained for different impellers 4, see Table 2. Among them, ○ represents three sets of data that were repeatedly measured.

[0083] Table 2 Single-phase stirring measurement

[0084]

[0085] Therefore, the present invention has the following advantages and significant effects:

[0086] (1) The prior art can only measure the pressure at a single position in the cylinder 5 and cannot measure the pressure at any position in the three-dimensional space. The present invention uses the transmitters on the side wall and bottom of the cylinder 5 to collect pressure signals, which can monitor the pressure fluctuations at any position during the stirring process in real time and analyze the pressure change trend on any cross section, which is very important for the performance evaluation and guidance of the stirring device; (2) It avoids the calculation errors caused by the use of empirical correlation formulas and the subjective factors of visual inspection, and has good adaptability to working conditions such as different stirring equipment sizes and stirring powers.

[0087] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0088] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A device for measuring pressure during a stirring process, characterized in that: include: The test cylinder comprises a stirring barrel body and a pressure transmission cavity separated by a partition, and the bottom of the pressure transmission cavity is also connected to a pressure transmitter for measuring the pressure of a set measuring hole; A digital data collector, connected to the pressure transmitter, for collecting pressures of multiple measuring holes; The computer is connected to the digital acquisition instrument and is used to calculate the flow rate of the pressure in the stirring process according to the pressure of each measuring hole, and to draw the pressure field distribution and velocity field distribution in the stirring barrel body based on the calculation results.

2. The stirring process pressure measuring device according to claim 1, characterized in that: A rubber ring is also provided between the mixing barrel body and the pressure conduction cavity for sealing, and the mixing barrel body on the upper layer and the pressure conduction cavity on the lower layer are combined with the partition through a flange.

3. The stirring process pressure measuring device according to claim 1, characterized in that: The mixing barrel body specifically includes: a barrel, a speed regulating motor, a baffle, a stirring shaft and an impeller connected to the stirring shaft; the stirring shaft and the impeller are arranged inside the barrel, and a plurality of baffles are also arranged on the side wall of the barrel; the stirring shaft is also connected to the speed regulating motor.

4. The stirring process pressure measuring device according to claim 1, characterized in that: The pressure transmitter is also connected to a 24V DC power supply.

5. The stirring process pressure measuring device according to claim 1, characterized in that: The measuring holes include a first measuring hole group and a second measuring hole group; the first measuring hole group is arranged on the partition plate, and the second measuring hole group is arranged on the side wall of the cylinder wall.

6. A method for measuring pressure during a stirring process, based on the device according to any one of claims 1 to 5, characterized in that: include: Check the measuring devices and calibrate the pressure transmitters; After the inspection and the calibration are completed, the pressures of the multiple measuring holes are measured respectively to obtain multiple groups of data, and the flow rate is calculated based on each group of data, and the pressure field distribution and velocity field distribution in the mixing barrel body are plotted based on the calculation results.

7. The method for measuring the pressure during stirring according to claim 6, characterized in that: The inspection process specifically includes: Check the sealing of the diaphragm in the cylinder and the upper and lower rubber rings, check whether there is water leakage at the bottom transmitter connection, and check whether there is liquid leakage at the valve connection and downstream of the valve when the drain pipe valve is closed; After draining the water, place a bubble level on the partition inside the drum, adjust the height of the four corners of the mixing drum bracket to keep the mixing drum body horizontal. After filling the drum with water, place the scale on the four baffles respectively to check that the liquid height readings are equal to verify that the drum is placed horizontally. Connect the impeller, stirring shaft and speed regulating motor and install them in the mixing drum. Place a bubble level on the top of the motor to adjust the stirring shaft to be perpendicular to the liquid surface. Measure the distance between the stirring shaft and the drum wall in four directions. Adjust the motor bracket so that the stirring shaft is located in the center of the drum as much as possible. Before the experiment, water was added to the bottom cavity. To avoid bubbles in the cavity, the baffle and the upper cylinder were removed first, and water was added to the pressure-conducting cavity at the lower layer until the liquid level overflowed from the lower rubber ring. Then the baffle was tilted and covered from one side, so that the air was completely discharged from the other side. Connect the pressure transmitter to the DC power supply and the digital data logger, then add water to the cylinder, observe the change in voltage reading, and then calibrate the pressure transmitter.

8. The method for measuring the pressure during stirring according to claim 6, characterized in that: The calibration process specifically includes: First, fill the cylinder with water to a specific height h. Since the cylinder is an open container, the theoretical hydrostatic pressure caused by the liquid level is calculated, and the slope and intercept values ​​of the actual performance curve of the pressure transmitter are fitted to complete the calibration.

9. The method for measuring the pressure during stirring according to claim 6, characterized in that: The measuring process specifically includes: Step 1: Use hot melt adhesive to seal measuring points 2 to 5, open measuring point 1, add water to the cylinder, read the liquid level horizontally, add water to the liquid level until the liquid level is 270 mm, and record the data logger reading at this time as the liquid level reference; Step 2: Set the speed of the speed regulating motor to 300rpm, the digital sampling interval to 0.1s, and set the automatic stop after 1200 samplings, that is, the sampling time is 120s; set the sampling start time, according to the computer stopwatch, manually start the stirring motor when the set time is reached, and sampling will start automatically at this time. After sampling, turn off the motor and export the pressure data; Step 3: Wait for 1 minute until the liquid surface returns to calm, then repeat step 2 and measure each measuring point 3 times; Step 4: After measuring point 1 is completed, open the drain valve to drain the water in the upper cylinder, open measuring point 2, and close the remaining measuring points. After changing the measuring point, check whether there are bubbles in the cavity, keep the cavity fully filled with water, and fill water into the upper cylinder. After the water filling reaches 270mm, observe the data acquisition instrument reading and fine-tune the liquid level to the liquid height reference in step 1; repeat steps 2 to 3, and finally complete the measurement of all 5 measuring points; Step 5: Process the pressure fluctuation data of the five measuring points, select measuring point 3 with the smallest fluctuation, open measuring point 3, close the other measuring points, and measure the pressure at different speeds in single phase. Since the speed regulating motor needs a certain startup time from starting to reaching the set speed, which is about 35s at 300rpm, about 45s at 400rpm, and about 55s at 500rpm, the sampling time is extended to 150s, so that the effective sampling time after reaching the set speed is greater than 90s at all speeds; Step 6: Set the speed to 300rpm, 400rpm, and 500rpm respectively, repeat steps 2 to 3, and measure 3 times at each speed; Step 7: Replace the assembled impeller and check the installation height of the impeller, keeping the net distance from the bottom at 90mm unchanged, repeat steps 2 to 6, and finally obtain multiple sets of data for different impellers.

10. The method for measuring the pressure during stirring according to claim 6, characterized in that: The formula for calculating the flow rate is: In the formula, v i is the total velocity at the measuring point i, m / s; p i-底 is the pressure of the measuring point at the bottom corresponding to measuring point i, Pa; p i-静 is the pressure at measuring point i, Pa; h i is the vertical distance from the measuring point i to the bottom, m; ρ is the fluid density, kg / m 3 .

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