The development and experimental research of the performance test platform of the new agitator

Mixing and mixing operation is one of the most widely used process unit operations, widely used in chemical, petrochemical, pharmaceutical, paper, coatings, metallurgy, wastewater treatment and other industries. Mechanical mixing equipment plays an extremely important role in the main substances used in the manufacture of coatings, such as paint materials and synthetic resins, and the stirring effect is not ideal, which will lead to the phenomenon of implosion and fusion of the kettle, which seriously affects the quality of the polymer. Therefore, the study of stirring technology has also become very important
the
.
At present, there are fewer experimental platforms used to study the performance of agitators, and there are some problems, such as:
(1) mixing shaft positioning accuracy is low and flexibility is poor, can not guarantee that each experiment agitator is in the center axis, the vertical position of the mixing shaft is relatively fixed, according to the changes in the mixer in the vertical direction of the mixer height adjustment
; (2) The test conditions are simple and the agitator stirring performance test cannot be carried out in a medium with corrosiveness and pressure;
(3) testing process is cumbersome and cannot detect the viscosity and density of the slurry in real
; ( 4) The head of the mixer is mostly flat-bottomed, while the actual industrial application is broader than the oval head;
(5) the kettle material is all glass, the glass material is not easy to seal and fragile, which brings many unnecessary risks to the test;
(6) the diameter of the kettle is small, the volume of the kettle body and the actual industrial application of the mixer is quite different, resulting in a large deviation in the application of amplification. Based on the actual requirements, this study overcomes the shortcomings of the previous test platform and develops a new agitator performance test platform with strong comprehensive performance and easy operation. And use FLUENT6. 3 Numerical simulation of the stirring power of 3 kinds of conventional blades, the experimental and CFD simulation results show that the performance of the experimental platform is stable, easy to operate and has good precision.
1 Structural features
1. 1 Introduction to the agitator performance test platform
The agitator performance test platform is mainly composed of kettle body, stirring drive, stirring shaft lifting bracket, control cabinet and other components, and its supporting test software can monitor the agitator performance parameters in real time. The technology platform can be used for different specifications of blades, containers and mixing shafts, to achieve the mixing mixing time, mixing efficiency and stirring power and other performance indicators. The main body structure of the test platform is shown in Figure 1.
of the main structure of the agitator performance test platform
1. 2 Bus body part
figure 2 is the test platform entity diagram.
Agitator performance test platform solid figure
kettle body mounted on the test platform base, through bolts and base fixation, can ensure sufficient rigidity when stirring; Under normal pressure conditions, the barrel part of the test platform is made of 15 mm thick omeglass, according to the mixing medium and operating conditions, the body part can be replaced with tempered glass material cylinder body, transparent container advantages are convenient to observe the flow field state in the kettle during the experiment, as well as the use of particle image velocity measurement technology (PIV) and digital particle image technology (DPIV) and other observation cylinder fluid flow field and velocity field. According to the needs of the test, different specifications of the kettle body supporting the mixer can also be easily replaced. The upper head of the kettle body adopts a flat seal head, which consists of different specifications of sealing plate nesting, which, while ensuring partial sealing, also facilitates the replacement of different mixing shafts and stirring blades. For the first time, the lower head of the kettle body uses a standard oval seal with a wide range of industrial applications in the test machine, which facilitates the application of amplification technology simulation, and the seal can effectively eliminate the dead zone of the flow that is not easily reached when stirring.
3 Control System The control
is composed of the computer used for the test, the relevant test instruments and the operator's station. The actual power of different agitators at different speeds is transmitted to the HP-JCA intelligent electronic monitoring station through the drive, and the electrical signal of the temperature sensor is also transmitted to the electronic monitoring station, which is then transmitted back to the software interface via the 485-to-232 module. The stirring speed is entered on the software interface. The software internally nests the various equations of the agitator, through the software sub-menu, you can choose to customize the pulp leaves, enter the various size parameters of the blades, choose to enter the corresponding parameters of various agitators and the test data of the stirring liquid, you can get the theoretical stirring power of different agitators, stirring efficiency and so on.
2 works in the same way as
2. 1 Technical features The technical
the agitator performance test platform are set out in Table 1.
the technical parameters of the agitator performance testing platform
2. 2 Principle
The lifting system of the
test platform consists of a drive and a base and is powered by two motors, of which the speed control motor is transmitted through the Siemens 6SE6440 - 2UD17- 5AA1 drive to achieve the required stirring speed, and its power is also transmitted through the drive software. Another motor uses hydraulic principles to achieve the lifting of the mixing shaft.
blade is an important part of the mixing system, the test platform is equipped with paddle, open turbine, disc turbine, propulsion and other blades. This design, on the one hand, can easily replace the pulp leaves, the mixing shaft to the upper part of the kettle body, you can easily achieve different specifications, model blade replacement, on the other hand, when replacing the mixing container, can ensure that the mixing shaft on the same central axis, and according to the change of the kettle body, can achieve the blade in the vertical direction of the body of the kettle in any position to stay. The stirring time is usually determined by fading, conductivity, and temperature difference. Considering the accuracy and ease of operation, the test platform uses the temperature difference method to determine the stirring time. The test platform's software enables real-time detection and transmission of 3-point temperatures through 3 temperature sensors placed in different locations, and the HP-JCA Intelligent Electronic Monitoring Station processes electrical signals from the temperature sensors to the software. Based on the intelligent control consideration of the test system, the designer developed a supporting visual software system. During the test, the time used to meet the mixing requirements is automatically recorded by the software, and the temperature-time image is drawn simultaneously, which reflects the stirring process and the mixing effect intuitively.
3 Experimental Testing and Analysis
3. 1 Determination of stirring time
7 traditional pulp leaves such as paddle, open turbine, disc turbine, etc. are tested on this test platform. Add a water solution of a certain temperature to 70% of the volume scale, then lower the mixing oar to the appropriate height, add a certain proportion of the volume of 90 degrees C aqueous solution, enter different stirring speed for mixing time measurement. Figure 3 shows the test results at speeds of 2 r /s, 3 r/s, and 4 r /s.
The results of each agitator stirring time measurement
From the test results, it can be seen that this performance test platform accurately and intuitively reflects the correlation between stirring speed and stirring effect (stirring time), that is, in a certain speed range, improving the speed can significantly reduce the stirring time. At low speed, the oar type takes a long time to stir, and the turbine six-straight leaf type takes the shortest time. With the increase of speed, the turbulence of liquid increases, and the stirring time of various agitators decreases significantly and gets closer and closer.
3. 2 Determination of stirring power
stirring power is an important characteristic of blades, the theoretical stirring power is calculated by formula (1) s7):
μ is the viscosity value of the measured liquid; N to set the stirring speed value; ρ is liquid density; D is the diameter of the kettle; H is the depth of the liquid. The power of the seven blades described above was tested in an aqueous solution at speeds of 2 r /s, 3 r /s, and 4 r /s, as shown in Figure 4.
results of the agitator agitation power determination
it can be derived from Figure 4, with the increase of speed, the actual consumption of power of each agitator increased significantly. Among them, the power consumed by the paddle agitator is relatively low, and the power consumed by the disc six straight leaves and the turbine six straight leaves is larger. At the same speed, the propeller blade consumes about two-thirds of the power of the turbine six straight leaves and the disc six straight blades. Use finite meta software FLUENT6. 3 Simulate the power of the 3 mixing paddles . . . . . . . . . . . . . . . . . . . . . . . . . Figure 5 shows the comparison of measured power with simulated power. Comparing 2 kinds of results, it can be found that the platform can accurately determine the actual power consumed by the mixing oar. The percentage of error between actual and theoretical power is within 10%. Through the test results of 7 kinds of blades, it can be seen that when tested in aqueous solution, the error of the experimental data obtained is very small. With the increase of the mucus of the solution, the power error of some blades increased slightly in the course of the experiment. The reason is, on the one hand, with the increase of viscosity, the power consumed by stirring also increases accordingly, so that the mechanical loss of the decelerator and couplings and so on also increases; On the other hand, there are some manufacturing errors in the blades used in the test, and with the increase of viscosity, the error in power caused by them becomes more and more obvious.
Agitator Measured Power vs. Analog Power
4 Conclusion
This experimental platform uses a fully automatic hydraulic lifting system, an open transparent mixing tank, an intelligent variable frequency speed control system, and a visual operating interface. Compared with the traditional stirring experimental device, the operator's labor intensity is greatly reduced, which makes it more convenient to clean the mixing groove and replace the blades, and the positioning accuracy of the blades is greatly improved. The design of the open transparent mixing tank and the visual control program more intuitively reflect the process of stirring in the tank and provide a platform for the application of the latest particle image speed measurement technology (PIV). The experimental results and numerical simulation show that the experimental device has high precision, which provides a reliable basis for the teaching of stirring performance and the development and optimization of new blades in the coating industry.