During the operation of the pulse bag type dust collector , its dust removal efficiency and filter bag life will be affected by the flow field distribution inside the equipment. Therefore, it is necessary to systematically analyze the internal flow field of the pulse bag filter and the performance of the equipment to complete its promotion and application.
Improving the internal flow field of the pulse bag type dust collector to improve the dust removal efficiency
1. Working principle:
As a dust collector with compressed air as the power for dust removal, it can use the pulse blowing mechanism to release the compressed air instantaneously, and induce the air several times, so that it can enter the filter bag of the dust collector at a higher speed. . In the case of the filter bag's rapid expansion, shock vibration and directional airflow can be used to remove dust in the filter bag. From the structural point of view, the pulse bag type dust collector is composed of filter bag, dust gas chamber, air bag, electric controller, pulse valve, clean room, blow pipe and pneumatic valve.
During the operation of the dust collector, the dust-containing gas will enter the dust chamber from the inlet, and enter the clean room through the filter bag. In this process, dust will be left on the outer surface of the filter bag, and clean air will be discharged through the outlet. When the pressure difference value is reached, the electronic controller will control the pulse valve, so that the high-pressure gas in the air bag is ejected through the injection pipe. When both high-speed airflow and induced airflow enter the filter bag, the filter bag will expand rapidly, and at the same time, high-pressure airflow will be ejected through the tiny gaps of the filter bag fibers. At this time, the filter bag will shrink rapidly, causing the dust to fall off. However, in the process of dust removal, the dust removal work of the pulse bag type dust collector mainly occurs in the dust layer. If the internal flow field of the dust collector is not uniformly distributed, the thickness of the dust layer on each filter bag will be different. Different dust thicknesses result in different resistances, which leads to uneven flow field distribution.
Therefore, if the internal flow field of the dust collector cannot be uniformly distributed, the dust removal efficiency of the pulse bag dust collector will become lower and lower.
2. Internal flow field analysis:
2.1. Internal flow field analysis model:
In order to analyze the internal flow field of the pulse bag filter, CFD technology, GAMBIT software and FLUENT software can be used to simulate the value of the internal flow field of the dust collector. By analyzing the relevant simulation parameters, not only the characteristics of the flow field distribution of the dust collector can be lifted, but also a method for making the flow field uniformly distributed. When establishing the model, the dust collector can be set to the down-in operation mode, and 4 rows and 6 columns of filter bags can be set. However, its internal flow field should be a complex three-dimensional, strong swirling, turbulent flow field, so a turbulence model can be selected to analyze its flow field distribution. Specifically, _ is a RNG model that uses the SIMPLE algorithm and the standard wall function method. In addition, it is also necessary to assume that the fluid inside the dust collector is air at normal temperature and pressure, which cannot be compressed. At the same time, it is also assumed that the fluid often flows, and its motion parameters are independent of time. In the calculation process, it is necessary to assume that the airflow direction is perpendicular to the inlet end face, and that the inflow from the outlet boundary of the exhaust port has been fully developed. In addition, the filter bag must meet the boundary conditions for porous media, and its outlet must meet the internal boundary conditions.
2.2 Simulation results of internal flow field:
2.2.1. Analysis of flow field characteristics:
It can be known from the simulation calculation results that when the high-speed airflow enters the ash hopper, there will be a clear jet that can continue to the rear wall of the ash hopper. At the same time, inside and outside the filter bag, the velocity gradient of the air is relatively large, and local vortices appear. In addition, a high-speed airflow region appeared at the connection position between the exhaust pipe and the clean room. Analyzing the reasons for the existence of these fluids, it can be found that the internal flow field of the dust collector is not evenly distributed, so that it cannot complete the particle separation work well, and then accelerate the wear rate of the filter bag in the local area.
Degree, shortening its service life. When the airflow meets the rear wall of the ash hopper, part of the airflow will move upward along the wall, and the other part will move downward along the oblique surface. Due to the excessively high velocity of the airflow moving upward, the filter bag is severely impacted, causing the filter bag to be damaged; while the airflow moving downward will form a backflow, hindering the collection and separation of dust. At this time, the previously filtered particulate matter can easily be brought back to the tank by backflow, increasing the filtration load of the filter bag. In this case, both the front and rear filter bags are easily damaged, which reduces the separation efficiency of the dust collector. In addition, the occurrence of gas backflow makes the airflow inside the dust collector more turbulent, which in turn affects the separation of dust by the dust collector.
2.2.2. Analysis of uniformity of flow field distribution:
When analyzing the uniformity of the flow field distribution inside the dust collector, the US RMS standard should be adopted, and the measurement point section should be set at the connection between the dust collector and the ash hopper to ensure that the measured data is representative of _. It is known from the relevant analysis that the internal flow field of the pulse bag filter is not uniformly distributed. Specifically, because the cross-sectional area of the inlet pipe of the dust collector is significantly different from the cross-sectional area of the ash hopper, when the airflow enters the ash hopper from the air inlet pipe, violent movement will occur, and then the airflow disorder will occur . However, such a flow field distribution will affect the separation performance of the dust collector and shorten the service life of the filter bag. Therefore, in order to solve this problem, it is necessary to reduce the dynamic-static pressure conversion intensity of the inlet end face of the dust collector and the section of the ash bucket, so that the internal flow field of the dust collector is evenly distributed. In order to achieve this purpose, it is necessary to set a uniform air distribution device such as a deflector between the two, so as to improve the filter performance of the dust collector and extend the service life of the filter bag.
3. Concluding remarks:
All in all, the pulse bag type dust collector has the characteristics of good ash cleaning effect and high purification efficiency. The use of this type of dust collector can not only reduce the degree of air pollution, but also save the energy of people's work and living environment. It is worth being widely promoted. However, when analyzing the internal flow field distribution of the dust collector, it was found that in order to use the precipitator's performance, it is necessary to increase the uniformity of the internal flow field distribution. Therefore, this paper briefly studies the internal flow field distribution of the pulse bag type dust collector
in order to provide guidance for the future application and promotion of this type of dust collector.