英语
西班牙语
阿拉伯语A complete dust removal system includes four parts: dust hood, ventilation duct, dust collector and fan. Ventilation ducts (referred to as ducts) are channels for conveying dust-laden airflow, which connect dust hoods, dust collectors, and fans into a whole. Whether the piping design is reasonable or not directly affects the effect of the entire dust removal system. Therefore, various issues in the pipeline design must be fully considered in order to obtain a more reasonable and effective solution.
1. Piping components
1.1 Elbow
The elbow is a common component connecting the pipeline, and its resistance is related to the elbow diameter d, the radius of curvature R, and the number of sections of the elbow. The larger the radius of curvature R, the smaller the resistance. However, when R is greater than 2~2.5d, the resistance of the elbow is no longer significantly reduced, and the occupied space is too large, making the system piping, components and equipment difficult to arrange. Therefore, from the practical point of view, R generally takes 1~ 2d, 90° elbows are generally divided into 4 to 6 sections.
1.2 Three links
In the dust removal system of the centralized air network, the air flow converging part-the three links is often used. When the airflow velocity of the two branches in the confluence tee is different, the ejection effect will occur, and at the same time, there will be energy exchange. That is, the high flow velocity loses energy, the low flow velocity gains energy, but the total energy is lost. In order to reduce the resistance of the tee, the ejection phenomenon should be avoided. When designing, it is best to make the air velocity of the two branch pipes and the main pipe equal, that is, V1=V2=V3, then the relationship between the cross-sectional diameters of the two branch pipes and the main pipe is d12+d22=d32.
The resistance of the tee is related to the direction of the airflow. The angle between the two branches is generally 15°～30° to ensure smooth air flow and reduce resistance loss. The tee connection cannot be used for the tee connection, because the resistance of the tee connection is 4 to 5 times larger than the reasonable connection method.
In addition, try to avoid the use of four-way, because the airflow in the four-way interference is great, which seriously affects the suction effect and reduces the efficiency of the system.
1.3 Expanding tube
When the gas flows in the pipeline, if the cross section of the pipeline suddenly changes from small to large, the gas flow also suddenly expands, causing a large impact pressure loss. In order to reduce the resistance loss, a divergent tube with a smooth transition is usually used. The resistance of the divergent tube is caused by the formation of a vortex zone due to the inertia of the air flow when the cross-section is enlarged. The larger the divergence angle а, the larger the vortex area and the larger the energy loss. When a exceeds 45°, the pressure loss is equivalent to the impact loss. In order to reduce the resistance of the diverging tube, the diverging angle a must be minimized, but the smaller a, the greater the length of the diverging tube. Generally, the divergent angle a is preferably 30°.
1.4 Interface and outlet of pipe and fan
When the fan is running, vibration will occur. In order to reduce the impact of vibration on the pipeline, it is best to use a hose (such as a canvas hose) where the pipeline and the fan are connected. A straight pipe is generally used at the outlet of the fan. When the elbow needs to be installed at the outlet of the fan due to the limitation of the installation position, the direction of rotation of the elbow should be consistent with the direction of rotation of the fan impeller.
The outlet airflow of the pipe is discharged into the atmosphere. When the airflow is discharged from the pipe mouth, all the energy of the airflow before it is discharged will be lost. In order to reduce the loss of dynamic pressure at the outlet, the outlet can be made into a diverging tube with a small divergent angle. It is best not to install a hood or other objects at the outlet, and at the same time minimize the airflow velocity of the exhaust outlet.
1. Piping components
1.1 Elbow
The elbow is a common component connecting the pipeline, and its resistance is related to the elbow diameter d, the radius of curvature R, and the number of sections of the elbow. The larger the radius of curvature R, the smaller the resistance. However, when R is greater than 2~2.5d, the resistance of the elbow is no longer significantly reduced, and the occupied space is too large, making the system piping, components and equipment difficult to arrange. Therefore, from the practical point of view, R generally takes 1~ 2d, 90° elbows are generally divided into 4 to 6 sections.
1.2 Three links
In the dust removal system of the centralized air network, the air flow converging part-the three links is often used. When the airflow velocity of the two branches in the confluence tee is different, the ejection effect will occur, and at the same time, there will be energy exchange. That is, the high flow velocity loses energy, the low flow velocity gains energy, but the total energy is lost. In order to reduce the resistance of the tee, the ejection phenomenon should be avoided. When designing, it is best to make the air velocity of the two branch pipes and the main pipe equal, that is, V1=V2=V3, then the relationship between the cross-sectional diameters of the two branch pipes and the main pipe is d12+d22=d32.
The resistance of the tee is related to the direction of the airflow. The angle between the two branches is generally 15°～30° to ensure smooth air flow and reduce resistance loss. The tee connection cannot be used for the tee connection, because the resistance of the tee connection is 4 to 5 times larger than the reasonable connection method.
In addition, try to avoid the use of four-way, because the airflow in the four-way interference is great, which seriously affects the suction effect and reduces the efficiency of the system.
1.3 Expanding tube
When the gas flows in the pipeline, if the cross section of the pipeline suddenly changes from small to large, the gas flow also suddenly expands, causing a large impact pressure loss. In order to reduce the resistance loss, a divergent tube with a smooth transition is usually used. The resistance of the divergent tube is caused by the formation of a vortex zone due to the inertia of the air flow when the cross-section is enlarged. The larger the divergence angle а, the larger the vortex area and the larger the energy loss. When a exceeds 45°, the pressure loss is equivalent to the impact loss. In order to reduce the resistance of the diverging tube, the diverging angle a must be minimized, but the smaller a, the greater the length of the diverging tube. Generally, the divergent angle a is preferably 30°.
1.4 Interface and outlet of pipe and fan
When the fan is running, vibration will occur. In order to reduce the impact of vibration on the pipeline, it is best to use a hose (such as a canvas hose) where the pipeline and the fan are connected. A straight pipe is generally used at the outlet of the fan. When the elbow needs to be installed at the outlet of the fan due to the limitation of the installation position, the direction of rotation of the elbow should be consistent with the direction of rotation of the fan impeller.
The outlet airflow of the pipe is discharged into the atmosphere. When the airflow is discharged from the pipe mouth, all the energy of the airflow before it is discharged will be lost. In order to reduce the loss of dynamic pressure at the outlet, the outlet can be made into a diverging tube with a small divergent angle. It is best not to install a hood or other objects at the outlet, and at the same time minimize the airflow velocity of the exhaust outlet.
