一个完整的除尘系统包括吸尘罩、通风管道、除尘器、风机四个部分。通风管道(简称管道)是运送含尘气流的通道，它将吸尘罩、除尘器及风机等部分连接成一体。管道设计是否合理，直接影响到整个除尘系统的效果。因此，必须全面考虑管道设计中的各种问题，以获得比较合理、有效的方案。

A complete dedusting system includes four parts: dust suction hood, ventilation pipe, dust collector and blower. Ventilation pipe (short pipe) is a channel for conveying dust laden airflow. It connects the dust hood, dust collector and fan and so on. Whether the pipeline design is reasonable will directly affect the effect of the whole dust removal system. Therefore, all kinds of problems in pipeline design must be considered comprehensively, so as to get a more reasonable and effective plan.

1、管道构件

1. Pipe components

1.1 弯头

1.1 elbow

弯头是连接管道的常见构件，其阻力大小与弯管直径d、曲率半径R以及弯管所分的节数等因素有关。曲率半径R越大，阻力越小。但当R大于2～2.５d时，弯管阻力不再显著降低，而占用的空间则过大,使系统管道、部件及设备不易布置，故从实用出发，在设计中R一般取1～2d，90°弯头一般分成4～6节。

Elbow is a common component connecting pipes, and its resistance is related to factors such as the diameter of the elbow D, the radius of curvature R, and the number of nodes in the elbow. The greater the radius of curvature R, the smaller the resistance. But when the R is greater than 2 to 2.5D, the pipe resistance of the pipe is no longer significantly reduced and the space occupied is too large, so that the system pipes, parts and equipment are not easy to be arranged. Therefore, from the practical point of view, in the design, the R usually takes 1 to 2D, and the 90 degree elbow is generally divided into 4~6 sections.

1.2 三通

1.2 three links

在集中风网的除尘系统中，常采用气流汇合部件——三通。合流三通中两支管气流速度不同时，会发生引射作用，同时伴随有能量交换，即流速大的失去能量，流速小的得到能量，但总的能量是损失的。为了减小三通的阻力，应避免出现引射现象。设计时最好使两个支管与总管的气流速度相等，即V1=V2=V3，则两支管与总管截面直径之间的关系为d12+d22=d32。

In the dust collecting system of the centralized ventilation network, the air flow confluence component -- the three links is often used. At the same time, the velocity of air flow in the two branch of the three joint is different, and the ejection effect will occur at the same time. At the same time, with the energy exchange, that is, the flow velocity loses energy and the flow velocity is small, but the total energy is lost. In order to reduce the resistance of the three way, the ejection phenomenon should be avoided. At the time of design, it is better to equate the air velocity between the two branches and the main pipe, that is, V1=V2=V3, and the relationship between the two branch tube and the section diameter of the main pipe is d12+d22=d32.

三通的阻力与气流方向有关，两支管间的夹角一般取15°～30°，以保证气流畅通，减少阻力损失。三通不能采用T形连接，因为T形连接的三通阻力比合理的连接方式大4～5倍。

The resistance of the three way is related to the direction of the air flow. The angle between the two branches generally takes 15 to 30 degrees to ensure smooth flow and reduce resistance loss. The T connection can not be used for the three way connection, because the resistance of the three way connection of the T connection is 4~5 times larger than that of the reasonable connection mode.

另外，尽量避免使用四通，因为气流在四通干扰很大，严重影响吸风效果，降低系统的效率。

In addition, avoid using four links as far as possible, because airflow has great interference in the four way, which seriously affects the suction effect and reduces the efficiency of the system.

1.3 渐扩管

1.3 diffused tube

气体在管道中流动时，如管道的截面骤然由小变大，则气流也骤然扩大，引起较大的冲击压力损失。为减小阻力损失，通常采用平滑过渡的渐扩管。渐扩管的阻力是由于截面扩大时，气流因惯性作用来不及扩大而形成涡流区所造成的。渐扩角а越大，涡流区越大，能量损失也越大。当a超过45°时，压力损失相当于冲击损失。为了减小渐扩管阻力，必须尽量减小渐扩角a，但a越小，渐扩管的长度也越大。通常，渐扩角a以30°为宜。

When the gas flows in the pipeline, such as the section of the pipeline suddenly changes from small to large, the air flow also suddenly expands, causing a greater impact pressure loss. In order to reduce the resistance loss, the gradual transition tube with smooth transition is usually used. The resistance of the diffuser is due to the expansion of the airflow due to the inertia effect. The larger the expansion angle, the larger the eddy region, the greater the energy loss. When a exceeds 45 degrees, the pressure loss is equivalent to the impact loss. In order to reduce the resistance of the diffuser, the A should be reduced as much as possible, but the smaller the A is, the larger the length of the expanding tube will be. Usually, the A is 30 degrees.

1.4 管道与风机的接口及出口

1.4 the interface and exit of the pipe and fan

风机运转时会产生振动，为减小振动对管道的影响，在管道与风机相接的地方最好用一段软管(如帆布软管)。在风机的出口处一般采用直管，当受到安装位置的限制，需要在风机出口处安装弯头时，弯头的转向应与风机叶轮的旋转方向一致。

When the fan is running, it will generate vibration, so as to reduce the impact of vibration on the pipeline. It is better to use a hose (such as canvas hose) in the place where the pipeline is connected with the fan. In the outlet of the fan, the straight pipe is usually used. When the installation position is restricted, the elbow should be installed at the outlet of the fan. The turning of the elbow should be the same as the rotating direction of the fan impeller.

管道的出口气流排入大气，当气流由管道口排出时，气流在排出前所具有的能量将全部损失掉。为减少出口动压损失，可把出口作成渐扩角不大的渐扩管，出口处最好不要设风帽或其它物件，同时尽量降低排风口气流速度。

The outlet air flow of the pipeline is discharged into the atmosphere. When the airflow is discharged from the outlet of the pipeline, the energy of the air stream before it is discharged will be completely lost. In order to reduce the loss of dynamic pressure on the outlet, the outlet can be made into a diffused tube with small increasing angle. It is best not to set the hood or other objects at the exit, and at the same time reduce the air flow speed of the exhaust air.