In industrial production, boiler combustion is inseparable from the use of air supply and induced draft fans. Most air supply fans and induced draft fans use centrifugal fans. Compared with small centrifugal fans, large centrifugal fans used in boilers need one more air intake box. Components, what is an air intake box? What does the air intake box do?
1) The role of the centrifugal fan air intake box
1. What is an air intake box?
The centrifugal fan air intake box is also called the air intake chamber. The outlet is connected to the inlet of the air collector. It is mainly a structural part welded by two side plates and a circle plate. There are many structural forms, but the basic design principles are the same. The airflow energy loss is small, and the airflow can enter the axial direction smoothly and uniformly; it has sufficient rigidity and strength to prevent excessive deformation and vibration. Generally, it is only used on large or double suction centrifugal fans, and a manhole door is opened at a suitable position of the air intake box, so that personnel can install and inspect it and check the use of the impeller inlet.
2. The role of the air intake box
The role of the centrifugal fan air inlet box is to guide the airflow from radial to axial and isolate the bearing and the gas for easy maintenance: on the one hand, when the air inlet needs to be turned, installing the air inlet box can improve the inlet flow condition and reduce the uneven airflow caused by The flow loss caused by entering the impeller; on the other hand, the installation of the air inlet box can make the bearing installed outside the casing of the fan, which is convenient for installation and maintenance, and is more favorable for the working conditions of the bearing of the boiler induced draft fan. In thermal power plants, the boiler feed, induced draft fan and powder discharger are all equipped with air intake boxes.
2)the size requirements of the centrifugal fan intake box
The geometric shape and size of the air inlet box of the centrifugal fan have a very obvious influence on the flow state of the airflow after entering the fan. If the structure of the air inlet box is unreasonable, the resulting resistance loss can reach 15% to 20% of the full pressure of the fan. After testing, it is known that when determining the geometry and size of the air intake box, the following points should be paid attention to:
1. The ratio of length to width of the inlet end face of the intake box should be 2~3.
2. The ratio of the cross-sectional area of the intake box to the inlet area of the impeller is generally 1.7~2.0.
3. The shape of the air intake box has a great influence on the resistance value.