Centrifugal fan belongs to a kind of negative pressure fan. Through negative pressure at the air inlet, the gas can be sucked into the fan impeller and then thrown out through the air outlet. In general, there is only one air inlet, but there are also double air inlets, that is, double suction. Compared with the single-suction type centrifugal fan, what are the advantages and disadvantages of the double-suction type centrifugal fan?
1)Advantages of double suction centrifugal fans
In order to more directly reflect the characteristics of the double-suction centrifugal fan, the various situations introduced here are compared under the condition that the performance parameters of the two centrifugal fans are the same, and the operating environment is also the same. The advantages of double suction centrifugal fans are as follows:
1. Due to the large flow coefficient of the double-suction centrifugal fan, its impeller diameter is smaller than that of the single-suction type, and the rotating torque of the rotor is also reduced, which can reduce the power of the starting motor and shorten the starting time of the fan. It is extremely important for large centrifugal fans for ventilation.
2. The impeller diameter of the double suction centrifugal fan is small, which makes the manufacture, transportation and installation more convenient.
3. The air flows into the double suction impeller from both sides of the impeller, and the bearing load on both sides is the same, which can basically eliminate the axial force on the impeller. Single suction centrifugal fans require a thrust bearing and a heavy duty bearing close to the impeller.
4. The double-suction centrifugal fan adopts double-support structure and has high operation reliability.
2)Disadvantages of double suction centrifugal fans
Although the double suction centrifugal fan is particularly advantageous, it also has its disadvantages in other aspects:
1. In the case of free air intake, the double suction centrifugal fan must have a shaft passing through the impeller, and the shaft must be supported on the bearing seats on both sides, which brings certain obstacles to the air inlet.
2. When the air inlet needs to be connected to the pipeline, the double suction centrifugal fan must design two air intake boxes and connect them, and in most cases, the bearing must be installed in the air intake box. Therefore, the double suction centrifugal fan will produce many operating defects.
3. Since the double-sided air intake device is much more expensive than the single-sided air intake device, especially when it is used for mine ventilation, a backup fan must be installed, and when the fan is required to be able to reverse the wind, the intake curve will be closed. It is more complicated, so the double suction centrifugal fan is higher in cost.
4. When the intake box and the intake curve are installed, the efficiency of the double-suction centrifugal fan will be reduced by 3%~5% compared with the single-suction centrifugal fan due to the increase of fan loss.
5. Under the condition that the air inlet box is installed, the length of the main shaft of the double suction centrifugal fan is longer. In order to overcome the lateral vibration of the shaft, the diameter of the shaft needs to be increased, which leads to an increase in the mass of the shaft.