The air intake mode of the ducted centrifugal fan has two types: single side air intake (single suction) and double side air intake (double suction). Single-suction fans are divided into two types: single-side single-stage impeller and single-side double-stage impeller. In the same situation, the wind pressure generated by the two-stage impeller is twice that of the single-stage impeller. The double-suction single-stage fan has a double-side air intake and single-stage impeller structure. Under the same circumstances, the flow generated by this fan is twice that of single suction. Under special circumstances, the air inlet of the centrifugal fan is equipped with an air inlet chamber, which has five different inlet angle positions according to the "left" or "right" rotation direction of the impeller.
It is not economical for the fan to use physical methods to narrow the gap. It requires too many parts to be replaced, or it is uneconomical to scrap the machine. We try to use chemical methods to narrow the gap, that is, evenly fill the superglue JZ-AB in the gap δ. The glue has high bonding strength, resistance to water, oil, acid, alkali, humidity and heat aging, wide application temperature, non-toxic, non-flammable, long storage period, suitable for bonding various gold, silver, copper, iron, aluminum, glass, etc. , It is widely used in machinery manufacturing, maintenance, agricultural machinery and furniture.
The structure of the ducted centrifugal fan is relatively simple, and the manufacturing is also relatively convenient. The fan consists of an impeller, a casing, a transmission part, and a support part. The impeller consists of a shaft disc, a rear disc, a front disc and blades. The impeller and the main shaft are collectively called the rotor. The front disc of the impeller generally has a straight front disc, a tapered front disc and an arc front disc.
In terms of gas flow trajectory, the impeller with a flat front disc does not conform to the gas flow trajectory. The blade flow path at the outer diameter of the impeller is much larger than the blade flow path at the inner diameter of the impeller. Therefore, not only is there a difference in the airflow velocity of the blades, but also the airflow in the blade flow path at the outer diameter of the impeller cannot be filled, resulting in eddy currents, power consumption, and reduced fan efficiency. However, in the forward impeller, in order to be simple and convenient to manufacture, some types of ventilators still use this kind of front disc.
The gas flow trajectory of the tapered front disc is better than that of the flat front disc, but the cross-section of the flow path between the blades still cannot achieve equal or uniform diffusion of all parts. Therefore, there is still leakage in the blade flow channel, which affects the efficiency of the fan. Although the manufacturer has added more processes than the flat front plate, it is still relatively simple and convenient.
The arc of the arc-shaped front disc is determined according to the equal cross-section or equal-diffusion cross-section of the flow path between the blades. Therefore, the airflow in the blade channel is constant or decelerated, and there is no leakage flow in the blade channel under normal circumstances. Therefore, the efficiency of the impeller of the arc-shaped front disc is generally higher than that of the flat front disc and the conical front disc, but the manufacturing is more complicated than the first two front discs. However, from an economic point of view, it is more advantageous to use an arc-shaped front disc for mass-produced ducted centrifugal fans or large fans.
