The outer rotor EC centrifugal fan is essentially a var […]
The outer rotor EC centrifugal fan is essentially a variable flow and constant pressure device. When the speed is constant, the pressure-flow theoretical curve of the external rotor EC centrifugal fan should be a straight line. Due to internal losses, the actual characteristic curve is curved. The pressure generated in the outer rotor EC centrifugal fan is greatly affected by changes in the intake air temperature or density. For a given intake air volume, the highest intake air temperature (lowest air density) produces the lowest pressure. For a given pressure and flow characteristic curve, there is a power and flow characteristic curve. When the blower is running at a constant speed, for a given flow rate, the required power increases as the intake air temperature decreases.
The working principle of the external rotor EC centrifugal fan is basically the same as that of the turbo compressor, except that the gas flow rate is low and the pressure changes little. Generally, there is no need to consider the change of the gas specific volume, that is, the gas is treated as an incompressible fluid.
Outer-rotor EC centrifugal fan is based on the principle of converting kinetic energy into potential energy, using a high-speed rotating impeller to accelerate gas, then decelerate, change the flow direction, and convert kinetic energy into potential energy (pressure). In the single-stage outer rotor EC centrifugal fan, the gas enters the impeller from the axial direction, and changes to the radial direction when the gas flows through the impeller, and then enters the diffuser. In the diffuser, the gas changes the direction of flow to cause deceleration, which converts kinetic energy into pressure energy. The increase in pressure mainly occurs in the impeller, followed by the expansion process. In the multi-stage outer rotor EC centrifugal fan, a refluxer is used to make the air flow into the next impeller, generating higher pressure.
Outer-rotor EC centrifugal fan blades can be divided into three types: backward bending, forward bending, and radial according to the size of the outlet installation angle. The bending direction of the backward-curved blades is opposite to the direction of rotation of the impeller, and the outlet installation angle is less than 90 degrees; the exit direction of the radial blades is radial, and the outlet installation angle is equal to 90 degrees; the bending direction of the forward-curved blades is the same as that of the impeller. The outlet installation angle is greater than 90 degrees.
External rotor EC centrifugal fan can be made into two types of right-handed and left-handed. Viewed from the side of the motor: the impeller rotates clockwise, which is called a right-rotating fan; when it rotates counterclockwise, it is called a left-handed fan.
In summary, the external rotor EC centrifugal fan is a variable flow and constant pressure device. Its working principle is similar to that of a turbo compressor, but the gas flow rate is lower. It follows the principle of transforming kinetic energy into potential energy, accelerating the gas to complete its function. The blades of the outer rotor EC centrifugal fan also have different types, and the rotation method is also different.