The working principle of the blower is similar to that of the centrifugal fan, but the compression process of air is usually carried out by the centrifugal force. The fan is a high speed rotation of the rotor blades, the rotor drives the air speed, the centrifugal force makes the air in the casing involutes, along the flow to the outlet of the blower involute, high-speed airflow has certain wind pressure. The new air enters from the center of the casing. The working principle of single-stage high-speed centrifugal fan is that the original motivation through the shaft to drive the impeller rotating speed, radial flow is accelerated into the airflow into the high-speed rotation of the impeller from the inlet axial, and then enters the diffuser chamber, change the flow direction and speed, the speed will be high speed rotating airflow with kinetic energy into the pressure can make the fan (potential energy), to maintain stable export pressure. Theoretically, the centrifugal blower pressure flow characteristic curve is a straight line, but because of the existence of fan internal frictional resistance loss, the actual pressure and flow characteristic curve with the increase of flow gently down, power corresponding to the centrifugal fan flow curve with the increase of flow rise. When the fan operates at a constant speed, the working condition of the fan will move along the pressure flow characteristic curve. The operating point of the fan is not only decided by its own performance, but also depends on the characteristics of the system. When the resistance of the pipe network increases, the performance curve will become steeper. The basic principle of fan adjustment is to change the fan's own performance curve or external pipe network characteristic curve to get the required condition.
Principle and characteristics of frequency control:

With the continuous development of science and technology, AC motor speed control technology is widely used. Through the new generation of full control of electronic components, with the inverter to change the speed of the AC motor to control the flow of the fan, can greatly reduce the energy consumption of the past mechanical control flow.

Energy saving principle of frequency control:
When the air volume is reduced from Q1 to Q2, if the throttle adjustment method, the operating point from A to B, the wind pressure increased to H2, shaft power P2 decreased, but not much less. If the use of variable frequency regulation, fan operating point from A to C, can be seen in the same air volume Q2, the wind pressure H3 will be significantly reduced, the power P3 with a significant reduction. The power loss of delta P = save the HQ2 value and is proportional to the area of BH2H3C. Based on the above analysis, it is known that the frequency conversion adjustment is an efficient way to adjust. The blower uses the frequency conversion to adjust, does not have the additional pressure loss, the energy conservation effect is remarkable, the adjustment air volume range 0% ~ 100%, is suitable for the adjustment scope is broad, and often in the low load operation situation. However, when the fan speed decreased, volume decreases, the pressure will be changed by the fan ratio law: Q1/Q2 = (n1/n2), H1/H2 (n1/n2) = 2, P1/P2 = 3 (n1/n2) of the shaft power were reduced to 1/2, 1/4, 1/8, this is the reason why frequency adjustment mode can be large the rate of saving. According to the characteristics of frequency conversion regulation, in the process of sewage treatment, the aeration tank always keeps 5m normal liquid
At the same time, the blower is required to carry out a wide range of flow regulation under the condition of constant outlet pressure. When the depth of the adjustment is large, the pressure drop is too large to meet the technical requirements. When the adjustment depth is small, it does not show the advantages of energy saving, but the device complex, one-time investment increased. Therefore, it is obviously not suitable for the aeration tank to maintain the 5m liquid level under the working condition.

Principle and characteristics of inlet guide vane adjustment:
The inlet guide vane adjusting device is that a set of adjustable guide vanes and inlet guide vanes are arranged near the suction inlet of the blower, and the function is to cause the air flow to rotate before entering into the impeller, which causes the twisting speed. The guide vane can rotate around the shaft, and the rotation angle of each blade means changing the mounting angle of a guide vane, so as to change the direction of the airflow entering the fan impeller.

Inlet guide vane adjustment principle:
When the blade installation angle theta = 0 DEG, the guide vane inlet flow basically no effect, air will flow into the impeller blades in radial direction. When theta > 0 DEG, inlet guide vane will enable the absolute velocity of inlet flow velocity along the circumference direction deflection angle, the inlet flow velocity with throttling effect, the pre swirl and throttling effect will cause the fan performance curve down, so that the operating point changes, the fan flow rate adjusting. Energy saving principle of inlet guide vane adjustment. When the inlet guide vane mounting angle theta = 0 DEG from 1 increased to 2 or 3 theta theta, operating point from M1 to M2 or M3; the flow is reduced from Q1 to Q2 or Q3; the shaft power reduced to 1 by P 'P' 2 or 3 'P. That profile area of power saving ratio of throttle inlet guide. In this project, the depth of the aeration tank is fixed, the blower outlet pressure to maintain a constant condition, flow control, H = Q = constant, variable, similar to the linear characteristic curve of pipe network, the blower inlet guide vane adjustment, without the change of pipe network characteristic curve can be changed by the the opening and closing angle of leaf, the curve of flow performance of the fan pressure change, the flux change is through the operating point moves to the fan characteristic curve of new changes on the implementation of the. The centrifugal fan with the way of adjusting the inlet guide vane, obtain high efficiency and wide range of performance in the partial load condition, the outlet pressure to maintain constant conditions, work flow can be varied from 50% to 100% of the rated flow range. Adjust the greater depth and power saving more. If the flow is reduced to 60% of the rated flow, the inlet guide Ye Fang