According to the theory of hydrodynamics, the flow process of gas will be accompanied by loss. For example, after the gas flows through the throttling device, the pressure of the air flow will be reduced accordingly, that is, they lose the active work of the fan. Because all this happens in the process of gas conveying by the fan, that is, the energy of the fan is wasted.
The operating point of the fan is the intersection of the performance curve of the fan at a certain speed and the resistance characteristic line of the pipe network. During the actual operation of the fan, it does not always stay at the design working condition point. It will change with the needs of users or changes in external conditions, that is, the fan actually works under variable working conditions. In order to make the air pressure or air volume of the fan reach a certain target value, it is necessary to artificially control the fan or pipe network, also known as regulation. Through effective regulation, it can not only meet the requirements of production for flow or pressure, but also save energy to a certain extent under the condition that the fan can work stably. In short, the purpose of regulation is to meet the performance requirements, expand (stabilize) working conditions, save energy and prevent surge.
Different adjustment methods of fan can achieve the same purpose, but the energy-saving effects are different.
According to theoretical analysis and practical proof, the following four conclusions can be drawn.
(1) for blowers and compressors, the outlet throttling regulation mode consumes the most power. Although the relative flow QR (the ratio of actual flow Q to design flow Q0) decreases, the power also decreases accordingly. For example, when q = 0.65q0, the corresponding power is reduced to about 80%, but compared with other regulation methods, energy consumption still occupies an important position.
(2) if the relative flow changes little (or the regulation depth is small), there is little difference in power consumption among several regulation modes. That is, the regulation mode has little impact on the energy-saving effect, or even does not save energy, but consumes more power due to the existence of the regulation device (such as hydraulic coupler).
(3) generally speaking, the greater the adjustment depth, the more significant the energy-saving effect. Therefore, we should carefully choose the regulation mode in order to obtain benefits.
(4) the speed regulation curve is close to the ideal curve. Therefore, the variable speed regulation mode is superior, especially the energy-saving scheme of variable frequency motor speed regulation is better, but the variable frequency device needs to be added. It is recommended to actively try out frequency conversion speed regulation with small and medium capacity; Due to the high price of high-capacity and high-voltage variable frequency speed regulation device, the choice should be determined by comprehensive comparison in combination with specific conditions. In short, we should not only consider the regulation performance, but also consider the initial investment, reliability and economy of the equipment, and comprehensively evaluate the advantages and disadvantages of the regulation mode.