"Axial Fan" by changing the speed to change the performance curves of pumps and fans. Principle: According to the scaling law. Advantages: speed changes, constant efficiency, best economy. When the fan speed from n1 n2 promoted or reduced n3, changes in the performance curve. Fan working speed increases, the flow rate, total pressure increases; conversely flow total pressure decrease. Regulation of pipeline characteristic shift change, there is no additional regulation resistance, regulate the economy is high, is the ideal pump and fan adjustment method. However, you must use the shift variable-speed control of the prime mover or additional transmission, increased investment in equipment and operation and maintenance costs. Therefore, this adjustment method is mainly used to adjust more frequently large and medium-sized pump or fan.