When many manufacturers are designing their workshops, the selection of fans is only based on experience to estimate the resistance of the pipe network, which can easily lead to the selection of centrifugal fans that are too large, resulting in low operating efficiency and increased energy consumption. , the overall ventilation system technology is backward, the operating efficiency of the centrifugal fan is lower, so how to improve the efficiency of the centrifugal fan has become a very important issue.
1)Methods to improve the efficiency of centrifugal fans
As for how to improve the efficiency of centrifugal fans, there are generally two ways: one is to transform the fan, usually by using variable frequency speed regulation to improve its efficiency; the other is to use ternary flow design in the design stage of the ventilation system Theoretical high-efficiency fans, or replacing old fans with high-efficiency fans.
1. Adopt frequency conversion speed regulation to improve efficiency
The high-voltage frequency converter is used to adjust the speed of the supporting motor of the centrifugal fan. The liquid couple speed regulating mechanism is cancelled to make the motor and the centrifugal fan directly connected. The net resistance can improve the operating efficiency of the centrifugal fan by about 2% to 5%, and generally reduce the comprehensive power consumption by 1~1.5kWh/t.
2. Using high-efficiency fans to improve efficiency
Aiming at the structural defects of ordinary centrifugal fans, the high-efficiency fan adopts the “design concept of adapting to the changes of airflow in each layer of the blade section”, that is the three-dimensional flow design theory. Based on this theory, the shape of the designed centrifugal fan blades is an irregular curved surface shape, which can reduce the corresponding energy losses such as impact, boundary layer separation, friction, etc., improve the efficiency of the fan, and enhance the adaptability of the fan.
During use, the arc-line superimposed blades of the ternary flow fan are infinitely close to the airflow, which makes the flow of the airflow smoother, eliminates the eddy current, and improves the efficiency; the arc streamlined front disc also provides a basis for the improvement of efficiency; the sawtooth shape While reducing the back vortex, the rear disc reduces the axial additional force caused by the air pressure difference; the reasonable blade installation angle reduces the vortex and resistance formed by the intake air, and improves the aerodynamic performance.
2)Precautions for improving the efficiency of centrifugal fans
1. Before the transformation of the centrifugal fan, the air leakage should be controlled first, and the process operation should be optimized to achieve a stable and good production state as much as possible.
2. In the actual normal operation, the system operating conditions also change. Therefore, when selecting the centrifugal fan, most of the actual operating conditions should be in the high-efficiency area of the performance curve. How to correct the fan model and actual operating conditions? Selection is crucial to the energy-saving effect of centrifugal fans.
3. During the fan selection in the process design stage of the enterprise, the operating conditions of the centrifugal fan should be calibrated several times, and the data intervals such as air volume, air pressure, medium temperature, and dust concentration required for the normal operation of the system should be grasped as much as possible. The spare margin (5%~10%) of the centrifugal fan, but the air volume demand for extreme working conditions should not be considered in the fan selection factor.
4. The design of retrofitting centrifugal fans should minimize changes in civil foundations, fan interfaces, etc. One is to save investment and retrofit time, and the other is to prevent centrifugal fans from being retrofitted and replaced with original fans to keep production running normally and reduce failures. risk impact.
5. Since the full-pressure efficiency of the centrifugal fan after the transformation has a strong calibration and a large error, it can be converted into an agreement with the centrifugal fan manufacturer to make an intuitive assessment and settlement based on the reduced value of the motor operating power after the transformation. For example, the full-pressure efficiency of the fan after the transformation If it is less than 70%, it can be regarded as a failure of the retrofit of the high-efficiency fan.
6. After the centrifugal fan is installed with a frequency converter, if there is no special need, the inlet and outlet air volume control valves of the fan should be removed, and the air volume should be adjusted by adjusting the fan speed as much as possible to reduce the system resistance and reduce the fan consumption.