Noise, including aerodynamic noise and mechanical noise, will inevitably be generated during the operation of tunnel fans. Among them, aerodynamic noise is the main noise, whose sound pressure level is usually more than 10 decibels higher than mechanical noise. It is transmitted to the surrounding air through the inlet and outlet of the fan. Because the noise of tunnel fan is related to the structure form, air volume, total pressure and speed of the fan, the above factors should be paid attention to when seeking ways and methods to reduce the noise. Then how to reduce the noise of the fan sound source?
1. We should choose the type of tunnel fan reasonably. If it is really the case that high noise is required, then we should choose low noise fan. Under the same air volume and pressure, the centrifugal fan of the airfoil blade has less noise, while the centrifugal fan of the front plate blade has more noise.
2. The working point of the tunnel fan should be close to the high efficiency point. The higher the efficiency of the same type of fan, the smaller the noise. In order to keep the operating point of the fan in the high efficiency zone of the fan, it is necessary to avoid the use of valves to adjust the operating conditions. If a valve must be installed at the fan, the best position is 1 meter away from the fan outlet, so as to reduce noise to less than 2000 Hz. The airflow at the fan entrance should be maintained evenly.
3. The airflow speed in the pipeline should not be too high to avoid noise. The airflow speed in the pipeline shall be selected according to different requirements and relevant regulations. And we should pay attention to the transmission mode of the tunnel fan and the motor. The direct transmission noise of the fan is smaller, followed by the coupling. The seamless V-belt transmission is slightly worse. The fan shall be equipped with a low noise motor.