XinFeng Classroom | Ventilator Series: Fan Performance and Noise Control

01  

Ventilator Performance Parameters  

I. Primary Performance Parameters  

The primary performance parameters of ventilators include the following seven aspects:  

Airflow (Volume), Pressure, Gas Medium, Rotational Speed, Power, Temperature, Local Atmospheric Pressure;  

Airflow (Volume): Units include m³/h, m³/min, m³/s, (Nm³/h—standard flow rate); Pressure: Total pressure, static pressure; units include MPa, kPa, mmAq, Pa;  Gas Medium: Composition of the medium at the fan inlet;  Rotational Speed: Fan rotational speed in r/min;  Temperature: Temperature of the medium at the fan inlet and ambient temperature.  

02 

 Sources of Ventilator Noise   

    I. Aerodynamic Noise Aerodynamic noise includes rotational noise and vortex noise.

(1) Rotational noise originates from the rotating impeller.

 (2) Vortex noise stems from vortices generated by the fan, which disturb the airflow and create periodic compression and expansion cycles within the flow, thereby producing noise. II. Mechanical Noise     Mechanical noise primarily includes bearing noise from the fan, noise caused by belts and their transmission, vibration noise due to rotor imbalance, and noise generated by vibrations resulting from casing and duct installation deviations. III. Motor Noise     Motor noise is a major component of fan noise, primarily comprising electromagnetic noise, mechanical noise, and airflow noise.   

 03 

 Control of Ventilator Noise Common measures for controlling ventilator noise include: noise reduction, sound insulation, and vibration damping. I. Noise Reduction and Silencers Installing silencers at the inlet and outlet of ventilators is the primary method for noise control. Selecting appropriate silencers can reduce noise levels (A-weighted) by 20–40 decibels, corresponding to a 75–93% reduction in perceived loudness. II. Sound Insulation and Absorption     Sound insulation involves placing a barrier or shield between the noise source and a specific point, or enclosing the source to isolate noise from the working environment. This is typically achieved using sound enclosures or soundproof rooms. III. Vibration Reduction     Vibration is a primary noise source, making vibration reduction a key measure for controlling fan noise. Fan vibration reduction primarily involves two approaches:

 (1) Connecting a flexible duct section between the fan and air duct to prevent vibration transmission and radiated noise. 

(2) Installing vibration-damping components (e.g., springs, rubber isolators, or cork) between the fan and foundation to attenuate vibrations transmitted to the base. 

   04 

 Ventilator Surge Phenomenon   Surge Phenomenon: When a fan operating in a large-capacity piping system enters an unstable operating zone, significant fluctuations in flow rate and pressure may occur. This can cause severe vibration in the equipment accompanied by intense noise, a phenomenon known as surge.