In certain cases, specific operational needs require adjusting the airflow of centrifugal fans to meet desired conditions. Currently, two primary methods are used for this purpose: air damper adjustment and inlet vane adjustment. Each method has distinct effects and operational principles:
- Air Damper Adjustment
- Outlet Damper Adjustment: This approach alters the characteristics of the duct system rather than the fan itself. The airflow adjustment range is typically within all operating points on the fan’s rated performance curve. However, as this method involves artificially increasing the resistance in the duct system, additional resistance from partially closed dampers consumes pressure, resulting in poor energy efficiency.
- Inlet Damper Adjustment: When the damper is placed on the fan’s suction side, its adjustment principle mirrors that of the outlet damper. When placed on the discharge side, it changes the fan’s performance curve by adjusting the inlet pressure. This method is generally more energy-efficient.
- Spiral Damper Adjustment
By altering the outlet area of the fan, this method modifies the fan’s characteristics. However, compared to other methods, the power consumption changes little, and the energy-saving effect is not significant.
- Inlet Vane Adjustment
This method adjusts the orientation of the inlet vanes to modify the airflow direction entering the impeller, thereby altering the fan’s performance curve.
- Positive Inlet Vane Adjustment: Adjusts airflow to achieve all operating points below the fan’s rated performance curve when the inlet vane angle is set to zero.
- Negative Inlet Vane Adjustment: Increases the fan’s pressure and airflow but with a limited adjustment range.
Key Considerations:
Both air damper and inlet vane adjustments can be used under all conditions along the rated performance curve. These methods shift the surge point toward lower flow rates, making them widely used in constant-speed centrifugal fans. When selecting an adjustment method, it is essential to consider the fan’s structure and operational requirements to ensure optimal performance without damaging the fan. Proper adjustment improves airflow to meet specific work requirements efficiently.
