Customizing Centrifugal Fans for Desired Airflow

Centrifugal fans are designed to serve specific requirements of industrial applications in which they are installed. The actual demand for pressure and the flow of air depends on the operational requirement and the designed capacity of the fan. Quite often, industrial applications require wide variety of operational conditions with a change in the airflow or fan speed. A typical centrifugal fan has the capability to increase the speed of air stream entering into the fan through an impeller, and accelerate it radially to the outlet changing its direction by 90°. Many fan systems need external mechanisms that can alter the designed fan capacity to achieve optimum efficiency and system performance. It can be either increase or decrease in the volume of airflow to make it appropriate for the specific operational needs. Industrial applications implement several methods to achieve this desired change in the airflow.

Some are mentioned below –

Outlet Dampers
Dampers and louvers can be located at the fan inlet or outlet to control or block the flow of air. They act as a resistance to generate the required flow without actually changing fan speed. When compared to louvers, damper controls that are inside the fan ducts are more efficient in regulating the air volume. This is mainly because damper plates are movable or adjustable whereas louvers are fixed with no control over the air movement.

Variable inlet guide vanes
Guide vanes are typically designed to control the inlet airflow and increase the power efficiency. Centrifugal fans with back ward inclined aerofoil or flat blade wheel types mostly use inlet guide vanes for altering the amount of air or gas entering into the fan inlet. The curved sections of the variable inlet guide vanes impart a pre-spin and change the angle of the air that is entering into the fan housing. This results in controlled air volume, lower static discharge pressure and reduced input power requirement.

Variable speed drives
Adjustable or variable speed drives are mainly intended for increased process control capability and energy conservation. Today, various types of mechanical, hydraulic or electronic drives are available that can be used as variable speed drives in industrial applications. When a system demands for adjustment of air flow, then varying the fan operation speed is an efficient option for energy savings. This type of speed control is more viable for systems that have frequent air or gas flow variations. Adjusting the operation speeds not only controls the flow or air volume but also improves the performance of the fan.

Multiple fan systems
If low flow rates are required for long time intervals, then using more than one fan in series or parallel operation is more economical. By combining multiple fan systems one can achieve the desired flow rate without actually altering the fan size or capacity.

The decision whether to connect centrifugal fans in series or parallel depends on the operational conditions of the system and the requirement of air volume flow. For higher degree of flow rate flexibility, centrifugal fans can also be equipped with the above mentioned control mechanisms like damper controls, inlet guide vanes, variable speed drives etc.

Based on the specific requirements of airflow rate, volume, pressure and efficiency, centrifugal fans are provided with customized solutions to cater the needs of various industrial applications.