- General

Design Considerations and Applications For Industrial Blowers

Industrial blowers are mechanical devices that can move gas or air and are used in several industrial processes as well as applications that require enhanced gas or airflow. Increased airflow is achieved by the rotation of a fan wheel consisting of several fan blades. This fan wheel accelerates the air entering the blower housing and pushes it out through the housing exit, thus supplying air to the applications. The fan wheel is typically rotated by an electric motor or a turbine. There are two types of blowers, centrifugal and axial, which are classified based on the direction of the airflow. Based on your application, a variety of blower design options is available, and the blower should be selected such that it offers long and efficient services.

Design Aspects

There are several aspects to be considered while designing industrial blowers, with the primary focus being on the application that the blower is being selected for. Specific flow and pressure requirement of the application are the primary factors taken into account for blower design. Another factor to be considered is the application’s airflow characteristics, such as whether the blower will operate in an abrasive environment. A typical element in designing the centrifugal machines is to operate the units with operating pressure in a narrow range. While designing a blower, it is necessary to ensure that eddies and turbulence in the blower housing are also restricted, consequently keeping blade wear to a minimum. Large and fast fans result in increased force acting on the rotating structures; as a consequence the blower should also be designed such that impulsive resonant frequencies and excessive stress are eliminated.

Blower Selection and Installation

Generally, the selection of blowers is based on its longevity, performance, and efficiency. However, the noise characteristics of the blower are also taken into consideration, especially in cases where the blowers are used in HVAC systems. While installing the blower, it is important that it be installed on a rigid base to prevent resonance.

Blade Selection

Various blade types and configurations are available for industrial blowers, be it a centrifugal or an axial fan.

The primary blade configurations for a centrifugal blower are radial, forward inclined, and backward inclined. All of these blade configurations have pros and cons, and they should be selected based on the application.

Radial fans offer high pressure, high speed, and low volume airflow, making them ideal for pneumatic conveying systems as well as vacuum cleaners. In addition, its low sensitivity to solids also makes it particularly suited for applications with particulate-laden gas streams. Forward inclined fans are typically available with both flat and curved blades. These fans are ideal for low pressure, high volume applications. Backward inclined fans, on the other hand, offer better efficiencies and are better disposed to handle airflows with moderate particulate loading. They are particularly ideal for applications that require high pressures and medium flow.

Axial fans are available with variable pitch blades. In this type of fan, the pitch of the blade is periodically changed to suit the pressure and volume requirements of the application. Another variation of this type is the “on-the-fly” variable pitch, in which the blade pitch can be changed while the rotor is rotating. This option offers axial fans a versatility that makes them ideal for a broad spectrum of airflow applications.

Flow Control

In certain applications, flow control will also be a requirement. In such cases, a method of flow control must be selected. The two primary methods of controlling flow are speed variation and industrial dampers. Speed variation is achieved by controlling the speed of the driver. For this purpose, use an adjustable frequency AC controller, a hydraulic variable speed drive unit, plus a DC motor and drive. Industrial Dampers, on the other hand, control flow by restricting airflow. There are a variety of dampers available for use with industrial blowers, including radial inlet dampers, louvered inlet box dampers, and discharge dampers.