Centrifugal Air Blowers (or Centrifugal Fan) is a type of air handling device which pulls air with a small inlet, and expels it at a 90 degree angle difference at the exit. The main difference between a Centrifugal Air Blower and an Axial Fan is the relative direction which the air is expelled. The Axial fan pushes air out at the same axial direction that it enters the device. The Centrifugal Air Blower’s impeller is designed to suck air in at the middle of the wheel, and force it out through an opening at the circumference of the impeller’s wheel.
Blowers are designed for creating large pressure increases from small inlets. So a pressure difference between the internal and external part of the wheel causes air to be pulled from the eye of the impeller. Centrifugal Blowers are perfect for industrial and large applications as they create higher pressures and are able to overcome strong resistances within ducts and air handling equipment. Generating a constant volume of air or CFM, the Centrifugal Blower is the most popular fan or air moving device used in HVAC systems today. It has become a cost-effective solution due to its simple construction and the small amount of moving parts. A strong advantage of Centrifugal Air Blowers is that it can be used to transport materials such as grains and gas. Axial Fans are not recommended for carrying material due to its design.
Centrifugal Blowers and Parts
Centrifugal Blowers consist of an Inlet, an Outlet, a Shaft, the Housing and an Impeller.
The Inlet is where the air is sucked into the blower. The inlet is usually smaller than the outlet and it is situated at the core of the impeller. This is where the low pressure is created when the blower operates causing the air, gas or particle to be sucked in.
The Outlet is located at the circumference of the Impeller and is used to discharge the gas or particle from the blower.
The Shaft is the device used to rotate the fan. The shaft connects to a Generator, variable drive or belt which transfers torque to the impeller. The shaft consists of bearings which are usually water-cooled.
The Housing contains all the moving parts, and it is used to direct particle flow and maintain the pressure differences needed to allow the fan to operate.
The Impeller is the main operating and rotating part which has the blades in the required configuration.
Centrifugal Air Blower Blades
The blades on the impeller can be constructed in three ways to provide different aspects for suitable applications. The blades can be Forward-Curved (FC), Backward-Curved (BC) or Radial. If your aren’t sure which suits your needs contact Custom Fans of Australia and well will help solve your needs.
- Forward-Curved blades curve in the same direction that the material or air is travelling. These blades are suitable for situations that require high speeds, high volumes and low pressures.
- Backward-Curved blades curve in the opposite direction of the flow. They are highly efficient and robust, but they require more maintenance due to the buildup of solid particles that may occur between the fins due to the direction of the blade design. Backward Curved blades operate at higher speeds and still require less power to operate due to its efficient design. They are great for High Static operations with medium speed and High Efficiency.
- Radial Blades extend to the circumference from the core with a straight line. Its design is the simplest of the three. The design of its straight line blades means that it will have the least amount of build of solids on the blades. Radial Blades are great for moving grains and are even popular in simple solid movement applications such as the domestic vacuum cleaner.
We can conclude with the basic operation of a Centrifugal Air Blower. A generator, belt or Variable drive spins a shaft which has an impeller within the housing on the other end of the shaft. The Impeller consists of blades or ribs which control the direction the gas or particles flow. The particles are sucked through the inlet at the eye of the impeller and expelled through the outlet at the circumference into a ventilation system. This is the concept of a centrifugal air blower.