Many industries and applications are powered by the movement and compression of air; that’s why air compressors, blowers, and vacuum pumps are so essential to businesses! Today we’re focusing on centrifugal blowers, a type of blower that operates via dynamic compression and are well-suited for processes in a variety of industries, including wastewater treatment, pneumatic conveying, flue gas desulphurization, and fermentation.
Centrifugal Blowers: How They Work
Dynamic compressors work at a constant pressure, and their performance is impacted by external conditions, such as changes in inlet conditions. Air is drawn between the blades on a rapidly rotating compression impeller as it accelerates to a high velocity. Subsequently, the gas is discharged through a diffuser, where the kinetic energy is transformed into static pressure. Depending on the main direction of the gas flow, these compressors are called radial or axial compressors, all of which are designed for large volume flow rates.
Types of Centrifugal Blowers
Because centrifugal blowers operate with pressure and flow rate as dependent variables, they operate best as base load machines or in applications with constant pressure. Currently, two different designs of the modern centrifugal blower are in common use:
- Multistage Centrifugal Blower. The multistage centrifugal blower (MSCB) is usually coupled directly with an induction motor driveshaft, resulting in a slower operating speed. The design principles are fairly simple: for more flow, increase the impeller diameter; for more pressure, increase the number of impellers (stages). Like all centrifugal machines, the impeller configuration has a large effect on the performance of a MSCB. A MSCB can have two to 11 stages and any number of impeller geometries to create the desired flow and pressure curve.
- Turbo Blowers. The turbo blower is ideal for low-pressure applications requiring up to 2 bar (29psi). They’re demand-based, offer high efficiency over a wide range of flows, and have lower maintenance requirements. Two variations of turbo blowers include the integrally geared turbo blower and the high speed turbo blower.
- Integrally Geared Turbo Blower. The integrally geared turbo blower (IGTB) is driven by an induction motor via a speed-increasing gearbox. Although the motor rotates at only 1,800 or 3,600 RPM, the blower impeller rotates as fast as 30,000 RPM to produce the desired flow and pressure. The IGTB uses inlet guide vanes and variable diffuser vanes to control the air flow and pressure.
- High Speed Turbo Blower.
- Magnetic bearing turbo blowers equipped with motors are extremely reliable and efficient. These turbo blowers have a high-speed drive and work vibration-free and without a gear; instead, the motor impeller is flanged directly onto the shaft. The elimination of a gear enables excellent efficiency and reduces maintenance costs.
- Air bearing turbo blowers are also available. This technology is relatively old with occasional improvements, but also have lower initial investment costs and a compact design. Frequency converter, control and high-speed drive can also be integrated.
- Fun Fact: Both the air bearing and magnetic bearing turbo blowers use high speed permanent magnet motors controlled by variable frequency drives that allow the impellers to turn up to 60,000 RPM in order to create the desired air flow and pressure.
Which Centrifugal Technology Should You Choose?
The answer? It’s wholly dependent on process! For example, let’s take wastewater treatment. The multistage centrifugal blower (MSCB) offers the most versatility due to its ability to convey digester gas as well as air; it also offers the widest flow range due to the numerous configurations available. The integrally geared turbo blowers offers the largest flow rates and, thus, is not suitable for use in small plants. The high-speed turbo blower offers the greatest potential in industrial wastewater applications due to its small footprint, high efficiency, and integrated control system.
Also keep in mind that centrifugal blowers particularly show their advantages where high-volume flows are required. They can work more efficiently in this scenario than screw blowers, at least with a relatively constant compressed air requirement, when little has to be regulated. Screw blowers are usually more efficient when there are more fluctuating requirements and the resulting large control range.
When choosing a centrifugal blower technologies, it’s best to discuss your application’s unique needs and requirements with a trusted low-pressure blower expert. Give us a shout today at www.atlascopco.com/blowers-usa!
