How a Centrifugal Compressor Works

Continuing our series on different types of air compressors, today’s blog will feature the centrifugal compressor.  The centrifugal compressor is classified as a dynamic compressor.  Dynamic compressors are designed to work with  a continuous flow of air that has its velocity increased by an impeller rotating at a very high speed.

The centrifugal compressor works by transforming the kinetic energy and velocity into pressure energy in the diffuser.  The air passes through the inlet guide vanes being drawn into the center of a rotating Impeller with radial blades and is then pushed outward from the center by centrifugal force. This radial movement of air results in a pressure rise and the generation of kinetic energy.  The kinetic energy is also converted into pressure by passing through the diffuser.

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Sample Centrifugal Compressor

Multiple stages are required to raise the pressure to a sufficient level for typical industrial plant requirements.  Each stage takes up a part of the overall pressure rise of the compressor unit.  Depending on the pressure required for the application, a number of stages can be arranged in a series to achieve a higher pressure.

The most common centrifugal air compressor has two to four stages to generate pressures of 100 to 150 PSIG and incorporates a water cooled inter-cooler and separator between each stage to remove condensation and cool the air prior to entering the next stage.

Centrifugal compressors are the near middle of the road regarding efficiency, their typical operating cost is 16 to 20 kW/100 CFM.  The most efficient compressor type is the double-acting reciprocating and costs 15 to 16 kW/100 SCFM and the least is the Sliding Vane which costs 21 to 23 kW/100 SCFM.

Advantages of the centrifugal air compressor:

  • Up to 1500 HP systems are available
  • Price per HP drops as system size increases
  • Supplies lubricant-free air
  • Special installation pads are not required for installation

Disadvantages of the centrifugal air compressor

  • Costs more Initially
  • Requires specialized maintenance
  • Due to high rotational speeds (can exceed 50,000 RPM) precision high speed bearings and vibration monitoring are required

EXAIR recommends contacting a reputable air compressor dealer in your area to discuss your volume and pressure requirements to determine the best size & type air compressor for your needs.

Regardless of the type of air compressor you have, EXAIR’s Intelligent Compressed Air Products® can minimize your compressed air consumption, potentially reducing the size of compressor needed, reduce noise and still deliver powerful results!   If you would like to discuss highly efficient and quiet point of use compressed air products or any EXAIR product, we would enjoy hearing from you. 

Steve Harrison
Application Engineer
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Image Courtesy of  the Compressed Air Challenge

Spills & The Not So Easy Way To Clean Them Up

Before I worked for EXAIR, I worked for a CNC manufacturer/ distributor here in Cincinnati.  We would constantly have machines in our showroom filled with cutting fluid and running demonstrations, training or test cuts for our customers.  The bad part was that these never happened in the same week, sometimes not even in the same month.  So to keep the machines clean we would have to empty the coolant after we were done.   The way we would always do this was with the EXAIR Reversible Drum Vac.

RDVFamily_300px

Our unit was not exactly treated with the utmost respect.  It would get thrown on a shelf or in a drawer of a tool box for weeks on end, taken to shows, on customer visits, and even left on a drum full of coolant.  The best part is that it always worked.  The unit we had, was over ten years old when I worked there and I had been with them for 5 years, it had never needed any service.   No matter what we did, the unit always pulled through and took up less room than a regular electric vacuum.

The event that sparked this chain of thoughts was a small (1 entire quart) spill of fork oil in my garage earlier this week.  As I was working on my race bike I accidentally knocked over a freshly opened quart of fork oil and didn’t notice until it was all drained right underneath of my motorcycle.   Unfortunately, I don’t have a Reversible drum Vac at home to quickly suck up the spill before it sets into the concrete so I started cleaning it with paper towels and kitty litter.   Now I have this giant pile of dusty oil soaked stuff in the middle of the garage that has been sitting for 3 days to make sure it is all absorbed.   If I had even had a Mini Reversible Drum Vac I would have been able to utilize my air compressor and suck up the spill, instead I now have an entire trash bag of mess to clean up and dispose of.

spill

This happens more often than one would think in car garages, and performance shops.   Rather than running for the kitty litter, give the EXAIR Reversible Drum Vac a test and find out how much easier it is to suck up that coolant or oil spill straight into a 5, 30, 55 or 110 gallon drum.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF