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Why I believe in the High Speed Turbo Air compressor Technology

Why I believe in the High Speed Turbo Air compressor technology as the future Technology for the production of Compressed Air.

Why I believe in the High Speed Turbo Air compressor technology as the future Technology for the production of  Compressed Air.

The high speed Turbo (HST) technology is for me a 30 years journey.

Already during my Master in Mechanical Engineering at the University of Ghent, I was involved with High speed technology.  I did my master thesis on the development of a simulation program for the calculation of the static and dynamic behaviour of hydrostatic air-bearings with quadratic cavities.

After graduating in 1990 and starting my professional career, I joined a  project to develop Air-bearings for a high speed spindle, running at 50 000 rpm, at  a research center in Lausanne Switserland.   High precision air bearings could take the normal load but no shock load.  One year later, I joined a larger project, a joint development of a team in the US and a German team, to develop a liquid cooled High speed turbo 800kW.  The project took years, but was finally stopped because of lack of suitable frequency converters.

During the beginning of the nineties, only BiPolar Transistors were available, switching at 3kHz and the IGBT switching at 20kHz, were starting to become available on the market.  We build the first IGBT frequency converter even before the reputed Motor manufacturers had a frequency converter available with IGBT, allowing to switch the PWM on high frequency to improve the Sinusoidal current  This was needed to reduce the heat generated in the spindle by the losses.

The big challenge of a High speed spindle, is the energy density and the cooling capability. The heat generated in a spindle is proportional to the losses in the motor.  The losses are depending on the shape of the sinus of the current.   The higher switching frequency, the better the PWM and the lesser harmonics are created in the electrical current, and less heat produced in the center of the spindle.

The availability of the  IGBT's, was the start of a new era of frequency converters allowing to increase the energy density and developing High Speed Turbo technology.  

At the University of Lappeenranta, Finland projects were ongoing since the 90ies for the development of a HST, which later on was commercialised.  The motor technology used was a special induction motor, solid rotor induction motor.  This type of motor has higher losses than a Permanent magnet synchronous motor, and therefor less suitable for higher energy density.

The development continued with Permanent magnet motors, which result in the highest Energy efficiency.

On the evaluation of the bearing technology, comparison of the air-bearings (aerodynamic, aerostatic and foil air-bearings) with magnetic bearings was done.  Although the benefits of the air-bearing, the compactness and the simplicity of it, the magnetic bearing is the only solution which provides the robustness required in the Compressed Air application.

 

Compressed air as a utility in a factory, the consumption is very fluctuating.  The consumption of compressed air  is never constant.  The number of consumers of compressed air (valves, paint-guns,air nozzles,...) is huge leading to a fluctuating demand.  Sudden opening of a valve, generates pressure waves through the piping, which the bearings of the high speed turbo need to withstand.

 

The technology was first applied and used, beginning 20th century, in a single stage blower, for the aeration of Waste Water Treatment plants and has now become today a standard for that application.  A lot of the blower manufacturers their technology is coming out of S-Korea and licensed to various companies, but using Airfoil bearing technology.  The lifetime of the spindles was rather short, due to the lack of robustness of the airfoil-bearings.

Soon after, the Turbo blower with magnetic bearings become the standard and is super reliable.

 

The benefits of the Turbo blower are similar to the High speed turbo air compressor, which are reliability, complete oil-free, vibration free and limited maintenance needs.

 

In 2007, the first commercial High Speed turbo came on the market, but was a 2-stage Turbo Air-compressor.  The first attempt failed, although using the magnetic bearing technology.  The main drawback was the use of induction motor technology and the use of aluminum turbo wheels.  Short lifetime of the spindles and high repair costs, slowed down the commercialisation.

 

In 2011, the first full 3-stage Turbo compressor was launched with magnetic bearings and permanent magnetic motors.  The experience with the technology so far has been wonderful.  

 

The benefits of the High speed technology is that it is a complete Oil-free AirCompressor, no single drop of Oil is in the machine.  The rotors are magnetically levitated and no mechanical contact and wearing is occurring.  The machine is very compact because of the high energy density as well for the compressor stages as well for the drive system.  The high speed Turbo is more energy efficient because no mechanical losses are present as in a traditional centrifugal air compressor.    The HST is speed controlled, allowing smoothly following the fluctuating air demand.

The maintenance is limited to the air-filters.  No oil change, oil filters, waste disposal...

 

Almost like a dream, the perfect technology.

 

And why, after 20 years proven technology, does it take so long for a break-through ?