Clean Tech Solutions....
....For a World in Need of Energy Sustainability
Established in 1994, Mohawk Innovative Technology, Inc. (MiTi) is the world’s leading authority in developing oil-free, high-speed rotating machinery employing compliant foil air bearing technologies. Using our proprietary know-how, company trade secrets and patented technologies, MiTi has developed a family of CleanTech high efficiency, oil-free rotating machinery products that include renewable energy turbogenerators, oil-free turbocompressors/blowers and electric motors for a wide range of process gas temperatures. Each of these novel prototype products combines high power density and high-speed permanent magnet motor rotor/stator sets; advanced high frequency Variable Frequency Drives (VFD); and MiTi’s patented and world leading oil-free compliant foil air bearings. By integrating these three key technologies, with other state-of-the-art components, compact and reliable machines with electromechanical efficiencies higher than any other machine on the market today are possible. For example, motor/generator/bearing subsystem efficiencies exceeding 95%, and overall compressor efficiencies greater than 75% are achieved. Competing industrial product efficiencies range from 30 to 68%. Besides achieving high efficiency, MiTi’s oil-free systems offer substantial environmental benefits by eliminating hazardous waste oil disposal concerns and the potential for lubricating oil spills. By using renewable energy sources, including process waste heat, our turbogenerator contributes significantly to reducing greenhouse gas emissions. Finally, the MiTi oil-free system designs result in durable machines with low operating and maintenance costs.
ABOUT MITI PRODUCTS
Each MiTi prototype machine uses company patented compliant foil air bearings. Because these selfacting
hydrodynamic bearings (1) operate without any externally pressurized air source; (2) require no
supporting lubrication system; (3) have no known speed limit; and (4) generate a thin film of air for the shaft
to glide on virtually eliminating drag on the rotor, it is possible to take advantage of efficiencies that come
from operating at very high speeds. Additionally, smooth running and very durable machines have been
developed because the MiTi compliant foil air bearing designs have high levels of damping and spatially
variable stiffness. The MiTi oil-free systems are very compact. For example the MiTi 100 HP blower
dimensions are 12”Hx12”Wx19”L, the Motorized Turbocompressor is 6”Hx6”Wx12”L, and the 30 kW
Renewable Energy Turbogenerator is 9”Hx8”Wx15”L. These small subsystem sizes make it possible to
develop very compact system packages for a wide array of different system installations.
Renewable Energy Turbogenerator
The MiTi renewable energy turbogenerator is a very high efficiency turbine powered electric generator system for use with renewable energy sources. Low operating and maintenance costs are due to the integrated assembly of an advanced turbine drive, an efficient high-speed 4-pole permanent magnet generator rotor and MiTi Compliant Foil Air Bearings. Machine reliability and durability are increased because only one moving part is used and it is supported on a film of air. Long product life is achieved because contact between the bearing and/or seals and shaft only occurs briefly during startup and shutdown. Greenhouse gas emissions are reduced since renewable energy sources or industrial and utility waste heat are used to produce electricity. This product can also be used for combined energy and refrigeration systems. Environmental hazards associated with the use and disposal of lubricating oils are eliminated with MiTi’s compliant foil bearings and seals.
Motorized Blower for Industrial Applications
An advanced aerodynamic impeller, an 80 kW /60,000 rpm high-efficiency highspeed
permanent magnet motor, MiTi airfoil bearings and a sensorless VFD
combined with low starting currents reduces operating and maintenance costs.
The single integrated motor, impeller and oil-free bearing system increases life,
reduces maintenance costs and reduces installation footprint. Greenhouse gas
emissions are reduced due to lower energy needs. Environmental hazards and
hazardous waste disposal issues are eliminated with the MiTi oil-free bearings.
Being oil-free, MiTi blowers and compressors can work with many different
process gases from cryogenic to extremely high temperatures, including under two
phase flow conditions among others.
(See also: MiTi Newsletter 26, ASME Paper GT2007-27828)
Motorized Turbocompressor for Automotive Fuel Cells
The advanced aerodynamic impeller, a 12 kW /120,000 rpm high-speed
permanent magnet motor, MiTi Air Foil Bearings, a sensorless VFD and
turbine drive all combine to efficiently deliver contaminant free compressed air
to the fuel cell stacks. The MiTi motorized Turbocompressor also provides
the wide operating speed range and responsiveness needed for automotive
drivability while assuring long life in a compact, lightweight and quiet package.
Since power comes from the fuel cell itself, greenhouse gas emissions are
completely eliminated. Other applications include stationary fuel cells as well
as air cycle machines for cooling and pressurization of aircraft or train cabins.
(See also: MiTi Newsletter 25, ASME Paper GT2006-90796)
Oil-Free High-Speed Motors
A family of 15 to 175 HP high-speed permanent magnet or induction motors
with operational speeds to 120,000 rpm has been developed. Each motor uses
MiTi airfoil bearings, high power density motor elements, and a VFD to
provide motors with efficiencies greater than 95%, wide operating speed range
and precise speed control. Because MiTi oil-free airfoil bearings operate with
the process fluid/gas, no auxiliary lubrication supply system is needed,
eliminating maintenance and hazardous waste disposal issues. Efficiency gains
of 30-35% over medium sized high-speed motors using oil-lubricated bearings
have been demonstrated. As with our other products the single moving part
and MiTi bearings assure long life, low maintenance in a compact package.
Custom designs to meet special needs are available including those requiring
higher power levels and speeds as well as hermetic sealing.
(See also: MiTi Newsletter 21)
Oil-Free Gas Turbine Engine
An oil-free 30-pound thrust class turbojet engine using MiTi Air Foil
Bearings, has been developed and tested. Up to 10% reduction in fuel
consumption was achieved through the use of foil bearings. Because MiTi
oil-free airfoil bearings are used, ball bearing speed restrictions are eliminated,
short bearing life is overcome, and higher operating temperatures are possible.
Elimination of the auxiliary lubrication supply system reduces system weight
and volume. As with our other products the single moving part and MiTi
bearings assure long life, low maintenance in a compact package. Designs may
be customized to meet special needs.
(See also: ASME Papers GT2006-90791, WTC2005-63951, GT-2005-68404)
MiTi has developed the world’s first completely oil-free turbocharger using
compliant foil air bearings. The low powerloss of the lubricant and oil-free
foil bearings overcomes turbolag associated with other bearing designs to
increase engine responsiveness and efficiency. The oil-free design is
environmentally preferred since it prevents contaminating engine oil from
mixing with air entering the piston cylinders. This design helps reduce engine
emissions especially during the cold startup phase. Premature bearing failures
due to high speed and high operating temperatures are eliminated. Oil supply
and scavenge lines are also eliminated resulting in simplified engine installation,
reduced engine oil leak potential and lower parts count.
(See also: MiTi Newsletter 6, ASME Paper WTC2005-63724)
The MiTi oil-free motor driven blower offers efficiency gains over competing technology blowers and
compressors. For example, a 100 HP Roots blower with approximately 50% overall efficiency requires 150 kW
input power, a rotary screw compressor with 65% efficiency requires 115 kW input electrical power and the oilfree
blower with an estimated 75% efficiency will require 100 kW input power. For a three-shift operation and a
cost of $0.116/KWH, the total annual electrical costs for each unit would be $152,056, $116,538 and $101,338
respectively. Given that the MiTi oil-free blowers are expected to have more than a twenty-year life, Roots
blowers are typically limited to less than five years and screw compressors fifteen years, the cumulative effect of
the savings is tremendous. Because the MiTi 100 HP blower substantially reduces parasitic bearing losses, uses
advanced Permanent Magnet motor elements and incorporates VFD technologies, it is possible to achieve very
low operating costs. Besides operating costs, these units will reduce maintenance costs and eliminate
environmental waste disposal costs for system lubricants. An evaluation of maintenance costs savings between a
conventional 100 HP centrifugal compressor compared to a 100 HP screw compressor shows that total four-year
maintenance costs for the centrifugal compressor to be $5,865 versus $23,545 for a screw compressor. The higher
costs of the screw compressor are primarily associated with the cost of overhauling the rotors in the fourth year of
operation, something not needed with the MiTi centrifugal blower. Thus over a four-year period of operation
the MiTi 100 HP oil-free, centrifugal blower could be expected to save up to $60,800 in energy costs at
$0.116/KWH and up to $18,000 in maintenance costs compared to a screw compressor.
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