NT-PU37 37Kw Power Unit

The NT-PU37 is an experimental free turbine power unit (turbo expander) designed to extract usable power from an existing pressurized hot or cold gas source.  The unit is self-contained and skid mounted with integral cooling and lubrication systems.  The NT-PU37 is designed to be grid-tied and requires a separate gas generator to drive the turbine. 

Objectives:

• To build a reliable, stand alone, free turbine power unit that can recover thermodynamic energy from any suitable turbine gas producer like the J07-NT-XX TurboJet and convert it to electrical power.
  
• To provide a test bed for future gas generator (TurboJet) development.

This is it! The PU37 is the result of years of carefull study and consideration of how to effectively drive a generator with an automotive turbocharger. We have considered high speed direct drive systems like the TA30-NT-XX. We designed the NT-RT30 in an attempt to avoid the difficulties with high speed machinery, and we have even tried a belt drive system as used on T98-NT-XX just to see how long a belt might last at super high speeds.

Our current thinking is "KISS" The PU37 uses a diesel power unit turbine that has a helical pinion rather than a compressor wheel. We use this pinion do drive a large bull gear directly mounted on the generator shaft. The machinery is far from simple, but we have done our best to keep everything as basic as we can.

The PU37 is a demand displacement machine that is designed to be grid-tied. This eliminates difficulties in speed and frequency regulation as the generator will be locked in phase with the power gird. Future versions could be off-grid capable with the addition of suitable speed controller equipment.

The lubrication and cooling system are self contained, the oil pump runs directly off the main shaft.

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General Specifications (subject to change)
The NT-PU37 37 kW micro turbine power unit consists of:

• Radial power turbine
• Parallel shaft single stage speed reducer
• Induction generator
• Lubrication and cooling system
• Welded steel skid frame

Power Turbine:

• Single stage radial turbine
• Max inlet temperature  700°C
• Max speed 90,000 RPM
• Design speed 72,000 RPM

Speed Reducer:

• Welded steel gearbox
• NEMA flange mounted
• Direct mounted driven helical gear
• Single stage 20:1 reduction

Generator:

• Squirrel cage induction generator
• 575V 3 Phase  60 Hz  3,600 RPM
• High efficiency TEFC  50 HP

Lubrication System:

• 6 Liter dry sump
• Direct drive gear pump 75 psi
• Oil cooler and filter

Estimated performance curve

Download the .pdf Specsheet here

 

Note: The NT-PU37 is experimental research apparatus and may not be suited to any particular use or purpose. There is no warranty or promise of performance of any kind expressed or implied. Specifications are approximate and subject to change.   20110920

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The following photos show how we developed PU37

 
This is how we built the gearbox without the need for sand casting.

 
We welded the plates with 3/32 Flux Core, super strong and stiff.

  
This is how the parts looked after annealing and blanchard grinding.

 
We milled the pilot bores, dowel and bolt holes plus ribs on our Mitsubishi M-V60.

Milling NT-PU37 gearbox.

  
Checking the cutter for the custom bull gear. Note the trick compression coupling.

  
We static balanced the bull gear for 3,600 RPM operation.

  
Thanks to careful measuring and precision machining, the parts fit perfectly!

   
This is the turbine power unit, notice the helical pinion gear.

This video shows PU37 being tested for the first time with compressed air.

 

The next task was to finish the lubrication system. We have acquired a Siemens VFD speed controller that we will use to drive the generator to run the gears in and check for vibration.

We proved the oil flow prior to running the gears at high speed..

 

   
   
This is the finished NT-PU37. We still have the Lexan window on the gearbox.

This video shows the PU37 being run up to speed with the VFD.

The NT-PU37 free turbine power unit is now complete and ready for coupling to a gas generator and application testing. We are prepared to continue ourselves (as time permits) or sell the apparatus to interested research organizations looking for a free turbine generator for use in their own projects.

Contact mark@nye.ca for more information.