Update on PTBC Tesla Turbine Project

October 22, 2001

October is a very mystical time of the year. Projects that creep along during other months suddenly seem to pull together in October almost by a power of their own. That's the way it has been for our in-house turbine project. We have a pretty good line up of designs, experiments and updates from a couple of club members so hang on... here we go.

First of all I want to share a couple of photos of our efforts here in Michigan. The first photo shows our Sachs case with all the shaft components assembled and torqued down. The hot rotor flange is on the right, the output pulley on the left. Just below the bearing case are the disks, star washers and hot rotor case end plates -- as we received them from our laser cutter.

The time and effort saved by having a local shop laser cut these parts was well worth the relatively low cost. For our first stage prototyping we are working with a low-cost 836 steel; for final prototypes we'll specify either 316 or 416 stainless for all of these parts.

The next photo shows most of the parts assembled and ready for the hot rotor case ring and end plate.

Test Results

After final assembly of the hot rotor section we modified the outlet of our pulse combustor and attached it to the turbine nozzle. Although the combustor cycled properly, the rotor did not self start. The nozzle being a 1" x 1" square tube did not generate enough directed energetic gas between the plates. Most of the gas energy went around the disks and exited the hot rotor case without transferring power to the disk pack. After grinding a nozzle insert and fitting it into the nozzle tube, the resultant slot impeded the pulse combustion cycle (using low pressure air).

Conclusions

Tesla turbines do not operate under conventional turbine principles. Bladed turbines require large volumes of relatively low velocity fluid, whereas Tesla turbines require lower volumes of accurately-directed high velocity fluid.

Tesla turbines work extremely well with steam, air, or hot gas fed to a slotted nozzle at around 80-160 psi. They do not work well with typical simple pulse combustor techniques.

In order to get pulse combustion to work properly with a Tesla turbine, air and fuel must be delivered to the chamber at pressures suitable to deliver approximately 80-160 psi of hot gas to the working rotor nozzle.

Future Developments

In the coming months we plan to experiment with steam and improved combustion systems for powering up the hot rotor section.

Other Club Member Development Updates

Don Thrasher sent us this photo of his star washer improvements. (For more information on his generator project, see our September 10 article.)

Also, Luis Mendonca sent a number of photos showing some of his work with Tesla turbines. The photos show some of his early work with steam or compressed air driving a turbine; other photos show his more recent work with pulse combustion techniques.