Combustor Test Results, More on Nozzles & Combustor Sequencer Schematics

December 24, 2001

Here we are in the twelfth month of our turbine builders club. A lot has been accomplished in 2001 -- if you have followed the designs in this column you should have a basic Tesla turbine assembled and operating on compressed air or steam. If not, all of the drawings and tips are on this site to get you up and running.  

Combustor Test Results

We made a couple of minor modifications to our basic vortex combustor; a slotted tube was inserted between the combustion chamber and exhaust tube to help contain combustibles in the main chamber. Once the combustor was up to operating temperature the modification seemed to slightly improve firing reliability, but cold startup was still a problem even using propane.

After choking the inlet to the main air induction blower and setting the fuel valve to full open continuous burn, the unit fired up with no problem. After just a few minutes of burn air inlet was opened to allow lean-burn mixing -- no problems. So the lesson here is that during cold start conditions the fuel-air mix must be on the rich side until the chamber heats up -- then it will function reliably in lean-burn mode.

Convergent-Divergent Nozzles Recently we received an email questioning our explanation of convergent-divergent nozzle practice. Since both inlet and outlet nozzles are extremely important in achieving efficiency with a Tesla turbine, we were already planning to post a scanned page for study. Well, here it is, by the book -- the convergent-divergent nozzle (Figure A).

Figure A Nozzles

Combustor Sequencer

Don Thrasher requested a copy of our combustion sequencer schematic. Referring to the block diagram (Figure B), the basic operation is as follows:

Figure B
Block Diagram

The variable rate main clock controls the combustion sequence and the frequency of the cycle. A rate control potentiometer varies the cycle from about one cycle per second to approximately 100 cycles per second. A cycle begins with the main clock sending a signal to the fuel gate valve driver transistor to open the (normally closed) fuel valve to admit propane gas into the combustion chamber, where the gas and blower-driven air are mixed. As soon as the fuel valve pulse goes low another pulse is sent to the signal logic gate, switching the 1000 hz clock to the spark coil driver. This in turn sends a high frequency spark burst to the plug, making ignition more reliable.

Figures C, D, E & F show wiring diagrams for the power supply, sequencer, and coil drivers.

Figure C Combustor Sequencer  Power Supply	Figure D Combustion Sequencer
Figure E Spark Coil Driver	Figure F Fuel Valve Driver

Member Input

Luis Mendonca sent us pictures of his completed pulse combustion turbine. This is a new design of his, and from the following pictures we can see that it is operational.

Click on picture to view
this photo series

Samuel Falvo also sent us pictures of his air-driven Tesla turbine demonstrator made from cardboard and a soda straw. He says that everyone who sees it run (on lung power) is amazed at the amount of torque it produces for its size and energy input.

Click on picture to view
this photo series

Winding Things Up

This year we've accomplished quite a bit -- we have:

• posted working drawings detailing how to build a high quality Tesla turbine from scrapped engine blocks 
  
• built and tested the turbine with excellent results
  
• explored the basics of combustion

What can we expect in the coming year (2002)? First of all we need to remind ourselves that the purpose for exploring new engine types is to someday move the world away from inefficient, polluting piston engines into motive power solutions that will ease the coming energy crunch, and allow us to once again breathe fresh air.

Besides, problem solving and creating new working machinery is just plain fun. Since combustion efficiency is one of the biggest challenges facing mankind, 2002 will be the year for introducing new technologies to solve the fuel shortage and emissions problems plaguing the world today. It is our goal to be in the forefront of developing and delivering these solutions in the coming year.

Stay tuned for more discoveries in the months ahead.

Ken Rieli, CEO 
PNGinc

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