|
Burner tube constructed of firebrick
Here's a more in-depth description of the stoichiometric combustion WVO burner. Warning: Like all other projects described on this site, I assume no liability whatsoever for you burning your house down or anything else bad that happens from the application or misapplication of the following information.
The ignition system was a propane torch, the one seen on the lower left of the photograph. The burner took a long time to light, and I had to slowly switch from propane to WVO or the flame would extinguish and start to puff out clouds of blue smoke. The propane torch is just a plain bernzomatic soldering torch. I drilled a hole into the side of the firebrick near the breach end to blast the starting flame into. In the photo, this starting port is being mostly blocked by a fragment of firebrick, seen on the left side of the burner.
Please understand that this thing is very much experimental and I am by no means an authority on the subject. I can describe what I encountered along this adventure and you will need to modify it to fit along with your own knowlege and experience.
This is not a furnace; it is just a burner tube made of firebrick. I took two carbide grit holesaws like what are intended for drilling holes in ceramic tile and concrete, and I drilled a 1.5 inch hole through the centers of I think 5 firebrick halves that measured approx 4.5 inch square by 1.25 inch thick. The burner was constructed by stacking the bricks up and clamping together with some threaded rod.
The last firebrick by the exit end was drilled with a 1.25 hole saw, little smaller to force some flame gasses back down the EGR passages which I will describe next:
The EGR passages consisted of 12 holes about .1875 (3/16) inch diameter, drilled around the edge of the holes in each firebrick, precise enough to line up from the near the front of the burner to the back. Then little slots were cut from the holes out into the main burner tube cavity at each end. A little suction is formed at the "breach" end of the burner because of the fuel air mixture blasted in, and a little pressure formed near the "muzzle" end of the burner so that flame gases flow back through the EGR passages to the breach end.
EGR by the way stands for "exhaust gas recirculation" just like in a car engine. The inert exhaust gases help preheat the incoming air, and help reduce NOx emissions.
I learned that a good flame with extremely low NOx emissions and with EGR gases will burn greenish. I don't know if my burner was indeed doing this, but it did burn greenish. It could have been something in the firebrick that was giving in the green color. It was mostly purple and blue, but had greenish tinges to it especially at the flame tip. Deep inside the burner close to the venturi it was all blue colored. I don't know what would have been in the firebrick or anywhere else to generate the green flame color so I like to believe that my burner was burning extremely clean and with very low NOx emissions.
The venturi is like this: I took a 1/8" NPT brass plug and drilled a 1/16" hole down the center, and another hole at right angles to the first hole, drilling into one of the flats (that you would put the wrench onto tighten the plug). I only drilled this until it broke through into the first hole.
Then I took a piece of 1/16" brass tubing like you get in hardware stores in those K&S metal centers (don't know if your familiar with those), hobby stores often carry this fine tubing as well. The hole in the center of this tubing is only about .035 inch. I filed the end of the tubing to a 45 degree angle.
I screwed the brass plug into fittings that attached to my air compressor so that air blows through the hole lengthwise in the plug. The brass tubing with the end filed at an angle inserts into the perpendicular hole so that a little air can escape around the angled tip. This creates a real nice suction in the brass tube to suck up the oil and vaporize it into a very fine mist.
No preheating of the oil or compressed air was needed. After the interior of the burner was up to a red hot glow, the propane torch could be removed from the starting port as long as care was taken to block off air from being drawn into the starting port. A litte experimenting was done with throttling the starting port, and I found that allowing a litte air to come in would make the flame "suck" back into the burner instead of burning somewhat outside the muzzle.
My camera did not do a good job of showing the interior of the burner when it was operating, but with my eyes I was able to observe the operation of the EGR passages. The inside wall of the burner tube had orange, almost bright yellow lines on it right where the EGR passages were, and they extended all the way back to the breach end where the fuel air mixture entered. So I know that some of the flame gases were indeed traveling back and helping to preheat and ignite the fuel air mixture at the breach end of the burner.
I've tried lots of different designs for WVO burners but with very low success. Nothing that I would post on my web page. But this one worked almost like magic and Im just incredulous how much better it worked than other ones I've tried. I think the secret is in the EGR passages and the oil atomizing venturi. Oh--one other thing I was using 60-80 psi on the air, but so litte air was needed that my little compressor only ran about every 3 or 5 minutes.
Please bear with me folks, I may not get photos up here real soon as I'm busy with many projects all the time. I hope to get some diagrams and more photos here eventually, though.
|
|
