I seem to have a lot of people interested in this little gadget, also a lot of nay Sayers on its need for a compressed air source instead of the "Hot Pan" method that's more commonly seen. I have no doubt the hot pan method works, but my intentions were to make A LOT of heat without the smoke and smell that normally accompanies waste oil burning.
My prime goal of this project was to heat water to supplement the heating and hot water needs in my home, an additional bonus is the extremely high temps it can attain that I can use it for melting aluminum to make some castings.
Now onto the meat of the project.
The basic theory of how its setup is simple. pressurize the oil, add a little heat, add a little more air to help atomize it and light it on fire... Sounds easy enough? It is once you get the proportions right.
The tank I am using for testing was an older propane tank that was beyond its certification age. Its still in excellent shape and can easily handle the top pressures of up to 40 psi I was testing with. Because I needed 2 separate adjustable air pressures There are 2 air regulators on the tank. As there is only one hole in a propane tank I had to piggyback all of the hardware on the 3/4" inlet/outlet. I inserted a 3/4" X 4" nipple in and put a 3/4" Tee on top, one port for filling and outlet, and one for air in.
The air supply is Teed off to both regulators, one feeds pressure to the tank
to get positive and consistent oil flow, the other to add extra atomizing air at
the nozzle. The worst part about using a propane tank is the one fitting it had.
it makes it a pain to fill, you have to remove the oil out feed tube, but its
the best I had at the time. The 1/4" copper tube coming out of the top is the
oil out. I drilled the brass compression fitting all the way through with a
1/4" drill to make it a pass through fitting. then fed the copper to about
1" off the bottom of the tank then secured it with the compression sleeve
Air is fed to the top of the oil to help push it through the
line when its cold. The warmer the oil is the less pressure you will need
to push it through.
The oil coming through the line is then fed through a air filter housing with a sintered bronze filter, its good protection for the down stream valve. Next in line is a needle valve, this gives a good precise flow control.
I have been messing around with different pressures and at this point I am down to 20psi on the oil and about 3 psi on the air. but depending on how think your oil is you may need higher pressures to move it through.
The Nozzle is over simplistic, but it works, it consists of a 1/8" pipe Tee (have since changed this with a compression Tee) with 1/4" and 3/16" compression fittings for the tubing. The 3/16" compression fitting for the oil feed is drilled so the tubing can pass all the way through into the Tee, then its cut off at an angle to give the airflow more shear surface to help atomize the oil. The oil leaves the needle valve through a 3/16" steel brake line and meets up with the air line at a Tee on the top of the stove. The air and oil then come out of a short length of 3/16" brake line with the end flattened down with just a small narrow opening left.
The nozzle tube is the trickiest part to make right the first time. After trying a few different configurations this was the best setup I ended up with, The tubing was just squeezed down in a vice till it was nearly closed off then I pinched the outer edges a bit to narrow the resulting slot. This gives you a fairly decent flame pattern almost like a paint spray gun with reasonable atomization.
The tank holds about 4-5 Imp Gal's and so far with about 12-14 hrs of testing I still have about 20-30% left in the tank, its a bit of a pain to fill because you have to remove some of the top plumbing but this is only a test setup. Later on I will get a bigger pressure tank with more openings so I can have separate fill and feed ports.
During one of the test burns I dug up a K type thermocouple and stuck it into one of the vent ports in the stove door out of direct flame. The spec sheet for this thermal says its max range tops out at 54 mili-volts at 2450°F and I pulled it out of the stove after it hit 68 mili-volts (oops!), so I am guessing the temps are hitting somewhere in the 2600°F range so I am confident that melting aluminum is doable..