"Liquid and gaseous fuel injector for a crucible furnace" if you want to get really technical
I'm in the process of designing and building a new crucible furnace for metalcasting. I like the idea of used motor oil as a fuel. Between myself, friends, and family, I do alot of oil changes, and if that's not enough, it's easy to get used oil for free just by asking mechanics. Perhaps building the burner first seems a little backwards. I figured that making a fairly simple burner that uses oil is going to impose some limits on how small you can go. So I will now build a furnace around my "small oil burner". I put small in quotes because a burner made from 1" pipe isn't really all that small when you consider people have made furnaces out of coffee cans.
Let's give credit where credit is due. I based my burner design off of Lionel Oliver's "brute". If you have any interest in knowing some more details about oil burner operation, I suggest reading his fairly large site. In fact I suggest reading his site even if you dont like oil burners because he has a fairly extensive metalcasting site, and links to even more metalcasting sites. There is even some interesting non-metalcasting stuff in there too.
I made it completely out of plumbing fittings. The only 2 items that you may not be able to find in your local home center or plumbing supply house are a 1" steel hex plug, and the 1/8"x18" pipe for the nozzle. Both of these items I got from Grainger (Plug: grainger# 1MNF7 ; Pipe: grainger# 1LLW3). The 1/8" pipe is actually a steel schedule 80 high pressure steam pipe. It has a slightly smaller diameter then a regular 1/8" black steel nipple, but not much. The schedule 80 certainly is not required for this job, however I was not able to find a regular black steel nipple longer then 12". Grainger does sell long unthreaded standard 1/8" pipe sections if you want to weld or cut your own threads with a pipe die.
The only tools I used to make this that you wont find in your typical homeowner's toolbox are a drill press and a 1/8"-27 NPT pipe thread tap. You don't have to have the tap if you want to weld, and you don't need the drill press if you can drill perfect perpendicular holes with a handheld drill. Oh and don't try to use the drill press to drill these holes without a proper drill press vise. I also used a flaring kit on the copper tubing. If you don't have that or don't want to buy that, you could use compression fittings (I HATE compression fittings), or perhaps a flexible hose with hose barb adapters.
TIP: Many pipes and nipples have small burrs on the inside ends of the pipe. I remove these with a round file so they don't interfere with the fluid dynamics.
Here's an overview of the burner. This works exactly like Lionel's burner. The body of the burner is made from a 1"x12" pipe nipple. The propane inlet is on the top and is simply a 1/8" pipe nipple threaded into the 1" pipe. No jet of any kind. I need to add a 90 degree elbow and nipple pointing towards the back, as the propane hose is way too close to the heat as you'll see in later pictures. The oil hooks up to the rear valve via a 3/8" flare fitting. Forced air is fed into the 1" pipe nipple sticking out of the T fitting. Both valves are 1/4" ball valves.
Here you can see a close up of the oil nozzle. Note the blue paint on it. I assume it's like that to denote it as a schedule 80 pipe or a steam pipe. This nipple goes the whole length of the burner and is cut to size from the 18" pipe I spoke of earlier. Also note that I am NOT using any flares or tapers on the burner's tip.
Here you can see the 1" plug. A hole is drilled all the way through it, and is tapped from both sides to act as a pipe coupler. The oil nozzle from the previous picture threads into the end of the plug you can't see.
Here's my oil tank on its (temporary) stand. The 1" pipe is welded to the top to act as a fill tube. I'm not showing you the weld because it is my first successful filet weld with an oxy-acetylene torch, and while functional isn't very pretty. Obviously the cap has to come off when the burner is in operation, just like pouring from a gas can. I like how propane tanks conviently use 3/4" NPT pipe threads for the valve. The plumbing here consists of a 3/4" close nipple, 3/4"-1/2" reducing elbow, a 1/2"x6" nipple, 1/2" ball valve, and 1/2" NPT-3/8" flare fitting. The oil line is 3/8" OD soft copper tubing. I left the base on the tank because it is perfect for holding the fill cap. I will clean up the rust and paint the tank black soon.
Here is an overview of my burner test rig. I'm using a vacuum cleaner as my forced air source until I can cast a nice custom dedicated blower with speed control. The pink freon can furnace in the picture was built about 5-6 years ago, and is useless because the refractory melts. The composition of the refractory on the test furnace is a mixture of perlite and furnace cement from a home center; don't replicate that mix! At least it has been useful as a test vehicle for my burner, because it won't work outside of a furnace. Also note that I am NOT using an oil preheater.
Here's a closeup of the furnace and burner. Note how the inside of the furnace has melted and turned to green glass from a previous firing with a normally aspirated propane burner. The testing of my new burner completely destroyed this furnace, which I expected to happen. In fact the lid fused to the furnace and had to be beat off with a hammer. I can adjust the airflow by moving the fire bricks holding the vacuum hose closer to the burner.
Here I am preheating the furnace with propane only. The oil will not ignite until the furnace is already hot. This only takes a few minutes.
Here the furnace is running on oil only. There was zero soot or smoke coming from the flame, and also zero odors.
Here I cranked up the air and oil flow. What looks like smoke or soot coming from the flame is actually a driveway spot. You can see the propane hose is dangerously close to the heat so I turned off the furnace shortly after taking this picture. A 90 degree elbow and nipple will fix that.
This webpage was first made on June 7, 2008 with a text editor. This webpage uses W3C compliant code and is best viewed with ANY browser or operating system. Well, lynx won't be very useful because there are images where ALT tags would be useless.