Jake von Slatt's gasoline and waste oil foundry, tour and test firing of the gasoline injector system.
For the blower assembly I used the design described in Dave Gingery's Building a Gas Fired Crucible Furnace. I used 18 Ga sheet metal from an old Compaq file server PC.
The blower wheel mounts to a belt driven buffer/grinding wheel mandrel. These are available at most hardware stores.
The fan enclosure or volute was cut form the same PC case and MIG welded.
I made a chassis for the fan and motor from some scavenged bed frame angle iron.
Dave Gingery's original blower was designed for propane, but I decided that I was going to build mine for gasoline. My main reason for this was that I wanted to gain some experience with gasoline burners in general for a future steam car project, but also because propane is boring. To atomize the the gasoline I used a BOSCH fuel injector from a BMW, I got these used off eBay for a few bucks each.
The fuel injector was mounted behind a removable panel in the air-stream from the blower.
Here you'll also see a spark plug and a BBQ igniter, this idea totally didn't work.
I used the body of an old table lamp for my fuel tank. Inside the brass urn is a 12 volt fuel injection pump from a Nissan of some sort, the pressure line comes out the top and goes through a filter and the return line is fitted with a valve so I can adjust the fuel pressure.
Since I also need a way to adjust the amount of air I'm feeding into the furnace I needed some sort of throttle on the blower intake. I made this one with some more lamp parts, threaded rod and heavy wire.
At 30 PSI the fuel injector provides good atomization as well as A LOT of gasoline.
My original plan was to adjust the fuel flow by playing with the fuel pressure, however it turned out that at low pressures the fuel injector produces a stream rather than a nice mist and this does not work well at all when the furnace is cold. To address this I built a PWM controller using this circuit. With the PWM controller I can adjust the duty cycle of the injector while leaving the pressure at 30 PSI for good atomization.
It works pretty well.
To fire it up I start with the furnace open and the air flow at near zero. I turn on the fuel and light the burner, once it's burning well I close the furnace and let the interior heat up. After about 5 minutes I can turn the fuel up to full flow and adjust the air for a slight reducing atmosphere in the furnace.
At this rate the fuel tank empties in about twenty minutes, but the plan is to begin feeding waste oil as soon at the furnace is hot so the gallon tank for gasoline is plenty.
5 minutes in the furnace was enough to heat this bit of steel up to where I could pound it flat with a hammer, looks like I can use this for some limited forging too, though the configuration is not ideal.