Prototyping a spinning cup oil burner

Belt drive... interesting idea. Motor mounted on the outside of the pipe, belt looped inside the pipe to a gear on the ass end of the shaft with the cup mounted on the other end. I like it.

 

Where were you during the first couple of pages of this thread Jason...?...lol.

As far as the masses copying Mark's efforts.... Well all good ideas get copied. That's how I built nearly all of my diy stuff. Standing proudly on the shoulders of others. The view is really nice up here and I get the benefit of hindsight being front and center

 

Gentlemen....the challenge has been met and exceeded: It cold starts on Canola oil with an oil soaked rag to light it. Fuel flow is really slow: I estimated from the bubbles in the plastic line that it flowed about 1 inch per second.......I'll have to cut that 1/8" nozzle hole off the end of the copper tube if I'm going to get any faster rate of burn. I ran the furnace for an hour with about 3.5 litres (0.92 US Gallons) of Canola consumed to melt about 3Kg of aluminium in forty minutes or so. I'd better start editing the footage and get another vid up the Youtubes .

 

Very nice...!! Congrats

Now you're cooking...lol

I think you should consider force feeding your fuel, whether it be via pressurized tank or pump of some sort. I prefer the pump approach has having "stored energy" leads to potential hazards, and you still stay away from the whole compressor thing.

 

I recently converted from gravity flow with 8 feet of elevation (quickly became a nuisance) to a 12v automotive fuel pump powered by a 12 dollar 12v power supply. There are two pressure levels commonly available in these pumps. I passed on the 5 to 8 pound style and am quite happy with the 2-4 pound unit. Simply makes life easier. For something like 30dollars there are fully pressure adjustable units available. The 12volts also drives my very quiet leaf blower for combustion air.

 

The power supply is set into a an ammo box that I bought at Harbor Freight and uses SO cord with plugs and receptacles of a type that can’t be confused with household current. The excess room in the box serves to hold small tools and furnace related accessories. Glad I did it.

 

I use a 12vdc "bilge pump" which is a tiny centrifugal pump. I guess I could adjust it's output easy enough via voltage but rather just run full out and throttle the burner with the traditional needle valve. Honestly, the 12vdc is an annoyance for me that I didn't give much thought when I bought the pump. All the power supplies I have kicking around are 24vdc so there's some minor rework I need to perform to get the power I need.

Instead I retooled an oil coolant pump from an extruder with a beefy DC motor. Far more work than the fore mentioned power supply alteration but now I have waay more head room on fuel rate.


I think the spinning cup approach would be the one build that could handle an extreme amount of fuel rate. ...especially Mark's current design wherein the fuel is injected toward the back of the cup. A back fed cup with just a terminated pipe at the cup would end up producing a jet of fuel that wouldn't touch the cup ID at high rates of fuel. ....I think

 

Here are a couple of pics of my power supply and fuel pump. For those unfamiliar with the power supplies they are available in a wide range of voltages and are extremely simple plug and play devices with pretty decent amperage outputs. I chose 12V as it is such a common voltage for accessories and will power my fuel/air mixture gauge as well. You can see there is the grey household current input and three individually switched 12V outputs one of which is as yet uncorded. I used a piece of 1/4" cast clear plexiglass for the floor of the toolbox portion just so I could see that nothing is amiss in power supply portion of the box.

The nice thing about putting it all in the ammo box is that it is waterproof (I live in the Pacific NW where rain is a normal event) and pretty rugged which seems appropriate for the expected use. The box was about 15 bucks.

 

That ammo box pump power supply is a work of art!, I have an old cast iron gear displacement pump from a six cylinder engine along with a 240V induction motor and belt drive but it's cumbersome. I do like that plastic extruder coolant pump with integral motor. Lifting twenty litres of oil 2+ metres high is going to get old pretty fast, it'll have to do for the experimentation phase until I get some idea of what I need.

As J Vibert has pointed out, even a raised tank of oil is a form of stored energy and would be a potential leak/fire hazard in a permanent installation.

Chirpy's Tinkerings pointed out, over on Youtube that I might get coking in the hot copper tube from the furnace heat after shutdown.

 

I have zero doubt of this. I experience some coking at the dip of my plain drip tube and it doesn't near the exposure to the furnace heat that yours does.

I believe nozzle guys make a habit of immediately pulling the burner after shut down to prevent o-ring damage. This may just be a procedure you have to follow as well. Really isn't a bad practice regardless of what burner type you run. It's on my list of shut down tasks. Just not the top priority.

No disrespect to the pressurized tank guys, but pumping fuel is where it's at if you're not already using a compressor to run a nozzle.

 

I could already be experiencing coking, I have to pull the tube to cut the 1/8" tip off anyway, so I'll report back on it's state.


Edit: I pulled apart the copper fuel tube and cut off the 1/8" tip : it was black inside and out with dried, burnt oil. Possibly a second vent tap at the top of the siphon to allow the fuel tube to purge to air. I think the Mk3 version with hollow cup drive shaft should alleviate the problem.

 

No coking here... I leave the burner in the furnace, but leave the blower running for good half hour before putting the show away. Coking occurs when unburnt fuel drys on the face of a nozzle. Case in point. The airplane I fly has direct drive engines so when the prop spins, so does the turbine. After shutting down, I wait a minute or two and then pull the props through about 10 rotations... Then repeat a few minutes later. All that air rushing through helps blow dry the fuel off the fuel nozzles. This prevents coking and helps cool the turbine. I time change the 24 fuel nozzles every 400hrs. They always come out super clean because of this practice.
Here's some interesting reading regarding this little known issue.

 

I ran the furnace today with the 1/2" fuel line from the oil drum through the valve and up to the spinning cup unit which is 1/4" for the last three feet or so. The 1/8" nozzle hole was cut off and is just the 1/4" tube now. The furnace runs a lot better but after it warms up it begins to surge when the fuel flow is high and the air flow is higher (air valve is still less than 1/3rd open). The oil is getting to the nozzle if the flow is anything to go by, but I suspect the copper U turn into the cup is getting hot and causing the fuel to boil in the tube. The furnace was pretty hot but not super duper yellow-orange bright like I see on my friend's liquid petroleum gas fired furnace. I was able to get the bottom of those three bricks on the top of the furnace to glow orange...the first time I've seen that so far and the crucible was glowing orange as opposed to a dull red on all other test runs.

It runs, reliably but the oscillating surge at higher settings is a bit annoying: it might be time for a MK3 hollow drive shaft unit to eliminate the copper U in the flames. After the run, there is a yellow ash deposit all over the inside of the furnace lining and also the crucible which is an orange pottery colour now: it's supposed to be clay graphite with 30% silicon carbide but doesn't look like it any more, I may have to cut a pouring spout in the rim with a silicon carbide abrasive stick and see just how much graphite and silicon carbide is actually under the surface.

 

Seems I read somewhere, crucibles are not to be fired empty or even with small amounts of metal. Small melts, small crucible. Melting 2lbs of alloy in a 20 will shorten its life.

You have a point about that U-turn at the front... How is that copper pipe holding up? I was thinking 2weeks ago, some SS pipe might be a better choice. But, oil will still boil inside that too. Rear entry into that cup if you can figure it out might be the ticket! Keep trying, we are all rooting for you!

 

The 'U'-turn on the feed pipe has always been the design flaw, imho. Not trying to be dick-ish there, just saying what I thought the moment I saw it. That said, I didn't give any consideration to the oil boiling within it. Just the likely hood of it disintegrating at high temps. I figured it's use was more so just a quick and dirty method to test the functionality of the spinning cup so I didn't harp on it. Excited to see a hollow drive shaft version.

On that note: I've given some pondering to the hollow shaft design, and I think there needs to be a diffuser of some sort to force the oil into the ID of the cup. I would think at high fuel rates the oil may just 'jet' out of the tube and not even make contact to the cup.

 

The oil jetting out without being spun seems l Ike a reasonable concern. To prevent this, placing a disc with notches around its periphery maybe 1/3 of the way into the cone depression would prevent direct jetting. As fuel tried to jet straight out it would strike the disc and be slung radially to hit the cone and thus be atomized as desired. The disc could be a simple “coin” with, say, 1/16” notches machined or even flied into its edge. Then just tack it with a tig In 3 or 4 places and you are set.

 

Yep... was thinking along the same lines. I'm not much a mechanical engineer but there may be some concern about unbalancing the cup with welds though...? Not sure about the whole light mass .vs. rpm thing....

 

If you fusion welded the cup using no filler then, at least in theory and probably practice, there is no addition of metal in any spot so balance should be practically not changed. I am thinking tiny tig tacks maybe 1/16 to 3/32” diameter. Alternatively a shallow slightly undersize groove could be cut into the cone and the disc pressed into place. If the cone and disc are of the same composition, heating and cooling should not cause loss of the pressed-in disc purchase.