Vaporizing oil spray experiment.

The amount of fuel your burning, almost 7 US gallons in 90 minutes seems inordinately high. That's over 4.5 gallons per hour. And if that's only half of your previous consumption then.... Wow. I'm assuming those are pressure nozzles on your burner, not Venturi types, so that explains the high fuel pressure values and no mention of compressed air. ( I looked for a build thread in your profile and couldn't find one, sorry if I can't remember the details of your design). Like you I am trying to get a good burn rate dialed in and am using Melterskelter's 2.8 gal/hr as a goal for fuel consumption which is evidently doing the job for him. That's about what I've been consuming right along and although I've always had enough heat output, it's the distribution within the furnace that I'm trying to tune. My recent crucible failure and subsequent repairs have put that exercise pretty much on hold over the last couple weeks but the disk on top of the plinth is showing promise. But as I'm following this thread, in my mind I keep going back to your high bore turbulance and high fuel consumption and have to wonder if your burner is the source of both.
Edit: Denis posts much faster than I do! Lol.

Pete

 

It ran with pretty good performance before, but was hard to tune like an Italian sportscar and leaked like a British motorbike, performance when running well, was 15Kgs of iron from cold to poured in 62 minutes with 22 litres of fuel burnt. Without going into specifics the fuel has 30% less energy than diesel so a comparable diesel figure would be 14.6 litres of fuel. I've managed to sort out the leak but tuning is another matter and the melt was hamstrung by a mass of oxides and iron in the crucible from the previous run that had to be melted first before more iron could be added. I hope with a bit more fiddling around with the tuning/configuration I can get hot combustion like before.

There is a fairly long build thread here https://forums.thehomefoundry.org/index.php?threads/yet-another-keg-furnace.401/page-8 that details a fairly conventional 1.5 beer keg furnace build. The fuel system is a 55 PSI pressure regulator pump feeding eight brass garden mist nozzles, each nozzle gives 3 litres per hour flow and nozzles can be removed and the hole plugged with a screw. Small nozzles give finer droplets than large ones so the ungainly assembly gives a much finer spray and allows flow rate in 3 litre increments of 3-24 litres per hour with a needle valve for fine flow tuning. The whole thing was working quite well once I had the burner disc fitted. https://forums.thehomefoundry.org/index.php?threads/oil-furnace-swirl-experiments.855/page-2

Yesterday's run shows the crucible slightly darker than the flames with a segment of brake rotor in the bottom right of the hole.


Earlier unsuccessful iron run with no refractory disc.



Earlier run with the best tuning to date and the experimental disc.

 

It only occurred to me later today that there's too much swirl happening: the plinth flame disc and the refractory nozzle is spinning up a flame vortex strong enough to whip up the crucible slag tornado. The easy experiment is to remove the refractory disc and let the refractory nozzle coupled to the relatively high pressure blower generate the flow. Also the crucible will be 2" lower then improving exhaust flow. Refractory disc + refractory lined tuyere = too much swirl = hot slag rain ...or in the words of Brian Ferry: "A hard rain's gonna fall".

 

I’ve been reading the threads on burner designs and it made me wonder about a burner based on the old time gasoline blowtorch principle. They had a cup under the burner that you put a little fuel in and lit off to preheat the burner so the fuel was vaporized. The YouTube videos show a nice clean blue flame with only a pressurized fuel tank to get fuel to the burner.

So the thought occurs that a heated nozzle to vaporize waste oil before actually burning it might make a very good burner.

 

Now that you mention it, there's significant heat on the brass nozzle assembly, that must be aiding vaporization of the fuel. So there has to be some vapourizing going on, if it wasn't for the fuel and airflow cooling it and some heatsinking from the 1/2" copper fuel pipe. I used to have one of those old hand pumped soldering irons, complete with dents on the body after the leather seals leak and the whole thing catches on fire and gets flung off the ladder while trying to solder galvanized gutters . Here's what it looks like after the shrink fit and soft solder (230 deg C) join failed and the front shot off into the furnace to be slagged, never to be seen again. I had a photo on this forum showing distinctly oxidized brass from the heat, I'll see if I can link it here.



Versus what it looked like originally:




These two photos show the appearance without any cleaning at all after two or three successful iron melting sessions and show the partial singeing of the brass nozzles from the heat.

 

I found that burners that use any metal surface that doesn't get red hot starts to accumulate carbon buildup and gue. Cleaning needs to be done. So far at a dozen or so practice burns and melts I have not cleaned my burner tip at all. One of them looks like it's getting some buildup on the outside but nothing on the drip tube. The other one looks pretty clean. If you look closely you can see where the baked on drips are accumulating.

 

That's true, you can't leave them in place or they can get too hot and residual fuel inside dribbles out, but any inside the nozzle would be converted to carbon buildup. I kept forgetting to withdraw the nozzles immediately on shutdown and paid the price after about ten times. I'm going to add a sign on the fuel shutoff valve.

Here's the new "one piece body" brass nozzle, while stainless is possible the mist nozzles are still brass and at least brass conducts heat a bit better into the air and fuel flows.

 

Mark, that tip looks beautiful. I would like to see how it looks after a one hour burn. My burners has not been cleaned or touched with about 10 hours of burn.

Edit; at the end of each burn I clean the lines with diesel fuel to clear out any of the vegetable oil in the lines. Then I put her away wet with a quick wipe up of paper towel.

 

Posting No.45, third photo has the original after four melts and forgetting to withdraw a few times, photo two is after 8 melts with carbon buildup, post furnace run as the residual pressure makes it dribble a fair bit.

 

Thank you. With my full documentation I have 7 to 8 hours of burn time on those tips. No cleaning.

 

I found I can give it a quick scrub on the nozzle faces with a small fine brass wire brush and run some 0.4mm twist drills by hand into the nozzle orifices to give it a quick clean.

 

I'm gonna keep pushing mine till they need a full cleaning. I'll even put a YouTube video up here. hopefully I get another 7 to 10 hours of burn.

 

Shit, I haven't cleaned my kwiky since I built it years ago! If my jet engine fuel nozzles didn't have a 2grand core charge EACH, I'd try one! I don't sleep well when I have to ship 20 of them back to the overhaul shop! Every 400hrs, they get swapped out. Best 2400bucks you'll ever spend! INSTANT fuel savings that I can actually SEE!

 

Jeez Jason, I can fix you up with nozzles made from hardware store parts if you want . I'm testing the new assembly right now, it's flowing 16 litres per hour or 4 US gallons per hour with a nice fine mist that should vapourize and burn faster. I had to hand make some copper washers, anneal them and sand them flat to get a decent high temperature seal in place of the rubber O ring. Spray pattern is parallel forward but that's on water, once you run some diesel or kero through it the lower surface tension gives a cone pattern instead.

 

That thing sprays NICE!

 

It's looking the part, even gives a nice fine spray at lower pressures, fine droplets should burn faster too. I took a leaf out of one of the nozzle manufacturer's books that said smaller nozzle orifices give smaller droplet size so having multiple small nozzles will give a fine spray at the required volume compared to one big one. If this thing works as intended (the last one did), I'll make a spare in case of an emergency failure so I don't lose a crucible.

 

Nice looking nozzle. To get a fine mist does it have to be run at full pressure? What I am thinking is how do you adjust the flow rate should you decide that, perhaps, your optimal fuel flow is 2.8 gallons per hour? Does taking out or plugging a few of the nozzles work as a means of flow adjustment?

You’ve d one yeoman’s duty getting system operational.

Denis

 

Hi Denis, it was giving a decent spray even after the tap was shut off so I think it should be fine in that respect, there's also a range of nozzle orifice sizes and then the option of removing a nozzle and putting a 3/16" screw in to plug it.

 

Your vaporizing spray looks amazing! If you can keep the new tip cool enough it looks promising...

My tip is literally half inch away from the inside walls of my furnace. I think I might be getting some backed on goo from the old chicken wings, Fish and chips (& smell), from the waist vegetable oil. I do preheat now my waste vegetable oil to 65°C. I kind a learned the hard way.

 

Apart from a bit of soot from the fuel dribble after shutdown, it seems to have done the job. However it used 18 litres over 80 minutes while I tried to get throttle setting right and only melted iron on the top of the crucible. This is without the refractory disc but with the refractory nozzle glowing orange as seen towards the end of the video. The brass nozzle is slightly darker in colour but otherwise unharmed after a wipe with a rag, all the black came off (sump oil). Fuel consumption was 18 litres over 80 minutes to barely melt some iron, versus 22 litres to melt 15 kilograms of iron in 62 odd minutes with the earlier 0.4mm orifice fuel nozzle and refractory disc fitted. Furnace interior is bright orange-yellow in colour and would be perfect for bronze or aluminium but just not enough oomph for iron. Will have to make a new refractory disc and try it too as the old one broke earlier. I loaded the crucible back into the furnace for a slow cool down but still with a slug of iron inside it, again I heard a loud "tink" sound that may be the crucible cracking.

Edit: The only liquid in the crucible was molten iron slag: lightweight, breaks like glass and weakly magnetic.