Burner Question

[Jack Innes]

I am currently working on the burner in my Blackstaff type boiler. The burner has 2 nozzles fed kerosene by compressed air at 18psi. The assembly mounts on the boiler support legs & is offset to the Port side by 1/2". Could there be any reason to offset the burner? The copper coils on the close side cleaned up much better than the other side which may indicate they ran hotter & burned the carbon off???

Secondly, would it be practical to try feeding the kerosene with an electric fuel pump to eliminate the cumbersome air system?

Thank you,
Jack

[fredrosse]

To burn Oil or Kerosene the fuel must be atomized (or vaporized) before ignition or smoke/soot will result. Air or steam atomization works well, but compressed air comes at a premium for extra machinery, and steam atomization consumes a fraction of boiler output, and consumes feedwater that cannot be recovered. Atomizing steam also suppresses the flame temperature somewhat.

Vaporizing burners can work well, where the fire vaporizes the fuel, then generally a jet of fuel vapor into the throat of a Venturi induces enough primary air before ignition to avoid smoke/soot. Vaporizing burners are often temperamental, as too much vaporizing heat will crack the hydrocarbon fuel, and carbon deposits will clog the vaporizer tubing. Too little heat here results in liquid fuel issuing from the jet, with poor combustion resulting.

Almost all manufactured small oil burners are now "pressure atomized" with a motor driven pump, and require about 100 - 150 psi (7-10 Bar) pressure for proper function, as well as plenty of turbulence with the combustion air surrounding the atomization nozzle. Air atomization inherently accomplishes this requirement, but with pressure atomization of oil only, getting enough air into intimate mixing with the atomized fuel is difficult and requires the addition of a high turbulence fan. If you can copy the basic design of conventional oil burners things can work well.

However that will usually start to use significant electric power for the fan and oil pump. Not significant if you plug into your house AC circuit, but often significant for a small steamer that has to rely on battery power. Small residential oil burners are now offered with 12 VDC power, for the hot pressure washer applications, this would provide a pre-engineered burner that functions well. Trying to get this right with your own design may take much iteration. For me that would be what I call "fun", but for many the work required here would be better spent on earning the money to just buy the ready made burner.

[smokestackmag]

I had one of those 12V DC burners made by Beckett, still have it in fact. But I took it out of my boat for exactly the reason stated by Fred Rosse. Too much of a hassle to keep the batteries charged. My solution was to change to solid fuel which I have thoroughly enjoyed ever since. I first burned wood and now I am trying coal (being careful to stay away from people who keep really clean boats). There's a fellow in Georgia who swears by this same oil burner. He was in that business for many years and that is what he understands. He also cannot physically lug wood or coal. He set up a permanent magnet alternator to keep his batteries charged and that seems to work quite well for him. If you want more info contact me with your email address and I will tell him. He's quite forthcoming. And my Beckett burner is available.

[boatbum]

Please pm me I'm interested in the burner.

Keith