Olfelt

[barts]

<I'm away from home for this month; so I'm w/o my usual references. This is
pretty much what I remember from the old Audels oil burner handbook, though>

http://www.ncoilheat.org/files/3614/438 ... al2013.pdf

suggests 80 Square Inches per GPH (up to 3.00 GPH), so for a round combustion chamber
240 sq inches means about 17.5" diameter inside the refractory for your boiler.

They also have some recommendations re air supply...

- Bart

[fredrosse]

Burning No. 2 Heating Oil (Dissel Fuel) 3GPH, with 20% excess combustion air, requires 360 PPH (PoundsMass per Hour) combustion air total, or 80 SCFM (Standard Cubic Feet per Minute).

With a 6 inch diameter air inlet (or an equivalent area with several smaller inlets), about 0.05 inches WC (Inches Water Column) pressure drop will be required. For comparison, a 10 foot tall stack at 500F would give about the same draft. Of course if natural stack draft is the only thing driving combustion air and flue gas flow, then flow areas would have to be opened up to allow for pressure drop of flue gas through the boiler hot gas passages.

Note that 3 GPH oil flow is about 420,000 BTU per hour, enough for a Dissel Engine load of about 50 HP. This fire would generate a healthy amount of steam, about 300 PPH, enough for the vicinity of 10 horsepower in a steam engine.

[ron parola]

GRINDING through the site Bard sent me.... probably just to FRY what little little gray cells are left, thanks... I think. Yup around 3gph runs my 3X4X5 worn engine along at flank speed; 6ish MPH according to Steve's cell phone; we've got a cabin AND a canopy; windage IS really an issue. But hull speed isn't supposed to be much higher, have been making SS wrapper for boiler today and tomorrow will be making up a rig to test how much fuel really flows at a constant basis. As with the Stanley, startup REALLY skews fuel MPG, Driving to Colorado we were able to chart mileage WITHOUT cold starts; pretty grim; 3 to 9 MPG depending on terrain, but we were traveling at RIDICULOUSLY high speeds, 45 to 50. So the boat consumption will be less than I've come up with once I see what we use as an average, then I can calculate air intake. Thanks guys rp

[ron parola]

sorry,after review that's 3X5X4 oops rp

[ron parola]

NAKED pix, well the boiler is. It works! Running my American Blower Company 3 1/4 X 3 worn old motor. Only issue is two problems with the sight glass, 1) water VERY unstable, there is a still pipe under the sheetmetal that has a metal deflector around it but I think it's boiling the water still, so will move it outside cover. It does seem to be more stable when pumping water in; when it's boiling you can SEE the water flow in the glass and 2) when engine running water level rises to top of gauge,moving the pipe MAY take care of that also, may also raise the glass a bit. But pretty happy so far, now a bit longer fuel vapourizer Cheers rp

[DetroiTug]

"there is a still pipe under the sheetmetal that has a metal deflector around it but I think it's boiling the water still"

Ron,

My Ofeldt has a 1/4" schedule 80 pipe coming out of the bottom of the drum to the outer casing, below it running the length between is a 1/8" X 1 X 1 angle iron upside down to deflect the heat around it. I don't have any trouble with it boiling water in the glass. But, the sight glass is a little flaky. For instance at start up if there is a half glass, as the heat comes up the water in the glass rises and then as the pressure builds, the water goes back to the bottom of the glass. Which I attribute to the tubes filling with water and lowering the level in the center drum as that is what the sight glass is reading. Other than that, the glass is fairly legible. At a bit of a disadvantage too as the glass is mounted about a foot away on the side of the body, so any angle of lean or rocking effects the sight glass even more.

The running the engine and having the sight glass rise is not something I see. One thing I think that is important is to not impinge fire on the bottom of the center drum. The center drum acts as a downcomer, steam is generated in the tubes - the circulation is water/steam up in the tubes - it has to come back down. If the center drum is making steam also, the water doesn't know which way to go. If a Stanley/baker type burner is being used, I'd put a heat deflector on the bottom of the center drum. Demand showing a rise in the drum displays a lack of internal circulation.

Looking at the Ofeldt burner ( or my rendition of it), there is no fire in the center under the drum.

If you'd like the drawings I made of this burner, let me know. It's inexpensive to build and it works great, burns straight kerosene perfectly and it's much quieter than Stanley/Baker types. No howling.

-Ron

[ron parola]

I've been following your trials and tribulations also; good job. I'm using a Lune Valley type burner so there is a "hole " in the centre of the fire, maybe a shield is in order. But I've moved the sight glass standpipe to the outside of the sheet metal and the reading is a lot more stable, BUT original bottom fitting was at the TOP of the lower "drum", I've moved the fitting pointing to the outside and it picks up the water from the bottom of the lower support, that in itself may have done it. Yeah the water rises a LOT when running my test engine but when boiler pressure reaches 160ish psi the motor becomes more efficient, throttle down and level drops so maybe in the boat there will be no issue. Will be swapping it out after the meet in Sept. Cheers rp

[DetroiTug]

Taking to one of my steam friends about this last night and he suggested to make sure the steam line to the engine is totally isolated (two different outlets at the boiler) from the steam line to the top of the glass. If they are both on the same circuit, that would cause a pressure drop at the top of the glass and cause the water to rise on engine acceleration.

-Ron

[barts]

My Lune Valley boiler has completely separate connections for the water glass and engine and I see a lot of rise when the engine starts. I think this is because the tubes terminate below the water line. When the throttle is opened and the pressure drops, the hottest water in the tubes flashed into steam, and that flows into the boiler, reducing the density and lifting the water level.

This seems to be born out by the effect being minimized when opening the throttle after the fire has been off for a bit.

So, I would expect to see this effect on any boiler with submerged tubes.

- Bart

[Oilking]

While standing checks, as in check valve, on an old stick shift can, you learned that the water in the glass jumped with increases in steam demand. You had to have the guts to give the wheel a quarter to a half turn open even though the water level went up or before you new it you'd be chasing it out the bottom of the glass. Two thing are happening that cause the rise, first the drop in pressure created by the initial steam demand causes the steam bubbles to expand pushing water out of the tubes, second the increased firing rate makes more steam bubbles to meet the demand for more steam. The water will rise initially then drop to normal level and a new equilibrium if the feed check is opened enough to match the steam demand. I don't think that VFT's are quite as susceptible due to the larger water volume and heating surfaces don't confine the water as in a water tube boiler.

Steaming tomorrow on the Portland's monthly outing. Going to be over 100 degrees, but were steaming!

Dave