Steam & Excursion > Oil firing question

During the 1,500 manhour rebuild of the 3" scale Atlantic that runs in
Traverse City, I made a new twin atomizer (scaled up Chet Petersons
design) and a new oil pan. (The old pan only had a small inlet for air at
the front of the pan) These new atomizers produce a better spray than the
old one.

Question: is there a relationship of the airholes needed in the oil pan to
the flue area or such?
The new pan has a airhole in the front around the burners (20% of the flue
area) and a slot in the back (40% of the flue area) and we can get blue
smoke "popping" out of these air holes w/o having any dark smoke. Is that
because it needs more air?

Also, if the steam to the atomizer is turned up, the "popping" gets worse
and when the steam is turned down, not all the oil is atomized and so it
drips. Turning up the blower really does not help the "popping" unless the
blower is on very little.

We burn diesel fuel in the 3" Atlantic and when the damper on the firebox door is open, there is less "popping" out of the air holes than when the damper is closed.
Also, the "popping" increases when the fuel is increased past the bright yellow flame.
The blue smoke puffs out both the air hole in back and the air hole in front where the burner is.

If the airholes are decreased to create more turbulence, would that help? what about larger air holes?
Any ideas?

Thanks,
Jeff

PS: as a side note, in our three 1.5" scale steamers, we burn coal so the 3" Atlantic is our first expierence with oil and we are still on the learning curve

The first thing you learn about oil fire in scale engines is to go to coal! Every oil burner I've seen is different from another in scale engines. When mine was oil I got a quieter fire and it fired better when I changed the air opening from just a wide open slot 2"X 4" by putting in a piece of sheet metal and started drilling 3/8th holes in it, try it and keep adding holes till it started firing good. Not very scientific I admit, but this made it fire better. However, I finally changed it to coal and been happy ever since then.

Almost forgot to answer question about "poping". You will never get rid of the poping noise an oil burner makes. But you can quiet it down and that is done by baffeling the air intake. The more air the fire gets, the more it will pop.

Well, first, I'd think any air opening "proportion" data produced for oil-fired power by the mechanical engineers back in "steam days" would be moot because almost every one of them would have related to one or more of the "heavy oils" burnt by such power. Of course, your fuel's totally different.

I'm sure you already know this, but it's important that you think of your loco in the sense of a carburetor, you're balancing the "fuel/oil mixture" as you adjust your fire.

I find interesting that the popping decreases when you open the damper because my initial reaction was one of "lean mixture." However, thinking about the two engines I'm familiar with I now believe you may be looking at a situation of over-atomization and the fire's being alternately blown out and re-lit.

We burn #2 diesel fuel at the Henry Doorly Zoo in Omaha, NE where we have two engines of 30" gauge. We have steep ascents and decents which require frequent transitions from exhaust draft to blower draft, also frequent periods of very low fire conditions. We have found it best to leave our dampers open all the time, totally the reverse of standard practice on "real railroads" where rules required the closing of dampers at appropriate times in order to prevent entrance of cold air, which would soon lead to leaking tubes, flues and staybolts on full-sized engines. Our smaller power (THANKFULLY) doesn't suffer this problem, the respective surface areas being 1/5 or less the size of big road engines.

Our engines will begin to "pant" if the atomizer's too high, especially under low-fire conditions. It's effectively blowing the fire out. The minute you add fuel or reduce atomizer they settle down. Same thing with the blower, only different sounds. Reduce blower or add fuel and the condition is alleviated. It's a balancing act. And, it's much more tenuous with diesel fuel than it is with heavy oil (though I've seen 3985's fire go out with resultant "whump" and flames as it's re-lit).

That brings up another thought. In case you haven't already figured this out, whenever the fire goes out FIRST hit the blower. Do that immediately, THEN cut the oil. Leave the blower on a bit in order to clear the firebox of gasses. If the engines well-heated you can re-light the fire by first cracking the atomizer and then opening the oil valve carefully, all while blower remains on. It's easy once you're used to it, but be darned careful until you are, and make sure everyone understands it fully before they run. Diesel fueled locomotives have their fires either blown or sucked out by atomizer or blower (respectively), let alone accidental cutting of oil feed. Once again, if it goes out just hit the blower, then cut the oil and atomozer, wait some few seconds, then crack the atomizer and carefully open oil valve. Get these out of order and you stand a good chance of a VERY nice BANG as it re-lights!!

Sorry to run on so above.

You don't indicate if you've tried running the engine with the damper open, only that it's better with it open. I'd be interested to know about that. If you have "run" it, not just sat and messed with the damper, then I'd suggest that you consider trying to open the pan in a way which allows you to easily close it back up should the experiment prove ineffective. If greater opening doesn't do it then I'm going to suggest that you try a test change in atomizer to a single pipe. I hope this is easily done for you.

I'd appreciate it if you'd keep in touch about this. It's very interesting and I hope you can get past this because it's both annoying and I fear a bit unsafe with the wrong person(s) operating the engine (due to the above).

4-12-2 Wrote:
> I find interesting that the popping decreases when
> you open the damper because my initial reaction
> was one of "lean mixture." However, thinking
> about the two engines I'm familiar with I now
> believe you may be looking at a situation of
> over-atomization and the fire's being alternately
> blown out and re-lit.

I think that over atomizing causes gas and what you hear is the gas explosions or popping since this is a small firebox.

This is true. I know on full size locomotives, if you are really over-atomizing the fuel, it will have a dark orange and green flame and have a very instense shallow drumming sound(due to the gas combusting)

we run with the damper open. There is only a small improvement with running with the damper closed, partly open or all the way open. When the damper is all the way open on the bottom of the pan, and the firebox door is open part way, the drumming and "puffing" of blue smoke (coming out of the airl holes) is less.

Today we tried putting a firebrick on the back sheet of the firebox below the firebox door to act as a flash wall. This did help to stop the puffing of the blue smoke, but the flames were then going into the boiler tubes and it took longer for the boiler to recover pressure and we had to burn the fire with a darker haze to get the heat we needed.
We also tried having a larger space between the blower/blast nozzel and the petti-coat, but that didnt help (it would be hard to say if there was much of a change)

After moving the extra firebrick out of the way, she gained pressure faster, we could burn the fire leaner, the flames were not going into the boiler tubes, but the blue smoke started coming back out of the air holes.

About over atomizing it, that does really kick out the blue smoke and the fire looks "thin" and blown about. There is a little play between having the burner drip and over atomizing it.

frosty,

I simply don't understand this sort of either drip or over-atomize thing. I can't help but feel you have "too much atomizer" on there, in other words too much steam the minute you try to "pass the drip mode." I'd suggest at least trying a larger atomizer steam delivery pipe, as an experiment. You should be able to go from zero to blasting and still have plenty of adjustment in between. We do, and as I said we're running diesel fuel which is of course far more sensitive to "blowing out" than most other oils.

Generally, blue smoke on oil burners means the fire's out or at least very thin (lean). This is absolutely true when such smoke shows at the stack, and I don't care if it's a small engine or 3985. Are you noticing anything suggesting that the fire is fluttering to the extent that it's intermittently out, even for miliseconds?

Another thought: Every oil burner I know has a lining of refractory brick and or cement. It sounds to me as if you have none of this. I'm going to do some reading and see what I come up with. I haven't seen an oil burner without this and am wondering if this could be part of your problem.

John

Hi John,
when i say "over-atomizing" I am talking about having the steam turned on high enough that it kicks the flame out of the firebox door and the air holes.
Once the atomizer steam is turned up past the "drip point" we do have a little bit of play before too much steam is going thru the atomizer.

We are going to try putting a larger air hole in the rear of the firepan to try and get more oxygen into the fire to see if that helps.

Our pan is lined with firebrick. The pan is 1/4" thick with the firebrick 1-1/4"x4-1/2"x9" and all bare metal that is exposed to the flame (of the firepan) is covered. The firebrick 1-1/4" up the side sheets. The sidesheets are about 12" tall and the mudright is made out of 1-1/4" square steel.

Jeff