Wulf-Dieter Oil Burner

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Wulf-Dieter wrote:

Completed some 40 years ago and still working! You're right, petroleum will burn a bit better than diesel fuel does. Standard light oil for use with heatings for homes will do, too. Published back in January 1991 in "dampfmodel" you'll find a drawing. First built into my Model of DB class 44 fuel, 5 inch gauge this worked out fine. No dripping, smokeless and adjustable from 15% to full.


Wulf-Dieter answers questions posed by James Keith, June 12, 2012. Wulf's answers are in italics.

I found a number of your contributions to Chaski.org and took joy in watching your videos and seeing tracks filled with 5 inch gauge steam. In this country (United States), 7-1/2 inch gauge dominates and, unfortunately, 4-3/4 inch gauge has nearly disappeared.

As for oiler burner Live Steam locos ... they are popular on the west coast but not so much here in the eastern half of the U.S. It was the same with full-size steam in the 1900s. The west coast had oil wells -- and little to no coal.

Thus oil was the common fueld in that part of the country.

Similar story here in Europe. In countries like France or Germany oil burners became popular after WW II, but not at all in England.

I was fascinated by your atomizer design ... and have some question. I hope you don't mind.

a) I see that you have a convergent-divergent steam nozzle and, from your comments, I get the idea that you operate your atomizers at (or near) full boiler pressure. Thus, you have supersonic steam velocity at the oil/steam mixing plane. Am I correct so far?

You're right! Thus steam consumption is well below 1 pound per once pound of oil.

Does the existing high velocity jet provide for a stable flame? I would have guessed that it would have tended to blow the flame out?

No problem as long as there is a red hot plate under the fire door to reverse the flame. And a long fire bridge (arch) of course, made of high temperature stainless steel to avoid sucking the flames into the tubes by excessive draft.

Can you give me an idea of what your typical steam supply pressure at the atomizer might be.

The working pressure of the 44 boiler is up to 130 psi. The burner normally works well below this but may be worked to about 120 psi at full capacity. Two steam valves of just 1 mm are sufficient!

The burner constructed for use with locos in 1.6 inch scale will deliver its full capacity at a slightly reduced 100 psi. Thus diameter of its steam nozzle is 0.6 to 0.7 mm versus a fueld exit of 1.8 mm for best atomizing.

b) If I read the drawing correctly, your steam nozzle throat diameter=0.4 mm and the exit diamete=0.6 mm?

Steam nozzle of 0.4 mm (0.5 mm for 100 psi or less) is right. To elevate manufacturing and tests, the steam nozzle can be exchanged very easily. This never was necessary, yet!

Fuel exit (mixing nozzle) showed best results at 1.6 mm (not 0.6!). No dripping from the nozzle at all!

Bigger diameter will allow atomizing fueld of higher viscosity than diesel bu result in a lower vacuum in the fueld delivery pipe.

c) How do you generally regulate the fire during a run? With the steam supply valve? Or by adjusting the oil supply? Or both?

Both! Normally blower (first!), atomizer steam and fueld are adjusted from the cab.

Once you find a stable adjust, the output may be adjusted from about 30 to 70 percent output just by means of the atomizer handle. When you are starting from a long station stop it is recommended to turn on the fuel slightly more.

Do you adjust the oil supply by rotating the nozzle outer-body from the cab, or is that adjusted once and then you go with it?

The rotating nozzle body is adjusted from the cab (as it was in real life). The advantage of throttling fueld directly at the nozzle to stablize the flame in case of accasionally water bubbles in the fuel. The main fueld valve at the tender outlet is just for safe cutoff.

d) You mention a "blue" flame. Is the blue flame hot enough for normal operation?

No, less than ideal. But this works fine to clean up the tubes at the end of working time.

e) Do you use superheated steam to supply the atomizer?

Yes, I do! It's a separate superheater element which delivers steam of up to 650 degrees F. But it's not mandatory, just better atomizing. At full load I can add saturated steam to increase power.

f) I notice an interesting flare on the outside of the atomizer at the exit plane. I presume its purpose is to introduce turbulence and ehance mixing. Di you experiement with various sizes of flares to determine their effectiveness? (I couldn't quite make out the German name for this flare (?) in the drawing, sorry)

There are two items: To avoid dripping from the nozzle, there is a sharp edge at the end of the rotating nozzle. In case of any dripping for spilling when starting the burner at low steam pressure there is a shovel like pan below. The idea is to suck any overflow by the draft into the fire. Very important when steaming during exhibitions inside buildings!

g) AND (I suppose the kiler qwuestion) ... would you look kindly on my including info about your design on the web page?

Yes, I will do in short!

You must have been just a youngster in 1977; you have been, indeed, a pioneer. And that's a very nice looking engine you have.

Thank you for your recognition! Yes, I was of age 30 then when starting my project of a German DB class 44 oil burner. That was exactly the very last year those engines were use on revenue service for ore drags! Still competitive then to the (hydraulic) diesels (not to electric locomotives of course) - unbelievable to U.S. in a world of total dieselization, isn't it? At this time I'm constructing a N&W class A with working HT - stoker.